2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
45 #include "ucioption.h"
51 //// Local definitions
57 enum NodeType { NonPV, PV };
59 // Set to true to force running with one thread.
60 // Used for debugging SMP code.
61 const bool FakeSplit = false;
63 // Fast lookup table of sliding pieces indexed by Piece
64 const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
65 inline bool piece_is_slider(Piece p) { return Slidings[p]; }
67 // ThreadsManager class is used to handle all the threads related stuff in search,
68 // init, starting, parking and, the most important, launching a slave thread at a
69 // split point are what this class does. All the access to shared thread data is
70 // done through this class, so that we avoid using global variables instead.
72 class ThreadsManager {
73 /* As long as the single ThreadsManager object is defined as a global we don't
74 need to explicitly initialize to zero its data members because variables with
75 static storage duration are automatically set to zero before enter main()
81 int min_split_depth() const { return minimumSplitDepth; }
82 int active_threads() const { return activeThreads; }
83 void set_active_threads(int cnt) { activeThreads = cnt; }
85 void read_uci_options();
86 bool available_thread_exists(int master) const;
87 bool thread_is_available(int slave, int master) const;
88 bool cutoff_at_splitpoint(int threadID) const;
89 void wake_sleeping_thread(int threadID);
90 void idle_loop(int threadID, SplitPoint* sp);
93 void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
94 Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
97 Depth minimumSplitDepth;
98 int maxThreadsPerSplitPoint;
99 bool useSleepingThreads;
101 volatile bool allThreadsShouldExit;
102 Thread threads[MAX_THREADS];
103 Lock mpLock, sleepLock[MAX_THREADS];
104 WaitCondition sleepCond[MAX_THREADS];
108 // RootMove struct is used for moves at the root at the tree. For each root
109 // move, we store two scores, a node count, and a PV (really a refutation
110 // in the case of moves which fail low). Value pv_score is normally set at
111 // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
112 // according to the order in which moves are returned by MovePicker.
117 RootMove(const RootMove& rm) { *this = rm; }
118 RootMove& operator=(const RootMove& rm);
120 // RootMove::operator<() is the comparison function used when
121 // sorting the moves. A move m1 is considered to be better
122 // than a move m2 if it has an higher pv_score, or if it has
123 // equal pv_score but m1 has the higher non_pv_score. In this
124 // way we are guaranteed that PV moves are always sorted as first.
125 bool operator<(const RootMove& m) const {
126 return pv_score != m.pv_score ? pv_score < m.pv_score
127 : non_pv_score < m.non_pv_score;
130 void extract_pv_from_tt(Position& pos);
131 void insert_pv_in_tt(Position& pos);
132 std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine);
137 Move pv[PLY_MAX_PLUS_2];
141 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
142 // with an handful of methods above the standard ones.
144 struct RootMoveList : public std::vector<RootMove> {
146 typedef std::vector<RootMove> Base;
148 void init(Position& pos, Move searchMoves[]);
149 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
150 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
156 // When formatting a move for std::cout we must know if we are in Chess960
157 // or not. To keep using the handy operator<<() on the move the trick is to
158 // embed this flag in the stream itself. Function-like named enum set960 is
159 // used as a custom manipulator and the stream internal general-purpose array,
160 // accessed through ios_base::iword(), is used to pass the flag to the move's
161 // operator<<() that will use it to properly format castling moves.
164 std::ostream& operator<< (std::ostream& os, const set960& f) {
166 os.iword(0) = int(f);
171 // Overload operator << for moves to make it easier to print moves in
172 // coordinate notation compatible with UCI protocol.
173 std::ostream& operator<<(std::ostream& os, Move m) {
175 bool chess960 = (os.iword(0) != 0); // See set960()
176 return os << move_to_uci(m, chess960);
184 // Maximum depth for razoring
185 const Depth RazorDepth = 4 * ONE_PLY;
187 // Dynamic razoring margin based on depth
188 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
190 // Maximum depth for use of dynamic threat detection when null move fails low
191 const Depth ThreatDepth = 5 * ONE_PLY;
193 // Step 9. Internal iterative deepening
195 // Minimum depth for use of internal iterative deepening
196 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
198 // At Non-PV nodes we do an internal iterative deepening search
199 // when the static evaluation is bigger then beta - IIDMargin.
200 const Value IIDMargin = Value(0x100);
202 // Step 11. Decide the new search depth
204 // Extensions. Configurable UCI options
205 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
206 Depth CheckExtension[2], PawnPushTo7thExtension[2], PassedPawnExtension[2];
207 Depth PawnEndgameExtension[2], MateThreatExtension[2];
209 // Minimum depth for use of singular extension
210 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
212 // Step 12. Futility pruning
214 // Futility margin for quiescence search
215 const Value FutilityMarginQS = Value(0x80);
217 // Futility lookup tables (initialized at startup) and their getter functions
218 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
219 int FutilityMoveCountArray[32]; // [depth]
221 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
222 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
224 // Step 14. Reduced search
226 // Reduction lookup tables (initialized at startup) and their getter functions
227 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
229 template <NodeType PV>
230 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
232 // Easy move margin. An easy move candidate must be at least this much
233 // better than the second best move.
234 const Value EasyMoveMargin = Value(0x200);
237 /// Namespace variables
248 // Time management variables
249 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
250 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
251 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
256 std::ofstream LogFile;
258 // Multi-threads manager object
259 ThreadsManager ThreadsMgr;
261 // Node counters, used only by thread[0] but try to keep in different cache
262 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
263 bool SendSearchedNodes;
265 int NodesBetweenPolls = 30000;
272 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
274 template <NodeType PvNode, bool SpNode, bool Root>
275 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
277 template <NodeType PvNode>
278 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
280 template <NodeType PvNode>
281 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
283 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
284 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
287 template <NodeType PvNode>
288 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous);
290 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
291 bool connected_moves(const Position& pos, Move m1, Move m2);
292 bool value_is_mate(Value value);
293 Value value_to_tt(Value v, int ply);
294 Value value_from_tt(Value v, int ply);
295 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
296 bool connected_threat(const Position& pos, Move m, Move threat);
297 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
298 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
299 void update_killers(Move m, Move killers[]);
300 void update_gains(const Position& pos, Move move, Value before, Value after);
302 int current_search_time();
303 std::string value_to_uci(Value v);
304 std::string speed_to_uci(int64_t nodes);
305 void poll(const Position& pos);
306 void wait_for_stop_or_ponderhit();
308 #if !defined(_MSC_VER)
309 void* init_thread(void* threadID);
311 DWORD WINAPI init_thread(LPVOID threadID);
315 // MovePickerExt is an extended MovePicker used to choose at compile time
316 // the proper move source according to the type of node.
317 template<bool SpNode, bool Root> struct MovePickerExt;
319 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
320 // before to search them.
321 template<> struct MovePickerExt<false, true> : public MovePicker {
323 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
324 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
326 Value score = VALUE_ZERO;
328 // Score root moves using the standard way used in main search, the moves
329 // are scored according to the order in which they are returned by MovePicker.
330 // This is the second order score that is used to compare the moves when
331 // the first order pv scores of both moves are equal.
