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], 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 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 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 ok_to_use_TT_PV(const TTEntry* tte, Depth depth, Value alpha, Value beta, int ply);
301 bool connected_threat(const Position& pos, Move m, Move threat);
302 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
303 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
304 void update_killers(Move m, Move killers[]);
305 void update_gains(const Position& pos, Move move, Value before, Value after);
306 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last);
308 int current_search_time();
309 std::string value_to_uci(Value v);
310 int nps(const Position& pos);
311 void poll(const Position& pos);
312 void wait_for_stop_or_ponderhit();
314 #if !defined(_MSC_VER)
315 void* init_thread(void* threadID);
317 DWORD WINAPI init_thread(LPVOID threadID);
321 // MovePickerExt is an extended MovePicker used to choose at compile time
322 // the proper move source according to the type of node.
323 template<bool SpNode, bool Root> struct MovePickerExt;
325 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
326 // before to search them.
327 template<> struct MovePickerExt<false, true> : public MovePicker {
329 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
330 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
332 Value score = VALUE_ZERO;
334 // Score root moves using the standard way used in main search, the moves
335 // are scored according to the order in which are returned by MovePicker.
336 // This is the second order score that is used to compare the moves when
337 // the first order pv scores of both moves are equal.
338 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
339 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
340 if (rm->pv[0] == move)
342 rm->non_pv_score = score--;
350 Move get_next_move() {
357 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
360 RootMoveList::iterator rm;
364 // In SpNodes use split point's shared MovePicker object as move source
365 template<> struct MovePickerExt<true, false> : public MovePicker {
367 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
368 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
371 Move get_next_move() { return mp->get_next_move(); }
373 RootMoveList::iterator rm; // Dummy, needed to compile
377 // Default case, create and use a MovePicker object as source
378 template<> struct MovePickerExt<false, false> : public MovePicker {
380 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
381 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
383 RootMoveList::iterator rm; // Dummy, needed to compile
393 /// init_threads(), exit_threads() and nodes_searched() are helpers to
394 /// give accessibility to some TM methods from outside of current file.
396 void init_threads() { ThreadsMgr.init_threads(); }
397 void exit_threads() { ThreadsMgr.exit_threads(); }
400 /// init_search() is called during startup. It initializes various lookup tables
404 int d; // depth (ONE_PLY == 2)
405 int hd; // half depth (ONE_PLY == 1)
408 // Init reductions array
409 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
411 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
412 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
413 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
414 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
417 // Init futility margins array
418 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
419 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
421 // Init futility move count array
422 for (d = 0; d < 32; d++)
423 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
427 /// perft() is our utility to verify move generation is bug free. All the legal
428 /// moves up to given depth are generated and counted and the sum returned.
430 int64_t perft(Position& pos, Depth depth)
432 MoveStack mlist[MOVES_MAX];
437 // Generate all legal moves
438 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
440 // If we are at the last ply we don't need to do and undo
441 // the moves, just to count them.
442 if (depth <= ONE_PLY)
443 return int(last - mlist);
445 // Loop through all legal moves
447 for (MoveStack* cur = mlist; cur != last; cur++)
450 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
451 sum += perft(pos, depth - ONE_PLY);
458 /// think() is the external interface to Stockfish's search, and is called when
459 /// the program receives the UCI 'go' command. It initializes various
460 /// search-related global variables, and calls id_loop(). It returns false
461 /// when a quit command is received during the search.
463 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
464 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
466 // Initialize global search variables
467 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
469 SearchStartTime = get_system_time();
470 ExactMaxTime = maxTime;
473 InfiniteSearch = infinite;
475 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
477 // Look for a book move, only during games, not tests
478 if (UseTimeManagement && Options["OwnBook"].value<bool>())
480 if (Options["Book File"].value<std::string>() != OpeningBook.name())
481 OpeningBook.open(Options["Book File"].value<std::string>());
483 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
484 if (bookMove != MOVE_NONE)
487 wait_for_stop_or_ponderhit();
489 cout << "bestmove " << bookMove << endl;
494 // Read UCI option values
495 TT.set_size(Options["Hash"].value<int>());
496 if (Options["Clear Hash"].value<bool>())
498 Options["Clear Hash"].set_value("false");
502 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
503 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
504 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
505 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
506 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
507 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
508 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
509 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
510 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
511 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
512 MultiPV = Options["MultiPV"].value<int>();
513 UseLogFile = Options["Use Search Log"].value<bool>();
515 read_evaluation_uci_options(pos.side_to_move());
517 // Set the number of active threads
518 ThreadsMgr.read_uci_options();
519 init_eval(ThreadsMgr.active_threads());
521 // Wake up needed threads
522 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
523 ThreadsMgr.wake_sleeping_thread(i);
526 int myTime = time[pos.side_to_move()];
527 int myIncrement = increment[pos.side_to_move()];
528 if (UseTimeManagement)
529 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
531 // Set best NodesBetweenPolls interval to avoid lagging under
532 // heavy time pressure.
534 NodesBetweenPolls = Min(MaxNodes, 30000);
535 else if (myTime && myTime < 1000)
536 NodesBetweenPolls = 1000;
537 else if (myTime && myTime < 5000)
538 NodesBetweenPolls = 5000;
540 NodesBetweenPolls = 30000;
542 // Write search information to log file
545 std::string name = Options["Search Log Filename"].value<std::string>();
546 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
548 LogFile << "Searching: " << pos.to_fen()
549 << "\ninfinite: " << infinite
550 << " ponder: " << ponder
551 << " time: " << myTime
552 << " increment: " << myIncrement
553 << " moves to go: " << movesToGo << endl;
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 << "\nNodes: " << 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: "
574 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
577 // Return from think() with unchanged position
578 pos.undo_move(bestMove);
583 // This makes all the threads to go to sleep
584 ThreadsMgr.set_active_threads(1);
586 // If we are pondering or in infinite search, we shouldn't print the
587 // best move before we are told to do so.
588 if (!StopRequest && (Pondering || InfiniteSearch))
589 wait_for_stop_or_ponderhit();
591 // Could be both MOVE_NONE when searching on a stalemate position
592 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
600 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
601 // with increasing depth until the allocated thinking time has been consumed,
602 // user stops the search, or the maximum search depth is reached.
