along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
#include <cmath>
#include <cstring>
-#include <fstream>
+#include <iomanip>
#include <iostream>
#include <sstream>
+#include <vector>
+#include <algorithm>
#include "book.h"
#include "evaluate.h"
#include "misc.h"
#include "movegen.h"
#include "movepick.h"
-#include "lock.h"
-#include "san.h"
#include "search.h"
+#include "timeman.h"
#include "thread.h"
#include "tt.h"
#include "ucioption.h"
+namespace Search {
+
+ volatile SignalsType Signals;
+ LimitsType Limits;
+ std::vector<Move> RootMoves;
+ Position RootPosition;
+}
+
using std::cout;
using std::endl;
-
-////
-//// Local definitions
-////
+using std::string;
+using namespace Search;
namespace {
- /// Types
- enum NodeType { NonPV, PV };
-
- // Set to true to force running with one thread.
- // Used for debugging SMP code.
+ // Set to true to force running with one thread. Used for debugging
const bool FakeSplit = false;
- // ThreadsManager class is used to handle all the threads related stuff in search,
- // init, starting, parking and, the most important, launching a slave thread at a
- // split point are what this class does. All the access to shared thread data is
- // done through this class, so that we avoid using global variables instead.
-
- class ThreadsManager {
- /* As long as the single ThreadsManager object is defined as a global we don't
- need to explicitly initialize to zero its data members because variables with
- static storage duration are automatically set to zero before enter main()
- */
- public:
- void init_threads();
- void exit_threads();
-
- int active_threads() const { return ActiveThreads; }
- void set_active_threads(int newActiveThreads) { ActiveThreads = newActiveThreads; }
- void incrementNodeCounter(int threadID) { threads[threadID].nodes++; }
- void incrementBetaCounter(Color us, Depth d, int threadID) { threads[threadID].betaCutOffs[us] += unsigned(d); }
-
- void resetNodeCounters();
- void resetBetaCounters();
- int64_t nodes_searched() const;
- void get_beta_counters(Color us, int64_t& our, int64_t& their) const;
- bool available_thread_exists(int master) const;
- bool thread_is_available(int slave, int master) const;
- bool thread_should_stop(int threadID) const;
- void wake_sleeping_threads();
- void put_threads_to_sleep();
- void idle_loop(int threadID, SplitPoint* sp);
-
- template <bool Fake>
- void split(const Position& pos, SearchStack* ss, Value* alpha, const Value beta, Value* bestValue,
- Depth depth, bool mateThreat, int* moveCount, MovePicker* mp, int master, bool pvNode);
-
- private:
- friend void poll();
-
- int ActiveThreads;
- volatile bool AllThreadsShouldExit, AllThreadsShouldSleep;
- Thread threads[MAX_THREADS];
- SplitPoint SplitPointStack[MAX_THREADS][ACTIVE_SPLIT_POINTS_MAX];
-
- Lock MPLock, WaitLock;
-
-#if !defined(_MSC_VER)
- pthread_cond_t WaitCond;
-#else
- HANDLE SitIdleEvent[MAX_THREADS];
-#endif
-
- };
-
-
- // RootMove struct is used for moves at the root at the tree. For each
- // root move, we store a score, a node count, and a PV (really a refutation
- // in the case of moves which fail low).
+ // Different node types, used as template parameter
+ enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
+ // RootMove struct is used for moves at the root of the tree. For each root
+ // move, we store a score, a node count, and a PV (really a refutation
+ // in the case of moves which fail low). Score is normally set at
+ // -VALUE_INFINITE for all non-pv moves.
struct RootMove {
- RootMove() { nodes = cumulativeNodes = ourBeta = theirBeta = 0ULL; }
-
// RootMove::operator<() is the comparison function used when
// sorting the moves. A move m1 is considered to be better
- // than a move m2 if it has a higher score, or if the moves
- // have equal score but m1 has the higher beta cut-off count.
- bool operator<(const RootMove& m) const {
+ // than a move m2 if it has an higher score
+ bool operator<(const RootMove& m) const { return score < m.score; }
- return score != m.score ? score < m.score : theirBeta <= m.theirBeta;
- }
+ void extract_pv_from_tt(Position& pos);
+ void insert_pv_in_tt(Position& pos);
- Move move;
+ int64_t nodes;
Value score;
- int64_t nodes, cumulativeNodes, ourBeta, theirBeta;
- Move pv[PLY_MAX_PLUS_2];
+ Value prevScore;
+ std::vector<Move> pv;
};
+ // RootMoveList struct is mainly a std::vector of RootMove objects
+ struct RootMoveList : public std::vector<RootMove> {
- // The RootMoveList class is essentially an array of RootMove objects, with
- // a handful of methods for accessing the data in the individual moves.
-
- class RootMoveList {
-
- public:
- RootMoveList(Position& pos, Move searchMoves[]);
+ void init(Position& pos, Move rootMoves[]);
+ RootMove* find(const Move& m, int startIndex = 0);
- int move_count() const { return count; }
- Move get_move(int moveNum) const { return moves[moveNum].move; }
- Value get_move_score(int moveNum) const { return moves[moveNum].score; }
- void set_move_score(int moveNum, Value score) { moves[moveNum].score = score; }
- Move get_move_pv(int moveNum, int i) const { return moves[moveNum].pv[i]; }
- int64_t get_move_cumulative_nodes(int moveNum) const { return moves[moveNum].cumulativeNodes; }
-
- void set_move_nodes(int moveNum, int64_t nodes);
- void set_beta_counters(int moveNum, int64_t our, int64_t their);
- void set_move_pv(int moveNum, const Move pv[]);
- void sort();
- void sort_multipv(int n);
-
- private:
- static const int MaxRootMoves = 500;
- RootMove moves[MaxRootMoves];
- int count;
+ int bestMoveChanges;
};
- /// Adjustments
+ /// Constants
- // Step 6. Razoring
+ // Lookup table to check if a Piece is a slider and its access function
+ const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
+ inline bool piece_is_slider(Piece p) { return Slidings[p]; }
// Maximum depth for razoring
- const Depth RazorDepth = 4 * OnePly;
+ const Depth RazorDepth = 4 * ONE_PLY;
// Dynamic razoring margin based on depth
inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
- // Step 8. Null move search with verification search
-
- // Null move margin. A null move search will not be done if the static
- // evaluation of the position is more than NullMoveMargin below beta.
- const Value NullMoveMargin = Value(0x200);
-
// Maximum depth for use of dynamic threat detection when null move fails low
- const Depth ThreatDepth = 5 * OnePly;
-
- // Step 9. Internal iterative deepening
+ const Depth ThreatDepth = 5 * ONE_PLY;
// Minimum depth for use of internal iterative deepening
- const Depth IIDDepth[2] = { 8 * OnePly /* non-PV */, 5 * OnePly /* PV */};
+ const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY };
// At Non-PV nodes we do an internal iterative deepening search
// when the static evaluation is bigger then beta - IIDMargin.
const Value IIDMargin = Value(0x100);
- // Step 11. Decide the new search depth
-
- // Extensions. Configurable UCI options
- // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
- Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
- Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
-
// Minimum depth for use of singular extension
- const Depth SingularExtensionDepth[2] = { 8 * OnePly /* non-PV */, 6 * OnePly /* PV */};
-
- // If the TT move is at least SingularExtensionMargin better then the
- // remaining ones we will extend it.
- const Value SingularExtensionMargin = Value(0x20);
-
- // Step 12. Futility pruning
+ const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY };
// Futility margin for quiescence search
const Value FutilityMarginQS = Value(0x80);
- // Futility lookup tables (initialized at startup) and their getter functions
- int32_t FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
- int FutilityMoveCountArray[32]; // [depth]
+ // Futility lookup tables (initialized at startup) and their access functions
+ Value FutilityMargins[16][64]; // [depth][moveNumber]
+ int FutilityMoveCounts[32]; // [depth]
+
+ inline Value futility_margin(Depth d, int mn) {
- inline Value futility_margin(Depth d, int mn) { return Value(d < 7 * OnePly ? FutilityMarginsMatrix[Max(d, 0)][Min(mn, 63)] : 2 * VALUE_INFINITE); }
- inline int futility_move_count(Depth d) { return d < 16 * OnePly ? FutilityMoveCountArray[d] : 512; }
+ return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)]
+ : 2 * VALUE_INFINITE;
+ }
- // Step 14. Reduced search
+ inline int futility_move_count(Depth d) {
- // Reduction lookup tables (initialized at startup) and their getter functions
- int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
+ return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES;
+ }
- template <NodeType PV>
- inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
+ // Reduction lookup tables (initialized at startup) and their access function
+ int8_t Reductions[2][64][64]; // [pv][depth][moveNumber]
- // Common adjustments
+ template <bool PvNode> inline Depth reduction(Depth d, int mn) {
- // Search depth at iteration 1
- const Depth InitialDepth = OnePly;
+ return (Depth) Reductions[PvNode][std::min(int(d) / ONE_PLY, 63)][std::min(mn, 63)];
+ }
// Easy move margin. An easy move candidate must be at least this much
// better than the second best move.
- const Value EasyMoveMargin = Value(0x200);
-
- // Last seconds noise filtering (LSN)
- const bool UseLSNFiltering = true;
- const int LSNTime = 4000; // In milliseconds
- const Value LSNValue = value_from_centipawns(200);
- bool loseOnTime = false;
-
-
- /// Global variables
+ const Value EasyMoveMargin = Value(0x150);
- // Iteration counter
- int Iteration;
- // Scores and number of times the best move changed for each iteration
- Value ValueByIteration[PLY_MAX_PLUS_2];
- int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
+ /// Namespace variables
- // Search window management
- int AspirationDelta;
+ // Root move list
+ RootMoveList Rml;
// MultiPV mode
- int MultiPV;
+ size_t MultiPV, UCIMultiPV, MultiPVIdx;
- // Time managment variables
- int SearchStartTime, MaxNodes, MaxDepth, MaxSearchTime;
- int AbsoluteMaxSearchTime, ExtraSearchTime, ExactMaxTime;
- bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit;
- bool FirstRootMove, AbortSearch, Quit, AspirationFailLow;
+ // Time management variables
+ TimeManager TimeMgr;
- // Log file
- bool UseLogFile;
- std::ofstream LogFile;
-
- // Multi-threads related variables
- Depth MinimumSplitDepth;
- int MaxThreadsPerSplitPoint;
- ThreadsManager TM;
-
- // Node counters, used only by thread[0] but try to keep in different cache
- // lines (64 bytes each) from the heavy multi-thread read accessed variables.
- int NodesSincePoll;
- int NodesBetweenPolls = 30000;
+ // Skill level adjustment
+ int SkillLevel;
+ bool SkillLevelEnabled;
// History table
History H;
- /// Local functions
-
- Value id_loop(const Position& pos, Move searchMoves[]);
- Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr);
- template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, bool allowNullmove, int threadID);
+ /// Local functions
- template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID);
+ Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove);
- template <NodeType PvNode>
- void sp_search(SplitPoint* sp, int threadID);
+ template <NodeType NT>
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- template <NodeType PvNode>
- Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
+ template <NodeType NT>
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- void update_pv(SearchStack* ss, int ply);
- void sp_update_pv(SearchStack* pss, SearchStack* ss, int ply);
+ bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
bool connected_moves(const Position& pos, Move m1, Move m2);
- bool value_is_mate(Value value);
- bool move_is_killer(Move m, SearchStack* ss);
- bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
+ Value value_to_tt(Value v, int ply);
+ Value value_from_tt(Value v, int ply);
+ bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply);
bool connected_threat(const Position& pos, Move m, Move threat);
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
- void update_killers(Move m, SearchStack* ss);
- void update_gains(const Position& pos, Move move, Value before, Value after);
-
- int current_search_time();
- int nps();
- void poll();
- void ponderhit();
- void wait_for_stop_or_ponderhit();
- void init_ss_array(SearchStack* ss);
- void print_pv_info(const Position& pos, SearchStack* ss, Value alpha, Value beta, Value value);
-
-#if !defined(_MSC_VER)
- void *init_thread(void *threadID);
-#else
- DWORD WINAPI init_thread(LPVOID threadID);
-#endif
+ void do_skill_level(Move* best, Move* ponder);
+
+ int elapsed_time(bool reset = false);
+ string score_to_uci(Value v, Value alpha = -VALUE_INFINITE, Value beta = VALUE_INFINITE);
+ string speed_to_uci(int64_t nodes);
+ string pv_to_uci(const Move pv[], int pvNum, bool chess960);
+ string pretty_pv(Position& pos, int depth, Value score, int time, Move pv[]);
+ string depth_to_uci(Depth depth);
+
+ // MovePickerExt template class extends MovePicker and allows to choose at compile
+ // time the proper moves source according to the type of node. In the default case
+ // we simply create and use a standard MovePicker object.
+ template<bool SpNode> struct MovePickerExt : public MovePicker {
+
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b) {}
+ };
-}
+ // In case of a SpNode we use split point's shared MovePicker object as moves source
+ template<> struct MovePickerExt<true> : public MovePicker {
+
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
+
+ Move get_next_move() { return mp->get_next_move(); }
+ MovePicker* mp;
+ };
+
+ // Overload operator<<() to make it easier to print moves in a coordinate
+ // notation compatible with UCI protocol.
+ std::ostream& operator<<(std::ostream& os, Move m) {
+
+ bool chess960 = (os.iword(0) != 0); // See set960()
+ return os << move_to_uci(m, chess960);
+ }
+
+ // When formatting a move for std::cout we must know if we are in Chess960
+ // or not. To keep using the handy operator<<() on the move the trick is to
+ // embed this flag in the stream itself. Function-like named enum set960 is
+ // used as a custom manipulator and the stream internal general-purpose array,
+ // accessed through ios_base::iword(), is used to pass the flag to the move's
+ // operator<<() that will read it to properly format castling moves.
+ enum set960 {};
+
+ std::ostream& operator<< (std::ostream& os, const set960& f) {
+
+ os.iword(0) = int(f);
+ return os;
+ }
+
+ // is_dangerous() checks whether a move belongs to some classes of known
+ // 'dangerous' moves so that we avoid to prune it.
+ FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) {
+ // Test for a pawn pushed to 7th or a passed pawn move
+ if (type_of(pos.piece_on(move_from(m))) == PAWN)
+ {
+ Color c = pos.side_to_move();
+ if ( relative_rank(c, move_to(m)) == RANK_7
+ || pos.pawn_is_passed(c, move_to(m)))
+ return true;
+ }
-////
-//// Functions
-////
+ // Test for a capture that triggers a pawn endgame
+ if ( captureOrPromotion
+ && type_of(pos.piece_on(move_to(m))) != PAWN
+ && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
+ - PieceValueMidgame[pos.piece_on(move_to(m))] == VALUE_ZERO)
+ && !is_special(m))
+ return true;
-/// init_threads(), exit_threads() and nodes_searched() are helpers to
-/// give accessibility to some TM methods from outside of current file.
+ return false;
+ }
-void init_threads() { TM.init_threads(); }
-void exit_threads() { TM.exit_threads(); }
-int64_t nodes_searched() { return TM.nodes_searched(); }
+} // namespace
-/// init_search() is called during startup. It initializes various lookup tables
+/// init_search() is called during startup to initialize various lookup tables
-void init_search() {
+void Search::init() {
- int d; // depth (OnePly == 2)
- int hd; // half depth (OnePly == 1)
+ int d; // depth (ONE_PLY == 2)
+ int hd; // half depth (ONE_PLY == 1)
int mc; // moveCount
// Init reductions array
for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
{
double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
- double nonPVRed = log(double(hd)) * log(double(mc)) / 1.5;
- ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(OnePly)) : 0);
- ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(OnePly)) : 0);
+ double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
+ Reductions[1][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
+ Reductions[0][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
}
// Init futility margins array
- for (d = 0; d < 16; d++) for (mc = 0; mc < 64; mc++)
- FutilityMarginsMatrix[d][mc] = 112 * int(log(double(d * d) / 2) / log(2.0) + 1) - 8 * mc + 45;
+ for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
+ FutilityMargins[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
// Init futility move count array
for (d = 0; d < 32; d++)
- FutilityMoveCountArray[d] = 3 + (1 << (3 * d / 8));
+ FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(d, 2.0));
}
-// SearchStack::init() initializes a search stack. Used at the beginning of a
-// new search from the root.
-void SearchStack::init(int ply) {
+/// perft() is our utility to verify move generation. All the leaf nodes up to
+/// the given depth are generated and counted and the sum returned.
