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, int depth, Value alpha, Value beta, int pvLine);
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 sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
150 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], PawnPushTo7thExtension[2], PassedPawnExtension[2];
207 Depth 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 than 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 // Easy move margin. An easy move candidate must be at least this much
237 // better than the second best move.
238 const Value EasyMoveMargin = Value(0x200);
241 /// Namespace variables
252 // Time management variables
253 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
254 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
255 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
260 std::ofstream LogFile;
262 // Multi-threads manager object
263 ThreadsManager ThreadsMgr;
265 // Node counters, used only by thread[0] but try to keep in different cache
266 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
267 bool SendSearchedNodes;
269 int NodesBetweenPolls = 30000;
276 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
278 template <NodeType PvNode, bool SpNode, bool Root>
279 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
281 template <NodeType PvNode>
282 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
284 template <NodeType PvNode>
285 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
287 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
288 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
291 template <NodeType PvNode>
292 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous);
294 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
295 bool connected_moves(const Position& pos, Move m1, Move m2);
296 bool value_is_mate(Value value);
297 Value value_to_tt(Value v, int ply);
298 Value value_from_tt(Value v, int ply);
299 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
300 bool connected_threat(const Position& pos, Move m, Move threat);
301 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
302 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
303 void update_killers(Move m, Move killers[]);
304 void update_gains(const Position& pos, Move move, Value before, Value after);
305 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last);
307 int current_search_time();
308 std::string value_to_uci(Value v);
309 int nps(const Position& pos);
310 void poll(const Position& pos);
311 void wait_for_stop_or_ponderhit();
313 #if !defined(_MSC_VER)
314 void* init_thread(void* threadID);
316 DWORD WINAPI init_thread(LPVOID threadID);
320 // MovePickerExt is an extended MovePicker used to choose at compile time
321 // the proper move source according to the type of node.
322 template<bool SpNode, bool Root> struct MovePickerExt;
324 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
325 // before to search them.
326 template<> struct MovePickerExt<false, true> : public MovePicker {
328 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
329 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
331 Value score = VALUE_ZERO;
333 // Score root moves using the standard way used in main search, the moves
334 // are scored according to the order in which they are returned by MovePicker.
335 // This is the second order score that is used to compare the moves when
336 // the first order pv scores of both moves are equal.
337 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
338 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
339 if (rm->pv[0] == move)
341 rm->non_pv_score = score--;
349 Move get_next_move() {
356 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
359 RootMoveList::iterator rm;
363 // In SpNodes use split point's shared MovePicker object as move source
364 template<> struct MovePickerExt<true, false> : public MovePicker {
366 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
367 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
370 Move get_next_move() { return mp->get_next_move(); }
372 RootMoveList::iterator rm; // Dummy, needed to compile
376 // Default case, create and use a MovePicker object as source
377 template<> struct MovePickerExt<false, false> : public MovePicker {
379 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
380 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
382 RootMoveList::iterator rm; // Dummy, needed to compile
392 /// init_threads(), exit_threads() and nodes_searched() are helpers to
393 /// give accessibility to some TM methods from outside of current file.
395 void init_threads() { ThreadsMgr.init_threads(); }
396 void exit_threads() { ThreadsMgr.exit_threads(); }
399 /// init_search() is called during startup. It initializes various lookup tables
403 int d; // depth (ONE_PLY == 2)
404 int hd; // half depth (ONE_PLY == 1)
407 // Init reductions array
408 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
410 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
411 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
412 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
413 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
416 // Init futility margins array
417 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
418 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
420 // Init futility move count array
421 for (d = 0; d < 32; d++)
422 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
426 /// perft() is our utility to verify move generation is bug free. All the legal
427 /// moves up to given depth are generated and counted and the sum returned.
429 int64_t perft(Position& pos, Depth depth)
431 MoveStack mlist[MOVES_MAX];
436 // Generate all legal moves
437 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
439 // If we are at the last ply we don't need to do and undo
440 // the moves, just to count them.
441 if (depth <= ONE_PLY)
442 return int(last - mlist);
444 // Loop through all legal moves
446 for (MoveStack* cur = mlist; cur != last; cur++)
449 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
450 sum += perft(pos, depth - ONE_PLY);
457 /// think() is the external interface to Stockfish's search, and is called when
458 /// the program receives the UCI 'go' command. It initializes various
459 /// search-related global variables, and calls id_loop(). It returns false
460 /// when a quit command is received during the search.
462 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
463 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
465 // Initialize global search variables
466 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
468 SearchStartTime = get_system_time();
469 ExactMaxTime = maxTime;
472 InfiniteSearch = infinite;
474 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
476 // Look for a book move, only during games, not tests
477 if (UseTimeManagement && Options["OwnBook"].value<bool>())
479 if (Options["Book File"].value<std::string>() != OpeningBook.name())
480 OpeningBook.open(Options["Book File"].value<std::string>());
482 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
483 if (bookMove != MOVE_NONE)
486 wait_for_stop_or_ponderhit();
488 cout << "bestmove " << bookMove << endl;
493 // Read UCI option values
494 TT.set_size(Options["Hash"].value<int>());
495 if (Options["Clear Hash"].value<bool>())
497 Options["Clear Hash"].set_value("false");
501 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
502 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
503 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
504 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
505 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
506 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
507 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
508 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
509 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
510 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
511 MultiPV = Options["MultiPV"].value<int>();
512 UseLogFile = Options["Use Search Log"].value<bool>();
514 read_evaluation_uci_options(pos.side_to_move());
516 // Set the number of active threads
517 ThreadsMgr.read_uci_options();
518 init_eval(ThreadsMgr.active_threads());
520 // Wake up needed threads
521 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
522 ThreadsMgr.wake_sleeping_thread(i);
525 int myTime = time[pos.side_to_move()];
526 int myIncrement = increment[pos.side_to_move()];
527 if (UseTimeManagement)
528 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
530 // Set best NodesBetweenPolls interval to avoid lagging under
531 // heavy time pressure.
533 NodesBetweenPolls = Min(MaxNodes, 30000);
534 else if (myTime && myTime < 1000)
535 NodesBetweenPolls = 1000;
536 else if (myTime && myTime < 5000)
537 NodesBetweenPolls = 5000;
539 NodesBetweenPolls = 30000;
541 // Write search information to log file
544 std::string name = Options["Search Log Filename"].value<std::string>();
545 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
547 LogFile << "\nSearching: " << pos.to_fen()
548 << "\ninfinite: " << infinite
549 << " ponder: " << ponder
550 << " time: " << myTime
551 << " increment: " << myIncrement
552 << " moves to go: " << movesToGo
556 // We're ready to start thinking. Call the iterative deepening loop function
557 Move ponderMove = MOVE_NONE;
558 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
560 // Print final search statistics
561 cout << "info nodes " << pos.nodes_searched()
562 << " nps " << nps(pos)
563 << " time " << current_search_time() << endl;
567 LogFile << "Nodes: " << pos.nodes_searched()
568 << "\nNodes/second: " << nps(pos)
569 << "\nBest move: " << move_to_san(pos, bestMove);
572 pos.do_move(bestMove, st);
573 LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
574 pos.undo_move(bestMove); // Return from think() with unchanged position
578 // This makes all the threads to go to sleep
579 ThreadsMgr.set_active_threads(1);
581 // If we are pondering or in infinite search, we shouldn't print the
582 // best move before we are told to do so.
