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, Depth depth, 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 void init(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); }
158 // When formatting a move for std::cout we must know if we are in Chess960
159 // or not. To keep using the handy operator<<() on the move the trick is to
160 // embed this flag in the stream itself. Function-like named enum set960 is
161 // used as a custom manipulator and the stream internal general-purpose array,
162 // accessed through ios_base::iword(), is used to pass the flag to the move's
163 // operator<<() that will use it to properly format castling moves.
166 std::ostream& operator<< (std::ostream& os, const set960& f) {
168 os.iword(0) = int(f);
173 // Overload operator << for moves to make it easier to print moves in
174 // coordinate notation compatible with UCI protocol.
175 std::ostream& operator<<(std::ostream& os, Move m) {
177 bool chess960 = (os.iword(0) != 0); // See set960()
178 return os << move_to_uci(m, chess960);
186 // Maximum depth for razoring
187 const Depth RazorDepth = 4 * ONE_PLY;
189 // Dynamic razoring margin based on depth
190 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
192 // Maximum depth for use of dynamic threat detection when null move fails low
193 const Depth ThreatDepth = 5 * ONE_PLY;
195 // Step 9. Internal iterative deepening
197 // Minimum depth for use of internal iterative deepening
198 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
200 // At Non-PV nodes we do an internal iterative deepening search
201 // when the static evaluation is bigger then beta - IIDMargin.
202 const Value IIDMargin = Value(0x100);
204 // Step 11. Decide the new search depth
206 // Extensions. Configurable UCI options
207 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
208 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
209 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
211 // Minimum depth for use of singular extension
212 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
214 // If the TT move is at least SingularExtensionMargin better then the
215 // remaining ones we will extend it.
216 const Value SingularExtensionMargin = Value(0x20);
218 // Step 12. Futility pruning
220 // Futility margin for quiescence search
221 const Value FutilityMarginQS = Value(0x80);
223 // Futility lookup tables (initialized at startup) and their getter functions
224 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
225 int FutilityMoveCountArray[32]; // [depth]
227 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
228 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
230 // Step 14. Reduced search
232 // Reduction lookup tables (initialized at startup) and their getter functions
233 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
235 template <NodeType PV>
236 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
238 // Common adjustments
240 // Search depth at iteration 1
241 const Depth InitialDepth = ONE_PLY;
243 // Easy move margin. An easy move candidate must be at least this much
244 // better than the second best move.
245 const Value EasyMoveMargin = Value(0x200);
248 /// Namespace variables
253 // Pointer to root move list
259 // Time managment variables
260 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
261 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
262 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
267 std::ofstream LogFile;
269 // Multi-threads manager object
270 ThreadsManager ThreadsMgr;
272 // Node counters, used only by thread[0] but try to keep in different cache
273 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
274 bool SendSearchedNodes;
276 int NodesBetweenPolls = 30000;
283 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
285 template <NodeType PvNode, bool SpNode, bool Root>
286 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
288 template <NodeType PvNode>
289 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
291 template <NodeType PvNode>
292 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
294 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
295 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
298 template <NodeType PvNode>
299 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
301 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
302 bool connected_moves(const Position& pos, Move m1, Move m2);
303 bool value_is_mate(Value value);
304 Value value_to_tt(Value v, int ply);
305 Value value_from_tt(Value v, int ply);
306 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
307 bool connected_threat(const Position& pos, Move m, Move threat);
308 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
309 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
310 void update_killers(Move m, Move killers[]);
311 void update_gains(const Position& pos, Move move, Value before, Value after);
313 int current_search_time();
314 std::string value_to_uci(Value v);
315 int nps(const Position& pos);
316 void poll(const Position& pos);
317 void wait_for_stop_or_ponderhit();
318 void init_ss_array(SearchStack* ss, int size);
320 #if !defined(_MSC_VER)
321 void* init_thread(void* threadID);
323 DWORD WINAPI init_thread(LPVOID threadID);
327 // A dispatcher to choose among different move sources according to the type of node
328 template<bool SpNode, bool Root> struct MovePickerExt;
330 // In Root nodes use RootMoveList Rml as source
331 template<> struct MovePickerExt<false, true> {
333 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack*, Value)
334 : rm(Rml.begin()), firstCall(true) {}
336 Move get_next_move() {
343 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
345 int number_of_evasions() const { return (int)Rml.size(); }
347 RootMoveList::iterator rm;
351 // In SpNodes use split point's shared MovePicker as move source
352 template<> struct MovePickerExt<true, false> {
354 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack* ss, Value)
357 Move get_next_move() { return mp->get_next_move(); }
358 int number_of_evasions() const { return mp->number_of_evasions(); }
360 RootMoveList::iterator rm; // Dummy, never used
364 // Normal case, create and use a MovePicker object as source
365 template<> struct MovePickerExt<false, false> : public MovePicker {
367 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
368 SearchStack* ss, Value beta) : MovePicker(p, ttm, d, h, ss, beta) {}
370 RootMoveList::iterator rm; // Dummy, never used
380 /// init_threads(), exit_threads() and nodes_searched() are helpers to
381 /// give accessibility to some TM methods from outside of current file.
383 void init_threads() { ThreadsMgr.init_threads(); }
384 void exit_threads() { ThreadsMgr.exit_threads(); }
387 /// init_search() is called during startup. It initializes various lookup tables
391 int d; // depth (ONE_PLY == 2)
392 int hd; // half depth (ONE_PLY == 1)
395 // Init reductions array
396 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
398 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
399 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
400 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
401 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
404 // Init futility margins array
405 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
406 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
408 // Init futility move count array
409 for (d = 0; d < 32; d++)
410 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
414 /// perft() is our utility to verify move generation is bug free. All the legal
415 /// moves up to given depth are generated and counted and the sum returned.
417 int64_t perft(Position& pos, Depth depth)
419 MoveStack mlist[MOVES_MAX];
424 // Generate all legal moves
425 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
427 // If we are at the last ply we don't need to do and undo
428 // the moves, just to count them.
429 if (depth <= ONE_PLY)
430 return int(last - mlist);
432 // Loop through all legal moves
434 for (MoveStack* cur = mlist; cur != last; cur++)
437 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
438 sum += perft(pos, depth - ONE_PLY);
445 /// think() is the external interface to Stockfish's search, and is called when
446 /// the program receives the UCI 'go' command. It initializes various
447 /// search-related global variables, and calls id_loop(). It returns false
448 /// when a quit command is received during the search.