- pv[ply] = pv[ply + 1] = MOVE_NONE;
- currentMove = threatMove = MOVE_NONE;
- reduction = Depth(0);
- eval = VALUE_NONE;
-}
+int64_t Search::perft(Position& pos, Depth depth) {
-void SearchStack::initKillers() {
+ StateInfo st;
+ int64_t sum = 0;
- mateKiller = MOVE_NONE;
- for (int i = 0; i < KILLER_MAX; i++)
- killers[i] = MOVE_NONE;
+ // Generate all legal moves
+ MoveList<MV_LEGAL> ml(pos);
+
+ // If we are at the last ply we don't need to do and undo
+ // the moves, just to count them.
+ if (depth <= ONE_PLY)
+ return ml.size();
+
+ // Loop through all legal moves
+ CheckInfo ci(pos);
+ for ( ; !ml.end(); ++ml)
+ {
+ pos.do_move(ml.move(), st, ci, pos.move_gives_check(ml.move(), ci));
+ sum += perft(pos, depth - ONE_PLY);
+ pos.undo_move(ml.move());
+ }
+ return sum;
}
-/// perft() is our utility to verify move generation is bug free. All the legal
-/// moves up to given depth are generated and counted and the sum returned.
+/// think() is the external interface to Stockfish's search, and is called by the
+/// main thread when the program receives the UCI 'go' command. It searches from
+/// RootPosition and at the end prints the "bestmove" to output.
-int perft(Position& pos, Depth depth)
-{
- StateInfo st;
- Move move;
- int sum = 0;
- MovePicker mp(pos, MOVE_NONE, depth, H);
+void Search::think() {
- // If we are at the last ply we don't need to do and undo
- // the moves, just to count them.
- if (depth <= OnePly) // Replace with '<' to test also qsearch
- {
- while (mp.get_next_move()) sum++;
- return sum;
- }
+ static Book book; // Defined static to initialize the PRNG only once
- // Loop through all legal moves
- CheckInfo ci(pos);
- while ((move = mp.get_next_move()) != MOVE_NONE)
- {
- pos.do_move(move, st, ci, pos.move_is_check(move, ci));
- sum += perft(pos, depth - OnePly);
- pos.undo_move(move);
- }
- return sum;
-}
+ Position& pos = RootPosition;
+
+ // Reset elapsed search time
+ elapsed_time(true);
+ // Set output stream mode: normal or chess960. Castling notation is different
+ cout << set960(pos.is_chess960());
-/// think() is the external interface to Stockfish's search, and is called when
-/// the program receives the UCI 'go' command. It initializes various
-/// search-related global variables, and calls root_search(). It returns false
-/// when a quit command is received during the search.
-
-bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
- int time[], int increment[], int movesToGo, int maxDepth,
- int maxNodes, int maxTime, Move searchMoves[]) {
-
- // Initialize global search variables
- StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false;
- MaxSearchTime = AbsoluteMaxSearchTime = ExtraSearchTime = 0;
- NodesSincePoll = 0;
- TM.resetNodeCounters();
- SearchStartTime = get_system_time();
- ExactMaxTime = maxTime;
- MaxDepth = maxDepth;
- MaxNodes = maxNodes;
- InfiniteSearch = infinite;
- PonderSearch = ponder;
- UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
-
- // Look for a book move, only during games, not tests
- if (UseTimeManagement && get_option_value_bool("OwnBook"))
+ // Look for a book move
+ if (Options["OwnBook"].value<bool>())
{
- if (get_option_value_string("Book File") != OpeningBook.file_name())
- OpeningBook.open(get_option_value_string("Book File"));
+ if (Options["Book File"].value<string>() != book.name())
+ book.open(Options["Book File"].value<string>());
- Move bookMove = OpeningBook.get_move(pos, get_option_value_bool("Best Book Move"));
+ Move bookMove = book.probe(pos, Options["Best Book Move"].value<bool>());
if (bookMove != MOVE_NONE)
{
- if (PonderSearch)
- wait_for_stop_or_ponderhit();
+ if (!Signals.stop && (Limits.ponder || Limits.infinite))
+ Threads.wait_for_stop_or_ponderhit();
cout << "bestmove " << bookMove << endl;
- return true;
+ return;
}
}
- // Reset loseOnTime flag at the beginning of a new game
- if (button_was_pressed("New Game"))
- loseOnTime = false;
+ // Read UCI options: GUI could change UCI parameters during the game
+ read_evaluation_uci_options(pos.side_to_move());
+ Threads.read_uci_options();
- // Read UCI option values
- TT.set_size(get_option_value_int("Hash"));
- if (button_was_pressed("Clear Hash"))
- TT.clear();
+ // Set a new TT size if changed
+ TT.set_size(Options["Hash"].value<int>());
- CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
- CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)"));
- SingleEvasionExtension[1] = Depth(get_option_value_int("Single Evasion Extension (PV nodes)"));
- SingleEvasionExtension[0] = Depth(get_option_value_int("Single Evasion Extension (non-PV nodes)"));
- PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
- PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
- PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
- PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
- PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
- PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
- MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
- MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
-
- MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
- MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point");
- MultiPV = get_option_value_int("MultiPV");
- Chess960 = get_option_value_bool("UCI_Chess960");
- UseLogFile = get_option_value_bool("Use Search Log");
-
- if (UseLogFile)
- LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
-
- read_weights(pos.side_to_move());
-
- // Set the number of active threads
- int newActiveThreads = get_option_value_int("Threads");
- if (newActiveThreads != TM.active_threads())
+ if (Options["Clear Hash"].value<bool>())
{
- TM.set_active_threads(newActiveThreads);
- init_eval(TM.active_threads());
+ Options["Clear Hash"].set_value("false");
+ TT.clear();
}
- // Wake up sleeping threads
- TM.wake_sleeping_threads();
-
- // Set thinking time
- int myTime = time[side_to_move];
- int myIncrement = increment[side_to_move];
- if (UseTimeManagement)
- {
- if (!movesToGo) // Sudden death time control
- {
- if (myIncrement)
- {
- MaxSearchTime = myTime / 30 + myIncrement;
- AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
- }
- else // Blitz game without increment
- {
- MaxSearchTime = myTime / 30;
- AbsoluteMaxSearchTime = myTime / 8;
- }
- }
- else // (x moves) / (y minutes)
- {
- if (movesToGo == 1)
- {
- MaxSearchTime = myTime / 2;
- AbsoluteMaxSearchTime = (myTime > 3000)? (myTime - 500) : ((myTime * 3) / 4);
- }
- else
- {
- MaxSearchTime = myTime / Min(movesToGo, 20);
- AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3);
- }
- }
+ UCIMultiPV = Options["MultiPV"].value<size_t>();
+ SkillLevel = Options["Skill Level"].value<size_t>();
- if (get_option_value_bool("Ponder"))
- {
- MaxSearchTime += MaxSearchTime / 4;
- MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
- }
- }
+ // Do we have to play with skill handicap? In this case enable MultiPV that
+ // we will use behind the scenes to retrieve a set of possible moves.
+ SkillLevelEnabled = (SkillLevel < 20);
+ MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV);
- // Set best NodesBetweenPolls interval to avoid lagging under
- // heavy time pressure.
- if (MaxNodes)
- NodesBetweenPolls = Min(MaxNodes, 30000);
- else if (myTime && myTime < 1000)
- NodesBetweenPolls = 1000;
- else if (myTime && myTime < 5000)
- NodesBetweenPolls = 5000;
- else
- NodesBetweenPolls = 30000;
-
- // Write search information to log file
- if (UseLogFile)
- LogFile << "Searching: " << pos.to_fen() << endl
- << "infinite: " << infinite
- << " ponder: " << ponder
- << " time: " << myTime
- << " increment: " << myIncrement
- << " moves to go: " << movesToGo << endl;
-
- // LSN filtering. Used only for developing purposes, disabled by default
- if ( UseLSNFiltering
- && loseOnTime)
+ // Write current search header to log file
+ if (Options["Use Search Log"].value<bool>())
{
- // Step 2. If after last move we decided to lose on time, do it now!
- while (SearchStartTime + myTime + 1000 > get_system_time())
- /* wait here */;
+ Log log(Options["Search Log Filename"].value<string>());
+ log << "\nSearching: " << pos.to_fen()
+ << "\ninfinite: " << Limits.infinite
+ << " ponder: " << Limits.ponder
+ << " time: " << Limits.time
+ << " increment: " << Limits.increment
+ << " moves to go: " << Limits.movesToGo
+ << endl;
}
- // We're ready to start thinking. Call the iterative deepening loop function
- Value v = id_loop(pos, searchMoves);
-
- if (UseLSNFiltering)
+ // Wake up needed threads and reset maxPly counter
+ for (int i = 0; i < Threads.size(); i++)
{
- // Step 1. If this is sudden death game and our position is hopeless,
- // decide to lose on time.
- if ( !loseOnTime // If we already lost on time, go to step 3.
- && myTime < LSNTime
- && myIncrement == 0
- && movesToGo == 0
- && v < -LSNValue)
- {
- loseOnTime = true;
- }
- else if (loseOnTime)
- {
- // Step 3. Now after stepping over the time limit, reset flag for next match.
- loseOnTime = false;
- }
+ Threads[i].maxPly = 0;
+ Threads[i].wake_up();
}
- if (UseLogFile)
- LogFile.close();
-
- TM.put_threads_to_sleep();
-
- return !Quit;
-}
-
-
-namespace {
-
- // id_loop() is the main iterative deepening loop. It calls root_search
- // repeatedly with increasing depth until the allocated thinking time has
- // been consumed, the user stops the search, or the maximum search depth is
- // reached.
-
- Value id_loop(const Position& pos, Move searchMoves[]) {
-
- Position p(pos);
- SearchStack ss[PLY_MAX_PLUS_2];
- Move EasyMove = MOVE_NONE;
- Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
+ // Set best timer interval to avoid lagging under time pressure. Timer is
+ // used to check for remaining available thinking time.
+ TimeMgr.init(Limits, pos.startpos_ply_counter());
- // Moves to search are verified, copied, scored and sorted
- RootMoveList rml(p, searchMoves);
-
- // Handle special case of searching on a mate/stale position
- if (rml.move_count() == 0)
- {
- if (PonderSearch)
- wait_for_stop_or_ponderhit();
-
- return pos.is_check() ? -VALUE_MATE : VALUE_DRAW;
- }
+ if (TimeMgr.available_time())
+ Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 8, 20)));
+ else
+ Threads.set_timer(100);
- // Print RootMoveList startup scoring to the standard output,
- // so to output information also for iteration 1.
- cout << "info depth " << 1
- << "\ninfo depth " << 1
- << " score " << value_to_string(rml.get_move_score(0))
- << " time " << current_search_time()
- << " nodes " << TM.nodes_searched()
- << " nps " << nps()
- << " pv " << rml.get_move(0) << "\n";
-
- // Initialize
- TT.new_search();
- H.clear();
- init_ss_array(ss);
- ValueByIteration[1] = rml.get_move_score(0);
- p.reset_ply();
- Iteration = 1;
-
- // Is one move significantly better than others after initial scoring ?
- if ( rml.move_count() == 1
- || rml.get_move_score(0) > rml.get_move_score(1) + EasyMoveMargin)
- EasyMove = rml.get_move(0);
-
- // Iterative deepening loop
- while (Iteration < PLY_MAX)
- {
- // Initialize iteration
- Iteration++;
- BestMoveChangesByIteration[Iteration] = 0;
+ // We're ready to start thinking. Call the iterative deepening loop function
+ Move ponderMove = MOVE_NONE;
+ Move bestMove = id_loop(pos, &RootMoves[0], &ponderMove);
- cout << "info depth " << Iteration << endl;
+ // Stop timer, no need to check for available time any more
+ Threads.set_timer(0);
- // Calculate dynamic aspiration window based on previous iterations
- if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
- {
- int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
- int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
+ // This makes all the slave threads to go to sleep, if not already sleeping
+ Threads.set_size(1);
- AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
- AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
+ // Write current search final statistics to log file
+ if (Options["Use Search Log"].value<bool>())
+ {
+ int e = elapsed_time();
- alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
- beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
- }
+ Log log(Options["Search Log Filename"].value<string>());
+ log << "Nodes: " << pos.nodes_searched()
+ << "\nNodes/second: " << (e > 0 ? pos.nodes_searched() * 1000 / e : 0)
+ << "\nBest move: " << move_to_san(pos, bestMove);
- // Search to the current depth, rml is updated and sorted, alpha and beta could change
- value = root_search(p, ss, rml, &alpha, &beta);
+ StateInfo st;
+ pos.do_move(bestMove, st);
+ log << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
+ pos.undo_move(bestMove); // Return from think() with unchanged position
+ }
- // Write PV to transposition table, in case the relevant entries have
- // been overwritten during the search.
- TT.insert_pv(p, ss->pv);
+ // When we reach max depth we arrive here even without a StopRequest, but if
+ // we are pondering or in infinite search, we shouldn't print the best move
+ // before we are told to do so.
+ if (!Signals.stop && (Limits.ponder || Limits.infinite))
+ Threads.wait_for_stop_or_ponderhit();
- if (AbortSearch)
- break; // Value cannot be trusted. Break out immediately!
+ // Could be MOVE_NONE when searching on a stalemate position
+ cout << "bestmove " << bestMove;
- //Save info about search result
- ValueByIteration[Iteration] = value;
+ // UCI protol is not clear on allowing sending an empty ponder move, instead
+ // it is clear that ponder move is optional. So skip it if empty.
+ if (ponderMove != MOVE_NONE)
+ cout << " ponder " << ponderMove;
- // Drop the easy move if differs from the new best move
- if (ss->pv[0] != EasyMove)
- EasyMove = MOVE_NONE;
+ cout << endl;
+}
- if (UseTimeManagement)
- {
- // Time to stop?
- bool stopSearch = false;
-
- // Stop search early if there is only a single legal move,
- // we search up to Iteration 6 anyway to get a proper score.
- if (Iteration >= 6 && rml.move_count() == 1)
- stopSearch = true;
-
- // Stop search early when the last two iterations returned a mate score
- if ( Iteration >= 6
- && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
- && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
- stopSearch = true;
-
- // Stop search early if one move seems to be much better than the others
- int64_t nodes = TM.nodes_searched();
- if ( Iteration >= 8
- && EasyMove == ss->pv[0]
- && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100
- && current_search_time() > MaxSearchTime / 16)
- ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100
- && current_search_time() > MaxSearchTime / 32)))
- stopSearch = true;
-
- // Add some extra time if the best move has changed during the last two iterations
- if (Iteration > 5 && Iteration <= 50)
- ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2)
- + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
-
- // Stop search if most of MaxSearchTime is consumed at the end of the
- // iteration. We probably don't have enough time to search the first
- // move at the next iteration anyway.
- if (current_search_time() > ((MaxSearchTime + ExtraSearchTime) * 80) / 128)
- stopSearch = true;
-
- if (stopSearch)
- {
- if (PonderSearch)
- StopOnPonderhit = true;
- else
- break;
- }
- }
- if (MaxDepth && Iteration >= MaxDepth)
- break;
- }
+namespace {
- // If we are pondering or in infinite search, we shouldn't print the
- // best move before we are told to do so.
- if (!AbortSearch && (PonderSearch || InfiniteSearch))
- wait_for_stop_or_ponderhit();
- else
- // Print final search statistics
- cout << "info nodes " << TM.nodes_searched()
- << " nps " << nps()
- << " time " << current_search_time()
- << " hashfull " << TT.full() << endl;
-
- // Print the best move and the ponder move to the standard output
- if (ss->pv[0] == MOVE_NONE)
- {
- ss->pv[0] = rml.get_move(0);
- ss->pv[1] = MOVE_NONE;
- }
+ // id_loop() is the main iterative deepening loop. It calls search() repeatedly
+ // with increasing depth until the allocated thinking time has been consumed,
+ // user stops the search, or the maximum search depth is reached.