583 if (!StopRequest && (Pondering || InfiniteSearch))
584 wait_for_stop_or_ponderhit();
586 // Could be both MOVE_NONE when searching on a stalemate position
587 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
595 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
596 // with increasing depth until the allocated thinking time has been consumed,
597 // user stops the search, or the maximum search depth is reached.
599 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
601 SearchStack ss[PLY_MAX_PLUS_2];
602 Value bestValues[PLY_MAX_PLUS_2];
603 int bestMoveChanges[PLY_MAX_PLUS_2];
604 int depth, researchCountFL, researchCountFH, aspirationDelta;
605 Value value, alpha, beta;
606 Move bestMove, easyMove;
608 // Moves to search are verified, scored and sorted
609 Rml.init(pos, searchMoves);
611 // Initialize FIXME move before Rml.init()
614 memset(ss, 0, 4 * sizeof(SearchStack));
615 *ponderMove = bestMove = easyMove = MOVE_NONE;
616 depth = aspirationDelta = 0;
617 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
618 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
620 // Handle special case of searching on a mate/stalemate position
623 cout << "info depth 0 score "
624 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
630 // Is one move significantly better than others after initial scoring ?
632 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
633 easyMove = Rml[0].pv[0];
635 // Iterative deepening loop
636 while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
638 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
639 cout << "info depth " << depth << endl;
641 // Calculate dynamic aspiration window based on previous iterations
642 if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
644 int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
645 int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
647 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
648 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
650 alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
651 beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
654 // Start with a small aspiration window and, in case of fail high/low,
655 // research with bigger window until not failing high/low anymore.
658 // Search starting from ss+1 to allow calling update_gains()
659 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth * ONE_PLY, 0);
661 // Send PV line to GUI and write to transposition table in case the
662 // relevant entries have been overwritten during the search.
663 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
665 Rml[i].insert_pv_in_tt(pos);
666 cout << set960(pos.is_chess960())
667 << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
670 // Value cannot be trusted. Break out immediately!
674 assert(value >= alpha);
676 // In case of failing high/low increase aspiration window and research,
677 // otherwise exit the fail high/low loop.
680 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
683 else if (value <= alpha)
685 AspirationFailLow = true;
686 StopOnPonderhit = false;
688 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
695 // Collect info about search result
696 bestMove = Rml[0].pv[0];
697 bestValues[depth] = value;
698 bestMoveChanges[depth] = Rml.bestMoveChanges;
701 LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
703 // Drop the easy move if differs from the new best move
704 if (bestMove != easyMove)
705 easyMove = MOVE_NONE;
707 if (UseTimeManagement && !StopRequest)
710 bool noMoreTime = false;
712 // Stop search early when the last two iterations returned a mate score
714 && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100
715 && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100)
718 // Stop search early if one move seems to be much better than the
719 // others or if there is only a single legal move. In this latter
720 // case we search up to Iteration 8 anyway to get a proper score.
722 && easyMove == bestMove
724 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
725 && current_search_time() > TimeMgr.available_time() / 16)
726 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
727 && current_search_time() > TimeMgr.available_time() / 32)))
730 // Add some extra time if the best move has changed during the last two iterations
731 if (depth > 4 && depth < 50)
732 TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]);
734 // Stop search if most of MaxSearchTime is consumed at the end of the
735 // iteration. We probably don't have enough time to search the first
736 // move at the next iteration anyway.
737 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
743 StopOnPonderhit = true;
750 *ponderMove = Rml[0].pv[1];
755 // search<>() is the main search function for both PV and non-PV nodes and for
756 // normal and SplitPoint nodes. When called just after a split point the search
757 // is simpler because we have already probed the hash table, done a null move
758 // search, and searched the first move before splitting, we don't have to repeat
759 // all this work again. We also don't need to store anything to the hash table
760 // here: This is taken care of after we return from the split point.
762 template <NodeType PvNode, bool SpNode, bool Root>
763 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
765 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
766 assert(beta > alpha && beta <= VALUE_INFINITE);
767 assert(PvNode || alpha == beta - 1);
768 assert((Root || ply > 0) && ply < PLY_MAX);
769 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
771 Move movesSearched[MOVES_MAX];
776 Move ttMove, move, excludedMove, threatMove;
779 Value bestValue, value, oldAlpha;
780 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
781 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
782 bool mateThreat = false;
783 int moveCount = 0, playedMoveCount = 0;
784 int threadID = pos.thread();
785 SplitPoint* sp = NULL;
787 refinedValue = bestValue = value = -VALUE_INFINITE;
789 isCheck = pos.is_check();
795 ttMove = excludedMove = MOVE_NONE;
796 threatMove = sp->threatMove;
797 mateThreat = sp->mateThreat;
798 goto split_point_start;
803 // Step 1. Initialize node and poll. Polling can abort search
804 ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
805 (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
806 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
808 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
814 // Step 2. Check for aborted search and immediate draw
816 || ThreadsMgr.cutoff_at_splitpoint(threadID)
818 || ply >= PLY_MAX - 1) && !Root)
821 // Step 3. Mate distance pruning
822 alpha = Max(value_mated_in(ply), alpha);
823 beta = Min(value_mate_in(ply+1), beta);
827 // Step 4. Transposition table lookup
828 // We don't want the score of a partial search to overwrite a previous full search
829 // TT value, so we use a different position key in case of an excluded move.
830 excludedMove = ss->excludedMove;
831 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
833 tte = TT.retrieve(posKey);
834 ttMove = tte ? tte->move() : MOVE_NONE;
836 // At PV nodes we check for exact scores, while at non-PV nodes we check for
837 // and return a fail high/low. Biggest advantage at probing at PV nodes is
838 // to have a smooth experience in analysis mode.
841 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
842 : ok_to_use_TT(tte, depth, beta, ply)))
845 ss->bestMove = ttMove; // Can be MOVE_NONE
846 return value_from_tt(tte->value(), ply);
849 // Step 5. Evaluate the position statically and
850 // update gain statistics of parent move.
