X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=35a396814d676f4878738150ddd129d20e551bb1;hb=96d3b1c92b8db7d2238fc4993a4f3da49f04d614;hp=2e12f82e2a44ff16b3c31a6fc75afb97e715db5d;hpb=018022b8666200dacd3533e215e2de41f93df9da;p=stockfish
diff --git a/src/search.cpp b/src/search.cpp
index 2e12f82e..35a39681 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1,7 +1,7 @@
/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -17,124 +17,53 @@
along with this program. If not, see .
*/
+#include
#include
#include
#include
-#include
#include
#include
-#include
#include "book.h"
#include "evaluate.h"
#include "history.h"
-#include "misc.h"
-#include "move.h"
#include "movegen.h"
#include "movepick.h"
+#include "notation.h"
#include "search.h"
#include "timeman.h"
#include "thread.h"
#include "tt.h"
#include "ucioption.h"
-using std::cout;
-using std::endl;
+namespace Search {
+
+ volatile SignalsType Signals;
+ LimitsType Limits;
+ std::vector RootMoves;
+ Position RootPos;
+ Color RootColor;
+ Time::point SearchTime;
+ StateStackPtr SetupStates;
+}
+
+using std::string;
+using Eval::evaluate;
+using namespace Search;
namespace {
// Set to true to force running with one thread. Used for debugging
const bool FakeSplit = false;
- // Different node types, used as template parameter
- enum NodeType { Root, PV, NonPV, SplitPointPV, SplitPointNonPV };
-
- // 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
- // according to the order in which moves are returned by MovePicker.
- struct RootMove {
-
- RootMove();
- RootMove(const RootMove& rm) { *this = rm; }
- RootMove& operator=(const RootMove& rm);
-
- // 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.
- 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(Position& pos, int depth, int selDepth,
- Value alpha, Value beta, int pvIdx);
- int64_t nodes;
- Value pv_score;
- Value non_pv_score;
- Move pv[PLY_MAX_PLUS_2];
- };
-
- // RootMoveList struct is just a vector of RootMove objects,
- // with an handful of methods above the standard ones.
- struct RootMoveList : public std::vector {
-
- typedef std::vector Base;
-
- void init(Position& pos, Move searchMoves[]);
- void sort() { insertion_sort(begin(), end()); }
- void sort_first(int n) { insertion_sort(begin(), begin() + n); }
-
- int bestMoveChanges;
- };
-
-
- /// Constants
-
- // 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]; }
+ // This is the minimum interval in msec between two check_time() calls
+ const int TimerResolution = 5;
- // Step 6. Razoring
-
- // Maximum depth for razoring
- const Depth RazorDepth = 4 * ONE_PLY;
+ // Different node types, used as template parameter
+ enum NodeType { Root, PV, NonPV, SplitPointRoot, SplitPointPV, SplitPointNonPV };
// Dynamic razoring margin based on depth
- inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
-
- // Maximum depth for use of dynamic threat detection when null move fails low
- const Depth ThreatDepth = 5 * ONE_PLY;
-
- // Step 9. Internal iterative deepening
-
- // Minimum depth for use of internal iterative deepening
- 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. Array index 0 is used for non-PV nodes, index 1 for PV nodes
- const Depth CheckExtension[] = { ONE_PLY / 2, ONE_PLY / 1 };
- const Depth PawnEndgameExtension[] = { ONE_PLY / 1, ONE_PLY / 1 };
- const Depth PawnPushTo7thExtension[] = { ONE_PLY / 2, ONE_PLY / 2 };
- const Depth PassedPawnExtension[] = { DEPTH_ZERO, ONE_PLY / 2 };
-
- // Minimum depth for use of singular extension
- const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY };
-
- // Step 12. Futility pruning
-
- // Futility margin for quiescence search
- const Value FutilityMarginQS = Value(0x80);
+ inline Value razor_margin(Depth d) { return Value(512 + 16 * int(d)); }
// Futility lookup tables (initialized at startup) and their access functions
Value FutilityMargins[16][64]; // [depth][moveNumber]
@@ -142,197 +71,60 @@ namespace {
inline Value futility_margin(Depth d, int mn) {
- return d < 7 * ONE_PLY ? FutilityMargins[Max(d, 1)][Min(mn, 63)]
+ return d < 7 * ONE_PLY ? FutilityMargins[std::max(int(d), 1)][std::min(mn, 63)]
: 2 * VALUE_INFINITE;
}
- inline int futility_move_count(Depth d) {
-
- return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES;
- }
-
- // Step 14. Reduced search
-
// Reduction lookup tables (initialized at startup) and their access function
int8_t Reductions[2][64][64]; // [pv][depth][moveNumber]
template inline Depth reduction(Depth d, int mn) {
- return (Depth) Reductions[PvNode][Min(d / ONE_PLY, 63)][Min(mn, 63)];
+ 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);
-
-
- /// Namespace variables
-
- // Root move list
- RootMoveList Rml;
-
- // MultiPV mode
- int MultiPV, UCIMultiPV;
-
- // Time management variables
- bool StopOnPonderhit, FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
+ size_t PVSize, PVIdx;
TimeManager TimeMgr;
- SearchLimits Limits;
-
- // Log file
- std::ofstream LogFile;
-
- // Skill level adjustment
- int SkillLevel;
- bool SkillLevelEnabled;
-
- // 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
+ int BestMoveChanges;
+ Value DrawValue[COLOR_NB];
History H;
-
- /// Local functions
-
- Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
-
template
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- template
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth);
+ template
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
- bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
- bool connected_moves(const Position& pos, Move m1, Move m2);
+ void id_loop(Position& pos);
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_gains(const Position& pos, Move move, Value before, Value after);
- void do_skill_level(Move* best, Move* ponder);
-
- int current_search_time(int set = 0);
- std::string value_to_uci(Value v);
- std::string speed_to_uci(int64_t nodes);
- void poll(const Position& pos);
- void wait_for_stop_or_ponderhit();
-
- // 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 struct MovePickerExt : public MovePicker {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
- : MovePicker(p, ttm, d, h, ss, b) {}
-
- RootMove& current() { assert(false); return Rml[0]; } // Dummy, needed to compile
- };
-
- // In case of a SpNode we use split point's shared MovePicker object as moves source
- template<> struct MovePickerExt : public MovePickerExt {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
- : MovePickerExt(p, ttm, d, h, ss, b), mp(ss->sp->mp) {}
-
- Move get_next_move() { return mp->get_next_move(); }
- MovePicker* mp;
- };
-
- template<> struct MovePickerExt : public MovePickerExt {
-
- MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
- : MovePickerExt(p, ttm, d, h, ss, b) {}
- };
-
- // In case of a Root node we use RootMoveList as moves source
- template<> struct MovePickerExt : public MovePicker {
-
- MovePickerExt(const Position&, Move, Depth, const History&, SearchStack*, Value);
- RootMove& current() { return Rml[cur]; }
- Move get_next_move() { return ++cur < (int)Rml.size() ? Rml[cur].pv[0] : MOVE_NONE; }
-
- int cur;
- };
-
- // 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;
- }
-
- // 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
- FORCE_INLINE Depth extension(const Position& pos, Move m, bool captureOrPromotion,
- bool moveIsCheck, bool* dangerous) {
- assert(m != MOVE_NONE);
-
- Depth result = DEPTH_ZERO;
- *dangerous = moveIsCheck;
-
- if (moveIsCheck && pos.see_sign(m) >= 0)
- result += CheckExtension[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;
- }
+ bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta);
+ bool yields_to_threat(const Position& pos, Move move, Move threat);
+ bool prevents_threat(const Position& pos, Move move, Move threat);
+ string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
+
+ struct Skill {
+ Skill(int l) : level(l), best(MOVE_NONE) {}
+ ~Skill() {
+ if (enabled()) // Swap best PV line with the sub-optimal one
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(),
+ RootMoves.end(), best ? best : pick_move()));
}
- 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_ZERO)
- && !move_is_special(m))
- {
- result += PawnEndgameExtension[PvNode];
- *dangerous = true;
- }
+ bool enabled() const { return level < 20; }
+ bool time_to_pick(int depth) const { return depth == 1 + level; }
+ Move pick_move();
- return Min(result, ONE_PLY);
- }
+ int level;
+ Move best;
+ };
} // namespace
-/// init_search() is called during startup to initialize various lookup tables
+/// Search::init() is called during startup to initialize various lookup tables
-void init_search() {
+void Search::init() {
int d; // depth (ONE_PLY == 2)
int hd; // half depth (ONE_PLY == 1)
@@ -353,170 +145,132 @@ void init_search() {
// Init futility move count array
for (d = 0; d < 32; d++)
- FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(d, 2.0));
+ FutilityMoveCounts[d] = int(3.001 + 0.25 * pow(double(d), 2.0));
}
-/// 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.
+/// Search::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.
-int64_t perft(Position& pos, Depth depth) {
-
- MoveStack mlist[MAX_MOVES];
- StateInfo st;
- Move m;
- int64_t sum = 0;
+size_t Search::perft(Position& pos, Depth depth) {
- // Generate all legal moves
- MoveStack* last = generate(pos, mlist);
+ // At the last ply just return the number of legal moves (leaf nodes)
+ if (depth == ONE_PLY)
+ return MoveList(pos).size();
- // 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
+ StateInfo st;
+ size_t cnt = 0;
CheckInfo ci(pos);
- for (MoveStack* cur = mlist; cur != last; cur++)
+
+ for (MoveList ml(pos); !ml.end(); ++ml)
{
- m = cur->move;
- pos.do_move(m, st, ci, pos.move_gives_check(m, ci));
- sum += perft(pos, depth - ONE_PLY);
- pos.undo_move(m);
+ pos.do_move(ml.move(), st, ci, pos.move_gives_check(ml.move(), ci));
+ cnt += perft(pos, depth - ONE_PLY);
+ pos.undo_move(ml.move());
}
- return sum;
+
+ return cnt;
}
-/// think() is the external interface to Stockfish's search, and is called when
-/// 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.
+/// Search::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 RootPos and at the end prints the "bestmove" to output.
-bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) {
+void Search::think() {
- static Book book;
+ static PolyglotBook book; // Defined static to initialize the PRNG only once
- // Initialize global search-related variables
- StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
- NodesSincePoll = 0;
- current_search_time(get_system_time());
- Limits = limits;
- TimeMgr.init(Limits, pos.startpos_ply_counter());
+ RootColor = RootPos.side_to_move();
+ TimeMgr.init(Limits, RootPos.startpos_ply_counter(), RootColor);
- // Set best NodesBetweenPolls interval to avoid lagging under time pressure
- if (Limits.maxNodes)
- NodesBetweenPolls = Min(Limits.maxNodes, 30000);
- else if (Limits.time && Limits.time < 1000)
- NodesBetweenPolls = 1000;
- else if (Limits.time && Limits.time < 5000)
- NodesBetweenPolls = 5000;
- else
- NodesBetweenPolls = 30000;
+ if (RootMoves.empty())
+ {
+ RootMoves.push_back(MOVE_NONE);
+ sync_cout << "info depth 0 score "
+ << score_to_uci(RootPos.in_check() ? -VALUE_MATE : VALUE_DRAW)
+ << sync_endl;
- // Look for a book move
- if (Options["OwnBook"].value())
+ goto finalize;
+ }
+
+ if (Options["OwnBook"] && !Limits.infinite)
{
- if (Options["Book File"].value() != book.name())
- book.open(Options["Book File"].value());
+ Move bookMove = book.probe(RootPos, Options["Book File"], Options["Best Book Move"]);
- Move bookMove = book.get_move(pos, Options["Best Book Move"].value());
- if (bookMove != MOVE_NONE)
+ if (bookMove && std::count(RootMoves.begin(), RootMoves.end(), bookMove))
{
- if (Limits.ponder)
- wait_for_stop_or_ponderhit();
-
- cout << "bestmove " << bookMove << endl;
- return !QuitRequest;
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(), RootMoves.end(), bookMove));
+ goto finalize;
}
}
- // Read UCI options
- UCIMultiPV = Options["MultiPV"].value();
- SkillLevel = Options["Skill Level"].value();
-
- read_evaluation_uci_options(pos.side_to_move());
- Threads.read_uci_options();
-
- // If needed allocate pawn and material hash tables and adjust TT size
- Threads.init_hash_tables();
- TT.set_size(Options["Hash"].value());
-
- if (Options["Clear Hash"].value())
+ if (Options["Contempt Factor"] && !Options["UCI_AnalyseMode"])
{
- Options["Clear Hash"].set_value("false");
- TT.clear();
+ int cf = Options["Contempt Factor"] * PawnValueMg / 100; // From centipawns
+ cf = cf * MaterialTable::game_phase(RootPos) / PHASE_MIDGAME; // Scale down with phase
+ DrawValue[ RootColor] = VALUE_DRAW - Value(cf);
+ DrawValue[~RootColor] = VALUE_DRAW + Value(cf);
}
+ else
+ DrawValue[WHITE] = DrawValue[BLACK] = VALUE_DRAW;
- // 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);
-
- // Wake up needed threads and reset maxPly counter
- for (int i = 0; i < Threads.size(); i++)
+ if (Options["Use Search Log"])
{
- Threads[i].wake_up();
- Threads[i].maxPly = 0;
+ Log log(Options["Search Log Filename"]);
+ log << "\nSearching: " << RootPos.to_fen()
+ << "\ninfinite: " << Limits.infinite
+ << " ponder: " << Limits.ponder
+ << " time: " << Limits.time[RootColor]
+ << " increment: " << Limits.inc[RootColor]
+ << " moves to go: " << Limits.movestogo
+ << std::endl;
}
- // Write to log file and keep it open to be accessed during the search
- if (Options["Use Search Log"].value())
- {
- std::string name = Options["Search Log Filename"].value();
- LogFile.open(name.c_str(), std::ios::out | std::ios::app);
-
- if (LogFile.is_open())
- LogFile << "\nSearching: " << pos.to_fen()
- << "\ninfinite: " << Limits.infinite
- << " ponder: " << Limits.ponder
- << " time: " << Limits.time
- << " increment: " << Limits.increment
- << " moves to go: " << Limits.movesToGo
- << endl;
- }
+ Threads.wake_up();
+
+ // Set best timer interval to avoid lagging under time pressure. Timer is
+ // used to check for remaining available thinking time.
+ if (Limits.use_time_management())
+ Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 16,
+ TimerResolution)));
+ else if (Limits.nodes)
+ Threads.set_timer(2 * TimerResolution);
+ else
+ Threads.set_timer(100);
- // We're ready to start thinking. Call the iterative deepening loop function
- Move ponderMove = MOVE_NONE;
- Move bestMove = id_loop(pos, searchMoves, &ponderMove);
+ id_loop(RootPos); // Let's start searching !
- cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
+ Threads.set_timer(0); // Stop timer
+ Threads.sleep();
- // Write final search statistics and close log file
- if (LogFile.is_open())
+ if (Options["Use Search Log"])
{
- int t = current_search_time();
+ Time::point elapsed = Time::now() - SearchTime + 1;
- LogFile << "Nodes: " << pos.nodes_searched()
- << "\nNodes/second: " << (t > 0 ? pos.nodes_searched() * 1000 / t : 0)
- << "\nBest move: " << move_to_san(pos, bestMove);
+ Log log(Options["Search Log Filename"]);
+ log << "Nodes: " << RootPos.nodes_searched()
+ << "\nNodes/second: " << RootPos.nodes_searched() * 1000 / elapsed
+ << "\nBest move: " << move_to_san(RootPos, RootMoves[0].pv[0]);
StateInfo st;
- pos.do_move(bestMove, st);
- LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
- pos.undo_move(bestMove); // Return from think() with unchanged position
- LogFile.close();
+ RootPos.do_move(RootMoves[0].pv[0], st);
+ log << "\nPonder move: " << move_to_san(RootPos, RootMoves[0].pv[1]) << std::endl;
+ RootPos.undo_move(RootMoves[0].pv[0]);
}
- // This makes all the threads to go to sleep
- Threads.set_size(1);
+finalize:
- // If we are pondering or in infinite search, we shouldn't print the
- // best move before we are told to do so.
- if (!StopRequest && (Limits.ponder || Limits.infinite))
- wait_for_stop_or_ponderhit();
+ // When we reach max depth we arrive here even without Signals.stop is raised,
+ // 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))
+ RootPos.this_thread()->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;
+ // Best move could be MOVE_NONE when searching on a stalemate position
+ sync_cout << "bestmove " << move_to_uci(RootMoves[0].pv[0], RootPos.is_chess960())
+ << " ponder " << move_to_uci(RootMoves[0].pv[1], RootPos.is_chess960())
+ << sync_endl;
}
@@ -526,170 +280,179 @@ namespace {
// 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) {
+ void id_loop(Position& pos) {
- SearchStack ss[PLY_MAX_PLUS_2];
- Value bestValues[PLY_MAX_PLUS_2];
- int bestMoveChanges[PLY_MAX_PLUS_2];
- int depth, selDepth, aspirationDelta;
- Value value, alpha, beta;
- Move bestMove, easyMove, skillBest, skillPonder;
+ Stack ss[MAX_PLY_PLUS_2];
+ int depth, prevBestMoveChanges;
+ Value bestValue, alpha, beta, delta;
+ bool bestMoveNeverChanged = true;
- // Initialize stuff before a new search
- memset(ss, 0, 4 * sizeof(SearchStack));
+ memset(ss, 0, 4 * sizeof(Stack));
+ depth = BestMoveChanges = 0;
+ bestValue = delta = -VALUE_INFINITE;
+ ss->currentMove = MOVE_NULL; // Hack to skip update gains
TT.new_search();
H.clear();
- *ponderMove = bestMove = easyMove = skillBest = skillPonder = MOVE_NONE;
- depth = aspirationDelta = 0;
- alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
- ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
- // Moves to search are verified and copied
- Rml.init(pos, searchMoves);
+ PVSize = Options["MultiPV"];
+ Skill skill(Options["Skill Level"]);
- // Handle special case of searching on a mate/stalemate position
- if (Rml.size() == 0)
- {
- cout << "info depth 0 score "
- << value_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW)
- << endl;
+ // Do we have to play with skill handicap? In this case enable MultiPV search
+ // that we will use behind the scenes to retrieve a set of possible moves.
+ if (skill.enabled() && PVSize < 4)
+ PVSize = 4;
- return MOVE_NONE;
- }
+ PVSize = std::min(PVSize, RootMoves.size());
// Iterative deepening loop until requested to stop or target depth reached
- while (!StopRequest && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth))
+ while (++depth <= MAX_PLY && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
{
- Rml.bestMoveChanges = 0;
- cout << set960(pos.is_chess960()) << "info depth " << depth << endl;
-
- // Calculate dynamic aspiration window based on previous iterations
- if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
- {
- int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
- int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
+ // Save last iteration's scores before first PV line is searched and all
+ // the move scores but the (new) PV are set to -VALUE_INFINITE.
+ for (size_t i = 0; i < RootMoves.size(); i++)
+ RootMoves[i].prevScore = RootMoves[i].score;
- aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
- aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
+ prevBestMoveChanges = BestMoveChanges; // Only sensible when PVSize == 1
+ BestMoveChanges = 0;
- alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
- beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
- }
-
- // 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(pos, ss+1, alpha, beta, depth * ONE_PLY);
-
- // 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;
-
- // In case of failing high/low increase aspiration window and research,
- // otherwise exit the fail high/low loop.
- if (value >= beta)
+ // MultiPV loop. We perform a full root search for each PV line
+ for (PVIdx = 0; PVIdx < PVSize; PVIdx++)
+ {
+ // Set aspiration window default width
+ if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN)
{
- beta = Min(beta + aspirationDelta, VALUE_INFINITE);
- aspirationDelta += aspirationDelta / 2;
+ delta = Value(16);
+ alpha = RootMoves[PVIdx].prevScore - delta;
+ beta = RootMoves[PVIdx].prevScore + delta;
}
- else if (value <= alpha)
+ else
{
- AspirationFailLow = true;
- StopOnPonderhit = false;
-
- alpha = Max(alpha - aspirationDelta, -VALUE_INFINITE);
- aspirationDelta += aspirationDelta / 2;
+ alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
}
- else
- break;
-
- } while (abs(value) < VALUE_KNOWN_WIN);
-
- // Collect info about search result
- bestMove = Rml[0].pv[0];
- *ponderMove = Rml[0].pv[1];
- bestValues[depth] = value;
- bestMoveChanges[depth] = Rml.bestMoveChanges;
- // Do we need to pick now the best and the ponder moves ?
- if (SkillLevelEnabled && depth == 1 + SkillLevel)
- do_skill_level(&skillBest, &skillPonder);
+ // Start with a small aspiration window and, in case of fail high/low,
+ // research with bigger window until not failing high/low anymore.
+ while (true)
+ {
+ // 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(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(RootMoves.begin() + PVIdx, RootMoves.end());
+
+ // Write PV back to transposition table in case the relevant
+ // entries have been overwritten during the search.
+ for (size_t i = 0; i <= PVIdx; i++)
+ RootMoves[i].insert_pv_in_tt(pos);
+
+ // If search has been stopped return immediately. Sorting and
+ // writing PV back to TT is safe becuase RootMoves is still
+ // valid, although refers to previous iteration.
+ if (Signals.stop)
+ return;
+
+ // In case of failing high/low increase aspiration window and
+ // research, otherwise exit the loop.