450 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
451 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
453 // Initialize global search variables
454 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
456 SearchStartTime = get_system_time();
457 ExactMaxTime = maxTime;
460 InfiniteSearch = infinite;
462 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
464 // Look for a book move, only during games, not tests
465 if (UseTimeManagement && Options["OwnBook"].value<bool>())
467 if (Options["Book File"].value<std::string>() != OpeningBook.name())
468 OpeningBook.open(Options["Book File"].value<std::string>());
470 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
471 if (bookMove != MOVE_NONE)
474 wait_for_stop_or_ponderhit();
476 cout << "bestmove " << bookMove << endl;
481 // Read UCI option values
482 TT.set_size(Options["Hash"].value<int>());
483 if (Options["Clear Hash"].value<bool>())
485 Options["Clear Hash"].set_value("false");
489 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
490 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
491 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
492 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
493 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
494 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
495 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
496 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
497 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
498 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
499 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
500 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
501 MultiPV = Options["MultiPV"].value<int>();
502 UseLogFile = Options["Use Search Log"].value<bool>();
504 read_evaluation_uci_options(pos.side_to_move());
506 // Set the number of active threads
507 ThreadsMgr.read_uci_options();
508 init_eval(ThreadsMgr.active_threads());
510 // Wake up needed threads
511 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
512 ThreadsMgr.wake_sleeping_thread(i);
515 int myTime = time[pos.side_to_move()];
516 int myIncrement = increment[pos.side_to_move()];
517 if (UseTimeManagement)
518 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
520 // Set best NodesBetweenPolls interval to avoid lagging under
521 // heavy time pressure.
523 NodesBetweenPolls = Min(MaxNodes, 30000);
524 else if (myTime && myTime < 1000)
525 NodesBetweenPolls = 1000;
526 else if (myTime && myTime < 5000)
527 NodesBetweenPolls = 5000;
529 NodesBetweenPolls = 30000;
531 // Write search information to log file
534 std::string name = Options["Search Log Filename"].value<std::string>();
535 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
537 LogFile << "Searching: " << pos.to_fen()
538 << "\ninfinite: " << infinite
539 << " ponder: " << ponder
540 << " time: " << myTime
541 << " increment: " << myIncrement
542 << " moves to go: " << movesToGo << endl;
545 // We're ready to start thinking. Call the iterative deepening loop function
546 Move ponderMove = MOVE_NONE;
547 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
549 // Print final search statistics
550 cout << "info nodes " << pos.nodes_searched()
551 << " nps " << nps(pos)
552 << " time " << current_search_time() << endl;
556 LogFile << "\nNodes: " << pos.nodes_searched()
557 << "\nNodes/second: " << nps(pos)
558 << "\nBest move: " << move_to_san(pos, bestMove);
561 pos.do_move(bestMove, st);
562 LogFile << "\nPonder move: "
563 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
566 // Return from think() with unchanged position
567 pos.undo_move(bestMove);
572 // This makes all the threads to go to sleep
573 ThreadsMgr.set_active_threads(1);
575 // If we are pondering or in infinite search, we shouldn't print the
576 // best move before we are told to do so.
577 if (!StopRequest && (Pondering || InfiniteSearch))
578 wait_for_stop_or_ponderhit();
580 // Could be both MOVE_NONE when searching on a stalemate position
581 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
589 // id_loop() is the main iterative deepening loop. It calls search()
590 // repeatedly with increasing depth until the allocated thinking time has
591 // been consumed, the user stops the search, or the maximum search depth is
594 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
596 SearchStack ss[PLY_MAX_PLUS_2];
597 Value bestValues[PLY_MAX_PLUS_2];
598 int bestMoveChanges[PLY_MAX_PLUS_2];
599 int iteration, researchCountFL, researchCountFH, aspirationDelta;
600 Value value, alpha, beta;
604 // Moves to search are verified, scored and sorted
605 Rml.init(pos, searchMoves);
607 // Initialize FIXME move before Rml.init()
610 init_ss_array(ss, PLY_MAX_PLUS_2);
611 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
612 EasyMove = MOVE_NONE;
616 // Handle special case of searching on a mate/stale position
619 cout << "info depth " << iteration << " score "
620 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
626 // Send initial scoring (iteration 1)
627 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
628 << "info depth " << iteration
629 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
631 // Is one move significantly better than others after initial scoring ?
633 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
634 EasyMove = Rml[0].pv[0];
636 // Iterative deepening loop
637 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
639 cout << "info depth " << iteration << endl;
641 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
642 depth = (iteration - 2) * ONE_PLY + InitialDepth;
644 // Calculate dynamic aspiration window based on previous iterations
645 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
647 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
648 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
650 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
651 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
653 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
654 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
657 // We start with small aspiration window and in case of fail high/low, we
658 // research with bigger window until we are not failing high/low anymore.
661 // Sort the moves before to (re)search
662 Rml.set_non_pv_scores(pos, Rml[0].pv[0], ss);
665 // Search to the current depth
666 value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
668 // Sort the moves and write PV lines to transposition table, in case
669 // the relevant entries have been overwritten during the search.
671 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
672 Rml[i].insert_pv_in_tt(pos);
674 // Value cannot be trusted. Break out immediately!
678 assert(value >= alpha);
680 bestMoveChanges[iteration] = Rml.bestMoveChanges; // FIXME move outside fail high/low loop
682 // In case of failing high/low increase aspiration window and research,
683 // otherwise exit the fail high/low loop.
686 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
689 else if (value <= alpha)
691 AspirationFailLow = true;
692 StopOnPonderhit = false;
694 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
701 //Save info about search result
702 bestValues[iteration] = value;
704 // Drop the easy move if differs from the new best move
705 if (Rml[0].pv[0] != EasyMove)
706 EasyMove = MOVE_NONE;
708 if (UseTimeManagement && !StopRequest)
711 bool noMoreTime = false;
713 // Stop search early if there is only a single legal move,
714 // we search up to Iteration 6 anyway to get a proper score.
715 if (iteration >= 6 && Rml.size() == 1)
718 // Stop search early when the last two iterations returned a mate score
720 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
721 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
724 // Stop search early if one move seems to be much better than the others
726 && EasyMove == Rml[0].pv[0]
727 && ( ( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
728 && current_search_time() > TimeMgr.available_time() / 16)
729 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
730 && current_search_time() > TimeMgr.available_time() / 32)))
733 // Add some extra time if the best move has changed during the last two iterations
734 if (iteration > 5 && iteration <= 50)
735 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
737 // Stop search if most of MaxSearchTime is consumed at the end of the
738 // iteration. We probably don't have enough time to search the first
739 // move at the next iteration anyway.
740 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
746 StopOnPonderhit = true;
753 *ponderMove = Rml[0].pv[1];
758 // search<>() is the main search function for both PV and non-PV nodes and for
759 // normal and SplitPoint nodes. When called just after a split point the search
760 // is simpler because we have already probed the hash table, done a null move
761 // search, and searched the first move before splitting, we don't have to repeat
762 // all this work again. We also don't need to store anything to the hash table
763 // here: This is taken care of after we return from the split point.
765 template <NodeType PvNode, bool SpNode, bool Root>
766 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
768 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
769 assert(beta > alpha && beta <= VALUE_INFINITE);
770 assert(PvNode || alpha == beta - 1);
771 assert((Root || ply > 0) && ply < PLY_MAX);
772 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
774 Move movesSearched[MOVES_MAX];
779 Move ttMove, move, excludedMove, threatMove;
782 Value bestValue, value, oldAlpha;
783 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
784 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
785 bool mateThreat = false;
787 int threadID = pos.thread();
788 SplitPoint* sp = NULL;
790 refinedValue = bestValue = value = -VALUE_INFINITE;
792 isCheck = pos.is_check();
798 ttMove = excludedMove = MOVE_NONE;
799 threatMove = sp->threatMove;
800 mateThreat = sp->mateThreat;
801 goto split_point_start;
805 else {} // Hack to fix icc's "statement is unreachable" warning
807 // Step 1. Initialize node and poll. Polling can abort search
808 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
809 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
813 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
819 // Step 2. Check for aborted search and immediate draw
821 || ThreadsMgr.cutoff_at_splitpoint(threadID)
823 || ply >= PLY_MAX - 1)
826 // Step 3. Mate distance pruning
827 alpha = Max(value_mated_in(ply), alpha);
828 beta = Min(value_mate_in(ply+1), beta);
833 // Step 4. Transposition table lookup
835 // We don't want the score of a partial search to overwrite a previous full search
836 // TT value, so we use a different position key in case of an excluded move exists.