604 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
606 SearchStack ss[PLY_MAX_PLUS_2];
607 Value bestValues[PLY_MAX_PLUS_2];
608 int bestMoveChanges[PLY_MAX_PLUS_2];
609 int iteration, researchCountFL, researchCountFH, aspirationDelta;
610 Value value, alpha, beta;
612 Move bestMove, easyMove;
614 // Moves to search are verified, scored and sorted
615 Rml.init(pos, searchMoves);
617 // Initialize FIXME move before Rml.init()
620 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
621 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
622 *ponderMove = bestMove = easyMove = MOVE_NONE;
625 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
627 // Handle special case of searching on a mate/stale position
630 cout << "info depth " << iteration << " score "
631 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
637 // Send initial scoring (iteration 1)
638 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
639 << "info depth " << iteration
640 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
642 // Is one move significantly better than others after initial scoring ?
644 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
645 easyMove = Rml[0].pv[0];
647 // Iterative deepening loop
648 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
650 cout << "info depth " << iteration << endl;
652 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
653 depth = (iteration - 1) * ONE_PLY;
655 // Calculate dynamic aspiration window based on previous iterations
656 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
658 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
659 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
661 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
662 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
664 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
665 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
668 // Start with a small aspiration window and, in case of fail high/low,
669 // research with bigger window until not failing high/low anymore.
672 // Search starting from ss+1 to allow calling update_gains()
673 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
675 // Write PV lines to transposition table, in case the relevant entries
676 // have been overwritten during the search.
677 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
678 Rml[i].insert_pv_in_tt(pos);
680 // Value cannot be trusted. Break out immediately!
684 assert(value >= alpha);
686 // In case of failing high/low increase aspiration window and research,
687 // otherwise exit the fail high/low loop.
690 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
693 else if (value <= alpha)
695 AspirationFailLow = true;
696 StopOnPonderhit = false;
698 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
705 // Collect info about search result
706 bestMove = Rml[0].pv[0];
707 bestValues[iteration] = value;
708 bestMoveChanges[iteration] = Rml.bestMoveChanges;
710 // Drop the easy move if differs from the new best move
711 if (bestMove != easyMove)
712 easyMove = MOVE_NONE;
714 if (UseTimeManagement && !StopRequest)
717 bool noMoreTime = false;
719 // Stop search early when the last two iterations returned a mate score
721 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
722 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
725 // Stop search early if one move seems to be much better than the
726 // others or if there is only a single legal move. In this latter
727 // case we search up to Iteration 8 anyway to get a proper score.
729 && easyMove == bestMove
731 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
732 && current_search_time() > TimeMgr.available_time() / 16)
733 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
734 && current_search_time() > TimeMgr.available_time() / 32)))
737 // Add some extra time if the best move has changed during the last two iterations
738 if (iteration > 5 && iteration <= 50)
739 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
741 // Stop search if most of MaxSearchTime is consumed at the end of the
742 // iteration. We probably don't have enough time to search the first
743 // move at the next iteration anyway.
744 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
750 StopOnPonderhit = true;
757 *ponderMove = Rml[0].pv[1];
762 // search<>() is the main search function for both PV and non-PV nodes and for
763 // normal and SplitPoint nodes. When called just after a split point the search
764 // is simpler because we have already probed the hash table, done a null move
765 // search, and searched the first move before splitting, we don't have to repeat
766 // all this work again. We also don't need to store anything to the hash table
767 // here: This is taken care of after we return from the split point.
769 template <NodeType PvNode, bool SpNode, bool Root>
770 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
772 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
773 assert(beta > alpha && beta <= VALUE_INFINITE);
774 assert(PvNode || alpha == beta - 1);
775 assert((Root || ply > 0) && ply < PLY_MAX);
776 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
778 Move movesSearched[MOVES_MAX];
783 Move ttMove, move, excludedMove, threatMove;
786 Value bestValue, value, oldAlpha;
787 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
788 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
789 bool mateThreat = false;
790 int moveCount = 0, playedMoveCount = 0;
791 int threadID = pos.thread();
792 SplitPoint* sp = NULL;
794 refinedValue = bestValue = value = -VALUE_INFINITE;
796 isCheck = pos.is_check();
802 ttMove = excludedMove = MOVE_NONE;
803 threatMove = sp->threatMove;
804 mateThreat = sp->mateThreat;
805 goto split_point_start;
810 // Step 1. Initialize node and poll. Polling can abort search
811 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
812 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
814 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
820 // Step 2. Check for aborted search and immediate draw
822 || ThreadsMgr.cutoff_at_splitpoint(threadID)
824 || ply >= PLY_MAX - 1) && !Root)
827 // Step 3. Mate distance pruning
828 alpha = Max(value_mated_in(ply), alpha);
829 beta = Min(value_mate_in(ply+1), beta);
833 // Step 4. Transposition table lookup
834 // We don't want the score of a partial search to overwrite a previous full search
835 // TT value, so we use a different position key in case of an excluded move exists.
836 excludedMove = ss->excludedMove;
837 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
839 tte = TT.retrieve(posKey);
840 ttMove = tte ? tte->move() : MOVE_NONE;
842 // At PV nodes we check for exact scores within (alha, beta) range, while
843 // at non-PV nodes we check for and return a fail high/low. Biggest advantage
844 // at probing at PV nodes is to have a smooth experience in analysis mode.
845 if (!Root && tte && (PvNode ? ok_to_use_TT_PV(tte, depth, alpha, beta, ply) : ok_to_use_TT(tte, depth, beta, ply)))
848 ss->bestMove = ttMove; // Can be MOVE_NONE
849 return value_from_tt(tte->value(), ply);
852 // Step 5. Evaluate the position statically and
853 // update gain statistics of parent move.
855 ss->eval = ss->evalMargin = VALUE_NONE;
858 assert(tte->static_value() != VALUE_NONE);
860 ss->eval = tte->static_value();
861 ss->evalMargin = tte->static_value_margin();
862 refinedValue = refine_eval(tte, ss->eval, ply);
866 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
867 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
870 // Save gain for the parent non-capture move
871 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
873 // Step 6. Razoring (is omitted in PV nodes)
875 && depth < RazorDepth
877 && refinedValue < beta - razor_margin(depth)
878 && ttMove == MOVE_NONE
879 && !value_is_mate(beta)
880 && !pos.has_pawn_on_7th(pos.side_to_move()))
882 Value rbeta = beta - razor_margin(depth);
883 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
885 // Logically we should return (v + razor_margin(depth)), but
886 // surprisingly this did slightly weaker in tests.
890 // Step 7. Static null move pruning (is omitted in PV nodes)
891 // We're betting that the opponent doesn't have a move that will reduce
892 // the score by more than futility_margin(depth) if we do a null move.
