along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
#include <cmath>
#include <cstring>
#include "evaluate.h"
#include "history.h"
#include "misc.h"
+#include "move.h"
#include "movegen.h"
#include "movepick.h"
#include "lock.h"
-#include "san.h"
#include "search.h"
#include "timeman.h"
#include "thread.h"
using std::cout;
using std::endl;
-////
-//// Local definitions
-////
-
namespace {
- // Types
+ // Different node types, used as template parameter
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;
- // Fast lookup table of sliding pieces indexed by Piece
+ // 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]; }
- // 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.
+ // ThreadsManager class is used to handle all the threads related stuff like init,
+ // starting, parking and, the most important, launching a slave thread at a split
+ // point. All the access to shared thread data is done through this class.
class ThreadsManager {
/* As long as the single ThreadsManager object is defined as a global we don't
};
- // RootMove struct is used for moves at the root at the tree. For each root
+ // RootMove struct is used for moves at the root of the tree. For each root
// move, we store two scores, a node count, and a PV (really a refutation
// in the case of moves which fail low). Value pv_score is normally set at
// -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
// 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 an higher pv_score, or if it has
- // equal pv_score but m1 has the higher non_pv_score. In this
- // way we are guaranteed that PV moves are always sorted as first.
+ // equal pv_score but m1 has the higher non_pv_score. In this way
+ // we are guaranteed that PV moves are always sorted as first.
bool operator<(const RootMove& m) const {
return pv_score != m.pv_score ? pv_score < m.pv_score
: non_pv_score < m.non_pv_score;
void extract_pv_from_tt(Position& pos);
void insert_pv_in_tt(Position& pos);
- std::string pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine = 0);
+ std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvIdx);
int64_t nodes;
Value pv_score;
};
- // RootMoveList struct is essentially a std::vector<> of RootMove objects,
+ // RootMoveList struct is just a std::vector<> of RootMove objects,
// with an handful of methods above the standard ones.
struct RootMoveList : public std::vector<RootMove> {
typedef std::vector<RootMove> Base;
- RootMoveList(Position& pos, Move searchMoves[]);
- void set_non_pv_scores(const Position& pos);
-
+ void init(Position& pos, Move searchMoves[]);
void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
+
+ int bestMoveChanges;
};
+ // 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 use it to properly format castling moves.
+ // operator<<() that will read it to properly format castling moves.
enum set960 {};
- std::ostream& operator<< (std::ostream& os, const set960& m) {
+ std::ostream& operator<< (std::ostream& os, const set960& f) {
- os.iword(0) = int(m);
+ os.iword(0) = int(f);
return os;
}
// 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];
+ Depth CheckExtension[2], PawnPushTo7thExtension[2], PassedPawnExtension[2];
+ Depth PawnEndgameExtension[2], MateThreatExtension[2];
// Minimum depth for use of singular extension
const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* 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
// Futility margin for quiescence search
const Value FutilityMarginQS = Value(0x80);
- // Futility lookup tables (initialized at startup) and their getter functions
+ // Futility lookup tables (initialized at startup) and their access functions
Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
int FutilityMoveCountArray[32]; // [depth]
template <NodeType PV>
inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
- // Common adjustments
-
- // Search depth at iteration 1
- const Depth InitialDepth = ONE_PLY;
-
// Easy move margin. An easy move candidate must be at least this much
// better than the second best move.
const Value EasyMoveMargin = Value(0x200);
/// Namespace variables
- // Book object
+ // Book
Book OpeningBook;
- // 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];
-
- // Search window management
- int AspirationDelta;
+ // Root move list
+ RootMoveList Rml;
// MultiPV mode
- int MultiPV;
+ int MultiPV, UCIMultiPV;
- // Time managment variables
+ // Time management variables
int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
- bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit;
- bool FirstRootMove, AbortSearch, Quit, AspirationFailLow;
+ bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
+ bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
TimeManager TimeMgr;
// Log file
bool UseLogFile;
std::ofstream LogFile;
- // Multi-threads manager object
+ // Skill level adjustment
+ int SkillLevel;
+ bool SkillLevelEnabled;
+ RKISS RK;
+
+ // Multi-threads manager
ThreadsManager ThreadsMgr;
// 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.
+ bool SendSearchedNodes;
int NodesSincePoll;
int NodesBetweenPolls = 30000;
// History table
History H;
+
/// Local functions
Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
- Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
- template <NodeType PvNode, bool SpNode>
+ template <NodeType PvNode, bool SpNode, bool Root>
Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
template <NodeType PvNode>
template <NodeType PvNode>
inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
-
return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
- : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
+ return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
+ : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
}
template <NodeType PvNode>
- Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
+ Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous);
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);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
bool ok_to_use_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);
+ void do_skill_level(Move* best, Move* ponder);
int current_search_time();
std::string value_to_uci(Value v);
- int nps(const Position& pos);
+ std::string speed_to_uci(int64_t nodes);
void poll(const Position& pos);
- void ponderhit();
void wait_for_stop_or_ponderhit();
- void init_ss_array(SearchStack* ss, int size);
#if !defined(_MSC_VER)
void* init_thread(void* threadID);
DWORD WINAPI init_thread(LPVOID threadID);
#endif
-}
+ // MovePickerExt is an extended MovePicker used to choose at compile time
+ // the proper move source according to the type of node.
+ template<bool SpNode, bool Root> struct MovePickerExt;
+
+ // In Root nodes use RootMoveList as source. Score and sort the root moves
+ // before to search them.
+ template<> struct MovePickerExt<false, true> : public MovePicker {
+
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
+ Move move;
+ Value score = VALUE_ZERO;
-////
-//// Functions
-////
+ // Score root moves using standard ordering used in main search, the moves
+ // are scored according to the order in which they are returned by MovePicker.
+ // This is the second order score that is used to compare the moves when
+ // the first orders pv_score of both moves are equal.
+ while ((move = MovePicker::get_next_move()) != MOVE_NONE)
+ for (rm = Rml.begin(); rm != Rml.end(); ++rm)
+ if (rm->pv[0] == move)
+ {
+ rm->non_pv_score = score--;
+ break;
+ }
-/// init_threads(), exit_threads() and nodes_searched() are helpers to
-/// give accessibility to some TM methods from outside of current file.