332 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
333 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
334 if (rm->pv[0] == move)
336 rm->non_pv_score = score--;
344 Move get_next_move() {
351 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
354 RootMoveList::iterator rm;
358 // In SpNodes use split point's shared MovePicker object as move source
359 template<> struct MovePickerExt<true, false> : public MovePicker {
361 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
362 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
365 Move get_next_move() { return mp->get_next_move(); }
367 RootMoveList::iterator rm; // Dummy, needed to compile
371 // Default case, create and use a MovePicker object as source
372 template<> struct MovePickerExt<false, false> : public MovePicker {
374 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
375 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
377 RootMoveList::iterator rm; // Dummy, needed to compile
387 /// init_threads(), exit_threads() and nodes_searched() are helpers to
388 /// give accessibility to some TM methods from outside of current file.
390 void init_threads() { ThreadsMgr.init_threads(); }
391 void exit_threads() { ThreadsMgr.exit_threads(); }
394 /// init_search() is called during startup. It initializes various lookup tables
398 int d; // depth (ONE_PLY == 2)
399 int hd; // half depth (ONE_PLY == 1)
402 // Init reductions array
403 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
405 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
406 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
407 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
408 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
411 // Init futility margins array
412 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
413 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
415 // Init futility move count array
416 for (d = 0; d < 32; d++)
417 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
421 /// perft() is our utility to verify move generation is bug free. All the legal
422 /// moves up to given depth are generated and counted and the sum returned.
424 int64_t perft(Position& pos, Depth depth)
426 MoveStack mlist[MOVES_MAX];
431 // Generate all legal moves
432 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
434 // If we are at the last ply we don't need to do and undo
435 // the moves, just to count them.
436 if (depth <= ONE_PLY)
437 return int(last - mlist);
439 // Loop through all legal moves
441 for (MoveStack* cur = mlist; cur != last; cur++)
444 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
445 sum += perft(pos, depth - ONE_PLY);
452 /// think() is the external interface to Stockfish's search, and is called when
453 /// the program receives the UCI 'go' command. It initializes various
454 /// search-related global variables, and calls id_loop(). It returns false
455 /// when a quit command is received during the search.
457 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
458 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
460 // Initialize global search variables
461 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
463 SearchStartTime = get_system_time();
464 ExactMaxTime = maxTime;
467 InfiniteSearch = infinite;
469 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
471 // Look for a book move, only during games, not tests
472 if (UseTimeManagement && Options["OwnBook"].value<bool>())
474 if (Options["Book File"].value<std::string>() != OpeningBook.name())
475 OpeningBook.open(Options["Book File"].value<std::string>());
477 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
478 if (bookMove != MOVE_NONE)
481 wait_for_stop_or_ponderhit();
483 cout << "bestmove " << bookMove << endl;
488 // Read UCI option values
489 TT.set_size(Options["Hash"].value<int>());
490 if (Options["Clear Hash"].value<bool>())
492 Options["Clear Hash"].set_value("false");
496 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
497 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
498 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
499 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
500 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
501 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
502 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
503 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
504 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
505 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
506 MultiPV = Options["MultiPV"].value<int>();
507 UseLogFile = Options["Use Search Log"].value<bool>();
509 read_evaluation_uci_options(pos.side_to_move());
511 // Set the number of active threads
512 ThreadsMgr.read_uci_options();
513 init_eval(ThreadsMgr.active_threads());
515 // Wake up needed threads
516 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
517 ThreadsMgr.wake_sleeping_thread(i);
520 int myTime = time[pos.side_to_move()];
521 int myIncrement = increment[pos.side_to_move()];
522 if (UseTimeManagement)
523 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
525 // Set best NodesBetweenPolls interval to avoid lagging under
526 // heavy time pressure.
528 NodesBetweenPolls = Min(MaxNodes, 30000);
529 else if (myTime && myTime < 1000)
530 NodesBetweenPolls = 1000;
531 else if (myTime && myTime < 5000)
532 NodesBetweenPolls = 5000;
534 NodesBetweenPolls = 30000;
536 // Write search information to log file
539 std::string name = Options["Search Log Filename"].value<std::string>();
540 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
542 LogFile << "\nSearching: " << pos.to_fen()
543 << "\ninfinite: " << infinite
544 << " ponder: " << ponder
545 << " time: " << myTime
546 << " increment: " << myIncrement
547 << " moves to go: " << movesToGo
551 // We're ready to start thinking. Call the iterative deepening loop function
552 Move ponderMove = MOVE_NONE;
553 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
555 // Print final search statistics
556 cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
560 int t = current_search_time();
562 LogFile << "Nodes: " << pos.nodes_searched()
563 << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0)
564 << "\nBest move: " << move_to_san(pos, bestMove);
567 pos.do_move(bestMove, st);
568 LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
569 pos.undo_move(bestMove); // Return from think() with unchanged position
573 // This makes all the threads to go to sleep
574 ThreadsMgr.set_active_threads(1);
576 // If we are pondering or in infinite search, we shouldn't print the
577 // best move before we are told to do so.
578 if (!StopRequest && (Pondering || InfiniteSearch))
579 wait_for_stop_or_ponderhit();
581 // Could be MOVE_NONE when searching on a stalemate position
582 cout << "bestmove " << bestMove;
584 // UCI protol is not clear on allowing sending an empty ponder move, instead
585 // it is clear that ponder move is optional. So skip it if empty.
586 if (ponderMove != MOVE_NONE)
587 cout << " ponder " << ponderMove;
597 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
598 // with increasing depth until the allocated thinking time has been consumed,
599 // user stops the search, or the maximum search depth is reached.
601 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
603 SearchStack ss[PLY_MAX_PLUS_2];
604 Value bestValues[PLY_MAX_PLUS_2];
605 int bestMoveChanges[PLY_MAX_PLUS_2];
606 int depth, aspirationDelta;
607 Value value, alpha, beta;
608 Move bestMove, easyMove;
610 // Initialize stuff before a new search
611 memset(ss, 0, 4 * sizeof(SearchStack));
614 *ponderMove = bestMove = easyMove = MOVE_NONE;
615 depth = aspirationDelta = 0;
616 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
617 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
619 // Moves to search are verified and copied
620 Rml.init(pos, searchMoves);
622 // Handle special case of searching on a mate/stalemate position
625 cout << "info depth 0 score "
626 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
632 // Iterative deepening loop
633 while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
635 Rml.bestMoveChanges = 0;
636 cout << set960(pos.is_chess960()) << "info depth " << depth << endl;
638 // Calculate dynamic aspiration window based on previous iterations
639 if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
641 int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
642 int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
644 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
645 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
647 alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
648 beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
651 // Start with a small aspiration window and, in case of fail high/low,
652 // research with bigger window until not failing high/low anymore.
654 // Search starting from ss+1 to allow calling update_gains()
655 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth * ONE_PLY, 0);
657 // Write PV back to transposition table in case the relevant entries
658 // have been overwritten during the search.
659 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
660 Rml[i].insert_pv_in_tt(pos);
662 // Value cannot be trusted. Break out immediately!
666 assert(value >= alpha);
668 // In case of failing high/low increase aspiration window and research,
669 // otherwise exit the fail high/low loop.
