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 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], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
207 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
209 // Minimum depth for use of singular extension
210 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
212 // If the TT move is at least SingularExtensionMargin better then the
213 // remaining ones we will extend it.
214 const Value SingularExtensionMargin = Value(0x20);
216 // Step 12. Futility pruning
218 // Futility margin for quiescence search
219 const Value FutilityMarginQS = Value(0x80);
221 // Futility lookup tables (initialized at startup) and their getter functions
222 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
223 int FutilityMoveCountArray[32]; // [depth]
225 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
226 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
228 // Step 14. Reduced search
230 // Reduction lookup tables (initialized at startup) and their getter functions
231 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
233 template <NodeType PV>
234 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
236 // 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 managment 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 singleEvasion, 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);
306 int current_search_time();
307 std::string value_to_uci(Value v);
308 int nps(const Position& pos);
309 void poll(const Position& pos);
310 void wait_for_stop_or_ponderhit();
312 #if !defined(_MSC_VER)
313 void* init_thread(void* threadID);
315 DWORD WINAPI init_thread(LPVOID threadID);
319 // MovePickerExt is an extended MovePicker used to choose at compile time
320 // the proper move source according to the type of node.
321 template<bool SpNode, bool Root> struct MovePickerExt;
323 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
324 // before to search them.
325 template<> struct MovePickerExt<false, true> : public MovePicker {
327 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
328 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
330 Value score = VALUE_ZERO;
332 // Score root moves using the standard way used in main search, the moves
333 // are scored according to the order in which are returned by MovePicker.
334 // This is the second order score that is used to compare the moves when
335 // the first order pv scores of both moves are equal.
336 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
337 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
338 if (rm->pv[0] == move)
340 rm->non_pv_score = score--;
348 Move get_next_move() {
355 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
357 int number_of_evasions() const { return (int)Rml.size(); }
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 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
504 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
505 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
506 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
507 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
508 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
509 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
510 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
511 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
512 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
513 MultiPV = Options["MultiPV"].value<int>();
514 UseLogFile = Options["Use Search Log"].value<bool>();
516 read_evaluation_uci_options(pos.side_to_move());
518 // Set the number of active threads
519 ThreadsMgr.read_uci_options();
520 init_eval(ThreadsMgr.active_threads());
522 // Wake up needed threads
523 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
524 ThreadsMgr.wake_sleeping_thread(i);
527 int myTime = time[pos.side_to_move()];
528 int myIncrement = increment[pos.side_to_move()];
529 if (UseTimeManagement)
530 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
532 // Set best NodesBetweenPolls interval to avoid lagging under
533 // heavy time pressure.
535 NodesBetweenPolls = Min(MaxNodes, 30000);
536 else if (myTime && myTime < 1000)
537 NodesBetweenPolls = 1000;
538 else if (myTime && myTime < 5000)
539 NodesBetweenPolls = 5000;
541 NodesBetweenPolls = 30000;
543 // Write search information to log file
546 std::string name = Options["Search Log Filename"].value<std::string>();
547 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
549 LogFile << "Searching: " << pos.to_fen()
550 << "\ninfinite: " << infinite
551 << " ponder: " << ponder
552 << " time: " << myTime
553 << " increment: " << myIncrement
554 << " moves to go: " << movesToGo << endl;
557 // We're ready to start thinking. Call the iterative deepening loop function
558 Move ponderMove = MOVE_NONE;
559 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
561 // Print final search statistics
562 cout << "info nodes " << pos.nodes_searched()
563 << " nps " << nps(pos)
564 << " time " << current_search_time() << endl;
568 LogFile << "\nNodes: " << pos.nodes_searched()
569 << "\nNodes/second: " << nps(pos)
570 << "\nBest move: " << move_to_san(pos, bestMove);
573 pos.do_move(bestMove, st);
574 LogFile << "\nPonder move: "
575 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
578 // Return from think() with unchanged position
579 pos.undo_move(bestMove);
584 // This makes all the threads to go to sleep
585 ThreadsMgr.set_active_threads(1);
587 // If we are pondering or in infinite search, we shouldn't print the
588 // best move before we are told to do so.
589 if (!StopRequest && (Pondering || InfiniteSearch))
590 wait_for_stop_or_ponderhit();
592 // Could be both MOVE_NONE when searching on a stalemate position
593 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
601 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
602 // with increasing depth until the allocated thinking time has been consumed,
603 // user stops the search, or the maximum search depth is reached.
605 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
607 SearchStack ss[PLY_MAX_PLUS_2];
608 Value bestValues[PLY_MAX_PLUS_2];
609 int bestMoveChanges[PLY_MAX_PLUS_2];
610 int iteration, researchCountFL, researchCountFH, aspirationDelta;
611 Value value, alpha, beta;
613 Move bestMove, easyMove;
615 // Moves to search are verified, scored and sorted
616 Rml.init(pos, searchMoves);
618 // Initialize FIXME move before Rml.init()
621 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
622 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
623 *ponderMove = bestMove = easyMove = MOVE_NONE;
626 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
628 // Handle special case of searching on a mate/stale position
631 cout << "info depth " << iteration << " score "
632 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
638 // Send initial scoring (iteration 1)
639 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
640 << "info depth " << iteration
641 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
643 // Is one move significantly better than others after initial scoring ?
645 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
646 easyMove = Rml[0].pv[0];
648 // Iterative deepening loop
649 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
651 cout << "info depth " << iteration << endl;
653 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
654 depth = (iteration - 1) * ONE_PLY;
656 // Calculate dynamic aspiration window based on previous iterations
657 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
659 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
660 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
662 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
663 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
665 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
666 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
669 // Start with a small aspiration window and, in case of fail high/low,
670 // research with bigger window until not failing high/low anymore.
673 // Search starting from ss+1 to allow calling update_gains()
674 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
676 // Write PV lines to transposition table, in case the relevant entries
677 // have been overwritten during the search.
678 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
679 Rml[i].insert_pv_in_tt(pos);
681 // Value cannot be trusted. Break out immediately!
685 assert(value >= alpha);
687 // In case of failing high/low increase aspiration window and research,
688 // otherwise exit the fail high/low loop.
