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 connected_threat(const Position& pos, Move m, Move threat);
301 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
302 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
303 void update_killers(Move m, Move killers[]);
304 void update_gains(const Position& pos, Move move, Value before, Value after);
305 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last);
307 int current_search_time();
308 std::string value_to_uci(Value v);
309 int nps(const Position& pos);
310 void poll(const Position& pos);
311 void wait_for_stop_or_ponderhit();
313 #if !defined(_MSC_VER)
314 void* init_thread(void* threadID);
316 DWORD WINAPI init_thread(LPVOID threadID);
320 // MovePickerExt is an extended MovePicker used to choose at compile time
321 // the proper move source according to the type of node.
322 template<bool SpNode, bool Root> struct MovePickerExt;
324 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
325 // before to search them.
326 template<> struct MovePickerExt<false, true> : public MovePicker {
328 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
329 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
331 Value score = VALUE_ZERO;
333 // Score root moves using the standard way used in main search, the moves
334 // are scored according to the order in which are returned by MovePicker.
335 // This is the second order score that is used to compare the moves when
336 // the first order pv scores of both moves are equal.
337 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
338 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
339 if (rm->pv[0] == move)
341 rm->non_pv_score = score--;
349 Move get_next_move() {
356 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
359 RootMoveList::iterator rm;
363 // In SpNodes use split point's shared MovePicker object as move source
364 template<> struct MovePickerExt<true, false> : public MovePicker {
366 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
367 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
370 Move get_next_move() { return mp->get_next_move(); }
372 RootMoveList::iterator rm; // Dummy, needed to compile
376 // Default case, create and use a MovePicker object as source
377 template<> struct MovePickerExt<false, false> : public MovePicker {
379 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
380 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
382 RootMoveList::iterator rm; // Dummy, needed to compile
392 /// init_threads(), exit_threads() and nodes_searched() are helpers to
393 /// give accessibility to some TM methods from outside of current file.
395 void init_threads() { ThreadsMgr.init_threads(); }
396 void exit_threads() { ThreadsMgr.exit_threads(); }
399 /// init_search() is called during startup. It initializes various lookup tables
403 int d; // depth (ONE_PLY == 2)
404 int hd; // half depth (ONE_PLY == 1)
407 // Init reductions array
408 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
410 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
411 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
412 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
413 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
416 // Init futility margins array
417 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
418 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
420 // Init futility move count array
421 for (d = 0; d < 32; d++)
422 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
426 /// perft() is our utility to verify move generation is bug free. All the legal
427 /// moves up to given depth are generated and counted and the sum returned.
429 int64_t perft(Position& pos, Depth depth)
431 MoveStack mlist[MOVES_MAX];
436 // Generate all legal moves
437 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
439 // If we are at the last ply we don't need to do and undo
440 // the moves, just to count them.
441 if (depth <= ONE_PLY)
442 return int(last - mlist);
444 // Loop through all legal moves
446 for (MoveStack* cur = mlist; cur != last; cur++)
449 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
450 sum += perft(pos, depth - ONE_PLY);
457 /// think() is the external interface to Stockfish's search, and is called when
458 /// the program receives the UCI 'go' command. It initializes various
459 /// search-related global variables, and calls id_loop(). It returns false
460 /// when a quit command is received during the search.
462 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
463 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
465 // Initialize global search variables
466 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
468 SearchStartTime = get_system_time();
469 ExactMaxTime = maxTime;
472 InfiniteSearch = infinite;
474 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
476 // Look for a book move, only during games, not tests
477 if (UseTimeManagement && Options["OwnBook"].value<bool>())
479 if (Options["Book File"].value<std::string>() != OpeningBook.name())
480 OpeningBook.open(Options["Book File"].value<std::string>());
482 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
483 if (bookMove != MOVE_NONE)
486 wait_for_stop_or_ponderhit();
488 cout << "bestmove " << bookMove << endl;
493 // Read UCI option values
494 TT.set_size(Options["Hash"].value<int>());
495 if (Options["Clear Hash"].value<bool>())
497 Options["Clear Hash"].set_value("false");
501 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
502 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
503 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
504 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
505 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
506 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
507 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
508 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
509 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
510 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
511 MultiPV = Options["MultiPV"].value<int>();
512 UseLogFile = Options["Use Search Log"].value<bool>();
514 read_evaluation_uci_options(pos.side_to_move());
516 // Set the number of active threads
517 ThreadsMgr.read_uci_options();
518 init_eval(ThreadsMgr.active_threads());
520 // Wake up needed threads
521 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
522 ThreadsMgr.wake_sleeping_thread(i);
525 int myTime = time[pos.side_to_move()];
526 int myIncrement = increment[pos.side_to_move()];
527 if (UseTimeManagement)
528 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
530 // Set best NodesBetweenPolls interval to avoid lagging under
531 // heavy time pressure.