895 && depth < RazorDepth
897 && refinedValue >= beta + futility_margin(depth, 0)
898 && !value_is_mate(beta)
899 && pos.non_pawn_material(pos.side_to_move()))
900 return refinedValue - futility_margin(depth, 0);
902 // Step 8. Null move search with verification search (is omitted in PV nodes)
907 && refinedValue >= beta
908 && !value_is_mate(beta)
909 && pos.non_pawn_material(pos.side_to_move()))
911 ss->currentMove = MOVE_NULL;
913 // Null move dynamic reduction based on depth
914 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
916 // Null move dynamic reduction based on value
917 if (refinedValue - beta > PawnValueMidgame)
920 pos.do_null_move(st);
921 (ss+1)->skipNullMove = true;
922 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
923 (ss+1)->skipNullMove = false;
924 pos.undo_null_move();
926 if (nullValue >= beta)
928 // Do not return unproven mate scores
929 if (nullValue >= value_mate_in(PLY_MAX))
932 if (depth < 6 * ONE_PLY)
935 // Do verification search at high depths
936 ss->skipNullMove = true;
937 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
938 ss->skipNullMove = false;
945 // The null move failed low, which means that we may be faced with
946 // some kind of threat. If the previous move was reduced, check if
947 // the move that refuted the null move was somehow connected to the
948 // move which was reduced. If a connection is found, return a fail
949 // low score (which will cause the reduced move to fail high in the
950 // parent node, which will trigger a re-search with full depth).
951 if (nullValue == value_mated_in(ply + 2))
954 threatMove = (ss+1)->bestMove;
955 if ( depth < ThreatDepth
957 && threatMove != MOVE_NONE
958 && connected_moves(pos, (ss-1)->currentMove, threatMove))
963 // Step 9. Internal iterative deepening
964 if ( depth >= IIDDepth[PvNode]
965 && ttMove == MOVE_NONE
966 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
968 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
970 ss->skipNullMove = true;
971 search<PvNode>(pos, ss, alpha, beta, d, ply);
972 ss->skipNullMove = false;
974 ttMove = ss->bestMove;
975 tte = TT.retrieve(posKey);
978 // Expensive mate threat detection (only for PV nodes)
980 mateThreat = pos.has_mate_threat();
982 split_point_start: // At split points actual search starts from here
984 // Initialize a MovePicker object for the current position
985 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
987 ss->bestMove = MOVE_NONE;
988 futilityBase = ss->eval + ss->evalMargin;
989 singularExtensionNode = !Root
991 && depth >= SingularExtensionDepth[PvNode]
994 && !excludedMove // Do not allow recursive singular extension search
995 && (tte->type() & VALUE_TYPE_LOWER)
996 && tte->depth() >= depth - 3 * ONE_PLY;
999 lock_grab(&(sp->lock));
1000 bestValue = sp->bestValue;
1003 // Step 10. Loop through moves
1004 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1005 while ( bestValue < beta
1006 && (move = mp.get_next_move()) != MOVE_NONE
1007 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1009 assert(move_is_ok(move));
1013 moveCount = ++sp->moveCount;
1014 lock_release(&(sp->lock));
1016 else if (move == excludedMove)
1023 // This is used by time management
1024 FirstRootMove = (moveCount == 1);
1026 // Save the current node count before the move is searched
1027 nodes = pos.nodes_searched();
1029 // If it's time to send nodes info, do it here where we have the
1030 // correct accumulated node counts searched by each thread.
1031 if (SendSearchedNodes)
1033 SendSearchedNodes = false;
1034 cout << "info nodes " << nodes
1035 << " nps " << nps(pos)
1036 << " time " << current_search_time() << endl;
1039 if (current_search_time() >= 1000)
1040 cout << "info currmove " << move
1041 << " currmovenumber " << moveCount << endl;
1044 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1045 moveIsCheck = pos.move_is_check(move, ci);
1046 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1048 // Step 11. Decide the new search depth
1049 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1051 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1052 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1053 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1054 // lower then ttValue minus a margin then we extend ttMove.
1055 if ( singularExtensionNode
1056 && move == tte->move()
1059 Value ttValue = value_from_tt(tte->value(), ply);
1061 if (abs(ttValue) < VALUE_KNOWN_WIN)
1063 Value b = ttValue - SingularExtensionMargin;
1064 ss->excludedMove = move;
1065 ss->skipNullMove = true;
1066 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1067 ss->skipNullMove = false;
1068 ss->excludedMove = MOVE_NONE;
1069 ss->bestMove = MOVE_NONE;
1075 // Update current move (this must be done after singular extension search)
1076 ss->currentMove = move;
1077 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1079 // Step 12. Futility pruning (is omitted in PV nodes)
1081 && !captureOrPromotion
1085 && !move_is_castle(move))
1087 // Move count based pruning
1088 if ( moveCount >= futility_move_count(depth)
1089 && !(threatMove && connected_threat(pos, move, threatMove))
1090 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1093 lock_grab(&(sp->lock));
1098 // Value based pruning
1099 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1100 // but fixing this made program slightly weaker.
1101 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1102 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1103 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1105 if (futilityValueScaled < beta)
1109 lock_grab(&(sp->lock));
1110 if (futilityValueScaled > sp->bestValue)
1111 sp->bestValue = bestValue = futilityValueScaled;
1113 else if (futilityValueScaled > bestValue)
1114 bestValue = futilityValueScaled;
1119 // Prune moves with negative SEE at low depths
1120 if ( predictedDepth < 2 * ONE_PLY
1121 && bestValue > value_mated_in(PLY_MAX)
1122 && pos.see_sign(move) < 0)
1125 lock_grab(&(sp->lock));
1131 // Step 13. Make the move
1132 pos.do_move(move, st, ci, moveIsCheck);
1134 if (!SpNode && !captureOrPromotion)
1135 movesSearched[playedMoveCount++] = move;
1137 // Step extra. pv search (only in PV nodes)
1138 // The first move in list is the expected PV
1141 // Aspiration window is disabled in multi-pv case
1142 if (Root && MultiPV > 1)
1143 alpha = -VALUE_INFINITE;
1145 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1149 // Step 14. Reduced depth search
1150 // If the move fails high will be re-searched at full depth.
1151 bool doFullDepthSearch = true;
1153 if ( depth >= 3 * ONE_PLY
1154 && !captureOrPromotion
1156 && !move_is_castle(move)
1157 && ss->killers[0] != move
1158 && ss->killers[1] != move)
1160 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1161 : reduction<PvNode>(depth, moveCount);
1164 alpha = SpNode ? sp->alpha : alpha;
1165 Depth d = newDepth - ss->reduction;
1166 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1168 doFullDepthSearch = (value > alpha);
1170 ss->reduction = DEPTH_ZERO; // Restore original reduction
1173 // Step 15. Full depth search
1174 if (doFullDepthSearch)
1176 alpha = SpNode ? sp->alpha : alpha;
1177 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1179 // Step extra. pv search (only in PV nodes)
1180 // Search only for possible new PV nodes, if instead value >= beta then
1181 // parent node fails low with value <= alpha and tries another move.