852 ss->eval = ss->evalMargin = VALUE_NONE;
855 assert(tte->static_value() != VALUE_NONE);
857 ss->eval = tte->static_value();
858 ss->evalMargin = tte->static_value_margin();
859 refinedValue = refine_eval(tte, ss->eval, ply);
863 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
864 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
867 // Save gain for the parent non-capture move
868 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
870 // Step 6. Razoring (is omitted in PV nodes)
872 && depth < RazorDepth
874 && refinedValue < beta - razor_margin(depth)
875 && ttMove == MOVE_NONE
876 && !value_is_mate(beta)
877 && !pos.has_pawn_on_7th(pos.side_to_move()))
879 Value rbeta = beta - razor_margin(depth);
880 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
882 // Logically we should return (v + razor_margin(depth)), but
883 // surprisingly this did slightly weaker in tests.
887 // Step 7. Static null move pruning (is omitted in PV nodes)
888 // We're betting that the opponent doesn't have a move that will reduce
889 // the score by more than futility_margin(depth) if we do a null move.
892 && depth < RazorDepth
894 && refinedValue >= beta + futility_margin(depth, 0)
895 && !value_is_mate(beta)
896 && pos.non_pawn_material(pos.side_to_move()))
897 return refinedValue - futility_margin(depth, 0);
899 // Step 8. Null move search with verification search (is omitted in PV nodes)
904 && refinedValue >= beta
905 && !value_is_mate(beta)
906 && pos.non_pawn_material(pos.side_to_move()))
908 ss->currentMove = MOVE_NULL;
910 // Null move dynamic reduction based on depth
911 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
913 // Null move dynamic reduction based on value
914 if (refinedValue - beta > PawnValueMidgame)
917 pos.do_null_move(st);
918 (ss+1)->skipNullMove = true;
919 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
920 (ss+1)->skipNullMove = false;
921 pos.undo_null_move();
923 if (nullValue >= beta)
925 // Do not return unproven mate scores
926 if (nullValue >= value_mate_in(PLY_MAX))
929 if (depth < 6 * ONE_PLY)
932 // Do verification search at high depths
933 ss->skipNullMove = true;
934 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
935 ss->skipNullMove = false;
942 // The null move failed low, which means that we may be faced with
943 // some kind of threat. If the previous move was reduced, check if
944 // the move that refuted the null move was somehow connected to the
945 // move which was reduced. If a connection is found, return a fail
946 // low score (which will cause the reduced move to fail high in the
947 // parent node, which will trigger a re-search with full depth).
948 if (nullValue == value_mated_in(ply + 2))
951 threatMove = (ss+1)->bestMove;
952 if ( depth < ThreatDepth
954 && threatMove != MOVE_NONE
955 && connected_moves(pos, (ss-1)->currentMove, threatMove))
960 // Step 9. Internal iterative deepening
961 if ( depth >= IIDDepth[PvNode]
962 && ttMove == MOVE_NONE
963 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
965 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
967 ss->skipNullMove = true;
968 search<PvNode>(pos, ss, alpha, beta, d, ply);
969 ss->skipNullMove = false;
971 ttMove = ss->bestMove;
972 tte = TT.retrieve(posKey);
975 // Expensive mate threat detection (only for PV nodes)
977 mateThreat = pos.has_mate_threat();
979 split_point_start: // At split points actual search starts from here
981 // Initialize a MovePicker object for the current position
982 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
984 ss->bestMove = MOVE_NONE;
985 futilityBase = ss->eval + ss->evalMargin;
986 singularExtensionNode = !Root
988 && depth >= SingularExtensionDepth[PvNode]
991 && !excludedMove // Do not allow recursive singular extension search
992 && (tte->type() & VALUE_TYPE_LOWER)
993 && tte->depth() >= depth - 3 * ONE_PLY;
996 lock_grab(&(sp->lock));
997 bestValue = sp->bestValue;
1000 // Step 10. Loop through moves
1001 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1002 while ( bestValue < beta
1003 && (move = mp.get_next_move()) != MOVE_NONE
1004 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1006 assert(move_is_ok(move));
1010 moveCount = ++sp->moveCount;
1011 lock_release(&(sp->lock));
1013 else if (move == excludedMove)
1020 // This is used by time management
1021 FirstRootMove = (moveCount == 1);
1023 // Save the current node count before the move is searched
1024 nodes = pos.nodes_searched();
1026 // If it's time to send nodes info, do it here where we have the
1027 // correct accumulated node counts searched by each thread.
1028 if (SendSearchedNodes)
1030 SendSearchedNodes = false;
1031 cout << "info nodes " << nodes
1032 << " nps " << nps(pos)
1033 << " time " << current_search_time() << endl;
1036 if (current_search_time() >= 1000)
1037 cout << "info currmove " << move
1038 << " currmovenumber " << moveCount << endl;
1041 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1042 moveIsCheck = pos.move_is_check(move, ci);
1043 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1045 // Step 11. Decide the new search depth
1046 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1048 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1049 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1050 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1051 // lower than ttValue minus a margin then we extend ttMove.
1052 if ( singularExtensionNode
1053 && move == tte->move()
1056 Value ttValue = value_from_tt(tte->value(), ply);
1058 if (abs(ttValue) < VALUE_KNOWN_WIN)
1060 Value b = ttValue - SingularExtensionMargin;
1061 ss->excludedMove = move;
1062 ss->skipNullMove = true;
1063 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1064 ss->skipNullMove = false;
1065 ss->excludedMove = MOVE_NONE;
1066 ss->bestMove = MOVE_NONE;
1072 // Update current move (this must be done after singular extension search)
1073 ss->currentMove = move;
1074 newDepth = depth - ONE_PLY + ext;
1076 // Step 12. Futility pruning (is omitted in PV nodes)
1078 && !captureOrPromotion
1082 && !move_is_castle(move))
1084 // Move count based pruning
1085 if ( moveCount >= futility_move_count(depth)
1086 && !(threatMove && connected_threat(pos, move, threatMove))
1087 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1090 lock_grab(&(sp->lock));
1095 // Value based pruning
1096 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1097 // but fixing this made program slightly weaker.
1098 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1099 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1100 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1102 if (futilityValueScaled < beta)
1106 lock_grab(&(sp->lock));
1107 if (futilityValueScaled > sp->bestValue)
1108 sp->bestValue = bestValue = futilityValueScaled;
1110 else if (futilityValueScaled > bestValue)
1111 bestValue = futilityValueScaled;
1116 // Prune moves with negative SEE at low depths
1117 if ( predictedDepth < 2 * ONE_PLY
1118 && bestValue > value_mated_in(PLY_MAX)
1119 && pos.see_sign(move) < 0)
1122 lock_grab(&(sp->lock));
1128 // Step 13. Make the move
1129 pos.do_move(move, st, ci, moveIsCheck);
1131 if (!SpNode && !captureOrPromotion)
1132 movesSearched[playedMoveCount++] = move;
1134 // Step extra. pv search (only in PV nodes)
1135 // The first move in list is the expected PV
1138 // Aspiration window is disabled in multi-pv case
1139 if (Root && MultiPV > 1)
1140 alpha = -VALUE_INFINITE;
1142 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1146 // Step 14. Reduced depth search
1147 // If the move fails high will be re-searched at full depth.