533 NodesBetweenPolls = Min(MaxNodes, 30000);
534 else if (myTime && myTime < 1000)
535 NodesBetweenPolls = 1000;
536 else if (myTime && myTime < 5000)
537 NodesBetweenPolls = 5000;
539 NodesBetweenPolls = 30000;
541 // Write search information to log file
544 std::string name = Options["Search Log Filename"].value<std::string>();
545 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
547 LogFile << "Searching: " << pos.to_fen()
548 << "\ninfinite: " << infinite
549 << " ponder: " << ponder
550 << " time: " << myTime
551 << " increment: " << myIncrement
552 << " moves to go: " << movesToGo << endl;
555 // We're ready to start thinking. Call the iterative deepening loop function
556 Move ponderMove = MOVE_NONE;
557 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
559 // Print final search statistics
560 cout << "info nodes " << pos.nodes_searched()
561 << " nps " << nps(pos)
562 << " time " << current_search_time() << endl;
566 LogFile << "\nNodes: " << pos.nodes_searched()
567 << "\nNodes/second: " << nps(pos)
568 << "\nBest move: " << move_to_san(pos, bestMove);
571 pos.do_move(bestMove, st);
572 LogFile << "\nPonder move: "
573 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
576 // Return from think() with unchanged position
577 pos.undo_move(bestMove);
582 // This makes all the threads to go to sleep
583 ThreadsMgr.set_active_threads(1);
585 // If we are pondering or in infinite search, we shouldn't print the
586 // best move before we are told to do so.
587 if (!StopRequest && (Pondering || InfiniteSearch))
588 wait_for_stop_or_ponderhit();
590 // Could be both MOVE_NONE when searching on a stalemate position
591 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
599 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
600 // with increasing depth until the allocated thinking time has been consumed,
601 // user stops the search, or the maximum search depth is reached.
603 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
605 SearchStack ss[PLY_MAX_PLUS_2];
606 Value bestValues[PLY_MAX_PLUS_2];
607 int bestMoveChanges[PLY_MAX_PLUS_2];
608 int iteration, researchCountFL, researchCountFH, aspirationDelta;
609 Value value, alpha, beta;
611 Move bestMove, easyMove;
613 // Moves to search are verified, scored and sorted
614 Rml.init(pos, searchMoves);
616 // Initialize FIXME move before Rml.init()
619 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
620 *ponderMove = bestMove = easyMove = MOVE_NONE;
621 iteration = aspirationDelta = 0;
622 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
623 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
625 // Handle special case of searching on a mate/stale position
628 cout << "info depth 0 score "
629 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
635 // Is one move significantly better than others after initial scoring ?
637 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
638 easyMove = Rml[0].pv[0];
640 // Iterative deepening loop
641 while (++iteration <= PLY_MAX && !StopRequest)
643 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
644 depth = iteration * ONE_PLY;
646 if (MaxDepth && depth > MaxDepth * ONE_PLY)
649 cout << "info depth " << depth / ONE_PLY << endl;
651 // Calculate dynamic aspiration window based on previous iterations
652 if (MultiPV == 1 && iteration >= 5 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
654 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
655 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
657 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
658 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
660 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
661 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
664 // Start with a small aspiration window and, in case of fail high/low,
665 // research with bigger window until not failing high/low anymore.
668 // Search starting from ss+1 to allow calling update_gains()
669 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
671 // Send PV line to GUI and write to transposition table in case the
672 // relevant entries have been overwritten during the search.