1182 if (PvNode && value > alpha && (Root || value < beta))
1183 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1187 // Step 16. Undo move
1188 pos.undo_move(move);
1190 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1192 // Step 17. Check for new best move
1195 lock_grab(&(sp->lock));
1196 bestValue = sp->bestValue;
1200 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1205 sp->bestValue = value;
1209 if (PvNode && value < beta) // We want always alpha < beta
1217 sp->betaCutoff = true;
1219 if (value == value_mate_in(ply + 1))
1220 ss->mateKiller = move;
1222 ss->bestMove = move;
1225 sp->parentSstack->bestMove = move;
1231 // To avoid to exit with bestValue == -VALUE_INFINITE
1232 if (value > bestValue)
1235 // Finished searching the move. If StopRequest is true, the search
1236 // was aborted because the user interrupted the search or because we
1237 // ran out of time. In this case, the return value of the search cannot
1238 // be trusted, and we break out of the loop without updating the best
1243 // Remember searched nodes counts for this move
1244 mp.rm->nodes += pos.nodes_searched() - nodes;
1246 // Step 17. Check for new best move
1247 if (!isPvMove && value <= alpha)
1248 mp.rm->pv_score = -VALUE_INFINITE;
1251 // PV move or new best move!
1254 ss->bestMove = move;
1255 mp.rm->pv_score = value;
1256 mp.rm->extract_pv_from_tt(pos);
1258 // We record how often the best move has been changed in each
1259 // iteration. This information is used for time managment: When
1260 // the best move changes frequently, we allocate some more time.
1261 if (!isPvMove && MultiPV == 1)
1262 Rml.bestMoveChanges++;
1264 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1265 // requires we send all the PV lines properly sorted.
1266 Rml.sort_multipv(moveCount);
1268 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1269 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1271 // Update alpha. In multi-pv we don't use aspiration window, so
1272 // set alpha equal to minimum score among the PV lines.
1274 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1275 else if (value > alpha)
1278 } // PV move or new best move
1281 // Step 18. Check for split
1284 && depth >= ThreadsMgr.min_split_depth()
1285 && ThreadsMgr.active_threads() > 1
1287 && ThreadsMgr.available_thread_exists(threadID)
1289 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1290 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1291 threatMove, mateThreat, moveCount, &mp, PvNode);
1294 // Step 19. Check for mate and stalemate
1295 // All legal moves have been searched and if there are
1296 // no legal moves, it must be mate or stalemate.
1297 // If one move was excluded return fail low score.
1298 if (!SpNode && !moveCount)
1299 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1301 // Step 20. Update tables
1302 // If the search is not aborted, update the transposition table,
1303 // history counters, and killer moves.
1304 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1306 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1307 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1308 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1310 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1312 // Update killers and history only for non capture moves that fails high
1313 if ( bestValue >= beta
1314 && !pos.move_is_capture_or_promotion(move))
1316 update_history(pos, move, depth, movesSearched, playedMoveCount);
1317 update_killers(move, ss->killers);
1323 // Here we have the lock still grabbed
1324 sp->slaves[threadID] = 0;
1325 sp->nodes += pos.nodes_searched();
1326 lock_release(&(sp->lock));
1329 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1334 // qsearch() is the quiescence search function, which is called by the main
1335 // search function when the remaining depth is zero (or, to be more precise,
1336 // less than ONE_PLY).
1338 template <NodeType PvNode>
1339 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1341 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1342 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1343 assert(PvNode || alpha == beta - 1);
1345 assert(ply > 0 && ply < PLY_MAX);
1346 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1350 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1351 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1354 Value oldAlpha = alpha;
1356 ss->bestMove = ss->currentMove = MOVE_NONE;
1358 // Check for an instant draw or maximum ply reached
1359 if (pos.is_draw() || ply >= PLY_MAX - 1)
1362 // Decide whether or not to include checks, this fixes also the type of
1363 // TT entry depth that we are going to use. Note that in qsearch we use
1364 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1365 isCheck = pos.is_check();
1366 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1368 // Transposition table lookup. At PV nodes, we don't use the TT for
1369 // pruning, but only for move ordering.
1370 tte = TT.retrieve(pos.get_key());
1371 ttMove = (tte ? tte->move() : MOVE_NONE);
1373 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1375 ss->bestMove = ttMove; // Can be MOVE_NONE
1376 return value_from_tt(tte->value(), ply);
1379 // Evaluate the position statically
1382 bestValue = futilityBase = -VALUE_INFINITE;
1383 ss->eval = evalMargin = VALUE_NONE;
1384 enoughMaterial = false;
1390 assert(tte->static_value() != VALUE_NONE);
1392 evalMargin = tte->static_value_margin();
1393 ss->eval = bestValue = tte->static_value();
1396 ss->eval = bestValue = evaluate(pos, evalMargin);
1398 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1400 // Stand pat. Return immediately if static value is at least beta
1401 if (bestValue >= beta)
1404 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1409 if (PvNode && bestValue > alpha)
1412 // Futility pruning parameters, not needed when in check
1413 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1414 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1417 // Initialize a MovePicker object for the current position, and prepare
1418 // to search the moves. Because the depth is <= 0 here, only captures,
1419 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1421 MovePicker mp(pos, ttMove, depth, H);
1424 // Loop through the moves until no moves remain or a beta cutoff occurs
1425 while ( alpha < beta
1426 && (move = mp.get_next_move()) != MOVE_NONE)
1428 assert(move_is_ok(move));
1430 moveIsCheck = pos.move_is_check(move, ci);
1438 && !move_is_promotion(move)
1439 && !pos.move_is_passed_pawn_push(move))
1441 futilityValue = futilityBase
1442 + pos.endgame_value_of_piece_on(move_to(move))
1443 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1445 if (futilityValue < alpha)
1447 if (futilityValue > bestValue)
1448 bestValue = futilityValue;
1453 // Detect non-capture evasions that are candidate to be pruned
1454 evasionPrunable = isCheck
1455 && bestValue > value_mated_in(PLY_MAX)
1456 && !pos.move_is_capture(move)
1457 && !pos.can_castle(pos.side_to_move());
1459 // Don't search moves with negative SEE values
1461 && (!isCheck || evasionPrunable)
1463 && !move_is_promotion(move)
1464 && pos.see_sign(move) < 0)
1467 // Don't search useless checks
1472 && !pos.move_is_capture_or_promotion(move)
1473 && ss->eval + PawnValueMidgame / 4 < beta
1474 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1476 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1477 bestValue = ss->eval + PawnValueMidgame / 4;
1482 // Update current move
1483 ss->currentMove = move;
1485 // Make and search the move
1486 pos.do_move(move, st, ci, moveIsCheck);
1487 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1488 pos.undo_move(move);
1490 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1493 if (value > bestValue)
1499 ss->bestMove = move;
1504 // All legal moves have been searched. A special case: If we're in check
1505 // and no legal moves were found, it is checkmate.