672 beta = Min(beta + aspirationDelta, VALUE_INFINITE);
673 aspirationDelta += aspirationDelta / 2;
675 else if (value <= alpha)
677 AspirationFailLow = true;
678 StopOnPonderhit = false;
680 alpha = Max(alpha - aspirationDelta, -VALUE_INFINITE);
681 aspirationDelta += aspirationDelta / 2;
686 } while (abs(value) < VALUE_KNOWN_WIN);
688 // Collect info about search result
689 bestMove = Rml[0].pv[0];
690 bestValues[depth] = value;
691 bestMoveChanges[depth] = Rml.bestMoveChanges;
693 // Send PV line to GUI and to log file
694 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
695 cout << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
698 LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
700 // Init easyMove after first iteration or drop if differs from the best move
701 if (depth == 1 && (Rml.size() == 1 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin))
703 else if (bestMove != easyMove)
704 easyMove = MOVE_NONE;
706 if (UseTimeManagement && !StopRequest)
709 bool noMoreTime = false;
711 // Stop search early when the last two iterations returned a mate score
713 && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100
714 && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100)
717 // Stop search early if one move seems to be much better than the
718 // others or if there is only a single legal move. In this latter
719 // case we search up to Iteration 8 anyway to get a proper score.
721 && easyMove == bestMove
723 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
724 && current_search_time() > TimeMgr.available_time() / 16)
725 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
726 && current_search_time() > TimeMgr.available_time() / 32)))
729 // Add some extra time if the best move has changed during the last two iterations
730 if (depth > 4 && depth < 50)
731 TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]);
733 // Stop search if most of MaxSearchTime is consumed at the end of the
734 // iteration. We probably don't have enough time to search the first
735 // move at the next iteration anyway.
736 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
742 StopOnPonderhit = true;
749 *ponderMove = Rml[0].pv[1];
754 // search<>() is the main search function for both PV and non-PV nodes and for
755 // normal and SplitPoint nodes. When called just after a split point the search
756 // is simpler because we have already probed the hash table, done a null move
757 // search, and searched the first move before splitting, we don't have to repeat
758 // all this work again. We also don't need to store anything to the hash table
759 // here: This is taken care of after we return from the split point.
761 template <NodeType PvNode, bool SpNode, bool Root>
762 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
764 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
765 assert(beta > alpha && beta <= VALUE_INFINITE);
766 assert(PvNode || alpha == beta - 1);
767 assert((Root || ply > 0) && ply < PLY_MAX);
768 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
770 Move movesSearched[MOVES_MAX];
775 Move ttMove, move, excludedMove, threatMove;
778 Value bestValue, value, oldAlpha;
779 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
780 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
781 bool mateThreat = false;
782 int moveCount = 0, playedMoveCount = 0;
783 int threadID = pos.thread();
784 SplitPoint* sp = NULL;
786 refinedValue = bestValue = value = -VALUE_INFINITE;
788 isCheck = pos.is_check();
794 ttMove = excludedMove = MOVE_NONE;
795 threatMove = sp->threatMove;
796 mateThreat = sp->mateThreat;
797 goto split_point_start;
802 // Step 1. Initialize node and poll. Polling can abort search
803 ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
804 (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
805 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
807 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
813 // Step 2. Check for aborted search and immediate draw
815 || ThreadsMgr.cutoff_at_splitpoint(threadID)
817 || ply >= PLY_MAX - 1) && !Root)
820 // Step 3. Mate distance pruning
821 alpha = Max(value_mated_in(ply), alpha);
822 beta = Min(value_mate_in(ply+1), beta);
826 // Step 4. Transposition table lookup
827 // We don't want the score of a partial search to overwrite a previous full search
828 // TT value, so we use a different position key in case of an excluded move.
829 excludedMove = ss->excludedMove;
830 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
832 tte = TT.retrieve(posKey);
833 ttMove = tte ? tte->move() : MOVE_NONE;
835 // At PV nodes we check for exact scores, while at non-PV nodes we check for
836 // and return a fail high/low. Biggest advantage at probing at PV nodes is
837 // to have a smooth experience in analysis mode.
840 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
841 : ok_to_use_TT(tte, depth, beta, ply)))
844 ss->bestMove = ttMove; // Can be MOVE_NONE
845 return value_from_tt(tte->value(), ply);
848 // Step 5. Evaluate the position statically and
849 // update gain statistics of parent move.
851 ss->eval = ss->evalMargin = VALUE_NONE;
854 assert(tte->static_value() != VALUE_NONE);
856 ss->eval = tte->static_value();
857 ss->evalMargin = tte->static_value_margin();
858 refinedValue = refine_eval(tte, ss->eval, ply);
862 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
863 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
866 // Save gain for the parent non-capture move
867 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
869 // Step 6. Razoring (is omitted in PV nodes)
871 && depth < RazorDepth
873 && refinedValue < beta - razor_margin(depth)
874 && ttMove == MOVE_NONE
875 && !value_is_mate(beta)
876 && !pos.has_pawn_on_7th(pos.side_to_move()))
878 Value rbeta = beta - razor_margin(depth);
879 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
881 // Logically we should return (v + razor_margin(depth)), but
882 // surprisingly this did slightly weaker in tests.
886 // Step 7. Static null move pruning (is omitted in PV nodes)
887 // We're betting that the opponent doesn't have a move that will reduce
888 // the score by more than futility_margin(depth) if we do a null move.
891 && depth < RazorDepth
893 && refinedValue >= beta + futility_margin(depth, 0)
894 && !value_is_mate(beta)
895 && pos.non_pawn_material(pos.side_to_move()))
896 return refinedValue - futility_margin(depth, 0);
898 // Step 8. Null move search with verification search (is omitted in PV nodes)
903 && refinedValue >= beta
904 && !value_is_mate(beta)
905 && pos.non_pawn_material(pos.side_to_move()))
907 ss->currentMove = MOVE_NULL;
909 // Null move dynamic reduction based on depth
910 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
912 // Null move dynamic reduction based on value
913 if (refinedValue - beta > PawnValueMidgame)
916 pos.do_null_move(st);
917 (ss+1)->skipNullMove = true;
918 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
919 (ss+1)->skipNullMove = false;
920 pos.undo_null_move();
922 if (nullValue >= beta)
924 // Do not return unproven mate scores
925 if (nullValue >= value_mate_in(PLY_MAX))
928 if (depth < 6 * ONE_PLY)
931 // Do verification search at high depths
932 ss->skipNullMove = true;
933 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
934 ss->skipNullMove = false;
941 // The null move failed low, which means that we may be faced with
942 // some kind of threat. If the previous move was reduced, check if
943 // the move that refuted the null move was somehow connected to the
944 // move which was reduced. If a connection is found, return a fail
945 // low score (which will cause the reduced move to fail high in the
946 // parent node, which will trigger a re-search with full depth).
