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
251 // Pointer to root move list
257 // Scores and number of times the best move changed for each iteration
258 Value ValueByIteration[PLY_MAX_PLUS_2];
259 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
261 // Search window management
267 // Time managment variables
268 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
269 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
270 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
275 std::ofstream LogFile;
277 // Multi-threads manager object
278 ThreadsManager ThreadsMgr;
280 // Node counters, used only by thread[0] but try to keep in different cache
281 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
282 bool SendSearchedNodes;
284 int NodesBetweenPolls = 30000;
291 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
293 template <NodeType PvNode, bool SpNode, bool Root>
294 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
296 template <NodeType PvNode>
297 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
299 template <NodeType PvNode>
300 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
302 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
303 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
306 template <NodeType PvNode>
307 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
309 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
310 bool connected_moves(const Position& pos, Move m1, Move m2);
311 bool value_is_mate(Value value);
312 Value value_to_tt(Value v, int ply);
313 Value value_from_tt(Value v, int ply);
314 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
315 bool connected_threat(const Position& pos, Move m, Move threat);
316 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
317 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
318 void update_killers(Move m, Move killers[]);
319 void update_gains(const Position& pos, Move move, Value before, Value after);
321 int current_search_time();
322 std::string value_to_uci(Value v);
323 int nps(const Position& pos);
324 void poll(const Position& pos);
325 void wait_for_stop_or_ponderhit();
326 void init_ss_array(SearchStack* ss, int size);
328 #if !defined(_MSC_VER)
329 void* init_thread(void* threadID);
331 DWORD WINAPI init_thread(LPVOID threadID);
335 // A dispatcher to choose among different move sources according to the type of node
336 template<bool SpNode, bool Root> struct MovePickerExt;
338 // In Root nodes use RootMoveList Rml as source
339 template<> struct MovePickerExt<false, true> {
341 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack*, Value)
342 : rm(Rml->begin()), firstCall(true) {}
344 Move get_next_move() {
351 return rm != Rml->end() ? rm->pv[0] : MOVE_NONE;
353 int number_of_evasions() const { return (int)Rml->size(); }
355 RootMoveList::iterator rm;
359 // In SpNodes use split point's shared MovePicker as move source
360 template<> struct MovePickerExt<true, false> {
362 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack* ss, Value)
365 Move get_next_move() { return mp->get_next_move(); }
366 int number_of_evasions() const { return mp->number_of_evasions(); }
368 RootMoveList::iterator rm; // Dummy, never used
372 // Normal case, create and use a MovePicker object as source
373 template<> struct MovePickerExt<false, false> : public MovePicker {
375 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
376 SearchStack* ss, Value beta) : MovePicker(p, ttm, d, h, ss, beta) {}
378 RootMoveList::iterator rm; // Dummy, never used
388 /// init_threads(), exit_threads() and nodes_searched() are helpers to
389 /// give accessibility to some TM methods from outside of current file.
391 void init_threads() { ThreadsMgr.init_threads(); }
392 void exit_threads() { ThreadsMgr.exit_threads(); }
395 /// init_search() is called during startup. It initializes various lookup tables
399 int d; // depth (ONE_PLY == 2)
400 int hd; // half depth (ONE_PLY == 1)
403 // Init reductions array
404 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
406 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
407 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
408 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
409 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
412 // Init futility margins array
413 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
414 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
416 // Init futility move count array
417 for (d = 0; d < 32; d++)
418 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
422 /// perft() is our utility to verify move generation is bug free. All the legal
423 /// moves up to given depth are generated and counted and the sum returned.
425 int64_t perft(Position& pos, Depth depth)
427 MoveStack mlist[MOVES_MAX];
432 // Generate all legal moves
433 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
435 // If we are at the last ply we don't need to do and undo
436 // the moves, just to count them.
437 if (depth <= ONE_PLY)
438 return int(last - mlist);
440 // Loop through all legal moves
442 for (MoveStack* cur = mlist; cur != last; cur++)
445 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
446 sum += perft(pos, depth - ONE_PLY);
453 /// think() is the external interface to Stockfish's search, and is called when
454 /// the program receives the UCI 'go' command. It initializes various
455 /// search-related global variables, and calls id_loop(). It returns false
456 /// when a quit command is received during the search.
458 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
459 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
461 // Initialize global search variables
462 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
464 SearchStartTime = get_system_time();
465 ExactMaxTime = maxTime;
468 InfiniteSearch = infinite;
470 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
472 // Look for a book move, only during games, not tests
473 if (UseTimeManagement && Options["OwnBook"].value<bool>())
475 if (Options["Book File"].value<std::string>() != OpeningBook.name())
476 OpeningBook.open(Options["Book File"].value<std::string>());
478 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
479 if (bookMove != MOVE_NONE)
482 wait_for_stop_or_ponderhit();
484 cout << "bestmove " << bookMove << endl;
489 // Read UCI option values
490 TT.set_size(Options["Hash"].value<int>());
491 if (Options["Clear Hash"].value<bool>())
493 Options["Clear Hash"].set_value("false");
497 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
498 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
499 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
500 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
501 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
502 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
503 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
504 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
505 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
506 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
507 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
508 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
509 MultiPV = Options["MultiPV"].value<int>();
510 UseLogFile = Options["Use Search Log"].value<bool>();
512 read_evaluation_uci_options(pos.side_to_move());
514 // Set the number of active threads
515 ThreadsMgr.read_uci_options();
516 init_eval(ThreadsMgr.active_threads());
518 // Wake up needed threads
519 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
520 ThreadsMgr.wake_sleeping_thread(i);
523 int myTime = time[pos.side_to_move()];
524 int myIncrement = increment[pos.side_to_move()];
525 if (UseTimeManagement)
526 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
528 // Set best NodesBetweenPolls interval to avoid lagging under
529 // heavy time pressure.
531 NodesBetweenPolls = Min(MaxNodes, 30000);
532 else if (myTime && myTime < 1000)
533 NodesBetweenPolls = 1000;
534 else if (myTime && myTime < 5000)
535 NodesBetweenPolls = 5000;
537 NodesBetweenPolls = 30000;
539 // Write search information to log file
542 std::string name = Options["Search Log Filename"].value<std::string>();
543 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
545 LogFile << "Searching: " << pos.to_fen()
546 << "\ninfinite: " << infinite
547 << " ponder: " << ponder
548 << " time: " << myTime
549 << " increment: " << myIncrement
550 << " moves to go: " << movesToGo << endl;
553 // We're ready to start thinking. Call the iterative deepening loop function
554 Move ponderMove = MOVE_NONE;
555 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
557 // Print final search statistics
558 cout << "info nodes " << pos.nodes_searched()
559 << " nps " << nps(pos)
560 << " time " << current_search_time() << endl;
564 LogFile << "\nNodes: " << pos.nodes_searched()
565 << "\nNodes/second: " << nps(pos)
566 << "\nBest move: " << move_to_san(pos, bestMove);
569 pos.do_move(bestMove, st);
570 LogFile << "\nPonder move: "
571 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
574 // Return from think() with unchanged position
575 pos.undo_move(bestMove);
580 // This makes all the threads to go to sleep
581 ThreadsMgr.set_active_threads(1);
583 // If we are pondering or in infinite search, we shouldn't print the
584 // best move before we are told to do so.