1506 if (isCheck && bestValue == -VALUE_INFINITE)
1507 return value_mated_in(ply);
1509 // Update transposition table
1510 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1511 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1513 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1519 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1520 // it is used in RootMoveList to get an initial scoring.
1521 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1523 SearchStack ss[PLY_MAX_PLUS_2];
1526 memset(ss, 0, 4 * sizeof(SearchStack));
1527 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1529 for (MoveStack* cur = mlist; cur != last; cur++)
1531 ss[0].currentMove = cur->move;
1532 pos.do_move(cur->move, st);
1533 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1534 pos.undo_move(cur->move);
1539 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1540 // bestValue is updated only when returning false because in that case move
1543 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1545 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1546 Square from, to, ksq, victimSq;
1549 Value futilityValue, bv = *bestValue;
1551 from = move_from(move);
1553 them = opposite_color(pos.side_to_move());
1554 ksq = pos.king_square(them);
1555 kingAtt = pos.attacks_from<KING>(ksq);
1556 pc = pos.piece_on(from);
1558 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1559 oldAtt = pos.attacks_from(pc, from, occ);
1560 newAtt = pos.attacks_from(pc, to, occ);
1562 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1563 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1565 if (!(b && (b & (b - 1))))
1568 // Rule 2. Queen contact check is very dangerous
1569 if ( type_of_piece(pc) == QUEEN
1570 && bit_is_set(kingAtt, to))
1573 // Rule 3. Creating new double threats with checks
1574 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1578 victimSq = pop_1st_bit(&b);
1579 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1581 // Note that here we generate illegal "double move"!
1582 if ( futilityValue >= beta
1583 && pos.see_sign(make_move(from, victimSq)) >= 0)
1586 if (futilityValue > bv)
1590 // Update bestValue only if check is not dangerous (because we will prune the move)
1596 // connected_moves() tests whether two moves are 'connected' in the sense
1597 // that the first move somehow made the second move possible (for instance
1598 // if the moving piece is the same in both moves). The first move is assumed
1599 // to be the move that was made to reach the current position, while the
1600 // second move is assumed to be a move from the current position.
1602 bool connected_moves(const Position& pos, Move m1, Move m2) {
1604 Square f1, t1, f2, t2;
1607 assert(m1 && move_is_ok(m1));
1608 assert(m2 && move_is_ok(m2));
1610 // Case 1: The moving piece is the same in both moves
1616 // Case 2: The destination square for m2 was vacated by m1
1622 // Case 3: Moving through the vacated square
1623 if ( piece_is_slider(pos.piece_on(f2))
1624 && bit_is_set(squares_between(f2, t2), f1))
1627 // Case 4: The destination square for m2 is defended by the moving piece in m1
1628 p = pos.piece_on(t1);
1629 if (bit_is_set(pos.attacks_from(p, t1), t2))
1632 // Case 5: Discovered check, checking piece is the piece moved in m1
1633 if ( piece_is_slider(p)
1634 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1635 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1637 // discovered_check_candidates() works also if the Position's side to
1638 // move is the opposite of the checking piece.
1639 Color them = opposite_color(pos.side_to_move());
1640 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1642 if (bit_is_set(dcCandidates, f2))
1649 // value_is_mate() checks if the given value is a mate one eventually
1650 // compensated for the ply.
1652 bool value_is_mate(Value value) {
1654 assert(abs(value) <= VALUE_INFINITE);
1656 return value <= value_mated_in(PLY_MAX)
1657 || value >= value_mate_in(PLY_MAX);
1661 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1662 // "plies to mate from the current ply". Non-mate scores are unchanged.
1663 // The function is called before storing a value to the transposition table.
1665 Value value_to_tt(Value v, int ply) {
1667 if (v >= value_mate_in(PLY_MAX))
1670 if (v <= value_mated_in(PLY_MAX))
1677 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1678 // the transposition table to a mate score corrected for the current ply.
1680 Value value_from_tt(Value v, int ply) {
1682 if (v >= value_mate_in(PLY_MAX))
1685 if (v <= value_mated_in(PLY_MAX))
1692 // extension() decides whether a move should be searched with normal depth,
1693 // or with extended depth. Certain classes of moves (checking moves, in
1694 // particular) are searched with bigger depth than ordinary moves and in
1695 // any case are marked as 'dangerous'. Note that also if a move is not
1696 // extended, as example because the corresponding UCI option is set to zero,
1697 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1698 template <NodeType PvNode>
1699 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1700 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1702 assert(m != MOVE_NONE);
1704 Depth result = DEPTH_ZERO;
1705 *dangerous = moveIsCheck | mateThreat;
1709 if (moveIsCheck && pos.see_sign(m) >= 0)
1710 result += CheckExtension[PvNode];
1713 result += MateThreatExtension[PvNode];
1716 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1718 Color c = pos.side_to_move();
1719 if (relative_rank(c, move_to(m)) == RANK_7)
1721 result += PawnPushTo7thExtension[PvNode];
1724 if (pos.pawn_is_passed(c, move_to(m)))
1726 result += PassedPawnExtension[PvNode];
1731 if ( captureOrPromotion
1732 && pos.type_of_piece_on(move_to(m)) != PAWN
1733 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1734 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1735 && !move_is_promotion(m)
1738 result += PawnEndgameExtension[PvNode];
1743 && captureOrPromotion
1744 && pos.type_of_piece_on(move_to(m)) != PAWN
1745 && pos.see_sign(m) >= 0)
1747 result += ONE_PLY / 2;
1751 return Min(result, ONE_PLY);
1755 // connected_threat() tests whether it is safe to forward prune a move or if
1756 // is somehow coonected to the threat move returned by null search.
1758 bool connected_threat(const Position& pos, Move m, Move threat) {
1760 assert(move_is_ok(m));
1761 assert(threat && move_is_ok(threat));
1762 assert(!pos.move_is_check(m));
1763 assert(!pos.move_is_capture_or_promotion(m));
1764 assert(!pos.move_is_passed_pawn_push(m));
1766 Square mfrom, mto, tfrom, tto;
1768 mfrom = move_from(m);
1770 tfrom = move_from(threat);
1771 tto = move_to(threat);
1773 // Case 1: Don't prune moves which move the threatened piece
1777 // Case 2: If the threatened piece has value less than or equal to the
1778 // value of the threatening piece, don't prune move which defend it.