+ if (bestValue > alpha && bestValue < beta)
+ break;
+
+ // Give some update (without cluttering the UI) before to research
+ if (Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+
+ if (abs(bestValue) >= VALUE_KNOWN_WIN)
+ {
+ alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
+ }
+ else if (bestValue >= beta)
+ {
+ beta += delta;
+ delta += delta / 2;
+ }
+ else
+ {
+ Signals.failedLowAtRoot = true;
+ Signals.stopOnPonderhit = false;
+
+ alpha -= delta;
+ delta += delta / 2;
+ }
+
+ assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+ }
- // Retrieve max searched depth among threads
- selDepth = 0;
- for (int i = 0; i < Threads.size(); i++)
- if (Threads[i].maxPly > selDepth)
- selDepth = Threads[i].maxPly;
+ // Sort the PV lines searched so far and update the GUI
+ sort(RootMoves.begin(), RootMoves.begin() + PVIdx + 1);
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
+ }
- // 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, selDepth, alpha, beta, i) << endl;
+ // Do we need to pick now the sub-optimal best move ?
+ if (skill.enabled() && skill.time_to_pick(depth))
+ skill.pick_move();
- if (LogFile.is_open())
- LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
+ if (Options["Use Search Log"])
+ {
+ Log log(Options["Search Log Filename"]);
+ log << pretty_pv(pos, depth, bestValue, Time::now() - SearchTime, &RootMoves[0].pv[0])
+ << std::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;
+ // Filter out startup noise when monitoring best move stability
+ if (depth > 2 && BestMoveChanges)
+ bestMoveNeverChanged = false;
- // Check for some early stop condition
- if (!StopRequest && Limits.useTimeManagement())
+ // Do we have time for the next iteration? Can we stop searching now?
+ if (Limits.use_time_management() && !Signals.stopOnPonderhit)
{
- // Stop search early when the last two iterations returned a mate score
- if ( depth >= 5
- && abs(bestValues[depth]) >= VALUE_MATE_IN_PLY_MAX
- && abs(bestValues[depth - 1]) >= VALUE_MATE_IN_PLY_MAX)
- StopRequest = true;
-
- // Stop search early if one move seems to be much better than the
- // others or if there is only a single legal move. Also in the latter
- // case we search up to some depth 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
- && current_search_time() > TimeMgr.available_time() / 32)))
- StopRequest = true;
+ bool stop = false; // Local variable, not 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 (current_search_time() > (TimeMgr.available_time() * 62) / 100)
- StopRequest = true;
+ if (depth > 4 && depth < 50 && PVSize == 1)
+ TimeMgr.pv_instability(BestMoveChanges, prevBestMoveChanges);
+
+ // 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 (Time::now() - SearchTime > (TimeMgr.available_time() * 62) / 100)
+ stop = true;
+
+ // Stop search early if one move seems to be much better than others
+ if ( depth >= 12
+ && !stop
+ && PVSize == 1
+ && ( (bestMoveNeverChanged && pos.captured_piece_type())
+ || Time::now() - SearchTime > (TimeMgr.available_time() * 40) / 100))
+ {
+ Value rBeta = bestValue - 2 * PawnValueMg;
+ (ss+1)->excludedMove = RootMoves[0].pv[0];
+ (ss+1)->skipNullMove = true;
+ Value v = search(pos, ss+1, rBeta - 1, rBeta, (depth - 3) * ONE_PLY);
+ (ss+1)->skipNullMove = false;
+ (ss+1)->excludedMove = MOVE_NONE;
+
+ if (v < rBeta)
+ stop = true;
+ }
- // If we are allowed to ponder do not stop the search now but keep pondering
- if (StopRequest && Limits.ponder)
+ if (stop)
{
- StopRequest = false;
- StopOnPonderhit = true;
+ // 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;
}
}
}
-
- // 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);
-
- bestMove = skillBest;
- *ponderMove = skillPonder;
- }
-
- return bestMove;
}
@@ -701,72 +464,74 @@ namespace {
// here: This is taken care of after we return from the split point.
template
- Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
- const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV);
- const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV);
- const bool RootNode = (NT == Root);
+ 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.thread() >= 0 && pos.thread() < Threads.size());
+ assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
+ assert(PvNode || (alpha == beta - 1));
+ assert(depth > DEPTH_ZERO);
- Move movesSearched[MAX_MOVES];
- int64_t nodes;
+ Move movesSearched[64];
StateInfo st;
const TTEntry *tte;
+ SplitPoint* sp;
Key posKey;
- Move ttMove, move, excludedMove, threatMove;
+ Move ttMove, move, excludedMove, bestMove, threatMove;
Depth ext, newDepth;
- ValueType vt;
- Value bestValue, value, oldAlpha;
- Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
- bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous;
- int moveCount = 0, playedMoveCount = 0;
- Thread& thread = Threads[pos.thread()];
- SplitPoint* sp = NULL;
-
- refinedValue = bestValue = value = -VALUE_INFINITE;
- oldAlpha = alpha;
+ Value bestValue, value, ttValue;
+ Value eval, nullValue, futilityValue;
+ CheckType givesCheck;
+ bool inCheck, pvMove, singularExtensionNode;
+ bool captureOrPromotion, dangerous, doFullDepthSearch;
+ int moveCount, playedMoveCount;
+
+ // Step 1. Initialize node
+ Thread* thisThread = pos.this_thread();
+ moveCount = playedMoveCount = 0;
inCheck = pos.in_check();
- ss->ply = (ss-1)->ply + 1;
-
- // Used to send selDepth info to GUI
- if (PvNode && thread.maxPly < ss->ply)
- thread.maxPly = ss->ply;
if (SpNode)
{
sp = ss->sp;
+ bestMove = sp->bestMove;
+ threatMove = sp->threatMove;
+ bestValue = sp->bestValue;
tte = NULL;
ttMove = excludedMove = MOVE_NONE;
- threatMove = sp->threatMove;
+ ttValue = VALUE_NONE;
+
+ assert(sp->bestValue > -VALUE_INFINITE && sp->moveCount > 0);
+
goto split_point_start;
}
- // Step 1. Initialize node and poll. Polling can abort search
- ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
+ bestValue = -VALUE_INFINITE;
+ ss->currentMove = threatMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
+ ss->ply = (ss-1)->ply + 1;
(ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
- if (pos.thread() == 0 && ++NodesSincePoll > NodesBetweenPolls)
- {
- NodesSincePoll = 0;
- poll(pos);
- }
-
- // Step 2. Check for aborted search and immediate draw
- if (( StopRequest
- || pos.is_draw()
- || ss->ply > PLY_MAX) && !RootNode)
- return VALUE_DRAW;
+ // Used to send selDepth info to GUI
+ if (PvNode && thisThread->maxPly < ss->ply)
+ thisThread->maxPly = ss->ply;
- // Step 3. Mate distance pruning
if (!RootNode)
{
- alpha = Max(value_mated_in(ss->ply), alpha);
- beta = Min(value_mate_in(ss->ply+1), beta);
+ // Step 2. Check for aborted search and immediate draw
+ if (Signals.stop || pos.is_draw() || ss->ply > MAX_PLY)
+ return DrawValue[pos.side_to_move()];
+
+ // Step 3. Mate distance pruning. Even if we mate at the next move our score
+ // would be at best mate_in(ss->ply+1), but if alpha is already bigger because
+ // a shorter mate was found upward in the tree then there is no need to search
+ // further, we will never beat current alpha. Same logic but with reversed signs
+ // applies also in the opposite condition of being mated instead of giving mate,
+ // in this case return a fail-high score.
+ alpha = std::max(mated_in(ss->ply), alpha);
+ beta = std::min(mate_in(ss->ply+1), beta);
if (alpha >= beta)
return alpha;
}
@@ -775,53 +540,90 @@ namespace {
// 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.
excludedMove = ss->excludedMove;
- posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
-
+ posKey = excludedMove ? pos.exclusion_key() : pos.key();
tte = TT.probe(posKey);
- ttMove = tte ? tte->move() : MOVE_NONE;
+ ttMove = RootNode ? RootMoves[PVIdx].pv[0] : tte ? tte->move() : MOVE_NONE;
+ ttValue = tte ? value_from_tt(tte->value(), ss->ply) : VALUE_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.
- if (tte && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
- : ok_to_use_TT(tte, depth, beta, ss->ply)))
+ // 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
+ && tte->depth() >= depth
+ && ttValue != VALUE_NONE // Only in case of TT access race
+ && ( PvNode ? tte->type() == BOUND_EXACT
+ : ttValue >= beta ? (tte->type() & BOUND_LOWER)
+ : (tte->type() & BOUND_UPPER)))
{
TT.refresh(tte);
- ss->bestMove = ttMove; // Can be MOVE_NONE
- return value_from_tt(tte->value(), ss->ply);
+ ss->currentMove = ttMove; // Can be MOVE_NONE
+
+ if ( ttValue >= beta
+ && ttMove
+ && !pos.is_capture_or_promotion(ttMove)
+ && ttMove != ss->killers[0])
+ {
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = ttMove;
+ }
+ return ttValue;
}
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
- ss->eval = ss->evalMargin = VALUE_NONE;
+ ss->staticEval = ss->evalMargin = eval = VALUE_NONE;
+
else if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
+ // Following asserts are valid only in single thread condition because
+ // TT access is always racy and its contents cannot be trusted.
+ assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
+ assert(ttValue != VALUE_NONE || tte->type() == BOUND_NONE || Threads.size() > 1);
- ss->eval = tte->static_value();
+ ss->staticEval = eval = tte->static_value();
ss->evalMargin = tte->static_value_margin();
- refinedValue = refine_eval(tte, ss->eval, ss->ply);
+
+ if (eval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
+
+ // Can ttValue be used as a better position evaluation?
+ if (ttValue != VALUE_NONE)
+ if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
+ || ((tte->type() & BOUND_UPPER) && ttValue < eval))
+ eval = ttValue;
}
else
{
- refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
- TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
+ eval = ss->staticEval = evaluate(pos, ss->evalMargin);
+ TT.store(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
+ ss->staticEval, ss->evalMargin);
}
- // Save gain for the parent non-capture move
- 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)->staticEval != VALUE_NONE
+ && ss->staticEval != VALUE_NONE
+ && !pos.captured_piece_type()
+ && type_of(move) == NORMAL)
+ {
+ Square to = to_sq(move);
+ H.update_gain(pos.piece_on(to), to, -(ss-1)->staticEval - ss->staticEval);
+ }
// Step 6. Razoring (is omitted in PV nodes)
if ( !PvNode
- && depth < RazorDepth
+ && depth < 4 * ONE_PLY
&& !inCheck
- && refinedValue + razor_margin(depth) < beta
+ && eval + razor_margin(depth) < beta
&& ttMove == MOVE_NONE
- && abs(beta) < VALUE_MATE_IN_PLY_MAX
- && !pos.has_pawn_on_7th(pos.side_to_move()))
+ && abs(beta) < VALUE_MATE_IN_MAX_PLY
+ && !pos.pawn_on_7th(pos.side_to_move()))
{
Value rbeta = beta - razor_margin(depth);
- Value v = qsearch(pos, ss, rbeta-1, rbeta, DEPTH_ZERO);
+ Value v = qsearch(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.