947 if (nullValue == value_mated_in(ply + 2))
950 threatMove = (ss+1)->bestMove;
951 if ( depth < ThreatDepth
953 && threatMove != MOVE_NONE
954 && connected_moves(pos, (ss-1)->currentMove, threatMove))
959 // Step 9. Internal iterative deepening
960 if ( depth >= IIDDepth[PvNode]
961 && ttMove == MOVE_NONE
962 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
964 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
966 ss->skipNullMove = true;
967 search<PvNode>(pos, ss, alpha, beta, d, ply);
968 ss->skipNullMove = false;
970 ttMove = ss->bestMove;
971 tte = TT.retrieve(posKey);
974 // Expensive mate threat detection (only for PV nodes)
976 mateThreat = pos.has_mate_threat();
978 split_point_start: // At split points actual search starts from here
980 // Initialize a MovePicker object for the current position
981 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
983 ss->bestMove = MOVE_NONE;
984 futilityBase = ss->eval + ss->evalMargin;
985 singularExtensionNode = !Root
987 && depth >= SingularExtensionDepth[PvNode]
990 && !excludedMove // Do not allow recursive singular extension search
991 && (tte->type() & VALUE_TYPE_LOWER)
992 && tte->depth() >= depth - 3 * ONE_PLY;
995 lock_grab(&(sp->lock));
996 bestValue = sp->bestValue;
999 // Step 10. Loop through moves
1000 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1001 while ( bestValue < beta
1002 && (move = mp.get_next_move()) != MOVE_NONE
1003 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1005 assert(move_is_ok(move));
1009 moveCount = ++sp->moveCount;
1010 lock_release(&(sp->lock));
1012 else if (move == excludedMove)
1019 // This is used by time management
1020 FirstRootMove = (moveCount == 1);
1022 // Save the current node count before the move is searched
1023 nodes = pos.nodes_searched();
1025 // If it's time to send nodes info, do it here where we have the
1026 // correct accumulated node counts searched by each thread.
1027 if (SendSearchedNodes)
1029 SendSearchedNodes = false;
1030 cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
1033 if (current_search_time() >= 1000)
1034 cout << "info currmove " << move
1035 << " currmovenumber " << moveCount << endl;
1038 // At Root and at first iteration do a PV search on all the moves
1039 // to score root moves. Otherwise only the first one is the PV.
1040 isPvMove = (PvNode && moveCount <= (Root ? MultiPV + 1000 * (depth <= ONE_PLY) : 1));
1041 moveIsCheck = pos.move_is_check(move, ci);
1042 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1044 // Step 11. Decide the new search depth
1045 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1047 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1048 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1049 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1050 // lower than ttValue minus a margin then we extend ttMove.
1051 if ( singularExtensionNode
1052 && move == tte->move()
1055 Value ttValue = value_from_tt(tte->value(), ply);
1057 if (abs(ttValue) < VALUE_KNOWN_WIN)
1059 Value b = ttValue - int(depth);
1060 ss->excludedMove = move;
1061 ss->skipNullMove = true;
1062 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1063 ss->skipNullMove = false;
1064 ss->excludedMove = MOVE_NONE;
1065 ss->bestMove = MOVE_NONE;
1071 // Update current move (this must be done after singular extension search)
1072 ss->currentMove = move;
1073 newDepth = depth - ONE_PLY + ext;
1075 // Step 12. Futility pruning (is omitted in PV nodes)
1077 && !captureOrPromotion
1081 && !move_is_castle(move))
1083 // Move count based pruning
1084 if ( moveCount >= futility_move_count(depth)
1085 && !(threatMove && connected_threat(pos, move, threatMove))
1086 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1089 lock_grab(&(sp->lock));
1094 // Value based pruning
1095 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1096 // but fixing this made program slightly weaker.
1097 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1098 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1099 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1101 if (futilityValueScaled < beta)
1105 lock_grab(&(sp->lock));
1106 if (futilityValueScaled > sp->bestValue)
1107 sp->bestValue = bestValue = futilityValueScaled;
1109 else if (futilityValueScaled > bestValue)
1110 bestValue = futilityValueScaled;
1115 // Prune moves with negative SEE at low depths
1116 if ( predictedDepth < 2 * ONE_PLY
1117 && bestValue > value_mated_in(PLY_MAX)
1118 && pos.see_sign(move) < 0)
1121 lock_grab(&(sp->lock));
1127 // Step 13. Make the move
1128 pos.do_move(move, st, ci, moveIsCheck);
1130 if (!SpNode && !captureOrPromotion)
1131 movesSearched[playedMoveCount++] = move;
1133 // Step extra. pv search (only in PV nodes)
1134 // The first move in list is the expected PV
1137 // Aspiration window is disabled in multi-pv case
1138 if (Root && MultiPV > 1)
1139 alpha = -VALUE_INFINITE;
1141 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1145 // Step 14. Reduced depth search
1146 // If the move fails high will be re-searched at full depth.
1147 bool doFullDepthSearch = true;
1149 if ( depth >= 3 * ONE_PLY
1150 && !captureOrPromotion
1152 && !move_is_castle(move)
1153 && ss->killers[0] != move
1154 && ss->killers[1] != move)
1156 ss->reduction = reduction<PvNode>(depth, moveCount);
1159 alpha = SpNode ? sp->alpha : alpha;
1160 Depth d = newDepth - ss->reduction;
1161 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1163 doFullDepthSearch = (value > alpha);
1165 ss->reduction = DEPTH_ZERO; // Restore original reduction
1168 // Step 15. Full depth search
1169 if (doFullDepthSearch)
1171 alpha = SpNode ? sp->alpha : alpha;
1172 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1174 // Step extra. pv search (only in PV nodes)
1175 // Search only for possible new PV nodes, if instead value >= beta then
1176 // parent node fails low with value <= alpha and tries another move.
1177 if (PvNode && value > alpha && (Root || value < beta))
1178 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1182 // Step 16. Undo move
1183 pos.undo_move(move);
1185 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1187 // Step 17. Check for new best move
1190 lock_grab(&(sp->lock));
1191 bestValue = sp->bestValue;
1195 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1200 sp->bestValue = value;
1202 if (!Root && value > alpha)
1204 if (PvNode && value < beta) // We want always alpha < beta
1212 sp->betaCutoff = true;
1214 if (value == value_mate_in(ply + 1))
1215 ss->mateKiller = move;
1217 ss->bestMove = move;
1220 sp->ss->bestMove = move;
1226 // Finished searching the move. If StopRequest is true, the search
1227 // was aborted because the user interrupted the search or because we
1228 // ran out of time. In this case, the return value of the search cannot
1229 // be trusted, and we break out of the loop without updating the best
1234 // Remember searched nodes counts for this move
1235 mp.rm->nodes += pos.nodes_searched() - nodes;
1237 // PV move or new best move ?
1238 if (isPvMove || value > alpha)
1241 ss->bestMove = move;
1242 mp.rm->pv_score = value;
1243 mp.rm->extract_pv_from_tt(pos);
1245 // We record how often the best move has been changed in each
1246 // iteration. This information is used for time management: When
1247 // the best move changes frequently, we allocate some more time.
1248 if (!isPvMove && MultiPV == 1)
1249 Rml.bestMoveChanges++;
1251 Rml.sort_multipv(moveCount);
1253 // Update alpha. In multi-pv we don't use aspiration window, so
1254 // set alpha equal to minimum score among the PV lines.
1256 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1257 else if (value > alpha)
1261 mp.rm->pv_score = -VALUE_INFINITE;
1265 // Step 18. Check for split
1268 && depth >= ThreadsMgr.min_split_depth()
1269 && ThreadsMgr.active_threads() > 1
1271 && ThreadsMgr.available_thread_exists(threadID)
1273 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1274 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1275 threatMove, mateThreat, moveCount, &mp, PvNode);
1278 // Step 19. Check for mate and stalemate
1279 // All legal moves have been searched and if there are
1280 // no legal moves, it must be mate or stalemate.
1281 // If one move was excluded return fail low score.
1282 if (!SpNode && !moveCount)
1283 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1285 // Step 20. Update tables
1286 // If the search is not aborted, update the transposition table,
1287 // history counters, and killer moves.