837 excludedMove = ss->excludedMove;
838 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
840 tte = TT.retrieve(posKey);
841 ttMove = tte ? tte->move() : MOVE_NONE;
843 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
844 // This is to avoid problems in the following areas:
846 // * Repetition draw detection
847 // * Fifty move rule detection
848 // * Searching for a mate
849 // * Printing of full PV line
850 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
853 ss->bestMove = ttMove; // Can be MOVE_NONE
854 return value_from_tt(tte->value(), ply);
857 // Step 5. Evaluate the position statically and
858 // update gain statistics of parent move.
860 ss->eval = ss->evalMargin = VALUE_NONE;
863 assert(tte->static_value() != VALUE_NONE);
865 ss->eval = tte->static_value();
866 ss->evalMargin = tte->static_value_margin();
867 refinedValue = refine_eval(tte, ss->eval, ply);
871 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
872 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
875 // Save gain for the parent non-capture move
877 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
879 // Step 6. Razoring (is omitted in PV nodes)
881 && depth < RazorDepth
883 && refinedValue < beta - razor_margin(depth)
884 && ttMove == MOVE_NONE
885 && !value_is_mate(beta)
886 && !pos.has_pawn_on_7th(pos.side_to_move()))
888 Value rbeta = beta - razor_margin(depth);
889 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
891 // Logically we should return (v + razor_margin(depth)), but
892 // surprisingly this did slightly weaker in tests.
896 // Step 7. Static null move pruning (is omitted in PV nodes)
897 // We're betting that the opponent doesn't have a move that will reduce
898 // the score by more than futility_margin(depth) if we do a null move.
901 && depth < RazorDepth
903 && refinedValue >= beta + futility_margin(depth, 0)
904 && !value_is_mate(beta)
905 && pos.non_pawn_material(pos.side_to_move()))
906 return refinedValue - futility_margin(depth, 0);
908 // Step 8. Null move search with verification search (is omitted in PV nodes)
913 && refinedValue >= beta
914 && !value_is_mate(beta)
915 && pos.non_pawn_material(pos.side_to_move()))
917 ss->currentMove = MOVE_NULL;
919 // Null move dynamic reduction based on depth
920 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
922 // Null move dynamic reduction based on value
923 if (refinedValue - beta > PawnValueMidgame)
926 pos.do_null_move(st);
927 (ss+1)->skipNullMove = true;
928 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
929 (ss+1)->skipNullMove = false;
930 pos.undo_null_move();
932 if (nullValue >= beta)
934 // Do not return unproven mate scores
935 if (nullValue >= value_mate_in(PLY_MAX))
938 if (depth < 6 * ONE_PLY)
941 // Do verification search at high depths
942 ss->skipNullMove = true;
943 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
944 ss->skipNullMove = false;
951 // The null move failed low, which means that we may be faced with
952 // some kind of threat. If the previous move was reduced, check if
953 // the move that refuted the null move was somehow connected to the
954 // move which was reduced. If a connection is found, return a fail
955 // low score (which will cause the reduced move to fail high in the
956 // parent node, which will trigger a re-search with full depth).
957 if (nullValue == value_mated_in(ply + 2))
960 threatMove = (ss+1)->bestMove;
961 if ( depth < ThreatDepth
963 && threatMove != MOVE_NONE
964 && connected_moves(pos, (ss-1)->currentMove, threatMove))
969 // Step 9. Internal iterative deepening
971 && depth >= IIDDepth[PvNode]
972 && ttMove == MOVE_NONE
973 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
975 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
977 ss->skipNullMove = true;
978 search<PvNode>(pos, ss, alpha, beta, d, ply);
979 ss->skipNullMove = false;
981 ttMove = ss->bestMove;
982 tte = TT.retrieve(posKey);
985 // Expensive mate threat detection (only for PV nodes)
986 if (PvNode && !Root) // FIXME
987 mateThreat = pos.has_mate_threat();
989 split_point_start: // At split points actual search starts from here
991 // Initialize a MovePicker object for the current position
992 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
994 ss->bestMove = MOVE_NONE;
995 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
996 futilityBase = ss->eval + ss->evalMargin;
997 singularExtensionNode = !Root
999 && depth >= SingularExtensionDepth[PvNode]
1002 && !excludedMove // Do not allow recursive singular extension search
1003 && (tte->type() & VALUE_TYPE_LOWER)
1004 && tte->depth() >= depth - 3 * ONE_PLY;
1007 lock_grab(&(sp->lock));
1008 bestValue = sp->bestValue;
1011 // Step 10. Loop through moves
1012 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1013 while ( bestValue < beta
1014 && (move = mp.get_next_move()) != MOVE_NONE
1015 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1017 assert(move_is_ok(move));
1021 moveCount = ++sp->moveCount;
1022 lock_release(&(sp->lock));
1024 else if (move == excludedMove)
1027 movesSearched[moveCount++] = move;
1031 // This is used by time management
1032 FirstRootMove = (moveCount == 1);
1034 // Save the current node count before the move is searched
1035 nodes = pos.nodes_searched();
1037 // If it's time to send nodes info, do it here where we have the
1038 // correct accumulated node counts searched by each thread.
1039 if (SendSearchedNodes)
1041 SendSearchedNodes = false;
1042 cout << "info nodes " << nodes
1043 << " nps " << nps(pos)
1044 << " time " << current_search_time() << endl;
1047 if (current_search_time() >= 1000)
1048 cout << "info currmove " << move
1049 << " currmovenumber " << moveCount << endl;
1052 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1053 moveIsCheck = pos.move_is_check(move, ci);
1054 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1056 // Step 11. Decide the new search depth
1057 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1059 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1060 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1061 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1062 // lower then ttValue minus a margin then we extend ttMove.
1063 if ( singularExtensionNode
1064 && move == tte->move()
1067 Value ttValue = value_from_tt(tte->value(), ply);
1069 if (abs(ttValue) < VALUE_KNOWN_WIN)
1071 Value b = ttValue - SingularExtensionMargin;
1072 ss->excludedMove = move;
1073 ss->skipNullMove = true;
1074 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1075 ss->skipNullMove = false;
1076 ss->excludedMove = MOVE_NONE;
1077 ss->bestMove = MOVE_NONE;
1083 // Update current move (this must be done after singular extension search)
1084 ss->currentMove = move;
1085 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1087 // Step 12. Futility pruning (is omitted in PV nodes)
1089 && !captureOrPromotion
1093 && !move_is_castle(move))
1095 // Move count based pruning
1096 if ( moveCount >= futility_move_count(depth)
1097 && !(threatMove && connected_threat(pos, move, threatMove))
1098 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1101 lock_grab(&(sp->lock));
1106 // Value based pruning
1107 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1108 // but fixing this made program slightly weaker.