1779 if ( pos.move_is_capture(threat)
1780 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1781 || pos.type_of_piece_on(tfrom) == KING)
1782 && pos.move_attacks_square(m, tto))
1785 // Case 3: If the moving piece in the threatened move is a slider, don't
1786 // prune safe moves which block its ray.
1787 if ( piece_is_slider(pos.piece_on(tfrom))
1788 && bit_is_set(squares_between(tfrom, tto), mto)
1789 && pos.see_sign(m) >= 0)
1796 // ok_to_use_TT() returns true if a transposition table score
1797 // can be used at a given point in search. There are two versions
1798 // one to be used in non-PV nodes and one in PV nodes where we look
1799 // for an exact score that falls between (alha, beta) boundaries.
1801 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1803 Value v = value_from_tt(tte->value(), ply);
1805 return ( tte->depth() >= depth
1806 || v >= Max(value_mate_in(PLY_MAX), beta)
1807 || v < Min(value_mated_in(PLY_MAX), beta))
1809 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1810 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1813 bool ok_to_use_TT_PV(const TTEntry* tte, Depth depth, Value alpha, Value beta, int ply) {
1815 Value v = value_from_tt(tte->value(), ply);
1817 return tte->depth() >= depth
1818 && tte->type() == VALUE_TYPE_EXACT
1819 && tte->move() != MOVE_NONE
1825 // refine_eval() returns the transposition table score if
1826 // possible otherwise falls back on static position evaluation.
1828 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1832 Value v = value_from_tt(tte->value(), ply);
1834 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1835 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1842 // update_history() registers a good move that produced a beta-cutoff
1843 // in history and marks as failures all the other moves of that ply.
1845 void update_history(const Position& pos, Move move, Depth depth,
1846 Move movesSearched[], int moveCount) {
1848 Value bonus = Value(int(depth) * int(depth));
1850 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1852 for (int i = 0; i < moveCount - 1; i++)
1854 m = movesSearched[i];
1858 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1863 // update_killers() add a good move that produced a beta-cutoff
1864 // among the killer moves of that ply.
1866 void update_killers(Move m, Move killers[]) {
1868 if (m != killers[0])
1870 killers[1] = killers[0];
1876 // update_gains() updates the gains table of a non-capture move given
1877 // the static position evaluation before and after the move.
1879 void update_gains(const Position& pos, Move m, Value before, Value after) {
1882 && before != VALUE_NONE
1883 && after != VALUE_NONE
1884 && pos.captured_piece_type() == PIECE_TYPE_NONE
1885 && !move_is_special(m))
1886 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1890 // value_to_uci() converts a value to a string suitable for use with the UCI
1891 // protocol specifications:
1893 // cp <x> The score from the engine's point of view in centipawns.
1894 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1895 // use negative values for y.
1897 std::string value_to_uci(Value v) {
1899 std::stringstream s;
1901 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1902 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1904 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1910 // current_search_time() returns the number of milliseconds which have passed
1911 // since the beginning of the current search.
1913 int current_search_time() {
1915 return get_system_time() - SearchStartTime;
1919 // nps() computes the current nodes/second count
1921 int nps(const Position& pos) {
1923 int t = current_search_time();
1924 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1928 // poll() performs two different functions: It polls for user input, and it
1929 // looks at the time consumed so far and decides if it's time to abort the
1932 void poll(const Position& pos) {
1934 static int lastInfoTime;
1935 int t = current_search_time();
1938 if (input_available())
1940 // We are line oriented, don't read single chars
1941 std::string command;
1943 if (!std::getline(std::cin, command))
1946 if (command == "quit")
1948 // Quit the program as soon as possible
1950 QuitRequest = StopRequest = true;
1953 else if (command == "stop")
1955 // Stop calculating as soon as possible, but still send the "bestmove"
1956 // and possibly the "ponder" token when finishing the search.
1960 else if (command == "ponderhit")
1962 // The opponent has played the expected move. GUI sends "ponderhit" if
1963 // we were told to ponder on the same move the opponent has played. We
1964 // should continue searching but switching from pondering to normal search.
1967 if (StopOnPonderhit)
1972 // Print search information
1976 else if (lastInfoTime > t)
1977 // HACK: Must be a new search where we searched less than
1978 // NodesBetweenPolls nodes during the first second of search.
1981 else if (t - lastInfoTime >= 1000)
1988 if (dbg_show_hit_rate)
1989 dbg_print_hit_rate();
1991 // Send info on searched nodes as soon as we return to root
1992 SendSearchedNodes = true;
1995 // Should we stop the search?
1999 bool stillAtFirstMove = FirstRootMove
2000 && !AspirationFailLow
2001 && t > TimeMgr.available_time();
2003 bool noMoreTime = t > TimeMgr.maximum_time()
2004 || stillAtFirstMove;
2006 if ( (UseTimeManagement && noMoreTime)
2007 || (ExactMaxTime && t >= ExactMaxTime)
2008 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2013 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2014 // while the program is pondering. The point is to work around a wrinkle in
2015 // the UCI protocol: When pondering, the engine is not allowed to give a
2016 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2017 // We simply wait here until one of these commands is sent, and return,
2018 // after which the bestmove and pondermove will be printed.
2020 void wait_for_stop_or_ponderhit() {
2022 std::string command;
2026 // Wait for a command from stdin
2027 if (!std::getline(std::cin, command))
2030 if (command == "quit")
2035 else if (command == "ponderhit" || command == "stop")
2041 // init_thread() is the function which is called when a new thread is
2042 // launched. It simply calls the idle_loop() function with the supplied
2043 // threadID. There are two versions of this function; one for POSIX
2044 // threads and one for Windows threads.
2046 #if !defined(_MSC_VER)
2048 void* init_thread(void* threadID) {
2050 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2056 DWORD WINAPI init_thread(LPVOID threadID) {
2058 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2065 /// The ThreadsManager class
2068 // read_uci_options() updates number of active threads and other internal
2069 // parameters according to the UCI options values. It is called before
2070 // to start a new search.
2072 void ThreadsManager::read_uci_options() {
2074 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2075 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2076 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2077 activeThreads = Options["Threads"].value<int>();
2081 // idle_loop() is where the threads are parked when they have no work to do.
2082 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2083 // object for which the current thread is the master.
2085 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2087 assert(threadID >= 0 && threadID < MAX_THREADS);
2090 bool allFinished = false;
2094 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2095 // master should exit as last one.
2096 if (allThreadsShouldExit)
2099 threads[threadID].state = THREAD_TERMINATED;
2103 // If we are not thinking, wait for a condition to be signaled
2104 // instead of wasting CPU time polling for work.