691 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
694 else if (value <= alpha)
696 AspirationFailLow = true;
697 StopOnPonderhit = false;
699 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
706 // Collect info about search result
707 bestMove = Rml[0].pv[0];
708 bestValues[iteration] = value;
709 bestMoveChanges[iteration] = Rml.bestMoveChanges;
711 // Drop the easy move if differs from the new best move
712 if (bestMove != easyMove)
713 easyMove = MOVE_NONE;
715 if (UseTimeManagement && !StopRequest)
718 bool noMoreTime = false;
720 // Stop search early when the last two iterations returned a mate score
722 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
723 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
726 // Stop search early if one move seems to be much better than the
727 // others or if there is only a single legal move. In this latter
728 // case we search up to Iteration 8 anyway to get a proper score.
730 && easyMove == bestMove
732 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
733 && current_search_time() > TimeMgr.available_time() / 16)
734 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
735 && current_search_time() > TimeMgr.available_time() / 32)))
738 // Add some extra time if the best move has changed during the last two iterations
739 if (iteration > 5 && iteration <= 50)
740 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
742 // Stop search if most of MaxSearchTime is consumed at the end of the
743 // iteration. We probably don't have enough time to search the first
744 // move at the next iteration anyway.
745 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
751 StopOnPonderhit = true;
758 *ponderMove = Rml[0].pv[1];
763 // search<>() is the main search function for both PV and non-PV nodes and for
764 // normal and SplitPoint nodes. When called just after a split point the search
765 // is simpler because we have already probed the hash table, done a null move
766 // search, and searched the first move before splitting, we don't have to repeat
767 // all this work again. We also don't need to store anything to the hash table
768 // here: This is taken care of after we return from the split point.
770 template <NodeType PvNode, bool SpNode, bool Root>
771 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
773 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
774 assert(beta > alpha && beta <= VALUE_INFINITE);
775 assert(PvNode || alpha == beta - 1);
776 assert((Root || ply > 0) && ply < PLY_MAX);
777 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
779 Move movesSearched[MOVES_MAX];
784 Move ttMove, move, excludedMove, threatMove;
787 Value bestValue, value, oldAlpha;
788 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
789 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
790 bool mateThreat = false;
791 int moveCount = 0, playedMoveCount = 0;
792 int threadID = pos.thread();
793 SplitPoint* sp = NULL;
795 refinedValue = bestValue = value = -VALUE_INFINITE;
797 isCheck = pos.is_check();
803 ttMove = excludedMove = MOVE_NONE;
804 threatMove = sp->threatMove;
805 mateThreat = sp->mateThreat;
806 goto split_point_start;
811 // Step 1. Initialize node and poll. Polling can abort search
812 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
813 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
815 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
821 // Step 2. Check for aborted search and immediate draw
823 || ThreadsMgr.cutoff_at_splitpoint(threadID)
825 || ply >= PLY_MAX - 1) && !Root)
828 // Step 3. Mate distance pruning
829 alpha = Max(value_mated_in(ply), alpha);
830 beta = Min(value_mate_in(ply+1), beta);
834 // 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
876 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
878 // Step 6. Razoring (is omitted in PV nodes)
880 && depth < RazorDepth
882 && refinedValue < beta - razor_margin(depth)
883 && ttMove == MOVE_NONE
884 && !value_is_mate(beta)
885 && !pos.has_pawn_on_7th(pos.side_to_move()))
887 Value rbeta = beta - razor_margin(depth);
888 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
890 // Logically we should return (v + razor_margin(depth)), but
891 // surprisingly this did slightly weaker in tests.
895 // Step 7. Static null move pruning (is omitted in PV nodes)
896 // We're betting that the opponent doesn't have a move that will reduce
897 // the score by more than futility_margin(depth) if we do a null move.
900 && depth < RazorDepth
902 && refinedValue >= beta + futility_margin(depth, 0)
903 && !value_is_mate(beta)
904 && pos.non_pawn_material(pos.side_to_move()))
905 return refinedValue - futility_margin(depth, 0);
907 // Step 8. Null move search with verification search (is omitted in PV nodes)
912 && refinedValue >= beta
913 && !value_is_mate(beta)
914 && pos.non_pawn_material(pos.side_to_move()))
916 ss->currentMove = MOVE_NULL;
918 // Null move dynamic reduction based on depth
919 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
921 // Null move dynamic reduction based on value
922 if (refinedValue - beta > PawnValueMidgame)
925 pos.do_null_move(st);
926 (ss+1)->skipNullMove = true;
927 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
928 (ss+1)->skipNullMove = false;
929 pos.undo_null_move();
931 if (nullValue >= beta)
933 // Do not return unproven mate scores
934 if (nullValue >= value_mate_in(PLY_MAX))
937 if (depth < 6 * ONE_PLY)
940 // Do verification search at high depths
941 ss->skipNullMove = true;
942 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
943 ss->skipNullMove = false;
950 // The null move failed low, which means that we may be faced with
951 // some kind of threat. If the previous move was reduced, check if
952 // the move that refuted the null move was somehow connected to the
953 // move which was reduced. If a connection is found, return a fail
954 // low score (which will cause the reduced move to fail high in the
955 // parent node, which will trigger a re-search with full depth).
956 if (nullValue == value_mated_in(ply + 2))
959 threatMove = (ss+1)->bestMove;
960 if ( depth < ThreatDepth
962 && threatMove != MOVE_NONE
963 && connected_moves(pos, (ss-1)->currentMove, threatMove))
968 // Step 9. Internal iterative deepening
969 if ( depth >= IIDDepth[PvNode]
970 && ttMove == MOVE_NONE
971 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
973 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
975 ss->skipNullMove = true;
976 search<PvNode>(pos, ss, alpha, beta, d, ply);
977 ss->skipNullMove = false;
979 ttMove = ss->bestMove;
980 tte = TT.retrieve(posKey);
983 // Expensive mate threat detection (only for PV nodes)
985 mateThreat = pos.has_mate_threat();
987 split_point_start: // At split points actual search starts from here
989 // Initialize a MovePicker object for the current position
990 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
992 ss->bestMove = MOVE_NONE;
993 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
994 futilityBase = ss->eval + ss->evalMargin;
995 singularExtensionNode = !Root
997 && depth >= SingularExtensionDepth[PvNode]
1000 && !excludedMove // Do not allow recursive singular extension search
1001 && (tte->type() & VALUE_TYPE_LOWER)
1002 && tte->depth() >= depth - 3 * ONE_PLY;
1005 lock_grab(&(sp->lock));
1006 bestValue = sp->bestValue;
1009 // Step 10. Loop through moves
1010 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1011 while ( bestValue < beta
1012 && (move = mp.get_next_move()) != MOVE_NONE
1013 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1015 assert(move_is_ok(move));
1019 moveCount = ++sp->moveCount;
1020 lock_release(&(sp->lock));
1022 else if (move == excludedMove)
1029 // This is used by time management
1030 FirstRootMove = (moveCount == 1);
1032 // Save the current node count before the move is searched
1033 nodes = pos.nodes_searched();
1035 // If it's time to send nodes info, do it here where we have the
1036 // correct accumulated node counts searched by each thread.
