2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
45 #include "ucioption.h"
51 //// Local definitions
57 enum NodeType { NonPV, PV };
59 // Set to true to force running with one thread.
60 // Used for debugging SMP code.
61 const bool FakeSplit = false;
63 // Fast lookup table of sliding pieces indexed by Piece
64 const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
65 inline bool piece_is_slider(Piece p) { return Slidings[p]; }
67 // ThreadsManager class is used to handle all the threads related stuff in search,
68 // init, starting, parking and, the most important, launching a slave thread at a
69 // split point are what this class does. All the access to shared thread data is
70 // done through this class, so that we avoid using global variables instead.
72 class ThreadsManager {
73 /* As long as the single ThreadsManager object is defined as a global we don't
74 need to explicitly initialize to zero its data members because variables with
75 static storage duration are automatically set to zero before enter main()
81 int min_split_depth() const { return minimumSplitDepth; }
82 int active_threads() const { return activeThreads; }
83 void set_active_threads(int cnt) { activeThreads = cnt; }
85 void read_uci_options();
86 bool available_thread_exists(int master) const;
87 bool thread_is_available(int slave, int master) const;
88 bool cutoff_at_splitpoint(int threadID) const;
89 void wake_sleeping_thread(int threadID);
90 void idle_loop(int threadID, SplitPoint* sp);
93 void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
94 Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
97 Depth minimumSplitDepth;
98 int maxThreadsPerSplitPoint;
99 bool useSleepingThreads;
101 volatile bool allThreadsShouldExit;
102 Thread threads[MAX_THREADS];
103 Lock mpLock, sleepLock[MAX_THREADS];
104 WaitCondition sleepCond[MAX_THREADS];
108 // RootMove struct is used for moves at the root at the tree. For each root
109 // move, we store two scores, a node count, and a PV (really a refutation
110 // in the case of moves which fail low). Value pv_score is normally set at
111 // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
112 // according to the order in which moves are returned by MovePicker.
117 RootMove(const RootMove& rm) { *this = rm; }
118 RootMove& operator=(const RootMove& rm);
120 // RootMove::operator<() is the comparison function used when
121 // sorting the moves. A move m1 is considered to be better
122 // than a move m2 if it has an higher pv_score, or if it has
123 // equal pv_score but m1 has the higher non_pv_score. In this
124 // way we are guaranteed that PV moves are always sorted as first.
125 bool operator<(const RootMove& m) const {
126 return pv_score != m.pv_score ? pv_score < m.pv_score
127 : non_pv_score < m.non_pv_score;
130 void extract_pv_from_tt(Position& pos);
131 void insert_pv_in_tt(Position& pos);
132 std::string pv_info_to_uci(Position& pos, Value alpha, Value beta, int pvLine = 0);
137 Move pv[PLY_MAX_PLUS_2];
141 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
142 // with an handful of methods above the standard ones.
144 struct RootMoveList : public std::vector<RootMove> {
146 typedef std::vector<RootMove> Base;
148 RootMoveList(Position& pos, Move searchMoves[]);
149 void set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss);
151 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
152 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
156 // When formatting a move for std::cout we must know if we are in Chess960
157 // or not. To keep using the handy operator<<() on the move the trick is to
158 // embed this flag in the stream itself. Function-like named enum set960 is
159 // used as a custom manipulator and the stream internal general-purpose array,
160 // accessed through ios_base::iword(), is used to pass the flag to the move's
161 // operator<<() that will use it to properly format castling moves.
164 std::ostream& operator<< (std::ostream& os, const set960& f) {
166 os.iword(0) = int(f);
171 // Overload operator << for moves to make it easier to print moves in
172 // coordinate notation compatible with UCI protocol.
173 std::ostream& operator<<(std::ostream& os, Move m) {
175 bool chess960 = (os.iword(0) != 0); // See set960()
176 return os << move_to_uci(m, chess960);
184 // Maximum depth for razoring
185 const Depth RazorDepth = 4 * ONE_PLY;
187 // Dynamic razoring margin based on depth
188 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
190 // Maximum depth for use of dynamic threat detection when null move fails low
191 const Depth ThreatDepth = 5 * ONE_PLY;
193 // Step 9. Internal iterative deepening
195 // Minimum depth for use of internal iterative deepening
196 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
198 // At Non-PV nodes we do an internal iterative deepening search
199 // when the static evaluation is bigger then beta - IIDMargin.
200 const Value IIDMargin = Value(0x100);
202 // Step 11. Decide the new search depth
204 // Extensions. Configurable UCI options
205 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
206 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
207 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
209 // Minimum depth for use of singular extension
210 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
212 // If the TT move is at least SingularExtensionMargin better then the
213 // remaining ones we will extend it.
214 const Value SingularExtensionMargin = Value(0x20);
216 // Step 12. Futility pruning
218 // Futility margin for quiescence search
219 const Value FutilityMarginQS = Value(0x80);
221 // Futility lookup tables (initialized at startup) and their getter functions
222 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
223 int FutilityMoveCountArray[32]; // [depth]
225 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
226 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
228 // Step 14. Reduced search
230 // Reduction lookup tables (initialized at startup) and their getter functions
231 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
233 template <NodeType PV>
234 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
236 // Common adjustments
238 // Search depth at iteration 1
239 const Depth InitialDepth = ONE_PLY;
241 // Easy move margin. An easy move candidate must be at least this much
242 // better than the second best move.
243 const Value EasyMoveMargin = Value(0x200);
246 /// Namespace variables
254 // Scores and number of times the best move changed for each iteration
255 Value ValueByIteration[PLY_MAX_PLUS_2];
256 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
258 // Search window management
264 // Time managment variables
265 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
266 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
267 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
272 std::ofstream LogFile;
274 // Multi-threads manager object
275 ThreadsManager ThreadsMgr;
277 // Node counters, used only by thread[0] but try to keep in different cache
278 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
279 bool SendSearchedNodes;
281 int NodesBetweenPolls = 30000;
288 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
289 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
291 template <NodeType PvNode, bool SpNode>
292 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
294 template <NodeType PvNode>
295 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
297 template <NodeType PvNode>
298 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
300 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
301 : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
304 template <NodeType PvNode>
305 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
307 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
308 bool connected_moves(const Position& pos, Move m1, Move m2);
309 bool value_is_mate(Value value);
310 Value value_to_tt(Value v, int ply);
311 Value value_from_tt(Value v, int ply);
312 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
313 bool connected_threat(const Position& pos, Move m, Move threat);
314 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
315 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
316 void update_killers(Move m, Move killers[]);
317 void update_gains(const Position& pos, Move move, Value before, Value after);
319 int current_search_time();
320 std::string value_to_uci(Value v);
321 int nps(const Position& pos);
322 void poll(const Position& pos);
323 void wait_for_stop_or_ponderhit();
324 void init_ss_array(SearchStack* ss, int size);
326 #if !defined(_MSC_VER)
327 void* init_thread(void* threadID);
329 DWORD WINAPI init_thread(LPVOID threadID);
339 /// init_threads(), exit_threads() and nodes_searched() are helpers to
340 /// give accessibility to some TM methods from outside of current file.
342 void init_threads() { ThreadsMgr.init_threads(); }
343 void exit_threads() { ThreadsMgr.exit_threads(); }
346 /// init_search() is called during startup. It initializes various lookup tables
350 int d; // depth (ONE_PLY == 2)
351 int hd; // half depth (ONE_PLY == 1)
354 // Init reductions array
355 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
357 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
358 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
359 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
360 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
363 // Init futility margins array
364 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
365 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
367 // Init futility move count array
368 for (d = 0; d < 32; d++)
369 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
373 /// perft() is our utility to verify move generation is bug free. All the legal
374 /// moves up to given depth are generated and counted and the sum returned.
376 int64_t perft(Position& pos, Depth depth)
378 MoveStack mlist[MOVES_MAX];
383 // Generate all legal moves
384 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
386 // If we are at the last ply we don't need to do and undo
387 // the moves, just to count them.