1148 bool doFullDepthSearch = true;
1150 if ( depth >= 3 * ONE_PLY
1151 && !captureOrPromotion
1153 && !move_is_castle(move)
1154 && ss->killers[0] != move
1155 && ss->killers[1] != move)
1157 ss->reduction = reduction<PvNode>(depth, moveCount);
1160 alpha = SpNode ? sp->alpha : alpha;
1161 Depth d = newDepth - ss->reduction;
1162 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1164 doFullDepthSearch = (value > alpha);
1166 ss->reduction = DEPTH_ZERO; // Restore original reduction
1169 // Step 15. Full depth search
1170 if (doFullDepthSearch)
1172 alpha = SpNode ? sp->alpha : alpha;
1173 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1175 // Step extra. pv search (only in PV nodes)
1176 // Search only for possible new PV nodes, if instead value >= beta then
1177 // parent node fails low with value <= alpha and tries another move.
1178 if (PvNode && value > alpha && (Root || value < beta))
1179 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1183 // Step 16. Undo move
1184 pos.undo_move(move);
1186 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1188 // Step 17. Check for new best move
1191 lock_grab(&(sp->lock));
1192 bestValue = sp->bestValue;
1196 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1201 sp->bestValue = value;
1203 if (!Root && value > alpha)
1205 if (PvNode && value < beta) // We want always alpha < beta
1213 sp->betaCutoff = true;
1215 if (value == value_mate_in(ply + 1))
1216 ss->mateKiller = move;
1218 ss->bestMove = move;
1221 sp->ss->bestMove = move;
1227 // Finished searching the move. If StopRequest is true, the search
1228 // was aborted because the user interrupted the search or because we
1229 // ran out of time. In this case, the return value of the search cannot
1230 // be trusted, and we break out of the loop without updating the best
1235 // Remember searched nodes counts for this move
1236 mp.rm->nodes += pos.nodes_searched() - nodes;
1238 // PV move or new best move ?
1239 if (isPvMove || value > alpha)
1242 ss->bestMove = move;
1243 mp.rm->pv_score = value;
1244 mp.rm->extract_pv_from_tt(pos);
1246 // We record how often the best move has been changed in each
1247 // iteration. This information is used for time management: When
1248 // the best move changes frequently, we allocate some more time.
1249 if (!isPvMove && MultiPV == 1)
1250 Rml.bestMoveChanges++;
1252 Rml.sort_multipv(moveCount);
1254 // Update alpha. In multi-pv we don't use aspiration window, so
1255 // set alpha equal to minimum score among the PV lines.
1257 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1258 else if (value > alpha)
1262 mp.rm->pv_score = -VALUE_INFINITE;
1266 // Step 18. Check for split
1269 && depth >= ThreadsMgr.min_split_depth()
1270 && ThreadsMgr.active_threads() > 1
1272 && ThreadsMgr.available_thread_exists(threadID)
1274 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1275 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1276 threatMove, mateThreat, moveCount, &mp, PvNode);
1279 // Step 19. Check for mate and stalemate
1280 // All legal moves have been searched and if there are
1281 // no legal moves, it must be mate or stalemate.
1282 // If one move was excluded return fail low score.
1283 if (!SpNode && !moveCount)
1284 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1286 // Step 20. Update tables
1287 // If the search is not aborted, update the transposition table,
1288 // history counters, and killer moves.
1289 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1291 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1292 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1293 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1295 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1297 // Update killers and history only for non capture moves that fails high
1298 if ( bestValue >= beta
1299 && !pos.move_is_capture_or_promotion(move))
1301 update_history(pos, move, depth, movesSearched, playedMoveCount);
1302 update_killers(move, ss->killers);
1308 // Here we have the lock still grabbed
1309 sp->slaves[threadID] = 0;
1310 sp->nodes += pos.nodes_searched();
1311 lock_release(&(sp->lock));
1314 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1319 // qsearch() is the quiescence search function, which is called by the main
1320 // search function when the remaining depth is zero (or, to be more precise,
1321 // less than ONE_PLY).
1323 template <NodeType PvNode>
1324 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1326 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1327 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1328 assert(PvNode || alpha == beta - 1);
1330 assert(ply > 0 && ply < PLY_MAX);
1331 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1335 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1336 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1339 Value oldAlpha = alpha;
1341 ss->bestMove = ss->currentMove = MOVE_NONE;
1343 // Check for an instant draw or maximum ply reached
1344 if (pos.is_draw() || ply >= PLY_MAX - 1)
1347 // Decide whether or not to include checks, this fixes also the type of
1348 // TT entry depth that we are going to use. Note that in qsearch we use
1349 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1350 isCheck = pos.is_check();
1351 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1353 // Transposition table lookup. At PV nodes, we don't use the TT for
1354 // pruning, but only for move ordering.
1355 tte = TT.retrieve(pos.get_key());
1356 ttMove = (tte ? tte->move() : MOVE_NONE);
1358 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1360 ss->bestMove = ttMove; // Can be MOVE_NONE
1361 return value_from_tt(tte->value(), ply);
1364 // Evaluate the position statically
1367 bestValue = futilityBase = -VALUE_INFINITE;
1368 ss->eval = evalMargin = VALUE_NONE;
1369 enoughMaterial = false;
1375 assert(tte->static_value() != VALUE_NONE);
1377 evalMargin = tte->static_value_margin();
1378 ss->eval = bestValue = tte->static_value();
1381 ss->eval = bestValue = evaluate(pos, evalMargin);
1383 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1385 // Stand pat. Return immediately if static value is at least beta
1386 if (bestValue >= beta)
1389 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1394 if (PvNode && bestValue > alpha)
1397 // Futility pruning parameters, not needed when in check
1398 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1399 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1402 // Initialize a MovePicker object for the current position, and prepare
1403 // to search the moves. Because the depth is <= 0 here, only captures,
1404 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1406 MovePicker mp(pos, ttMove, depth, H);
1409 // Loop through the moves until no moves remain or a beta cutoff occurs
1410 while ( alpha < beta
1411 && (move = mp.get_next_move()) != MOVE_NONE)
1413 assert(move_is_ok(move));
1415 moveIsCheck = pos.move_is_check(move, ci);
1423 && !move_is_promotion(move)
1424 && !pos.move_is_passed_pawn_push(move))
1426 futilityValue = futilityBase
1427 + pos.endgame_value_of_piece_on(move_to(move))
1428 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1430 if (futilityValue < alpha)
1432 if (futilityValue > bestValue)
1433 bestValue = futilityValue;
1438 // Detect non-capture evasions that are candidate to be pruned
1439 evasionPrunable = isCheck
1440 && bestValue > value_mated_in(PLY_MAX)
1441 && !pos.move_is_capture(move)
1442 && !pos.can_castle(pos.side_to_move());
1444 // Don't search moves with negative SEE values
1446 && (!isCheck || evasionPrunable)
1448 && !move_is_promotion(move)
1449 && pos.see_sign(move) < 0)
1452 // Don't search useless checks
1457 && !pos.move_is_capture_or_promotion(move)
1458 && ss->eval + PawnValueMidgame / 4 < beta
1459 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1461 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1462 bestValue = ss->eval + PawnValueMidgame / 4;
1467 // Update current move
1468 ss->currentMove = move;
1470 // Make and search the move
1471 pos.do_move(move, st, ci, moveIsCheck);
1472 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1473 pos.undo_move(move);
1475 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1478 if (value > bestValue)
1484 ss->bestMove = move;
1489 // All legal moves have been searched. A special case: If we're in check
1490 // and no legal moves were found, it is checkmate.