1037 if (SendSearchedNodes)
1039 SendSearchedNodes = false;
1040 cout << "info nodes " << nodes
1041 << " nps " << nps(pos)
1042 << " time " << current_search_time() << endl;
1045 if (current_search_time() >= 1000)
1046 cout << "info currmove " << move
1047 << " currmovenumber " << moveCount << endl;
1050 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1051 moveIsCheck = pos.move_is_check(move, ci);
1052 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1054 // Step 11. Decide the new search depth
1055 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1057 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1058 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1059 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1060 // lower then ttValue minus a margin then we extend ttMove.
1061 if ( singularExtensionNode
1062 && move == tte->move()
1065 Value ttValue = value_from_tt(tte->value(), ply);
1067 if (abs(ttValue) < VALUE_KNOWN_WIN)
1069 Value b = ttValue - SingularExtensionMargin;
1070 ss->excludedMove = move;
1071 ss->skipNullMove = true;
1072 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1073 ss->skipNullMove = false;
1074 ss->excludedMove = MOVE_NONE;
1075 ss->bestMove = MOVE_NONE;
1081 // Update current move (this must be done after singular extension search)
1082 ss->currentMove = move;
1083 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1085 // Step 12. Futility pruning (is omitted in PV nodes)
1087 && !captureOrPromotion
1091 && !move_is_castle(move))
1093 // Move count based pruning
1094 if ( moveCount >= futility_move_count(depth)
1095 && !(threatMove && connected_threat(pos, move, threatMove))
1096 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1099 lock_grab(&(sp->lock));
1104 // Value based pruning
1105 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1106 // but fixing this made program slightly weaker.
1107 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1108 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1109 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1111 if (futilityValueScaled < beta)
1115 lock_grab(&(sp->lock));
1116 if (futilityValueScaled > sp->bestValue)
1117 sp->bestValue = bestValue = futilityValueScaled;
1119 else if (futilityValueScaled > bestValue)
1120 bestValue = futilityValueScaled;
1125 // Prune moves with negative SEE at low depths
1126 if ( predictedDepth < 2 * ONE_PLY
1127 && bestValue > value_mated_in(PLY_MAX)
1128 && pos.see_sign(move) < 0)
1131 lock_grab(&(sp->lock));
1137 // Step 13. Make the move
1138 pos.do_move(move, st, ci, moveIsCheck);
1140 if (!SpNode && !captureOrPromotion)
1141 movesSearched[playedMoveCount++] = move;
1143 // Step extra. pv search (only in PV nodes)
1144 // The first move in list is the expected PV
1147 // Aspiration window is disabled in multi-pv case
1148 if (Root && MultiPV > 1)
1149 alpha = -VALUE_INFINITE;
1151 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1155 // Step 14. Reduced depth search
1156 // If the move fails high will be re-searched at full depth.
1157 bool doFullDepthSearch = true;
1159 if ( depth >= 3 * ONE_PLY
1160 && !captureOrPromotion
1162 && !move_is_castle(move)
1163 && ss->killers[0] != move
1164 && ss->killers[1] != move)
1166 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1167 : reduction<PvNode>(depth, moveCount);
1170 alpha = SpNode ? sp->alpha : alpha;
1171 Depth d = newDepth - ss->reduction;
1172 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1174 doFullDepthSearch = (value > alpha);
1176 ss->reduction = DEPTH_ZERO; // Restore original reduction
1179 // Step 15. Full depth search
1180 if (doFullDepthSearch)
1182 alpha = SpNode ? sp->alpha : alpha;
1183 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1185 // Step extra. pv search (only in PV nodes)
1186 // Search only for possible new PV nodes, if instead value >= beta then
1187 // parent node fails low with value <= alpha and tries another move.
1188 if (PvNode && value > alpha && (Root || value < beta))
1189 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1193 // Step 16. Undo move
1194 pos.undo_move(move);
1196 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1198 // Step 17. Check for new best move
1201 lock_grab(&(sp->lock));
1202 bestValue = sp->bestValue;
1206 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1211 sp->bestValue = value;
1215 if (PvNode && value < beta) // We want always alpha < beta
1223 sp->betaCutoff = true;
1225 if (value == value_mate_in(ply + 1))
1226 ss->mateKiller = move;
1228 ss->bestMove = move;
1231 sp->parentSstack->bestMove = move;
1237 // To avoid to exit with bestValue == -VALUE_INFINITE
1238 if (value > bestValue)
1241 // Finished searching the move. If StopRequest is true, the search
1242 // was aborted because the user interrupted the search or because we
1243 // ran out of time. In this case, the return value of the search cannot
1244 // be trusted, and we break out of the loop without updating the best
1249 // Remember searched nodes counts for this move
1250 mp.rm->nodes += pos.nodes_searched() - nodes;
1252 // Step 17. Check for new best move
1253 if (!isPvMove && value <= alpha)
1254 mp.rm->pv_score = -VALUE_INFINITE;
1257 // PV move or new best move!
1260 ss->bestMove = move;
1261 mp.rm->pv_score = value;
1262 mp.rm->extract_pv_from_tt(pos);
1264 // We record how often the best move has been changed in each
1265 // iteration. This information is used for time managment: When
1266 // the best move changes frequently, we allocate some more time.