- assert(ss->pv[0] != MOVE_NONE);
+ Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove) {
- cout << "bestmove " << ss->pv[0];
+ Stack ss[PLY_MAX_PLUS_2];
+ Value bestValues[PLY_MAX_PLUS_2];
+ int bestMoveChanges[PLY_MAX_PLUS_2];
+ int depth, aspirationDelta;
+ Value bestValue, alpha, beta;
+ Move bestMove, skillBest, skillPonder;
+ bool bestMoveNeverChanged = true;
- if (ss->pv[1] != MOVE_NONE)
- cout << " ponder " << ss->pv[1];
+ // Initialize stuff before a new search
+ memset(ss, 0, 4 * sizeof(Stack));
+ TT.new_search();
+ H.clear();
+ *ponderMove = bestMove = skillBest = skillPonder = MOVE_NONE;
+ depth = aspirationDelta = 0;
+ bestValue = alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
+ ss->currentMove = MOVE_NULL; // Hack to skip update gains
- cout << endl;
+ // Moves to search are verified and copied
+ Rml.init(pos, rootMoves);
- if (UseLogFile)
+ // Handle special case of searching on a mate/stalemate position
+ if (Rml.empty())
{
- if (dbg_show_mean)
- dbg_print_mean(LogFile);
+ cout << "info" << depth_to_uci(DEPTH_ZERO)
+ << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW, alpha, beta) << endl;
- if (dbg_show_hit_rate)
- dbg_print_hit_rate(LogFile);
-
- LogFile << "\nNodes: " << TM.nodes_searched()
- << "\nNodes/second: " << nps()
- << "\nBest move: " << move_to_san(p, ss->pv[0]);
-
- StateInfo st;
- p.do_move(ss->pv[0], st);
- LogFile << "\nPonder move: "
- << move_to_san(p, ss->pv[1]) // Works also with MOVE_NONE
- << endl;
+ return MOVE_NONE;
}
- return rml.get_move_score(0);
- }
-
- // root_search() is the function which searches the root node. It is
- // similar to search_pv except that it uses a different move ordering
- // scheme, prints some information to the standard output and handles
- // the fail low/high loops.
-
- Value root_search(Position& pos, SearchStack* ss, RootMoveList& rml, Value* alphaPtr, Value* betaPtr) {
-
- EvalInfo ei;
- StateInfo st;
- CheckInfo ci(pos);
- int64_t nodes;
- Move move;
- Depth depth, ext, newDepth;
- Value value, alpha, beta;
- bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
- int researchCountFH, researchCountFL;
-
- researchCountFH = researchCountFL = 0;
- alpha = *alphaPtr;
- beta = *betaPtr;
- isCheck = pos.is_check();
-
- // Step 1. Initialize node and poll (omitted at root, init_ss_array() has already initialized root node)
- // Step 2. Check for aborted search (omitted at root)
- // Step 3. Mate distance pruning (omitted at root)
- // Step 4. Transposition table lookup (omitted at root)
-
- // Step 5. Evaluate the position statically
- // At root we do this only to get reference value for child nodes
- if (!isCheck)
- ss->eval = evaluate(pos, ei, 0);
-
- // Step 6. Razoring (omitted at root)
- // Step 7. Static null move pruning (omitted at root)
- // Step 8. Null move search with verification search (omitted at root)
- // Step 9. Internal iterative deepening (omitted at root)
-
- // Step extra. Fail low loop
- // We start with small aspiration window and in case of fail low, we research
- // with bigger window until we are not failing low anymore.
- while (1)
+ // Iterative deepening loop until requested to stop or target depth reached
+ while (!Signals.stop && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth))
{
- // Sort the moves before to (re)search
- rml.sort();
-
- // Step 10. Loop through all moves in the root move list
- for (int i = 0; i < rml.move_count() && !AbortSearch; i++)
- {
- // This is used by time management
- FirstRootMove = (i == 0);
+ // Save now last iteration's scores, before Rml moves are reordered
+ for (size_t i = 0; i < Rml.size(); i++)
+ Rml[i].prevScore = Rml[i].score;
- // Save the current node count before the move is searched
- nodes = TM.nodes_searched();
+ Rml.bestMoveChanges = 0;
- // Reset beta cut-off counters
- TM.resetBetaCounters();
+ // MultiPV loop. We perform a full root search for each PV line
+ for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, Rml.size()); MultiPVIdx++)
+ {
+ // Calculate dynamic aspiration window based on previous iterations
+ if (depth >= 5 && abs(Rml[MultiPVIdx].prevScore) < VALUE_KNOWN_WIN)
+ {
+ int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
+ int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
- // Pick the next root move, and print the move and the move number to
- // the standard output.
- move = ss->currentMove = rml.get_move(i);
+ aspirationDelta = std::min(std::max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
+ aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
- if (current_search_time() >= 1000)
- cout << "info currmove " << move
- << " currmovenumber " << i + 1 << endl;
+ alpha = std::max(Rml[MultiPVIdx].prevScore - aspirationDelta, -VALUE_INFINITE);
+ beta = std::min(Rml[MultiPVIdx].prevScore + aspirationDelta, VALUE_INFINITE);
+ }
+ else
+ {
+ alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
+ }
- moveIsCheck = pos.move_is_check(move);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
+ // Start with a small aspiration window and, in case of fail high/low,
+ // research with bigger window until not failing high/low anymore.
+ do {
+ // Search starts from ss+1 to allow referencing (ss-1). This is
+ // needed by update gains and ss copy when splitting at Root.
+ bestValue = search<Root>(pos, ss+1, alpha, beta, depth * ONE_PLY);
+
+ // Bring to front the best move. It is critical that sorting is
+ // done with a stable algorithm because all the values but the first
+ // and eventually the new best one are set to -VALUE_INFINITE and
+ // we want to keep the same order for all the moves but the new
+ // PV that goes to the front. Note that in case of MultiPV search
+ // the already searched PV lines are preserved.
+ sort<RootMove>(Rml.begin() + MultiPVIdx, Rml.end());
+
+ // In case we have found an exact score and we are going to leave
+ // the fail high/low loop then reorder the PV moves, otherwise
+ // leave the last PV move in its position so to be searched again.
+ // Of course this is needed only in MultiPV search.
+ if (MultiPVIdx && bestValue > alpha && bestValue < beta)
+ sort<RootMove>(Rml.begin(), Rml.begin() + MultiPVIdx);
+
+ // Write PV back to transposition table in case the relevant entries
+ // have been overwritten during the search.
+ for (size_t i = 0; i <= MultiPVIdx; i++)
+ Rml[i].insert_pv_in_tt(pos);
+
+ // If search has been stopped exit the aspiration window loop,
+ // note that sorting and writing PV back to TT is safe becuase
+ // Rml is still valid, although refers to the previous iteration.
+ if (Signals.stop)
+ break;
- // Step 11. Decide the new search depth
- depth = (Iteration - 2) * OnePly + InitialDepth;
- ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
- newDepth = depth + ext;
+ // Send full PV info to GUI if we are going to leave the loop or
+ // if we have a fail high/low and we are deep in the search. UCI
+ // protocol requires to send all the PV lines also if are still
+ // to be searched and so refer to the previous search's score.
+ if ((bestValue > alpha && bestValue < beta) || elapsed_time() > 2000)
+ for (size_t i = 0; i < std::min(UCIMultiPV, Rml.size()); i++)
+ {
+ bool updated = (i <= MultiPVIdx);
- // Step 12. Futility pruning (omitted at root)
+ if (depth == 1 && !updated)
+ continue;
- // Step extra. Fail high loop
- // If move fails high, we research with bigger window until we are not failing
- // high anymore.
- value = - VALUE_INFINITE;
+ Depth d = (updated ? depth : depth - 1) * ONE_PLY;
+ Value s = (updated ? Rml[i].score : Rml[i].prevScore);
- while (1)
- {
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
+ cout << "info"
+ << depth_to_uci(d)
+ << (i == MultiPVIdx ? score_to_uci(s, alpha, beta) : score_to_uci(s))
+ << speed_to_uci(pos.nodes_searched())
+ << pv_to_uci(&Rml[i].pv[0], i + 1, pos.is_chess960())
+ << endl;
+ }
- // Step extra. pv search
- // We do pv search for first moves (i < MultiPV)
- // and for fail high research (value > alpha)
- if (i < MultiPV || value > alpha)
+ // In case of failing high/low increase aspiration window and
+ // research, otherwise exit the fail high/low loop.
+ if (bestValue >= beta)
{
- // Aspiration window is disabled in multi-pv case
- if (MultiPV > 1)
- alpha = -VALUE_INFINITE;
-
- // Full depth PV search, done on first move or after a fail high
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, 0);
+ beta = std::min(beta + aspirationDelta, VALUE_INFINITE);
+ aspirationDelta += aspirationDelta / 2;
}
- else
+ else if (bestValue <= alpha)
{
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth
- bool doFullDepthSearch = true;
-
- if ( depth >= 3 * OnePly
- && !dangerous
- && !captureOrPromotion
- && !move_is_castle(move))
- {
- ss->reduction = reduction<PV>(depth, i - MultiPV + 2);
- if (ss->reduction)
- {
- // Reduced depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, 0);
- doFullDepthSearch = (value > alpha);
- }
- }
+ Signals.failedLowAtRoot = true;
+ Signals.stopOnPonderhit = false;
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- // Full depth non-pv search using alpha as upperbound
- ss->reduction = Depth(0);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, true, 0);
-
- // If we are above alpha then research at same depth but as PV
- // to get a correct score or eventually a fail high above beta.
- if (value > alpha)
- value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, 0);
- }
+ alpha = std::max(alpha - aspirationDelta, -VALUE_INFINITE);
+ aspirationDelta += aspirationDelta / 2;
}
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- // Can we exit fail high loop ?
- if (AbortSearch || value < beta)
+ else
break;
- // We are failing high and going to do a research. It's important to update
- // the score before research in case we run out of time while researching.
- rml.set_move_score(i, value);
- update_pv(ss, 0);
- TT.extract_pv(pos, ss->pv, PLY_MAX);
- rml.set_move_pv(i, ss->pv);
-
- // Print information to the standard output
- print_pv_info(pos, ss, alpha, beta, value);
-
- // Prepare for a research after a fail high, each time with a wider window
- *betaPtr = beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
- researchCountFH++;
-
- } // End of fail high loop
-
- // Finished searching the move. If AbortSearch is true, the search
- // was aborted because the user interrupted the search or because we
- // ran out of time. In this case, the return value of the search cannot
- // be trusted, and we break out of the loop without updating the best
- // move and/or PV.
- if (AbortSearch)
- break;
-
- // Remember beta-cutoff and searched nodes counts for this move. The
- // info is used to sort the root moves for the next iteration.
- int64_t our, their;
- TM.get_beta_counters(pos.side_to_move(), our, their);
- rml.set_beta_counters(i, our, their);
- rml.set_move_nodes(i, TM.nodes_searched() - nodes);
-
- assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
- assert(value < beta);
-
- // Step 17. Check for new best move
- if (value <= alpha && i >= MultiPV)
- rml.set_move_score(i, -VALUE_INFINITE);
- else
- {
- // PV move or new best move!
-
- // Update PV
- rml.set_move_score(i, value);
- update_pv(ss, 0);
- TT.extract_pv(pos, ss->pv, PLY_MAX);
- rml.set_move_pv(i, ss->pv);
-
- if (MultiPV == 1)
- {
- // We record how often the best move has been changed in each
- // iteration. This information is used for time managment: When
- // the best move changes frequently, we allocate some more time.
- if (i > 0)
- BestMoveChangesByIteration[Iteration]++;
-
- // Print information to the standard output
- print_pv_info(pos, ss, alpha, beta, value);
-
- // Raise alpha to setup proper non-pv search upper bound
- if (value > alpha)
- alpha = value;
- }
- else // MultiPV > 1
- {
- rml.sort_multipv(i);
- for (int j = 0; j < Min(MultiPV, rml.move_count()); j++)
- {
- cout << "info multipv " << j + 1
- << " score " << value_to_string(rml.get_move_score(j))
- << " depth " << (j <= i ? Iteration : Iteration - 1)
- << " time " << current_search_time()
- << " nodes " << TM.nodes_searched()
- << " nps " << nps()
- << " pv ";
-
- for (int k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
- cout << rml.get_move_pv(j, k) << " ";
-
- cout << endl;
- }
- alpha = rml.get_move_score(Min(i, MultiPV - 1));
- }
- } // PV move or new best move
+ } while (abs(bestValue) < VALUE_KNOWN_WIN);
+ }
- assert(alpha >= *alphaPtr);
+ // Collect info about search result
+ bestMove = Rml[0].pv[0];
+ *ponderMove = Rml[0].pv[1];
+ bestValues[depth] = bestValue;
+ bestMoveChanges[depth] = Rml.bestMoveChanges;
- AspirationFailLow = (alpha == *alphaPtr);
+ // Skills: Do we need to pick now the best and the ponder moves ?
+ if (SkillLevelEnabled && depth == 1 + SkillLevel)
+ do_skill_level(&skillBest, &skillPonder);
- if (AspirationFailLow && StopOnPonderhit)
- StopOnPonderhit = false;
+ if (Options["Use Search Log"].value<bool>())
+ {
+ Log log(Options["Search Log Filename"].value<string>());
+ log << pretty_pv(pos, depth, bestValue, elapsed_time(), &Rml[0].pv[0]) << endl;
}
- // Can we exit fail low loop ?
- if (AbortSearch || !AspirationFailLow)
- break;
+ // Filter out startup noise when monitoring best move stability
+ if (depth > 2 && bestMoveChanges[depth])
+ bestMoveNeverChanged = false;
+
+ // Do we have time for the next iteration? Can we stop searching now?
+ if (!Signals.stop && !Signals.stopOnPonderhit && Limits.useTimeManagement())
+ {
+ bool stop = false; // Local variable instead of the volatile Signals.stop
+
+ // Take in account some extra time if the best move has changed
+ if (depth > 4 && depth < 50)
+ TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth - 1]);
+
+ // Stop search if most of available time is already consumed. We probably don't
+ // have enough time to search the first move at the next iteration anyway.
+ if (elapsed_time() > (TimeMgr.available_time() * 62) / 100)
+ stop = true;
+
+ // Stop search early if one move seems to be much better than others
+ if ( depth >= 10
+ && !stop
+ && ( bestMoveNeverChanged
+ || elapsed_time() > (TimeMgr.available_time() * 40) / 100))
+ {
+ Value rBeta = bestValue - EasyMoveMargin;
+ (ss+1)->excludedMove = bestMove;
+ (ss+1)->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss+1, rBeta - 1, rBeta, (depth * ONE_PLY) / 2);
+ (ss+1)->skipNullMove = false;
+ (ss+1)->excludedMove = MOVE_NONE;
+
+ if (v < rBeta)
+ stop = true;
+ }
- // Prepare for a research after a fail low, each time with a wider window
- *alphaPtr = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
- researchCountFL++;
+ if (stop)
+ {
+ // If we are allowed to ponder do not stop the search now but
+ // keep pondering until GUI sends "ponderhit" or "stop".
+ if (Limits.ponder)
+ Signals.stopOnPonderhit = true;
+ else
+ Signals.stop = true;
+ }
+ }
+ }
- } // Fail low loop
+ // When using skills overwrite best and ponder moves with the sub-optimal ones
+ if (SkillLevelEnabled)
+ {
+ if (skillBest == MOVE_NONE) // Still unassigned ?
+ do_skill_level(&skillBest, &skillPonder);
- // Sort the moves before to return
- rml.sort();
+ bestMove = skillBest;
+ *ponderMove = skillPonder;
+ }
- return alpha;
+ return bestMove;
}
- // search<>() is the main search function for both PV and non-PV nodes
+ // search<>() is the main search function for both PV and non-PV nodes and for
+ // normal and SplitPoint nodes. When called just after a split point the search
+ // is simpler because we have already probed the hash table, done a null move
+ // search, and searched the first move before splitting, we don't have to repeat
+ // all this work again. We also don't need to store anything to the hash table
+ // here: This is taken care of after we return from the split point.