+ Rml.sort();
+ rm = Rml.begin();
+ }
-void init_threads() { ThreadsMgr.init_threads(); }
-void exit_threads() { ThreadsMgr.exit_threads(); }
+ Move get_next_move() {
+ if (!firstCall)
+ ++rm;
+ else
+ firstCall = false;
-/// init_search() is called during startup. It initializes various lookup tables
+ return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
+ }
-void init_search() {
+ RootMoveList::iterator rm;
+ bool firstCall;
+ };
+
+ // In SpNodes use split point's shared MovePicker object as move source
+ template<> struct MovePickerExt<true, false> : public MovePicker {
+
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
+
+ Move get_next_move() { return mp->get_next_move(); }
+
+ RootMoveList::iterator rm; // Dummy, needed to compile
+ MovePicker* mp;
+ };
+
+ // Default case, create and use a MovePicker object as source
+ template<> struct MovePickerExt<false, false> : public MovePicker {
+
+ MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
+ : MovePicker(p, ttm, d, h, ss, b) {}
+
+ RootMoveList::iterator rm; // Dummy, needed to compile
+ };
+
+} // namespace
+
+
+/// init_threads() is called during startup. It initializes various lookup tables
+/// and creates and launches search threads.
+
+void init_threads() {
int d; // depth (ONE_PLY == 2)
int hd; // half depth (ONE_PLY == 1)
// Init futility move count array
for (d = 0; d < 32; d++)
FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
+
+ // Create and startup threads
+ ThreadsMgr.init_threads();
}
-/// 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.
+/// exit_threads() is a trampoline to access ThreadsMgr from outside of current file
+void exit_threads() { ThreadsMgr.exit_threads(); }
-int perft(Position& pos, Depth depth)
-{
- MoveStack mlist[MOVES_MAX];
- StateInfo st;
- Move m;
- int sum = 0;
- // Generate all legal moves
- MoveStack* last = generate_moves(pos, mlist);
+/// perft() is our utility to verify move generation. All the legal moves up to
+/// given depth are generated and counted and the sum returned.
- // 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 int(last - mlist);
+int64_t perft(Position& pos, Depth depth) {
- // Loop through all legal moves
- CheckInfo ci(pos);
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- m = cur->move;
- pos.do_move(m, st, ci, pos.move_is_check(m, ci));
- sum += perft(pos, depth - ONE_PLY);
- pos.undo_move(m);
- }
- return sum;
+ MoveStack mlist[MOVES_MAX];
+ StateInfo st;
+ Move m;
+ int64_t sum = 0;
+
+ // Generate all legal moves
+ MoveStack* last = generate<MV_LEGAL>(pos, mlist);
+
+ // 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 int(last - mlist);
+
+ // Loop through all legal moves
+ CheckInfo ci(pos);
+ for (MoveStack* cur = mlist; cur != last; cur++)
+ {
+ m = cur->move;
+ pos.do_move(m, st, ci, pos.move_is_check(m, ci));
+ sum += perft(pos, depth - ONE_PLY);
+ pos.undo_move(m);
+ }
+ return sum;
}
/// 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.
+/// the program receives the UCI 'go' command. It initializes various global
+/// variables, and calls id_loop(). It returns false when a quit command is
+/// received during the search.
bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
- // Initialize global search variables
- StopOnPonderhit = AbortSearch = Quit = AspirationFailLow = false;
+ // Initialize global search-related variables
+ StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
NodesSincePoll = 0;
SearchStartTime = get_system_time();
ExactMaxTime = maxTime;
MaxDepth = maxDepth;
MaxNodes = maxNodes;
InfiniteSearch = infinite;
- PonderSearch = ponder;
+ Pondering = ponder;
UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
// Look for a book move, only during games, not tests
if (UseTimeManagement && Options["OwnBook"].value<bool>())
{
- if (Options["Book File"].value<std::string>() != OpeningBook.file_name())
+ if (Options["Book File"].value<std::string>() != OpeningBook.name())
OpeningBook.open(Options["Book File"].value<std::string>());
Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
if (bookMove != MOVE_NONE)
{
- if (PonderSearch)
+ if (Pondering)
wait_for_stop_or_ponderhit();
cout << "bestmove " << bookMove << endl;
- return true;
+ return !QuitRequest;
}
}
- // Read UCI option values
- TT.set_size(Options["Hash"].value<int>());
- if (Options["Clear Hash"].value<bool>())
- {
- Options["Clear Hash"].set_value("false");
- TT.clear();
- }
-
+ // Read UCI options
CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
- SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
- SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
- MultiPV = Options["MultiPV"].value<int>();
+ UCIMultiPV = Options["MultiPV"].value<int>();
+ SkillLevel = Options["Skill level"].value<int>();
UseLogFile = Options["Use Search Log"].value<bool>();
- if (UseLogFile)
- LogFile.open(Options["Search Log Filename"].value<std::string>().c_str(), std::ios::out | std::ios::app);
+ read_evaluation_uci_options(pos.side_to_move());
+
+ if (Options["Clear Hash"].value<bool>())
+ {
+ Options["Clear Hash"].set_value("false");
+ TT.clear();
+ }
+ TT.set_size(Options["Hash"].value<int>());
- read_weights(pos.side_to_move());
+ // 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 ? Max(UCIMultiPV, 4) : UCIMultiPV);
// Set the number of active threads
ThreadsMgr.read_uci_options();
init_eval(ThreadsMgr.active_threads());
- // Wake up needed threads
+ // Wake up needed threads. Main thread, with threadID == 0, is always active
for (int i = 1; i < ThreadsMgr.active_threads(); i++)
ThreadsMgr.wake_sleeping_thread(i);
if (UseTimeManagement)
TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
- // Set best NodesBetweenPolls interval to avoid lagging under
- // heavy time pressure.