1267 if (!isPvMove && MultiPV == 1)
1268 Rml.bestMoveChanges++;
1270 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1271 // requires we send all the PV lines properly sorted.
1272 Rml.sort_multipv(moveCount);
1274 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1275 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1277 // Update alpha. In multi-pv we don't use aspiration window, so
1278 // set alpha equal to minimum score among the PV lines.
1280 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1281 else if (value > alpha)
1284 } // PV move or new best move
1287 // Step 18. Check for split
1290 && depth >= ThreadsMgr.min_split_depth()
1291 && ThreadsMgr.active_threads() > 1
1293 && ThreadsMgr.available_thread_exists(threadID)
1295 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1296 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1297 threatMove, mateThreat, moveCount, &mp, PvNode);
1300 // Step 19. Check for mate and stalemate
1301 // All legal moves have been searched and if there are
1302 // no legal moves, it must be mate or stalemate.
1303 // If one move was excluded return fail low score.
1304 if (!SpNode && !moveCount)
1305 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1307 // Step 20. Update tables
1308 // If the search is not aborted, update the transposition table,
1309 // history counters, and killer moves.
1310 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1312 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1313 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1314 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1316 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1318 // Update killers and history only for non capture moves that fails high
1319 if ( bestValue >= beta
1320 && !pos.move_is_capture_or_promotion(move))
1322 update_history(pos, move, depth, movesSearched, playedMoveCount);
1323 update_killers(move, ss->killers);
1329 // Here we have the lock still grabbed
1330 sp->slaves[threadID] = 0;
1331 sp->nodes += pos.nodes_searched();
1332 lock_release(&(sp->lock));
1335 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1340 // qsearch() is the quiescence search function, which is called by the main
1341 // search function when the remaining depth is zero (or, to be more precise,
1342 // less than ONE_PLY).
1344 template <NodeType PvNode>
1345 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1347 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1348 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1349 assert(PvNode || alpha == beta - 1);
1351 assert(ply > 0 && ply < PLY_MAX);
1352 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1356 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1357 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1360 Value oldAlpha = alpha;
1362 ss->bestMove = ss->currentMove = MOVE_NONE;
1364 // Check for an instant draw or maximum ply reached
1365 if (pos.is_draw() || ply >= PLY_MAX - 1)
1368 // Decide whether or not to include checks, this fixes also the type of
1369 // TT entry depth that we are going to use. Note that in qsearch we use
1370 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1371 isCheck = pos.is_check();
1372 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1374 // Transposition table lookup. At PV nodes, we don't use the TT for
1375 // pruning, but only for move ordering.
1376 tte = TT.retrieve(pos.get_key());
1377 ttMove = (tte ? tte->move() : MOVE_NONE);
1379 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1381 ss->bestMove = ttMove; // Can be MOVE_NONE
1382 return value_from_tt(tte->value(), ply);
1385 // Evaluate the position statically
1388 bestValue = futilityBase = -VALUE_INFINITE;
1389 ss->eval = evalMargin = VALUE_NONE;
1390 enoughMaterial = false;
1396 assert(tte->static_value() != VALUE_NONE);
1398 evalMargin = tte->static_value_margin();
1399 ss->eval = bestValue = tte->static_value();
1402 ss->eval = bestValue = evaluate(pos, evalMargin);
1404 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1406 // Stand pat. Return immediately if static value is at least beta
1407 if (bestValue >= beta)
1410 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1415 if (PvNode && bestValue > alpha)
1418 // Futility pruning parameters, not needed when in check
1419 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1420 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1423 // Initialize a MovePicker object for the current position, and prepare
1424 // to search the moves. Because the depth is <= 0 here, only captures,
1425 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1427 MovePicker mp(pos, ttMove, depth, H);
1430 // Loop through the moves until no moves remain or a beta cutoff occurs
1431 while ( alpha < beta
1432 && (move = mp.get_next_move()) != MOVE_NONE)
1434 assert(move_is_ok(move));
1436 moveIsCheck = pos.move_is_check(move, ci);
1444 && !move_is_promotion(move)
1445 && !pos.move_is_passed_pawn_push(move))
1447 futilityValue = futilityBase
1448 + pos.endgame_value_of_piece_on(move_to(move))
1449 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1451 if (futilityValue < alpha)
1453 if (futilityValue > bestValue)
1454 bestValue = futilityValue;
1459 // Detect non-capture evasions that are candidate to be pruned
1460 evasionPrunable = isCheck
1461 && bestValue > value_mated_in(PLY_MAX)
1462 && !pos.move_is_capture(move)
1463 && !pos.can_castle(pos.side_to_move());
1465 // Don't search moves with negative SEE values
1467 && (!isCheck || evasionPrunable)
1469 && !move_is_promotion(move)
1470 && pos.see_sign(move) < 0)
1473 // Don't search useless checks
1478 && !pos.move_is_capture_or_promotion(move)
1479 && ss->eval + PawnValueMidgame / 4 < beta
1480 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1482 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1483 bestValue = ss->eval + PawnValueMidgame / 4;
1488 // Update current move
1489 ss->currentMove = move;
1491 // Make and search the move
1492 pos.do_move(move, st, ci, moveIsCheck);
1493 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1494 pos.undo_move(move);
1496 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1499 if (value > bestValue)
1505 ss->bestMove = move;
1510 // All legal moves have been searched. A special case: If we're in check
1511 // and no legal moves were found, it is checkmate.
1512 if (isCheck && bestValue == -VALUE_INFINITE)
1513 return value_mated_in(ply);
1515 // Update transposition table
1516 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1517 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1519 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1525 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1526 // bestValue is updated only when returning false because in that case move
1529 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1531 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1532 Square from, to, ksq, victimSq;
1535 Value futilityValue, bv = *bestValue;
1537 from = move_from(move);
1539 them = opposite_color(pos.side_to_move());
1540 ksq = pos.king_square(them);
1541 kingAtt = pos.attacks_from<KING>(ksq);
1542 pc = pos.piece_on(from);
1544 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1545 oldAtt = pos.attacks_from(pc, from, occ);
1546 newAtt = pos.attacks_from(pc, to, occ);
1548 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1549 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1551 if (!(b && (b & (b - 1))))
1554 // Rule 2. Queen contact check is very dangerous
1555 if ( type_of_piece(pc) == QUEEN
1556 && bit_is_set(kingAtt, to))
1559 // Rule 3. Creating new double threats with checks
1560 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1564 victimSq = pop_1st_bit(&b);
1565 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1567 // Note that here we generate illegal "double move"!