1109 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1110 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1111 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1113 if (futilityValueScaled < beta)
1117 lock_grab(&(sp->lock));
1118 if (futilityValueScaled > sp->bestValue)
1119 sp->bestValue = bestValue = futilityValueScaled;
1121 else if (futilityValueScaled > bestValue)
1122 bestValue = futilityValueScaled;
1127 // Prune moves with negative SEE at low depths
1128 if ( predictedDepth < 2 * ONE_PLY
1129 && bestValue > value_mated_in(PLY_MAX)
1130 && pos.see_sign(move) < 0)
1133 lock_grab(&(sp->lock));
1139 // Step 13. Make the move
1140 pos.do_move(move, st, ci, moveIsCheck);
1142 // Step extra. pv search (only in PV nodes)
1143 // The first move in list is the expected PV
1146 // Aspiration window is disabled in multi-pv case
1147 if (Root && MultiPV > 1)
1148 alpha = -VALUE_INFINITE;
1150 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1154 // Step 14. Reduced depth search
1155 // If the move fails high will be re-searched at full depth.
1156 bool doFullDepthSearch = true;
1158 if ( depth >= 3 * ONE_PLY
1159 && !captureOrPromotion
1161 && !move_is_castle(move)
1162 && ss->killers[0] != move
1163 && ss->killers[1] != move)
1165 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1166 : reduction<PvNode>(depth, moveCount);
1169 alpha = SpNode ? sp->alpha : alpha;
1170 Depth d = newDepth - ss->reduction;
1171 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1173 doFullDepthSearch = (value > alpha);
1175 ss->reduction = DEPTH_ZERO; // Restore original reduction
1178 // Step 15. Full depth search
1179 if (doFullDepthSearch)
1181 alpha = SpNode ? sp->alpha : alpha;
1182 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1184 // Step extra. pv search (only in PV nodes)
1185 // Search only for possible new PV nodes, if instead value >= beta then
1186 // parent node fails low with value <= alpha and tries another move.
1187 if (PvNode && value > alpha && (Root || value < beta))
1188 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1192 // Step 16. Undo move
1193 pos.undo_move(move);
1195 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1197 // Step 17. Check for new best move
1200 lock_grab(&(sp->lock));
1201 bestValue = sp->bestValue;
1205 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1210 sp->bestValue = value;
1214 if (PvNode && value < beta) // We want always alpha < beta
1222 sp->betaCutoff = true;
1224 if (value == value_mate_in(ply + 1))
1225 ss->mateKiller = move;
1227 ss->bestMove = move;
1230 sp->parentSstack->bestMove = move;
1236 // Finished searching the move. If StopRequest is true, the search
1237 // was aborted because the user interrupted the search or because we
1238 // ran out of time. In this case, the return value of the search cannot
1239 // be trusted, and we break out of the loop without updating the best
1244 // Remember searched nodes counts for this move
1245 mp.rm->nodes += pos.nodes_searched() - nodes;
1247 // Step 17. Check for new best move
1248 if (!isPvMove && value <= alpha)
1249 mp.rm->pv_score = -VALUE_INFINITE;
1252 // PV move or new best move!
1255 ss->bestMove = move;
1256 mp.rm->pv_score = value;
1257 mp.rm->extract_pv_from_tt(pos);
1259 // We record how often the best move has been changed in each
1260 // iteration. This information is used for time managment: When
1261 // the best move changes frequently, we allocate some more time.
1262 if (!isPvMove && MultiPV == 1)
1263 Rml.bestMoveChanges++;
1265 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1266 // requires we send all the PV lines properly sorted.
1267 Rml.sort_multipv(moveCount);
1269 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1270 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1272 // Update alpha. In multi-pv we don't use aspiration window
1275 // Raise alpha to setup proper non-pv search upper bound
1277 alpha = bestValue = value;
1279 else // Set alpha equal to minimum score among the PV lines
1280 alpha = bestValue = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1282 } // PV move or new best move
1285 // Step 18. Check for split
1288 && depth >= ThreadsMgr.min_split_depth()
1289 && ThreadsMgr.active_threads() > 1
1291 && ThreadsMgr.available_thread_exists(threadID)
1293 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1294 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1295 threatMove, mateThreat, moveCount, (MovePicker*)&mp, PvNode);
1298 // Step 19. Check for mate and stalemate
1299 // All legal moves have been searched and if there are
1300 // no legal moves, it must be mate or stalemate.
1301 // If one move was excluded return fail low score.
1302 if (!SpNode && !moveCount)
1303 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1305 // Step 20. Update tables
1306 // If the search is not aborted, update the transposition table,
1307 // history counters, and killer moves.
1308 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1310 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1311 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1312 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1314 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1316 // Update killers and history only for non capture moves that fails high
1317 if ( bestValue >= beta
1318 && !pos.move_is_capture_or_promotion(move))
1320 update_history(pos, move, depth, movesSearched, moveCount);
1321 update_killers(move, ss->killers);
1327 // Here we have the lock still grabbed
1328 sp->slaves[threadID] = 0;
1329 sp->nodes += pos.nodes_searched();
1330 lock_release(&(sp->lock));
1333 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1338 // qsearch() is the quiescence search function, which is called by the main
1339 // search function when the remaining depth is zero (or, to be more precise,
1340 // less than ONE_PLY).
1342 template <NodeType PvNode>
1343 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1345 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1346 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1347 assert(PvNode || alpha == beta - 1);
1349 assert(ply > 0 && ply < PLY_MAX);
1350 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1354 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1355 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1358 Value oldAlpha = alpha;
1360 ss->bestMove = ss->currentMove = MOVE_NONE;
1362 // Check for an instant draw or maximum ply reached
1363 if (pos.is_draw() || ply >= PLY_MAX - 1)
1366 // Decide whether or not to include checks, this fixes also the type of
1367 // TT entry depth that we are going to use. Note that in qsearch we use
1368 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1369 isCheck = pos.is_check();
1370 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1372 // Transposition table lookup. At PV nodes, we don't use the TT for
1373 // pruning, but only for move ordering.