1288 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1290 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1291 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1292 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1294 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1296 // Update killers and history only for non capture moves that fails high
1297 if ( bestValue >= beta
1298 && !pos.move_is_capture_or_promotion(move))
1300 update_history(pos, move, depth, movesSearched, playedMoveCount);
1301 update_killers(move, ss->killers);
1307 // Here we have the lock still grabbed
1308 sp->slaves[threadID] = 0;
1309 sp->nodes += pos.nodes_searched();
1310 lock_release(&(sp->lock));
1313 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1318 // qsearch() is the quiescence search function, which is called by the main
1319 // search function when the remaining depth is zero (or, to be more precise,
1320 // less than ONE_PLY).
1322 template <NodeType PvNode>
1323 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1325 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1326 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1327 assert(PvNode || alpha == beta - 1);
1329 assert(ply > 0 && ply < PLY_MAX);
1330 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1334 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1335 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1338 Value oldAlpha = alpha;
1340 ss->bestMove = ss->currentMove = MOVE_NONE;
1342 // Check for an instant draw or maximum ply reached
1343 if (pos.is_draw() || ply >= PLY_MAX - 1)
1346 // Decide whether or not to include checks, this fixes also the type of
1347 // TT entry depth that we are going to use. Note that in qsearch we use
1348 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1349 isCheck = pos.is_check();
1350 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1352 // Transposition table lookup. At PV nodes, we don't use the TT for
1353 // pruning, but only for move ordering.
1354 tte = TT.retrieve(pos.get_key());
1355 ttMove = (tte ? tte->move() : MOVE_NONE);
1357 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1359 ss->bestMove = ttMove; // Can be MOVE_NONE
1360 return value_from_tt(tte->value(), ply);
1363 // Evaluate the position statically
1366 bestValue = futilityBase = -VALUE_INFINITE;
1367 ss->eval = evalMargin = VALUE_NONE;
1368 enoughMaterial = false;
1374 assert(tte->static_value() != VALUE_NONE);
1376 evalMargin = tte->static_value_margin();
1377 ss->eval = bestValue = tte->static_value();
1380 ss->eval = bestValue = evaluate(pos, evalMargin);
1382 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1384 // Stand pat. Return immediately if static value is at least beta
1385 if (bestValue >= beta)
1388 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1393 if (PvNode && bestValue > alpha)
1396 // Futility pruning parameters, not needed when in check
1397 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1398 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1401 // Initialize a MovePicker object for the current position, and prepare
1402 // to search the moves. Because the depth is <= 0 here, only captures,
1403 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1405 MovePicker mp(pos, ttMove, depth, H);
1408 // Loop through the moves until no moves remain or a beta cutoff occurs
1409 while ( alpha < beta
1410 && (move = mp.get_next_move()) != MOVE_NONE)
1412 assert(move_is_ok(move));
1414 moveIsCheck = pos.move_is_check(move, ci);
1422 && !move_is_promotion(move)
1423 && !pos.move_is_passed_pawn_push(move))
1425 futilityValue = futilityBase
1426 + pos.endgame_value_of_piece_on(move_to(move))
1427 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1429 if (futilityValue < alpha)
1431 if (futilityValue > bestValue)
1432 bestValue = futilityValue;
1436 // Prune moves with negative or equal SEE
1437 if ( futilityBase < beta
1438 && depth < DEPTH_ZERO
1439 && pos.see(move) <= 0)
1443 // Detect non-capture evasions that are candidate to be pruned
1444 evasionPrunable = isCheck
1445 && bestValue > value_mated_in(PLY_MAX)
1446 && !pos.move_is_capture(move)
1447 && !pos.can_castle(pos.side_to_move());
1449 // Don't search moves with negative SEE values
1451 && (!isCheck || evasionPrunable)
1453 && !move_is_promotion(move)
1454 && pos.see_sign(move) < 0)
1457 // Don't search useless checks
1462 && !pos.move_is_capture_or_promotion(move)
1463 && ss->eval + PawnValueMidgame / 4 < beta
1464 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1466 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1467 bestValue = ss->eval + PawnValueMidgame / 4;
1472 // Update current move
1473 ss->currentMove = move;
1475 // Make and search the move
1476 pos.do_move(move, st, ci, moveIsCheck);
1477 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1478 pos.undo_move(move);
1480 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1483 if (value > bestValue)
1489 ss->bestMove = move;
1494 // All legal moves have been searched. A special case: If we're in check
1495 // and no legal moves were found, it is checkmate.
1496 if (isCheck && bestValue == -VALUE_INFINITE)
1497 return value_mated_in(ply);
1499 // Update transposition table
1500 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1501 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1503 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1509 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1510 // bestValue is updated only when returning false because in that case move
1513 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1515 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1516 Square from, to, ksq, victimSq;
1519 Value futilityValue, bv = *bestValue;
1521 from = move_from(move);
1523 them = opposite_color(pos.side_to_move());
1524 ksq = pos.king_square(them);
1525 kingAtt = pos.attacks_from<KING>(ksq);
1526 pc = pos.piece_on(from);
1528 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1529 oldAtt = pos.attacks_from(pc, from, occ);
1530 newAtt = pos.attacks_from(pc, to, occ);
1532 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1533 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1535 if (!(b && (b & (b - 1))))
1538 // Rule 2. Queen contact check is very dangerous
1539 if ( type_of_piece(pc) == QUEEN
1540 && bit_is_set(kingAtt, to))
1543 // Rule 3. Creating new double threats with checks
1544 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1548 victimSq = pop_1st_bit(&b);
1549 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1551 // Note that here we generate illegal "double move"!
1552 if ( futilityValue >= beta
1553 && pos.see_sign(make_move(from, victimSq)) >= 0)
1556 if (futilityValue > bv)
1560 // Update bestValue only if check is not dangerous (because we will prune the move)
1566 // connected_moves() tests whether two moves are 'connected' in the sense
1567 // that the first move somehow made the second move possible (for instance
1568 // if the moving piece is the same in both moves). The first move is assumed
1569 // to be the move that was made to reach the current position, while the
1570 // second move is assumed to be a move from the current position.
1572 bool connected_moves(const Position& pos, Move m1, Move m2) {
1574 Square f1, t1, f2, t2;
1577 assert(m1 && move_is_ok(m1));
1578 assert(m2 && move_is_ok(m2));
1580 // Case 1: The moving piece is the same in both moves
1586 // Case 2: The destination square for m2 was vacated by m1
1592 // Case 3: Moving through the vacated square
1593 if ( piece_is_slider(pos.piece_on(f2))
1594 && bit_is_set(squares_between(f2, t2), f1))
1597 // Case 4: The destination square for m2 is defended by the moving piece in m1
1598 p = pos.piece_on(t1);
1599 if (bit_is_set(pos.attacks_from(p, t1), t2))
1602 // Case 5: Discovered check, checking piece is the piece moved in m1
1603 if ( piece_is_slider(p)
1604 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1605 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1607 // discovered_check_candidates() works also if the Position's side to
1608 // move is the opposite of the checking piece.
1609 Color them = opposite_color(pos.side_to_move());
1610 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1612 if (bit_is_set(dcCandidates, f2))
1619 // value_is_mate() checks if the given value is a mate one eventually
1620 // compensated for the ply.
1622 bool value_is_mate(Value value) {
1624 assert(abs(value) <= VALUE_INFINITE);
1626 return value <= value_mated_in(PLY_MAX)
1627 || value >= value_mate_in(PLY_MAX);
1631 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1632 // "plies to mate from the current ply". Non-mate scores are unchanged.