585 if (!StopRequest && (Pondering || InfiniteSearch))
586 wait_for_stop_or_ponderhit();
588 // Could be both MOVE_NONE when searching on a stalemate position
589 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
597 // id_loop() is the main iterative deepening loop. It calls search()
598 // repeatedly with increasing depth until the allocated thinking time has
599 // been consumed, the user stops the search, or the maximum search depth is
602 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
604 SearchStack ss[PLY_MAX_PLUS_2];
606 Move EasyMove = MOVE_NONE;
607 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
608 int researchCountFL, researchCountFH;
610 // Moves to search are verified, scored and sorted
611 RootMoveList rml(pos, searchMoves);
614 // Handle special case of searching on a mate/stale position
617 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
619 cout << "info depth " << 1
620 << " score " << value_to_uci(s) << endl;
628 init_ss_array(ss, PLY_MAX_PLUS_2);
629 ValueByIteration[1] = rml[0].pv_score;
632 // Send initial RootMoveList scoring (iteration 1)
633 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
634 << "info depth " << Iteration
635 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
637 // Is one move significantly better than others after initial scoring ?
639 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
640 EasyMove = rml[0].pv[0];
642 // Iterative deepening loop
643 while (Iteration < PLY_MAX)
645 // Initialize iteration
647 BestMoveChangesByIteration[Iteration] = 0;
649 cout << "info depth " << Iteration << endl;
651 // Calculate dynamic aspiration window based on previous iterations
652 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
654 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
655 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
657 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
658 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
660 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
661 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
664 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
666 researchCountFL = researchCountFH = 0;
668 // We start with small aspiration window and in case of fail high/low, we
669 // research with bigger window until we are not failing high/low anymore.
672 // Sort the moves before to (re)search
673 rml.set_non_pv_scores(pos, rml[0].pv[0], ss);
676 // Search to the current depth, rml is updated and sorted
677 value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
679 // Sort the moves before to return
682 // Write PV lines to transposition table, in case the relevant entries
683 // have been overwritten during the search.
684 for (int i = 0; i < Min(MultiPV, (int)rml.size()); i++)
685 rml[i].insert_pv_in_tt(pos);
690 assert(value >= alpha);
694 // Prepare for a research after a fail high, each time with a wider window
695 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
698 else if (value <= alpha)
700 AspirationFailLow = true;
701 StopOnPonderhit = false;
703 // Prepare for a research after a fail low, each time with a wider window
704 alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
712 break; // Value cannot be trusted. Break out immediately!
714 //Save info about search result
715 ValueByIteration[Iteration] = value;
717 // Drop the easy move if differs from the new best move
718 if (rml[0].pv[0] != EasyMove)
719 EasyMove = MOVE_NONE;
721 if (UseTimeManagement)
724 bool stopSearch = false;
726 // Stop search early if there is only a single legal move,
727 // we search up to Iteration 6 anyway to get a proper score.
728 if (Iteration >= 6 && rml.size() == 1)
731 // Stop search early when the last two iterations returned a mate score
733 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
734 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
737 // Stop search early if one move seems to be much better than the others
739 && EasyMove == rml[0].pv[0]
740 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
741 && current_search_time() > TimeMgr.available_time() / 16)
742 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
743 && current_search_time() > TimeMgr.available_time() / 32)))
746 // Add some extra time if the best move has changed during the last two iterations
747 if (Iteration > 5 && Iteration <= 50)
748 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
749 BestMoveChangesByIteration[Iteration-1]);
751 // Stop search if most of MaxSearchTime is consumed at the end of the
752 // iteration. We probably don't have enough time to search the first
753 // move at the next iteration anyway.
754 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
760 StopOnPonderhit = true;
766 if (MaxDepth && Iteration >= MaxDepth)
770 *ponderMove = rml[0].pv[1];
775 // search<>() is the main search function for both PV and non-PV nodes and for
776 // normal and SplitPoint nodes. When called just after a split point the search
777 // is simpler because we have already probed the hash table, done a null move
778 // search, and searched the first move before splitting, we don't have to repeat
779 // all this work again. We also don't need to store anything to the hash table
780 // here: This is taken care of after we return from the split point.
782 template <NodeType PvNode, bool SpNode, bool Root>
783 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
785 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
786 assert(beta > alpha && beta <= VALUE_INFINITE);
787 assert(PvNode || alpha == beta - 1);
788 assert((Root || ply > 0) && ply < PLY_MAX);
789 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
791 Move movesSearched[MOVES_MAX];
796 Move ttMove, move, excludedMove, threatMove;
799 Value bestValue, value, oldAlpha;
800 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
801 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
802 bool mateThreat = false;
804 int threadID = pos.thread();
805 SplitPoint* sp = NULL;
807 refinedValue = bestValue = value = -VALUE_INFINITE;
809 isCheck = pos.is_check();
815 ttMove = excludedMove = MOVE_NONE;
816 threatMove = sp->threatMove;
817 mateThreat = sp->mateThreat;
818 goto split_point_start;
820 else {} // Hack to fix icc's "statement is unreachable" warning
822 // Step 1. Initialize node and poll. Polling can abort search
823 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
824 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
828 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
834 // Step 2. Check for aborted search and immediate draw
836 || ThreadsMgr.cutoff_at_splitpoint(threadID)
838 || ply >= PLY_MAX - 1)
841 // Step 3. Mate distance pruning
842 alpha = Max(value_mated_in(ply), alpha);
843 beta = Min(value_mate_in(ply+1), beta);
848 // Step 4. Transposition table lookup
850 // We don't want the score of a partial search to overwrite a previous full search
851 // TT value, so we use a different position key in case of an excluded move exists.
852 excludedMove = ss->excludedMove;
853 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
855 tte = TT.retrieve(posKey);
856 ttMove = tte ? tte->move() : MOVE_NONE;
858 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
859 // This is to avoid problems in the following areas:
861 // * Repetition draw detection
862 // * Fifty move rule detection
863 // * Searching for a mate
864 // * Printing of full PV line
865 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
868 ss->bestMove = ttMove; // Can be MOVE_NONE
869 return value_from_tt(tte->value(), ply);
872 // Step 5. Evaluate the position statically and
873 // update gain statistics of parent move.