1374 tte = TT.retrieve(pos.get_key());
1375 ttMove = (tte ? tte->move() : MOVE_NONE);
1377 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1379 ss->bestMove = ttMove; // Can be MOVE_NONE
1380 return value_from_tt(tte->value(), ply);
1383 // Evaluate the position statically
1386 bestValue = futilityBase = -VALUE_INFINITE;
1387 ss->eval = evalMargin = VALUE_NONE;
1388 enoughMaterial = false;
1394 assert(tte->static_value() != VALUE_NONE);
1396 evalMargin = tte->static_value_margin();
1397 ss->eval = bestValue = tte->static_value();
1400 ss->eval = bestValue = evaluate(pos, evalMargin);
1402 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1404 // Stand pat. Return immediately if static value is at least beta
1405 if (bestValue >= beta)
1408 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1413 if (PvNode && bestValue > alpha)
1416 // Futility pruning parameters, not needed when in check
1417 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1418 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1421 // Initialize a MovePicker object for the current position, and prepare
1422 // to search the moves. Because the depth is <= 0 here, only captures,
1423 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1425 MovePicker mp(pos, ttMove, depth, H);
1428 // Loop through the moves until no moves remain or a beta cutoff occurs
1429 while ( alpha < beta
1430 && (move = mp.get_next_move()) != MOVE_NONE)
1432 assert(move_is_ok(move));
1434 moveIsCheck = pos.move_is_check(move, ci);
1442 && !move_is_promotion(move)
1443 && !pos.move_is_passed_pawn_push(move))
1445 futilityValue = futilityBase
1446 + pos.endgame_value_of_piece_on(move_to(move))
1447 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1449 if (futilityValue < alpha)
1451 if (futilityValue > bestValue)
1452 bestValue = futilityValue;
1457 // Detect non-capture evasions that are candidate to be pruned
1458 evasionPrunable = isCheck
1459 && bestValue > value_mated_in(PLY_MAX)
1460 && !pos.move_is_capture(move)
1461 && !pos.can_castle(pos.side_to_move());
1463 // Don't search moves with negative SEE values
1465 && (!isCheck || evasionPrunable)
1467 && !move_is_promotion(move)
1468 && pos.see_sign(move) < 0)
1471 // Don't search useless checks
1476 && !pos.move_is_capture_or_promotion(move)
1477 && ss->eval + PawnValueMidgame / 4 < beta
1478 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1480 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1481 bestValue = ss->eval + PawnValueMidgame / 4;
1486 // Update current move
1487 ss->currentMove = move;
1489 // Make and search the move
1490 pos.do_move(move, st, ci, moveIsCheck);
1491 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1492 pos.undo_move(move);
1494 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1497 if (value > bestValue)
1503 ss->bestMove = move;
1508 // All legal moves have been searched. A special case: If we're in check
1509 // and no legal moves were found, it is checkmate.
1510 if (isCheck && bestValue == -VALUE_INFINITE)
1511 return value_mated_in(ply);
1513 // Update transposition table
1514 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1515 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1517 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1523 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1524 // bestValue is updated only when returning false because in that case move
1527 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1529 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1530 Square from, to, ksq, victimSq;
1533 Value futilityValue, bv = *bestValue;
1535 from = move_from(move);
1537 them = opposite_color(pos.side_to_move());
1538 ksq = pos.king_square(them);
1539 kingAtt = pos.attacks_from<KING>(ksq);
1540 pc = pos.piece_on(from);
1542 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1543 oldAtt = pos.attacks_from(pc, from, occ);
1544 newAtt = pos.attacks_from(pc, to, occ);
1546 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1547 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1549 if (!(b && (b & (b - 1))))
1552 // Rule 2. Queen contact check is very dangerous
1553 if ( type_of_piece(pc) == QUEEN
1554 && bit_is_set(kingAtt, to))
1557 // Rule 3. Creating new double threats with checks
1558 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1562 victimSq = pop_1st_bit(&b);
1563 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1565 // Note that here we generate illegal "double move"!
1566 if ( futilityValue >= beta
1567 && pos.see_sign(make_move(from, victimSq)) >= 0)
1570 if (futilityValue > bv)
1574 // Update bestValue only if check is not dangerous (because we will prune the move)
1580 // connected_moves() tests whether two moves are 'connected' in the sense
1581 // that the first move somehow made the second move possible (for instance
1582 // if the moving piece is the same in both moves). The first move is assumed
1583 // to be the move that was made to reach the current position, while the
1584 // second move is assumed to be a move from the current position.
1586 bool connected_moves(const Position& pos, Move m1, Move m2) {
1588 Square f1, t1, f2, t2;
1591 assert(m1 && move_is_ok(m1));
1592 assert(m2 && move_is_ok(m2));
1594 // Case 1: The moving piece is the same in both moves
1600 // Case 2: The destination square for m2 was vacated by m1
1606 // Case 3: Moving through the vacated square
1607 if ( piece_is_slider(pos.piece_on(f2))
1608 && bit_is_set(squares_between(f2, t2), f1))
1611 // Case 4: The destination square for m2 is defended by the moving piece in m1
1612 p = pos.piece_on(t1);
1613 if (bit_is_set(pos.attacks_from(p, t1), t2))
1616 // Case 5: Discovered check, checking piece is the piece moved in m1
1617 if ( piece_is_slider(p)
1618 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1619 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1621 // discovered_check_candidates() works also if the Position's side to
1622 // move is the opposite of the checking piece.
1623 Color them = opposite_color(pos.side_to_move());
1624 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1626 if (bit_is_set(dcCandidates, f2))
1633 // value_is_mate() checks if the given value is a mate one eventually
1634 // compensated for the ply.
1636 bool value_is_mate(Value value) {
1638 assert(abs(value) <= VALUE_INFINITE);
1640 return value <= value_mated_in(PLY_MAX)
1641 || value >= value_mate_in(PLY_MAX);
1645 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1646 // "plies to mate from the current ply". Non-mate scores are unchanged.
1647 // The function is called before storing a value to the transposition table.
1649 Value value_to_tt(Value v, int ply) {
1651 if (v >= value_mate_in(PLY_MAX))
1654 if (v <= value_mated_in(PLY_MAX))
1661 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1662 // the transposition table to a mate score corrected for the current ply.
1664 Value value_from_tt(Value v, int ply) {
1666 if (v >= value_mate_in(PLY_MAX))
1669 if (v <= value_mated_in(PLY_MAX))
1676 // extension() decides whether a move should be searched with normal depth,
1677 // or with extended depth. Certain classes of moves (checking moves, in
1678 // particular) are searched with bigger depth than ordinary moves and in
1679 // any case are marked as 'dangerous'. Note that also if a move is not
1680 // extended, as example because the corresponding UCI option is set to zero,
1681 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1682 template <NodeType PvNode>
1683 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1684 bool singleEvasion, bool mateThreat, bool* dangerous) {
1686 assert(m != MOVE_NONE);
1688 Depth result = DEPTH_ZERO;
1689 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1693 if (moveIsCheck && pos.see_sign(m) >= 0)
1694 result += CheckExtension[PvNode];
1697 result += SingleEvasionExtension[PvNode];
1700 result += MateThreatExtension[PvNode];
1703 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1705 Color c = pos.side_to_move();
1706 if (relative_rank(c, move_to(m)) == RANK_7)
1708 result += PawnPushTo7thExtension[PvNode];
1711 if (pos.pawn_is_passed(c, move_to(m)))
1713 result += PassedPawnExtension[PvNode];
1718 if ( captureOrPromotion
1719 && pos.type_of_piece_on(move_to(m)) != PAWN
1720 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1721 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1722 && !move_is_promotion(m)
1725 result += PawnEndgameExtension[PvNode];
1730 && captureOrPromotion
1731 && pos.type_of_piece_on(move_to(m)) != PAWN
1732 && pos.see_sign(m) >= 0)
1734 result += ONE_PLY / 2;
1738 return Min(result, ONE_PLY);
1742 // connected_threat() tests whether it is safe to forward prune a move or if
1743 // is somehow coonected to the threat move returned by null search.