+ // Set best NodesBetweenPolls interval to avoid lagging under time pressure
if (MaxNodes)
NodesBetweenPolls = Min(MaxNodes, 30000);
else if (myTime && myTime < 1000)
// 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;
+ {
+ std::string name = Options["Search Log Filename"].value<std::string>();
+ LogFile.open(name.c_str(), std::ios::out | std::ios::app);
+
+ LogFile << "\nSearching: " << pos.to_fen()
+ << "\ninfinite: " << infinite
+ << " ponder: " << ponder
+ << " time: " << myTime
+ << " increment: " << myIncrement
+ << " moves to go: " << movesToGo
+ << endl;
+ }
// We're ready to start thinking. Call the iterative deepening loop function
Move ponderMove = MOVE_NONE;
Move bestMove = id_loop(pos, searchMoves, &ponderMove);
// Print final search statistics
- cout << "info nodes " << pos.nodes_searched()
- << " nps " << nps(pos)
- << " time " << current_search_time() << endl;
-
- // 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();
-
- // Could be both MOVE_NONE when searching on a stalemate position
- cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
+ cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
if (UseLogFile)
{
- if (dbg_show_mean)
- dbg_print_mean(LogFile);
+ int t = current_search_time();
- if (dbg_show_hit_rate)
- dbg_print_hit_rate(LogFile);
-
- LogFile << "\nNodes: " << pos.nodes_searched()
- << "\nNodes/second: " << nps(pos)
- << "\nBest move: " << move_to_san(pos, bestMove);
+ LogFile << "Nodes: " << pos.nodes_searched()
+ << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0)
+ << "\nBest move: " << move_to_san(pos, bestMove);
StateInfo st;
pos.do_move(bestMove, st);
- LogFile << "\nPonder move: "
- << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
- << endl;
- }
-
- if (UseLogFile)
+ LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
+ pos.undo_move(bestMove); // Return from think() with unchanged position
LogFile.close();
+ }
// This makes all the threads to go to sleep
ThreadsMgr.set_active_threads(1);
- return !Quit;
+ // If we are pondering or in infinite search, we shouldn't print the
+ // best move before we are told to do so.
+ if (!StopRequest && (Pondering || InfiniteSearch))
+ wait_for_stop_or_ponderhit();
+
+ // Could be MOVE_NONE when searching on a stalemate position
+ cout << "bestmove " << bestMove;
+
+ // 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;
+
+ cout << endl;
+
+ return !QuitRequest;
}
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.
+ // 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.
Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
SearchStack ss[PLY_MAX_PLUS_2];
- Depth depth;
- Move EasyMove = MOVE_NONE;
- Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
+ Value bestValues[PLY_MAX_PLUS_2];
+ int bestMoveChanges[PLY_MAX_PLUS_2];
+ int depth, aspirationDelta, skillSamplingDepth;
+ Value value, alpha, beta;
+ Move bestMove, easyMove, skillBest, skillPonder;
+
+ // Initialize stuff before a new search
+ memset(ss, 0, 4 * sizeof(SearchStack));
+ TT.new_search();
+ H.clear();
+ *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE;
+ depth = aspirationDelta = skillSamplingDepth = 0;
+ alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
+ ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
- // Moves to search are verified, scored and sorted
- RootMoveList rml(pos, searchMoves);
+ // Moves to search are verified and copied
+ Rml.init(pos, searchMoves);
- // Handle special case of searching on a mate/stale position
- if (rml.size() == 0)
+ // Handle special case of searching on a mate/stalemate position
+ if (Rml.size() == 0)
{
- Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
-
- cout << "info depth " << 1
- << " score " << value_to_uci(s) << endl;
+ cout << "info depth 0 score "
+ << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
+ << endl;
return MOVE_NONE;
}
- // Initialize
- TT.new_search();
- H.clear();
- init_ss_array(ss, PLY_MAX_PLUS_2);
- ValueByIteration[1] = rml[0].pv_score;
- Iteration = 1;
-
- // Send initial RootMoveList scoring (iteration 1)
- cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
- << "info depth " << Iteration
- << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
-
- // Is one move significantly better than others after initial scoring ?
- if ( rml.size() == 1
- || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
- EasyMove = rml[0].pv[0];
+ // Choose a random sampling depth according to SkillLevel so that at low
+ // skills there is an higher risk to pick up a blunder.
+ if (SkillLevelEnabled)
+ skillSamplingDepth = 4 + SkillLevel + (RK.rand<unsigned>() % 4);
// Iterative deepening loop
- while (Iteration < PLY_MAX)
+ while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
{
- // Initialize iteration
- Iteration++;
- BestMoveChangesByIteration[Iteration] = 0;
-
- cout << "info depth " << Iteration << endl;
+ Rml.bestMoveChanges = 0;
+ cout << set960(pos.is_chess960()) << "info depth " << depth << endl;
// Calculate dynamic aspiration window based on previous iterations
- if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
+ if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
{
- int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
- int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
+ int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
+ int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
- AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
- AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
+ aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
+ aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
- alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
- beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
+ alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
+ beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
}
- depth = (Iteration - 2) * ONE_PLY + InitialDepth;
+ // 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 starting from ss+1 to allow calling update_gains()
+ value = search<PV, false, true>(pos, ss+1, alpha, beta, depth * ONE_PLY, 0);
+
+ // Write PV back to transposition table in case the relevant entries
+ // have been overwritten during the search.
+ for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
+ Rml[i].insert_pv_in_tt(pos);
+
+ // Value cannot be trusted. Break out immediately!
+ if (StopRequest)
+ break;
- // Search to the current depth, rml is updated and sorted
- value = root_search(pos, ss, alpha, beta, depth, rml);
+ assert(value >= alpha);
+
+ // In case of failing high/low increase aspiration window and research,
+ // otherwise exit the fail high/low loop.
+ if (value >= beta)
+ {
+ beta = Min(beta + aspirationDelta, VALUE_INFINITE);
+ aspirationDelta += aspirationDelta / 2;
+ }
+ else if (value <= alpha)
+ {
+ AspirationFailLow = true;
+ StopOnPonderhit = false;
+
+ alpha = Max(alpha - aspirationDelta, -VALUE_INFINITE);
+ aspirationDelta += aspirationDelta / 2;
+ }
+ else
+ break;
- if (AbortSearch)
- break; // Value cannot be trusted. Break out immediately!
+ } while (abs(value) < VALUE_KNOWN_WIN);
- //Save info about search result
- ValueByIteration[Iteration] = value;
+ // Collect info about search result
+ bestMove = Rml[0].pv[0];
+ *ponderMove = Rml[0].pv[1];
+ bestValues[depth] = value;
+ bestMoveChanges[depth] = Rml.bestMoveChanges;
- // Drop the easy move if differs from the new best move
- if (rml[0].pv[0] != EasyMove)
- EasyMove = MOVE_NONE;
+ // Do we need to pick now the best and the ponder moves ?