875 ss->eval = ss->evalMargin = VALUE_NONE;
878 assert(tte->static_value() != VALUE_NONE);
880 ss->eval = tte->static_value();
881 ss->evalMargin = tte->static_value_margin();
882 refinedValue = refine_eval(tte, ss->eval, ply);
886 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
887 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
890 // Save gain for the parent non-capture move
892 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
894 // Step 6. Razoring (is omitted in PV nodes)
896 && depth < RazorDepth
898 && refinedValue < beta - razor_margin(depth)
899 && ttMove == MOVE_NONE
900 && !value_is_mate(beta)
901 && !pos.has_pawn_on_7th(pos.side_to_move()))
903 Value rbeta = beta - razor_margin(depth);
904 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
906 // Logically we should return (v + razor_margin(depth)), but
907 // surprisingly this did slightly weaker in tests.
911 // Step 7. Static null move pruning (is omitted in PV nodes)
912 // We're betting that the opponent doesn't have a move that will reduce
913 // the score by more than futility_margin(depth) if we do a null move.
916 && depth < RazorDepth
918 && refinedValue >= beta + futility_margin(depth, 0)
919 && !value_is_mate(beta)
920 && pos.non_pawn_material(pos.side_to_move()))
921 return refinedValue - futility_margin(depth, 0);
923 // Step 8. Null move search with verification search (is omitted in PV nodes)
928 && refinedValue >= beta
929 && !value_is_mate(beta)
930 && pos.non_pawn_material(pos.side_to_move()))
932 ss->currentMove = MOVE_NULL;
934 // Null move dynamic reduction based on depth
935 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
937 // Null move dynamic reduction based on value
938 if (refinedValue - beta > PawnValueMidgame)
941 pos.do_null_move(st);
942 (ss+1)->skipNullMove = true;
943 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
944 (ss+1)->skipNullMove = false;
945 pos.undo_null_move();
947 if (nullValue >= beta)
949 // Do not return unproven mate scores
950 if (nullValue >= value_mate_in(PLY_MAX))
953 if (depth < 6 * ONE_PLY)
956 // Do verification search at high depths
957 ss->skipNullMove = true;
958 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
959 ss->skipNullMove = false;
966 // The null move failed low, which means that we may be faced with
967 // some kind of threat. If the previous move was reduced, check if
968 // the move that refuted the null move was somehow connected to the
969 // move which was reduced. If a connection is found, return a fail
970 // low score (which will cause the reduced move to fail high in the
971 // parent node, which will trigger a re-search with full depth).
972 if (nullValue == value_mated_in(ply + 2))
975 threatMove = (ss+1)->bestMove;
976 if ( depth < ThreatDepth
978 && threatMove != MOVE_NONE
979 && connected_moves(pos, (ss-1)->currentMove, threatMove))
984 // Step 9. Internal iterative deepening
986 && depth >= IIDDepth[PvNode]
987 && ttMove == MOVE_NONE
988 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
990 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
992 ss->skipNullMove = true;
993 search<PvNode>(pos, ss, alpha, beta, d, ply);
994 ss->skipNullMove = false;
996 ttMove = ss->bestMove;
997 tte = TT.retrieve(posKey);
1000 // Expensive mate threat detection (only for PV nodes)
1001 if (PvNode && !Root) // FIXME
1002 mateThreat = pos.has_mate_threat();
1004 split_point_start: // At split points actual search starts from here
1006 // Initialize a MovePicker object for the current position
1007 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1009 ss->bestMove = MOVE_NONE;
1010 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1011 futilityBase = ss->eval + ss->evalMargin;
1012 singularExtensionNode = !Root
1014 && depth >= SingularExtensionDepth[PvNode]
1017 && !excludedMove // Do not allow recursive singular extension search
1018 && (tte->type() & VALUE_TYPE_LOWER)
1019 && tte->depth() >= depth - 3 * ONE_PLY;
1025 lock_grab(&(sp->lock));
1026 bestValue = sp->bestValue;
1029 // Step 10. Loop through moves
1030 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1031 while ( bestValue < beta
1032 && (move = mp.get_next_move()) != MOVE_NONE
1033 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1035 assert(move_is_ok(move));
1039 moveCount = ++sp->moveCount;
1040 lock_release(&(sp->lock));
1042 else if (move == excludedMove)
1045 movesSearched[moveCount++] = move;
1049 // This is used by time management
1050 FirstRootMove = (moveCount == 1);
1052 // Save the current node count before the move is searched
1053 nodes = pos.nodes_searched();
1055 // If it's time to send nodes info, do it here where we have the
1056 // correct accumulated node counts searched by each thread.
1057 if (SendSearchedNodes)
1059 SendSearchedNodes = false;
1060 cout << "info nodes " << nodes
1061 << " nps " << nps(pos)
1062 << " time " << current_search_time() << endl;
1065 if (current_search_time() >= 1000)
1066 cout << "info currmove " << move
1067 << " currmovenumber " << moveCount << endl;
1070 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1071 moveIsCheck = pos.move_is_check(move, ci);
1072 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1074 // Step 11. Decide the new search depth
1075 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1077 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1078 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1079 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1080 // lower then ttValue minus a margin then we extend ttMove.
1081 if ( singularExtensionNode
1082 && move == tte->move()
1085 Value ttValue = value_from_tt(tte->value(), ply);
1087 if (abs(ttValue) < VALUE_KNOWN_WIN)
1089 Value b = ttValue - SingularExtensionMargin;
1090 ss->excludedMove = move;
1091 ss->skipNullMove = true;
1092 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1093 ss->skipNullMove = false;
1094 ss->excludedMove = MOVE_NONE;
1095 ss->bestMove = MOVE_NONE;
1101 // Update current move (this must be done after singular extension search)
1102 ss->currentMove = move;
1103 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1105 // Step 12. Futility pruning (is omitted in PV nodes)
1107 && !captureOrPromotion
1111 && !move_is_castle(move))
1113 // Move count based pruning
1114 if ( moveCount >= futility_move_count(depth)
1115 && !(threatMove && connected_threat(pos, move, threatMove))
1116 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1119 lock_grab(&(sp->lock));
1124 // Value based pruning
1125 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1126 // but fixing this made program slightly weaker.
1127 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1128 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1129 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1131 if (futilityValueScaled < beta)
1135 lock_grab(&(sp->lock));
1136 if (futilityValueScaled > sp->bestValue)
1137 sp->bestValue = bestValue = futilityValueScaled;
1139 else if (futilityValueScaled > bestValue)
1140 bestValue = futilityValueScaled;
1145 // Prune moves with negative SEE at low depths
1146 if ( predictedDepth < 2 * ONE_PLY
1147 && bestValue > value_mated_in(PLY_MAX)
1148 && pos.see_sign(move) < 0)
1151 lock_grab(&(sp->lock));
1157 // Step 13. Make the move
1158 pos.do_move(move, st, ci, moveIsCheck);
1160 // Step extra. pv search (only in PV nodes)
1161 // The first move in list is the expected PV
1164 // Aspiration window is disabled in multi-pv case
1165 if (Root && MultiPV > 1)
1166 alpha = -VALUE_INFINITE;
1168 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1172 // Step 14. Reduced depth search
1173 // If the move fails high will be re-searched at full depth.