1568 if ( futilityValue >= beta
1569 && pos.see_sign(make_move(from, victimSq)) >= 0)
1572 if (futilityValue > bv)
1576 // Update bestValue only if check is not dangerous (because we will prune the move)
1582 // connected_moves() tests whether two moves are 'connected' in the sense
1583 // that the first move somehow made the second move possible (for instance
1584 // if the moving piece is the same in both moves). The first move is assumed
1585 // to be the move that was made to reach the current position, while the
1586 // second move is assumed to be a move from the current position.
1588 bool connected_moves(const Position& pos, Move m1, Move m2) {
1590 Square f1, t1, f2, t2;
1593 assert(m1 && move_is_ok(m1));
1594 assert(m2 && move_is_ok(m2));
1596 // Case 1: The moving piece is the same in both moves
1602 // Case 2: The destination square for m2 was vacated by m1
1608 // Case 3: Moving through the vacated square
1609 if ( piece_is_slider(pos.piece_on(f2))
1610 && bit_is_set(squares_between(f2, t2), f1))
1613 // Case 4: The destination square for m2 is defended by the moving piece in m1
1614 p = pos.piece_on(t1);
1615 if (bit_is_set(pos.attacks_from(p, t1), t2))
1618 // Case 5: Discovered check, checking piece is the piece moved in m1
1619 if ( piece_is_slider(p)
1620 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1621 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1623 // discovered_check_candidates() works also if the Position's side to
1624 // move is the opposite of the checking piece.
1625 Color them = opposite_color(pos.side_to_move());
1626 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1628 if (bit_is_set(dcCandidates, f2))
1635 // value_is_mate() checks if the given value is a mate one eventually
1636 // compensated for the ply.
1638 bool value_is_mate(Value value) {
1640 assert(abs(value) <= VALUE_INFINITE);
1642 return value <= value_mated_in(PLY_MAX)
1643 || value >= value_mate_in(PLY_MAX);
1647 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1648 // "plies to mate from the current ply". Non-mate scores are unchanged.
1649 // The function is called before storing a value to the transposition table.
1651 Value value_to_tt(Value v, int ply) {
1653 if (v >= value_mate_in(PLY_MAX))
1656 if (v <= value_mated_in(PLY_MAX))
1663 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1664 // the transposition table to a mate score corrected for the current ply.
1666 Value value_from_tt(Value v, int ply) {
1668 if (v >= value_mate_in(PLY_MAX))
1671 if (v <= value_mated_in(PLY_MAX))
1678 // extension() decides whether a move should be searched with normal depth,
1679 // or with extended depth. Certain classes of moves (checking moves, in
1680 // particular) are searched with bigger depth than ordinary moves and in
1681 // any case are marked as 'dangerous'. Note that also if a move is not
1682 // extended, as example because the corresponding UCI option is set to zero,
1683 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1684 template <NodeType PvNode>
1685 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1686 bool singleEvasion, bool mateThreat, bool* dangerous) {
1688 assert(m != MOVE_NONE);
1690 Depth result = DEPTH_ZERO;
1691 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1695 if (moveIsCheck && pos.see_sign(m) >= 0)
1696 result += CheckExtension[PvNode];
1699 result += SingleEvasionExtension[PvNode];
1702 result += MateThreatExtension[PvNode];
1705 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1707 Color c = pos.side_to_move();
1708 if (relative_rank(c, move_to(m)) == RANK_7)
1710 result += PawnPushTo7thExtension[PvNode];
1713 if (pos.pawn_is_passed(c, move_to(m)))
1715 result += PassedPawnExtension[PvNode];
1720 if ( captureOrPromotion
1721 && pos.type_of_piece_on(move_to(m)) != PAWN
1722 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1723 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1724 && !move_is_promotion(m)
1727 result += PawnEndgameExtension[PvNode];
1732 && captureOrPromotion
1733 && pos.type_of_piece_on(move_to(m)) != PAWN
1734 && pos.see_sign(m) >= 0)
1736 result += ONE_PLY / 2;
1740 return Min(result, ONE_PLY);
1744 // connected_threat() tests whether it is safe to forward prune a move or if
1745 // is somehow coonected to the threat move returned by null search.
1747 bool connected_threat(const Position& pos, Move m, Move threat) {
1749 assert(move_is_ok(m));
1750 assert(threat && move_is_ok(threat));
1751 assert(!pos.move_is_check(m));
1752 assert(!pos.move_is_capture_or_promotion(m));
1753 assert(!pos.move_is_passed_pawn_push(m));
1755 Square mfrom, mto, tfrom, tto;
1757 mfrom = move_from(m);
1759 tfrom = move_from(threat);
1760 tto = move_to(threat);
1762 // Case 1: Don't prune moves which move the threatened piece
1766 // Case 2: If the threatened piece has value less than or equal to the
1767 // value of the threatening piece, don't prune move which defend it.
1768 if ( pos.move_is_capture(threat)
1769 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1770 || pos.type_of_piece_on(tfrom) == KING)
1771 && pos.move_attacks_square(m, tto))
1774 // Case 3: If the moving piece in the threatened move is a slider, don't
1775 // prune safe moves which block its ray.
1776 if ( piece_is_slider(pos.piece_on(tfrom))
1777 && bit_is_set(squares_between(tfrom, tto), mto)
1778 && pos.see_sign(m) >= 0)
1785 // ok_to_use_TT() returns true if a transposition table score
1786 // can be used at a given point in search.
1788 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1790 Value v = value_from_tt(tte->value(), ply);
1792 return ( tte->depth() >= depth
1793 || v >= Max(value_mate_in(PLY_MAX), beta)
1794 || v < Min(value_mated_in(PLY_MAX), beta))
1796 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1797 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1801 // refine_eval() returns the transposition table score if
1802 // possible otherwise falls back on static position evaluation.