1745 bool connected_threat(const Position& pos, Move m, Move threat) {
1747 assert(move_is_ok(m));
1748 assert(threat && move_is_ok(threat));
1749 assert(!pos.move_is_check(m));
1750 assert(!pos.move_is_capture_or_promotion(m));
1751 assert(!pos.move_is_passed_pawn_push(m));
1753 Square mfrom, mto, tfrom, tto;
1755 mfrom = move_from(m);
1757 tfrom = move_from(threat);
1758 tto = move_to(threat);
1760 // Case 1: Don't prune moves which move the threatened piece
1764 // Case 2: If the threatened piece has value less than or equal to the
1765 // value of the threatening piece, don't prune move which defend it.
1766 if ( pos.move_is_capture(threat)
1767 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1768 || pos.type_of_piece_on(tfrom) == KING)
1769 && pos.move_attacks_square(m, tto))
1772 // Case 3: If the moving piece in the threatened move is a slider, don't
1773 // prune safe moves which block its ray.
1774 if ( piece_is_slider(pos.piece_on(tfrom))
1775 && bit_is_set(squares_between(tfrom, tto), mto)
1776 && pos.see_sign(m) >= 0)
1783 // ok_to_use_TT() returns true if a transposition table score
1784 // can be used at a given point in search.
1786 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1788 Value v = value_from_tt(tte->value(), ply);
1790 return ( tte->depth() >= depth
1791 || v >= Max(value_mate_in(PLY_MAX), beta)
1792 || v < Min(value_mated_in(PLY_MAX), beta))
1794 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1795 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1799 // refine_eval() returns the transposition table score if
1800 // possible otherwise falls back on static position evaluation.
1802 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1806 Value v = value_from_tt(tte->value(), ply);
1808 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1809 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1816 // update_history() registers a good move that produced a beta-cutoff
1817 // in history and marks as failures all the other moves of that ply.
1819 void update_history(const Position& pos, Move move, Depth depth,
1820 Move movesSearched[], int moveCount) {
1822 Value bonus = Value(int(depth) * int(depth));
1824 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1826 for (int i = 0; i < moveCount - 1; i++)
1828 m = movesSearched[i];
1832 if (!pos.move_is_capture_or_promotion(m))
1833 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1838 // update_killers() add a good move that produced a beta-cutoff
1839 // among the killer moves of that ply.
1841 void update_killers(Move m, Move killers[]) {
1843 if (m == killers[0])
1846 killers[1] = killers[0];
1851 // update_gains() updates the gains table of a non-capture move given
1852 // the static position evaluation before and after the move.
1854 void update_gains(const Position& pos, Move m, Value before, Value after) {
1857 && before != VALUE_NONE
1858 && after != VALUE_NONE
1859 && pos.captured_piece_type() == PIECE_TYPE_NONE
1860 && !move_is_special(m))
1861 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1865 // init_ss_array() does a fast reset of the first entries of a SearchStack
1866 // array and of all the excludedMove and skipNullMove entries.
1868 void init_ss_array(SearchStack* ss, int size) {
1870 for (int i = 0; i < size; i++, ss++)
1872 ss->excludedMove = MOVE_NONE;
1873 ss->skipNullMove = false;
1874 ss->reduction = DEPTH_ZERO;
1878 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1883 // value_to_uci() converts a value to a string suitable for use with the UCI
1884 // protocol specifications:
1886 // cp <x> The score from the engine's point of view in centipawns.
1887 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1888 // use negative values for y.
1890 std::string value_to_uci(Value v) {
1892 std::stringstream s;
1894 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1895 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1897 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1903 // current_search_time() returns the number of milliseconds which have passed
1904 // since the beginning of the current search.
1906 int current_search_time() {
1908 return get_system_time() - SearchStartTime;
1912 // nps() computes the current nodes/second count
1914 int nps(const Position& pos) {
1916 int t = current_search_time();
1917 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1921 // poll() performs two different functions: It polls for user input, and it
1922 // looks at the time consumed so far and decides if it's time to abort the
1925 void poll(const Position& pos) {
1927 static int lastInfoTime;
1928 int t = current_search_time();
1931 if (input_available())
1933 // We are line oriented, don't read single chars
1934 std::string command;
1936 if (!std::getline(std::cin, command))
1939 if (command == "quit")
1941 // Quit the program as soon as possible
1943 QuitRequest = StopRequest = true;
1946 else if (command == "stop")
1948 // Stop calculating as soon as possible, but still send the "bestmove"
1949 // and possibly the "ponder" token when finishing the search.
1953 else if (command == "ponderhit")
1955 // The opponent has played the expected move. GUI sends "ponderhit" if
1956 // we were told to ponder on the same move the opponent has played. We
1957 // should continue searching but switching from pondering to normal search.
1960 if (StopOnPonderhit)
1965 // Print search information
1969 else if (lastInfoTime > t)
1970 // HACK: Must be a new search where we searched less than
1971 // NodesBetweenPolls nodes during the first second of search.
1974 else if (t - lastInfoTime >= 1000)
1981 if (dbg_show_hit_rate)
1982 dbg_print_hit_rate();
1984 // Send info on searched nodes as soon as we return to root
1985 SendSearchedNodes = true;
1988 // Should we stop the search?
1992 bool stillAtFirstMove = FirstRootMove
1993 && !AspirationFailLow
1994 && t > TimeMgr.available_time();
1996 bool noMoreTime = t > TimeMgr.maximum_time()
1997 || stillAtFirstMove;
1999 if ( (UseTimeManagement && noMoreTime)
2000 || (ExactMaxTime && t >= ExactMaxTime)
2001 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2006 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2007 // while the program is pondering. The point is to work around a wrinkle in
2008 // the UCI protocol: When pondering, the engine is not allowed to give a
2009 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2010 // We simply wait here until one of these commands is sent, and return,
2011 // after which the bestmove and pondermove will be printed.
2013 void wait_for_stop_or_ponderhit() {
2015 std::string command;
2019 // Wait for a command from stdin
2020 if (!std::getline(std::cin, command))
2023 if (command == "quit")
2028 else if (command == "ponderhit" || command == "stop")
2034 // init_thread() is the function which is called when a new thread is
2035 // launched. It simply calls the idle_loop() function with the supplied
2036 // threadID. There are two versions of this function; one for POSIX
2037 // threads and one for Windows threads.
2039 #if !defined(_MSC_VER)
2041 void* init_thread(void* threadID) {
2043 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2049 DWORD WINAPI init_thread(LPVOID threadID) {
2051 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2058 /// The ThreadsManager class
2061 // read_uci_options() updates number of active threads and other internal
2062 // parameters according to the UCI options values. It is called before
2063 // to start a new search.
2065 void ThreadsManager::read_uci_options() {
2067 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2068 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2069 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2070 activeThreads = Options["Threads"].value<int>();
2074 // idle_loop() is where the threads are parked when they have no work to do.
2075 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2076 // object for which the current thread is the master.