1174 bool doFullDepthSearch = true;
1176 if ( depth >= 3 * ONE_PLY
1177 && !captureOrPromotion
1179 && !move_is_castle(move)
1180 && ss->killers[0] != move
1181 && ss->killers[1] != move)
1183 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1184 : reduction<PvNode>(depth, moveCount);
1187 alpha = SpNode ? sp->alpha : alpha;
1188 Depth d = newDepth - ss->reduction;
1189 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1191 doFullDepthSearch = (value > alpha);
1193 ss->reduction = DEPTH_ZERO; // Restore original reduction
1196 // Step 15. Full depth search
1197 if (doFullDepthSearch)
1199 alpha = SpNode ? sp->alpha : alpha;
1200 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1202 // Step extra. pv search (only in PV nodes)
1203 // Search only for possible new PV nodes, if instead value >= beta then
1204 // parent node fails low with value <= alpha and tries another move.
1205 if (PvNode && value > alpha && (Root || value < beta))
1206 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1210 // Step 16. Undo move
1211 pos.undo_move(move);
1213 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1215 // Step 17. Check for new best move
1218 lock_grab(&(sp->lock));
1219 bestValue = sp->bestValue;
1223 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1228 sp->bestValue = value;
1232 if (PvNode && value < beta) // We want always alpha < beta
1240 sp->betaCutoff = true;
1242 if (value == value_mate_in(ply + 1))
1243 ss->mateKiller = move;
1245 ss->bestMove = move;
1248 sp->parentSstack->bestMove = move;
1254 // Finished searching the move. If StopRequest is true, the search
1255 // was aborted because the user interrupted the search or because we
1256 // ran out of time. In this case, the return value of the search cannot
1257 // be trusted, and we break out of the loop without updating the best
1262 // Remember searched nodes counts for this move
1263 mp.rm->nodes += pos.nodes_searched() - nodes;
1265 // Step 17. Check for new best move
1266 if (!isPvMove && value <= alpha)
1267 mp.rm->pv_score = -VALUE_INFINITE;
1270 // PV move or new best move!
1273 ss->bestMove = move;
1274 mp.rm->pv_score = value;
1275 mp.rm->extract_pv_from_tt(pos);
1277 // We record how often the best move has been changed in each
1278 // iteration. This information is used for time managment: When
1279 // the best move changes frequently, we allocate some more time.
1280 if (!isPvMove && MultiPV == 1)
1281 BestMoveChangesByIteration[Iteration]++;
1283 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1284 // requires we send all the PV lines properly sorted.
1285 Rml->sort_multipv(moveCount);
1287 for (int j = 0; j < Min(MultiPV, (int)Rml->size()); j++)
1288 cout << (*Rml)[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
1290 // Update alpha. In multi-pv we don't use aspiration window
1293 // Raise alpha to setup proper non-pv search upper bound
1295 alpha = bestValue = value;
1297 else // Set alpha equal to minimum score among the PV lines
1298 alpha = bestValue = (*Rml)[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1300 } // PV move or new best move
1303 // Step 18. Check for split
1306 && depth >= ThreadsMgr.min_split_depth()
1307 && ThreadsMgr.active_threads() > 1
1309 && ThreadsMgr.available_thread_exists(threadID)
1311 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1313 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1314 threatMove, mateThreat, moveCount, (MovePicker*)&mp, PvNode);
1317 // Step 19. Check for mate and stalemate
1318 // All legal moves have been searched and if there are
1319 // no legal moves, it must be mate or stalemate.
1320 // If one move was excluded return fail low score.
1321 if (!SpNode && !moveCount)
1322 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1324 // Step 20. Update tables
1325 // If the search is not aborted, update the transposition table,
1326 // history counters, and killer moves.
1327 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1329 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1330 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1331 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1333 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1335 // Update killers and history only for non capture moves that fails high
1336 if ( bestValue >= beta
1337 && !pos.move_is_capture_or_promotion(move))
1339 update_history(pos, move, depth, movesSearched, moveCount);
1340 update_killers(move, ss->killers);
1346 // Here we have the lock still grabbed
1347 sp->slaves[threadID] = 0;
1348 sp->nodes += pos.nodes_searched();
1349 lock_release(&(sp->lock));
1352 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1357 // qsearch() is the quiescence search function, which is called by the main
1358 // search function when the remaining depth is zero (or, to be more precise,
1359 // less than ONE_PLY).
1361 template <NodeType PvNode>
1362 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1364 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1365 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1366 assert(PvNode || alpha == beta - 1);
1368 assert(ply > 0 && ply < PLY_MAX);
1369 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1373 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1374 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1377 Value oldAlpha = alpha;
1379 ss->bestMove = ss->currentMove = MOVE_NONE;
1381 // Check for an instant draw or maximum ply reached
1382 if (pos.is_draw() || ply >= PLY_MAX - 1)
1385 // Decide whether or not to include checks, this fixes also the type of
1386 // TT entry depth that we are going to use. Note that in qsearch we use
1387 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1388 isCheck = pos.is_check();
1389 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1391 // Transposition table lookup. At PV nodes, we don't use the TT for
1392 // pruning, but only for move ordering.
1393 tte = TT.retrieve(pos.get_key());
1394 ttMove = (tte ? tte->move() : MOVE_NONE);
1396 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1398 ss->bestMove = ttMove; // Can be MOVE_NONE
1399 return value_from_tt(tte->value(), ply);
1402 // Evaluate the position statically
1405 bestValue = futilityBase = -VALUE_INFINITE;
1406 ss->eval = evalMargin = VALUE_NONE;
1407 enoughMaterial = false;
1413 assert(tte->static_value() != VALUE_NONE);
1415 evalMargin = tte->static_value_margin();
1416 ss->eval = bestValue = tte->static_value();
1419 ss->eval = bestValue = evaluate(pos, evalMargin);
1421 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1423 // Stand pat. Return immediately if static value is at least beta
1424 if (bestValue >= beta)
1427 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1432 if (PvNode && bestValue > alpha)
1435 // Futility pruning parameters, not needed when in check
1436 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1437 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1440 // Initialize a MovePicker object for the current position, and prepare
1441 // to search the moves. Because the depth is <= 0 here, only captures,
1442 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1444 MovePicker mp(pos, ttMove, depth, H);
1447 // Loop through the moves until no moves remain or a beta cutoff occurs
1448 while ( alpha < beta
1449 && (move = mp.get_next_move()) != MOVE_NONE)
1451 assert(move_is_ok(move));
1453 moveIsCheck = pos.move_is_check(move, ci);
1461 && !move_is_promotion(move)
1462 && !pos.move_is_passed_pawn_push(move))
1464 futilityValue = futilityBase
1465 + pos.endgame_value_of_piece_on(move_to(move))
1466 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1468 if (futilityValue < alpha)
1470 if (futilityValue > bestValue)
1471 bestValue = futilityValue;
1476 // Detect non-capture evasions that are candidate to be pruned
1477 evasionPrunable = isCheck
1478 && bestValue > value_mated_in(PLY_MAX)
1479 && !pos.move_is_capture(move)
1480 && !pos.can_castle(pos.side_to_move());
1482 // Don't search moves with negative SEE values
1484 && (!isCheck || evasionPrunable)
1486 && !move_is_promotion(move)
1487 && pos.see_sign(move) < 0)
1490 // Don't search useless checks
1495 && !pos.move_is_capture_or_promotion(move)
1496 && ss->eval + PawnValueMidgame / 4 < beta
1497 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1499 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1500 bestValue = ss->eval + PawnValueMidgame / 4;
1505 // Update current move
1506 ss->currentMove = move;
1508 // Make and search the move
1509 pos.do_move(move, st, ci, moveIsCheck);
1510 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1511 pos.undo_move(move);
1513 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1516 if (value > bestValue)
1522 ss->bestMove = move;
1527 // All legal moves have been searched. A special case: If we're in check
1528 // and no legal moves were found, it is checkmate.