@@ -833,42 +635,42 @@ namespace {
// the score by more than futility_margin(depth) if we do a null move.
if ( !PvNode
&& !ss->skipNullMove
- && depth < RazorDepth
+ && depth < 4 * ONE_PLY
&& !inCheck
- && refinedValue - futility_margin(depth, 0) >= beta
- && abs(beta) < VALUE_MATE_IN_PLY_MAX
+ && eval - FutilityMargins[depth][0] >= beta
+ && abs(beta) < VALUE_MATE_IN_MAX_PLY
&& pos.non_pawn_material(pos.side_to_move()))
- return refinedValue - futility_margin(depth, 0);
+ return eval - FutilityMargins[depth][0];
// Step 8. Null move search with verification search (is omitted in PV nodes)
if ( !PvNode
&& !ss->skipNullMove
&& depth > ONE_PLY
&& !inCheck
- && refinedValue >= beta
- && abs(beta) < VALUE_MATE_IN_PLY_MAX
+ && eval >= beta
+ && abs(beta) < VALUE_MATE_IN_MAX_PLY
&& pos.non_pawn_material(pos.side_to_move()))
{
ss->currentMove = MOVE_NULL;
// Null move dynamic reduction based on depth
- int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
+ Depth R = 3 * ONE_PLY + depth / 4;
// Null move dynamic reduction based on value
- if (refinedValue - PawnValueMidgame > beta)
- R++;
+ if (eval - PawnValueMg > beta)
+ R += ONE_PLY;
- pos.do_null_move(st);
+ pos.do_null_move(st);
(ss+1)->skipNullMove = true;
- nullValue = depth-R*ONE_PLY < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY);
+ nullValue = depth-R < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : - search(pos, ss+1, -beta, -alpha, depth-R);
(ss+1)->skipNullMove = false;
- pos.undo_null_move();
+ 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_MAX_PLY)
nullValue = beta;
if (depth < 6 * ONE_PLY)
@@ -876,7 +678,7 @@ namespace {
// Do verification search at high depths
ss->skipNullMove = true;
- Value v = search(pos, ss, alpha, beta, depth-R*ONE_PLY);
+ Value v = search(pos, ss, alpha, beta, depth-R);
ss->skipNullMove = false;
if (v >= beta)
@@ -890,12 +692,12 @@ namespace {
// 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).
- threatMove = (ss+1)->bestMove;
+ threatMove = (ss+1)->currentMove;
- if ( depth < ThreatDepth
+ if ( depth < 5 * ONE_PLY
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
- && connected_moves(pos, (ss-1)->currentMove, threatMove))
+ && yields_to_threat(pos, (ss-1)->currentMove, threatMove))
return beta - 1;
}
}
@@ -905,23 +707,26 @@ namespace {
// and a reduced search returns a value much above beta, we can (almost) safely
// prune the previous move.
if ( !PvNode
- && depth >= RazorDepth + ONE_PLY
+ && depth >= 5 * ONE_PLY
&& !inCheck
&& !ss->skipNullMove
&& excludedMove == MOVE_NONE
- && abs(beta) < VALUE_MATE_IN_PLY_MAX)
+ && abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
Value rbeta = beta + 200;
Depth rdepth = depth - ONE_PLY - 3 * ONE_PLY;
assert(rdepth >= ONE_PLY);
+ assert((ss-1)->currentMove != MOVE_NONE);
+ assert((ss-1)->currentMove != MOVE_NULL);
- MovePicker mp(pos, ttMove, H, Position::see_value(pos.captured_piece_type()));
+ MovePicker mp(pos, ttMove, H, pos.captured_piece_type());
CheckInfo ci(pos);
- while ((move = mp.get_next_move()) != MOVE_NONE)
+ while ((move = mp.next_move()) != MOVE_NONE)
if (pos.pl_move_is_legal(move, ci.pinned))
{
+ ss->currentMove = move;
pos.do_move(move, st, ci, pos.move_gives_check(move, ci));
value = -search(pos, ss+1, -rbeta, -rbeta+1, rdepth);
pos.undo_move(move);
@@ -931,9 +736,9 @@ namespace {
}
// Step 10. Internal iterative deepening
- if ( depth >= IIDDepth[PvNode]
+ if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
&& ttMove == MOVE_NONE
- && (PvNode || (!inCheck && ss->eval + IIDMargin >= beta)))
+ && (PvNode || (!inCheck && ss->staticEval + Value(256) >= beta)))
{
Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
@@ -947,100 +752,95 @@ namespace {
split_point_start: // At split points actual search starts from here
- // Initialize a MovePicker object for the current position
- MovePickerExt mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
+ MovePicker mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta);
CheckInfo ci(pos);
- ss->bestMove = MOVE_NONE;
- futilityBase = ss->eval + ss->evalMargin;
+ value = bestValue; // Workaround a bogus 'uninitialized' warning under gcc
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;
- }
+ && depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
+ && ttMove != MOVE_NONE
+ && !excludedMove // Recursive singular search is not allowed
+ && (tte->type() & BOUND_LOWER)
+ && tte->depth() >= depth - 3 * ONE_PLY;
// 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
- && !thread.cutoff_occurred())
+ while ((move = mp.next_move()) != MOVE_NONE)
{
- assert(move_is_ok(move));
+ assert(is_ok(move));
if (move == excludedMove)
continue;
- // At PV and SpNode nodes we want the moves to be legal
- if ((PvNode || SpNode) && !pos.pl_move_is_legal(move, ci.pinned))
+ // 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 && !std::count(RootMoves.begin() + PVIdx, RootMoves.end(), move))
continue;
if (SpNode)
{
+ // Shared counter cannot be decremented later if move turns out to be illegal
+ if (!pos.pl_move_is_legal(move, ci.pinned))
+ continue;
+
moveCount = ++sp->moveCount;
- lock_release(&(sp->lock));
+ sp->mutex.unlock();
}
else
moveCount++;
if (RootNode)
{
- // This is used by time management
- FirstRootMove = (moveCount == 1);
+ Signals.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;
+ if (thisThread == Threads.main_thread() && Time::now() - SearchTime > 2000)
+ sync_cout << "info depth " << depth / ONE_PLY
+ << " currmove " << move_to_uci(move, pos.is_chess960())
+ << " currmovenumber " << moveCount + PVIdx << sync_endl;
}
- // At Root and at first iteration do a PV search on all the moves to score root moves
- isPvMove = (PvNode && moveCount <= (RootNode ? depth <= ONE_PLY ? MAX_MOVES : MultiPV : 1));
+ ext = DEPTH_ZERO;
+ captureOrPromotion = pos.is_capture_or_promotion(move);
givesCheck = pos.move_gives_check(move, ci);
- captureOrPromotion = pos.move_is_capture(move) || move_is_promotion(move);
-
- // Step 12. Decide the new search depth
- ext = extension(pos, move, captureOrPromotion, givesCheck, &dangerous);
+ dangerous = givesCheck
+ || pos.is_passed_pawn_push(move)
+ || type_of(move) == CASTLE
+ || ( captureOrPromotion // Entering a pawn endgame?
+ && type_of(pos.piece_on(to_sq(move))) != PAWN
+ && type_of(move) == NORMAL
+ && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
+ - PieceValue[MG][pos.piece_on(to_sq(move))] == VALUE_ZERO));
+
+ // Step 12. Extend checks and, in PV nodes, also dangerous moves
+ if (PvNode && dangerous)
+ ext = ONE_PLY;
+
+ else if (givesCheck && (givesCheck == DISCO_CHECK || pos.see_sign(move) >= 0))
+ ext = 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 == ttMove
- && pos.pl_move_is_legal(move, ci.pinned)
- && ext < ONE_PLY)
+ if ( singularExtensionNode
+ && move == ttMove
+ && !ext
+ && pos.pl_move_is_legal(move, ci.pinned)
+ && abs(ttValue) < VALUE_KNOWN_WIN)
{
- Value ttValue = value_from_tt(tte->value(), ss->ply);
+ assert(ttValue != VALUE_NONE);
- if (abs(ttValue) < VALUE_KNOWN_WIN)
- {
- Value rBeta = ttValue - int(depth);
- ss->excludedMove = move;
- ss->skipNullMove = true;
- Value v = search(pos, ss, rBeta - 1, rBeta, depth / 2);
- ss->skipNullMove = false;
- ss->excludedMove = MOVE_NONE;
- ss->bestMove = MOVE_NONE;
- if (v < rBeta)
- ext = ONE_PLY;
- }
+ Value rBeta = ttValue - int(depth);
+ ss->excludedMove = move;
+ ss->skipNullMove = true;
+ value = search(pos, ss, rBeta - 1, rBeta, depth / 2);
+ ss->skipNullMove = false;
+ ss->excludedMove = MOVE_NONE;
+
+ if (value < rBeta)
+ ext = rBeta >= beta ? ONE_PLY + ONE_PLY / 2 : ONE_PLY;
}
// Update current move (this must be done after singular extension search)
@@ -1052,15 +852,16 @@ split_point_start: // At split points actual search starts from here
&& !inCheck
&& !dangerous
&& move != ttMove
- && !move_is_castle(move))
+ && (bestValue > VALUE_MATED_IN_MAX_PLY || ( bestValue == -VALUE_INFINITE
+ && alpha > VALUE_MATED_IN_MAX_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
+ if ( depth < 16 * ONE_PLY
+ && moveCount >= FutilityMoveCounts[depth]
+ && (!threatMove || !prevents_threat(pos, move, threatMove)))
{
if (SpNode)
- lock_grab(&(sp->lock));
+ sp->mutex.lock();
continue;
}
@@ -1069,30 +870,24 @@ split_point_start: // At split points actual search starts from here
// We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
// but fixing this made program slightly weaker.
Depth predictedDepth = newDepth - reduction(depth, moveCount);
- futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
- + H.gain(pos.piece_on(move_from(move)), move_to(move));
+ futilityValue = ss->staticEval + ss->evalMargin + futility_margin(predictedDepth, moveCount)
+ + H.gain(pos.piece_moved(move), to_sq(move));
- if (futilityValueScaled < beta)
+ if (futilityValue < beta)
{
if (SpNode)
- {
- lock_grab(&(sp->lock));
- if (futilityValueScaled > sp->bestValue)
- sp->bestValue = bestValue = futilityValueScaled;
- }
- else if (futilityValueScaled > bestValue)
- bestValue = futilityValueScaled;
+ sp->mutex.lock();
continue;
}
// Prune moves with negative SEE at low depths
if ( predictedDepth < 2 * ONE_PLY
- && bestValue > VALUE_MATED_IN_PLY_MAX
+ && givesCheck != DISCO_CHECK
&& pos.see_sign(move) < 0)
{
if (SpNode)
- lock_grab(&(sp->lock));
+ sp->mutex.lock();
continue;
}
@@ -1105,60 +900,53 @@ split_point_start: // At split points actual search starts from here
continue;
}
+ pvMove = PvNode ? moveCount == 1 : false;
ss->currentMove = move;
+ if (!SpNode && !captureOrPromotion && playedMoveCount < 64)
+ movesSearched[playedMoveCount++] = move;
// Step 14. Make the move
pos.do_move(move, st, ci, givesCheck);
- if (!SpNode && !captureOrPromotion)
- movesSearched[playedMoveCount++] = move;
-
- // Step extra. pv search (only in PV nodes)
- // The first move in list is the expected PV
- if (isPvMove)
- value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search(pos, ss+1, -beta, -alpha, newDepth);
- else
+ // Step 15. Reduced depth search (LMR). If the move fails high will be
+ // re-searched at full depth.