+
+ template <NodeType NT>
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
- template <NodeType PvNode>
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth,
- bool allowNullmove, int threadID) {
+ const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot);
+ const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot);
+ const bool RootNode = (NT == Root || NT == SplitPointRoot);
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
- assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
- assert(threadID >= 0 && threadID < TM.active_threads());
+ assert(pos.thread() >= 0 && pos.thread() < Threads.size());
- Move movesSearched[256];
- EvalInfo ei;
+ Move movesSearched[MAX_MOVES];
+ int64_t nodes;
StateInfo st;
- const TTEntry* tte;
+ const TTEntry *tte;
Key posKey;
- Move ttMove, move, excludedMove;
+ Move ttMove, move, excludedMove, threatMove;
Depth ext, newDepth;
+ ValueType vt;
Value bestValue, value, oldAlpha;
- Value refinedValue, nullValue, futilityValueScaled; // Non-PV specific
- bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
- bool mateThreat = false;
- int moveCount = 0;
- int ply = pos.ply();
+ Value refinedValue, nullValue, futilityBase, futilityValue;
+ bool isPvMove, inCheck, singularExtensionNode, givesCheck;
+ bool captureOrPromotion, dangerous, doFullDepthSearch;
+ int moveCount = 0, playedMoveCount = 0;
+ Thread& thread = Threads[pos.thread()];
+ SplitPoint* sp = NULL;
+
refinedValue = bestValue = value = -VALUE_INFINITE;
oldAlpha = alpha;
+ inCheck = pos.in_check();
+ ss->ply = (ss-1)->ply + 1;
- // Step 1. Initialize node and poll. Polling can abort search
- TM.incrementNodeCounter(threadID);
- ss->init(ply);
- (ss + 1)->excludedMove = MOVE_NONE;
- (ss + 2)->initKillers();
+ // Used to send selDepth info to GUI
+ if (PvNode && thread.maxPly < ss->ply)
+ thread.maxPly = ss->ply;
- if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
+ // Step 1. Initialize node
+ if (!SpNode)
+ {
+ ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
+ (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
+ (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+ }
+ else
{
- NodesSincePoll = 0;
- poll();
+ sp = ss->sp;
+ tte = NULL;
+ ttMove = excludedMove = MOVE_NONE;
+ threatMove = sp->threatMove;
+ goto split_point_start;
}
// Step 2. Check for aborted search and immediate draw
- if (AbortSearch || TM.thread_should_stop(threadID))
- return Value(0);
-
- if (pos.is_draw() || ply >= PLY_MAX - 1)
+ if (( Signals.stop
+ || pos.is_draw<false>()
+ || ss->ply > PLY_MAX) && !RootNode)
return VALUE_DRAW;
// Step 3. Mate distance pruning
- alpha = Max(value_mated_in(ply), alpha);
- beta = Min(value_mate_in(ply+1), beta);
- if (alpha >= beta)
- return alpha;
+ if (!RootNode)
+ {
+ alpha = std::max(value_mated_in(ss->ply), alpha);
+ beta = std::min(value_mate_in(ss->ply+1), beta);
+ if (alpha >= beta)
+ return alpha;
+ }
// Step 4. Transposition table lookup
-
// We don't want the score of a partial search to overwrite a previous full search
- // TT value, so we use a different position key in case of an excluded move exists.
+ // TT value, so we use a different position key in case of an excluded move.
excludedMove = ss->excludedMove;
posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
+ tte = TT.probe(posKey);
+ ttMove = RootNode ? Rml[MultiPVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
+
+ // At PV nodes we check for exact scores, while at non-PV nodes we check for
+ // a fail high/low. Biggest advantage at probing at PV nodes is to have a
+ // smooth experience in analysis mode. We don't probe at Root nodes otherwise
+ // we should also update RootMoveList to avoid bogus output.
+ if (!RootNode && tte && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
+ : can_return_tt(tte, depth, beta, ss->ply)))
+ {
+ TT.refresh(tte);
+ ss->bestMove = move = ttMove; // Can be MOVE_NONE
+ value = value_from_tt(tte->value(), ss->ply);
+
+ if ( value >= beta
+ && move
+ && !pos.is_capture_or_promotion(move)
+ && move != ss->killers[0])
+ {
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
+ }
+ return value;
+ }
- tte = TT.retrieve(posKey);
- ttMove = (tte ? tte->move() : MOVE_NONE);
-
- // At PV nodes, we don't use the TT for pruning, but only for move ordering.
- // This is to avoid problems in the following areas:
- //
- // * Repetition draw detection
- // * Fifty move rule detection
- // * Searching for a mate
- // * Printing of full PV line
-
- if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
+ // Step 5. Evaluate the position statically and update parent's gain statistics
+ if (inCheck)
+ ss->eval = ss->evalMargin = VALUE_NONE;
+ else if (tte)
{
- // Refresh tte entry to avoid aging
- TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove, tte->static_value(), tte->king_danger());
+ assert(tte->static_value() != VALUE_NONE);
- ss->currentMove = ttMove; // Can be MOVE_NONE
- return value_from_tt(tte->value(), ply);
+ ss->eval = tte->static_value();
+ ss->evalMargin = tte->static_value_margin();
+ refinedValue = refine_eval(tte, ss->eval, ss->ply);
}
-
- // Step 5. Evaluate the position statically
- // At PV nodes we do this only to update gain statistics
- isCheck = pos.is_check();
- if (!isCheck)
+ else
{
- if (tte && tte->static_value() != VALUE_NONE)
- {
- ss->eval = tte->static_value();
- ei.kingDanger[pos.side_to_move()] = tte->king_danger();
- }
- else
- ss->eval = evaluate(pos, ei, threadID);
+ refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
+ TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
+ }
- refinedValue = refine_eval(tte, ss->eval, ply); // Enhance accuracy with TT value if possible
- update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
+ // Update gain for the parent non-capture move given the static position
+ // evaluation before and after the move.
+ if ( (move = (ss-1)->currentMove) != MOVE_NULL
+ && (ss-1)->eval != VALUE_NONE
+ && ss->eval != VALUE_NONE
+ && pos.captured_piece_type() == PIECE_TYPE_NONE
+ && !is_special(move))
+ {
+ Square to = move_to(move);
+ H.update_gain(pos.piece_on(to), to, -(ss-1)->eval - ss->eval);
}
// Step 6. Razoring (is omitted in PV nodes)
if ( !PvNode
&& depth < RazorDepth
- && !isCheck
- && refinedValue < beta - razor_margin(depth)
+ && !inCheck
+ && refinedValue + razor_margin(depth) < beta
&& ttMove == MOVE_NONE
- && (ss-1)->currentMove != MOVE_NULL
- && !value_is_mate(beta)
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& !pos.has_pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, Depth(0), threadID);
+ Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
if (v < rbeta)
// Logically we should return (v + razor_margin(depth)), but
// surprisingly this did slightly weaker in tests.
// We're betting that the opponent doesn't have a move that will reduce
// the score by more than futility_margin(depth) if we do a null move.
if ( !PvNode
- && allowNullmove
+ && !ss->skipNullMove
&& depth < RazorDepth
- && refinedValue >= beta + futility_margin(depth, 0)
- && !isCheck
- && !value_is_mate(beta)
+ && !inCheck
+ && refinedValue - futility_margin(depth, 0) >= beta
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& pos.non_pawn_material(pos.side_to_move()))
return refinedValue - futility_margin(depth, 0);
// Step 8. Null move search with verification search (is omitted in PV nodes)
- // When we jump directly to qsearch() we do a null move only if static value is
- // at least beta. Otherwise we do a null move if static value is not more than
- // NullMoveMargin under beta.
if ( !PvNode
- && allowNullmove
- && depth > OnePly
- && refinedValue >= beta - (depth >= 4 * OnePly ? NullMoveMargin : 0)
- && !isCheck
- && !value_is_mate(beta)
+ && !ss->skipNullMove
+ && depth > ONE_PLY
+ && !inCheck
+ && refinedValue >= beta
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
// Null move dynamic reduction based on depth
- int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0);
+ int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
// Null move dynamic reduction based on value
- if (refinedValue - beta > PawnValueMidgame)
+ if (refinedValue - PawnValueMidgame > beta)
R++;
- pos.do_null_move(st);
-
- nullValue = depth-R*OnePly < OnePly ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*OnePly, false, threadID);
- pos.undo_null_move();
+ pos.do_null_move<true>(st);
+ (ss+1)->skipNullMove = true;
+ nullValue = depth-R*ONE_PLY < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY);
+ (ss+1)->skipNullMove = false;
+ pos.do_null_move<false>(st);
if (nullValue >= beta)
{
// Do not return unproven mate scores
- if (nullValue >= value_mate_in(PLY_MAX))
+ if (nullValue >= VALUE_MATE_IN_PLY_MAX)
nullValue = beta;
- // Do zugzwang verification search at high depths
- if ( depth < 6 * OnePly
- || search<NonPV>(pos, ss, alpha, beta, depth-5*OnePly, false, threadID) >= beta)
+ if (depth < 6 * ONE_PLY)
+ return nullValue;
+
+ // Do verification search at high depths
+ ss->skipNullMove = true;
+ Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY);
+ ss->skipNullMove = false;
+
+ if (v >= beta)
return nullValue;
}
else
// move which was reduced. If a connection is found, return a fail
// low score (which will cause the reduced move to fail high in the
// parent node, which will trigger a re-search with full depth).
- if (nullValue == value_mated_in(ply + 2))
- mateThreat = true;
+ threatMove = (ss+1)->bestMove;
- ss->threatMove = (ss+1)->currentMove;
if ( depth < ThreatDepth
&& (ss-1)->reduction
- && connected_moves(pos, (ss-1)->currentMove, ss->threatMove))
+ && threatMove != MOVE_NONE
+ && connected_moves(pos, (ss-1)->currentMove, threatMove))
return beta - 1;
}
}
- // Step 9. Internal iterative deepening
- if ( depth >= IIDDepth[PvNode]
- && (ttMove == MOVE_NONE || (PvNode && tte->depth() <= depth - 4 * OnePly))
- && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
+ // Step 9. ProbCut (is omitted in PV nodes)
+ // If we have a very good capture (i.e. SEE > seeValues[captured_piece_type])
+ // and a reduced search returns a value much above beta, we can (almost) safely
+ // prune the previous move.
+ if ( !PvNode
+ && depth >= RazorDepth + ONE_PLY
+ && !inCheck
+ && !ss->skipNullMove
+ && excludedMove == MOVE_NONE
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX)
+ {
+ Value rbeta = beta + 200;
+ Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY;
+
+ assert(rdepth >= ONE_PLY);
+
+ MovePicker mp(pos, ttMove, H, pos.captured_piece_type());
+ CheckInfo ci(pos);
+
+ while ((move = mp.get_next_move()) != MOVE_NONE)
+ if (pos.pl_move_is_legal(move, ci.pinned))
+ {
+ pos.do_move(move, st, ci, pos.move_gives_check(move, ci));
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth);
+ pos.undo_move(move);
+ if (value >= rbeta)
+ return value;
+ }
+ }
+
+ // Step 10. Internal iterative deepening
+ if ( depth >= IIDDepth[PvNode]
+ && ttMove == MOVE_NONE
+ && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta)))
{
- Depth d = (PvNode ? depth - 2 * OnePly : depth / 2);
- search<PvNode>(pos, ss, alpha, beta, d, false, threadID);
- ttMove = ss->pv[ply];
- tte = TT.retrieve(posKey);
+ Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
+
+ ss->skipNullMove = true;
+ search<PvNode ? PV : NonPV>(pos, ss, alpha, beta, d);
+ ss->skipNullMove = false;
+
+ tte = TT.probe(posKey);
+ ttMove = tte ? tte->move() : MOVE_NONE;
}
- // Expensive mate threat detection (only for PV nodes)
- if (PvNode)
- mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
+split_point_start: // At split points actual search starts from here
// Initialize a MovePicker object for the current position
- MovePicker mp = MovePicker(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
+ MovePickerExt<SpNode> mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
CheckInfo ci(pos);
- bool singularExtensionNode = depth >= SingularExtensionDepth[PvNode]
- && tte && tte->move()
- && !excludedMove // Do not allow recursive singular extension search
- && is_lower_bound(tte->type())
- && tte->depth() >= depth - 3 * OnePly;
-
- // Step 10. Loop through moves
- // Loop through all legal moves until no moves remain or a beta cutoff occurs
+ ss->bestMove = MOVE_NONE;
+ futilityBase = ss->eval + ss->evalMargin;
+ singularExtensionNode = !RootNode
+ && !SpNode
+ && depth >= SingularExtensionDepth[PvNode]
+ && ttMove != MOVE_NONE
+ && !excludedMove // Do not allow recursive singular extension search
+ && (tte->type() & VALUE_TYPE_LOWER)
+ && tte->depth() >= depth - 3 * ONE_PLY;
+ if (SpNode)
+ {
+ lock_grab(&(sp->lock));
+ bestValue = sp->bestValue;
+ }
+
+ // Step 11. Loop through moves
+ // Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
while ( bestValue < beta
&& (move = mp.get_next_move()) != MOVE_NONE
- && !TM.thread_should_stop(threadID))
+ && !thread.cutoff_occurred())
{
- assert(move_is_ok(move));
+ assert(is_ok(move));
if (move == excludedMove)
continue;
- singleEvasion = (isCheck && mp.number_of_evasions() == 1);
- moveIsCheck = pos.move_is_check(move, ci);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
+ // At root obey the "searchmoves" option and skip moves not listed in Root
+ // Move List, as a consequence any illegal move is also skipped. In MultiPV
+ // mode we also skip PV moves which have been already searched.
+ if (RootNode && !Rml.find(move, MultiPVIdx))
+ continue;
+
+ // At PV and SpNode nodes we want all moves to be legal since the beginning
+ if ((PvNode || SpNode) && !pos.pl_move_is_legal(move, ci.pinned))
+ continue;
+
+ if (SpNode)
+ {
+ moveCount = ++sp->moveCount;
+ lock_release(&(sp->lock));
+ }
+ else
+ moveCount++;
+
+ if (RootNode)
+ {
+ // This is used by time management
+ Signals.firstRootMove = (moveCount == 1);
+
+ // Save the current node count before the move is searched
+ nodes = pos.nodes_searched();
+
+ // For long searches send current move info to GUI
+ if (pos.thread() == 0 && elapsed_time() > 2000)
+ cout << "info" << depth_to_uci(depth)
+ << " currmove " << move
+ << " currmovenumber " << moveCount + MultiPVIdx << endl;
+ }
+
+ isPvMove = (PvNode && moveCount <= 1);
+ captureOrPromotion = pos.is_capture_or_promotion(move);
+ givesCheck = pos.move_gives_check(move, ci);
+ dangerous = givesCheck || is_dangerous(pos, move, captureOrPromotion);
+ ext = DEPTH_ZERO;
- // Step 11. Decide the new search depth
- ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
+ // Step 12. Extend checks and, in PV nodes, also dangerous moves
+ if (PvNode && dangerous)
+ ext = ONE_PLY;
- // Singular extension search. We extend the TT move if its value is much better than
- // its siblings. To verify this we do a reduced search on all the other moves but the
- // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
+ else if (givesCheck && pos.see_sign(move) >= 0)
+ ext = PvNode ? ONE_PLY : ONE_PLY / 2;
+
+ // Singular extension search. If all moves but one fail low on a search of
+ // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move
+ // is singular and should be extended. To verify this we do a reduced search
+ // on all the other moves but the ttMove, if result is lower than ttValue minus
+ // a margin then we extend ttMove.
if ( singularExtensionNode
- && move == tte->move()
- && ext < OnePly)
+ && !ext
+ && move == ttMove
+ && pos.pl_move_is_legal(move, ci.pinned))
{
- Value ttValue = value_from_tt(tte->value(), ply);
+ Value ttValue = value_from_tt(tte->value(), ss->ply);
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value b = ttValue - SingularExtensionMargin;
+ Value rBeta = ttValue - int(depth);
ss->excludedMove = move;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, false, threadID);
+ ss->skipNullMove = true;
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2);
+ ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
-
- if (v < ttValue - SingularExtensionMargin)
- ext = OnePly;
+ ss->bestMove = MOVE_NONE;
+ if (value < rBeta)
+ ext = ONE_PLY;
}
}
- newDepth = depth - OnePly + ext;
-
// Update current move (this must be done after singular extension search)
- movesSearched[moveCount++] = ss->currentMove = move;
+ newDepth = depth - ONE_PLY + ext;
- // Step 12. Futility pruning (is omitted in PV nodes)
+ // Step 13. Futility pruning (is omitted in PV nodes)
if ( !PvNode
&& !captureOrPromotion
- && !isCheck
+ && !inCheck
&& !dangerous
&& move != ttMove
- && !move_is_castle(move))
+ && !is_castle(move))
{
// Move count based pruning
if ( moveCount >= futility_move_count(depth)
- && !(ss->threatMove && connected_threat(pos, move, ss->threatMove))
- && bestValue > value_mated_in(PLY_MAX))
+ && (!threatMove || !connected_threat(pos, move, threatMove))
+ && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy
+ {
+ if (SpNode)
+ lock_grab(&(sp->lock));
+
continue;
+ }
// Value based pruning
- // We illogically ignore reduction condition depth >= 3*OnePly for predicted depth,
+ // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
// but fixing this made program slightly weaker.
- Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
- futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_on(move_from(move)), move_to(move));
+ Depth predictedDepth = newDepth - reduction<PvNode>(depth, moveCount);
+ futilityValue = futilityBase + futility_margin(predictedDepth, moveCount)
+ + H.gain(pos.piece_on(move_from(move)), move_to(move));
- if (futilityValueScaled < beta)
+ if (futilityValue < beta)
{
- if (futilityValueScaled > bestValue)
- bestValue = futilityValueScaled;
- continue;
- }
- }
-
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step extra. pv search (only in PV nodes)
- // The first move in list is the expected PV
- if (PvNode && moveCount == 1)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, threadID);
- else
- {
- // Step 14. Reduced depth search
- // If the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( depth >= 3 * OnePly
- && !captureOrPromotion
- && !dangerous
- && !move_is_castle(move)
- && !move_is_killer(move, ss))
- {
- ss->reduction = reduction<PvNode>(depth, moveCount);
- if (ss->reduction)
+ if (SpNode)
{
- Depth d = newDepth - ss->reduction;
- value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true, threadID);
-
- doFullDepthSearch = (value > alpha);
+ lock_grab(&(sp->lock));
+ if (futilityValue > sp->bestValue)
+ sp->bestValue = bestValue = futilityValue;
}
+ else if (futilityValue > bestValue)
+ bestValue = futilityValue;
- // The move failed high, but if reduction is very big we could
- // face a false positive, retry with a less aggressive reduction,
- // if the move fails high again then go with full depth search.