+ if (SkillLevelEnabled && depth == skillSamplingDepth)
+ do_skill_level(&skillBest, &skillPonder);
- if (UseTimeManagement)
+ // Send PV line to GUI and to log file
+ for (int i = 0; i < Min(UCIMultiPV, (int)Rml.size()); i++)
+ cout << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
+
+ if (UseLogFile)
+ LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
+
+ // Init easyMove after first iteration or drop if differs from the best move
+ if (depth == 1 && (Rml.size() == 1 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin))
+ easyMove = bestMove;
+ else if (bestMove != easyMove)
+ easyMove = MOVE_NONE;
+
+ if (UseTimeManagement && !StopRequest)
{
// 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.size() == 1)
- stopSearch = true;
+ bool noMoreTime = false;
// 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
- if ( Iteration >= 8
- && EasyMove == rml[0].pv[0]
- && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
+ if ( depth >= 5
+ && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100
+ && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100)
+ noMoreTime = true;
+
+ // Stop search early if one move seems to be much better than the
+ // others or if there is only a single legal move. In this latter
+ // case we search up to Iteration 8 anyway to get a proper score.
+ if ( depth >= 7
+ && easyMove == bestMove
+ && ( Rml.size() == 1
+ ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
&& current_search_time() > TimeMgr.available_time() / 16)
- ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
+ ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
&& current_search_time() > TimeMgr.available_time() / 32)))
- stopSearch = true;
+ noMoreTime = true;
// Add some extra time if the best move has changed during the last two iterations
- if (Iteration > 5 && Iteration <= 50)
- TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
- BestMoveChangesByIteration[Iteration-1]);
+ if (depth > 4 && depth < 50)
+ TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]);
// 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() > (TimeMgr.available_time() * 80) / 128)
- stopSearch = true;
+ noMoreTime = true;
- if (stopSearch)
+ if (noMoreTime)
{
- if (PonderSearch)
+ if (Pondering)
StopOnPonderhit = true;
else
break;
}
}
-
- if (MaxDepth && Iteration >= MaxDepth)
- break;
}
- *ponderMove = rml[0].pv[1];
- return rml[0].pv[0];
- }
-
-
- // root_search() is the function which searches the root node. It is
- // similar to search_pv except that it prints some information to the
- // standard output and handles the fail low/high loops.
-
- Value root_search(Position& pos, SearchStack* ss, Value alpha,
- Value beta, Depth depth, RootMoveList& rml) {
- StateInfo st;
- CheckInfo ci(pos);
- int64_t nodes;
- Move move;
- Depth ext, newDepth;
- Value value, oldAlpha;
- bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
- int researchCountFH, researchCountFL;
-
- researchCountFH = researchCountFL = 0;
- oldAlpha = alpha;
- isCheck = pos.is_check();
-
- // Step 1. Initialize node (polling is omitted at root)
- ss->currentMove = ss->bestMove = MOVE_NONE;
-
- // 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
- ss->evalMargin = VALUE_NONE;
- ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
-
- // 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)
+ // When using skills fake best and ponder moves with the sub-optimal ones
+ if (SkillLevelEnabled)
{
- // Sort the moves before to (re)search
- rml.set_non_pv_scores(pos);
- rml.sort();
-
- // Step 10. Loop through all moves in the root move list
- for (int i = 0; i < (int)rml.size() && !AbortSearch; i++)
- {
- // This is used by time management
- FirstRootMove = (i == 0);
-
- // Save the current node count before the move is searched
- nodes = pos.nodes_searched();
-
- // Pick the next root move, and print the move and the move number to
- // the standard output.
- move = ss->currentMove = rml[i].pv[0];
-
- if (current_search_time() >= 1000)
- cout << "info currmove " << move
- << " currmovenumber " << i + 1 << endl;
-
- moveIsCheck = pos.move_is_check(move);
- captureOrPromotion = pos.move_is_capture_or_promotion(move);
-
- // Step 11. Decide the new search depth
- ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
- newDepth = depth + ext;
-
- // Step 12. Futility pruning (omitted at root)
-
- // Step extra. Fail high loop
- // If move fails high, we research with bigger window until we are not failing
- // high anymore.
- value = -VALUE_INFINITE;
-
- while (1)
- {
- // Step 13. Make the move
- pos.do_move(move, st, ci, moveIsCheck);
-
- // 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)
- {
- // 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, 1);
- }
- else
- {
- // Step 14. Reduced search
- // if the move fails high will be re-searched at full depth
- bool doFullDepthSearch = true;
-
- if ( depth >= 3 * ONE_PLY
- && !dangerous
- && !captureOrPromotion
- && !move_is_castle(move))
- {
- ss->reduction = reduction<PV>(depth, i - MultiPV + 2);
- if (ss->reduction)
- {
- assert(newDepth-ss->reduction >= ONE_PLY);
-
- // Reduced depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
- doFullDepthSearch = (value > alpha);
- }
- ss->reduction = DEPTH_ZERO; // Restore original reduction
- }
-
- // Step 15. Full depth search
- if (doFullDepthSearch)
- {
- // Full depth non-pv search using alpha as upperbound
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
-
- // 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, 1);
- }
- }
-
- // Step 16. Undo move
- pos.undo_move(move);
-
- // Can we exit fail high loop ?
- if (AbortSearch || value < beta)
- 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.
- ss->bestMove = move;
- rml[i].pv_score = value;
- rml[i].extract_pv_from_tt(pos);
-
- // Inform GUI that PV has changed
- cout << rml[i].pv_info_to_uci(pos, alpha, beta) << endl;
+ if (skillBest == MOVE_NONE) // Still unassigned ?
+ do_skill_level(&skillBest, &skillPonder);
- // Prepare for a research after a fail high, each time with a wider window
- 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 searched nodes counts for this move
- rml[i].nodes += pos.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[i].pv_score = -VALUE_INFINITE;
- else
- {
- // PV move or new best move!