+ if ( depth > 3 * ONE_PLY
+ && !pvMove
+ && !captureOrPromotion
+ && !dangerous
+ && ss->killers[0] != move
+ && ss->killers[1] != move)
{
- // Step 15. Reduced depth search
- // If the move fails high will be re-searched at full depth.
- bool doFullDepthSearch = true;
+ ss->reduction = reduction(depth, moveCount);
+ Depth d = std::max(newDepth - ss->reduction, ONE_PLY);
alpha = SpNode ? sp->alpha : alpha;
- if ( depth > 3 * ONE_PLY
- && !captureOrPromotion
- && !dangerous
- && !move_is_castle(move)
- && ss->killers[0] != move
- && ss->killers[1] != move)
- {
- ss->reduction = reduction(depth, moveCount);
- if (ss->reduction)
- {
- Depth d = newDepth - ss->reduction;
- value = d < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search(pos, ss+1, -(alpha+1), -alpha, d);
- doFullDepthSearch = (value > alpha);
- }
- ss->reduction = DEPTH_ZERO; // Restore original reduction
- }
+ value = -search(pos, ss+1, -(alpha+1), -alpha, d);
- // Step 16. Full depth search
- if (doFullDepthSearch)
- {
- alpha = SpNode ? sp->alpha : alpha;
- value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search(pos, ss+1, -(alpha+1), -alpha, newDepth);
-
- // 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 && (RootNode || value < beta))
- value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search(pos, ss+1, -beta, -alpha, newDepth);
- }
+ doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO);
+ ss->reduction = DEPTH_ZERO;
+ }
+ else
+ doFullDepthSearch = !pvMove;
+
+ // Step 16. Full depth search, when LMR is skipped or fails high
+ if (doFullDepthSearch)
+ {
+ alpha = SpNode ? sp->alpha : alpha;
+ value = newDepth < ONE_PLY ?
+ givesCheck ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
+ : - search(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 && (pvMove || (value > alpha && (RootNode || value < beta))))
+ value = newDepth < ONE_PLY ?
+ givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
+ : - search(pos, ss+1, -beta, -alpha, newDepth);
// Step 17. Undo move
pos.undo_move(move);
@@ -1167,214 +955,223 @@ split_point_start: // At split points actual search starts from here
// Step 18. Check for new best move
if (SpNode)
{
- lock_grab(&(sp->lock));
+ sp->mutex.lock();
bestValue = sp->bestValue;
alpha = sp->alpha;
}
- if (value > bestValue && !(SpNode && thread.cutoff_occurred()))
- {
- bestValue = value;
-
- if (SpNode)
- sp->bestValue = value;
-
- if (!RootNode && value > alpha)
- {
- if (PvNode && value < beta) // We want always alpha < beta
- {
- alpha = value;
-
- if (SpNode)
- sp->alpha = value;
- }
- else if (SpNode)
- sp->is_betaCutoff = true;
-
- ss->bestMove = move;
-
- if (SpNode)
- sp->ss->bestMove = move;
- }
- }
+ // Finished searching the move. If Signals.stop 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 (Signals.stop || thisThread->cutoff_occurred())
+ return value; // To avoid returning VALUE_INFINITE
if (RootNode)
{
- // 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.current().nodes += pos.nodes_searched() - nodes;
+ RootMove& rm = *std::find(RootMoves.begin(), RootMoves.end(), move);
// PV move or new best move ?
- if (isPvMove || value > alpha)
+ if (pvMove || value > alpha)
{
- // Update PV
- ss->bestMove = move;
- mp.current().pv_score = value;
- mp.current().extract_pv_from_tt(pos);
+ 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++;
-
- // It is critical that sorting is done with a stable algorithm
- // becuase all the values but the first are usually set to
- // -VALUE_INFINITE and we want to keep the same order for all
- // the moves but the new PV that goes to head.
- Rml.sort_first(moveCount);
-
- // Update alpha. In multi-pv we don't use aspiration window, so set
- // alpha equal to minimum score among the PV lines searched so far.
- if (MultiPV > 1)
- alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score;
- else if (value > alpha)
- alpha = value;
+ if (!pvMove)
+ 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.
- mp.current().pv_score = -VALUE_INFINITE;
-
- } // RootNode
-
- // Step 19. Check for split
- if ( !RootNode
- && !SpNode
- && depth >= Threads.min_split_depth()
- && bestValue < beta
- && Threads.available_slave_exists(pos.thread())
- && !StopRequest
- && !thread.cutoff_occurred())
- Threads.split(pos, ss, &alpha, beta, &bestValue, depth,
- threatMove, moveCount, &mp, PvNode);
+ rm.score = -VALUE_INFINITE;
+ }
+
+ if (value > bestValue)
+ {
+ bestValue = value;
+ if (SpNode) sp->bestValue = value;
+
+ if (value > alpha)
+ {
+ bestMove = move;
+ if (SpNode) sp->bestMove = move;
+
+ if (PvNode && value < beta)
+ {
+ alpha = value; // Update alpha here! Always alpha < beta
+ if (SpNode) sp->alpha = value;
+ }
+ else // Fail high
+ {
+ if (SpNode) sp->cutoff = true;
+ break;
+ }
+ }
+ }
+
+ // Step 19. Check for splitting the search
+ if ( !SpNode
+ && depth >= Threads.min_split_depth()
+ && bestValue < beta
+ && Threads.available_slave_exists(thisThread))
+ {
+ bestValue = Threads.split(pos, ss, alpha, beta, bestValue, &bestMove,
+ depth, threatMove, moveCount, mp, NT);
+ if (bestValue >= beta)
+ break;
+ }
}
+ if (SpNode)
+ return bestValue;
+
// 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.
- // If one move was excluded return fail low score.
- if (!SpNode && !moveCount)
- return excludedMove ? oldAlpha : inCheck ? value_mated_in(ss->ply) : VALUE_DRAW;
-
- // Step 21. Update tables
- // If the search is not aborted, update the transposition table,
- // history counters, and killer moves.
- if (!SpNode && !StopRequest && !thread.cutoff_occurred())
+ // 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 Signals.stop 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.
+ // A split node has at least one move, the one tried before to be splitted.
+ if (!moveCount)
+ return excludedMove ? alpha
+ : inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
+
+ // If we have pruned all the moves without searching return a fail-low score
+ if (bestValue == -VALUE_INFINITE)
{
- move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
- vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
- : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
+ assert(!playedMoveCount);
- TT.store(posKey, value_to_tt(bestValue, ss->ply), vt, depth, move, ss->eval, ss->evalMargin);
+ bestValue = alpha;
+ }
- // Update killers and history only for non capture moves that fails high
- if ( bestValue >= beta
- && !pos.move_is_capture(move)
- && !move_is_promotion(move))
+ if (bestValue >= beta) // Failed high
+ {
+ TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth,
+ bestMove, ss->staticEval, ss->evalMargin);
+
+ if (!pos.is_capture_or_promotion(bestMove) && !inCheck)
{
- if (move != ss->killers[0])
+ if (bestMove != ss->killers[0])
{
ss->killers[1] = ss->killers[0];
- ss->killers[0] = move;
+ ss->killers[0] = bestMove;
}
- update_history(pos, move, depth, movesSearched, playedMoveCount);
- }
- }
- if (SpNode)
- {
- // Here we have the lock still grabbed
- sp->is_slave[pos.thread()] = false;
- sp->nodes += pos.nodes_searched();
- lock_release(&(sp->lock));
+ // Increase history value of the cut-off move
+ Value bonus = Value(int(depth) * int(depth));
+ H.add(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
+
+ // Decrease history of all the other played non-capture moves
+ for (int i = 0; i < playedMoveCount - 1; i++)
+ {
+ Move m = movesSearched[i];
+ H.add(pos.piece_moved(m), to_sq(m), -bonus);
+ }
+ }
}
+ else // Failed low or PV search
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval, ss->evalMargin);
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 ONE_PLY).
- template
- Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) {
+ template
+ 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.thread() >= 0 && pos.thread() < Threads.size());
+ assert(InCheck == pos.in_check());
+ assert(alpha >= -VALUE_INFINITE && alpha < beta && beta <= VALUE_INFINITE);
+ assert(PvNode || (alpha == beta - 1));
+ assert(depth <= DEPTH_ZERO);
StateInfo st;
- Move ttMove, move;
- Value bestValue, value, evalMargin, futilityValue, futilityBase;
- bool inCheck, enoughMaterial, givesCheck, evasionPrunable;
const TTEntry* tte;
+ Key posKey;
+ Move ttMove, move, bestMove;
+ Value bestValue, value, ttValue, futilityValue, futilityBase;
+ CheckType givesCheck;
+ bool enoughMaterial, evasionPrunable, fromNull;
Depth ttDepth;
- Value oldAlpha = alpha;
- ss->bestMove = ss->currentMove = MOVE_NONE;
+ ss->currentMove = bestMove = MOVE_NONE;
ss->ply = (ss-1)->ply + 1;
+ fromNull = (ss-1)->currentMove == MOVE_NULL;
// Check for an instant draw or maximum ply reached
- if (pos.is_draw() || 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);
+ if (pos.is_draw() || ss->ply > MAX_PLY)
+ return DrawValue[pos.side_to_move()];
// Transposition table lookup. At PV nodes, we don't use the TT for
// pruning, but only for move ordering.
- tte = TT.probe(pos.get_key());
- ttMove = (tte ? tte->move() : MOVE_NONE);
+ posKey = pos.key();
+ tte = TT.probe(posKey);
+ ttMove = tte ? tte->move() : MOVE_NONE;
+ ttValue = tte ? value_from_tt(tte->value(),ss->ply) : VALUE_NONE;
- if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ss->ply))
+ // 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.
+ ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
+ : DEPTH_QS_NO_CHECKS;
+ if ( tte
+ && tte->depth() >= ttDepth
+ && ttValue != VALUE_NONE // Only in case of TT access race
+ && ( PvNode ? tte->type() == BOUND_EXACT
+ : ttValue >= beta ? (tte->type() & BOUND_LOWER)
+ : (tte->type() & BOUND_UPPER)))
{
- ss->bestMove = ttMove; // Can be MOVE_NONE
- return value_from_tt(tte->value(), ss->ply);
+ ss->currentMove = ttMove; // Can be MOVE_NONE
+ return ttValue;
}
// Evaluate the position statically
- if (inCheck)
+ if (InCheck)
{
+ ss->staticEval = ss->evalMargin = VALUE_NONE;
bestValue = futilityBase = -VALUE_INFINITE;
- ss->eval = evalMargin = VALUE_NONE;
enoughMaterial = false;
}
else
{
- if (tte)
+ if (fromNull)
+ {
+ ss->staticEval = bestValue = -(ss-1)->staticEval;
+ ss->evalMargin = VALUE_ZERO;
+ }
+ else if (tte)
{
- assert(tte->static_value() != VALUE_NONE);
+ assert(tte->static_value() != VALUE_NONE || Threads.size() > 1);
- evalMargin = tte->static_value_margin();
- ss->eval = bestValue = tte->static_value();
+ ss->staticEval = bestValue = tte->static_value();
+ ss->evalMargin = tte->static_value_margin();
+
+ if (ss->staticEval == VALUE_NONE || ss->evalMargin == VALUE_NONE) // Due to a race
+ ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
}
else
- ss->eval = bestValue = evaluate(pos, evalMargin);
+ ss->staticEval = bestValue = evaluate(pos, ss->evalMargin);
// 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);
+ TT.store(pos.key(), value_to_tt(bestValue, ss->ply), BOUND_LOWER,
+ DEPTH_NONE, MOVE_NONE, ss->staticEval, ss->evalMargin);
return bestValue;
}
@@ -1382,43 +1179,43 @@ split_point_start: // At split points actual search starts from here
if (PvNode && bestValue > alpha)
alpha = bestValue;
- // Futility pruning parameters, not needed when in check
- futilityBase = ss->eval + evalMargin + FutilityMarginQS;
- enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
+ futilityBase = ss->staticEval + ss->evalMargin + Value(128);
+ enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMg;
}
// 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 >= DEPTH_QS_CHECKS) will
// be generated.
- MovePicker mp(pos, ttMove, depth, H, move_to((ss-1)->currentMove));
+ MovePicker mp(pos, ttMove, depth, H, to_sq((ss-1)->currentMove));
CheckInfo ci(pos);
// Loop through the moves until no moves remain or a beta cutoff occurs
- while ( alpha < beta
- && (move = mp.get_next_move()) != MOVE_NONE)
+ while ((move = mp.next_move()) != MOVE_NONE)
{
- assert(move_is_ok(move));
+ assert(is_ok(move));
givesCheck = pos.move_gives_check(move, ci);
// Futility pruning
if ( !PvNode
- && !inCheck
+ && !InCheck
&& !givesCheck
+ && !fromNull
&& move != ttMove
&& enoughMaterial
- && !move_is_promotion(move)
- && !pos.move_is_passed_pawn_push(move))
+ && type_of(move) != PROMOTION
+ && !pos.is_passed_pawn_push(move))
{
futilityValue = futilityBase
- + pos.endgame_value_of_piece_on(move_to(move))
- + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
+ + PieceValue[EG][pos.piece_on(to_sq(move))]
+ + (type_of(move) == ENPASSANT ? PawnValueEg : VALUE_ZERO);
- if (futilityValue < alpha)
+ if (futilityValue < beta)
{
if (futilityValue > bestValue)
bestValue = futilityValue;
+
continue;
}
@@ -1431,69 +1228,75 @@ split_point_start: // At split points actual search starts from here
// Detect non-capture evasions that are candidate to be pruned
evasionPrunable = !PvNode
- && inCheck
- && bestValue > VALUE_MATED_IN_PLY_MAX
- && !pos.move_is_capture(move)
+ && InCheck
+ && bestValue > VALUE_MATED_IN_MAX_PLY
+ && !pos.is_capture(move)
&& !pos.can_castle(pos.side_to_move());
// Don't search moves with negative SEE values
if ( !PvNode
- && (!inCheck || evasionPrunable)
+ && (!InCheck || evasionPrunable)
&& move != ttMove
- && !move_is_promotion(move)
+ && givesCheck != DISCO_CHECK
+ && type_of(move) != PROMOTION
&& pos.see_sign(move) < 0)
continue;
// Don't search useless checks
if ( !PvNode
- && !inCheck
+ && !InCheck
&& givesCheck
&& move != ttMove
- && !pos.move_is_capture(move)
- && !move_is_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;
-
+ && !pos.is_capture_or_promotion(move)
+ && ss->staticEval + PawnValueMg / 4 < beta
+ && !check_is_dangerous(pos, move, futilityBase, beta))
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, givesCheck);
- value = -qsearch(pos, ss+1, -beta, -alpha, depth-ONE_PLY);
+ value = givesCheck ? -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY)
+ : -qsearch(pos, ss+1, -beta, -alpha, depth - ONE_PLY);
pos.undo_move(move);
assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
- // New best move?
+ // Check for new best move
if (value > bestValue)
{
bestValue = value;
+
if (value > alpha)
{
- alpha = value;
- ss->bestMove = move;
+ if (PvNode && value < beta) // Update alpha here! Always alpha < beta
+ {
+ alpha = value;
+ bestMove = move;
+ }
+ else // Fail high
+ {
+ TT.store(posKey, value_to_tt(value, ss->ply), BOUND_LOWER,
+ ttDepth, move, ss->staticEval, ss->evalMargin);
+
+ return value;
+ }
}
}
}
// All legal moves have been searched. A special case: If we're in check
// and no legal moves were found, it is checkmate.
- if (inCheck && bestValue == -VALUE_INFINITE)
- return value_mated_in(ss->ply);
+ if (InCheck && bestValue == -VALUE_INFINITE)
+ return mated_in(ss->ply); // Plies to mate from the root
- // Update transposition table
- ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
- TT.store(pos.get_key(), value_to_tt(bestValue, ss->ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
+ ttDepth, bestMove, ss->staticEval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
@@ -1501,711 +1304,476 @@ split_point_start: // At split points actual search starts from here
}
- // 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.
-
- 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 = opposite_color(pos.side_to_move());
- ksq = pos.king_square(them);
- kingAtt = pos.attacks_from(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_of_color(them) & ~newAtt & ~(1ULL << to);
-
- if (!(b && (b & (b - 1))))
- return true;
-
- // Rule 2. Queen contact check is very dangerous
- if ( type_of_piece(pc) == QUEEN
- && bit_is_set(kingAtt, to))
- return true;
-
- // Rule 3. Creating new double threats with checks
- b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
-
- while (b)
- {
- victimSq = pop_1st_bit(&b);
- futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
-
- // Note that here we generate illegal "double move"!
- if ( futilityValue >= beta
- && pos.see_sign(make_move(from, victimSq)) >= 0)
- return true;
-
- if (futilityValue > bv)
- bv = futilityValue;
- }
-
- // Update bestValue only if check is not dangerous (because we will prune the move)
- *bestValue = bv;
- return false;
- }
-
-
- // connected_moves() tests whether two moves are 'connected' in the sense
- // that the first move somehow made the second move possible (for instance
- // if the moving piece is the same in both moves). The first move is assumed
- // to be the move that was made to reach the current position, while the
- // second move is assumed to be a move from the current position.
-
- bool connected_moves(const Position& pos, Move m1, Move m2) {
-
- Square f1, t1, f2, t2;
- Piece p;
-
- assert(m1 && move_is_ok(m1));
- assert(m2 && move_is_ok(m2));
-
- // Case 1: The moving piece is the same in both moves
- f2 = move_from(m2);
- t1 = move_to(m1);
- if (f2 == t1)
- return true;
-
- // Case 2: The destination square for m2 was vacated by m1
- t2 = move_to(m2);
- f1 = move_from(m1);
- if (t2 == f1)
- return true;
-
- // Case 3: Moving through the vacated square
- if ( piece_is_slider(pos.piece_on(f2))
- && 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))
- 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))
- {
- // 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))
- return true;
- }
- return false;
- }
-
-
// 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.
+ // "plies to mate from the current position". 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)
- return v + ply;
+ assert(v != VALUE_NONE);
- if (v <= VALUE_MATED_IN_PLY_MAX)
- return v - ply;
-
- return v;
+ return v >= VALUE_MATE_IN_MAX_PLY ? v + ply
+ : v <= VALUE_MATED_IN_MAX_PLY ? v - ply : v;
}
- // 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.
+ // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score
+ // from the transposition table (where refers to the plies to mate/be mated
+ // from current position) to "plies to mate/be mated from the root".
Value value_from_tt(Value v, int ply) {
- if (v >= VALUE_MATE_IN_PLY_MAX)
- return v - ply;
-
- if (v <= VALUE_MATED_IN_PLY_MAX)
- return v + ply;
-
- return v;
+ return v == VALUE_NONE ? VALUE_NONE
+ : v >= VALUE_MATE_IN_MAX_PLY ? v - ply
+ : v <= VALUE_MATED_IN_MAX_PLY ? v + ply : v;
}
- // connected_threat() tests whether it is safe to forward prune a move or if
- // 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_gives_check(m));
- assert(!pos.move_is_capture(m) && !move_is_promotion(m));
- assert(!pos.move_is_passed_pawn_push(m));
+ // check_is_dangerous() tests if a checking move can be pruned in qsearch()
- Square mfrom, mto, tfrom, tto;
-
- mfrom = move_from(m);
- mto = move_to(m);
- tfrom = move_from(threat);
- tto = move_to(threat);
-
- // Case 1: Don't prune moves which move the threatened piece
- if (mfrom == tto)
+ bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta)
+ {
+ Piece pc = pos.piece_moved(move);
+ Square from = from_sq(move);
+ Square to = to_sq(move);
+ Color them = ~pos.side_to_move();
+ Square ksq = pos.king_square(them);
+ Bitboard enemies = pos.pieces(them);
+ Bitboard kingAtt = pos.attacks_from(ksq);
+ Bitboard occ = pos.pieces() ^ from ^ ksq;
+ Bitboard oldAtt = pos.attacks_from(pc, from, occ);
+ Bitboard newAtt = pos.attacks_from(pc, to, occ);
+
+ // Checks which give opponent's king at most one escape square are dangerous
+ if (!more_than_one(kingAtt & ~(enemies | newAtt | to)))
return true;
- // Case 2: If the threatened piece has value less than or equal to the
- // 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)
- && pos.move_attacks_square(m, tto))
+ // Queen contact check is very dangerous
+ if (type_of(pc) == QUEEN && (kingAtt & to))
return true;
- // Case 3: If the moving piece in the threatened move is a slider, don't
- // prune safe moves which block its ray.
- if ( piece_is_slider(pos.piece_on(tfrom))
- && bit_is_set(squares_between(tfrom, tto), mto)
- && pos.see_sign(m) >= 0)
- return true;
+ // Creating new double threats with checks is dangerous
+ Bitboard b = (enemies ^ ksq) & newAtt & ~oldAtt;
+ while (b)
+ {
+ // Note that here we generate illegal "double move"!
+ if (futilityBase + PieceValue[EG][pos.piece_on(pop_lsb(&b))] >= beta)
+ return true;
+ }
return false;
}
- // ok_to_use_TT() returns true if a transposition table score
- // can be used at a given point in search.
-
- bool ok_to_use_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))
-
- && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
- || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
- }
-
-
- // refine_eval() returns the transposition table score if
- // possible otherwise falls back on static position evaluation.
-
- Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
+ // yields_to_threat() tests whether the move at previous ply yields to the so
+ // called threat move (the best move returned from a null search that fails
+ // low). Here 'yields to' means that the move somehow made the threat possible
+ // for instance if the moving piece is the same in both moves.