- if (doFullDepthSearch && ss->reduction > 2 * OnePly)
- {
- assert(newDepth - OnePly >= OnePly);
-
- ss->reduction = OnePly;
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, true, threadID);
- doFullDepthSearch = (value > alpha);
- }
- ss->reduction = Depth(0); // Restore original reduction
+ continue;
}
- // Step 15. Full depth search
- if (doFullDepthSearch)
+ // Prune moves with negative SEE at low depths
+ if ( predictedDepth < 2 * ONE_PLY
+ && bestValue > VALUE_MATED_IN_PLY_MAX
+ && pos.see_sign(move) < 0)
{
- value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, true, threadID);
-
- // Step extra. pv search (only in PV nodes)
- // Search only for possible new PV nodes, if instead value >= beta then
- // parent node fails low with value <= alpha and tries another move.
- if (PvNode && value > alpha && value < beta)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -beta, -alpha, Depth(0), threadID)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, threadID);
+ if (SpNode)
+ lock_grab(&(sp->lock));
+
+ continue;
}
}
- // Step 16. Undo move
+ // Check for legality only before to do the move
+ if (!pos.pl_move_is_legal(move, ci.pinned))
+ {
+ moveCount--;
+ continue;
+ }
+
+ ss->currentMove = move;
+ if (!SpNode && !captureOrPromotion)
+ movesSearched[playedMoveCount++] = move;
+
+ // Step 14. Make the move
+ pos.do_move(move, st, ci, givesCheck);
+
+ // Step 15. Reduced depth search (LMR). If the move fails high will be
+ // re-searched at full depth.
+ if ( depth > 3 * ONE_PLY
+ && !isPvMove
+ && !captureOrPromotion
+ && !dangerous
+ && !is_castle(move)
+ && ss->killers[0] != move
+ && ss->killers[1] != move)
+ {
+ ss->reduction = reduction<PvNode>(depth, moveCount);
+ Depth d = newDepth - ss->reduction;
+ alpha = SpNode ? sp->alpha : alpha;
+
+ value = d < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d);
+
+ doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
+ ss->reduction = DEPTH_ZERO;
+ }
+ else
+ doFullDepthSearch = !isPvMove;
+
+ // Step 16. Full depth search, when LMR is skipped or fails high
+ if (doFullDepthSearch)
+ {
+ alpha = SpNode ? sp->alpha : alpha;
+ value = newDepth < ONE_PLY ? -qsearch<NonPV>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth);
+ }
+
+ // Only for PV nodes do a full PV search on the first move or after a fail
+ // high, in the latter case search only if value < beta, otherwise let the
+ // parent node to fail low with value <= alpha and to try another move.
+ if (PvNode && (isPvMove || (value > alpha && (RootNode || value < beta))))
+ value = newDepth < ONE_PLY ? -qsearch<PV>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth);
+
+ // Step 17. Undo move
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // Step 17. Check for new best move
+ // Step 18. Check for new best move
+ if (SpNode)
+ {
+ lock_grab(&(sp->lock));
+ bestValue = sp->bestValue;
+ alpha = sp->alpha;
+ }
+
+ // Finished searching the move. If StopRequest is true, the search
+ // was aborted because the user interrupted the search or because we
+ // ran out of time. In this case, the return value of the search cannot
+ // be trusted, and we don't update the best move and/or PV.
+ if (RootNode && !Signals.stop)
+ {
+ // Remember searched nodes counts for this move
+ RootMove* rm = Rml.find(move);
+ rm->nodes += pos.nodes_searched() - nodes;
+
+ // PV move or new best move ?
+ if (isPvMove || value > alpha)
+ {
+ // Update PV
+ rm->score = value;
+ rm->extract_pv_from_tt(pos);
+
+ // We record how often the best move has been changed in each
+ // iteration. This information is used for time management: When
+ // the best move changes frequently, we allocate some more time.
+ if (!isPvMove && MultiPV == 1)
+ Rml.bestMoveChanges++;
+ }
+ else
+ // All other moves but the PV are set to the lowest value, this
+ // is not a problem when sorting becuase sort is stable and move
+ // position in the list is preserved, just the PV is pushed up.
+ rm->score = -VALUE_INFINITE;
+
+ } // RootNode
+
if (value > bestValue)
{
bestValue = value;
- if (value > alpha)
- {
- if (PvNode && value < beta) // This guarantees that always: alpha < beta
- alpha = value;
+ ss->bestMove = move;
- update_pv(ss, ply);
+ if ( PvNode
+ && value > alpha
+ && value < beta) // We want always alpha < beta
+ alpha = value;
- if (value == value_mate_in(ply + 1))
- ss->mateKiller = move;
+ if (SpNode && !thread.cutoff_occurred())
+ {
+ sp->bestValue = value;
+ sp->ss->bestMove = move;
+ sp->alpha = alpha;
+ sp->is_betaCutoff = (value >= beta);
}
}
- // Step 18. Check for split
- if ( depth >= MinimumSplitDepth
- && TM.active_threads() > 1
+ // Step 19. Check for split
+ if ( !SpNode
+ && depth >= Threads.min_split_depth()
&& bestValue < beta
- && TM.available_thread_exists(threadID)
- && !AbortSearch
- && !TM.thread_should_stop(threadID)
- && Iteration <= 99)
- TM.split<FakeSplit>(pos, ss, &alpha, beta, &bestValue, depth,
- mateThreat, &moveCount, &mp, threadID, PvNode);
+ && Threads.available_slave_exists(pos.thread())
+ && !Signals.stop
+ && !thread.cutoff_occurred())
+ bestValue = Threads.split<FakeSplit>(pos, ss, alpha, beta, bestValue, depth,
+ threatMove, moveCount, &mp, NT);
}
- // Step 19. Check for mate and stalemate
- // All legal moves have been searched and if there are
- // no legal moves, it must be mate or stalemate.
- // If one move was excluded return fail low score.
- if (!moveCount)
- return excludedMove ? oldAlpha : (isCheck ? value_mated_in(ply) : VALUE_DRAW);
+ // Step 20. Check for mate and stalemate
+ // All legal moves have been searched and if there are no legal moves, it
+ // must be mate or stalemate. Note that we can have a false positive in
+ // case of StopRequest or thread.cutoff_occurred() are set, but this is
+ // harmless because return value is discarded anyhow in the parent nodes.
+ // If we are in a singular extension search then return a fail low score.
+ if (!SpNode && !moveCount)
+ return excludedMove ? oldAlpha : inCheck ? value_mated_in(ss->ply) : VALUE_DRAW;
- // Step 20. Update tables
+ // Step 21. Update tables
// If the search is not aborted, update the transposition table,
// history counters, and killer moves.
- if (AbortSearch || TM.thread_should_stop(threadID))
- return bestValue;
+ if (!SpNode && !Signals.stop && !thread.cutoff_occurred())
+ {
+ move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
+ vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
+ : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
- if (bestValue <= oldAlpha)
- TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]);
+ TT.store(posKey, value_to_tt(bestValue, ss->ply), vt, depth, move, ss->eval, ss->evalMargin);
- else if (bestValue >= beta)
- {
- TM.incrementBetaCounter(pos.side_to_move(), depth, threadID);
- move = ss->pv[ply];
- TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move, ss->eval, ei.kingDanger[pos.side_to_move()]);
- if (!pos.move_is_capture_or_promotion(move))
+ // Update killers and history only for non capture moves that fails high
+ if ( bestValue >= beta
+ && !pos.is_capture_or_promotion(move))
{
- update_history(pos, move, depth, movesSearched, moveCount);
- update_killers(move, ss);
+ if (move != ss->killers[0])
+ {
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = move;
+ }
+ update_history(pos, move, depth, movesSearched, playedMoveCount);
}
}
- else
- TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss->pv[ply], ss->eval, ei.kingDanger[pos.side_to_move()]);
+
+ if (SpNode)
+ {
+ // Here we have the lock still grabbed
+ sp->is_slave[pos.thread()] = false;
+ sp->nodes += pos.nodes_searched();
+ lock_release(&(sp->lock));
+ }
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
return bestValue;
}
-
// qsearch() is the quiescence search function, which is called by the main
// search function when the remaining depth is zero (or, to be more precise,
- // less than OnePly).
+ // less than ONE_PLY).
- template <NodeType PvNode>
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int threadID) {
+ template <NodeType NT>
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
+ const bool PvNode = (NT == PV);
+
+ assert(NT == PV || NT == NonPV);
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
assert(depth <= 0);
- assert(pos.ply() > 0 && pos.ply() < PLY_MAX);
- assert(threadID >= 0 && threadID < TM.active_threads());
+ assert(pos.thread() >= 0 && pos.thread() < Threads.size());
- EvalInfo ei;
StateInfo st;
Move ttMove, move;
- Value staticValue, bestValue, value, futilityBase, futilityValue;
- bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
- const TTEntry* tte = NULL;
- int moveCount = 0;
- int ply = pos.ply();
+ Value bestValue, value, evalMargin, futilityValue, futilityBase;
+ bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
+ const TTEntry* tte;
+ Depth ttDepth;
+ ValueType vt;
Value oldAlpha = alpha;
- TM.incrementNodeCounter(threadID);
- ss->init(ply);
+ ss->bestMove = ss->currentMove = MOVE_NONE;
+ ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or maximum ply reached
- if (pos.is_draw() || ply >= PLY_MAX - 1)
+ if (pos.is_draw<true>() || ss->ply > PLY_MAX)
return VALUE_DRAW;
+ // Decide whether or not to include checks, this fixes also the type of
+ // TT entry depth that we are going to use. Note that in qsearch we use
+ // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
+ inCheck = pos.in_check();
+ ttDepth = (inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
+
// Transposition table lookup. At PV nodes, we don't use the TT for
// pruning, but only for move ordering.
- tte = TT.retrieve(pos.get_key());
+ tte = TT.probe(pos.get_key());
ttMove = (tte ? tte->move() : MOVE_NONE);
- if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
+ if (!PvNode && tte && can_return_tt(tte, ttDepth, beta, ss->ply))
{
- ss->currentMove = ttMove; // Can be MOVE_NONE
- return value_from_tt(tte->value(), ply);
+ ss->bestMove = ttMove; // Can be MOVE_NONE
+ return value_from_tt(tte->value(), ss->ply);
}
- isCheck = pos.is_check();
-
// Evaluate the position statically
- if (isCheck)
- staticValue = -VALUE_INFINITE;
- else if (tte && tte->static_value() != VALUE_NONE)
+ if (inCheck)
{
- staticValue = tte->static_value();
- ei.kingDanger[pos.side_to_move()] = tte->king_danger();
+ bestValue = futilityBase = -VALUE_INFINITE;
+ ss->eval = evalMargin = VALUE_NONE;
+ enoughMaterial = false;
}
else
- staticValue = evaluate(pos, ei, threadID);
-
- if (!isCheck)
{
- ss->eval = staticValue;
- update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
- }
+ if (tte)
+ {
+ assert(tte->static_value() != VALUE_NONE);
- // Initialize "stand pat score", and return it immediately if it is
- // at least beta.
- bestValue = staticValue;
+ evalMargin = tte->static_value_margin();
+ ss->eval = bestValue = tte->static_value();
+ }
+ else
+ ss->eval = bestValue = evaluate(pos, evalMargin);
- if (bestValue >= beta)
- {
- // Store the score to avoid a future costly evaluation() call
- if (!isCheck && !tte)
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, Depth(-127*OnePly), MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]);
+ // Stand pat. Return immediately if static value is at least beta
+ if (bestValue >= beta)
+ {
+ if (!tte)
+ TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
- return bestValue;
- }
+ return bestValue;
+ }
- if (bestValue > alpha)
- alpha = bestValue;
+ if (PvNode && bestValue > alpha)
+ alpha = bestValue;
- // If we are near beta then try to get a cutoff pushing checks a bit further
- bool deepChecks = (depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8);
+ // Futility pruning parameters, not needed when in check
+ futilityBase = ss->eval + evalMargin + FutilityMarginQS;
+ enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
+ }
// Initialize a MovePicker object for the current position, and prepare
// to search the moves. Because the depth is <= 0 here, only captures,
- // queen promotions and checks (only if depth == 0 or depth == -OnePly
- // and we are near beta) will be generated.
- MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H);
+ // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
+ // be generated.
+ MovePicker mp(pos, ttMove, depth, H, move_to((ss-1)->currentMove));
CheckInfo ci(pos);
- enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
- futilityBase = staticValue + FutilityMarginQS + ei.kingDanger[pos.side_to_move()];
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ( alpha < beta
+ while ( bestValue < beta
&& (move = mp.get_next_move()) != MOVE_NONE)
{
- assert(move_is_ok(move));
+ assert(is_ok(move));
- moveIsCheck = pos.move_is_check(move, ci);
-
- // Update current move
- moveCount++;
- ss->currentMove = move;
+ givesCheck = pos.move_gives_check(move, ci);
// Futility pruning
if ( !PvNode
- && enoughMaterial
- && !isCheck
- && !moveIsCheck
+ && !inCheck
+ && !givesCheck
&& move != ttMove
- && !move_is_promotion(move)
- && !pos.move_is_passed_pawn_push(move))
+ && enoughMaterial
+ && !is_promotion(move)
+ && !pos.is_passed_pawn_push(move))
{
futilityValue = futilityBase
- + pos.endgame_value_of_piece_on(move_to(move))
- + (move_is_ep(move) ? PawnValueEndgame : Value(0));
+ + PieceValueEndgame[pos.piece_on(move_to(move))]
+ + (is_enpassant(move) ? PawnValueEndgame : VALUE_ZERO);
- if (futilityValue < alpha)
+ if (futilityValue < beta)
{
if (futilityValue > bestValue)
bestValue = futilityValue;
+
continue;
}
+
+ // Prune moves with negative or equal SEE
+ if ( futilityBase < beta
+ && depth < DEPTH_ZERO
+ && pos.see(move) <= 0)
+ continue;
}
- // Detect blocking evasions that are candidate to be pruned
- evasionPrunable = isCheck
- && bestValue > value_mated_in(PLY_MAX)
- && !pos.move_is_capture(move)
- && pos.type_of_piece_on(move_from(move)) != KING
+ // Detect non-capture evasions that are candidate to be pruned
+ evasionPrunable = !PvNode
+ && inCheck
+ && bestValue > VALUE_MATED_IN_PLY_MAX
+ && !pos.is_capture(move)
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
if ( !PvNode
- && (!isCheck || evasionPrunable)
+ && (!inCheck || evasionPrunable)
&& move != ttMove
- && !move_is_promotion(move)
+ && !is_promotion(move)
&& pos.see_sign(move) < 0)
continue;
+ // Don't search useless checks
+ if ( !PvNode
+ && !inCheck
+ && givesCheck
+ && move != ttMove
+ && !pos.is_capture_or_promotion(move)
+ && ss->eval + PawnValueMidgame / 4 < beta
+ && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
+ {
+ if (ss->eval + PawnValueMidgame / 4 > bestValue)
+ bestValue = ss->eval + PawnValueMidgame / 4;
+
+ continue;
+ }
+
+ // Check for legality only before to do the move
+ if (!pos.pl_move_is_legal(move, ci.pinned))
+ continue;
+
+ // Update current move
+ ss->currentMove = move;
+
// Make and search the move
- pos.do_move(move, st, ci, moveIsCheck);
- value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-OnePly, threadID);
+ pos.do_move(move, st, ci, givesCheck);
+ value = -qsearch<NT>(pos, ss+1, -beta, -alpha, depth-ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
if (value > bestValue)
{
bestValue = value;
- if (value > alpha)
- {
+ ss->bestMove = move;
+
+ if ( PvNode
+ && value > alpha
+ && value < beta) // We want always alpha < beta
alpha = value;
- update_pv(ss, ply);
- }
}
}
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (!moveCount && isCheck) // Mate!
- return value_mated_in(ply);
+ if (inCheck && bestValue == -VALUE_INFINITE)
+ return value_mated_in(ss->ply);
// Update transposition table
- Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
- if (bestValue <= oldAlpha)
- {
- // If bestValue isn't changed it means it is still the static evaluation
- // of the node, so keep this info to avoid a future evaluation() call.