673 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
675 Rml[i].insert_pv_in_tt(pos);
676 cout << set960(pos.is_chess960())
677 << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
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 > 4 && 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, while at non-PV nodes we check for
843 // and return a fail high/low. Biggest advantage at probing at PV nodes is
844 // to have a smooth experience in analysis mode.
847 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
848 : ok_to_use_TT(tte, depth, beta, ply)))
851 ss->bestMove = ttMove; // Can be MOVE_NONE
852 return value_from_tt(tte->value(), ply);
855 // Step 5. Evaluate the position statically and
856 // update gain statistics of parent move.
858 ss->eval = ss->evalMargin = VALUE_NONE;
861 assert(tte->static_value() != VALUE_NONE);
863 ss->eval = tte->static_value();
864 ss->evalMargin = tte->static_value_margin();
865 refinedValue = refine_eval(tte, ss->eval, ply);
869 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
870 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
873 // Save gain for the parent non-capture move
874 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
876 // Step 6. Razoring (is omitted in PV nodes)
878 && depth < RazorDepth
880 && refinedValue < beta - razor_margin(depth)
881 && ttMove == MOVE_NONE
882 && !value_is_mate(beta)
883 && !pos.has_pawn_on_7th(pos.side_to_move()))
885 Value rbeta = beta - razor_margin(depth);
886 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
888 // Logically we should return (v + razor_margin(depth)), but
889 // surprisingly this did slightly weaker in tests.
893 // Step 7. Static null move pruning (is omitted in PV nodes)
894 // We're betting that the opponent doesn't have a move that will reduce
895 // the score by more than futility_margin(depth) if we do a null move.
898 && depth < RazorDepth
900 && refinedValue >= beta + futility_margin(depth, 0)
901 && !value_is_mate(beta)
902 && pos.non_pawn_material(pos.side_to_move()))
903 return refinedValue - futility_margin(depth, 0);
905 // Step 8. Null move search with verification search (is omitted in PV nodes)
910 && refinedValue >= beta
911 && !value_is_mate(beta)
912 && pos.non_pawn_material(pos.side_to_move()))
914 ss->currentMove = MOVE_NULL;
916 // Null move dynamic reduction based on depth
917 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
919 // Null move dynamic reduction based on value
920 if (refinedValue - beta > PawnValueMidgame)
923 pos.do_null_move(st);
924 (ss+1)->skipNullMove = true;
925 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
926 (ss+1)->skipNullMove = false;
927 pos.undo_null_move();
929 if (nullValue >= beta)
931 // Do not return unproven mate scores
932 if (nullValue >= value_mate_in(PLY_MAX))
935 if (depth < 6 * ONE_PLY)
938 // Do verification search at high depths
939 ss->skipNullMove = true;
940 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
941 ss->skipNullMove = false;
948 // The null move failed low, which means that we may be faced with
949 // some kind of threat. If the previous move was reduced, check if
950 // the move that refuted the null move was somehow connected to the
951 // move which was reduced. If a connection is found, return a fail
952 // low score (which will cause the reduced move to fail high in the
953 // parent node, which will trigger a re-search with full depth).