- assert(tte);
+ bool yields_to_threat(const Position& pos, Move move, Move threat) {
- Value v = value_from_tt(tte->value(), ply);
+ assert(is_ok(move));
+ assert(is_ok(threat));
+ assert(color_of(pos.piece_on(from_sq(threat))) == ~pos.side_to_move());
- if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
- || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
- return v;
+ Square mfrom = from_sq(move);
+ Square mto = to_sq(move);
+ Square tfrom = from_sq(threat);
+ Square tto = to_sq(threat);
- return defaultEval;
- }
-
-
- // update_history() registers a good move that produced a beta-cutoff
- // in history and marks as failures all the other moves of that ply.
+ // The piece is the same or threat's destination was vacated by the move
+ if (mto == tfrom || tto == mfrom)
+ return true;
- void update_history(const Position& pos, Move move, Depth depth,
- Move movesSearched[], int moveCount) {
- Move m;
- Value bonus = Value(int(depth) * int(depth));
+ // Threat moves through the vacated square
+ if (between_bb(tfrom, tto) & mfrom)
+ return true;
- H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
+ // Threat's destination is defended by the move's piece
+ Bitboard matt = pos.attacks_from(pos.piece_on(mto), mto, pos.pieces() ^ tfrom);
+ if (matt & tto)
+ return true;
- for (int i = 0; i < moveCount - 1; i++)
+ // Threat gives a discovered check through the move's checking piece
+ if (matt & pos.king_square(pos.side_to_move()))
{
- m = movesSearched[i];
-
- assert(m != move);
-
- H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
+ assert(between_bb(mto, pos.king_square(pos.side_to_move())) & tfrom);
+ return true;
}
- }
-
-
- // 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_type() == PIECE_TYPE_NONE
- && !move_is_special(m))
- H.update_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(int set) {
-
- static int searchStartTime;
-
- if (set)
- searchStartTime = set;
-
- return get_system_time() - searchStartTime;
- }
-
-
- // value_to_uci() converts a value to a string suitable for use with the UCI
- // protocol specifications:
- //
- // cp The score from the engine's point of view in centipawns.
- // mate Mate in y moves, not plies. If the engine is getting mated
- // use negative values for y.
-
- std::string value_to_uci(Value v) {
- std::stringstream s;
-
- 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 : -VALUE_MATE - v) / 2;
-
- return s.str();
+ return false;
}
- // speed_to_uci() returns a string with time stats of current search suitable
- // to be sent to UCI gui.
+ // prevents_threat() tests whether a move is able to defend against the so
+ // called threat move (the best move returned from a null search that fails
+ // low). In this case will not be pruned.
- std::string speed_to_uci(int64_t nodes) {
+ bool prevents_threat(const Position& pos, Move move, Move threat) {
- std::stringstream s;
- int t = current_search_time();
+ assert(is_ok(move));
+ assert(is_ok(threat));
+ assert(!pos.is_capture_or_promotion(move));
+ assert(!pos.is_passed_pawn_push(move));
- s << " nodes " << nodes
- << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
- << " time " << t;
+ Square mfrom = from_sq(move);
+ Square mto = to_sq(move);
+ Square tfrom = from_sq(threat);
+ Square tto = to_sq(threat);
- return s.str();
- }
-
-
- // 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(const Position& pos) {
-
- static int lastInfoTime;
- int t = current_search_time();
+ // Don't prune moves of the threatened piece
+ if (mfrom == tto)
+ return true;
- // Poll for input
- if (input_available())
+ // If the threatened piece has value less than or equal to the value of the
+ // threat piece, don't prune moves which defend it.
+ if ( pos.is_capture(threat)
+ && ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)]
+ || type_of(pos.piece_on(tfrom)) == KING))
{
- // We are line oriented, don't read single chars
- std::string command;
+ // Update occupancy as if the piece and the threat are moving
+ Bitboard occ = pos.pieces() ^ mfrom ^ mto ^ tfrom;
+ Piece piece = pos.piece_on(mfrom);
- if (!std::getline(std::cin, command) || command == "quit")
- {
- // Quit the program as soon as possible
- Limits.ponder = false;
- QuitRequest = StopRequest = true;
- return;
- }
- else if (command == "stop")
- {
- // Stop calculating as soon as possible, but still send the "bestmove"
- // and possibly the "ponder" token when finishing the search.
- Limits.ponder = false;
- StopRequest = true;
- }
- else if (command == "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.
- Limits.ponder = false;
-
- if (StopOnPonderhit)
- StopRequest = true;
- }
- }
-
- // 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;
+ // The moved piece attacks the square 'tto' ?
+ if (pos.attacks_from(piece, mto, occ) & tto)
+ return true;
- dbg_print_mean();
- dbg_print_hit_rate();
+ // Scan for possible X-ray attackers behind the moved piece
+ Bitboard xray = (attacks_bb< ROOK>(tto, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
+ | (attacks_bb(tto, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
- // Send info on searched nodes as soon as we return to root
- SendSearchedNodes = true;
+ // Verify attackers are triggered by our move and not already existing
+ if (xray && (xray ^ (xray & pos.attacks_from(tto))))
+ return true;
}
- // Should we stop the search?
- if (Limits.ponder)
- return;
-
- bool stillAtFirstMove = FirstRootMove
- && !AspirationFailLow
- && t > TimeMgr.available_time();
-
- bool noMoreTime = t > TimeMgr.maximum_time()
- || stillAtFirstMove;
-
- if ( (Limits.useTimeManagement() && noMoreTime)
- || (Limits.maxTime && t >= Limits.maxTime)
- || (Limits.maxNodes && pos.nodes_searched() >= Limits.maxNodes)) // FIXME
- StopRequest = true;
- }
-
-
- // 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.
-
- void wait_for_stop_or_ponderhit() {
-
- std::string command;
-
- // Wait for a command from stdin
- while ( std::getline(std::cin, command)
- && command != "ponderhit" && command != "stop" && command != "quit") {};
+ // Don't prune safe moves which block the threat path
+ if ((between_bb(tfrom, tto) & mto) && pos.see_sign(move) >= 0)
+ return true;
- if (command != "ponderhit" && command != "stop")
- QuitRequest = true; // Must be "quit" or getline() returned false
+ return false;
}
// 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) {
+ // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- assert(MultiPV > 1);
+ Move Skill::pick_move() {
static RKISS rk;
- // 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--)
+ // PRNG sequence should be not deterministic
+ for (int i = Time::now() % 50; i > 0; i--)
rk.rand();
- // 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,
+ // RootMoves are already sorted by score in descending order
+ int variance = std::min(RootMoves[0].score - RootMoves[PVSize - 1].score, PawnValueMg);
+ int weakness = 120 - 2 * level;
+ int max_s = -VALUE_INFINITE;
+ best = MOVE_NONE;
+
+ // Choose best move. For each move score we add two terms both dependent on
+ // weakness, 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++)
+ for (size_t i = 0; i < PVSize; i++)
{
- s = Rml[i].pv_score;
+ int s = RootMoves[i].score;
// Don't allow crazy blunders even at very low skills
- if (i > 0 && Rml[i-1].pv_score > s + EasyMoveMargin)
+ if (i > 0 && RootMoves[i-1].score > s + 2 * PawnValueMg)
break;
- // This is our magical formula
- s += ((max - s) * wk + var * (rk.rand() % wk)) / 128;
+ // This is our magic formula
+ s += ( weakness * int(RootMoves[0].score - s)
+ + variance * (rk.rand() % weakness)) / 128;
if (s > max_s)
{
max_s = s;
- *best = Rml[i].pv[0];
- *ponder = Rml[i].pv[1];
+ best = RootMoves[i].pv[0];
}
}
+ return best;
}
- /// RootMove and RootMoveList method's definitions
+ // uci_pv() formats PV information according to UCI protocol. UCI requires
+ // to send all the PV lines also if are still to be searched and so refer to
+ // the previous search score.
- RootMove::RootMove() {
+ string uci_pv(const Position& pos, int depth, Value alpha, Value beta) {
- nodes = 0;
- pv_score = non_pv_score = -VALUE_INFINITE;
- pv[0] = MOVE_NONE;
- }
-
- RootMove& RootMove::operator=(const RootMove& rm) {
-
- const Move* src = rm.pv;
- Move* dst = pv;
-
- // Avoid a costly full rm.pv[] copy
- do *dst++ = *src; while (*src++ != MOVE_NONE);
+ std::stringstream s;
+ Time::point elaspsed = Time::now() - SearchTime + 1;
+ size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
+ int selDepth = 0;
- nodes = rm.nodes;
- pv_score = rm.pv_score;
- non_pv_score = rm.non_pv_score;
- return *this;
- }
+ for (size_t i = 0; i < Threads.size(); i++)
+ if (Threads[i].maxPly > selDepth)
+ selDepth = Threads[i].maxPly;
- void RootMoveList::init(Position& pos, Move searchMoves[]) {
+ for (size_t i = 0; i < uciPVSize; i++)
+ {
+ bool updated = (i <= PVIdx);
- MoveStack mlist[MAX_MOVES];
- Move* sm;
+ if (depth == 1 && !updated)
+ continue;
- clear();
- bestMoveChanges = 0;
+ int d = updated ? depth : depth - 1;
+ Value v = updated ? RootMoves[i].score : RootMoves[i].prevScore;
- // Generate all legal moves and add them to RootMoveList
- MoveStack* last = generate(pos, mlist);
- for (MoveStack* cur = mlist; cur != last; cur++)
- {
- // If we have a searchMoves[] list then verify cur->move
- // is in the list before to add it.
- for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
+ if (s.rdbuf()->in_avail()) // Not at first line
+ s << "\n";
- if (searchMoves[0] && *sm != cur->move)
- continue;
+ s << "info depth " << d
+ << " seldepth " << selDepth
+ << " score " << (i == PVIdx ? score_to_uci(v, alpha, beta) : score_to_uci(v))
+ << " nodes " << pos.nodes_searched()
+ << " nps " << pos.nodes_searched() * 1000 / elaspsed
+ << " time " << elaspsed
+ << " multipv " << i + 1
+ << " pv";
- RootMove rm;
- rm.pv[0] = cur->move;
- rm.pv[1] = MOVE_NONE;
- rm.pv_score = -VALUE_INFINITE;
- push_back(rm);
+ for (size_t j = 0; RootMoves[i].pv[j] != MOVE_NONE; j++)
+ s << " " << move_to_uci(RootMoves[i].pv[j], pos.is_chess960());
}
- }
- // 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.
-
- void RootMove::extract_pv_from_tt(Position& pos) {
+ return s.str();
+ }
- StateInfo state[PLY_MAX_PLUS_2], *st = state;
- TTEntry* tte;
- int ply = 1;
+} // namespace
- assert(pv[0] != MOVE_NONE && pos.move_is_pl(pv[0]));
- pos.do_move(pv[0], *st++);
+/// RootMove::extract_pv_from_tt() builds a PV by adding moves from the TT table.