1529 if (isCheck && bestValue == -VALUE_INFINITE)
1530 return value_mated_in(ply);
1532 // Update transposition table
1533 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1534 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1536 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1542 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1543 // bestValue is updated only when returning false because in that case move
1546 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1548 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1549 Square from, to, ksq, victimSq;
1552 Value futilityValue, bv = *bestValue;
1554 from = move_from(move);
1556 them = opposite_color(pos.side_to_move());
1557 ksq = pos.king_square(them);
1558 kingAtt = pos.attacks_from<KING>(ksq);
1559 pc = pos.piece_on(from);
1561 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1562 oldAtt = pos.attacks_from(pc, from, occ);
1563 newAtt = pos.attacks_from(pc, to, occ);
1565 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1566 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1568 if (!(b && (b & (b - 1))))
1571 // Rule 2. Queen contact check is very dangerous
1572 if ( type_of_piece(pc) == QUEEN
1573 && bit_is_set(kingAtt, to))
1576 // Rule 3. Creating new double threats with checks
1577 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1581 victimSq = pop_1st_bit(&b);
1582 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1584 // Note that here we generate illegal "double move"!
1585 if ( futilityValue >= beta
1586 && pos.see_sign(make_move(from, victimSq)) >= 0)
1589 if (futilityValue > bv)
1593 // Update bestValue only if check is not dangerous (because we will prune the move)
1599 // connected_moves() tests whether two moves are 'connected' in the sense
1600 // that the first move somehow made the second move possible (for instance
1601 // if the moving piece is the same in both moves). The first move is assumed
1602 // to be the move that was made to reach the current position, while the
1603 // second move is assumed to be a move from the current position.
1605 bool connected_moves(const Position& pos, Move m1, Move m2) {
1607 Square f1, t1, f2, t2;
1610 assert(m1 && move_is_ok(m1));
1611 assert(m2 && move_is_ok(m2));
1613 // Case 1: The moving piece is the same in both moves
1619 // Case 2: The destination square for m2 was vacated by m1
1625 // Case 3: Moving through the vacated square
1626 if ( piece_is_slider(pos.piece_on(f2))
1627 && bit_is_set(squares_between(f2, t2), f1))
1630 // Case 4: The destination square for m2 is defended by the moving piece in m1
1631 p = pos.piece_on(t1);
1632 if (bit_is_set(pos.attacks_from(p, t1), t2))
1635 // Case 5: Discovered check, checking piece is the piece moved in m1
1636 if ( piece_is_slider(p)
1637 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1638 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1640 // discovered_check_candidates() works also if the Position's side to
1641 // move is the opposite of the checking piece.
1642 Color them = opposite_color(pos.side_to_move());
1643 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1645 if (bit_is_set(dcCandidates, f2))
1652 // value_is_mate() checks if the given value is a mate one eventually
1653 // compensated for the ply.
1655 bool value_is_mate(Value value) {
1657 assert(abs(value) <= VALUE_INFINITE);
1659 return value <= value_mated_in(PLY_MAX)
1660 || value >= value_mate_in(PLY_MAX);
1664 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1665 // "plies to mate from the current ply". Non-mate scores are unchanged.
1666 // The function is called before storing a value to the transposition table.
1668 Value value_to_tt(Value v, int ply) {
1670 if (v >= value_mate_in(PLY_MAX))
1673 if (v <= value_mated_in(PLY_MAX))
1680 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1681 // the transposition table to a mate score corrected for the current ply.
1683 Value value_from_tt(Value v, int ply) {
1685 if (v >= value_mate_in(PLY_MAX))
1688 if (v <= value_mated_in(PLY_MAX))
1695 // extension() decides whether a move should be searched with normal depth,
1696 // or with extended depth. Certain classes of moves (checking moves, in
1697 // particular) are searched with bigger depth than ordinary moves and in
1698 // any case are marked as 'dangerous'. Note that also if a move is not
1699 // extended, as example because the corresponding UCI option is set to zero,
1700 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1701 template <NodeType PvNode>
1702 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1703 bool singleEvasion, bool mateThreat, bool* dangerous) {
1705 assert(m != MOVE_NONE);
1707 Depth result = DEPTH_ZERO;
1708 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1712 if (moveIsCheck && pos.see_sign(m) >= 0)
1713 result += CheckExtension[PvNode];
1716 result += SingleEvasionExtension[PvNode];
1719 result += MateThreatExtension[PvNode];
1722 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1724 Color c = pos.side_to_move();
1725 if (relative_rank(c, move_to(m)) == RANK_7)
1727 result += PawnPushTo7thExtension[PvNode];
1730 if (pos.pawn_is_passed(c, move_to(m)))
1732 result += PassedPawnExtension[PvNode];
1737 if ( captureOrPromotion
1738 && pos.type_of_piece_on(move_to(m)) != PAWN
1739 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1740 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1741 && !move_is_promotion(m)
1744 result += PawnEndgameExtension[PvNode];
1749 && captureOrPromotion
1750 && pos.type_of_piece_on(move_to(m)) != PAWN
1751 && pos.see_sign(m) >= 0)
1753 result += ONE_PLY / 2;
1757 return Min(result, ONE_PLY);
1761 // connected_threat() tests whether it is safe to forward prune a move or if
1762 // is somehow coonected to the threat move returned by null search.
1764 bool connected_threat(const Position& pos, Move m, Move threat) {
1766 assert(move_is_ok(m));
1767 assert(threat && move_is_ok(threat));
1768 assert(!pos.move_is_check(m));
1769 assert(!pos.move_is_capture_or_promotion(m));
1770 assert(!pos.move_is_passed_pawn_push(m));
1772 Square mfrom, mto, tfrom, tto;
1774 mfrom = move_from(m);
1776 tfrom = move_from(threat);
1777 tto = move_to(threat);
1779 // Case 1: Don't prune moves which move the threatened piece
1783 // Case 2: If the threatened piece has value less than or equal to the
1784 // value of the threatening piece, don't prune move which defend it.