1804 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1808 Value v = value_from_tt(tte->value(), ply);
1810 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1811 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1818 // update_history() registers a good move that produced a beta-cutoff
1819 // in history and marks as failures all the other moves of that ply.
1821 void update_history(const Position& pos, Move move, Depth depth,
1822 Move movesSearched[], int moveCount) {
1824 Value bonus = Value(int(depth) * int(depth));
1826 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1828 for (int i = 0; i < moveCount - 1; i++)
1830 m = movesSearched[i];
1834 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1839 // update_killers() add a good move that produced a beta-cutoff
1840 // among the killer moves of that ply.
1842 void update_killers(Move m, Move killers[]) {
1844 if (m != killers[0])
1846 killers[1] = killers[0];
1852 // update_gains() updates the gains table of a non-capture move given
1853 // the static position evaluation before and after the move.
1855 void update_gains(const Position& pos, Move m, Value before, Value after) {
1858 && before != VALUE_NONE
1859 && after != VALUE_NONE
1860 && pos.captured_piece_type() == PIECE_TYPE_NONE
1861 && !move_is_special(m))
1862 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1866 // value_to_uci() converts a value to a string suitable for use with the UCI
1867 // protocol specifications:
1869 // cp <x> The score from the engine's point of view in centipawns.
1870 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1871 // use negative values for y.
1873 std::string value_to_uci(Value v) {
1875 std::stringstream s;
1877 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1878 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1880 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1886 // current_search_time() returns the number of milliseconds which have passed
1887 // since the beginning of the current search.
1889 int current_search_time() {
1891 return get_system_time() - SearchStartTime;
1895 // nps() computes the current nodes/second count
1897 int nps(const Position& pos) {
1899 int t = current_search_time();
1900 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1904 // poll() performs two different functions: It polls for user input, and it
1905 // looks at the time consumed so far and decides if it's time to abort the
1908 void poll(const Position& pos) {
1910 static int lastInfoTime;
1911 int t = current_search_time();
1914 if (input_available())
1916 // We are line oriented, don't read single chars
1917 std::string command;
1919 if (!std::getline(std::cin, command))
1922 if (command == "quit")
1924 // Quit the program as soon as possible
1926 QuitRequest = StopRequest = true;
1929 else if (command == "stop")
1931 // Stop calculating as soon as possible, but still send the "bestmove"
1932 // and possibly the "ponder" token when finishing the search.
1936 else if (command == "ponderhit")
1938 // The opponent has played the expected move. GUI sends "ponderhit" if
1939 // we were told to ponder on the same move the opponent has played. We
1940 // should continue searching but switching from pondering to normal search.
1943 if (StopOnPonderhit)
1948 // Print search information
1952 else if (lastInfoTime > t)
1953 // HACK: Must be a new search where we searched less than
1954 // NodesBetweenPolls nodes during the first second of search.
1957 else if (t - lastInfoTime >= 1000)
1964 if (dbg_show_hit_rate)
1965 dbg_print_hit_rate();
1967 // Send info on searched nodes as soon as we return to root
1968 SendSearchedNodes = true;
1971 // Should we stop the search?
1975 bool stillAtFirstMove = FirstRootMove
1976 && !AspirationFailLow
1977 && t > TimeMgr.available_time();
1979 bool noMoreTime = t > TimeMgr.maximum_time()
1980 || stillAtFirstMove;
1982 if ( (UseTimeManagement && noMoreTime)
1983 || (ExactMaxTime && t >= ExactMaxTime)
1984 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1989 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1990 // while the program is pondering. The point is to work around a wrinkle in
1991 // the UCI protocol: When pondering, the engine is not allowed to give a
1992 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1993 // We simply wait here until one of these commands is sent, and return,
1994 // after which the bestmove and pondermove will be printed.
1996 void wait_for_stop_or_ponderhit() {
1998 std::string command;
2002 // Wait for a command from stdin
2003 if (!std::getline(std::cin, command))
2006 if (command == "quit")
2011 else if (command == "ponderhit" || command == "stop")
2017 // init_thread() is the function which is called when a new thread is
2018 // launched. It simply calls the idle_loop() function with the supplied
2019 // threadID. There are two versions of this function; one for POSIX
2020 // threads and one for Windows threads.
2022 #if !defined(_MSC_VER)
2024 void* init_thread(void* threadID) {
2026 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2032 DWORD WINAPI init_thread(LPVOID threadID) {
2034 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2041 /// The ThreadsManager class
2044 // read_uci_options() updates number of active threads and other internal
2045 // parameters according to the UCI options values. It is called before
2046 // to start a new search.
2048 void ThreadsManager::read_uci_options() {
2050 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2051 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2052 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2053 activeThreads = Options["Threads"].value<int>();
2057 // idle_loop() is where the threads are parked when they have no work to do.
2058 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2059 // object for which the current thread is the master.
2061 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2063 assert(threadID >= 0 && threadID < MAX_THREADS);
2066 bool allFinished = false;
2070 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2071 // master should exit as last one.
2072 if (allThreadsShouldExit)
2075 threads[threadID].state = THREAD_TERMINATED;
2079 // If we are not thinking, wait for a condition to be signaled
2080 // instead of wasting CPU time polling for work.
2081 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2082 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2084 assert(!sp || useSleepingThreads);
2085 assert(threadID != 0 || useSleepingThreads);
2087 if (threads[threadID].state == THREAD_INITIALIZING)
2088 threads[threadID].state = THREAD_AVAILABLE;
2090 // Grab the lock to avoid races with wake_sleeping_thread()
2091 lock_grab(&sleepLock[threadID]);
2093 // If we are master and all slaves have finished do not go to sleep
2094 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2095 allFinished = (i == activeThreads);
2097 if (allFinished || allThreadsShouldExit)
2099 lock_release(&sleepLock[threadID]);
2103 // Do sleep here after retesting sleep conditions
2104 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2105 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2107 lock_release(&sleepLock[threadID]);
2110 // If this thread has been assigned work, launch a search
2111 if (threads[threadID].state == THREAD_WORKISWAITING)
2113 assert(!allThreadsShouldExit);
2115 threads[threadID].state = THREAD_SEARCHING;
2117 // Here we call search() with SplitPoint template parameter set to true
2118 SplitPoint* tsp = threads[threadID].splitPoint;
2119 Position pos(*tsp->pos, threadID);
2120 SearchStack* ss = tsp->sstack[threadID] + 1;
2124 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2126 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2128 assert(threads[threadID].state == THREAD_SEARCHING);
2130 threads[threadID].state = THREAD_AVAILABLE;
2132 // Wake up master thread so to allow it to return from the idle loop in
2133 // case we are the last slave of the split point.