2105 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2106 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2108 assert(!sp || useSleepingThreads);
2109 assert(threadID != 0 || useSleepingThreads);
2111 if (threads[threadID].state == THREAD_INITIALIZING)
2112 threads[threadID].state = THREAD_AVAILABLE;
2114 // Grab the lock to avoid races with wake_sleeping_thread()
2115 lock_grab(&sleepLock[threadID]);
2117 // If we are master and all slaves have finished do not go to sleep
2118 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2119 allFinished = (i == activeThreads);
2121 if (allFinished || allThreadsShouldExit)
2123 lock_release(&sleepLock[threadID]);
2127 // Do sleep here after retesting sleep conditions
2128 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2129 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2131 lock_release(&sleepLock[threadID]);
2134 // If this thread has been assigned work, launch a search
2135 if (threads[threadID].state == THREAD_WORKISWAITING)
2137 assert(!allThreadsShouldExit);
2139 threads[threadID].state = THREAD_SEARCHING;
2141 // Here we call search() with SplitPoint template parameter set to true
2142 SplitPoint* tsp = threads[threadID].splitPoint;
2143 Position pos(*tsp->pos, threadID);
2144 SearchStack* ss = tsp->sstack[threadID] + 1;
2148 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2150 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2152 assert(threads[threadID].state == THREAD_SEARCHING);
2154 threads[threadID].state = THREAD_AVAILABLE;
2156 // Wake up master thread so to allow it to return from the idle loop in
2157 // case we are the last slave of the split point.
2158 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2159 wake_sleeping_thread(tsp->master);
2162 // If this thread is the master of a split point and all slaves have
2163 // finished their work at this split point, return from the idle loop.
2164 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2165 allFinished = (i == activeThreads);
2169 // Because sp->slaves[] is reset under lock protection,
2170 // be sure sp->lock has been released before to return.
2171 lock_grab(&(sp->lock));
2172 lock_release(&(sp->lock));
2174 // In helpful master concept a master can help only a sub-tree, and
2175 // because here is all finished is not possible master is booked.
2176 assert(threads[threadID].state == THREAD_AVAILABLE);
2178 threads[threadID].state = THREAD_SEARCHING;
2185 // init_threads() is called during startup. It launches all helper threads,
2186 // and initializes the split point stack and the global locks and condition
2189 void ThreadsManager::init_threads() {
2191 int i, arg[MAX_THREADS];
2194 // Initialize global locks
2197 for (i = 0; i < MAX_THREADS; i++)
2199 lock_init(&sleepLock[i]);
2200 cond_init(&sleepCond[i]);
2203 // Initialize splitPoints[] locks
2204 for (i = 0; i < MAX_THREADS; i++)
2205 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2206 lock_init(&(threads[i].splitPoints[j].lock));
2208 // Will be set just before program exits to properly end the threads
2209 allThreadsShouldExit = false;
2211 // Threads will be put all threads to sleep as soon as created
2214 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2215 threads[0].state = THREAD_SEARCHING;
2216 for (i = 1; i < MAX_THREADS; i++)
2217 threads[i].state = THREAD_INITIALIZING;
2219 // Launch the helper threads
2220 for (i = 1; i < MAX_THREADS; i++)
2224 #if !defined(_MSC_VER)
2225 pthread_t pthread[1];
2226 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2227 pthread_detach(pthread[0]);
2229 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2233 cout << "Failed to create thread number " << i << endl;
2237 // Wait until the thread has finished launching and is gone to sleep
2238 while (threads[i].state == THREAD_INITIALIZING) {}
2243 // exit_threads() is called when the program exits. It makes all the
2244 // helper threads exit cleanly.
2246 void ThreadsManager::exit_threads() {
2248 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2250 // Wake up all the threads and waits for termination
2251 for (int i = 1; i < MAX_THREADS; i++)
2253 wake_sleeping_thread(i);
2254 while (threads[i].state != THREAD_TERMINATED) {}
2257 // Now we can safely destroy the locks
2258 for (int i = 0; i < MAX_THREADS; i++)
2259 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2260 lock_destroy(&(threads[i].splitPoints[j].lock));
2262 lock_destroy(&mpLock);
2264 // Now we can safely destroy the wait conditions
2265 for (int i = 0; i < MAX_THREADS; i++)
2267 lock_destroy(&sleepLock[i]);
2268 cond_destroy(&sleepCond[i]);
2273 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2274 // the thread's currently active split point, or in some ancestor of
2275 // the current split point.
2277 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2279 assert(threadID >= 0 && threadID < activeThreads);
2281 SplitPoint* sp = threads[threadID].splitPoint;
2283 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2288 // thread_is_available() checks whether the thread with threadID "slave" is
2289 // available to help the thread with threadID "master" at a split point. An
2290 // obvious requirement is that "slave" must be idle. With more than two
2291 // threads, this is not by itself sufficient: If "slave" is the master of
2292 // some active split point, it is only available as a slave to the other
2293 // threads which are busy searching the split point at the top of "slave"'s
2294 // split point stack (the "helpful master concept" in YBWC terminology).
2296 bool ThreadsManager::thread_is_available(int slave, int master) const {
2298 assert(slave >= 0 && slave < activeThreads);
2299 assert(master >= 0 && master < activeThreads);
2300 assert(activeThreads > 1);
2302 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2305 // Make a local copy to be sure doesn't change under our feet
2306 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2308 // No active split points means that the thread is available as
2309 // a slave for any other thread.
2310 if (localActiveSplitPoints == 0 || activeThreads == 2)
2313 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2314 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2315 // could have been set to 0 by another thread leading to an out of bound access.
2316 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2323 // available_thread_exists() tries to find an idle thread which is available as
2324 // a slave for the thread with threadID "master".
2326 bool ThreadsManager::available_thread_exists(int master) const {
2328 assert(master >= 0 && master < activeThreads);
2329 assert(activeThreads > 1);
2331 for (int i = 0; i < activeThreads; i++)
2332 if (thread_is_available(i, master))
2339 // split() does the actual work of distributing the work at a node between
2340 // several available threads. If it does not succeed in splitting the
2341 // node (because no idle threads are available, or because we have no unused
2342 // split point objects), the function immediately returns. If splitting is
2343 // possible, a SplitPoint object is initialized with all the data that must be
2344 // copied to the helper threads and we tell our helper threads that they have
2345 // been assigned work. This will cause them to instantly leave their idle loops and
2346 // call search().When all threads have returned from search() then split() returns.