1785 if ( pos.move_is_capture(threat)
1786 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1787 || pos.type_of_piece_on(tfrom) == KING)
1788 && pos.move_attacks_square(m, tto))
1791 // Case 3: If the moving piece in the threatened move is a slider, don't
1792 // prune safe moves which block its ray.
1793 if ( piece_is_slider(pos.piece_on(tfrom))
1794 && bit_is_set(squares_between(tfrom, tto), mto)
1795 && pos.see_sign(m) >= 0)
1802 // ok_to_use_TT() returns true if a transposition table score
1803 // can be used at a given point in search.
1805 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1807 Value v = value_from_tt(tte->value(), ply);
1809 return ( tte->depth() >= depth
1810 || v >= Max(value_mate_in(PLY_MAX), beta)
1811 || v < Min(value_mated_in(PLY_MAX), beta))
1813 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1814 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1818 // refine_eval() returns the transposition table score if
1819 // possible otherwise falls back on static position evaluation.
1821 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1825 Value v = value_from_tt(tte->value(), ply);
1827 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1828 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1835 // update_history() registers a good move that produced a beta-cutoff
1836 // in history and marks as failures all the other moves of that ply.
1838 void update_history(const Position& pos, Move move, Depth depth,
1839 Move movesSearched[], int moveCount) {
1841 Value bonus = Value(int(depth) * int(depth));
1843 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1845 for (int i = 0; i < moveCount - 1; i++)
1847 m = movesSearched[i];
1851 if (!pos.move_is_capture_or_promotion(m))
1852 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1857 // update_killers() add a good move that produced a beta-cutoff
1858 // among the killer moves of that ply.
1860 void update_killers(Move m, Move killers[]) {
1862 if (m == killers[0])
1865 killers[1] = killers[0];
1870 // update_gains() updates the gains table of a non-capture move given
1871 // the static position evaluation before and after the move.
1873 void update_gains(const Position& pos, Move m, Value before, Value after) {
1876 && before != VALUE_NONE
1877 && after != VALUE_NONE
1878 && pos.captured_piece_type() == PIECE_TYPE_NONE
1879 && !move_is_special(m))
1880 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1884 // init_ss_array() does a fast reset of the first entries of a SearchStack
1885 // array and of all the excludedMove and skipNullMove entries.
1887 void init_ss_array(SearchStack* ss, int size) {
1889 for (int i = 0; i < size; i++, ss++)
1891 ss->excludedMove = MOVE_NONE;
1892 ss->skipNullMove = false;
1893 ss->reduction = DEPTH_ZERO;
1897 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1902 // value_to_uci() converts a value to a string suitable for use with the UCI
1903 // protocol specifications:
1905 // cp <x> The score from the engine's point of view in centipawns.
1906 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1907 // use negative values for y.
1909 std::string value_to_uci(Value v) {
1911 std::stringstream s;
1913 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1914 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1916 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1922 // current_search_time() returns the number of milliseconds which have passed
1923 // since the beginning of the current search.
1925 int current_search_time() {
1927 return get_system_time() - SearchStartTime;
1931 // nps() computes the current nodes/second count
1933 int nps(const Position& pos) {
1935 int t = current_search_time();
1936 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1940 // poll() performs two different functions: It polls for user input, and it
1941 // looks at the time consumed so far and decides if it's time to abort the
1944 void poll(const Position& pos) {
1946 static int lastInfoTime;
1947 int t = current_search_time();
1950 if (input_available())
1952 // We are line oriented, don't read single chars
1953 std::string command;
1955 if (!std::getline(std::cin, command))
1958 if (command == "quit")
1960 // Quit the program as soon as possible
1962 QuitRequest = StopRequest = true;
1965 else if (command == "stop")
1967 // Stop calculating as soon as possible, but still send the "bestmove"
1968 // and possibly the "ponder" token when finishing the search.
1972 else if (command == "ponderhit")
1974 // The opponent has played the expected move. GUI sends "ponderhit" if
1975 // we were told to ponder on the same move the opponent has played. We
1976 // should continue searching but switching from pondering to normal search.
1979 if (StopOnPonderhit)
1984 // Print search information
1988 else if (lastInfoTime > t)
1989 // HACK: Must be a new search where we searched less than
1990 // NodesBetweenPolls nodes during the first second of search.
1993 else if (t - lastInfoTime >= 1000)
2000 if (dbg_show_hit_rate)
2001 dbg_print_hit_rate();
2003 // Send info on searched nodes as soon as we return to root
2004 SendSearchedNodes = true;
2007 // Should we stop the search?
2011 bool stillAtFirstMove = FirstRootMove
2012 && !AspirationFailLow
2013 && t > TimeMgr.available_time();
2015 bool noMoreTime = t > TimeMgr.maximum_time()
2016 || stillAtFirstMove;
2018 if ( (UseTimeManagement && noMoreTime)
2019 || (ExactMaxTime && t >= ExactMaxTime)
2020 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2025 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2026 // while the program is pondering. The point is to work around a wrinkle in
2027 // the UCI protocol: When pondering, the engine is not allowed to give a
2028 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2029 // We simply wait here until one of these commands is sent, and return,
2030 // after which the bestmove and pondermove will be printed.
2032 void wait_for_stop_or_ponderhit() {
2034 std::string command;
2038 // Wait for a command from stdin
2039 if (!std::getline(std::cin, command))
2042 if (command == "quit")
2047 else if (command == "ponderhit" || command == "stop")
2053 // init_thread() is the function which is called when a new thread is
2054 // launched. It simply calls the idle_loop() function with the supplied
2055 // threadID. There are two versions of this function; one for POSIX
2056 // threads and one for Windows threads.
2058 #if !defined(_MSC_VER)
2060 void* init_thread(void* threadID) {
2062 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2068 DWORD WINAPI init_thread(LPVOID threadID) {
2070 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2077 /// The ThreadsManager class
2080 // read_uci_options() updates number of active threads and other internal
2081 // parameters according to the UCI options values. It is called before
2082 // to start a new search.
2084 void ThreadsManager::read_uci_options() {
2086 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2087 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2088 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2089 activeThreads = Options["Threads"].value<int>();
2093 // idle_loop() is where the threads are parked when they have no work to do.
2094 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2095 // object for which the current thread is the master.
2097 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2099 assert(threadID >= 0 && threadID < MAX_THREADS);
2102 bool allFinished = false;
2106 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2107 // master should exit as last one.
2108 if (allThreadsShouldExit)
2111 threads[threadID].state = THREAD_TERMINATED;
2115 // If we are not thinking, wait for a condition to be signaled
2116 // instead of wasting CPU time polling for work.