388 if (depth <= ONE_PLY)
389 return int(last - mlist);
391 // Loop through all legal moves
393 for (MoveStack* cur = mlist; cur != last; cur++)
396 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
397 sum += perft(pos, depth - ONE_PLY);
404 /// think() is the external interface to Stockfish's search, and is called when
405 /// the program receives the UCI 'go' command. It initializes various
406 /// search-related global variables, and calls root_search(). It returns false
407 /// when a quit command is received during the search.
409 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
410 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
412 // Initialize global search variables
413 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
415 SearchStartTime = get_system_time();
416 ExactMaxTime = maxTime;
419 InfiniteSearch = infinite;
421 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
423 // Look for a book move, only during games, not tests
424 if (UseTimeManagement && Options["OwnBook"].value<bool>())
426 if (Options["Book File"].value<std::string>() != OpeningBook.name())
427 OpeningBook.open(Options["Book File"].value<std::string>());
429 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
430 if (bookMove != MOVE_NONE)
433 wait_for_stop_or_ponderhit();
435 cout << "bestmove " << bookMove << endl;
440 // Read UCI option values
441 TT.set_size(Options["Hash"].value<int>());
442 if (Options["Clear Hash"].value<bool>())
444 Options["Clear Hash"].set_value("false");
448 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
449 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
450 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
451 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
452 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
453 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
454 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
455 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
456 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
457 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
458 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
459 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
460 MultiPV = Options["MultiPV"].value<int>();
461 UseLogFile = Options["Use Search Log"].value<bool>();
463 read_evaluation_uci_options(pos.side_to_move());
465 // Set the number of active threads
466 ThreadsMgr.read_uci_options();
467 init_eval(ThreadsMgr.active_threads());
469 // Wake up needed threads
470 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
471 ThreadsMgr.wake_sleeping_thread(i);
474 int myTime = time[pos.side_to_move()];
475 int myIncrement = increment[pos.side_to_move()];
476 if (UseTimeManagement)
477 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
479 // Set best NodesBetweenPolls interval to avoid lagging under
480 // heavy time pressure.
482 NodesBetweenPolls = Min(MaxNodes, 30000);
483 else if (myTime && myTime < 1000)
484 NodesBetweenPolls = 1000;
485 else if (myTime && myTime < 5000)
486 NodesBetweenPolls = 5000;
488 NodesBetweenPolls = 30000;
490 // Write search information to log file
493 std::string name = Options["Search Log Filename"].value<std::string>();
494 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
496 LogFile << "Searching: " << pos.to_fen()
497 << "\ninfinite: " << infinite
498 << " ponder: " << ponder
499 << " time: " << myTime
500 << " increment: " << myIncrement
501 << " moves to go: " << movesToGo << endl;
504 // We're ready to start thinking. Call the iterative deepening loop function
505 Move ponderMove = MOVE_NONE;
506 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
508 // Print final search statistics
509 cout << "info nodes " << pos.nodes_searched()
510 << " nps " << nps(pos)
511 << " time " << current_search_time() << endl;
515 LogFile << "\nNodes: " << pos.nodes_searched()
516 << "\nNodes/second: " << nps(pos)
517 << "\nBest move: " << move_to_san(pos, bestMove);
520 pos.do_move(bestMove, st);
521 LogFile << "\nPonder move: "
522 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
525 // Return from think() with unchanged position
526 pos.undo_move(bestMove);
531 // This makes all the threads to go to sleep
532 ThreadsMgr.set_active_threads(1);
534 // If we are pondering or in infinite search, we shouldn't print the
535 // best move before we are told to do so.
536 if (!StopRequest && (Pondering || InfiniteSearch))
537 wait_for_stop_or_ponderhit();
539 // Could be both MOVE_NONE when searching on a stalemate position
540 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
548 // id_loop() is the main iterative deepening loop. It calls root_search
549 // repeatedly with increasing depth until the allocated thinking time has
550 // been consumed, the user stops the search, or the maximum search depth is
553 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
555 SearchStack ss[PLY_MAX_PLUS_2];
557 Move EasyMove = MOVE_NONE;
558 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
560 // Moves to search are verified, scored and sorted
561 RootMoveList rml(pos, searchMoves);
563 // Handle special case of searching on a mate/stale position
566 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
568 cout << "info depth " << 1
569 << " score " << value_to_uci(s) << endl;
577 init_ss_array(ss, PLY_MAX_PLUS_2);
578 ValueByIteration[1] = rml[0].pv_score;
581 // Send initial RootMoveList scoring (iteration 1)
582 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
583 << "info depth " << Iteration
584 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
586 // Is one move significantly better than others after initial scoring ?
588 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
589 EasyMove = rml[0].pv[0];
591 // Iterative deepening loop
592 while (Iteration < PLY_MAX)
594 // Initialize iteration
596 BestMoveChangesByIteration[Iteration] = 0;
598 cout << "info depth " << Iteration << endl;
600 // Calculate dynamic aspiration window based on previous iterations
601 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
603 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
604 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
606 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
607 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
609 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
610 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
613 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
615 // Search to the current depth, rml is updated and sorted
616 value = root_search(pos, ss, alpha, beta, depth, rml);
619 break; // Value cannot be trusted. Break out immediately!
621 //Save info about search result
622 ValueByIteration[Iteration] = value;
624 // Drop the easy move if differs from the new best move
625 if (rml[0].pv[0] != EasyMove)
626 EasyMove = MOVE_NONE;
628 if (UseTimeManagement)
631 bool stopSearch = false;
633 // Stop search early if there is only a single legal move,
634 // we search up to Iteration 6 anyway to get a proper score.
635 if (Iteration >= 6 && rml.size() == 1)
638 // Stop search early when the last two iterations returned a mate score
640 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
641 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
644 // Stop search early if one move seems to be much better than the others
646 && EasyMove == rml[0].pv[0]
647 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
648 && current_search_time() > TimeMgr.available_time() / 16)
649 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
650 && current_search_time() > TimeMgr.available_time() / 32)))
653 // Add some extra time if the best move has changed during the last two iterations
654 if (Iteration > 5 && Iteration <= 50)
655 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
656 BestMoveChangesByIteration[Iteration-1]);
658 // Stop search if most of MaxSearchTime is consumed at the end of the
659 // iteration. We probably don't have enough time to search the first
660 // move at the next iteration anyway.
661 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
667 StopOnPonderhit = true;
673 if (MaxDepth && Iteration >= MaxDepth)
677 *ponderMove = rml[0].pv[1];
682 // root_search() is the function which searches the root node. It is
683 // similar to search_pv except that it prints some information to the
684 // standard output and handles the fail low/high loops.
686 Value root_search(Position& pos, SearchStack* ss, Value alpha,
687 Value beta, Depth depth, RootMoveList& rml) {
689 Move movesSearched[MOVES_MAX];
694 Value value, oldAlpha;
695 RootMoveList::iterator rm;
696 bool isCheck, moveIsCheck, captureOrPromotion, dangerous, isPvMove;
697 int moveCount, researchCountFH, researchCountFL;
699 researchCountFH = researchCountFL = 0;
701 isCheck = pos.is_check();
703 // Step 1. Initialize node (polling is omitted at root)
704 ss->currentMove = ss->bestMove = MOVE_NONE;
705 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
707 // Step 2. Check for aborted search (omitted at root)
708 // Step 3. Mate distance pruning (omitted at root)
709 // Step 4. Transposition table lookup (omitted at root)
711 // Step 5. Evaluate the position statically
712 // At root we do this only to get reference value for child nodes
713 ss->evalMargin = VALUE_NONE;
714 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
716 // Step 6. Razoring (omitted at root)
717 // Step 7. Static null move pruning (omitted at root)
718 // Step 8. Null move search with verification search (omitted at root)
719 // Step 9. Internal iterative deepening (omitted at root)
721 // Step extra. Fail low loop
722 // We start with small aspiration window and in case of fail low, we research
723 // with bigger window until we are not failing low anymore.