2078 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2080 assert(threadID >= 0 && threadID < MAX_THREADS);
2083 bool allFinished = false;
2087 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2088 // master should exit as last one.
2089 if (allThreadsShouldExit)
2092 threads[threadID].state = THREAD_TERMINATED;
2096 // If we are not thinking, wait for a condition to be signaled
2097 // instead of wasting CPU time polling for work.
2098 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2099 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2101 assert(!sp || useSleepingThreads);
2102 assert(threadID != 0 || useSleepingThreads);
2104 if (threads[threadID].state == THREAD_INITIALIZING)
2105 threads[threadID].state = THREAD_AVAILABLE;
2107 // Grab the lock to avoid races with wake_sleeping_thread()
2108 lock_grab(&sleepLock[threadID]);
2110 // If we are master and all slaves have finished do not go to sleep
2111 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2112 allFinished = (i == activeThreads);
2114 if (allFinished || allThreadsShouldExit)
2116 lock_release(&sleepLock[threadID]);
2120 // Do sleep here after retesting sleep conditions
2121 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2122 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2124 lock_release(&sleepLock[threadID]);
2127 // If this thread has been assigned work, launch a search
2128 if (threads[threadID].state == THREAD_WORKISWAITING)
2130 assert(!allThreadsShouldExit);
2132 threads[threadID].state = THREAD_SEARCHING;
2134 // Here we call search() with SplitPoint template parameter set to true
2135 SplitPoint* tsp = threads[threadID].splitPoint;
2136 Position pos(*tsp->pos, threadID);
2137 SearchStack* ss = tsp->sstack[threadID] + 1;
2141 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2143 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2145 assert(threads[threadID].state == THREAD_SEARCHING);
2147 threads[threadID].state = THREAD_AVAILABLE;
2149 // Wake up master thread so to allow it to return from the idle loop in
2150 // case we are the last slave of the split point.
2151 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2152 wake_sleeping_thread(tsp->master);
2155 // If this thread is the master of a split point and all slaves have
2156 // finished their work at this split point, return from the idle loop.
2157 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2158 allFinished = (i == activeThreads);
2162 // Because sp->slaves[] is reset under lock protection,
2163 // be sure sp->lock has been released before to return.
2164 lock_grab(&(sp->lock));
2165 lock_release(&(sp->lock));
2167 // In helpful master concept a master can help only a sub-tree, and
2168 // because here is all finished is not possible master is booked.
2169 assert(threads[threadID].state == THREAD_AVAILABLE);
2171 threads[threadID].state = THREAD_SEARCHING;
2178 // init_threads() is called during startup. It launches all helper threads,
2179 // and initializes the split point stack and the global locks and condition
2182 void ThreadsManager::init_threads() {
2184 int i, arg[MAX_THREADS];
2187 // Initialize global locks
2190 for (i = 0; i < MAX_THREADS; i++)
2192 lock_init(&sleepLock[i]);
2193 cond_init(&sleepCond[i]);
2196 // Initialize splitPoints[] locks
2197 for (i = 0; i < MAX_THREADS; i++)
2198 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2199 lock_init(&(threads[i].splitPoints[j].lock));
2201 // Will be set just before program exits to properly end the threads
2202 allThreadsShouldExit = false;
2204 // Threads will be put all threads to sleep as soon as created
2207 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2208 threads[0].state = THREAD_SEARCHING;
2209 for (i = 1; i < MAX_THREADS; i++)
2210 threads[i].state = THREAD_INITIALIZING;
2212 // Launch the helper threads
2213 for (i = 1; i < MAX_THREADS; i++)
2217 #if !defined(_MSC_VER)
2218 pthread_t pthread[1];
2219 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2220 pthread_detach(pthread[0]);
2222 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2226 cout << "Failed to create thread number " << i << endl;
2230 // Wait until the thread has finished launching and is gone to sleep
2231 while (threads[i].state == THREAD_INITIALIZING) {}
2236 // exit_threads() is called when the program exits. It makes all the
2237 // helper threads exit cleanly.
2239 void ThreadsManager::exit_threads() {
2241 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2243 // Wake up all the threads and waits for termination
2244 for (int i = 1; i < MAX_THREADS; i++)
2246 wake_sleeping_thread(i);
2247 while (threads[i].state != THREAD_TERMINATED) {}
2250 // Now we can safely destroy the locks
2251 for (int i = 0; i < MAX_THREADS; i++)
2252 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2253 lock_destroy(&(threads[i].splitPoints[j].lock));
2255 lock_destroy(&mpLock);
2257 // Now we can safely destroy the wait conditions
2258 for (int i = 0; i < MAX_THREADS; i++)
2260 lock_destroy(&sleepLock[i]);
2261 cond_destroy(&sleepCond[i]);
2266 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2267 // the thread's currently active split point, or in some ancestor of
2268 // the current split point.
2270 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2272 assert(threadID >= 0 && threadID < activeThreads);
2274 SplitPoint* sp = threads[threadID].splitPoint;
2276 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2281 // thread_is_available() checks whether the thread with threadID "slave" is
2282 // available to help the thread with threadID "master" at a split point. An
2283 // obvious requirement is that "slave" must be idle. With more than two
2284 // threads, this is not by itself sufficient: If "slave" is the master of
2285 // some active split point, it is only available as a slave to the other
2286 // threads which are busy searching the split point at the top of "slave"'s
2287 // split point stack (the "helpful master concept" in YBWC terminology).
2289 bool ThreadsManager::thread_is_available(int slave, int master) const {
2291 assert(slave >= 0 && slave < activeThreads);
2292 assert(master >= 0 && master < activeThreads);
2293 assert(activeThreads > 1);
2295 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2298 // Make a local copy to be sure doesn't change under our feet
2299 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2301 // No active split points means that the thread is available as
2302 // a slave for any other thread.
2303 if (localActiveSplitPoints == 0 || activeThreads == 2)
2306 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2307 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2308 // could have been set to 0 by another thread leading to an out of bound access.
2309 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2316 // available_thread_exists() tries to find an idle thread which is available as
2317 // a slave for the thread with threadID "master".
2319 bool ThreadsManager::available_thread_exists(int master) const {
2321 assert(master >= 0 && master < activeThreads);
2322 assert(activeThreads > 1);
2324 for (int i = 0; i < activeThreads; i++)
2325 if (thread_is_available(i, master))
2332 // split() does the actual work of distributing the work at a node between
2333 // several available threads. If it does not succeed in splitting the
2334 // node (because no idle threads are available, or because we have no unused
2335 // split point objects), the function immediately returns. If splitting is
2336 // possible, a SplitPoint object is initialized with all the data that must be
2337 // copied to the helper threads and we tell our helper threads that they have
2338 // been assigned work. This will cause them to instantly leave their idle loops and
2339 // call search().When all threads have returned from search() then split() returns.
2341 template <bool Fake>
2342 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2343 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2344 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2345 assert(pos.is_ok());
2346 assert(ply > 0 && ply < PLY_MAX);
2347 assert(*bestValue >= -VALUE_INFINITE);
2348 assert(*bestValue <= *alpha);
2349 assert(*alpha < beta);
2350 assert(beta <= VALUE_INFINITE);
2351 assert(depth > DEPTH_ZERO);
2352 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2353 assert(activeThreads > 1);
2355 int i, master = pos.thread();
2356 Thread& masterThread = threads[master];
2360 // If no other thread is available to help us, or if we have too many
2361 // active split points, don't split.