2134 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2135 wake_sleeping_thread(tsp->master);
2138 // If this thread is the master of a split point and all slaves have
2139 // finished their work at this split point, return from the idle loop.
2140 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2141 allFinished = (i == activeThreads);
2145 // Because sp->slaves[] is reset under lock protection,
2146 // be sure sp->lock has been released before to return.
2147 lock_grab(&(sp->lock));
2148 lock_release(&(sp->lock));
2150 // In helpful master concept a master can help only a sub-tree, and
2151 // because here is all finished is not possible master is booked.
2152 assert(threads[threadID].state == THREAD_AVAILABLE);
2154 threads[threadID].state = THREAD_SEARCHING;
2161 // init_threads() is called during startup. It launches all helper threads,
2162 // and initializes the split point stack and the global locks and condition
2165 void ThreadsManager::init_threads() {
2167 int i, arg[MAX_THREADS];
2170 // Initialize global locks
2173 for (i = 0; i < MAX_THREADS; i++)
2175 lock_init(&sleepLock[i]);
2176 cond_init(&sleepCond[i]);
2179 // Initialize splitPoints[] locks
2180 for (i = 0; i < MAX_THREADS; i++)
2181 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2182 lock_init(&(threads[i].splitPoints[j].lock));
2184 // Will be set just before program exits to properly end the threads
2185 allThreadsShouldExit = false;
2187 // Threads will be put all threads to sleep as soon as created
2190 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2191 threads[0].state = THREAD_SEARCHING;
2192 for (i = 1; i < MAX_THREADS; i++)
2193 threads[i].state = THREAD_INITIALIZING;
2195 // Launch the helper threads
2196 for (i = 1; i < MAX_THREADS; i++)
2200 #if !defined(_MSC_VER)
2201 pthread_t pthread[1];
2202 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2203 pthread_detach(pthread[0]);
2205 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2209 cout << "Failed to create thread number " << i << endl;
2213 // Wait until the thread has finished launching and is gone to sleep
2214 while (threads[i].state == THREAD_INITIALIZING) {}
2219 // exit_threads() is called when the program exits. It makes all the
2220 // helper threads exit cleanly.
2222 void ThreadsManager::exit_threads() {
2224 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2226 // Wake up all the threads and waits for termination
2227 for (int i = 1; i < MAX_THREADS; i++)
2229 wake_sleeping_thread(i);
2230 while (threads[i].state != THREAD_TERMINATED) {}
2233 // Now we can safely destroy the locks
2234 for (int i = 0; i < MAX_THREADS; i++)
2235 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2236 lock_destroy(&(threads[i].splitPoints[j].lock));
2238 lock_destroy(&mpLock);
2240 // Now we can safely destroy the wait conditions
2241 for (int i = 0; i < MAX_THREADS; i++)
2243 lock_destroy(&sleepLock[i]);
2244 cond_destroy(&sleepCond[i]);
2249 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2250 // the thread's currently active split point, or in some ancestor of
2251 // the current split point.
2253 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2255 assert(threadID >= 0 && threadID < activeThreads);
2257 SplitPoint* sp = threads[threadID].splitPoint;
2259 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2264 // thread_is_available() checks whether the thread with threadID "slave" is
2265 // available to help the thread with threadID "master" at a split point. An
2266 // obvious requirement is that "slave" must be idle. With more than two
2267 // threads, this is not by itself sufficient: If "slave" is the master of
2268 // some active split point, it is only available as a slave to the other
2269 // threads which are busy searching the split point at the top of "slave"'s
2270 // split point stack (the "helpful master concept" in YBWC terminology).
2272 bool ThreadsManager::thread_is_available(int slave, int master) const {
2274 assert(slave >= 0 && slave < activeThreads);
2275 assert(master >= 0 && master < activeThreads);
2276 assert(activeThreads > 1);
2278 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2281 // Make a local copy to be sure doesn't change under our feet
2282 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2284 // No active split points means that the thread is available as
2285 // a slave for any other thread.
2286 if (localActiveSplitPoints == 0 || activeThreads == 2)
2289 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2290 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2291 // could have been set to 0 by another thread leading to an out of bound access.
2292 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2299 // available_thread_exists() tries to find an idle thread which is available as
2300 // a slave for the thread with threadID "master".
2302 bool ThreadsManager::available_thread_exists(int master) const {
2304 assert(master >= 0 && master < activeThreads);
2305 assert(activeThreads > 1);
2307 for (int i = 0; i < activeThreads; i++)
2308 if (thread_is_available(i, master))
2315 // split() does the actual work of distributing the work at a node between
2316 // several available threads. If it does not succeed in splitting the
2317 // node (because no idle threads are available, or because we have no unused
2318 // split point objects), the function immediately returns. If splitting is
2319 // possible, a SplitPoint object is initialized with all the data that must be
2320 // copied to the helper threads and we tell our helper threads that they have
2321 // been assigned work. This will cause them to instantly leave their idle loops and
2322 // call search().When all threads have returned from search() then split() returns.
2324 template <bool Fake>
2325 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2326 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2327 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2328 assert(pos.is_ok());
2329 assert(ply > 0 && ply < PLY_MAX);
2330 assert(*bestValue >= -VALUE_INFINITE);
2331 assert(*bestValue <= *alpha);
2332 assert(*alpha < beta);
2333 assert(beta <= VALUE_INFINITE);
2334 assert(depth > DEPTH_ZERO);
2335 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2336 assert(activeThreads > 1);
2338 int i, master = pos.thread();
2339 Thread& masterThread = threads[master];
2343 // If no other thread is available to help us, or if we have too many
2344 // active split points, don't split.