1633 // The function is called before storing a value to the transposition table.
1635 Value value_to_tt(Value v, int ply) {
1637 if (v >= value_mate_in(PLY_MAX))
1640 if (v <= value_mated_in(PLY_MAX))
1647 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1648 // the transposition table to a mate score corrected for the current ply.
1650 Value value_from_tt(Value v, int ply) {
1652 if (v >= value_mate_in(PLY_MAX))
1655 if (v <= value_mated_in(PLY_MAX))
1662 // extension() decides whether a move should be searched with normal depth,
1663 // or with extended depth. Certain classes of moves (checking moves, in
1664 // particular) are searched with bigger depth than ordinary moves and in
1665 // any case are marked as 'dangerous'. Note that also if a move is not
1666 // extended, as example because the corresponding UCI option is set to zero,
1667 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1668 template <NodeType PvNode>
1669 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1670 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1672 assert(m != MOVE_NONE);
1674 Depth result = DEPTH_ZERO;
1675 *dangerous = moveIsCheck | mateThreat;
1679 if (moveIsCheck && pos.see_sign(m) >= 0)
1680 result += CheckExtension[PvNode];
1683 result += MateThreatExtension[PvNode];
1686 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1688 Color c = pos.side_to_move();
1689 if (relative_rank(c, move_to(m)) == RANK_7)
1691 result += PawnPushTo7thExtension[PvNode];
1694 if (pos.pawn_is_passed(c, move_to(m)))
1696 result += PassedPawnExtension[PvNode];
1701 if ( captureOrPromotion
1702 && pos.type_of_piece_on(move_to(m)) != PAWN
1703 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1704 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1705 && !move_is_promotion(m)
1708 result += PawnEndgameExtension[PvNode];
1713 && captureOrPromotion
1714 && pos.type_of_piece_on(move_to(m)) != PAWN
1715 && pos.see_sign(m) >= 0)
1717 result += ONE_PLY / 2;
1721 return Min(result, ONE_PLY);
1725 // connected_threat() tests whether it is safe to forward prune a move or if
1726 // is somehow connected to the threat move returned by null search.
1728 bool connected_threat(const Position& pos, Move m, Move threat) {
1730 assert(move_is_ok(m));
1731 assert(threat && move_is_ok(threat));
1732 assert(!pos.move_is_check(m));
1733 assert(!pos.move_is_capture_or_promotion(m));
1734 assert(!pos.move_is_passed_pawn_push(m));
1736 Square mfrom, mto, tfrom, tto;
1738 mfrom = move_from(m);
1740 tfrom = move_from(threat);
1741 tto = move_to(threat);
1743 // Case 1: Don't prune moves which move the threatened piece
1747 // Case 2: If the threatened piece has value less than or equal to the
1748 // value of the threatening piece, don't prune moves which defend it.
1749 if ( pos.move_is_capture(threat)
1750 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1751 || pos.type_of_piece_on(tfrom) == KING)
1752 && pos.move_attacks_square(m, tto))
1755 // Case 3: If the moving piece in the threatened move is a slider, don't
1756 // prune safe moves which block its ray.
1757 if ( piece_is_slider(pos.piece_on(tfrom))
1758 && bit_is_set(squares_between(tfrom, tto), mto)
1759 && pos.see_sign(m) >= 0)
1766 // ok_to_use_TT() returns true if a transposition table score
1767 // can be used at a given point in search.
1769 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1771 Value v = value_from_tt(tte->value(), ply);
1773 return ( tte->depth() >= depth
1774 || v >= Max(value_mate_in(PLY_MAX), beta)
1775 || v < Min(value_mated_in(PLY_MAX), beta))
1777 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1778 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1782 // refine_eval() returns the transposition table score if
1783 // possible otherwise falls back on static position evaluation.
1785 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1789 Value v = value_from_tt(tte->value(), ply);
1791 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1792 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1799 // update_history() registers a good move that produced a beta-cutoff
1800 // in history and marks as failures all the other moves of that ply.
1802 void update_history(const Position& pos, Move move, Depth depth,
1803 Move movesSearched[], int moveCount) {
1805 Value bonus = Value(int(depth) * int(depth));
1807 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1809 for (int i = 0; i < moveCount - 1; i++)
1811 m = movesSearched[i];
1815 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1820 // update_killers() add a good move that produced a beta-cutoff
1821 // among the killer moves of that ply.
1823 void update_killers(Move m, Move killers[]) {
1825 if (m != killers[0])
1827 killers[1] = killers[0];
1833 // update_gains() updates the gains table of a non-capture move given
1834 // the static position evaluation before and after the move.
1836 void update_gains(const Position& pos, Move m, Value before, Value after) {
1839 && before != VALUE_NONE
1840 && after != VALUE_NONE
1841 && pos.captured_piece_type() == PIECE_TYPE_NONE
1842 && !move_is_special(m))
1843 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1846 // current_search_time() returns the number of milliseconds which have passed
1847 // since the beginning of the current search.
1849 int current_search_time() {
1851 return get_system_time() - SearchStartTime;
1855 // value_to_uci() converts a value to a string suitable for use with the UCI
1856 // protocol specifications:
1858 // cp <x> The score from the engine's point of view in centipawns.
1859 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1860 // use negative values for y.
1862 std::string value_to_uci(Value v) {
1864 std::stringstream s;
1866 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1867 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1869 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
1875 // speed_to_uci() returns a string with time stats of current search suitable
1876 // to be sent to UCI gui.
1878 std::string speed_to_uci(int64_t nodes) {
1880 std::stringstream s;
1881 int t = current_search_time();
1883 s << " nodes " << nodes
1884 << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
1891 // poll() performs two different functions: It polls for user input, and it
1892 // looks at the time consumed so far and decides if it's time to abort the
1895 void poll(const Position& pos) {
1897 static int lastInfoTime;
1898 int t = current_search_time();
1901 if (input_available())
1903 // We are line oriented, don't read single chars
1904 std::string command;
1906 if (!std::getline(std::cin, command))
1909 if (command == "quit")
1911 // Quit the program as soon as possible
1913 QuitRequest = StopRequest = true;
1916 else if (command == "stop")
1918 // Stop calculating as soon as possible, but still send the "bestmove"
1919 // and possibly the "ponder" token when finishing the search.
1923 else if (command == "ponderhit")
1925 // The opponent has played the expected move. GUI sends "ponderhit" if
1926 // we were told to ponder on the same move the opponent has played. We
1927 // should continue searching but switching from pondering to normal search.
1930 if (StopOnPonderhit)
1935 // Print search information
1939 else if (lastInfoTime > t)
1940 // HACK: Must be a new search where we searched less than
1941 // NodesBetweenPolls nodes during the first second of search.
1944 else if (t - lastInfoTime >= 1000)
1951 if (dbg_show_hit_rate)
1952 dbg_print_hit_rate();
1954 // Send info on searched nodes as soon as we return to root
1955 SendSearchedNodes = true;
1958 // Should we stop the search?