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, d, MOVE_NONE, ss->eval, ei.kingDanger[pos.side_to_move()]);
- }
- else if (bestValue >= beta)
- {
- move = ss->pv[ply];
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move, ss->eval, ei.kingDanger[pos.side_to_move()]);
+ move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
+ vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
+ : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
- // Update killers only for good checking moves
- if (!pos.move_is_capture_or_promotion(move))
- update_killers(move, ss);
- }
- else
- TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, d, ss->pv[ply], ss->eval, ei.kingDanger[pos.side_to_move()]);
+ TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, move, ss->eval, evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
}
- // sp_search() is used to search from a split point. This function is called
- // by each thread working at the split point. It is similar to the normal
- // search() function, but simpler. Because we have already probed the hash
- // table, done a null move search, and searched the first move before
- // splitting, we don't have to repeat all this work in sp_search(). We
- // also don't need to store anything to the hash table here: This is taken
- // care of after we return from the split point.
-
- template <NodeType PvNode>
- void sp_search(SplitPoint* sp, int threadID) {
+ // check_is_dangerous() tests if a checking move can be pruned in qsearch().
+ // bestValue is updated only when returning false because in that case move
+ // will be pruned.
- assert(threadID >= 0 && threadID < TM.active_threads());
- assert(TM.active_threads() > 1);
-
- StateInfo st;
- Move move;
- Depth ext, newDepth;
- Value value;
- Value futilityValueScaled; // NonPV specific
- bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
- int moveCount;
- value = -VALUE_INFINITE;
+ bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
+ {
+ Bitboard b, occ, oldAtt, newAtt, kingAtt;
+ Square from, to, ksq, victimSq;
+ Piece pc;
+ Color them;
+ Value futilityValue, bv = *bestValue;
+
+ from = move_from(move);
+ to = move_to(move);
+ them = flip(pos.side_to_move());
+ ksq = pos.king_square(them);
+ kingAtt = pos.attacks_from<KING>(ksq);
+ pc = pos.piece_on(from);
+
+ occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
+ oldAtt = pos.attacks_from(pc, from, occ);
+ newAtt = pos.attacks_from(pc, to, occ);
+
+ // Rule 1. Checks which give opponent's king at most one escape square are dangerous
+ b = kingAtt & ~pos.pieces(them) & ~newAtt & ~(1ULL << to);
+
+ if (!(b && (b & (b - 1))))
+ return true;
- Position pos(*sp->pos);
- CheckInfo ci(pos);
- int ply = pos.ply();
- SearchStack* ss = sp->sstack[threadID] + 1;
- isCheck = pos.is_check();
+ // Rule 2. Queen contact check is very dangerous
+ if ( type_of(pc) == QUEEN
+ && bit_is_set(kingAtt, to))
+ return true;
- // Step 10. Loop through moves
- // Loop through all legal moves until no moves remain or a beta cutoff occurs
- lock_grab(&(sp->lock));
+ // Rule 3. Creating new double threats with checks
+ b = pos.pieces(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
- while ( sp->bestValue < sp->beta
- && (move = sp->mp->get_next_move()) != MOVE_NONE
- && !TM.thread_should_stop(threadID))
+ while (b)
{
- moveCount = ++sp->moveCount;
- lock_release(&(sp->lock));
-
- assert(move_is_ok(move));
-
- moveIsCheck = pos.move_is_check(move, ci);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, false, sp->mateThreat, &dangerous);
- newDepth = sp->depth - OnePly + ext;
-
- // Update current move
- ss->currentMove = move;
+ victimSq = pop_1st_bit(&b);
+ futilityValue = futilityBase + PieceValueEndgame[pos.piece_on(victimSq)];
- // Step 12. Futility pruning (is omitted in PV nodes)
- if ( !PvNode
- && !captureOrPromotion
- && !isCheck
- && !dangerous
- && !move_is_castle(move))
- {
- // Move count based pruning
- if ( moveCount >= futility_move_count(sp->depth)
- && !(ss->threatMove && connected_threat(pos, move, ss->threatMove))
- && sp->bestValue > value_mated_in(PLY_MAX))
- {
- lock_grab(&(sp->lock));
- continue;
- }
-
- // Value based pruning
- Depth predictedDepth = newDepth - reduction<NonPV>(sp->depth, moveCount);
- futilityValueScaled = ss->eval + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_on(move_from(move)), move_to(move));
-
- if (futilityValueScaled < sp->beta)
- {
- lock_grab(&(sp->lock));
-
- if (futilityValueScaled > sp->bestValue)
- sp->bestValue = futilityValueScaled;
- continue;
- }
- }
-
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // Step 14. Reduced search
- // If the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
-
- if ( !captureOrPromotion
- && !dangerous
- && !move_is_castle(move)
- && !move_is_killer(move, ss))
- {
- ss->reduction = reduction<PvNode>(sp->depth, moveCount);
- if (ss->reduction)
- {
- Value localAlpha = sp->alpha;
- Depth d = newDepth - ss->reduction;
- value = d < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, d, true, threadID);
- doFullDepthSearch = (value > localAlpha);
- }
-
- // The move failed high, but if reduction is very big we could
- // face a false positive, retry with a less aggressive reduction,
- // if the move fails high again then go with full depth search.
- if (doFullDepthSearch && ss->reduction > 2 * OnePly)
- {
- assert(newDepth - OnePly >= OnePly);
-
- ss->reduction = OnePly;
- Value localAlpha = sp->alpha;
- value = -search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth-ss->reduction, true, threadID);
- doFullDepthSearch = (value > localAlpha);
- }
- ss->reduction = Depth(0); // Restore original reduction
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- Value localAlpha = sp->alpha;
- value = newDepth < OnePly ? -qsearch<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, Depth(0), threadID)
- : - search<NonPV>(pos, ss+1, -(localAlpha+1), -localAlpha, newDepth, true, threadID);
-
- // Step extra. pv search (only in PV nodes)
- // Search only for possible new PV nodes, if instead value >= beta then
- // parent node fails low with value <= alpha and tries another move.
- if (PvNode && value > localAlpha && value < sp->beta)
- value = newDepth < OnePly ? -qsearch<PV>(pos, ss+1, -sp->beta, -sp->alpha, Depth(0), threadID)
- : - search<PV>(pos, ss+1, -sp->beta, -sp->alpha, newDepth, false, threadID);
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
-
- // Step 17. Check for new best move
- lock_grab(&(sp->lock));
-
- if (value > sp->bestValue && !TM.thread_should_stop(threadID))
- {
- sp->bestValue = value;
-
- if (sp->bestValue > sp->alpha)
- {
- if (!PvNode || value >= sp->beta)
- sp->stopRequest = true;
-
- if (PvNode && value < sp->beta) // This guarantees that always: sp->alpha < sp->beta
- sp->alpha = value;
+ // Note that here we generate illegal "double move"!
+ if ( futilityValue >= beta
+ && pos.see_sign(make_move(from, victimSq)) >= 0)
+ return true;
- sp_update_pv(sp->parentSstack, ss, ply);
- }
- }
+ if (futilityValue > bv)
+ bv = futilityValue;
}
- /* Here we have the lock still grabbed */
-
- sp->slaves[threadID] = 0;
-
- lock_release(&(sp->lock));
- }
-
- // update_pv() is called whenever a search returns a value > alpha.
- // It updates the PV in the SearchStack object corresponding to the
- // current node.
-
- void update_pv(SearchStack* ss, int ply) {
-
- assert(ply >= 0 && ply < PLY_MAX);
-
- int p;
-
- ss->pv[ply] = ss->currentMove;
-
- for (p = ply + 1; (ss+1)->pv[p] != MOVE_NONE; p++)
- ss->pv[p] = (ss+1)->pv[p];
-
- ss->pv[p] = MOVE_NONE;
- }
-
-
- // sp_update_pv() is a variant of update_pv for use at split points. The
- // difference between the two functions is that sp_update_pv also updates
- // the PV at the parent node.
-
- void sp_update_pv(SearchStack* pss, SearchStack* ss, int ply) {
-
- assert(ply >= 0 && ply < PLY_MAX);
-
- int p;
-
- ss->pv[ply] = pss->pv[ply] = ss->currentMove;
-
- for (p = ply + 1; (ss+1)->pv[p] != MOVE_NONE; p++)
- ss->pv[p] = pss->pv[p] = (ss+1)->pv[p];
-
- ss->pv[p] = pss->pv[p] = MOVE_NONE;
+ // Update bestValue only if check is not dangerous (because we will prune the move)
+ *bestValue = bv;
+ return false;
}
bool connected_moves(const Position& pos, Move m1, Move m2) {
Square f1, t1, f2, t2;
- Piece p;
-
- assert(move_is_ok(m1));
- assert(move_is_ok(m2));
+ Piece p1, p2;
+ Square ksq;
- if (m2 == MOVE_NONE)
- return false;
+ assert(is_ok(m1));
+ assert(is_ok(m2));
// Case 1: The moving piece is the same in both moves
f2 = move_from(m2);
return true;
// Case 3: Moving through the vacated square
- if ( piece_is_slider(pos.piece_on(f2))
+ p2 = pos.piece_on(f2);
+ if ( piece_is_slider(p2)
&& bit_is_set(squares_between(f2, t2), f1))
return true;
// Case 4: The destination square for m2 is defended by the moving piece in m1
- p = pos.piece_on(t1);
- if (bit_is_set(pos.attacks_from(p, t1), t2))
+ p1 = pos.piece_on(t1);
+ if (bit_is_set(pos.attacks_from(p1, t1), t2))
return true;
// Case 5: Discovered check, checking piece is the piece moved in m1
- if ( piece_is_slider(p)
- && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
- && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
+ ksq = pos.king_square(pos.side_to_move());
+ if ( piece_is_slider(p1)
+ && bit_is_set(squares_between(t1, ksq), f2))
{
- // discovered_check_candidates() works also if the Position's side to
- // move is the opposite of the checking piece.
- Color them = opposite_color(pos.side_to_move());
- Bitboard dcCandidates = pos.discovered_check_candidates(them);
-
- if (bit_is_set(dcCandidates, f2))
+ Bitboard occ = pos.occupied_squares();
+ clear_bit(&occ, f2);
+ if (bit_is_set(pos.attacks_from(p1, t1, occ), ksq))
return true;
}
return false;
}
- // value_is_mate() checks if the given value is a mate one
- // eventually compensated for the ply.
-
- bool value_is_mate(Value value) {
+ // value_to_tt() adjusts a mate score from "plies to mate from the root" to
+ // "plies to mate from the current ply". Non-mate scores are unchanged.
+ // The function is called before storing a value to the transposition table.
- assert(abs(value) <= VALUE_INFINITE);
+ Value value_to_tt(Value v, int ply) {
- return value <= value_mated_in(PLY_MAX)
- || value >= value_mate_in(PLY_MAX);
- }
+ if (v >= VALUE_MATE_IN_PLY_MAX)
+ return v + ply;
+ if (v <= VALUE_MATED_IN_PLY_MAX)
+ return v - ply;
- // move_is_killer() checks if the given move is among the
- // killer moves of that ply.
-
- bool move_is_killer(Move m, SearchStack* ss) {
-
- const Move* k = ss->killers;
- for (int i = 0; i < KILLER_MAX; i++, k++)
- if (*k == m)
- return true;
-
- return false;
+ return v;
}
- // extension() decides whether a move should be searched with normal depth,
- // or with extended depth. Certain classes of moves (checking moves, in
- // particular) are searched with bigger depth than ordinary moves and in
- // any case are marked as 'dangerous'. Note that also if a move is not
- // extended, as example because the corresponding UCI option is set to zero,
- // the move is marked as 'dangerous' so, at least, we avoid to prune it.
- template <NodeType PvNode>
- Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
- bool singleEvasion, bool mateThreat, bool* dangerous) {
-
- assert(m != MOVE_NONE);
-
- Depth result = Depth(0);
- *dangerous = moveIsCheck | singleEvasion | mateThreat;
+ // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
+ // the transposition table to a mate score corrected for the current ply.
- if (*dangerous)
- {
- if (moveIsCheck)
- result += CheckExtension[PvNode];
-
- if (singleEvasion)
- result += SingleEvasionExtension[PvNode];
-
- if (mateThreat)
- result += MateThreatExtension[PvNode];
- }
-
- if (pos.type_of_piece_on(move_from(m)) == PAWN)
- {
- Color c = pos.side_to_move();
- if (relative_rank(c, move_to(m)) == RANK_7)
- {
- result += PawnPushTo7thExtension[PvNode];
- *dangerous = true;
- }
- if (pos.pawn_is_passed(c, move_to(m)))
- {
- result += PassedPawnExtension[PvNode];
- *dangerous = true;
- }
- }
+ Value value_from_tt(Value v, int ply) {
- if ( captureOrPromotion
- && pos.type_of_piece_on(move_to(m)) != PAWN
- && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
- - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
- && !move_is_promotion(m)
- && !move_is_ep(m))
- {
- result += PawnEndgameExtension[PvNode];
- *dangerous = true;
- }
+ if (v >= VALUE_MATE_IN_PLY_MAX)
+ return v - ply;
- if ( PvNode
- && captureOrPromotion
- && pos.type_of_piece_on(move_to(m)) != PAWN
- && pos.see_sign(m) >= 0)
- {
- result += OnePly/2;
- *dangerous = true;
- }
+ if (v <= VALUE_MATED_IN_PLY_MAX)
+ return v + ply;
- return Min(result, OnePly);
+ return v;
}
// connected_threat() tests whether it is safe to forward prune a move or if
- // is somehow coonected to the threat move returned by null search.
+ // is somehow connected to the threat move returned by null search.
bool connected_threat(const Position& pos, Move m, Move threat) {
- assert(move_is_ok(m));
- assert(threat && move_is_ok(threat));
- assert(!pos.move_is_check(m));
- assert(!pos.move_is_capture_or_promotion(m));
- assert(!pos.move_is_passed_pawn_push(m));
+ assert(is_ok(m));
+ assert(is_ok(threat));
+ assert(!pos.is_capture_or_promotion(m));
+ assert(!pos.is_passed_pawn_push(m));
Square mfrom, mto, tfrom, tto;
return true;
// Case 2: If the threatened piece has value less than or equal to the
- // value of the threatening piece, don't prune move which defend it.
- if ( pos.move_is_capture(threat)
- && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
- || pos.type_of_piece_on(tfrom) == KING)
+ // value of the threatening piece, don't prune moves which defend it.
+ if ( pos.is_capture(threat)
+ && ( PieceValueMidgame[pos.piece_on(tfrom)] >= PieceValueMidgame[pos.piece_on(tto)]
+ || type_of(pos.piece_on(tfrom)) == KING)
&& pos.move_attacks_square(m, tto))
return true;
}
- // ok_to_use_TT() returns true if a transposition table score
- // can be used at a given point in search.
+ // can_return_tt() returns true if a transposition table score
+ // can be used to cut-off at a given point in search.
- bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
+ bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply) {
Value v = value_from_tt(tte->value(), ply);
return ( tte->depth() >= depth
- || v >= Max(value_mate_in(PLY_MAX), beta)
- || v < Min(value_mated_in(PLY_MAX), beta))
+ || v >= std::max(VALUE_MATE_IN_PLY_MAX, beta)
+ || v < std::min(VALUE_MATED_IN_PLY_MAX, beta))
- && ( (is_lower_bound(tte->type()) && v >= beta)
- || (is_upper_bound(tte->type()) && v < beta));
+ && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
+ || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
}
Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
- if (!tte)
- return defaultEval;
+ assert(tte);
Value v = value_from_tt(tte->value(), ply);
- if ( (is_lower_bound(tte->type()) && v >= defaultEval)
- || (is_upper_bound(tte->type()) && v < defaultEval))
+ if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
+ || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
return v;
return defaultEval;
void update_history(const Position& pos, Move move, Depth depth,
Move movesSearched[], int moveCount) {
-
Move m;
+ Value bonus = Value(int(depth) * int(depth));
- H.success(pos.piece_on(move_from(move)), move_to(move), depth);
+ H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
for (int i = 0; i < moveCount - 1; i++)
{
assert(m != move);
- if (!pos.move_is_capture_or_promotion(m))
- H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
+ H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
}
}
- // update_killers() add a good move that produced a beta-cutoff
- // among the killer moves of that ply.
-
- void update_killers(Move m, SearchStack* ss) {
-
- if (m == ss->killers[0])
- return;
-
- for (int i = KILLER_MAX - 1; i > 0; i--)
- ss->killers[i] = ss->killers[i - 1];
-
- ss->killers[0] = m;
- }
-
-
- // update_gains() updates the gains table of a non-capture move given
- // the static position evaluation before and after the move.