954 if (nullValue == value_mated_in(ply + 2))
957 threatMove = (ss+1)->bestMove;
958 if ( depth < ThreatDepth
960 && threatMove != MOVE_NONE
961 && connected_moves(pos, (ss-1)->currentMove, threatMove))
966 // Step 9. Internal iterative deepening
967 if ( depth >= IIDDepth[PvNode]
968 && ttMove == MOVE_NONE
969 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
971 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
973 ss->skipNullMove = true;
974 search<PvNode>(pos, ss, alpha, beta, d, ply);
975 ss->skipNullMove = false;
977 ttMove = ss->bestMove;
978 tte = TT.retrieve(posKey);
981 // Expensive mate threat detection (only for PV nodes)
983 mateThreat = pos.has_mate_threat();
985 split_point_start: // At split points actual search starts from here
987 // Initialize a MovePicker object for the current position
988 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
990 ss->bestMove = MOVE_NONE;
991 futilityBase = ss->eval + ss->evalMargin;
992 singularExtensionNode = !Root
994 && depth >= SingularExtensionDepth[PvNode]
997 && !excludedMove // Do not allow recursive singular extension search
998 && (tte->type() & VALUE_TYPE_LOWER)
999 && tte->depth() >= depth - 3 * ONE_PLY;
1002 lock_grab(&(sp->lock));
1003 bestValue = sp->bestValue;
1006 // Step 10. Loop through moves
1007 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1008 while ( bestValue < beta
1009 && (move = mp.get_next_move()) != MOVE_NONE
1010 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1012 assert(move_is_ok(move));
1016 moveCount = ++sp->moveCount;
1017 lock_release(&(sp->lock));
1019 else if (move == excludedMove)
1026 // This is used by time management
1027 FirstRootMove = (moveCount == 1);
1029 // Save the current node count before the move is searched
1030 nodes = pos.nodes_searched();
1032 // If it's time to send nodes info, do it here where we have the
1033 // correct accumulated node counts searched by each thread.
1034 if (SendSearchedNodes)
1036 SendSearchedNodes = false;
1037 cout << "info nodes " << nodes
1038 << " nps " << nps(pos)
1039 << " time " << current_search_time() << endl;
1042 if (current_search_time() >= 1000)
1043 cout << "info currmove " << move
1044 << " currmovenumber " << moveCount << endl;
1047 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1048 moveIsCheck = pos.move_is_check(move, ci);
1049 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1051 // Step 11. Decide the new search depth
1052 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1054 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1055 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1056 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1057 // lower then ttValue minus a margin then we extend ttMove.
1058 if ( singularExtensionNode
1059 && move == tte->move()
1062 Value ttValue = value_from_tt(tte->value(), ply);
1064 if (abs(ttValue) < VALUE_KNOWN_WIN)
1066 Value b = ttValue - SingularExtensionMargin;
1067 ss->excludedMove = move;
1068 ss->skipNullMove = true;
1069 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1070 ss->skipNullMove = false;
1071 ss->excludedMove = MOVE_NONE;
1072 ss->bestMove = MOVE_NONE;
1078 // Update current move (this must be done after singular extension search)
1079 ss->currentMove = move;
1080 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1082 // Step 12. Futility pruning (is omitted in PV nodes)
1084 && !captureOrPromotion
1088 && !move_is_castle(move))
1090 // Move count based pruning
1091 if ( moveCount >= futility_move_count(depth)
1092 && !(threatMove && connected_threat(pos, move, threatMove))
1093 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1096 lock_grab(&(sp->lock));
1101 // Value based pruning
1102 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1103 // but fixing this made program slightly weaker.
1104 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1105 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1106 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1108 if (futilityValueScaled < beta)
1112 lock_grab(&(sp->lock));
1113 if (futilityValueScaled > sp->bestValue)
1114 sp->bestValue = bestValue = futilityValueScaled;
1116 else if (futilityValueScaled > bestValue)
1117 bestValue = futilityValueScaled;
1122 // Prune moves with negative SEE at low depths
1123 if ( predictedDepth < 2 * ONE_PLY
1124 && bestValue > value_mated_in(PLY_MAX)
1125 && pos.see_sign(move) < 0)
1128 lock_grab(&(sp->lock));
1134 // Step 13. Make the move
1135 pos.do_move(move, st, ci, moveIsCheck);
1137 if (!SpNode && !captureOrPromotion)
1138 movesSearched[playedMoveCount++] = move;
1140 // Step extra. pv search (only in PV nodes)
1141 // The first move in list is the expected PV
1144 // Aspiration window is disabled in multi-pv case
1145 if (Root && MultiPV > 1)
1146 alpha = -VALUE_INFINITE;
1148 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1152 // Step 14. Reduced depth search
1153 // If the move fails high will be re-searched at full depth.