2348 template <bool Fake>
2349 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2350 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2351 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2352 assert(pos.is_ok());
2353 assert(ply > 0 && ply < PLY_MAX);
2354 assert(*bestValue >= -VALUE_INFINITE);
2355 assert(*bestValue <= *alpha);
2356 assert(*alpha < beta);
2357 assert(beta <= VALUE_INFINITE);
2358 assert(depth > DEPTH_ZERO);
2359 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2360 assert(activeThreads > 1);
2362 int i, master = pos.thread();
2363 Thread& masterThread = threads[master];
2367 // If no other thread is available to help us, or if we have too many
2368 // active split points, don't split.
2369 if ( !available_thread_exists(master)
2370 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2372 lock_release(&mpLock);
2376 // Pick the next available split point object from the split point stack
2377 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2379 // Initialize the split point object
2380 splitPoint.parent = masterThread.splitPoint;
2381 splitPoint.master = master;
2382 splitPoint.betaCutoff = false;
2383 splitPoint.ply = ply;
2384 splitPoint.depth = depth;
2385 splitPoint.threatMove = threatMove;
2386 splitPoint.mateThreat = mateThreat;
2387 splitPoint.alpha = *alpha;
2388 splitPoint.beta = beta;
2389 splitPoint.pvNode = pvNode;
2390 splitPoint.bestValue = *bestValue;
2392 splitPoint.moveCount = moveCount;
2393 splitPoint.pos = &pos;
2394 splitPoint.nodes = 0;
2395 splitPoint.parentSstack = ss;
2396 for (i = 0; i < activeThreads; i++)
2397 splitPoint.slaves[i] = 0;
2399 masterThread.splitPoint = &splitPoint;
2401 // If we are here it means we are not available
2402 assert(masterThread.state != THREAD_AVAILABLE);
2404 int workersCnt = 1; // At least the master is included
2406 // Allocate available threads setting state to THREAD_BOOKED
2407 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2408 if (thread_is_available(i, master))
2410 threads[i].state = THREAD_BOOKED;
2411 threads[i].splitPoint = &splitPoint;
2412 splitPoint.slaves[i] = 1;
2416 assert(Fake || workersCnt > 1);
2418 // We can release the lock because slave threads are already booked and master is not available
2419 lock_release(&mpLock);
2421 // Tell the threads that they have work to do. This will make them leave
2422 // their idle loop. But before copy search stack tail for each thread.
2423 for (i = 0; i < activeThreads; i++)
2424 if (i == master || splitPoint.slaves[i])
2426 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2428 assert(i == master || threads[i].state == THREAD_BOOKED);
2430 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2432 if (useSleepingThreads && i != master)
2433 wake_sleeping_thread(i);
2436 // Everything is set up. The master thread enters the idle loop, from
2437 // which it will instantly launch a search, because its state is
2438 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2439 // idle loop, which means that the main thread will return from the idle
2440 // loop when all threads have finished their work at this split point.
2441 idle_loop(master, &splitPoint);
2443 // We have returned from the idle loop, which means that all threads are
2444 // finished. Update alpha and bestValue, and return.
2447 *alpha = splitPoint.alpha;
2448 *bestValue = splitPoint.bestValue;
2449 masterThread.activeSplitPoints--;
2450 masterThread.splitPoint = splitPoint.parent;
2451 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2453 lock_release(&mpLock);
2457 // wake_sleeping_thread() wakes up the thread with the given threadID
2458 // when it is time to start a new search.
2460 void ThreadsManager::wake_sleeping_thread(int threadID) {
2462 lock_grab(&sleepLock[threadID]);
2463 cond_signal(&sleepCond[threadID]);
2464 lock_release(&sleepLock[threadID]);
2468 /// RootMove and RootMoveList method's definitions
2470 RootMove::RootMove() {
2473 pv_score = non_pv_score = -VALUE_INFINITE;
2477 RootMove& RootMove::operator=(const RootMove& rm) {
2479 const Move* src = rm.pv;
2482 // Avoid a costly full rm.pv[] copy
2483 do *dst++ = *src; while (*src++ != MOVE_NONE);
2486 pv_score = rm.pv_score;
2487 non_pv_score = rm.non_pv_score;
2491 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2492 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2493 // allow to always have a ponder move even when we fail high at root and also a
2494 // long PV to print that is important for position analysis.
2496 void RootMove::extract_pv_from_tt(Position& pos) {
2498 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2502 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2504 pos.do_move(pv[0], *st++);
2506 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2507 && tte->move() != MOVE_NONE
2508 && move_is_legal(pos, tte->move())
2510 && (!pos.is_draw() || ply < 2))
2512 pv[ply] = tte->move();
2513 pos.do_move(pv[ply++], *st++);
2515 pv[ply] = MOVE_NONE;
2517 do pos.undo_move(pv[--ply]); while (ply);
2520 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2521 // the PV back into the TT. This makes sure the old PV moves are searched
2522 // first, even if the old TT entries have been overwritten.
2524 void RootMove::insert_pv_in_tt(Position& pos) {
2526 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2529 Value v, m = VALUE_NONE;
2532 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2536 tte = TT.retrieve(k);
2538 // Don't overwrite exsisting correct entries
2539 if (!tte || tte->move() != pv[ply])
2541 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2542 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2544 pos.do_move(pv[ply], *st++);
2546 } while (pv[++ply] != MOVE_NONE);
2548 do pos.undo_move(pv[--ply]); while (ply);
2551 // pv_info_to_uci() returns a string with information on the current PV line
2552 // formatted according to UCI specification and eventually writes the info
2553 // to a log file. It is called at each iteration or after a new pv is found.
2555 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2557 std::stringstream s, l;
2560 while (*m != MOVE_NONE)
2563 s << "info depth " << depth / ONE_PLY
2564 << " seldepth " << int(m - pv)
2565 << " multipv " << pvLine + 1
2566 << " score " << value_to_uci(pv_score)
2567 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2568 << " time " << current_search_time()
2569 << " nodes " << pos.nodes_searched()
2570 << " nps " << nps(pos)
2571 << " pv " << l.str();
2573 if (UseLogFile && pvLine == 0)
2575 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2576 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2578 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2584 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2586 MoveStack mlist[MOVES_MAX];
2590 bestMoveChanges = 0;
2592 // Generate all legal moves and score them
2593 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2594 qsearch_scoring(pos, mlist, last);
2596 // Add each move to the RootMoveList's vector
2597 for (MoveStack* cur = mlist; cur != last; cur++)
2599 // If we have a searchMoves[] list then verify cur->move
2600 // is in the list before to add it.
2601 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2603 if (searchMoves[0] && *sm != cur->move)
2607 rm.pv[0] = cur->move;
2608 rm.pv[1] = MOVE_NONE;
2609 rm.pv_score = Value(cur->score);