1962 bool stillAtFirstMove = FirstRootMove
1963 && !AspirationFailLow
1964 && t > TimeMgr.available_time();
1966 bool noMoreTime = t > TimeMgr.maximum_time()
1967 || stillAtFirstMove;
1969 if ( (UseTimeManagement && noMoreTime)
1970 || (ExactMaxTime && t >= ExactMaxTime)
1971 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1976 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1977 // while the program is pondering. The point is to work around a wrinkle in
1978 // the UCI protocol: When pondering, the engine is not allowed to give a
1979 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1980 // We simply wait here until one of these commands is sent, and return,
1981 // after which the bestmove and pondermove will be printed.
1983 void wait_for_stop_or_ponderhit() {
1985 std::string command;
1989 // Wait for a command from stdin
1990 if (!std::getline(std::cin, command))
1993 if (command == "quit")
1998 else if (command == "ponderhit" || command == "stop")
2004 // init_thread() is the function which is called when a new thread is
2005 // launched. It simply calls the idle_loop() function with the supplied
2006 // threadID. There are two versions of this function; one for POSIX
2007 // threads and one for Windows threads.
2009 #if !defined(_MSC_VER)
2011 void* init_thread(void* threadID) {
2013 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2019 DWORD WINAPI init_thread(LPVOID threadID) {
2021 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2028 /// The ThreadsManager class
2031 // read_uci_options() updates number of active threads and other internal
2032 // parameters according to the UCI options values. It is called before
2033 // to start a new search.
2035 void ThreadsManager::read_uci_options() {
2037 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2038 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2039 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2040 activeThreads = Options["Threads"].value<int>();
2044 // idle_loop() is where the threads are parked when they have no work to do.
2045 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2046 // object for which the current thread is the master.
2048 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2050 assert(threadID >= 0 && threadID < MAX_THREADS);
2053 bool allFinished = false;
2057 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2058 // master should exit as last one.
2059 if (allThreadsShouldExit)
2062 threads[threadID].state = THREAD_TERMINATED;
2066 // If we are not thinking, wait for a condition to be signaled
2067 // instead of wasting CPU time polling for work.
2068 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2069 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2071 assert(!sp || useSleepingThreads);
2072 assert(threadID != 0 || useSleepingThreads);
2074 if (threads[threadID].state == THREAD_INITIALIZING)
2075 threads[threadID].state = THREAD_AVAILABLE;
2077 // Grab the lock to avoid races with wake_sleeping_thread()
2078 lock_grab(&sleepLock[threadID]);
2080 // If we are master and all slaves have finished do not go to sleep
2081 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2082 allFinished = (i == activeThreads);
2084 if (allFinished || allThreadsShouldExit)
2086 lock_release(&sleepLock[threadID]);
2090 // Do sleep here after retesting sleep conditions
2091 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2092 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2094 lock_release(&sleepLock[threadID]);
2097 // If this thread has been assigned work, launch a search
2098 if (threads[threadID].state == THREAD_WORKISWAITING)
2100 assert(!allThreadsShouldExit);
2102 threads[threadID].state = THREAD_SEARCHING;
2104 // Copy SplitPoint position and search stack and call search()
2105 // with SplitPoint template parameter set to true.
2106 SearchStack ss[PLY_MAX_PLUS_2];
2107 SplitPoint* tsp = threads[threadID].splitPoint;
2108 Position pos(*tsp->pos, threadID);
2110 memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
2114 search<PV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2116 search<NonPV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2118 assert(threads[threadID].state == THREAD_SEARCHING);
2120 threads[threadID].state = THREAD_AVAILABLE;
2122 // Wake up master thread so to allow it to return from the idle loop in
2123 // case we are the last slave of the split point.
2124 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2125 wake_sleeping_thread(tsp->master);
2128 // If this thread is the master of a split point and all slaves have
2129 // finished their work at this split point, return from the idle loop.
2130 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2131 allFinished = (i == activeThreads);
2135 // Because sp->slaves[] is reset under lock protection,
2136 // be sure sp->lock has been released before to return.
2137 lock_grab(&(sp->lock));
2138 lock_release(&(sp->lock));
2140 // In helpful master concept a master can help only a sub-tree, and
2141 // because here is all finished is not possible master is booked.
2142 assert(threads[threadID].state == THREAD_AVAILABLE);
2144 threads[threadID].state = THREAD_SEARCHING;
2151 // init_threads() is called during startup. It launches all helper threads,
2152 // and initializes the split point stack and the global locks and condition
2155 void ThreadsManager::init_threads() {
2157 int i, arg[MAX_THREADS];
2160 // Initialize global locks
2163 for (i = 0; i < MAX_THREADS; i++)
2165 lock_init(&sleepLock[i]);
2166 cond_init(&sleepCond[i]);
2169 // Initialize splitPoints[] locks
2170 for (i = 0; i < MAX_THREADS; i++)
2171 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2172 lock_init(&(threads[i].splitPoints[j].lock));
2174 // Will be set just before program exits to properly end the threads
2175 allThreadsShouldExit = false;
2177 // Threads will be put all threads to sleep as soon as created
2180 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2181 threads[0].state = THREAD_SEARCHING;
2182 for (i = 1; i < MAX_THREADS; i++)
2183 threads[i].state = THREAD_INITIALIZING;
2185 // Launch the helper threads
2186 for (i = 1; i < MAX_THREADS; i++)
2190 #if !defined(_MSC_VER)
2191 pthread_t pthread[1];
2192 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2193 pthread_detach(pthread[0]);
2195 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2199 cout << "Failed to create thread number " << i << endl;
2203 // Wait until the thread has finished launching and is gone to sleep
2204 while (threads[i].state == THREAD_INITIALIZING) {}
2209 // exit_threads() is called when the program exits. It makes all the
2210 // helper threads exit cleanly.
2212 void ThreadsManager::exit_threads() {
2214 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2216 // Wake up all the threads and waits for termination
2217 for (int i = 1; i < MAX_THREADS; i++)
2219 wake_sleeping_thread(i);
2220 while (threads[i].state != THREAD_TERMINATED) {}
2223 // Now we can safely destroy the locks
2224 for (int i = 0; i < MAX_THREADS; i++)
2225 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2226 lock_destroy(&(threads[i].splitPoints[j].lock));
2228 lock_destroy(&mpLock);
2230 // Now we can safely destroy the wait conditions
2231 for (int i = 0; i < MAX_THREADS; i++)
2233 lock_destroy(&sleepLock[i]);
2234 cond_destroy(&sleepCond[i]);
2239 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2240 // the thread's currently active split point, or in some ancestor of
2241 // the current split point.
2243 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2245 assert(threadID >= 0 && threadID < activeThreads);
2247 SplitPoint* sp = threads[threadID].splitPoint;
2249 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2254 // thread_is_available() checks whether the thread with threadID "slave" is
2255 // available to help the thread with threadID "master" at a split point. An
2256 // obvious requirement is that "slave" must be idle. With more than two
2257 // threads, this is not by itself sufficient: If "slave" is the master of
2258 // some active split point, it is only available as a slave to the other
2259 // threads which are busy searching the split point at the top of "slave"'s
2260 // split point stack (the "helpful master concept" in YBWC terminology).
2262 bool ThreadsManager::thread_is_available(int slave, int master) const {
2264 assert(slave >= 0 && slave < activeThreads);
2265 assert(master >= 0 && master < activeThreads);
2266 assert(activeThreads > 1);
2268 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2271 // Make a local copy to be sure doesn't change under our feet
2272 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2274 // No active split points means that the thread is available as
2275 // a slave for any other thread.