726 // Sort the moves before to (re)search
727 rml.set_non_pv_scores(pos, rml[0].pv[0], ss);
731 // Step 10. Loop through all moves in the root move list
732 for (rm = rml.begin(); rm != rml.end() && !StopRequest; ++rm)
734 // This is used by time management
735 FirstRootMove = (rm == rml.begin());
737 // Save the current node count before the move is searched
738 nodes = pos.nodes_searched();
740 // If it's time to send nodes info, do it here where we have the
741 // correct accumulated node counts searched by each thread.
742 if (SendSearchedNodes)
744 SendSearchedNodes = false;
745 cout << "info nodes " << nodes
746 << " nps " << nps(pos)
747 << " time " << current_search_time() << endl;
750 // Pick the next root move, and print the move and the move number to
751 // the standard output.
752 move = ss->currentMove = rm->pv[0];
753 movesSearched[moveCount++] = move;
754 isPvMove = (moveCount <= MultiPV);
756 if (current_search_time() >= 1000)
757 cout << "info currmove " << move
758 << " currmovenumber " << moveCount << endl;
760 moveIsCheck = pos.move_is_check(move);
761 captureOrPromotion = pos.move_is_capture_or_promotion(move);
763 // Step 11. Decide the new search depth
764 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
765 newDepth = depth + ext;
767 // Step 12. Futility pruning (omitted at root)
769 // Step extra. Fail high loop
770 // If move fails high, we research with bigger window until we are not failing
772 value = -VALUE_INFINITE;
776 // Step 13. Make the move
777 pos.do_move(move, st, ci, moveIsCheck);
779 // Step extra. pv search
780 // We do pv search for PV moves and when failing high
781 if (isPvMove || value > alpha)
783 // Aspiration window is disabled in multi-pv case
785 alpha = -VALUE_INFINITE;
787 // Full depth PV search, done on first move or after a fail high
788 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
792 // Step 14. Reduced search
793 // if the move fails high will be re-searched at full depth
794 bool doFullDepthSearch = true;
796 if ( depth >= 3 * ONE_PLY
798 && !captureOrPromotion
799 && !move_is_castle(move))
801 ss->reduction = reduction<PV>(depth, moveCount - MultiPV + 1);
804 assert(newDepth-ss->reduction >= ONE_PLY);
806 // Reduced depth non-pv search using alpha as upperbound
807 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
808 doFullDepthSearch = (value > alpha);
810 ss->reduction = DEPTH_ZERO; // Restore original reduction
813 // Step 15. Full depth search
814 if (doFullDepthSearch)
816 // Full depth non-pv search using alpha as upperbound
817 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
819 // If we are above alpha then research at same depth but as PV
820 // to get a correct score or eventually a fail high above beta.
822 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
826 // Step 16. Undo move
829 // Can we exit fail high loop ?
830 if (StopRequest || value < beta)
833 // We are failing high and going to do a research. It's important to update
834 // the score before research in case we run out of time while researching.
836 rm->pv_score = value;
837 rm->extract_pv_from_tt(pos);
839 // Update killers and history only for non capture moves that fails high
840 if (!pos.move_is_capture_or_promotion(move))
842 update_history(pos, move, depth, movesSearched, moveCount);
843 update_killers(move, ss->killers);
846 // Inform GUI that PV has changed
847 cout << rm->pv_info_to_uci(pos, alpha, beta) << endl;
849 // Prepare for a research after a fail high, each time with a wider window
850 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
853 } // End of fail high loop
855 // Finished searching the move. If AbortSearch is true, the search
856 // was aborted because the user interrupted the search or because we
857 // ran out of time. In this case, the return value of the search cannot
858 // be trusted, and we break out of the loop without updating the best
863 // Remember searched nodes counts for this move
864 rm->nodes += pos.nodes_searched() - nodes;
866 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
867 assert(value < beta);
869 // Step 17. Check for new best move
870 if (!isPvMove && value <= alpha)
871 rm->pv_score = -VALUE_INFINITE;
874 // PV move or new best move!
878 rm->pv_score = value;
879 rm->extract_pv_from_tt(pos);
881 // We record how often the best move has been changed in each
882 // iteration. This information is used for time managment: When
883 // the best move changes frequently, we allocate some more time.
884 if (!isPvMove && MultiPV == 1)
885 BestMoveChangesByIteration[Iteration]++;
887 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
888 // requires we send all the PV lines properly sorted.
889 rml.sort_multipv(moveCount);
891 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
892 cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
894 // Update alpha. In multi-pv we don't use aspiration window
897 // Raise alpha to setup proper non-pv search upper bound
901 else // Set alpha equal to minimum score among the PV lines
902 alpha = rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
904 } // PV move or new best move
906 assert(alpha >= oldAlpha);
908 AspirationFailLow = (alpha == oldAlpha);
910 if (AspirationFailLow && StopOnPonderhit)
911 StopOnPonderhit = false;
915 // Can we exit fail low loop ?
916 if (StopRequest || !AspirationFailLow)
919 // Prepare for a research after a fail low, each time with a wider window
920 oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
925 // Sort the moves before to return
928 // Write PV lines to transposition table, in case the relevant entries
929 // have been overwritten during the search.
930 for (int i = 0; i < Min(MultiPV, (int)rml.size()); i++)
931 rml[i].insert_pv_in_tt(pos);
937 // search<>() is the main search function for both PV and non-PV nodes and for
938 // normal and SplitPoint nodes. When called just after a split point the search
939 // is simpler because we have already probed the hash table, done a null move
940 // search, and searched the first move before splitting, we don't have to repeat
941 // all this work again. We also don't need to store anything to the hash table
942 // here: This is taken care of after we return from the split point.
944 template <NodeType PvNode, bool SpNode>
945 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
947 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
948 assert(beta > alpha && beta <= VALUE_INFINITE);
949 assert(PvNode || alpha == beta - 1);
950 assert(ply > 0 && ply < PLY_MAX);
951 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
953 Move movesSearched[MOVES_MAX];
957 Move ttMove, move, excludedMove, threatMove;
960 Value bestValue, value, oldAlpha;
961 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
962 bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
963 bool mateThreat = false;
965 int threadID = pos.thread();
966 SplitPoint* sp = NULL;
967 refinedValue = bestValue = value = -VALUE_INFINITE;
969 isCheck = pos.is_check();
975 ttMove = excludedMove = MOVE_NONE;
976 threatMove = sp->threatMove;
977 mateThreat = sp->mateThreat;
978 goto split_point_start;
980 else {} // Hack to fix icc's "statement is unreachable" warning
982 // Step 1. Initialize node and poll. Polling can abort search
983 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
984 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
986 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
992 // Step 2. Check for aborted search and immediate draw
994 || ThreadsMgr.cutoff_at_splitpoint(threadID)
996 || ply >= PLY_MAX - 1)
999 // Step 3. Mate distance pruning
1000 alpha = Max(value_mated_in(ply), alpha);
1001 beta = Min(value_mate_in(ply+1), beta);
1005 // Step 4. Transposition table lookup
1007 // We don't want the score of a partial search to overwrite a previous full search
1008 // TT value, so we use a different position key in case of an excluded move exists.
1009 excludedMove = ss->excludedMove;
1010 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
1012 tte = TT.retrieve(posKey);
1013 ttMove = tte ? tte->move() : MOVE_NONE;
1015 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
1016 // This is to avoid problems in the following areas:
1018 // * Repetition draw detection
1019 // * Fifty move rule detection
1020 // * Searching for a mate
1021 // * Printing of full PV line
1022 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1025 ss->bestMove = ttMove; // Can be MOVE_NONE
1026 return value_from_tt(tte->value(), ply);
1029 // Step 5. Evaluate the position statically and
1030 // update gain statistics of parent move.