2345 if ( !available_thread_exists(master)
2346 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2348 lock_release(&mpLock);
2352 // Pick the next available split point object from the split point stack
2353 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2355 // Initialize the split point object
2356 splitPoint.parent = masterThread.splitPoint;
2357 splitPoint.master = master;
2358 splitPoint.betaCutoff = false;
2359 splitPoint.ply = ply;
2360 splitPoint.depth = depth;
2361 splitPoint.threatMove = threatMove;
2362 splitPoint.mateThreat = mateThreat;
2363 splitPoint.alpha = *alpha;
2364 splitPoint.beta = beta;
2365 splitPoint.pvNode = pvNode;
2366 splitPoint.bestValue = *bestValue;
2368 splitPoint.moveCount = moveCount;
2369 splitPoint.pos = &pos;
2370 splitPoint.nodes = 0;
2371 splitPoint.parentSstack = ss;
2372 for (i = 0; i < activeThreads; i++)
2373 splitPoint.slaves[i] = 0;
2375 masterThread.splitPoint = &splitPoint;
2377 // If we are here it means we are not available
2378 assert(masterThread.state != THREAD_AVAILABLE);
2380 int workersCnt = 1; // At least the master is included
2382 // Allocate available threads setting state to THREAD_BOOKED
2383 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2384 if (thread_is_available(i, master))
2386 threads[i].state = THREAD_BOOKED;
2387 threads[i].splitPoint = &splitPoint;
2388 splitPoint.slaves[i] = 1;
2392 assert(Fake || workersCnt > 1);
2394 // We can release the lock because slave threads are already booked and master is not available
2395 lock_release(&mpLock);
2397 // Tell the threads that they have work to do. This will make them leave
2398 // their idle loop. But before copy search stack tail for each thread.
2399 for (i = 0; i < activeThreads; i++)
2400 if (i == master || splitPoint.slaves[i])
2402 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2404 assert(i == master || threads[i].state == THREAD_BOOKED);
2406 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2408 if (useSleepingThreads && i != master)
2409 wake_sleeping_thread(i);
2412 // Everything is set up. The master thread enters the idle loop, from
2413 // which it will instantly launch a search, because its state is
2414 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2415 // idle loop, which means that the main thread will return from the idle
2416 // loop when all threads have finished their work at this split point.
2417 idle_loop(master, &splitPoint);
2419 // We have returned from the idle loop, which means that all threads are
2420 // finished. Update alpha and bestValue, and return.
2423 *alpha = splitPoint.alpha;
2424 *bestValue = splitPoint.bestValue;
2425 masterThread.activeSplitPoints--;
2426 masterThread.splitPoint = splitPoint.parent;
2427 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2429 lock_release(&mpLock);
2433 // wake_sleeping_thread() wakes up the thread with the given threadID
2434 // when it is time to start a new search.
2436 void ThreadsManager::wake_sleeping_thread(int threadID) {
2438 lock_grab(&sleepLock[threadID]);
2439 cond_signal(&sleepCond[threadID]);
2440 lock_release(&sleepLock[threadID]);
2444 /// RootMove and RootMoveList method's definitions
2446 RootMove::RootMove() {
2449 pv_score = non_pv_score = -VALUE_INFINITE;
2453 RootMove& RootMove::operator=(const RootMove& rm) {
2455 const Move* src = rm.pv;
2458 // Avoid a costly full rm.pv[] copy
2459 do *dst++ = *src; while (*src++ != MOVE_NONE);
2462 pv_score = rm.pv_score;
2463 non_pv_score = rm.non_pv_score;
2467 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2468 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2469 // allow to always have a ponder move even when we fail high at root and also a
2470 // long PV to print that is important for position analysis.
2472 void RootMove::extract_pv_from_tt(Position& pos) {
2474 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2478 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2480 pos.do_move(pv[0], *st++);
2482 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2483 && tte->move() != MOVE_NONE
2484 && move_is_legal(pos, tte->move())
2486 && (!pos.is_draw() || ply < 2))
2488 pv[ply] = tte->move();
2489 pos.do_move(pv[ply++], *st++);
2491 pv[ply] = MOVE_NONE;
2493 do pos.undo_move(pv[--ply]); while (ply);
2496 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2497 // the PV back into the TT. This makes sure the old PV moves are searched
2498 // first, even if the old TT entries have been overwritten.
2500 void RootMove::insert_pv_in_tt(Position& pos) {
2502 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2505 Value v, m = VALUE_NONE;
2508 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2512 tte = TT.retrieve(k);
2514 // Don't overwrite exsisting correct entries
2515 if (!tte || tte->move() != pv[ply])
2517 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2518 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2520 pos.do_move(pv[ply], *st++);
2522 } while (pv[++ply] != MOVE_NONE);
2524 do pos.undo_move(pv[--ply]); while (ply);
2527 // pv_info_to_uci() returns a string with information on the current PV line
2528 // formatted according to UCI specification and eventually writes the info
2529 // to a log file. It is called at each iteration or after a new pv is found.
2531 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2533 std::stringstream s, l;
2536 while (*m != MOVE_NONE)
2539 s << "info depth " << depth / ONE_PLY
2540 << " seldepth " << int(m - pv)
2541 << " multipv " << pvLine + 1
2542 << " score " << value_to_uci(pv_score)
2543 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2544 << " time " << current_search_time()
2545 << " nodes " << pos.nodes_searched()
2546 << " nps " << nps(pos)
2547 << " pv " << l.str();
2549 if (UseLogFile && pvLine == 0)
2551 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2552 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2554 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2560 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2562 SearchStack ss[PLY_MAX_PLUS_2];
2563 MoveStack mlist[MOVES_MAX];
2567 // Initialize search stack
2568 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
2569 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2570 bestMoveChanges = 0;
2573 // Generate all legal moves
2574 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2576 // Add each move to the RootMoveList's vector
2577 for (MoveStack* cur = mlist; cur != last; cur++)
2579 // If we have a searchMoves[] list then verify cur->move
2580 // is in the list before to add it.
2581 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2583 if (searchMoves[0] && *sm != cur->move)
2586 // Find a quick score for the move and add to the list
2587 pos.do_move(cur->move, st);
2590 rm.pv[0] = ss[0].currentMove = cur->move;
2591 rm.pv[1] = MOVE_NONE;
2592 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2595 pos.undo_move(cur->move);