2117 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2118 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2120 assert(!sp || useSleepingThreads);
2121 assert(threadID != 0 || useSleepingThreads);
2123 if (threads[threadID].state == THREAD_INITIALIZING)
2124 threads[threadID].state = THREAD_AVAILABLE;
2126 // Grab the lock to avoid races with wake_sleeping_thread()
2127 lock_grab(&sleepLock[threadID]);
2129 // If we are master and all slaves have finished do not go to sleep
2130 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2131 allFinished = (i == activeThreads);
2133 if (allFinished || allThreadsShouldExit)
2135 lock_release(&sleepLock[threadID]);
2139 // Do sleep here after retesting sleep conditions
2140 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2141 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2143 lock_release(&sleepLock[threadID]);
2146 // If this thread has been assigned work, launch a search
2147 if (threads[threadID].state == THREAD_WORKISWAITING)
2149 assert(!allThreadsShouldExit);
2151 threads[threadID].state = THREAD_SEARCHING;
2153 // Here we call search() with SplitPoint template parameter set to true
2154 SplitPoint* tsp = threads[threadID].splitPoint;
2155 Position pos(*tsp->pos, threadID);
2156 SearchStack* ss = tsp->sstack[threadID] + 1;
2160 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2162 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2164 assert(threads[threadID].state == THREAD_SEARCHING);
2166 threads[threadID].state = THREAD_AVAILABLE;
2168 // Wake up master thread so to allow it to return from the idle loop in
2169 // case we are the last slave of the split point.
2170 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2171 wake_sleeping_thread(tsp->master);
2174 // If this thread is the master of a split point and all slaves have
2175 // finished their work at this split point, return from the idle loop.
2176 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2177 allFinished = (i == activeThreads);
2181 // Because sp->slaves[] is reset under lock protection,
2182 // be sure sp->lock has been released before to return.
2183 lock_grab(&(sp->lock));
2184 lock_release(&(sp->lock));
2186 // In helpful master concept a master can help only a sub-tree, and
2187 // because here is all finished is not possible master is booked.
2188 assert(threads[threadID].state == THREAD_AVAILABLE);
2190 threads[threadID].state = THREAD_SEARCHING;
2197 // init_threads() is called during startup. It launches all helper threads,
2198 // and initializes the split point stack and the global locks and condition
2201 void ThreadsManager::init_threads() {
2203 int i, arg[MAX_THREADS];
2206 // Initialize global locks
2209 for (i = 0; i < MAX_THREADS; i++)
2211 lock_init(&sleepLock[i]);
2212 cond_init(&sleepCond[i]);
2215 // Initialize splitPoints[] locks
2216 for (i = 0; i < MAX_THREADS; i++)
2217 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2218 lock_init(&(threads[i].splitPoints[j].lock));
2220 // Will be set just before program exits to properly end the threads
2221 allThreadsShouldExit = false;
2223 // Threads will be put all threads to sleep as soon as created
2226 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2227 threads[0].state = THREAD_SEARCHING;
2228 for (i = 1; i < MAX_THREADS; i++)
2229 threads[i].state = THREAD_INITIALIZING;
2231 // Launch the helper threads
2232 for (i = 1; i < MAX_THREADS; i++)
2236 #if !defined(_MSC_VER)
2237 pthread_t pthread[1];
2238 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2239 pthread_detach(pthread[0]);
2241 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2245 cout << "Failed to create thread number " << i << endl;
2249 // Wait until the thread has finished launching and is gone to sleep
2250 while (threads[i].state == THREAD_INITIALIZING) {}
2255 // exit_threads() is called when the program exits. It makes all the
2256 // helper threads exit cleanly.
2258 void ThreadsManager::exit_threads() {
2260 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2262 // Wake up all the threads and waits for termination
2263 for (int i = 1; i < MAX_THREADS; i++)
2265 wake_sleeping_thread(i);
2266 while (threads[i].state != THREAD_TERMINATED) {}
2269 // Now we can safely destroy the locks
2270 for (int i = 0; i < MAX_THREADS; i++)
2271 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2272 lock_destroy(&(threads[i].splitPoints[j].lock));
2274 lock_destroy(&mpLock);
2276 // Now we can safely destroy the wait conditions
2277 for (int i = 0; i < MAX_THREADS; i++)
2279 lock_destroy(&sleepLock[i]);
2280 cond_destroy(&sleepCond[i]);
2285 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2286 // the thread's currently active split point, or in some ancestor of
2287 // the current split point.
2289 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2291 assert(threadID >= 0 && threadID < activeThreads);
2293 SplitPoint* sp = threads[threadID].splitPoint;
2295 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2300 // thread_is_available() checks whether the thread with threadID "slave" is
2301 // available to help the thread with threadID "master" at a split point. An
2302 // obvious requirement is that "slave" must be idle. With more than two
2303 // threads, this is not by itself sufficient: If "slave" is the master of
2304 // some active split point, it is only available as a slave to the other
2305 // threads which are busy searching the split point at the top of "slave"'s
2306 // split point stack (the "helpful master concept" in YBWC terminology).
2308 bool ThreadsManager::thread_is_available(int slave, int master) const {
2310 assert(slave >= 0 && slave < activeThreads);
2311 assert(master >= 0 && master < activeThreads);
2312 assert(activeThreads > 1);
2314 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2317 // Make a local copy to be sure doesn't change under our feet
2318 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2320 // No active split points means that the thread is available as
2321 // a slave for any other thread.
2322 if (localActiveSplitPoints == 0 || activeThreads == 2)
2325 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2326 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2327 // could have been set to 0 by another thread leading to an out of bound access.
2328 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2335 // available_thread_exists() tries to find an idle thread which is available as
2336 // a slave for the thread with threadID "master".
2338 bool ThreadsManager::available_thread_exists(int master) const {
2340 assert(master >= 0 && master < activeThreads);
2341 assert(activeThreads > 1);
2343 for (int i = 0; i < activeThreads; i++)
2344 if (thread_is_available(i, master))
2351 // split() does the actual work of distributing the work at a node between
2352 // several available threads. If it does not succeed in splitting the
2353 // node (because no idle threads are available, or because we have no unused
2354 // split point objects), the function immediately returns. If splitting is
2355 // possible, a SplitPoint object is initialized with all the data that must be
2356 // copied to the helper threads and we tell our helper threads that they have
2357 // been assigned work. This will cause them to instantly leave their idle loops and
2358 // call search().When all threads have returned from search() then split() returns.
2360 template <bool Fake>
2361 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2362 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2363 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2364 assert(pos.is_ok());
2365 assert(ply > 0 && ply < PLY_MAX);
2366 assert(*bestValue >= -VALUE_INFINITE);
2367 assert(*bestValue <= *alpha);
2368 assert(*alpha < beta);
2369 assert(beta <= VALUE_INFINITE);
2370 assert(depth > DEPTH_ZERO);
2371 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2372 assert(activeThreads > 1);
2374 int i, master = pos.thread();
2375 Thread& masterThread = threads[master];
2379 // If no other thread is available to help us, or if we have too many
2380 // active split points, don't split.