1032 ss->eval = ss->evalMargin = VALUE_NONE;
1035 assert(tte->static_value() != VALUE_NONE);
1037 ss->eval = tte->static_value();
1038 ss->evalMargin = tte->static_value_margin();
1039 refinedValue = refine_eval(tte, ss->eval, ply);
1043 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1044 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1047 // Save gain for the parent non-capture move
1048 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1050 // Step 6. Razoring (is omitted in PV nodes)
1052 && depth < RazorDepth
1054 && refinedValue < beta - razor_margin(depth)
1055 && ttMove == MOVE_NONE
1056 && !value_is_mate(beta)
1057 && !pos.has_pawn_on_7th(pos.side_to_move()))
1059 Value rbeta = beta - razor_margin(depth);
1060 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1062 // Logically we should return (v + razor_margin(depth)), but
1063 // surprisingly this did slightly weaker in tests.
1067 // Step 7. Static null move pruning (is omitted in PV nodes)
1068 // We're betting that the opponent doesn't have a move that will reduce
1069 // the score by more than futility_margin(depth) if we do a null move.
1071 && !ss->skipNullMove
1072 && depth < RazorDepth
1074 && refinedValue >= beta + futility_margin(depth, 0)
1075 && !value_is_mate(beta)
1076 && pos.non_pawn_material(pos.side_to_move()))
1077 return refinedValue - futility_margin(depth, 0);
1079 // Step 8. Null move search with verification search (is omitted in PV nodes)
1081 && !ss->skipNullMove
1084 && refinedValue >= beta
1085 && !value_is_mate(beta)
1086 && pos.non_pawn_material(pos.side_to_move()))
1088 ss->currentMove = MOVE_NULL;
1090 // Null move dynamic reduction based on depth
1091 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1093 // Null move dynamic reduction based on value
1094 if (refinedValue - beta > PawnValueMidgame)
1097 pos.do_null_move(st);
1098 (ss+1)->skipNullMove = true;
1099 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1100 (ss+1)->skipNullMove = false;
1101 pos.undo_null_move();
1103 if (nullValue >= beta)
1105 // Do not return unproven mate scores
1106 if (nullValue >= value_mate_in(PLY_MAX))
1109 if (depth < 6 * ONE_PLY)
1112 // Do verification search at high depths
1113 ss->skipNullMove = true;
1114 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1115 ss->skipNullMove = false;
1122 // The null move failed low, which means that we may be faced with
1123 // some kind of threat. If the previous move was reduced, check if
1124 // the move that refuted the null move was somehow connected to the
1125 // move which was reduced. If a connection is found, return a fail
1126 // low score (which will cause the reduced move to fail high in the
1127 // parent node, which will trigger a re-search with full depth).
1128 if (nullValue == value_mated_in(ply + 2))
1131 threatMove = (ss+1)->bestMove;
1132 if ( depth < ThreatDepth
1133 && (ss-1)->reduction
1134 && threatMove != MOVE_NONE
1135 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1140 // Step 9. Internal iterative deepening
1141 if ( depth >= IIDDepth[PvNode]
1142 && ttMove == MOVE_NONE
1143 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1145 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1147 ss->skipNullMove = true;
1148 search<PvNode>(pos, ss, alpha, beta, d, ply);
1149 ss->skipNullMove = false;
1151 ttMove = ss->bestMove;
1152 tte = TT.retrieve(posKey);
1155 // Expensive mate threat detection (only for PV nodes)
1157 mateThreat = pos.has_mate_threat();
1159 split_point_start: // At split points actual search starts from here
1161 // Initialize a MovePicker object for the current position
1162 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1163 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1164 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1166 ss->bestMove = MOVE_NONE;
1167 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1168 futilityBase = ss->eval + ss->evalMargin;
1169 singularExtensionNode = !SpNode
1170 && depth >= SingularExtensionDepth[PvNode]
1173 && !excludedMove // Do not allow recursive singular extension search
1174 && (tte->type() & VALUE_TYPE_LOWER)
1175 && tte->depth() >= depth - 3 * ONE_PLY;
1178 lock_grab(&(sp->lock));
1179 bestValue = sp->bestValue;
1182 // Step 10. Loop through moves
1183 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1184 while ( bestValue < beta
1185 && (move = mp.get_next_move()) != MOVE_NONE
1186 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1188 assert(move_is_ok(move));
1192 moveCount = ++sp->moveCount;
1193 lock_release(&(sp->lock));
1195 else if (move == excludedMove)
1198 movesSearched[moveCount++] = move;
1200 moveIsCheck = pos.move_is_check(move, ci);
1201 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1203 // Step 11. Decide the new search depth
1204 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1206 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1207 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1208 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1209 // lower then ttValue minus a margin then we extend ttMove.
1210 if ( singularExtensionNode
1211 && move == tte->move()
1214 Value ttValue = value_from_tt(tte->value(), ply);
1216 if (abs(ttValue) < VALUE_KNOWN_WIN)
1218 Value b = ttValue - SingularExtensionMargin;
1219 ss->excludedMove = move;
1220 ss->skipNullMove = true;
1221 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1222 ss->skipNullMove = false;
1223 ss->excludedMove = MOVE_NONE;
1224 ss->bestMove = MOVE_NONE;
1230 // Update current move (this must be done after singular extension search)
1231 ss->currentMove = move;
1232 newDepth = depth - ONE_PLY + ext;
1234 // Step 12. Futility pruning (is omitted in PV nodes)
1236 && !captureOrPromotion
1240 && !move_is_castle(move))
1242 // Move count based pruning
1243 if ( moveCount >= futility_move_count(depth)
1244 && !(threatMove && connected_threat(pos, move, threatMove))
1245 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1248 lock_grab(&(sp->lock));
1253 // Value based pruning
1254 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1255 // but fixing this made program slightly weaker.
1256 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1257 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1258 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1260 if (futilityValueScaled < beta)
1264 lock_grab(&(sp->lock));
1265 if (futilityValueScaled > sp->bestValue)
1266 sp->bestValue = bestValue = futilityValueScaled;
1268 else if (futilityValueScaled > bestValue)
1269 bestValue = futilityValueScaled;
1274 // Prune moves with negative SEE at low depths
1275 if ( predictedDepth < 2 * ONE_PLY
1276 && bestValue > value_mated_in(PLY_MAX)
1277 && pos.see_sign(move) < 0)
1280 lock_grab(&(sp->lock));
1286 // Step 13. Make the move
1287 pos.do_move(move, st, ci, moveIsCheck);
1289 // Step extra. pv search (only in PV nodes)
1290 // The first move in list is the expected PV
1291 if (PvNode && moveCount == 1)
1292 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1295 // Step 14. Reduced depth search
1296 // If the move fails high will be re-searched at full depth.
1297 bool doFullDepthSearch = true;
1299 if ( depth >= 3 * ONE_PLY
1300 && !captureOrPromotion
1302 && !move_is_castle(move)
1303 && ss->killers[0] != move
1304 && ss->killers[1] != move)
1306 ss->reduction = reduction<PvNode>(depth, moveCount);
1310 alpha = SpNode ? sp->alpha : alpha;
1311 Depth d = newDepth - ss->reduction;
1312 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1314 doFullDepthSearch = (value > alpha);
1316 ss->reduction = DEPTH_ZERO; // Restore original reduction
1319 // Step 15. Full depth search
1320 if (doFullDepthSearch)
1322 alpha = SpNode ? sp->alpha : alpha;
1323 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1325 // Step extra. pv search (only in PV nodes)
1326 // Search only for possible new PV nodes, if instead value >= beta then
1327 // parent node fails low with value <= alpha and tries another move.