1491 if (isCheck && bestValue == -VALUE_INFINITE)
1492 return value_mated_in(ply);
1494 // Update transposition table
1495 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1496 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1498 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1504 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1505 // it is used in RootMoveList to get an initial scoring.
1506 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1508 SearchStack ss[PLY_MAX_PLUS_2];
1511 memset(ss, 0, 4 * sizeof(SearchStack));
1512 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1514 for (MoveStack* cur = mlist; cur != last; cur++)
1516 ss[0].currentMove = cur->move;
1517 pos.do_move(cur->move, st);
1518 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1519 pos.undo_move(cur->move);
1524 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1525 // bestValue is updated only when returning false because in that case move
1528 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1530 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1531 Square from, to, ksq, victimSq;
1534 Value futilityValue, bv = *bestValue;
1536 from = move_from(move);
1538 them = opposite_color(pos.side_to_move());
1539 ksq = pos.king_square(them);
1540 kingAtt = pos.attacks_from<KING>(ksq);
1541 pc = pos.piece_on(from);
1543 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1544 oldAtt = pos.attacks_from(pc, from, occ);
1545 newAtt = pos.attacks_from(pc, to, occ);
1547 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1548 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1550 if (!(b && (b & (b - 1))))
1553 // Rule 2. Queen contact check is very dangerous
1554 if ( type_of_piece(pc) == QUEEN
1555 && bit_is_set(kingAtt, to))
1558 // Rule 3. Creating new double threats with checks
1559 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1563 victimSq = pop_1st_bit(&b);
1564 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1566 // Note that here we generate illegal "double move"!
1567 if ( futilityValue >= beta
1568 && pos.see_sign(make_move(from, victimSq)) >= 0)
1571 if (futilityValue > bv)
1575 // Update bestValue only if check is not dangerous (because we will prune the move)
1581 // connected_moves() tests whether two moves are 'connected' in the sense
1582 // that the first move somehow made the second move possible (for instance
1583 // if the moving piece is the same in both moves). The first move is assumed
1584 // to be the move that was made to reach the current position, while the
1585 // second move is assumed to be a move from the current position.
1587 bool connected_moves(const Position& pos, Move m1, Move m2) {
1589 Square f1, t1, f2, t2;
1592 assert(m1 && move_is_ok(m1));
1593 assert(m2 && move_is_ok(m2));
1595 // Case 1: The moving piece is the same in both moves
1601 // Case 2: The destination square for m2 was vacated by m1
1607 // Case 3: Moving through the vacated square
1608 if ( piece_is_slider(pos.piece_on(f2))
1609 && bit_is_set(squares_between(f2, t2), f1))
1612 // Case 4: The destination square for m2 is defended by the moving piece in m1
1613 p = pos.piece_on(t1);
1614 if (bit_is_set(pos.attacks_from(p, t1), t2))
1617 // Case 5: Discovered check, checking piece is the piece moved in m1
1618 if ( piece_is_slider(p)
1619 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1620 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1622 // discovered_check_candidates() works also if the Position's side to
1623 // move is the opposite of the checking piece.
1624 Color them = opposite_color(pos.side_to_move());
1625 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1627 if (bit_is_set(dcCandidates, f2))
1634 // value_is_mate() checks if the given value is a mate one eventually
1635 // compensated for the ply.
1637 bool value_is_mate(Value value) {
1639 assert(abs(value) <= VALUE_INFINITE);
1641 return value <= value_mated_in(PLY_MAX)
1642 || value >= value_mate_in(PLY_MAX);
1646 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1647 // "plies to mate from the current ply". Non-mate scores are unchanged.
1648 // The function is called before storing a value to the transposition table.
1650 Value value_to_tt(Value v, int ply) {
1652 if (v >= value_mate_in(PLY_MAX))
1655 if (v <= value_mated_in(PLY_MAX))
1662 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1663 // the transposition table to a mate score corrected for the current ply.
1665 Value value_from_tt(Value v, int ply) {
1667 if (v >= value_mate_in(PLY_MAX))
1670 if (v <= value_mated_in(PLY_MAX))
1677 // extension() decides whether a move should be searched with normal depth,
1678 // or with extended depth. Certain classes of moves (checking moves, in
1679 // particular) are searched with bigger depth than ordinary moves and in
1680 // any case are marked as 'dangerous'. Note that also if a move is not
1681 // extended, as example because the corresponding UCI option is set to zero,
1682 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1683 template <NodeType PvNode>
1684 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1685 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1687 assert(m != MOVE_NONE);
1689 Depth result = DEPTH_ZERO;
1690 *dangerous = moveIsCheck | mateThreat;
1694 if (moveIsCheck && pos.see_sign(m) >= 0)
1695 result += CheckExtension[PvNode];
1698 result += MateThreatExtension[PvNode];
1701 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1703 Color c = pos.side_to_move();
1704 if (relative_rank(c, move_to(m)) == RANK_7)
1706 result += PawnPushTo7thExtension[PvNode];
1709 if (pos.pawn_is_passed(c, move_to(m)))
1711 result += PassedPawnExtension[PvNode];
1716 if ( captureOrPromotion
1717 && pos.type_of_piece_on(move_to(m)) != PAWN
1718 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1719 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1720 && !move_is_promotion(m)
1723 result += PawnEndgameExtension[PvNode];
1728 && captureOrPromotion
1729 && pos.type_of_piece_on(move_to(m)) != PAWN
1730 && pos.see_sign(m) >= 0)
1732 result += ONE_PLY / 2;
1736 return Min(result, ONE_PLY);
1740 // connected_threat() tests whether it is safe to forward prune a move or if
1741 // is somehow connected to the threat move returned by null search.