-
- // Update PV
- ss->bestMove = move;
- rml[i].pv_score = value;
- rml[i].extract_pv_from_tt(pos);
-
- // 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 (MultiPV == 1 && i > 0)
- BestMoveChangesByIteration[Iteration]++;
-
- // Inform GUI that PV has changed, in case of multi-pv UCI protocol
- // requires we send all the PV lines properly sorted.
- rml.sort_multipv(i);
-
- for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
- cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
-
- // Update alpha. In multi-pv we don't use aspiration window
- if (MultiPV == 1)
- {
- // Raise alpha to setup proper non-pv search upper bound
- if (value > alpha)
- alpha = value;
- }
- else // Set alpha equal to minimum score among the PV lines
- alpha = rml[Min(i, MultiPV - 1)].pv_score;
-
- } // PV move or new best move
-
- assert(alpha >= oldAlpha);
-
- AspirationFailLow = (alpha == oldAlpha);
-
- if (AspirationFailLow && StopOnPonderhit)
- StopOnPonderhit = false;
-
- } // Root moves loop
-
- // Can we exit fail low loop ?
- if (AbortSearch || !AspirationFailLow)
- break;
-
- // Prepare for a research after a fail low, each time with a wider window
- oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
- researchCountFL++;
-
- } // Fail low loop
-
- // Sort the moves before to return
- rml.sort();
-
- // Write PV lines to transposition table, in case the relevant entries
- // have been overwritten during the search.
- for (int i = 0; i < MultiPV; i++)
- rml[i].insert_pv_in_tt(pos);
+ bestMove = skillBest;
+ *ponderMove = skillPonder;
+ }
- return alpha;
+ return bestMove;
}
// 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 PvNode, bool SpNode>
+ template <NodeType PvNode, bool SpNode, bool Root>
Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
assert(beta > alpha && beta <= VALUE_INFINITE);
assert(PvNode || alpha == beta - 1);
- assert(ply > 0 && ply < PLY_MAX);
+ assert((Root || ply > 0) && ply < PLY_MAX);
assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
Move movesSearched[MOVES_MAX];
+ int64_t nodes;
StateInfo st;
const TTEntry *tte;
Key posKey;
ValueType vt;
Value bestValue, value, oldAlpha;
Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
- bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
+ bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous, isBadCap;
bool mateThreat = false;
- int moveCount = 0;
+ int moveCount = 0, playedMoveCount = 0;
int threadID = pos.thread();
SplitPoint* sp = NULL;
+
refinedValue = bestValue = value = -VALUE_INFINITE;
oldAlpha = alpha;
isCheck = pos.is_check();
mateThreat = sp->mateThreat;
goto split_point_start;
}
- else {} // Hack to fix icc's "statement is unreachable" warning
+ else if (Root)
+ bestValue = alpha;
// Step 1. Initialize node and poll. Polling can abort search
- ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
+ 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] = (ss+2)->mateKiller = MOVE_NONE;
if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
}
// Step 2. Check for aborted search and immediate draw
- if ( AbortSearch
- || ThreadsMgr.cutoff_at_splitpoint(threadID)
- || pos.is_draw()
- || ply >= PLY_MAX - 1)
+ if (( StopRequest
+ || ThreadsMgr.cutoff_at_splitpoint(threadID)
+ || pos.is_draw()
+ || ply >= PLY_MAX - 1) && !Root)
return VALUE_DRAW;
// Step 3. Mate distance pruning
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.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))
+ // 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.
+ if ( !Root
+ && tte
+ && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
+ : ok_to_use_TT(tte, depth, beta, ply)))
{
TT.refresh(tte);
ss->bestMove = ttMove; // Can be MOVE_NONE
return value_from_tt(tte->value(), ply);
}
- // Step 5. Evaluate the position statically and
- // update gain statistics of parent move.
+ // Step 5. Evaluate the position statically and update parent's gain statistics
if (isCheck)
ss->eval = ss->evalMargin = VALUE_NONE;
else if (tte)
if ( !PvNode
&& depth < RazorDepth
&& !isCheck
- && refinedValue < beta - razor_margin(depth)
+ && refinedValue + razor_margin(depth) < beta
&& ttMove == MOVE_NONE
- && !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);
&& !ss->skipNullMove
&& depth < RazorDepth
&& !isCheck
- && refinedValue >= beta + futility_margin(depth, 0)
- && !value_is_mate(beta)
+ && 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);
&& depth > ONE_PLY
&& !isCheck
&& refinedValue >= beta
- && !value_is_mate(beta)
+ && abs(beta) < VALUE_MATE_IN_PLY_MAX
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
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);
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;
if (depth < 6 * ONE_PLY)
mateThreat = true;
threatMove = (ss+1)->bestMove;
+
if ( depth < ThreatDepth
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
}
// Step 9. Internal iterative deepening
- if ( depth >= IIDDepth[PvNode]
- && ttMove == MOVE_NONE
- && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
+ if ( depth >= IIDDepth[PvNode]
+ && ttMove == MOVE_NONE
+ && (PvNode || (!isCheck && ss->eval + IIDMargin >= beta)))
{
Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
tte = TT.retrieve(posKey);
}
- // Expensive mate threat detection (only for PV nodes)
+ // Mate threat detection for PV nodes, otherwise we use null move search
if (PvNode)
mateThreat = pos.has_mate_threat();
split_point_start: // At split points actual search starts from here
// Initialize a MovePicker object for the current position
- // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
- MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
- MovePicker& mp = SpNode ? *sp->mp : mpBase;
+ MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
CheckInfo ci(pos);
ss->bestMove = MOVE_NONE;
- singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
futilityBase = ss->eval + ss->evalMargin;
- singularExtensionNode = !SpNode
+ singularExtensionNode = !Root
+ && !SpNode
&& depth >= SingularExtensionDepth[PvNode]
&& tte
&& tte->move()
else if (move == excludedMove)
continue;
else
- movesSearched[moveCount++] = move;
+ moveCount++;
+
+ if (Root)
+ {
+ // This is used by time management
+ FirstRootMove = (moveCount == 1);
+
+ // Save the current node count before the move is searched
+ nodes = pos.nodes_searched();
+
+ // If it's time to send nodes info, do it here where we have the
+ // correct accumulated node counts searched by each thread.