1328 if (PvNode && value > alpha && value < beta)
1329 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1333 // Step 16. Undo move
1334 pos.undo_move(move);
1336 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1338 // Step 17. Check for new best move
1341 lock_grab(&(sp->lock));
1342 bestValue = sp->bestValue;
1346 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1351 sp->bestValue = value;
1355 if (PvNode && value < beta) // We want always alpha < beta
1363 sp->betaCutoff = true;
1365 if (value == value_mate_in(ply + 1))
1366 ss->mateKiller = move;
1368 ss->bestMove = move;
1371 sp->parentSstack->bestMove = move;
1375 // Step 18. Check for split
1377 && depth >= ThreadsMgr.min_split_depth()
1378 && ThreadsMgr.active_threads() > 1
1380 && ThreadsMgr.available_thread_exists(threadID)
1382 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1384 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1385 threatMove, mateThreat, moveCount, &mp, PvNode);
1388 // Step 19. Check for mate and stalemate
1389 // All legal moves have been searched and if there are
1390 // no legal moves, it must be mate or stalemate.
1391 // If one move was excluded return fail low score.
1392 if (!SpNode && !moveCount)
1393 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1395 // Step 20. Update tables
1396 // If the search is not aborted, update the transposition table,
1397 // history counters, and killer moves.
1398 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1400 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1401 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1402 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1404 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1406 // Update killers and history only for non capture moves that fails high
1407 if ( bestValue >= beta
1408 && !pos.move_is_capture_or_promotion(move))
1410 update_history(pos, move, depth, movesSearched, moveCount);
1411 update_killers(move, ss->killers);
1417 // Here we have the lock still grabbed
1418 sp->slaves[threadID] = 0;
1419 sp->nodes += pos.nodes_searched();
1420 lock_release(&(sp->lock));
1423 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1428 // qsearch() is the quiescence search function, which is called by the main
1429 // search function when the remaining depth is zero (or, to be more precise,
1430 // less than ONE_PLY).
1432 template <NodeType PvNode>
1433 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1435 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1436 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1437 assert(PvNode || alpha == beta - 1);
1439 assert(ply > 0 && ply < PLY_MAX);
1440 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1444 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1445 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1448 Value oldAlpha = alpha;
1450 ss->bestMove = ss->currentMove = MOVE_NONE;
1452 // Check for an instant draw or maximum ply reached
1453 if (pos.is_draw() || ply >= PLY_MAX - 1)
1456 // Decide whether or not to include checks, this fixes also the type of
1457 // TT entry depth that we are going to use. Note that in qsearch we use
1458 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1459 isCheck = pos.is_check();
1460 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1462 // Transposition table lookup. At PV nodes, we don't use the TT for
1463 // pruning, but only for move ordering.
1464 tte = TT.retrieve(pos.get_key());
1465 ttMove = (tte ? tte->move() : MOVE_NONE);
1467 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1469 ss->bestMove = ttMove; // Can be MOVE_NONE
1470 return value_from_tt(tte->value(), ply);
1473 // Evaluate the position statically
1476 bestValue = futilityBase = -VALUE_INFINITE;
1477 ss->eval = evalMargin = VALUE_NONE;
1478 enoughMaterial = false;
1484 assert(tte->static_value() != VALUE_NONE);
1486 evalMargin = tte->static_value_margin();
1487 ss->eval = bestValue = tte->static_value();
1490 ss->eval = bestValue = evaluate(pos, evalMargin);
1492 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1494 // Stand pat. Return immediately if static value is at least beta
1495 if (bestValue >= beta)
1498 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1503 if (PvNode && bestValue > alpha)
1506 // Futility pruning parameters, not needed when in check
1507 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1508 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1511 // Initialize a MovePicker object for the current position, and prepare
1512 // to search the moves. Because the depth is <= 0 here, only captures,
1513 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1515 MovePicker mp(pos, ttMove, depth, H);
1518 // Loop through the moves until no moves remain or a beta cutoff occurs
1519 while ( alpha < beta
1520 && (move = mp.get_next_move()) != MOVE_NONE)
1522 assert(move_is_ok(move));
1524 moveIsCheck = pos.move_is_check(move, ci);
1532 && !move_is_promotion(move)
1533 && !pos.move_is_passed_pawn_push(move))
1535 futilityValue = futilityBase
1536 + pos.endgame_value_of_piece_on(move_to(move))
1537 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1539 if (futilityValue < alpha)
1541 if (futilityValue > bestValue)
1542 bestValue = futilityValue;
1547 // Detect non-capture evasions that are candidate to be pruned
1548 evasionPrunable = isCheck
1549 && bestValue > value_mated_in(PLY_MAX)
1550 && !pos.move_is_capture(move)
1551 && !pos.can_castle(pos.side_to_move());
1553 // Don't search moves with negative SEE values
1555 && (!isCheck || evasionPrunable)
1557 && !move_is_promotion(move)
1558 && pos.see_sign(move) < 0)
1561 // Don't search useless checks
1566 && !pos.move_is_capture_or_promotion(move)
1567 && ss->eval + PawnValueMidgame / 4 < beta
1568 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1570 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1571 bestValue = ss->eval + PawnValueMidgame / 4;
1576 // Update current move
1577 ss->currentMove = move;
1579 // Make and search the move
1580 pos.do_move(move, st, ci, moveIsCheck);
1581 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1582 pos.undo_move(move);
1584 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1587 if (value > bestValue)
1593 ss->bestMove = move;
1598 // All legal moves have been searched. A special case: If we're in check
1599 // and no legal moves were found, it is checkmate.
1600 if (isCheck && bestValue == -VALUE_INFINITE)
1601 return value_mated_in(ply);
1603 // Update transposition table
1604 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1605 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1607 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1613 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1614 // bestValue is updated only when returning false because in that case move
1617 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1619 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1620 Square from, to, ksq, victimSq;
1623 Value futilityValue, bv = *bestValue;
1625 from = move_from(move);
1627 them = opposite_color(pos.side_to_move());
1628 ksq = pos.king_square(them);
1629 kingAtt = pos.attacks_from<KING>(ksq);
1630 pc = pos.piece_on(from);
1632 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1633 oldAtt = pos.attacks_from(pc, from, occ);
1634 newAtt = pos.attacks_from(pc, to, occ);
1636 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1637 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1639 if (!(b && (b & (b - 1))))
1642 // Rule 2. Queen contact check is very dangerous
1643 if ( type_of_piece(pc) == QUEEN
1644 && bit_is_set(kingAtt, to))
1647 // Rule 3. Creating new double threats with checks
1648 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1652 victimSq = pop_1st_bit(&b);
1653 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1655 // Note that here we generate illegal "double move"!
1656 if ( futilityValue >= beta
1657 && pos.see_sign(make_move(from, victimSq)) >= 0)
1660 if (futilityValue > bv)
1664 // Update bestValue only if check is not dangerous (because we will prune the move)
1670 // connected_moves() tests whether two moves are 'connected' in the sense
1671 // that the first move somehow made the second move possible (for instance
1672 // if the moving piece is the same in both moves). The first move is assumed
1673 // to be the move that was made to reach the current position, while the
1674 // second move is assumed to be a move from the current position.
1676 bool connected_moves(const Position& pos, Move m1, Move m2) {
1678 Square f1, t1, f2, t2;
1681 assert(m1 && move_is_ok(m1));
1682 assert(m2 && move_is_ok(m2));
1684 // Case 1: The moving piece is the same in both moves
1690 // Case 2: The destination square for m2 was vacated by m1
1696 // Case 3: Moving through the vacated square
1697 if ( piece_is_slider(pos.piece_on(f2))
1698 && bit_is_set(squares_between(f2, t2), f1))
1701 // Case 4: The destination square for m2 is defended by the moving piece in m1
1702 p = pos.piece_on(t1);
1703 if (bit_is_set(pos.attacks_from(p, t1), t2))
1706 // Case 5: Discovered check, checking piece is the piece moved in m1
1707 if ( piece_is_slider(p)
1708 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1709 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1711 // discovered_check_candidates() works also if the Position's side to
1712 // move is the opposite of the checking piece.
1713 Color them = opposite_color(pos.side_to_move());
1714 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1716 if (bit_is_set(dcCandidates, f2))
1723 // value_is_mate() checks if the given value is a mate one eventually
1724 // compensated for the ply.