2276 if (localActiveSplitPoints == 0 || activeThreads == 2)
2279 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2280 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2281 // could have been set to 0 by another thread leading to an out of bound access.
2282 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2289 // available_thread_exists() tries to find an idle thread which is available as
2290 // a slave for the thread with threadID "master".
2292 bool ThreadsManager::available_thread_exists(int master) const {
2294 assert(master >= 0 && master < activeThreads);
2295 assert(activeThreads > 1);
2297 for (int i = 0; i < activeThreads; i++)
2298 if (thread_is_available(i, master))
2305 // split() does the actual work of distributing the work at a node between
2306 // several available threads. If it does not succeed in splitting the
2307 // node (because no idle threads are available, or because we have no unused
2308 // split point objects), the function immediately returns. If splitting is
2309 // possible, a SplitPoint object is initialized with all the data that must be
2310 // copied to the helper threads and we tell our helper threads that they have
2311 // been assigned work. This will cause them to instantly leave their idle loops and
2312 // call search().When all threads have returned from search() then split() returns.
2314 template <bool Fake>
2315 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2316 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2317 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2318 assert(pos.is_ok());
2319 assert(ply > 0 && ply < PLY_MAX);
2320 assert(*bestValue >= -VALUE_INFINITE);
2321 assert(*bestValue <= *alpha);
2322 assert(*alpha < beta);
2323 assert(beta <= VALUE_INFINITE);
2324 assert(depth > DEPTH_ZERO);
2325 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2326 assert(activeThreads > 1);
2328 int i, master = pos.thread();
2329 Thread& masterThread = threads[master];
2333 // If no other thread is available to help us, or if we have too many
2334 // active split points, don't split.
2335 if ( !available_thread_exists(master)
2336 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2338 lock_release(&mpLock);
2342 // Pick the next available split point object from the split point stack
2343 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2345 // Initialize the split point object
2346 splitPoint.parent = masterThread.splitPoint;
2347 splitPoint.master = master;
2348 splitPoint.betaCutoff = false;
2349 splitPoint.ply = ply;
2350 splitPoint.depth = depth;
2351 splitPoint.threatMove = threatMove;
2352 splitPoint.mateThreat = mateThreat;
2353 splitPoint.alpha = *alpha;
2354 splitPoint.beta = beta;
2355 splitPoint.pvNode = pvNode;
2356 splitPoint.bestValue = *bestValue;
2358 splitPoint.moveCount = moveCount;
2359 splitPoint.pos = &pos;
2360 splitPoint.nodes = 0;
2362 for (i = 0; i < activeThreads; i++)
2363 splitPoint.slaves[i] = 0;
2365 masterThread.splitPoint = &splitPoint;
2367 // If we are here it means we are not available
2368 assert(masterThread.state != THREAD_AVAILABLE);
2370 int workersCnt = 1; // At least the master is included
2372 // Allocate available threads setting state to THREAD_BOOKED
2373 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2374 if (thread_is_available(i, master))
2376 threads[i].state = THREAD_BOOKED;
2377 threads[i].splitPoint = &splitPoint;
2378 splitPoint.slaves[i] = 1;
2382 assert(Fake || workersCnt > 1);
2384 // We can release the lock because slave threads are already booked and master is not available
2385 lock_release(&mpLock);
2387 // Tell the threads that they have work to do. This will make them leave
2389 for (i = 0; i < activeThreads; i++)
2390 if (i == master || splitPoint.slaves[i])
2392 assert(i == master || threads[i].state == THREAD_BOOKED);
2394 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2396 if (useSleepingThreads && i != master)
2397 wake_sleeping_thread(i);
2400 // Everything is set up. The master thread enters the idle loop, from
2401 // which it will instantly launch a search, because its state is
2402 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2403 // idle loop, which means that the main thread will return from the idle
2404 // loop when all threads have finished their work at this split point.
2405 idle_loop(master, &splitPoint);
2407 // We have returned from the idle loop, which means that all threads are
2408 // finished. Update alpha and bestValue, and return.
2411 *alpha = splitPoint.alpha;
2412 *bestValue = splitPoint.bestValue;
2413 masterThread.activeSplitPoints--;
2414 masterThread.splitPoint = splitPoint.parent;
2415 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2417 lock_release(&mpLock);
2421 // wake_sleeping_thread() wakes up the thread with the given threadID
2422 // when it is time to start a new search.
2424 void ThreadsManager::wake_sleeping_thread(int threadID) {
2426 lock_grab(&sleepLock[threadID]);
2427 cond_signal(&sleepCond[threadID]);
2428 lock_release(&sleepLock[threadID]);
2432 /// RootMove and RootMoveList method's definitions
2434 RootMove::RootMove() {
2437 pv_score = non_pv_score = -VALUE_INFINITE;
2441 RootMove& RootMove::operator=(const RootMove& rm) {
2443 const Move* src = rm.pv;
2446 // Avoid a costly full rm.pv[] copy
2447 do *dst++ = *src; while (*src++ != MOVE_NONE);
2450 pv_score = rm.pv_score;
2451 non_pv_score = rm.non_pv_score;
2455 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2456 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2457 // allow to always have a ponder move even when we fail high at root and also a
2458 // long PV to print that is important for position analysis.
2460 void RootMove::extract_pv_from_tt(Position& pos) {
2462 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2466 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2468 pos.do_move(pv[0], *st++);
2470 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2471 && tte->move() != MOVE_NONE
2472 && move_is_legal(pos, tte->move())
2474 && (!pos.is_draw() || ply < 2))
2476 pv[ply] = tte->move();
2477 pos.do_move(pv[ply++], *st++);
2479 pv[ply] = MOVE_NONE;
2481 do pos.undo_move(pv[--ply]); while (ply);
2484 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2485 // the PV back into the TT. This makes sure the old PV moves are searched
2486 // first, even if the old TT entries have been overwritten.
2488 void RootMove::insert_pv_in_tt(Position& pos) {
2490 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2493 Value v, m = VALUE_NONE;
2496 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2500 tte = TT.retrieve(k);
2502 // Don't overwrite existing correct entries
2503 if (!tte || tte->move() != pv[ply])
2505 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2506 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2508 pos.do_move(pv[ply], *st++);
2510 } while (pv[++ply] != MOVE_NONE);
2512 do pos.undo_move(pv[--ply]); while (ply);
2515 // pv_info_to_uci() returns a string with information on the current PV line
2516 // formatted according to UCI specification. It is called at each iteration
2517 // or after a new pv is found.
2519 std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
2521 std::stringstream s, l;
2524 while (*m != MOVE_NONE)
2527 s << "info depth " << depth
2528 << " seldepth " << int(m - pv)
2529 << " multipv " << pvLine + 1
2530 << " score " << value_to_uci(pv_score)
2531 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2532 << speed_to_uci(pos.nodes_searched())
2533 << " pv " << l.str();
2539 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2541 MoveStack mlist[MOVES_MAX];
2545 bestMoveChanges = 0;
2547 // Generate all legal moves and add them to RootMoveList
2548 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2549 for (MoveStack* cur = mlist; cur != last; cur++)
2551 // If we have a searchMoves[] list then verify cur->move
2552 // is in the list before to add it.
2553 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2555 if (searchMoves[0] && *sm != cur->move)
2559 rm.pv[0] = cur->move;
2560 rm.pv[1] = MOVE_NONE;
2561 rm.pv_score = -VALUE_INFINITE;