+ if (SendSearchedNodes)
+ {
+ SendSearchedNodes = false;
+ cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
+ }
+ if (current_search_time() > 2000)
+ cout << "info currmove " << move
+ << " currmovenumber " << moveCount << endl;
+ }
+
+ // At Root and at first iteration do a PV search on all the moves to score root moves
+ isPvMove = (PvNode && moveCount <= (Root ? depth <= ONE_PLY ? 1000 : MultiPV : 1));
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, singleEvasion, mateThreat, &dangerous);
+ ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
- // 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 then ttValue minus a margin then we extend ttMove.
+ // 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 < ONE_PLY)
if (abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value b = ttValue - SingularExtensionMargin;
+ Value rBeta = ttValue - int(depth);
ss->excludedMove = move;
ss->skipNullMove = true;
- Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
+ Value v = search<NonPV>(pos, ss, rBeta - 1, rBeta, depth / 2, ply);
ss->skipNullMove = false;
ss->excludedMove = MOVE_NONE;
ss->bestMove = MOVE_NONE;
- if (v < b)
+ if (v < rBeta)
ext = ONE_PLY;
}
}
{
// Move count based pruning
if ( moveCount >= futility_move_count(depth)
- && !(threatMove && connected_threat(pos, move, threatMove))
- && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
+ && (!threatMove || !connected_threat(pos, move, threatMove))
+ && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy
{
if (SpNode)
lock_grab(&(sp->lock));
// Prune moves with negative SEE at low depths
if ( predictedDepth < 2 * ONE_PLY
- && bestValue > value_mated_in(PLY_MAX)
+ && bestValue > VALUE_MATED_IN_PLY_MAX
&& pos.see_sign(move) < 0)
{
if (SpNode)
}
}
+ // Bad capture detection. Will be used by prob-cut search
+ isBadCap = depth >= 3 * ONE_PLY
+ && depth < 8 * ONE_PLY
+ && captureOrPromotion
+ && move != ttMove
+ && !dangerous
+ && !move_is_promotion(move)
+ && abs(alpha) < VALUE_MATE_IN_PLY_MAX
+ && pos.see_sign(move) < 0;
+
// Step 13. Make the move
pos.do_move(move, st, ci, moveIsCheck);
+ if (!SpNode && !captureOrPromotion)
+ movesSearched[playedMoveCount++] = move;
+
// Step extra. pv search (only in PV nodes)
// The first move in list is the expected PV
- if (PvNode && moveCount == 1)
+ if (isPvMove)
+ {
+ // Aspiration window is disabled in multi-pv case
+ if (Root && MultiPV > 1)
+ alpha = -VALUE_INFINITE;
+
value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
+ }
else
{
// Step 14. Reduced depth search
// If the move fails high will be re-searched at full depth.
bool doFullDepthSearch = true;
+ alpha = SpNode ? sp->alpha : alpha;
if ( depth >= 3 * ONE_PLY
&& !captureOrPromotion
&& ss->killers[1] != move)
{
ss->reduction = reduction<PvNode>(depth, moveCount);
-
if (ss->reduction)
{
alpha = SpNode ? sp->alpha : alpha;
ss->reduction = DEPTH_ZERO; // Restore original reduction
}
+ // Probcut search for bad captures. If a reduced search returns a value
+ // very below beta then we can (almost) safely prune the bad capture.
+ if (isBadCap)
+ {
+ ss->reduction = 3 * ONE_PLY;
+ Value rAlpha = alpha - 300;
+ Depth d = newDepth - ss->reduction;
+ value = -search<NonPV>(pos, ss+1, -(rAlpha+1), -rAlpha, d, ply+1);
+ doFullDepthSearch = (value > rAlpha);
+ ss->reduction = DEPTH_ZERO; // Restore original reduction
+ }
+
// Step 15. Full depth search
if (doFullDepthSearch)
{
// 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)
+ if (PvNode && value > alpha && (Root || value < beta))
value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
}
}
if (SpNode)
sp->bestValue = value;
- if (value > alpha)
+ if (!Root && value > alpha)
{
if (PvNode && value < beta) // We want always alpha < beta
{
ss->bestMove = move;
if (SpNode)
- sp->parentSstack->bestMove = move;
+ sp->ss->bestMove = move;
}
}
+ if (Root)
+ {
+ // 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 break out of the loop without updating the best
+ // move and/or PV.
+ if (StopRequest)
+ break;
+
+ // Remember searched nodes counts for this move
+ mp.rm->nodes += pos.nodes_searched() - nodes;
+
+ // PV move or new best move ?
+ if (isPvMove || value > alpha)
+ {
+ // Update PV
+ ss->bestMove = move;
+ mp.rm->pv_score = value;
+ mp.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++;
+
+ Rml.sort_multipv(moveCount);
+
+ // Update alpha. In multi-pv we don't use aspiration window, so
+ // set alpha equal to minimum score among the PV lines.
+ if (MultiPV > 1)
+ alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
+ else if (value > alpha)
+ alpha = value;
+ }
+ else
+ mp.rm->pv_score = -VALUE_INFINITE;
+
+ } // Root
+
// Step 18. Check for split
- if ( !SpNode
+ if ( !Root
+ && !SpNode
&& depth >= ThreadsMgr.min_split_depth()
&& ThreadsMgr.active_threads() > 1
&& bestValue < beta
&& ThreadsMgr.available_thread_exists(threadID)
- && !AbortSearch
- && !ThreadsMgr.cutoff_at_splitpoint(threadID)
- && Iteration <= 99)
+ && !StopRequest
+ && !ThreadsMgr.cutoff_at_splitpoint(threadID))
ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
threatMove, mateThreat, moveCount, &mp, PvNode);
}
// Step 20. Update tables
// If the search is not aborted, update the transposition table,
// history counters, and killer moves.
- if (!SpNode && !AbortSearch && !ThreadsMgr.cutoff_at_splitpoint(threadID))
+ if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
{
move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
if ( bestValue >= beta
&& !pos.move_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);
}
}
bestValue = futilityValue;
continue;
}
+
+ // Prune moves with negative or equal SEE
+ if ( futilityBase < beta
+ && depth < DEPTH_ZERO
+ && pos.see(move) <= 0)
+ continue;
}
// Detect non-capture evasions that are candidate to be pruned
evasionPrunable = isCheck
- && bestValue > value_mated_in(PLY_MAX)
+ && bestValue > VALUE_MATED_IN_PLY_MAX
&& !pos.move_is_capture(move)
&& !pos.can_castle(pos.side_to_move());
}
- // value_is_mate() checks if the given value is a mate one eventually
- // compensated for the ply.