1726 bool value_is_mate(Value value) {
1728 assert(abs(value) <= VALUE_INFINITE);
1730 return value <= value_mated_in(PLY_MAX)
1731 || value >= value_mate_in(PLY_MAX);
1735 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1736 // "plies to mate from the current ply". Non-mate scores are unchanged.
1737 // The function is called before storing a value to the transposition table.
1739 Value value_to_tt(Value v, int ply) {
1741 if (v >= value_mate_in(PLY_MAX))
1744 if (v <= value_mated_in(PLY_MAX))
1751 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1752 // the transposition table to a mate score corrected for the current ply.
1754 Value value_from_tt(Value v, int ply) {
1756 if (v >= value_mate_in(PLY_MAX))
1759 if (v <= value_mated_in(PLY_MAX))
1766 // extension() decides whether a move should be searched with normal depth,
1767 // or with extended depth. Certain classes of moves (checking moves, in
1768 // particular) are searched with bigger depth than ordinary moves and in
1769 // any case are marked as 'dangerous'. Note that also if a move is not
1770 // extended, as example because the corresponding UCI option is set to zero,
1771 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1772 template <NodeType PvNode>
1773 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1774 bool singleEvasion, bool mateThreat, bool* dangerous) {
1776 assert(m != MOVE_NONE);
1778 Depth result = DEPTH_ZERO;
1779 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1783 if (moveIsCheck && pos.see_sign(m) >= 0)
1784 result += CheckExtension[PvNode];
1787 result += SingleEvasionExtension[PvNode];
1790 result += MateThreatExtension[PvNode];
1793 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1795 Color c = pos.side_to_move();
1796 if (relative_rank(c, move_to(m)) == RANK_7)
1798 result += PawnPushTo7thExtension[PvNode];
1801 if (pos.pawn_is_passed(c, move_to(m)))
1803 result += PassedPawnExtension[PvNode];
1808 if ( captureOrPromotion
1809 && pos.type_of_piece_on(move_to(m)) != PAWN
1810 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1811 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1812 && !move_is_promotion(m)
1815 result += PawnEndgameExtension[PvNode];
1820 && captureOrPromotion
1821 && pos.type_of_piece_on(move_to(m)) != PAWN
1822 && pos.see_sign(m) >= 0)
1824 result += ONE_PLY / 2;
1828 return Min(result, ONE_PLY);
1832 // connected_threat() tests whether it is safe to forward prune a move or if
1833 // is somehow coonected to the threat move returned by null search.
1835 bool connected_threat(const Position& pos, Move m, Move threat) {
1837 assert(move_is_ok(m));
1838 assert(threat && move_is_ok(threat));
1839 assert(!pos.move_is_check(m));
1840 assert(!pos.move_is_capture_or_promotion(m));
1841 assert(!pos.move_is_passed_pawn_push(m));
1843 Square mfrom, mto, tfrom, tto;
1845 mfrom = move_from(m);
1847 tfrom = move_from(threat);
1848 tto = move_to(threat);
1850 // Case 1: Don't prune moves which move the threatened piece
1854 // Case 2: If the threatened piece has value less than or equal to the
1855 // value of the threatening piece, don't prune move which defend it.
1856 if ( pos.move_is_capture(threat)
1857 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1858 || pos.type_of_piece_on(tfrom) == KING)
1859 && pos.move_attacks_square(m, tto))
1862 // Case 3: If the moving piece in the threatened move is a slider, don't
1863 // prune safe moves which block its ray.
1864 if ( piece_is_slider(pos.piece_on(tfrom))
1865 && bit_is_set(squares_between(tfrom, tto), mto)
1866 && pos.see_sign(m) >= 0)
1873 // ok_to_use_TT() returns true if a transposition table score
1874 // can be used at a given point in search.
1876 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1878 Value v = value_from_tt(tte->value(), ply);
1880 return ( tte->depth() >= depth
1881 || v >= Max(value_mate_in(PLY_MAX), beta)
1882 || v < Min(value_mated_in(PLY_MAX), beta))
1884 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1885 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1889 // refine_eval() returns the transposition table score if
1890 // possible otherwise falls back on static position evaluation.
1892 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1896 Value v = value_from_tt(tte->value(), ply);
1898 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1899 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1906 // update_history() registers a good move that produced a beta-cutoff
1907 // in history and marks as failures all the other moves of that ply.
1909 void update_history(const Position& pos, Move move, Depth depth,
1910 Move movesSearched[], int moveCount) {
1913 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
1915 for (int i = 0; i < moveCount - 1; i++)
1917 m = movesSearched[i];
1921 if (!pos.move_is_capture_or_promotion(m))
1922 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
1927 // update_killers() add a good move that produced a beta-cutoff
1928 // among the killer moves of that ply.
1930 void update_killers(Move m, Move killers[]) {
1932 if (m == killers[0])
1935 killers[1] = killers[0];
1940 // update_gains() updates the gains table of a non-capture move given
1941 // the static position evaluation before and after the move.
1943 void update_gains(const Position& pos, Move m, Value before, Value after) {
1946 && before != VALUE_NONE
1947 && after != VALUE_NONE
1948 && pos.captured_piece_type() == PIECE_TYPE_NONE
1949 && !move_is_special(m))
1950 H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1954 // init_ss_array() does a fast reset of the first entries of a SearchStack
1955 // array and of all the excludedMove and skipNullMove entries.
1957 void init_ss_array(SearchStack* ss, int size) {
1959 for (int i = 0; i < size; i++, ss++)
1961 ss->excludedMove = MOVE_NONE;
1962 ss->skipNullMove = false;
1963 ss->reduction = DEPTH_ZERO;
1967 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1972 // value_to_uci() converts a value to a string suitable for use with the UCI
1973 // protocol specifications:
1975 // cp <x> The score from the engine's point of view in centipawns.
1976 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1977 // use negative values for y.
1979 std::string value_to_uci(Value v) {
1981 std::stringstream s;
1983 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1984 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1986 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1992 // current_search_time() returns the number of milliseconds which have passed
1993 // since the beginning of the current search.
1995 int current_search_time() {
1997 return get_system_time() - SearchStartTime;
2001 // nps() computes the current nodes/second count
2003 int nps(const Position& pos) {
2005 int t = current_search_time();
2006 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
2010 // poll() performs two different functions: It polls for user input, and it
2011 // looks at the time consumed so far and decides if it's time to abort the
2014 void poll(const Position& pos) {
2016 static int lastInfoTime;
2017 int t = current_search_time();
2020 if (input_available())
2022 // We are line oriented, don't read single chars
2023 std::string command;
2025 if (!std::getline(std::cin, command))
2028 if (command == "quit")
2030 // Quit the program as soon as possible
2032 QuitRequest = StopRequest = true;
2035 else if (command == "stop")
2037 // Stop calculating as soon as possible, but still send the "bestmove"
2038 // and possibly the "ponder" token when finishing the search.
2042 else if (command == "ponderhit")
2044 // The opponent has played the expected move. GUI sends "ponderhit" if
2045 // we were told to ponder on the same move the opponent has played. We
2046 // should continue searching but switching from pondering to normal search.
2049 if (StopOnPonderhit)
2054 // Print search information
2058 else if (lastInfoTime > t)
2059 // HACK: Must be a new search where we searched less than
2060 // NodesBetweenPolls nodes during the first second of search.
2063 else if (t - lastInfoTime >= 1000)
2070 if (dbg_show_hit_rate)
2071 dbg_print_hit_rate();
2073 // Send info on searched nodes as soon as we return to root
2074 SendSearchedNodes = true;
2077 // Should we stop the search?