-
- void update_gains(const Position& pos, Move m, Value before, Value after) {
-
- if ( m != MOVE_NULL
- && before != VALUE_NONE
- && after != VALUE_NONE
- && pos.captured_piece() == NO_PIECE_TYPE
- && !move_is_castle(m)
- && !move_is_promotion(m))
- H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
- }
-
-
// current_search_time() returns the number of milliseconds which have passed
// since the beginning of the current search.
- int current_search_time() {
-
- return get_system_time() - SearchStartTime;
- }
-
+ int elapsed_time(bool reset) {
- // nps() computes the current nodes/second count.
+ static int searchStartTime;
- int nps() {
+ if (reset)
+ searchStartTime = get_system_time();
- int t = current_search_time();
- return (t > 0 ? int((TM.nodes_searched() * 1000) / t) : 0);
+ return get_system_time() - searchStartTime;
}
- // poll() performs two different functions: It polls for user input, and it
- // looks at the time consumed so far and decides if it's time to abort the
- // search.
-
- void poll() {
-
- static int lastInfoTime;
- int t = current_search_time();
-
- // Poll for input
- if (Bioskey())
- {
- // We are line oriented, don't read single chars
- std::string command;
-
- if (!std::getline(std::cin, command))
- command = "quit";
-
- if (command == "quit")
- {
- AbortSearch = true;
- PonderSearch = false;
- Quit = true;
- return;
- }
- else if (command == "stop")
- {
- AbortSearch = true;
- PonderSearch = false;
- }
- else if (command == "ponderhit")
- ponderhit();
- }
-
- // Print search information
- if (t < 1000)
- lastInfoTime = 0;
-
- else if (lastInfoTime > t)
- // HACK: Must be a new search where we searched less than
- // NodesBetweenPolls nodes during the first second of search.
- lastInfoTime = 0;
-
- else if (t - lastInfoTime >= 1000)
- {
- lastInfoTime = t;
-
- if (dbg_show_mean)
- dbg_print_mean();
-
- if (dbg_show_hit_rate)
- dbg_print_hit_rate();
+ // score_to_uci() converts a value to a string suitable for use with the UCI
+ // protocol specifications:
+ //
+ // cp <x> The score from the engine's point of view in centipawns.
+ // mate <y> Mate in y moves, not plies. If the engine is getting mated
+ // use negative values for y.
- cout << "info nodes " << TM.nodes_searched() << " nps " << nps()
- << " time " << t << " hashfull " << TT.full() << endl;
- }
+ string score_to_uci(Value v, Value alpha, Value beta) {
- // Should we stop the search?
- if (PonderSearch)
- return;
+ std::stringstream s;
- bool stillAtFirstMove = FirstRootMove
- && !AspirationFailLow
- && t > MaxSearchTime + ExtraSearchTime;
+ if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
+ s << " score cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
+ else
+ s << " score mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
- bool noMoreTime = t > AbsoluteMaxSearchTime
- || stillAtFirstMove;
+ s << (v >= beta ? " lowerbound" : v <= alpha ? " upperbound" : "");
- if ( (Iteration >= 3 && UseTimeManagement && noMoreTime)
- || (ExactMaxTime && t >= ExactMaxTime)
- || (Iteration >= 3 && MaxNodes && TM.nodes_searched() >= MaxNodes))
- AbortSearch = true;
+ return s.str();
}
- // ponderhit() is called when the program is pondering (i.e. thinking while
- // it's the opponent's turn to move) in order to let the engine know that
- // it correctly predicted the opponent's move.
-
- void ponderhit() {
+ // speed_to_uci() returns a string with time stats of current search suitable
+ // to be sent to UCI gui.
- int t = current_search_time();
- PonderSearch = false;
+ string speed_to_uci(int64_t nodes) {
- bool stillAtFirstMove = FirstRootMove
- && !AspirationFailLow
- && t > MaxSearchTime + ExtraSearchTime;
+ std::stringstream s;
+ int t = elapsed_time();
- bool noMoreTime = t > AbsoluteMaxSearchTime
- || stillAtFirstMove;
+ s << " nodes " << nodes
+ << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
+ << " time " << t;
- if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit))
- AbortSearch = true;
+ return s.str();
}
- // init_ss_array() does a fast reset of the first entries of a SearchStack array
-
- void init_ss_array(SearchStack* ss) {
-
- for (int i = 0; i < 3; i++, ss++)
- {
- ss->init(i);
- ss->initKillers();
- ss->excludedMove = MOVE_NONE;
- }
- }
-
+ // pv_to_uci() returns a string with information on the current PV line
+ // formatted according to UCI specification.
- // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
- // while the program is pondering. The point is to work around a wrinkle in
- // the UCI protocol: When pondering, the engine is not allowed to give a
- // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
- // We simply wait here until one of these commands is sent, and return,
- // after which the bestmove and pondermove will be printed (in id_loop()).
+ string pv_to_uci(const Move pv[], int pvNum, bool chess960) {
- void wait_for_stop_or_ponderhit() {
+ std::stringstream s;
- std::string command;
+ s << " multipv " << pvNum << " pv " << set960(chess960);
- while (true)
- {
- if (!std::getline(std::cin, command))
- command = "quit";
+ for ( ; *pv != MOVE_NONE; pv++)
+ s << *pv << " ";
- if (command == "quit")
- {
- Quit = true;
- break;
- }
- else if (command == "ponderhit" || command == "stop")
- break;
- }
+ return s.str();
}
- // print_pv_info() prints to standard output and eventually to log file information on
- // the current PV line. It is called at each iteration or after a new pv is found.
-
- void print_pv_info(const Position& pos, SearchStack* ss, Value alpha, Value beta, Value value) {
+ // depth_to_uci() returns a string with information on the current depth and
+ // seldepth formatted according to UCI specification.
- cout << "info depth " << Iteration
- << " score " << value_to_string(value)
- << ((value >= beta) ? " lowerbound" :
- ((value <= alpha)? " upperbound" : ""))
- << " time " << current_search_time()
- << " nodes " << TM.nodes_searched()
- << " nps " << nps()
- << " pv ";
+ string depth_to_uci(Depth depth) {
- for (int j = 0; ss->pv[j] != MOVE_NONE && j < PLY_MAX; j++)
- cout << ss->pv[j] << " ";
+ std::stringstream s;
- cout << endl;
+ // Retrieve max searched depth among threads
+ int selDepth = 0;
+ for (int i = 0; i < Threads.size(); i++)
+ if (Threads[i].maxPly > selDepth)
+ selDepth = Threads[i].maxPly;
- if (UseLogFile)
- {
- ValueType type = (value >= beta ? VALUE_TYPE_LOWER
- : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT));
+ s << " depth " << depth / ONE_PLY << " seldepth " << selDepth;
- LogFile << pretty_pv(pos, current_search_time(), Iteration,
- TM.nodes_searched(), value, type, ss->pv) << endl;
- }
+ return s.str();
}
+ string time_to_string(int millisecs) {
- // init_thread() is the function which is called when a new thread is
- // launched. It simply calls the idle_loop() function with the supplied
- // threadID. There are two versions of this function; one for POSIX
- // threads and one for Windows threads.
+ const int MSecMinute = 1000 * 60;
+ const int MSecHour = 1000 * 60 * 60;
-#if !defined(_MSC_VER)
+ int hours = millisecs / MSecHour;
+ int minutes = (millisecs % MSecHour) / MSecMinute;
+ int seconds = ((millisecs % MSecHour) % MSecMinute) / 1000;
- void* init_thread(void *threadID) {
+ std::stringstream s;
- TM.idle_loop(*(int*)threadID, NULL);
- return NULL;
- }
-
-#else
-
- DWORD WINAPI init_thread(LPVOID threadID) {
+ if (hours)
+ s << hours << ':';
- TM.idle_loop(*(int*)threadID, NULL);
- return 0;
+ s << std::setfill('0') << std::setw(2) << minutes << ':' << std::setw(2) << seconds;
+ return s.str();
}
-#endif
+ string score_to_string(Value v) {
+ std::stringstream s;
- /// The ThreadsManager class
-
- // resetNodeCounters(), resetBetaCounters(), searched_nodes() and
- // get_beta_counters() are getters/setters for the per thread
- // counters used to sort the moves at root.
-
- void ThreadsManager::resetNodeCounters() {
+ if (v >= VALUE_MATE_IN_PLY_MAX)
+ s << "#" << (VALUE_MATE - v + 1) / 2;
+ else if (v <= VALUE_MATED_IN_PLY_MAX)
+ s << "-#" << (VALUE_MATE + v) / 2;
+ else
+ s << std::setprecision(2) << std::fixed << std::showpos << float(v) / PawnValueMidgame;
- for (int i = 0; i < MAX_THREADS; i++)
- threads[i].nodes = 0ULL;
+ return s.str();
}
- void ThreadsManager::resetBetaCounters() {
- for (int i = 0; i < MAX_THREADS; i++)
- threads[i].betaCutOffs[WHITE] = threads[i].betaCutOffs[BLACK] = 0ULL;
- }
-
- int64_t ThreadsManager::nodes_searched() const {
+ // pretty_pv() creates a human-readable string from a position and a PV.
+ // It is used to write search information to the log file (which is created
+ // when the UCI parameter "Use Search Log" is "true").
- int64_t result = 0ULL;
- for (int i = 0; i < ActiveThreads; i++)
- result += threads[i].nodes;
+ string pretty_pv(Position& pos, int depth, Value value, int time, Move pv[]) {
- return result;
- }
+ const int64_t K = 1000;
+ const int64_t M = 1000000;
+ const int startColumn = 28;
+ const size_t maxLength = 80 - startColumn;
- void ThreadsManager::get_beta_counters(Color us, int64_t& our, int64_t& their) const {
+ StateInfo state[PLY_MAX_PLUS_2], *st = state;
+ Move* m = pv;
+ string san;
+ std::stringstream s;
+ size_t length = 0;
- our = their = 0UL;
- for (int i = 0; i < MAX_THREADS; i++)
- {
- our += threads[i].betaCutOffs[us];
- their += threads[i].betaCutOffs[opposite_color(us)];
- }
- }
+ // First print depth, score, time and searched nodes...
+ s << set960(pos.is_chess960())
+ << std::setw(2) << depth
+ << std::setw(8) << score_to_string(value)
+ << std::setw(8) << time_to_string(time);
+ if (pos.nodes_searched() < M)
+ s << std::setw(8) << pos.nodes_searched() / 1 << " ";
+ else if (pos.nodes_searched() < K * M)
+ s << std::setw(7) << pos.nodes_searched() / K << "K ";
+ else
+ s << std::setw(7) << pos.nodes_searched() / M << "M ";
- // idle_loop() is where the threads are parked when they have no work to do.
- // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
- // object for which the current thread is the master.
-
- void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
-
- assert(threadID >= 0 && threadID < MAX_THREADS);
-
- while (true)
+ // ...then print the full PV line in short algebraic notation
+ while (*m != MOVE_NONE)
{
- // Slave threads can exit as soon as AllThreadsShouldExit raises,
- // master should exit as last one.
- if (AllThreadsShouldExit)
- {
- assert(!sp);
- threads[threadID].state = THREAD_TERMINATED;
- return;
- }
+ san = move_to_san(pos, *m);
+ length += san.length() + 1;
- // If we are not thinking, wait for a condition to be signaled
- // instead of wasting CPU time polling for work.
- while (AllThreadsShouldSleep || threadID >= ActiveThreads)
+ if (length > maxLength)
{
- assert(!sp);
- assert(threadID != 0);
- threads[threadID].state = THREAD_SLEEPING;
-
-#if !defined(_MSC_VER)
- lock_grab(&WaitLock);
- if (AllThreadsShouldSleep || threadID >= ActiveThreads)
- pthread_cond_wait(&WaitCond, &WaitLock);
- lock_release(&WaitLock);
-#else
- WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
-#endif
+ length = san.length() + 1;
+ s << "\n" + string(startColumn, ' ');
}
+ s << san << ' ';
- // If thread has just woken up, mark it as available
- if (threads[threadID].state == THREAD_SLEEPING)
- threads[threadID].state = THREAD_AVAILABLE;
-
- // If this thread has been assigned work, launch a search
- if (threads[threadID].state == THREAD_WORKISWAITING)
- {
- assert(!AllThreadsShouldExit && !AllThreadsShouldSleep);
-
- threads[threadID].state = THREAD_SEARCHING;
-
- if (threads[threadID].splitPoint->pvNode)
- sp_search<PV>(threads[threadID].splitPoint, threadID);
- else
- sp_search<NonPV>(threads[threadID].splitPoint, threadID);
-
- assert(threads[threadID].state == THREAD_SEARCHING);
-
- threads[threadID].state = THREAD_AVAILABLE;
- }
-
- // If this thread is the master of a split point and all slaves have
- // finished their work at this split point, return from the idle loop.
- int i = 0;
- for ( ; sp && i < ActiveThreads && !sp->slaves[i]; i++) {}
-
- if (i == ActiveThreads)
- {
- // Because sp->slaves[] is reset under lock protection,
- // be sure sp->lock has been released before to return.
- lock_grab(&(sp->lock));
- lock_release(&(sp->lock));
-
- assert(threads[threadID].state == THREAD_AVAILABLE);
-
- threads[threadID].state = THREAD_SEARCHING;
- return;
- }
+ pos.do_move(*m++, *st++);
}
- }
-
-
- // init_threads() is called during startup. It launches all helper threads,
- // and initializes the split point stack and the global locks and condition
- // objects.
- void ThreadsManager::init_threads() {
+ // Restore original position before to leave
+ while (m != pv) pos.undo_move(*--m);
- volatile int i;
- bool ok;
+ return s.str();
+ }
-#if !defined(_MSC_VER)
- pthread_t pthread[1];
-#endif
- // Initialize global locks
- lock_init(&MPLock, NULL);
- lock_init(&WaitLock, NULL);
+ // When playing with strength handicap choose best move among the MultiPV set
+ // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
-#if !defined(_MSC_VER)
- pthread_cond_init(&WaitCond, NULL);
-#else
- for (i = 0; i < MAX_THREADS; i++)
- SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
-#endif
+ void do_skill_level(Move* best, Move* ponder) {
- // Initialize SplitPointStack locks
- for (i = 0; i < MAX_THREADS; i++)
- for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++)
- lock_init(&(SplitPointStack[i][j].lock), NULL);
+ assert(MultiPV > 1);
- // Will be set just before program exits to properly end the threads
- AllThreadsShouldExit = false;
+ static RKISS rk;
- // Threads will be put to sleep as soon as created
- AllThreadsShouldSleep = true;
+ // Rml list is already sorted by score in descending order
+ int s;
+ size_t size = std::min(MultiPV, Rml.size());
+ int max_s = -VALUE_INFINITE;
+ int max = Rml[0].score;
+ int var = std::min(max - Rml[size - 1].score, int(PawnValueMidgame));
+ int wk = 120 - 2 * SkillLevel;
- // All threads except the main thread should be initialized to THREAD_AVAILABLE
- ActiveThreads = 1;
- threads[0].state = THREAD_SEARCHING;
- for (i = 1; i < MAX_THREADS; i++)
- threads[i].state = THREAD_AVAILABLE;
+ // PRNG sequence should be non deterministic
+ for (int i = abs(get_system_time() % 50); i > 0; i--)
+ rk.rand<unsigned>();
- // Launch the helper threads
- for (i = 1; i < MAX_THREADS; i++)
+ // Choose best move. For each move's score we add two terms both dependent
+ // on wk, one deterministic and bigger for weaker moves, and one random,
+ // then we choose the move with the resulting highest score.
+ for (size_t i = 0; i < size; i++)
{
+ s = Rml[i].score;
+
+ // Don't allow crazy blunders even at very low skills
+ if (i > 0 && Rml[i-1].score > s + EasyMoveMargin)
+ break;
-#if !defined(_MSC_VER)
- ok = (pthread_create(pthread, NULL, init_thread, (void*)(&i)) == 0);
-#else
- ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, NULL) != NULL);
-#endif
+ // This is our magical formula
+ s += ((max - s) * wk + var * (rk.rand<unsigned>() % wk)) / 128;
- if (!ok)
+ if (s > max_s)
{
- cout << "Failed to create thread number " << i << endl;
- Application::exit_with_failure();
+ max_s = s;
+ *best = Rml[i].pv[0];
+ *ponder = Rml[i].pv[1];
}
-
- // Wait until the thread has finished launching and is gone to sleep
- while (threads[i].state != THREAD_SLEEPING) {}
}
}
- // exit_threads() is called when the program exits. It makes all the
- // helper threads exit cleanly.