-
- bool value_is_mate(Value value) {
-
- assert(abs(value) <= VALUE_INFINITE);
-
- return value <= value_mated_in(PLY_MAX)
- || value >= value_mate_in(PLY_MAX);
- }
-
-
// 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.
Value value_to_tt(Value v, int ply) {
- if (v >= value_mate_in(PLY_MAX))
+ if (v >= VALUE_MATE_IN_PLY_MAX)
return v + ply;
- if (v <= value_mated_in(PLY_MAX))
+ if (v <= VALUE_MATED_IN_PLY_MAX)
return v - ply;
return v;
Value value_from_tt(Value v, int ply) {
- if (v >= value_mate_in(PLY_MAX))
+ if (v >= VALUE_MATE_IN_PLY_MAX)
return v - ply;
- if (v <= value_mated_in(PLY_MAX))
+ if (v <= VALUE_MATED_IN_PLY_MAX)
return v + ply;
return v;
// 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) {
+ Depth extension(const Position& pos, Move m, bool captureOrPromotion,
+ bool moveIsCheck, bool mateThreat, bool* dangerous) {
assert(m != MOVE_NONE);
Depth result = DEPTH_ZERO;
- *dangerous = moveIsCheck | singleEvasion | mateThreat;
+ *dangerous = moveIsCheck | mateThreat;
if (*dangerous)
{
if (moveIsCheck && pos.see_sign(m) >= 0)
result += CheckExtension[PvNode];
- if (singleEvasion)
- result += SingleEvasionExtension[PvNode];
-
if (mateThreat)
result += MateThreatExtension[PvNode];
}
*dangerous = true;
}
- if ( PvNode
- && captureOrPromotion
- && pos.type_of_piece_on(move_to(m)) != PAWN
- && pos.see_sign(m) >= 0)
- {
- result += ONE_PLY / 2;
- *dangerous = true;
- }
-
return Min(result, ONE_PLY);
}
// 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) {
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.
+ // value of the threatening piece, don't prune moves 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 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 >= Max(VALUE_MATE_IN_PLY_MAX, beta)
+ || v < Min(VALUE_MATED_IN_PLY_MAX, beta))
&& ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
|| ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
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;
-
- ss->killers[1] = ss->killers[0];
- 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.
&& after != VALUE_NONE
&& pos.captured_piece_type() == PIECE_TYPE_NONE
&& !move_is_special(m))
- H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
+ H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
}
if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
else
- s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
+ s << "mate " << (v > 0 ? VALUE_MATE - v + 1 : -VALUE_MATE - v) / 2;
return s.str();
}
- // nps() computes the current nodes/second count.
- int nps(const Position& pos) {
+ // speed_to_uci() returns a string with time stats of current search suitable
+ // to be sent to UCI gui.
+
+ std::string speed_to_uci(int64_t nodes) {
+ std::stringstream s;
int t = current_search_time();
- return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
+
+ s << " nodes " << nodes
+ << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
+ << " time " << t;
+
+ return s.str();
}
int t = current_search_time();
// Poll for input
- if (data_available())
+ if (input_available())
{
// We are line oriented, don't read single chars
std::string command;
- if (!std::getline(std::cin, command))
- command = "quit";
-
- if (command == "quit")
+ if (!std::getline(std::cin, command) || command == "quit")
{
- AbortSearch = true;
- PonderSearch = false;
- Quit = true;
+ // Quit the program as soon as possible
+ Pondering = false;
+ QuitRequest = StopRequest = true;
return;
}
else if (command == "stop")
{
- AbortSearch = true;
- PonderSearch = false;
+ // Stop calculating as soon as possible, but still send the "bestmove"
+ // and possibly the "ponder" token when finishing the search.
+ Pondering = false;
+ StopRequest = true;
}
else if (command == "ponderhit")
- ponderhit();
+ {
+ // The opponent has played the expected move. GUI sends "ponderhit" if
+ // we were told to ponder on the same move the opponent has played. We
+ // should continue searching but switching from pondering to normal search.
+ Pondering = false;
+
+ if (StopOnPonderhit)
+ StopRequest = true;
+ }
}
// Print search information
if (dbg_show_hit_rate)
dbg_print_hit_rate();
- cout << "info nodes " << pos.nodes_searched() << " nps " << nps(pos)
- << " time " << t << endl;
+ // Send info on searched nodes as soon as we return to root
+ SendSearchedNodes = true;
}
// Should we stop the search?
- if (PonderSearch)
+ if (Pondering)
return;
bool stillAtFirstMove = FirstRootMove
bool noMoreTime = t > TimeMgr.maximum_time()
|| stillAtFirstMove;
- if ( (Iteration >= 3 && UseTimeManagement && noMoreTime)
+ if ( (UseTimeManagement && noMoreTime)
|| (ExactMaxTime && t >= ExactMaxTime)
- || (Iteration >= 3 && MaxNodes && pos.nodes_searched() >= MaxNodes))
- AbortSearch = true;
- }
-
-
- // 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() {
-
- int t = current_search_time();
- PonderSearch = false;
-
- bool stillAtFirstMove = FirstRootMove
- && !AspirationFailLow
- && t > TimeMgr.available_time();
-
- bool noMoreTime = t > TimeMgr.maximum_time()
- || stillAtFirstMove;
-
- if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit))
- AbortSearch = true;
- }
-
-
- // init_ss_array() does a fast reset of the first entries of a SearchStack
- // array and of all the excludedMove and skipNullMove entries.
-
- void init_ss_array(SearchStack* ss, int size) {
-
- for (int i = 0; i < size; i++, ss++)
- {
- ss->excludedMove = MOVE_NONE;
- ss->skipNullMove = false;
- ss->reduction = DEPTH_ZERO;
- ss->sp = NULL;
-
- if (i < 3)
- ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
- }
+ || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
+ StopRequest = true;
}
// 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()).