2362 if ( !available_thread_exists(master)
2363 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2365 lock_release(&mpLock);
2369 // Pick the next available split point object from the split point stack
2370 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2372 // Initialize the split point object
2373 splitPoint.parent = masterThread.splitPoint;
2374 splitPoint.master = master;
2375 splitPoint.betaCutoff = false;
2376 splitPoint.ply = ply;
2377 splitPoint.depth = depth;
2378 splitPoint.threatMove = threatMove;
2379 splitPoint.mateThreat = mateThreat;
2380 splitPoint.alpha = *alpha;
2381 splitPoint.beta = beta;
2382 splitPoint.pvNode = pvNode;
2383 splitPoint.bestValue = *bestValue;
2385 splitPoint.moveCount = moveCount;
2386 splitPoint.pos = &pos;
2387 splitPoint.nodes = 0;
2388 splitPoint.parentSstack = ss;
2389 for (i = 0; i < activeThreads; i++)
2390 splitPoint.slaves[i] = 0;
2392 masterThread.splitPoint = &splitPoint;
2394 // If we are here it means we are not available
2395 assert(masterThread.state != THREAD_AVAILABLE);
2397 int workersCnt = 1; // At least the master is included
2399 // Allocate available threads setting state to THREAD_BOOKED
2400 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2401 if (thread_is_available(i, master))
2403 threads[i].state = THREAD_BOOKED;
2404 threads[i].splitPoint = &splitPoint;
2405 splitPoint.slaves[i] = 1;
2409 assert(Fake || workersCnt > 1);
2411 // We can release the lock because slave threads are already booked and master is not available
2412 lock_release(&mpLock);
2414 // Tell the threads that they have work to do. This will make them leave
2415 // their idle loop. But before copy search stack tail for each thread.
2416 for (i = 0; i < activeThreads; i++)
2417 if (i == master || splitPoint.slaves[i])
2419 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2421 assert(i == master || threads[i].state == THREAD_BOOKED);
2423 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2425 if (useSleepingThreads && i != master)
2426 wake_sleeping_thread(i);
2429 // Everything is set up. The master thread enters the idle loop, from
2430 // which it will instantly launch a search, because its state is
2431 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2432 // idle loop, which means that the main thread will return from the idle
2433 // loop when all threads have finished their work at this split point.
2434 idle_loop(master, &splitPoint);
2436 // We have returned from the idle loop, which means that all threads are
2437 // finished. Update alpha and bestValue, and return.
2440 *alpha = splitPoint.alpha;
2441 *bestValue = splitPoint.bestValue;
2442 masterThread.activeSplitPoints--;
2443 masterThread.splitPoint = splitPoint.parent;
2444 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2446 lock_release(&mpLock);
2450 // wake_sleeping_thread() wakes up the thread with the given threadID
2451 // when it is time to start a new search.
2453 void ThreadsManager::wake_sleeping_thread(int threadID) {
2455 lock_grab(&sleepLock[threadID]);
2456 cond_signal(&sleepCond[threadID]);
2457 lock_release(&sleepLock[threadID]);
2461 /// RootMove and RootMoveList method's definitions
2463 RootMove::RootMove() {
2466 pv_score = non_pv_score = -VALUE_INFINITE;
2470 RootMove& RootMove::operator=(const RootMove& rm) {
2472 const Move* src = rm.pv;
2475 // Avoid a costly full rm.pv[] copy
2476 do *dst++ = *src; while (*src++ != MOVE_NONE);
2479 pv_score = rm.pv_score;
2480 non_pv_score = rm.non_pv_score;
2484 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2485 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2486 // allow to always have a ponder move even when we fail high at root and also a
2487 // long PV to print that is important for position analysis.
2489 void RootMove::extract_pv_from_tt(Position& pos) {
2491 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2495 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2497 pos.do_move(pv[0], *st++);
2499 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2500 && tte->move() != MOVE_NONE
2501 && move_is_legal(pos, tte->move())
2503 && (!pos.is_draw() || ply < 2))
2505 pv[ply] = tte->move();
2506 pos.do_move(pv[ply++], *st++);
2508 pv[ply] = MOVE_NONE;
2510 do pos.undo_move(pv[--ply]); while (ply);
2513 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2514 // the PV back into the TT. This makes sure the old PV moves are searched
2515 // first, even if the old TT entries have been overwritten.
2517 void RootMove::insert_pv_in_tt(Position& pos) {
2519 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2522 Value v, m = VALUE_NONE;
2525 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2529 tte = TT.retrieve(k);
2531 // Don't overwrite exsisting correct entries
2532 if (!tte || tte->move() != pv[ply])
2534 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2535 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2537 pos.do_move(pv[ply], *st++);
2539 } while (pv[++ply] != MOVE_NONE);
2541 do pos.undo_move(pv[--ply]); while (ply);
2544 // pv_info_to_uci() returns a string with information on the current PV line
2545 // formatted according to UCI specification and eventually writes the info
2546 // to a log file. It is called at each iteration or after a new pv is found.
2548 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2550 std::stringstream s, l;
2553 while (*m != MOVE_NONE)
2556 s << "info depth " << depth / ONE_PLY
2557 << " seldepth " << int(m - pv)
2558 << " multipv " << pvLine + 1
2559 << " score " << value_to_uci(pv_score)
2560 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2561 << " time " << current_search_time()
2562 << " nodes " << pos.nodes_searched()
2563 << " nps " << nps(pos)
2564 << " pv " << l.str();
2566 if (UseLogFile && pvLine == 0)
2568 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2569 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2571 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2577 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2579 SearchStack ss[PLY_MAX_PLUS_2];
2580 MoveStack mlist[MOVES_MAX];
2584 // Initialize search stack
2585 init_ss_array(ss, PLY_MAX_PLUS_2);
2586 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2587 bestMoveChanges = 0;
2590 // Generate all legal moves
2591 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2593 // Add each move to the RootMoveList's vector
2594 for (MoveStack* cur = mlist; cur != last; cur++)
2596 // If we have a searchMoves[] list then verify cur->move
2597 // is in the list before to add it.
2598 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2600 if (searchMoves[0] && *sm != cur->move)
2603 // Find a quick score for the move and add to the list
2604 pos.do_move(cur->move, st);
2607 rm.pv[0] = ss[0].currentMove = cur->move;
2608 rm.pv[1] = MOVE_NONE;
2609 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2612 pos.undo_move(cur->move);
2617 // Score root moves using the standard way used in main search, the moves
2618 // are scored according to the order in which are returned by MovePicker.
2619 // This is the second order score that is used to compare the moves when
2620 // the first order pv scores of both moves are equal.
2622 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2625 Value score = VALUE_ZERO;
2626 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2628 while ((move = mp.get_next_move()) != MOVE_NONE)
2629 for (Base::iterator it = begin(); it != end(); ++it)
2630 if (it->pv[0] == move)
2632 it->non_pv_score = score--;