1743 bool connected_threat(const Position& pos, Move m, Move threat) {
1745 assert(move_is_ok(m));
1746 assert(threat && move_is_ok(threat));
1747 assert(!pos.move_is_check(m));
1748 assert(!pos.move_is_capture_or_promotion(m));
1749 assert(!pos.move_is_passed_pawn_push(m));
1751 Square mfrom, mto, tfrom, tto;
1753 mfrom = move_from(m);
1755 tfrom = move_from(threat);
1756 tto = move_to(threat);
1758 // Case 1: Don't prune moves which move the threatened piece
1762 // Case 2: If the threatened piece has value less than or equal to the
1763 // value of the threatening piece, don't prune moves which defend it.
1764 if ( pos.move_is_capture(threat)
1765 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1766 || pos.type_of_piece_on(tfrom) == KING)
1767 && pos.move_attacks_square(m, tto))
1770 // Case 3: If the moving piece in the threatened move is a slider, don't
1771 // prune safe moves which block its ray.
1772 if ( piece_is_slider(pos.piece_on(tfrom))
1773 && bit_is_set(squares_between(tfrom, tto), mto)
1774 && pos.see_sign(m) >= 0)
1781 // ok_to_use_TT() returns true if a transposition table score
1782 // can be used at a given point in search.
1784 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1786 Value v = value_from_tt(tte->value(), ply);
1788 return ( tte->depth() >= depth
1789 || v >= Max(value_mate_in(PLY_MAX), beta)
1790 || v < Min(value_mated_in(PLY_MAX), beta))
1792 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1793 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1797 // refine_eval() returns the transposition table score if
1798 // possible otherwise falls back on static position evaluation.
1800 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1804 Value v = value_from_tt(tte->value(), ply);
1806 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1807 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1814 // update_history() registers a good move that produced a beta-cutoff
1815 // in history and marks as failures all the other moves of that ply.
1817 void update_history(const Position& pos, Move move, Depth depth,
1818 Move movesSearched[], int moveCount) {
1820 Value bonus = Value(int(depth) * int(depth));
1822 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1824 for (int i = 0; i < moveCount - 1; i++)
1826 m = movesSearched[i];
1830 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1835 // update_killers() add a good move that produced a beta-cutoff
1836 // among the killer moves of that ply.
1838 void update_killers(Move m, Move killers[]) {
1840 if (m != killers[0])
1842 killers[1] = killers[0];
1848 // update_gains() updates the gains table of a non-capture move given
1849 // the static position evaluation before and after the move.
1851 void update_gains(const Position& pos, Move m, Value before, Value after) {
1854 && before != VALUE_NONE
1855 && after != VALUE_NONE
1856 && pos.captured_piece_type() == PIECE_TYPE_NONE
1857 && !move_is_special(m))
1858 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1862 // value_to_uci() converts a value to a string suitable for use with the UCI
1863 // protocol specifications:
1865 // cp <x> The score from the engine's point of view in centipawns.
1866 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1867 // use negative values for y.
1869 std::string value_to_uci(Value v) {
1871 std::stringstream s;
1873 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1874 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1876 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
1882 // current_search_time() returns the number of milliseconds which have passed
1883 // since the beginning of the current search.
1885 int current_search_time() {
1887 return get_system_time() - SearchStartTime;
1891 // nps() computes the current nodes/second count
1893 int nps(const Position& pos) {
1895 int t = current_search_time();
1896 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1900 // poll() performs two different functions: It polls for user input, and it
1901 // looks at the time consumed so far and decides if it's time to abort the
1904 void poll(const Position& pos) {
1906 static int lastInfoTime;
1907 int t = current_search_time();
1910 if (input_available())
1912 // We are line oriented, don't read single chars
1913 std::string command;
1915 if (!std::getline(std::cin, command))
1918 if (command == "quit")
1920 // Quit the program as soon as possible
1922 QuitRequest = StopRequest = true;
1925 else if (command == "stop")
1927 // Stop calculating as soon as possible, but still send the "bestmove"
1928 // and possibly the "ponder" token when finishing the search.
1932 else if (command == "ponderhit")
1934 // The opponent has played the expected move. GUI sends "ponderhit" if
1935 // we were told to ponder on the same move the opponent has played. We
1936 // should continue searching but switching from pondering to normal search.
1939 if (StopOnPonderhit)
1944 // Print search information
1948 else if (lastInfoTime > t)
1949 // HACK: Must be a new search where we searched less than
1950 // NodesBetweenPolls nodes during the first second of search.
1953 else if (t - lastInfoTime >= 1000)
1960 if (dbg_show_hit_rate)
1961 dbg_print_hit_rate();
1963 // Send info on searched nodes as soon as we return to root
1964 SendSearchedNodes = true;
1967 // Should we stop the search?
1971 bool stillAtFirstMove = FirstRootMove
1972 && !AspirationFailLow
1973 && t > TimeMgr.available_time();
1975 bool noMoreTime = t > TimeMgr.maximum_time()
1976 || stillAtFirstMove;
1978 if ( (UseTimeManagement && noMoreTime)
1979 || (ExactMaxTime && t >= ExactMaxTime)
1980 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1985 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1986 // while the program is pondering. The point is to work around a wrinkle in
1987 // the UCI protocol: When pondering, the engine is not allowed to give a
1988 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1989 // We simply wait here until one of these commands is sent, and return,
1990 // after which the bestmove and pondermove will be printed.
1992 void wait_for_stop_or_ponderhit() {
1994 std::string command;
1998 // Wait for a command from stdin
1999 if (!std::getline(std::cin, command))
2002 if (command == "quit")
2007 else if (command == "ponderhit" || command == "stop")
2013 // init_thread() is the function which is called when a new thread is
2014 // launched. It simply calls the idle_loop() function with the supplied
2015 // threadID. There are two versions of this function; one for POSIX
2016 // threads and one for Windows threads.
2018 #if !defined(_MSC_VER)
2020 void* init_thread(void* threadID) {
2022 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2028 DWORD WINAPI init_thread(LPVOID threadID) {
2030 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2037 /// The ThreadsManager class
2040 // read_uci_options() updates number of active threads and other internal
2041 // parameters according to the UCI options values. It is called before
2042 // to start a new search.
2044 void ThreadsManager::read_uci_options() {
2046 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2047 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2048 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2049 activeThreads = Options["Threads"].value<int>();
2053 // idle_loop() is where the threads are parked when they have no work to do.
2054 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2055 // object for which the current thread is the master.