+ // after which the bestmove and pondermove will be printed.
void wait_for_stop_or_ponderhit() {
std::string command;
- while (true)
- {
- if (!std::getline(std::cin, command))
- command = "quit";
+ // Wait for a command from stdin
+ while ( std::getline(std::cin, command)
+ && command != "ponderhit" && command != "stop" && command != "quit") {};
- if (command == "quit")
- {
- Quit = true;
- break;
- }
- else if (command == "ponderhit" || command == "stop")
- break;
- }
+ if (command != "ponderhit" && command != "stop")
+ QuitRequest = true; // Must be "quit" or getline() returned false
}
threads[threadID].state = THREAD_SEARCHING;
- // Here we call search() with SplitPoint template parameter set to true
+ // Copy SplitPoint position and search stack and call search()
+ // with SplitPoint template parameter set to true.
+ SearchStack ss[PLY_MAX_PLUS_2];
SplitPoint* tsp = threads[threadID].splitPoint;
Position pos(*tsp->pos, threadID);
- SearchStack* ss = tsp->sstack[threadID] + 1;
- ss->sp = tsp;
+
+ memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
+ (ss+1)->sp = tsp;
if (tsp->pvNode)
- search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ search<PV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
else
- search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
+ search<NonPV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
assert(threads[threadID].state == THREAD_SEARCHING);
splitPoint.moveCount = moveCount;
splitPoint.pos = &pos;
splitPoint.nodes = 0;
- splitPoint.parentSstack = ss;
+ splitPoint.ss = ss;
for (i = 0; i < activeThreads; i++)
splitPoint.slaves[i] = 0;
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.
+ // their idle loop.
for (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()
k = pos.get_key();
tte = TT.retrieve(k);
- // Don't overwrite exsisting correct entries
+ // Don't overwrite existing correct entries
if (!tte || tte->move() != pv[ply])
{
v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
}
// pv_info_to_uci() returns a string with information on the current PV line
- // formatted according to UCI specification and eventually writes the info
- // to a log file. It is called at each iteration or after a new pv is found.
+ // formatted according to UCI specification.
- std::string RootMove::pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine) {
+ std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha,
+ Value beta, int pvIdx) {
+ std::stringstream s, l;
+ Move* m = pv;
- std::stringstream s;
+ while (*m != MOVE_NONE)
+ l << *m++ << " ";
- s << "info depth " << Iteration // FIXME
- << " multipv " << pvLine + 1
+ s << "info depth " << depth
+ << " seldepth " << int(m - pv)
+ << " multipv " << pvIdx + 1
<< " score " << value_to_uci(pv_score)
<< (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
- << " time " << current_search_time()
- << " nodes " << pos.nodes_searched()
- << " nps " << nps(pos)
- << " pv ";
-
- for (Move* m = pv; *m != MOVE_NONE; m++)
- s << *m << " ";
+ << speed_to_uci(pos.nodes_searched())
+ << " pv " << l.str();
- if (UseLogFile && pvLine == 0)
- {
- ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
- pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
-
- LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
- }
return s.str();
}
- RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
+ void RootMoveList::init(Position& pos, Move searchMoves[]) {
- SearchStack ss[PLY_MAX_PLUS_2];
MoveStack mlist[MOVES_MAX];
- StateInfo st;
Move* sm;
- // Initialize search stack
- init_ss_array(ss, PLY_MAX_PLUS_2);
- ss[0].eval = ss[0].evalMargin = VALUE_NONE;
+ clear();
+ bestMoveChanges = 0;
- // Generate all legal moves
- MoveStack* last = generate_moves(pos, mlist);
-
- // Add each move to the RootMoveList's vector
+ // Generate all legal moves and add them to RootMoveList
+ MoveStack* last = generate<MV_LEGAL>(pos, mlist);
for (MoveStack* cur = mlist; cur != last; cur++)
{
// If we have a searchMoves[] list then verify cur->move
if (searchMoves[0] && *sm != cur->move)
continue;
- // Find a quick score for the move and add to the list
- pos.do_move(cur->move, st);
-
RootMove rm;
- rm.pv[0] = ss[0].currentMove = cur->move;
+ rm.pv[0] = cur->move;
rm.pv[1] = MOVE_NONE;
- rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
+ rm.pv_score = -VALUE_INFINITE;
push_back(rm);
-
- pos.undo_move(cur->move);
}
- sort();
}
- // Score root moves using the standard way used in main search, the moves
- // are scored according to the order in which are returned by MovePicker.
- // This is the second order score that is used to compare the moves when
- // the first order pv scores of both moves are equal.
- void RootMoveList::set_non_pv_scores(const Position& pos)
- {
- Move move;
- Value score = VALUE_ZERO;
- MovePicker mp(pos, MOVE_NONE, ONE_PLY, H);
+ // When playing with strength handicap choose best move among the MultiPV set
+ // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen.
+ void do_skill_level(Move* best, Move* ponder) {
- while ((move = mp.get_next_move()) != MOVE_NONE)
- for (Base::iterator it = begin(); it != end(); ++it)
- if (it->pv[0] == move)
- {
- it->non_pv_score = score--;
- break;
- }
+ assert(MultiPV > 1);
+
+ // Rml list is already sorted by pv_score in descending order
+ int s;
+ int max_s = -VALUE_INFINITE;
+ int size = Min(MultiPV, (int)Rml.size());
+ int max = Rml[0].pv_score;
+ int var = Min(max - Rml[size - 1].pv_score, PawnValueMidgame);
+ int wk = 120 - 2 * SkillLevel;
+
+ // PRNG sequence should be non deterministic
+ for (int i = abs(get_system_time() % 50); i > 0; i--)
+ RK.rand<unsigned>();
+
+ // 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 (int i = 0; i < size; i++)
+ {
+ s = Rml[i].pv_score;
+
+ // Don't allow crazy blunders even at very low skills
+ if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin)
+ break;
+
+ // This is our magical formula
+ s += ((max - s) * wk + var * (RK.rand<unsigned>() % wk)) / 128;
+
+ if (s > max_s)
+ {
+ max_s = s;
+ *best = Rml[i].pv[0];
+ *ponder = Rml[i].pv[1];
+ }
+ }
}
} // namespace
projects / stockfish / blobdiff