2381 if ( !available_thread_exists(master)
2382 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2384 lock_release(&mpLock);
2388 // Pick the next available split point object from the split point stack
2389 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2391 // Initialize the split point object
2392 splitPoint.parent = masterThread.splitPoint;
2393 splitPoint.master = master;
2394 splitPoint.betaCutoff = false;
2395 splitPoint.ply = ply;
2396 splitPoint.depth = depth;
2397 splitPoint.threatMove = threatMove;
2398 splitPoint.mateThreat = mateThreat;
2399 splitPoint.alpha = *alpha;
2400 splitPoint.beta = beta;
2401 splitPoint.pvNode = pvNode;
2402 splitPoint.bestValue = *bestValue;
2404 splitPoint.moveCount = moveCount;
2405 splitPoint.pos = &pos;
2406 splitPoint.nodes = 0;
2407 splitPoint.parentSstack = ss;
2408 for (i = 0; i < activeThreads; i++)
2409 splitPoint.slaves[i] = 0;
2411 masterThread.splitPoint = &splitPoint;
2413 // If we are here it means we are not available
2414 assert(masterThread.state != THREAD_AVAILABLE);
2416 int workersCnt = 1; // At least the master is included
2418 // Allocate available threads setting state to THREAD_BOOKED
2419 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2420 if (thread_is_available(i, master))
2422 threads[i].state = THREAD_BOOKED;
2423 threads[i].splitPoint = &splitPoint;
2424 splitPoint.slaves[i] = 1;
2428 assert(Fake || workersCnt > 1);
2430 // We can release the lock because slave threads are already booked and master is not available
2431 lock_release(&mpLock);
2433 // Tell the threads that they have work to do. This will make them leave
2434 // their idle loop. But before copy search stack tail for each thread.
2435 for (i = 0; i < activeThreads; i++)
2436 if (i == master || splitPoint.slaves[i])
2438 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2440 assert(i == master || threads[i].state == THREAD_BOOKED);
2442 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2444 if (useSleepingThreads && i != master)
2445 wake_sleeping_thread(i);
2448 // Everything is set up. The master thread enters the idle loop, from
2449 // which it will instantly launch a search, because its state is
2450 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2451 // idle loop, which means that the main thread will return from the idle
2452 // loop when all threads have finished their work at this split point.
2453 idle_loop(master, &splitPoint);
2455 // We have returned from the idle loop, which means that all threads are
2456 // finished. Update alpha and bestValue, and return.
2459 *alpha = splitPoint.alpha;
2460 *bestValue = splitPoint.bestValue;
2461 masterThread.activeSplitPoints--;
2462 masterThread.splitPoint = splitPoint.parent;
2463 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2465 lock_release(&mpLock);
2469 // wake_sleeping_thread() wakes up the thread with the given threadID
2470 // when it is time to start a new search.
2472 void ThreadsManager::wake_sleeping_thread(int threadID) {
2474 lock_grab(&sleepLock[threadID]);
2475 cond_signal(&sleepCond[threadID]);
2476 lock_release(&sleepLock[threadID]);
2480 /// RootMove and RootMoveList method's definitions
2482 RootMove::RootMove() {
2485 pv_score = non_pv_score = -VALUE_INFINITE;
2489 RootMove& RootMove::operator=(const RootMove& rm) {
2491 const Move* src = rm.pv;
2494 // Avoid a costly full rm.pv[] copy
2495 do *dst++ = *src; while (*src++ != MOVE_NONE);
2498 pv_score = rm.pv_score;
2499 non_pv_score = rm.non_pv_score;
2503 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2504 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2505 // allow to always have a ponder move even when we fail high at root and also a
2506 // long PV to print that is important for position analysis.
2508 void RootMove::extract_pv_from_tt(Position& pos) {
2510 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2514 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2516 pos.do_move(pv[0], *st++);
2518 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2519 && tte->move() != MOVE_NONE
2520 && move_is_legal(pos, tte->move())
2522 && (!pos.is_draw() || ply < 2))
2524 pv[ply] = tte->move();
2525 pos.do_move(pv[ply++], *st++);
2527 pv[ply] = MOVE_NONE;
2529 do pos.undo_move(pv[--ply]); while (ply);
2532 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2533 // the PV back into the TT. This makes sure the old PV moves are searched
2534 // first, even if the old TT entries have been overwritten.
2536 void RootMove::insert_pv_in_tt(Position& pos) {
2538 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2541 Value v, m = VALUE_NONE;
2544 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2548 tte = TT.retrieve(k);
2550 // Don't overwrite exsisting correct entries
2551 if (!tte || tte->move() != pv[ply])
2553 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2554 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2556 pos.do_move(pv[ply], *st++);
2558 } while (pv[++ply] != MOVE_NONE);
2560 do pos.undo_move(pv[--ply]); while (ply);
2563 // pv_info_to_uci() returns a string with information on the current PV line
2564 // formatted according to UCI specification and eventually writes the info
2565 // to a log file. It is called at each iteration or after a new pv is found.
2567 std::string RootMove::pv_info_to_uci(Position& pos, Value alpha, Value beta, int pvLine) {
2569 std::stringstream s, l;
2572 while (*m != MOVE_NONE)
2575 s << "info depth " << Iteration // FIXME
2576 << " seldepth " << int(m - pv)
2577 << " multipv " << pvLine + 1
2578 << " score " << value_to_uci(pv_score)
2579 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2580 << " time " << current_search_time()
2581 << " nodes " << pos.nodes_searched()
2582 << " nps " << nps(pos)
2583 << " pv " << l.str();
2585 if (UseLogFile && pvLine == 0)
2587 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2588 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2590 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2596 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2598 SearchStack ss[PLY_MAX_PLUS_2];
2599 MoveStack mlist[MOVES_MAX];
2603 // Initialize search stack
2604 init_ss_array(ss, PLY_MAX_PLUS_2);
2605 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2607 // Generate all legal moves
2608 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2610 // Add each move to the RootMoveList's vector
2611 for (MoveStack* cur = mlist; cur != last; cur++)
2613 // If we have a searchMoves[] list then verify cur->move
2614 // is in the list before to add it.
2615 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2617 if (searchMoves[0] && *sm != cur->move)
2620 // Find a quick score for the move and add to the list
2621 pos.do_move(cur->move, st);
2624 rm.pv[0] = ss[0].currentMove = cur->move;
2625 rm.pv[1] = MOVE_NONE;
2626 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2629 pos.undo_move(cur->move);
2634 // Score root moves using the standard way used in main search, the moves
2635 // are scored according to the order in which are returned by MovePicker.
2636 // This is the second order score that is used to compare the moves when
2637 // the first order pv scores of both moves are equal.
2639 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2642 Value score = VALUE_ZERO;
2643 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2645 while ((move = mp.get_next_move()) != MOVE_NONE)
2646 for (Base::iterator it = begin(); it != end(); ++it)
2647 if (it->pv[0] == move)
2649 it->non_pv_score = score--;