+/// We consider also failing high nodes and not only BOUND_EXACT nodes so to
+/// allow to always have a ponder move even when we fail high at root, and a
+/// long PV to print that is important for position analysis.
- while ( (tte = TT.probe(pos.get_key())) != NULL
- && tte->move() != MOVE_NONE
- && pos.move_is_pl(tte->move())
- && pos.pl_move_is_legal(tte->move(), pos.pinned_pieces(pos.side_to_move()))
- && ply < PLY_MAX
- && (!pos.is_draw() || ply < 2))
- {
- pv[ply] = tte->move();
- pos.do_move(pv[ply++], *st++);
- }
- pv[ply] = MOVE_NONE;
+void RootMove::extract_pv_from_tt(Position& pos) {
- do pos.undo_move(pv[--ply]); while (ply);
- }
+ StateInfo state[MAX_PLY_PLUS_2], *st = state;
+ TTEntry* tte;
+ int ply = 0;
+ Move m = pv[0];
- // 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.
+ pv.clear();
- void RootMove::insert_pv_in_tt(Position& pos) {
+ do {
+ pv.push_back(m);
- StateInfo state[PLY_MAX_PLUS_2], *st = state;
- TTEntry* tte;
- Key k;
- Value v, m = VALUE_NONE;
- int ply = 0;
+ assert(pos.move_is_legal(pv[ply]));
+ pos.do_move(pv[ply++], *st++);
+ tte = TT.probe(pos.key());
- assert(pv[0] != MOVE_NONE && pos.move_is_pl(pv[0]));
+ } while ( tte
+ && pos.is_pseudo_legal(m = tte->move()) // Local copy, TT could change
+ && pos.pl_move_is_legal(m, pos.pinned_pieces())
+ && ply < MAX_PLY
+ && (!pos.is_draw() || ply < 2));
- do {
- k = pos.get_key();
- tte = TT.probe(k);
+ pv.push_back(MOVE_NONE); // Must be zero-terminating
- // 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++);
+ while (ply) pos.undo_move(pv[--ply]);
+}
- } while (pv[++ply] != MOVE_NONE);
- do pos.undo_move(pv[--ply]); while (ply);
- }
+/// RootMove::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.
- // pv_info_to_uci() returns a string with information on the current PV line
- // formatted according to UCI specification.
+void RootMove::insert_pv_in_tt(Position& pos) {
- std::string RootMove::pv_info_to_uci(Position& pos, int depth, int selDepth, Value alpha,
- Value beta, int pvIdx) {
- std::stringstream s;
+ StateInfo state[MAX_PLY_PLUS_2], *st = state;
+ TTEntry* tte;
+ int ply = 0;
+ Value v, m;
- s << "info depth " << depth
- << " seldepth " << selDepth
- << " multipv " << pvIdx + 1
- << " score " << value_to_uci(pv_score)
- << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
- << speed_to_uci(pos.nodes_searched())
- << " pv ";
+ do {
+ tte = TT.probe(pos.key());
- for (Move* m = pv; *m != MOVE_NONE; m++)
- s << *m << " ";
+ if (!tte || tte->move() != pv[ply]) // Don't overwrite correct entries
+ {
+ if (pos.in_check())
+ v = m = VALUE_NONE;
+ else
+ v = evaluate(pos, m);
- return s.str();
- }
+ TT.store(pos.key(), VALUE_NONE, BOUND_NONE, DEPTH_NONE, pv[ply], v, m);
+ }
- // Specializations for MovePickerExt in case of Root node
- MovePickerExt::MovePickerExt(const Position& p, Move ttm, Depth d,
- const History& h, SearchStack* ss, Value b)
- : MovePicker(p, ttm, d, h, ss, b), cur(-1) {
- Move move;
- Value score = VALUE_ZERO;
-
- // 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 (RootMoveList::iterator rm = Rml.begin(); rm != Rml.end(); ++rm)
- if (rm->pv[0] == move)
- {
- rm->non_pv_score = score--;
- break;
- }
+ assert(pos.move_is_legal(pv[ply]));
+ pos.do_move(pv[ply++], *st++);
- Rml.sort();
- }
+ } while (pv[ply] != MOVE_NONE);
-} // namespace
+ while (ply) pos.undo_move(pv[--ply]);
+}
-// ThreadsManager::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.
+/// Thread::idle_loop() is where the thread is parked when it has no work to do
-void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
+void Thread::idle_loop() {
- assert(threadID >= 0 && threadID < MAX_THREADS);
+ // Pointer 'sp_master', if non-NULL, points to the active SplitPoint
+ // object for which the thread is the master.
+ const SplitPoint* sp_master = splitPointsCnt ? curSplitPoint : NULL;
- int i;
- bool allFinished;
+ assert(!sp_master || (sp_master->master == this && is_searching));
- while (true)
+ // 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.
+ while (!sp_master || sp_master->slavesMask)
{
- // 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;
- }
-
- // If we are not thinking, wait for a condition to be signaled
+ // If we are not searching, wait for a condition to be signaled
// instead of wasting CPU time polling for work.
- while ( threadID >= activeThreads
- || threads[threadID].state == Thread::INITIALIZING
- || (useSleepingThreads && threads[threadID].state == Thread::AVAILABLE))
+ while ( do_sleep
+ || do_exit
+ || (!is_searching && Threads.use_sleeping_threads()))
{
- assert(!sp || useSleepingThreads);
- assert(threadID != 0 || useSleepingThreads);
-
- if (threads[threadID].state == Thread::INITIALIZING)
- threads[threadID].state = Thread::AVAILABLE;
+ if (do_exit)
+ {
+ assert(!sp_master);
+ return;
+ }
// Grab the lock to avoid races with Thread::wake_up()
- lock_grab(&threads[threadID].sleepLock);
-
- // If we are master and all slaves have finished do not go to sleep
- for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
- allFinished = (i == activeThreads);
+ mutex.lock();
- if (allFinished || allThreadsShouldExit)
+ // If we are master and all slaves have finished don't go to sleep
+ if (sp_master && !sp_master->slavesMask)
{
- lock_release(&threads[threadID].sleepLock);
+ mutex.unlock();
break;
}
- // Do sleep here after retesting sleep conditions
- if (threadID >= activeThreads || threads[threadID].state == Thread::AVAILABLE)
- cond_wait(&threads[threadID].sleepCond, &threads[threadID].sleepLock);
+ // 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)
+ sleepCondition.wait(mutex);
- lock_release(&threads[threadID].sleepLock);
+ mutex.unlock();
}
// If this thread has been assigned work, launch a search
- if (threads[threadID].state == Thread::WORKISWAITING)
+ if (is_searching)
{
- assert(!allThreadsShouldExit);
+ assert(!do_sleep && !do_exit);
+
+ Threads.mutex.lock();
+
+ assert(is_searching);
+ SplitPoint* sp = curSplitPoint;
+
+ Threads.mutex.unlock();
- threads[threadID].state = Thread::SEARCHING;
+ Stack ss[MAX_PLY_PLUS_2];
+ Position pos(*sp->pos, this);
- // Copy split point 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);
+ memcpy(ss, sp->ss - 1, 4 * sizeof(Stack));
+ (ss+1)->sp = sp;
- memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
- (ss+1)->sp = tsp;
+ sp->mutex.lock();
- if (tsp->pvNode)
- search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ assert(sp->activePositions[idx] == NULL);
+
+ sp->activePositions[idx] = &pos;
+
+ if (sp->nodeType == Root)
+ search(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ else if (sp->nodeType == PV)
+ search(pos, ss+1, sp->alpha, sp->beta, sp->depth);
+ else if (sp->nodeType == NonPV)
+ search(pos, ss+1, sp->alpha, sp->beta, sp->depth);
else
- search(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth);
+ assert(false);
- assert(threads[threadID].state == Thread::SEARCHING);
+ assert(is_searching);
- threads[threadID].state = Thread::AVAILABLE;
+ is_searching = false;
+ sp->activePositions[idx] = NULL;
+ sp->slavesMask &= ~(1ULL << idx);
+ sp->nodes += pos.nodes_searched();
// 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 ( useSleepingThreads
- && threadID != tsp->master
- && threads[tsp->master].state == Thread::AVAILABLE)
- threads[tsp->master].wake_up();
+ if ( Threads.use_sleeping_threads()
+ && this != sp->master
+ && !sp->slavesMask)
+ {
+ assert(!sp->master->is_searching);
+ sp->master->wake_up();
+ }
+
+ // After releasing the lock we cannot access anymore any SplitPoint
+ // related data in a safe way becuase it could have been released under
+ // our feet by the sp master. Also accessing other Thread objects is
+ // unsafe because if we are exiting there is a chance are already freed.
+ sp->mutex.unlock();
}
+ }
+}
- // 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.
- for (i = 0; sp && i < activeThreads && !sp->is_slave[i]; i++) {}
- allFinished = (i == activeThreads);
- if (allFinished)
- {
- // 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));
+/// check_time() is called by the timer thread when the timer triggers. It is
+/// used to print debug info and, more important, to detect when we are out of
+/// available time and so stop the search.
- // In helpful master concept a master can help only a sub-tree, and
- // because here is all finished is not possible master is booked.
- assert(threads[threadID].state == Thread::AVAILABLE);
+void check_time() {
- threads[threadID].state = Thread::SEARCHING;
- return;
- }
+ static Time::point lastInfoTime = Time::now();
+ int64_t nodes = 0; // Workaround silly 'uninitialized' gcc warning
+
+ if (Time::now() - lastInfoTime >= 1000)
+ {
+ lastInfoTime = Time::now();
+ dbg_print();
+ }
+
+ if (Limits.ponder)
+ return;
+
+ if (Limits.nodes)
+ {
+ Threads.mutex.lock();
+
+ nodes = RootPos.nodes_searched();
+
+ // Loop across all split points and sum accumulated SplitPoint nodes plus
+ // all the currently active slaves positions.
+ for (size_t i = 0; i < Threads.size(); i++)
+ for (int j = 0; j < Threads[i].splitPointsCnt; j++)
+ {
+ SplitPoint& sp = Threads[i].splitPoints[j];
+
+ sp.mutex.lock();
+
+ nodes += sp.nodes;
+ Bitboard sm = sp.slavesMask;
+ while (sm)
+ {
+ Position* pos = sp.activePositions[pop_lsb(&sm)];
+ nodes += pos ? pos->nodes_searched() : 0;
+ }
+
+ sp.mutex.unlock();
+ }
+
+ Threads.mutex.unlock();
}
+
+ Time::point elapsed = Time::now() - SearchTime;
+ bool stillAtFirstMove = Signals.firstRootMove
+ && !Signals.failedLowAtRoot
+ && elapsed > TimeMgr.available_time();
+
+ bool noMoreTime = elapsed > TimeMgr.maximum_time() - 2 * TimerResolution
+ || stillAtFirstMove;
+
+ if ( (Limits.use_time_management() && noMoreTime)
+ || (Limits.movetime && elapsed >= Limits.movetime)
+ || (Limits.nodes && nodes >= Limits.nodes))
+ Signals.stop = true;
}