2081 bool stillAtFirstMove = FirstRootMove
2082 && !AspirationFailLow
2083 && t > TimeMgr.available_time();
2085 bool noMoreTime = t > TimeMgr.maximum_time()
2086 || stillAtFirstMove;
2088 if ( (UseTimeManagement && noMoreTime)
2089 || (ExactMaxTime && t >= ExactMaxTime)
2090 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2095 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2096 // while the program is pondering. The point is to work around a wrinkle in
2097 // the UCI protocol: When pondering, the engine is not allowed to give a
2098 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2099 // We simply wait here until one of these commands is sent, and return,
2100 // after which the bestmove and pondermove will be printed.
2102 void wait_for_stop_or_ponderhit() {
2104 std::string command;
2108 // Wait for a command from stdin
2109 if (!std::getline(std::cin, command))
2112 if (command == "quit")
2117 else if (command == "ponderhit" || command == "stop")
2123 // init_thread() is the function which is called when a new thread is
2124 // launched. It simply calls the idle_loop() function with the supplied
2125 // threadID. There are two versions of this function; one for POSIX
2126 // threads and one for Windows threads.
2128 #if !defined(_MSC_VER)
2130 void* init_thread(void* threadID) {
2132 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2138 DWORD WINAPI init_thread(LPVOID threadID) {
2140 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2147 /// The ThreadsManager class
2150 // read_uci_options() updates number of active threads and other internal
2151 // parameters according to the UCI options values. It is called before
2152 // to start a new search.
2154 void ThreadsManager::read_uci_options() {
2156 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2157 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2158 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2159 activeThreads = Options["Threads"].value<int>();
2163 // idle_loop() is where the threads are parked when they have no work to do.
2164 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2165 // object for which the current thread is the master.
2167 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2169 assert(threadID >= 0 && threadID < MAX_THREADS);
2172 bool allFinished = false;
2176 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2177 // master should exit as last one.
2178 if (allThreadsShouldExit)
2181 threads[threadID].state = THREAD_TERMINATED;
2185 // If we are not thinking, wait for a condition to be signaled
2186 // instead of wasting CPU time polling for work.
2187 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2188 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2190 assert(!sp || useSleepingThreads);
2191 assert(threadID != 0 || useSleepingThreads);
2193 if (threads[threadID].state == THREAD_INITIALIZING)
2194 threads[threadID].state = THREAD_AVAILABLE;
2196 // Grab the lock to avoid races with wake_sleeping_thread()
2197 lock_grab(&sleepLock[threadID]);
2199 // If we are master and all slaves have finished do not go to sleep
2200 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2201 allFinished = (i == activeThreads);
2203 if (allFinished || allThreadsShouldExit)
2205 lock_release(&sleepLock[threadID]);
2209 // Do sleep here after retesting sleep conditions
2210 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2211 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2213 lock_release(&sleepLock[threadID]);
2216 // If this thread has been assigned work, launch a search
2217 if (threads[threadID].state == THREAD_WORKISWAITING)
2219 assert(!allThreadsShouldExit);
2221 threads[threadID].state = THREAD_SEARCHING;
2223 // Here we call search() with SplitPoint template parameter set to true
2224 SplitPoint* tsp = threads[threadID].splitPoint;
2225 Position pos(*tsp->pos, threadID);
2226 SearchStack* ss = tsp->sstack[threadID] + 1;
2230 search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2232 search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2234 assert(threads[threadID].state == THREAD_SEARCHING);
2236 threads[threadID].state = THREAD_AVAILABLE;
2238 // Wake up master thread so to allow it to return from the idle loop in
2239 // case we are the last slave of the split point.
2240 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2241 wake_sleeping_thread(tsp->master);
2244 // If this thread is the master of a split point and all slaves have
2245 // finished their work at this split point, return from the idle loop.
2246 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2247 allFinished = (i == activeThreads);
2251 // Because sp->slaves[] is reset under lock protection,
2252 // be sure sp->lock has been released before to return.
2253 lock_grab(&(sp->lock));
2254 lock_release(&(sp->lock));
2256 // In helpful master concept a master can help only a sub-tree, and
2257 // because here is all finished is not possible master is booked.
2258 assert(threads[threadID].state == THREAD_AVAILABLE);
2260 threads[threadID].state = THREAD_SEARCHING;
2267 // init_threads() is called during startup. It launches all helper threads,
2268 // and initializes the split point stack and the global locks and condition
2271 void ThreadsManager::init_threads() {
2273 int i, arg[MAX_THREADS];
2276 // Initialize global locks
2279 for (i = 0; i < MAX_THREADS; i++)
2281 lock_init(&sleepLock[i]);
2282 cond_init(&sleepCond[i]);
2285 // Initialize splitPoints[] locks
2286 for (i = 0; i < MAX_THREADS; i++)
2287 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2288 lock_init(&(threads[i].splitPoints[j].lock));
2290 // Will be set just before program exits to properly end the threads
2291 allThreadsShouldExit = false;
2293 // Threads will be put all threads to sleep as soon as created
2296 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2297 threads[0].state = THREAD_SEARCHING;
2298 for (i = 1; i < MAX_THREADS; i++)
2299 threads[i].state = THREAD_INITIALIZING;
2301 // Launch the helper threads
2302 for (i = 1; i < MAX_THREADS; i++)
2306 #if !defined(_MSC_VER)
2307 pthread_t pthread[1];
2308 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2309 pthread_detach(pthread[0]);
2311 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2315 cout << "Failed to create thread number " << i << endl;
2319 // Wait until the thread has finished launching and is gone to sleep
2320 while (threads[i].state == THREAD_INITIALIZING) {}
2325 // exit_threads() is called when the program exits. It makes all the
2326 // helper threads exit cleanly.
2328 void ThreadsManager::exit_threads() {
2330 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2332 // Wake up all the threads and waits for termination
2333 for (int i = 1; i < MAX_THREADS; i++)
2335 wake_sleeping_thread(i);
2336 while (threads[i].state != THREAD_TERMINATED) {}
2339 // Now we can safely destroy the locks
2340 for (int i = 0; i < MAX_THREADS; i++)
2341 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2342 lock_destroy(&(threads[i].splitPoints[j].lock));
2344 lock_destroy(&mpLock);
2346 // Now we can safely destroy the wait conditions
2347 for (int i = 0; i < MAX_THREADS; i++)
2349 lock_destroy(&sleepLock[i]);
2350 cond_destroy(&sleepCond[i]);
2355 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2356 // the thread's currently active split point, or in some ancestor of
2357 // the current split point.
2359 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2361 assert(threadID >= 0 && threadID < activeThreads);
2363 SplitPoint* sp = threads[threadID].splitPoint;
2365 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2370 // thread_is_available() checks whether the thread with threadID "slave" is
2371 // available to help the thread with threadID "master" at a split point. An
2372 // obvious requirement is that "slave" must be idle. With more than two
2373 // threads, this is not by itself sufficient: If "slave" is the master of
2374 // some active split point, it is only available as a slave to the other
2375 // threads which are busy searching the split point at the top of "slave"'s
2376 // split point stack (the "helpful master concept" in YBWC terminology).
2378 bool ThreadsManager::thread_is_available(int slave, int master) const {
2380 assert(slave >= 0 && slave < activeThreads);
2381 assert(master >= 0 && master < activeThreads);
2382 assert(activeThreads > 1);
2384 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2387 // Make a local copy to be sure doesn't change under our feet
2388 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2390 // No active split points means that the thread is available as
2391 // a slave for any other thread.
2392 if (localActiveSplitPoints == 0 || activeThreads == 2)
2395 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2396 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2397 // could have been set to 0 by another thread leading to an out of bound access.
2398 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2405 // available_thread_exists() tries to find an idle thread which is available as
2406 // a slave for the thread with threadID "master".
2408 bool ThreadsManager::available_thread_exists(int master) const {
2410 assert(master >= 0 && master < activeThreads);
2411 assert(activeThreads > 1);
2413 for (int i = 0; i < activeThreads; i++)
2414 if (thread_is_available(i, master))
2421 // split() does the actual work of distributing the work at a node between
2422 // several available threads. If it does not succeed in splitting the
2423 // node (because no idle threads are available, or because we have no unused
2424 // split point objects), the function immediately returns. If splitting is
2425 // possible, a SplitPoint object is initialized with all the data that must be
2426 // copied to the helper threads and we tell our helper threads that they have
2427 // been assigned work. This will cause them to instantly leave their idle loops and
2428 // call search().When all threads have returned from search() then split() returns.