2057 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2059 assert(threadID >= 0 && threadID < MAX_THREADS);
2062 bool allFinished = false;
2066 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2067 // master should exit as last one.
2068 if (allThreadsShouldExit)
2071 threads[threadID].state = THREAD_TERMINATED;
2075 // If we are not thinking, wait for a condition to be signaled
2076 // instead of wasting CPU time polling for work.
2077 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2078 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2080 assert(!sp || useSleepingThreads);
2081 assert(threadID != 0 || useSleepingThreads);
2083 if (threads[threadID].state == THREAD_INITIALIZING)
2084 threads[threadID].state = THREAD_AVAILABLE;
2086 // Grab the lock to avoid races with wake_sleeping_thread()
2087 lock_grab(&sleepLock[threadID]);
2089 // If we are master and all slaves have finished do not go to sleep
2090 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2091 allFinished = (i == activeThreads);
2093 if (allFinished || allThreadsShouldExit)
2095 lock_release(&sleepLock[threadID]);
2099 // Do sleep here after retesting sleep conditions
2100 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2101 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2103 lock_release(&sleepLock[threadID]);
2106 // If this thread has been assigned work, launch a search
2107 if (threads[threadID].state == THREAD_WORKISWAITING)
2109 assert(!allThreadsShouldExit);
2111 threads[threadID].state = THREAD_SEARCHING;
2113 // Copy SplitPoint position and search stack and call search()
2114 // with SplitPoint template parameter set to true.
2115 SearchStack ss[PLY_MAX_PLUS_2];
2116 SplitPoint* tsp = threads[threadID].splitPoint;
2117 Position pos(*tsp->pos, threadID);
2119 memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
2123 search<PV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2125 search<NonPV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2127 assert(threads[threadID].state == THREAD_SEARCHING);
2129 threads[threadID].state = THREAD_AVAILABLE;
2131 // Wake up master thread so to allow it to return from the idle loop in
2132 // case we are the last slave of the split point.
2133 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2134 wake_sleeping_thread(tsp->master);
2137 // If this thread is the master of a split point and all slaves have
2138 // finished their work at this split point, return from the idle loop.
2139 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2140 allFinished = (i == activeThreads);
2144 // Because sp->slaves[] is reset under lock protection,
2145 // be sure sp->lock has been released before to return.
2146 lock_grab(&(sp->lock));
2147 lock_release(&(sp->lock));
2149 // In helpful master concept a master can help only a sub-tree, and
2150 // because here is all finished is not possible master is booked.
2151 assert(threads[threadID].state == THREAD_AVAILABLE);
2153 threads[threadID].state = THREAD_SEARCHING;
2160 // init_threads() is called during startup. It launches all helper threads,
2161 // and initializes the split point stack and the global locks and condition
2164 void ThreadsManager::init_threads() {
2166 int i, arg[MAX_THREADS];
2169 // Initialize global locks
2172 for (i = 0; i < MAX_THREADS; i++)
2174 lock_init(&sleepLock[i]);
2175 cond_init(&sleepCond[i]);
2178 // Initialize splitPoints[] locks
2179 for (i = 0; i < MAX_THREADS; i++)
2180 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2181 lock_init(&(threads[i].splitPoints[j].lock));
2183 // Will be set just before program exits to properly end the threads
2184 allThreadsShouldExit = false;
2186 // Threads will be put all threads to sleep as soon as created
2189 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2190 threads[0].state = THREAD_SEARCHING;
2191 for (i = 1; i < MAX_THREADS; i++)
2192 threads[i].state = THREAD_INITIALIZING;
2194 // Launch the helper threads
2195 for (i = 1; i < MAX_THREADS; i++)
2199 #if !defined(_MSC_VER)
2200 pthread_t pthread[1];
2201 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2202 pthread_detach(pthread[0]);
2204 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2208 cout << "Failed to create thread number " << i << endl;
2212 // Wait until the thread has finished launching and is gone to sleep
2213 while (threads[i].state == THREAD_INITIALIZING) {}
2218 // exit_threads() is called when the program exits. It makes all the
2219 // helper threads exit cleanly.
2221 void ThreadsManager::exit_threads() {
2223 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2225 // Wake up all the threads and waits for termination
2226 for (int i = 1; i < MAX_THREADS; i++)
2228 wake_sleeping_thread(i);
2229 while (threads[i].state != THREAD_TERMINATED) {}
2232 // Now we can safely destroy the locks
2233 for (int i = 0; i < MAX_THREADS; i++)
2234 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2235 lock_destroy(&(threads[i].splitPoints[j].lock));
2237 lock_destroy(&mpLock);
2239 // Now we can safely destroy the wait conditions
2240 for (int i = 0; i < MAX_THREADS; i++)
2242 lock_destroy(&sleepLock[i]);
2243 cond_destroy(&sleepCond[i]);
2248 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2249 // the thread's currently active split point, or in some ancestor of
2250 // the current split point.
2252 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2254 assert(threadID >= 0 && threadID < activeThreads);
2256 SplitPoint* sp = threads[threadID].splitPoint;
2258 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2263 // thread_is_available() checks whether the thread with threadID "slave" is
2264 // available to help the thread with threadID "master" at a split point. An
2265 // obvious requirement is that "slave" must be idle. With more than two
2266 // threads, this is not by itself sufficient: If "slave" is the master of
2267 // some active split point, it is only available as a slave to the other
2268 // threads which are busy searching the split point at the top of "slave"'s
2269 // split point stack (the "helpful master concept" in YBWC terminology).
2271 bool ThreadsManager::thread_is_available(int slave, int master) const {
2273 assert(slave >= 0 && slave < activeThreads);
2274 assert(master >= 0 && master < activeThreads);
2275 assert(activeThreads > 1);
2277 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2280 // Make a local copy to be sure doesn't change under our feet
2281 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2283 // No active split points means that the thread is available as
2284 // a slave for any other thread.
2285 if (localActiveSplitPoints == 0 || activeThreads == 2)
2288 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2289 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2290 // could have been set to 0 by another thread leading to an out of bound access.
2291 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2298 // available_thread_exists() tries to find an idle thread which is available as
2299 // a slave for the thread with threadID "master".
2301 bool ThreadsManager::available_thread_exists(int master) const {
2303 assert(master >= 0 && master < activeThreads);
2304 assert(activeThreads > 1);
2306 for (int i = 0; i < activeThreads; i++)
2307 if (thread_is_available(i, master))
2314 // split() does the actual work of distributing the work at a node between
2315 // several available threads. If it does not succeed in splitting the
2316 // node (because no idle threads are available, or because we have no unused
2317 // split point objects), the function immediately returns. If splitting is
2318 // possible, a SplitPoint object is initialized with all the data that must be
2319 // copied to the helper threads and we tell our helper threads that they have
2320 // been assigned work. This will cause them to instantly leave their idle loops and
2321 // call search().When all threads have returned from search() then split() returns.