-
- void ThreadsManager::exit_threads() {
-
- ActiveThreads = MAX_THREADS; // HACK
- AllThreadsShouldSleep = true; // HACK
- wake_sleeping_threads();
-
- // This makes the threads to exit idle_loop()
- AllThreadsShouldExit = true;
-
- // Wait for thread termination
- for (int i = 1; i < MAX_THREADS; i++)
- while (threads[i].state != THREAD_TERMINATED) {}
-
- // Now we can safely destroy the locks
- for (int i = 0; i < MAX_THREADS; i++)
- for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++)
- lock_destroy(&(SplitPointStack[i][j].lock));
-
- lock_destroy(&WaitLock);
- lock_destroy(&MPLock);
- }
-
+ /// RootMove and RootMoveList method's definitions
- // thread_should_stop() checks whether the thread should stop its search.
- // This can happen if a beta cutoff has occurred in the thread's currently
- // active split point, or in some ancestor of the current split point.
+ void RootMoveList::init(Position& pos, Move rootMoves[]) {
- bool ThreadsManager::thread_should_stop(int threadID) const {
+ Move* sm;
+ bestMoveChanges = 0;
+ clear();
- assert(threadID >= 0 && threadID < ActiveThreads);
+ // Generate all legal moves and add them to RootMoveList
+ for (MoveList<MV_LEGAL> ml(pos); !ml.end(); ++ml)
+ {
+ // If we have a rootMoves[] list then verify the move
+ // is in the list before to add it.
+ for (sm = rootMoves; *sm && *sm != ml.move(); sm++) {}
- SplitPoint* sp;
+ if (sm != rootMoves && *sm != ml.move())
+ continue;
- for (sp = threads[threadID].splitPoint; sp && !sp->stopRequest; sp = sp->parent) {}
- return sp != NULL;
+ RootMove rm;
+ rm.pv.push_back(ml.move());
+ rm.pv.push_back(MOVE_NONE);
+ rm.score = rm.prevScore = -VALUE_INFINITE;
+ rm.nodes = 0;
+ push_back(rm);
+ }
}
+ RootMove* RootMoveList::find(const Move& m, int startIndex) {
- // thread_is_available() checks whether the thread with threadID "slave" is
- // available to help the thread with threadID "master" at a split point. An
- // obvious requirement is that "slave" must be idle. With more than two
- // threads, this is not by itself sufficient: If "slave" is the master of
- // some active split point, it is only available as a slave to the other
- // threads which are busy searching the split point at the top of "slave"'s
- // split point stack (the "helpful master concept" in YBWC terminology).
-
- bool ThreadsManager::thread_is_available(int slave, int master) const {
-
- assert(slave >= 0 && slave < ActiveThreads);
- assert(master >= 0 && master < ActiveThreads);
- assert(ActiveThreads > 1);
-
- if (threads[slave].state != THREAD_AVAILABLE || slave == master)
- return false;
+ for (size_t i = startIndex; i < size(); i++)
+ if ((*this)[i].pv[0] == m)
+ return &(*this)[i];
- // Make a local copy to be sure doesn't change under our feet
- int localActiveSplitPoints = threads[slave].activeSplitPoints;
-
- if (localActiveSplitPoints == 0)
- // No active split points means that the thread is available as
- // a slave for any other thread.
- return true;
-
- if (ActiveThreads == 2)
- return true;
-
- // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
- // that is known to be > 0, instead of threads[slave].activeSplitPoints that
- // could have been set to 0 by another thread leading to an out of bound access.
- if (SplitPointStack[slave][localActiveSplitPoints - 1].slaves[master])
- return true;
-
- return false;
+ return NULL;
}
- // available_thread_exists() tries to find an idle thread which is available as
- // a slave for the thread with threadID "master".
+ // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
+ // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
+ // allow to always have a ponder move even when we fail high at root and also a
+ // long PV to print that is important for position analysis.
- bool ThreadsManager::available_thread_exists(int master) const {
+ void RootMove::extract_pv_from_tt(Position& pos) {
- assert(master >= 0 && master < ActiveThreads);
- assert(ActiveThreads > 1);
+ StateInfo state[PLY_MAX_PLUS_2], *st = state;
+ TTEntry* tte;
+ int ply = 1;
+ Move m = pv[0];
- for (int i = 0; i < ActiveThreads; i++)
- if (thread_is_available(i, master))
- return true;
+ assert(m != MOVE_NONE && pos.is_pseudo_legal(m));
- return false;
- }
+ pv.clear();
+ pv.push_back(m);
+ pos.do_move(m, *st++);
-
- // split() does the actual work of distributing the work at a node between
- // several available threads. If it does not succeed in splitting the
- // node (because no idle threads are available, or because we have no unused
- // split point objects), the function immediately returns. If splitting is
- // possible, a SplitPoint object is initialized with all the data that must be
- // copied to the helper threads and we tell our helper threads that they have
- // been assigned work. This will cause them to instantly leave their idle loops
- // and call sp_search(). When all threads have returned from sp_search() then
- // split() returns.
-
- template <bool Fake>
- void ThreadsManager::split(const Position& p, SearchStack* ss, Value* alpha, const Value beta,
- Value* bestValue, Depth depth, bool mateThreat, int* moveCount,
- MovePicker* mp, int master, bool pvNode) {
- assert(p.is_ok());
- assert(*bestValue >= -VALUE_INFINITE);
- assert(*bestValue <= *alpha);
- assert(*alpha < beta);
- assert(beta <= VALUE_INFINITE);
- assert(depth > Depth(0));
- assert(master >= 0 && master < ActiveThreads);
- assert(ActiveThreads > 1);
-
- lock_grab(&MPLock);
-
- // If no other thread is available to help us, or if we have too many
- // active split points, don't split.
- if ( !available_thread_exists(master)
- || threads[master].activeSplitPoints >= ACTIVE_SPLIT_POINTS_MAX)
+ while ( (tte = TT.probe(pos.get_key())) != NULL
+ && tte->move() != MOVE_NONE
+ && pos.is_pseudo_legal(tte->move())
+ && pos.pl_move_is_legal(tte->move(), pos.pinned_pieces())
+ && ply < PLY_MAX
+ && (!pos.is_draw<false>() || ply < 2))
{
- lock_release(&MPLock);
- return;
+ pv.push_back(tte->move());
+ pos.do_move(tte->move(), *st++);
+ ply++;
}
+ pv.push_back(MOVE_NONE);
- // Pick the next available split point object from the split point stack
- SplitPoint* splitPoint = &SplitPointStack[master][threads[master].activeSplitPoints];
-
- // Initialize the split point object
- splitPoint->parent = threads[master].splitPoint;
- splitPoint->stopRequest = false;
- splitPoint->depth = depth;
- splitPoint->mateThreat = mateThreat;
- splitPoint->alpha = *alpha;
- splitPoint->beta = beta;
- splitPoint->pvNode = pvNode;
- splitPoint->bestValue = *bestValue;
- splitPoint->mp = mp;
- splitPoint->moveCount = *moveCount;
- splitPoint->pos = &p;
- splitPoint->parentSstack = ss;
- for (int i = 0; i < ActiveThreads; i++)
- splitPoint->slaves[i] = 0;
-
- threads[master].splitPoint = splitPoint;
- threads[master].activeSplitPoints++;
-
- // If we are here it means we are not available
- assert(threads[master].state != THREAD_AVAILABLE);
-
- int workersCnt = 1; // At least the master is included
-
- // Allocate available threads setting state to THREAD_BOOKED
- for (int i = 0; !Fake && i < ActiveThreads && workersCnt < MaxThreadsPerSplitPoint; i++)
- if (thread_is_available(i, master))
- {
- threads[i].state = THREAD_BOOKED;
- threads[i].splitPoint = splitPoint;
- splitPoint->slaves[i] = 1;
- workersCnt++;
- }
-
- assert(Fake || workersCnt > 1);
-
- // We can release the lock because slave threads are already booked and master is not available
- lock_release(&MPLock);
-
- // Tell the threads that they have work to do. This will make them leave
- // their idle loop. But before copy search stack tail for each thread.
- for (int i = 0; i < ActiveThreads; i++)
- if (i == master || splitPoint->slaves[i])
- {
- memcpy(splitPoint->sstack[i], ss - 1, 4 * sizeof(SearchStack));
-
- assert(i == master || threads[i].state == THREAD_BOOKED);
-
- threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
- }
-
- // Everything is set up. The master thread enters the idle loop, from
- // which it will instantly launch a search, because its state is
- // THREAD_WORKISWAITING. We send the split point as a second parameter to the
- // idle loop, which means that the main thread will return from the idle
- // loop when all threads have finished their work at this split point.
- idle_loop(master, splitPoint);
-
- // We have returned from the idle loop, which means that all threads are
- // finished. Update alpha and bestValue, and return.
- lock_grab(&MPLock);
-
- *alpha = splitPoint->alpha;
- *bestValue = splitPoint->bestValue;
- threads[master].activeSplitPoints--;
- threads[master].splitPoint = splitPoint->parent;
-
- lock_release(&MPLock);
+ do pos.undo_move(pv[--ply]); while (ply);
}
- // wake_sleeping_threads() wakes up all sleeping threads when it is time
- // to start a new search from the root.
+ // insert_pv_in_tt() is called at the end of a search iteration, and inserts
+ // the PV back into the TT. This makes sure the old PV moves are searched
+ // first, even if the old TT entries have been overwritten.
- void ThreadsManager::wake_sleeping_threads() {
+ void RootMove::insert_pv_in_tt(Position& pos) {
- assert(AllThreadsShouldSleep);
- assert(ActiveThreads > 0);
+ StateInfo state[PLY_MAX_PLUS_2], *st = state;
+ TTEntry* tte;
+ Key k;
+ Value v, m = VALUE_NONE;
+ int ply = 0;
- AllThreadsShouldSleep = false;
+ assert(pv[0] != MOVE_NONE && pos.is_pseudo_legal(pv[0]));
- if (ActiveThreads == 1)
- return;
-
-#if !defined(_MSC_VER)
- pthread_mutex_lock(&WaitLock);
- pthread_cond_broadcast(&WaitCond);
- pthread_mutex_unlock(&WaitLock);
-#else
- for (int i = 1; i < MAX_THREADS; i++)
- SetEvent(SitIdleEvent[i]);
-#endif
-
- }
+ do {
+ k = pos.get_key();
+ tte = TT.probe(k);
+ // Don't overwrite existing correct entries
+ if (!tte || tte->move() != pv[ply])
+ {
+ v = (pos.in_check() ? VALUE_NONE : evaluate(pos, m));
+ TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
+ }
+ pos.do_move(pv[ply], *st++);
- // put_threads_to_sleep() makes all the threads go to sleep just before
- // to leave think(), at the end of the search. Threads should have already
- // finished the job and should be idle.
-
- void ThreadsManager::put_threads_to_sleep() {
-
- assert(!AllThreadsShouldSleep);
+ } while (pv[++ply] != MOVE_NONE);
- // This makes the threads to go to sleep
- AllThreadsShouldSleep = true;
+ do pos.undo_move(pv[--ply]); while (ply);
}
- /// The RootMoveList class
+} // namespace
- // RootMoveList c'tor
- RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
+// Thread::idle_loop() is where the thread is parked when it has no work to do.
+// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object
+// for which the thread is the master.
- SearchStack ss[PLY_MAX_PLUS_2];
- MoveStack mlist[MaxRootMoves];
- StateInfo st;
- bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
+void Thread::idle_loop(SplitPoint* sp) {
- // Generate all legal moves
- MoveStack* last = generate_moves(pos, mlist);
+ while (true)
+ {
+ // If we are not searching, wait for a condition to be signaled
+ // instead of wasting CPU time polling for work.
+ while ( do_sleep
+ || do_terminate
+ || (Threads.use_sleeping_threads() && !is_searching))
+ {
+ assert((!sp && threadID) || Threads.use_sleeping_threads());
- // Add each move to the moves[] array
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- bool includeMove = includeAllMoves;
+ // Slave thread should exit as soon as do_terminate flag raises
+ if (do_terminate)
+ {
+ assert(!sp);
+ return;
+ }
- for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
- includeMove = (searchMoves[k] == cur->move);
+ // Grab the lock to avoid races with Thread::wake_up()
+ lock_grab(&sleepLock);
- if (!includeMove)
- continue;
+ // If we are master and all slaves have finished don't go to sleep
+ if (sp && Threads.split_point_finished(sp))
+ {
+ lock_release(&sleepLock);
+ break;
+ }
- // Find a quick score for the move
- init_ss_array(ss);
- pos.do_move(cur->move, st);
- moves[count].move = cur->move;
- moves[count].score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 0);
- moves[count].pv[0] = cur->move;
- moves[count].pv[1] = MOVE_NONE;
- pos.undo_move(cur->move);
- count++;
- }
- sort();
- }
+ // Do sleep after retesting sleep conditions under lock protection, in
+ // particular we need to avoid a deadlock in case a master thread has,
+ // in the meanwhile, allocated us and sent the wake_up() call before we
+ // had the chance to grab the lock.
+ if (do_sleep || !is_searching)
+ cond_wait(&sleepCond, &sleepLock);
+ lock_release(&sleepLock);
+ }
- // RootMoveList simple methods definitions
+ // If this thread has been assigned work, launch a search
+ if (is_searching)
+ {
+ assert(!do_terminate);
+
+ // Copy split point position and search stack and call search()
+ Stack ss[PLY_MAX_PLUS_2];
+ SplitPoint* tsp = splitPoint;
+ Position pos(*tsp->pos, threadID);
+
+ memcpy(ss, tsp->ss - 1, 4 * sizeof(Stack));
+ (ss+1)->sp = tsp;
+
+ if (tsp->nodeType == Root)
+ search<SplitPointRoot>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ else if (tsp->nodeType == PV)
+ search<SplitPointPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ else if (tsp->nodeType == NonPV)
+ search<SplitPointNonPV>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ else
+ assert(false);
- void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
+ assert(is_searching);
- moves[moveNum].nodes = nodes;
- moves[moveNum].cumulativeNodes += nodes;
- }
+ is_searching = false;
- void RootMoveList::set_beta_counters(int moveNum, int64_t our, int64_t their) {
+ // Wake up master thread so to allow it to return from the idle loop in
+ // case we are the last slave of the split point.
+ if ( Threads.use_sleeping_threads()
+ && threadID != tsp->master
+ && !Threads[tsp->master].is_searching)
+ Threads[tsp->master].wake_up();
+ }
- moves[moveNum].ourBeta = our;
- moves[moveNum].theirBeta = their;
+ // If this thread is the master of a split point and all slaves have
+ // finished their work at this split point, return from the idle loop.
+ if (sp && Threads.split_point_finished(sp))
+ {
+ // Because sp->is_slave[] is reset under lock protection,
+ // be sure sp->lock has been released before to return.
+ lock_grab(&(sp->lock));
+ lock_release(&(sp->lock));
+ return;
+ }
}
+}
- void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
-
- int j;
-
- for (j = 0; pv[j] != MOVE_NONE; j++)
- moves[moveNum].pv[j] = pv[j];
- moves[moveNum].pv[j] = MOVE_NONE;
- }
+// do_timer_event() is called by the timer thread when the timer triggers
+void do_timer_event() {
- // RootMoveList::sort() sorts the root move list at the beginning of a new
- // iteration.
+ static int lastInfoTime;
+ int e = elapsed_time();
- void RootMoveList::sort() {
+ // Print debug information every one second
+ if (!lastInfoTime || get_system_time() - lastInfoTime >= 1000)
+ {
+ lastInfoTime = get_system_time();
- sort_multipv(count - 1); // Sort all items
+ dbg_print_mean();
+ dbg_print_hit_rate();
}
+ // Should we stop the search?
+ if (Limits.ponder)
+ return;
- // RootMoveList::sort_multipv() sorts the first few moves in the root move
- // list by their scores and depths. It is used to order the different PVs
- // correctly in MultiPV mode.
-
- void RootMoveList::sort_multipv(int n) {
+ bool stillAtFirstMove = Signals.firstRootMove
+ && !Signals.failedLowAtRoot
+ && e > TimeMgr.available_time();
- int i,j;
+ bool noMoreTime = e > TimeMgr.maximum_time()
+ || stillAtFirstMove;
- for (i = 1; i <= n; i++)
- {
- RootMove rm = moves[i];
- for (j = i; j > 0 && moves[j - 1] < rm; j--)
- moves[j] = moves[j - 1];
-
- moves[j] = rm;
- }
- }
-
-} // namspace
+ if ( (Limits.useTimeManagement() && noMoreTime)
+ || (Limits.maxTime && e >= Limits.maxTime)
+ /* missing nodes limit */ ) // FIXME
+ Signals.stop = true;
+}