2430 template <bool Fake>
2431 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2432 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2433 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2434 assert(pos.is_ok());
2435 assert(ply > 0 && ply < PLY_MAX);
2436 assert(*bestValue >= -VALUE_INFINITE);
2437 assert(*bestValue <= *alpha);
2438 assert(*alpha < beta);
2439 assert(beta <= VALUE_INFINITE);
2440 assert(depth > DEPTH_ZERO);
2441 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2442 assert(activeThreads > 1);
2444 int i, master = pos.thread();
2445 Thread& masterThread = threads[master];
2449 // If no other thread is available to help us, or if we have too many
2450 // active split points, don't split.
2451 if ( !available_thread_exists(master)
2452 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2454 lock_release(&mpLock);
2458 // Pick the next available split point object from the split point stack
2459 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2461 // Initialize the split point object
2462 splitPoint.parent = masterThread.splitPoint;
2463 splitPoint.master = master;
2464 splitPoint.betaCutoff = false;
2465 splitPoint.ply = ply;
2466 splitPoint.depth = depth;
2467 splitPoint.threatMove = threatMove;
2468 splitPoint.mateThreat = mateThreat;
2469 splitPoint.alpha = *alpha;
2470 splitPoint.beta = beta;
2471 splitPoint.pvNode = pvNode;
2472 splitPoint.bestValue = *bestValue;
2474 splitPoint.moveCount = moveCount;
2475 splitPoint.pos = &pos;
2476 splitPoint.nodes = 0;
2477 splitPoint.parentSstack = ss;
2478 for (i = 0; i < activeThreads; i++)
2479 splitPoint.slaves[i] = 0;
2481 masterThread.splitPoint = &splitPoint;
2483 // If we are here it means we are not available
2484 assert(masterThread.state != THREAD_AVAILABLE);
2486 int workersCnt = 1; // At least the master is included
2488 // Allocate available threads setting state to THREAD_BOOKED
2489 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2490 if (thread_is_available(i, master))
2492 threads[i].state = THREAD_BOOKED;
2493 threads[i].splitPoint = &splitPoint;
2494 splitPoint.slaves[i] = 1;
2498 assert(Fake || workersCnt > 1);
2500 // We can release the lock because slave threads are already booked and master is not available
2501 lock_release(&mpLock);
2503 // Tell the threads that they have work to do. This will make them leave
2504 // their idle loop. But before copy search stack tail for each thread.
2505 for (i = 0; i < activeThreads; i++)
2506 if (i == master || splitPoint.slaves[i])
2508 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2510 assert(i == master || threads[i].state == THREAD_BOOKED);
2512 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2514 if (useSleepingThreads && i != master)
2515 wake_sleeping_thread(i);
2518 // Everything is set up. The master thread enters the idle loop, from
2519 // which it will instantly launch a search, because its state is
2520 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2521 // idle loop, which means that the main thread will return from the idle
2522 // loop when all threads have finished their work at this split point.
2523 idle_loop(master, &splitPoint);
2525 // We have returned from the idle loop, which means that all threads are
2526 // finished. Update alpha and bestValue, and return.
2529 *alpha = splitPoint.alpha;
2530 *bestValue = splitPoint.bestValue;
2531 masterThread.activeSplitPoints--;
2532 masterThread.splitPoint = splitPoint.parent;
2533 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2535 lock_release(&mpLock);
2539 // wake_sleeping_thread() wakes up the thread with the given threadID
2540 // when it is time to start a new search.
2542 void ThreadsManager::wake_sleeping_thread(int threadID) {
2544 lock_grab(&sleepLock[threadID]);
2545 cond_signal(&sleepCond[threadID]);
2546 lock_release(&sleepLock[threadID]);
2550 /// RootMove and RootMoveList method's definitions
2552 RootMove::RootMove() {
2555 pv_score = non_pv_score = -VALUE_INFINITE;
2559 RootMove& RootMove::operator=(const RootMove& rm) {
2561 const Move* src = rm.pv;
2564 // Avoid a costly full rm.pv[] copy
2565 do *dst++ = *src; while (*src++ != MOVE_NONE);
2568 pv_score = rm.pv_score;
2569 non_pv_score = rm.non_pv_score;
2573 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2574 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2575 // allow to always have a ponder move even when we fail high at root and also a
2576 // long PV to print that is important for position analysis.
2578 void RootMove::extract_pv_from_tt(Position& pos) {
2580 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2584 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2586 pos.do_move(pv[0], *st++);
2588 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2589 && tte->move() != MOVE_NONE
2590 && move_is_legal(pos, tte->move())
2592 && (!pos.is_draw() || ply < 2))
2594 pv[ply] = tte->move();
2595 pos.do_move(pv[ply++], *st++);
2597 pv[ply] = MOVE_NONE;
2599 do pos.undo_move(pv[--ply]); while (ply);
2602 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2603 // the PV back into the TT. This makes sure the old PV moves are searched
2604 // first, even if the old TT entries have been overwritten.
2606 void RootMove::insert_pv_in_tt(Position& pos) {
2608 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2611 Value v, m = VALUE_NONE;
2614 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2618 tte = TT.retrieve(k);
2620 // Don't overwrite exsisting correct entries
2621 if (!tte || tte->move() != pv[ply])
2623 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2624 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2626 pos.do_move(pv[ply], *st++);
2628 } while (pv[++ply] != MOVE_NONE);
2630 do pos.undo_move(pv[--ply]); while (ply);
2633 // pv_info_to_uci() returns a string with information on the current PV line
2634 // formatted according to UCI specification and eventually writes the info
2635 // to a log file. It is called at each iteration or after a new pv is found.
2637 std::string RootMove::pv_info_to_uci(Position& pos, Value alpha, Value beta, int pvLine) {
2639 std::stringstream s, l;
2642 while (*m != MOVE_NONE)
2645 s << "info depth " << Iteration // FIXME
2646 << " seldepth " << int(m - pv)
2647 << " multipv " << pvLine + 1
2648 << " score " << value_to_uci(pv_score)
2649 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2650 << " time " << current_search_time()
2651 << " nodes " << pos.nodes_searched()
2652 << " nps " << nps(pos)
2653 << " pv " << l.str();
2655 if (UseLogFile && pvLine == 0)
2657 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2658 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2660 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2666 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2668 SearchStack ss[PLY_MAX_PLUS_2];
2669 MoveStack mlist[MOVES_MAX];
2673 // Initialize search stack
2674 init_ss_array(ss, PLY_MAX_PLUS_2);
2675 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2677 // Generate all legal moves
2678 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2680 // Add each move to the RootMoveList's vector
2681 for (MoveStack* cur = mlist; cur != last; cur++)
2683 // If we have a searchMoves[] list then verify cur->move
2684 // is in the list before to add it.
2685 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2687 if (searchMoves[0] && *sm != cur->move)
2690 // Find a quick score for the move and add to the list
2691 pos.do_move(cur->move, st);
2694 rm.pv[0] = ss[0].currentMove = cur->move;
2695 rm.pv[1] = MOVE_NONE;
2696 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2699 pos.undo_move(cur->move);
2704 // Score root moves using the standard way used in main search, the moves
2705 // are scored according to the order in which are returned by MovePicker.
2706 // This is the second order score that is used to compare the moves when
2707 // the first order pv scores of both moves are equal.
2709 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2712 Value score = VALUE_ZERO;
2713 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2715 while ((move = mp.get_next_move()) != MOVE_NONE)
2716 for (Base::iterator it = begin(); it != end(); ++it)
2717 if (it->pv[0] == move)
2719 it->non_pv_score = score--;