2323 template <bool Fake>
2324 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2325 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2326 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2327 assert(pos.is_ok());
2328 assert(ply > 0 && ply < PLY_MAX);
2329 assert(*bestValue >= -VALUE_INFINITE);
2330 assert(*bestValue <= *alpha);
2331 assert(*alpha < beta);
2332 assert(beta <= VALUE_INFINITE);
2333 assert(depth > DEPTH_ZERO);
2334 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2335 assert(activeThreads > 1);
2337 int i, master = pos.thread();
2338 Thread& masterThread = threads[master];
2342 // If no other thread is available to help us, or if we have too many
2343 // active split points, don't split.
2344 if ( !available_thread_exists(master)
2345 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2347 lock_release(&mpLock);
2351 // Pick the next available split point object from the split point stack
2352 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2354 // Initialize the split point object
2355 splitPoint.parent = masterThread.splitPoint;
2356 splitPoint.master = master;
2357 splitPoint.betaCutoff = false;
2358 splitPoint.ply = ply;
2359 splitPoint.depth = depth;
2360 splitPoint.threatMove = threatMove;
2361 splitPoint.mateThreat = mateThreat;
2362 splitPoint.alpha = *alpha;
2363 splitPoint.beta = beta;
2364 splitPoint.pvNode = pvNode;
2365 splitPoint.bestValue = *bestValue;
2367 splitPoint.moveCount = moveCount;
2368 splitPoint.pos = &pos;
2369 splitPoint.nodes = 0;
2371 for (i = 0; i < activeThreads; i++)
2372 splitPoint.slaves[i] = 0;
2374 masterThread.splitPoint = &splitPoint;
2376 // If we are here it means we are not available
2377 assert(masterThread.state != THREAD_AVAILABLE);
2379 int workersCnt = 1; // At least the master is included
2381 // Allocate available threads setting state to THREAD_BOOKED
2382 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2383 if (thread_is_available(i, master))
2385 threads[i].state = THREAD_BOOKED;
2386 threads[i].splitPoint = &splitPoint;
2387 splitPoint.slaves[i] = 1;
2391 assert(Fake || workersCnt > 1);
2393 // We can release the lock because slave threads are already booked and master is not available
2394 lock_release(&mpLock);
2396 // Tell the threads that they have work to do. This will make them leave
2398 for (i = 0; i < activeThreads; i++)
2399 if (i == master || splitPoint.slaves[i])
2401 assert(i == master || threads[i].state == THREAD_BOOKED);
2403 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2405 if (useSleepingThreads && i != master)
2406 wake_sleeping_thread(i);
2409 // Everything is set up. The master thread enters the idle loop, from
2410 // which it will instantly launch a search, because its state is
2411 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2412 // idle loop, which means that the main thread will return from the idle
2413 // loop when all threads have finished their work at this split point.
2414 idle_loop(master, &splitPoint);
2416 // We have returned from the idle loop, which means that all threads are
2417 // finished. Update alpha and bestValue, and return.
2420 *alpha = splitPoint.alpha;
2421 *bestValue = splitPoint.bestValue;
2422 masterThread.activeSplitPoints--;
2423 masterThread.splitPoint = splitPoint.parent;
2424 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2426 lock_release(&mpLock);
2430 // wake_sleeping_thread() wakes up the thread with the given threadID
2431 // when it is time to start a new search.
2433 void ThreadsManager::wake_sleeping_thread(int threadID) {
2435 lock_grab(&sleepLock[threadID]);
2436 cond_signal(&sleepCond[threadID]);
2437 lock_release(&sleepLock[threadID]);
2441 /// RootMove and RootMoveList method's definitions
2443 RootMove::RootMove() {
2446 pv_score = non_pv_score = -VALUE_INFINITE;
2450 RootMove& RootMove::operator=(const RootMove& rm) {
2452 const Move* src = rm.pv;
2455 // Avoid a costly full rm.pv[] copy
2456 do *dst++ = *src; while (*src++ != MOVE_NONE);
2459 pv_score = rm.pv_score;
2460 non_pv_score = rm.non_pv_score;
2464 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2465 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2466 // allow to always have a ponder move even when we fail high at root and also a
2467 // long PV to print that is important for position analysis.
2469 void RootMove::extract_pv_from_tt(Position& pos) {
2471 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2475 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2477 pos.do_move(pv[0], *st++);
2479 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2480 && tte->move() != MOVE_NONE
2481 && move_is_legal(pos, tte->move())
2483 && (!pos.is_draw() || ply < 2))
2485 pv[ply] = tte->move();
2486 pos.do_move(pv[ply++], *st++);
2488 pv[ply] = MOVE_NONE;
2490 do pos.undo_move(pv[--ply]); while (ply);
2493 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2494 // the PV back into the TT. This makes sure the old PV moves are searched
2495 // first, even if the old TT entries have been overwritten.
2497 void RootMove::insert_pv_in_tt(Position& pos) {
2499 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2502 Value v, m = VALUE_NONE;
2505 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2509 tte = TT.retrieve(k);
2511 // Don't overwrite existing correct entries
2512 if (!tte || tte->move() != pv[ply])
2514 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2515 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2517 pos.do_move(pv[ply], *st++);
2519 } while (pv[++ply] != MOVE_NONE);
2521 do pos.undo_move(pv[--ply]); while (ply);
2524 // pv_info_to_uci() returns a string with information on the current PV line
2525 // formatted according to UCI specification. It is called at each iteration
2526 // or after a new pv is found.
2528 std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
2530 std::stringstream s, l;
2533 while (*m != MOVE_NONE)
2536 s << "info depth " << depth
2537 << " seldepth " << int(m - pv)
2538 << " multipv " << pvLine + 1
2539 << " score " << value_to_uci(pv_score)
2540 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2541 << " time " << current_search_time()
2542 << " nodes " << pos.nodes_searched()
2543 << " nps " << nps(pos)
2544 << " pv " << l.str();
2550 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2552 MoveStack mlist[MOVES_MAX];
2556 bestMoveChanges = 0;
2558 // Generate all legal moves and score them
2559 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2560 qsearch_scoring(pos, mlist, last);
2562 // Add each move to the RootMoveList's vector
2563 for (MoveStack* cur = mlist; cur != last; cur++)
2565 // If we have a searchMoves[] list then verify cur->move
2566 // is in the list before to add it.
2567 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2569 if (searchMoves[0] && *sm != cur->move)
2573 rm.pv[0] = cur->move;
2574 rm.pv[1] = MOVE_NONE;
2575 rm.pv_score = Value(cur->score);