1154 bool doFullDepthSearch = true;
1156 if ( depth >= 3 * ONE_PLY
1157 && !captureOrPromotion
1159 && !move_is_castle(move)
1160 && ss->killers[0] != move
1161 && ss->killers[1] != move)
1163 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1164 : reduction<PvNode>(depth, moveCount);
1167 alpha = SpNode ? sp->alpha : alpha;
1168 Depth d = newDepth - ss->reduction;
1169 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1171 doFullDepthSearch = (value > alpha);
1173 ss->reduction = DEPTH_ZERO; // Restore original reduction
1176 // Step 15. Full depth search
1177 if (doFullDepthSearch)
1179 alpha = SpNode ? sp->alpha : alpha;
1180 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1182 // Step extra. pv search (only in PV nodes)
1183 // Search only for possible new PV nodes, if instead value >= beta then
1184 // parent node fails low with value <= alpha and tries another move.
1185 if (PvNode && value > alpha && (Root || value < beta))
1186 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1190 // Step 16. Undo move
1191 pos.undo_move(move);
1193 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1195 // Step 17. Check for new best move
1198 lock_grab(&(sp->lock));
1199 bestValue = sp->bestValue;
1203 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1208 sp->bestValue = value;
1212 if (PvNode && value < beta) // We want always alpha < beta
1220 sp->betaCutoff = true;
1222 if (value == value_mate_in(ply + 1))
1223 ss->mateKiller = move;
1225 ss->bestMove = move;
1228 sp->parentSstack->bestMove = move;
1234 // To avoid to exit with bestValue == -VALUE_INFINITE
1235 if (value > bestValue)
1238 // Finished searching the move. If StopRequest is true, the search
1239 // was aborted because the user interrupted the search or because we
1240 // ran out of time. In this case, the return value of the search cannot
1241 // be trusted, and we break out of the loop without updating the best
1246 // Remember searched nodes counts for this move
1247 mp.rm->nodes += pos.nodes_searched() - nodes;
1249 // Step 17. Check for new best move
1250 if (!isPvMove && value <= alpha)
1251 mp.rm->pv_score = -VALUE_INFINITE;
1254 // PV move or new best move!
1257 ss->bestMove = move;
1258 mp.rm->pv_score = value;
1259 mp.rm->extract_pv_from_tt(pos);
1261 // We record how often the best move has been changed in each
1262 // iteration. This information is used for time managment: When
1263 // the best move changes frequently, we allocate some more time.
1264 if (!isPvMove && MultiPV == 1)
1265 Rml.bestMoveChanges++;
1267 Rml.sort_multipv(moveCount);
1269 // Update alpha. In multi-pv we don't use aspiration window, so
1270 // set alpha equal to minimum score among the PV lines.
1272 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1273 else if (value > alpha)
1276 } // PV move or new best move
1279 // Step 18. Check for split
1282 && depth >= ThreadsMgr.min_split_depth()
1283 && ThreadsMgr.active_threads() > 1
1285 && ThreadsMgr.available_thread_exists(threadID)
1287 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1288 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1289 threatMove, mateThreat, moveCount, &mp, PvNode);
1292 // Step 19. Check for mate and stalemate
1293 // All legal moves have been searched and if there are
1294 // no legal moves, it must be mate or stalemate.
1295 // If one move was excluded return fail low score.
1296 if (!SpNode && !moveCount)
1297 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1299 // Step 20. Update tables
1300 // If the search is not aborted, update the transposition table,
1301 // history counters, and killer moves.
1302 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1304 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1305 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1306 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1308 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1310 // Update killers and history only for non capture moves that fails high
1311 if ( bestValue >= beta
1312 && !pos.move_is_capture_or_promotion(move))
1314 update_history(pos, move, depth, movesSearched, playedMoveCount);
1315 update_killers(move, ss->killers);
1321 // Here we have the lock still grabbed
1322 sp->slaves[threadID] = 0;
1323 sp->nodes += pos.nodes_searched();
1324 lock_release(&(sp->lock));
1327 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1332 // qsearch() is the quiescence search function, which is called by the main
1333 // search function when the remaining depth is zero (or, to be more precise,
1334 // less than ONE_PLY).
1336 template <NodeType PvNode>
1337 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1339 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1340 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1341 assert(PvNode || alpha == beta - 1);
1343 assert(ply > 0 && ply < PLY_MAX);
1344 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1348 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1349 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1352 Value oldAlpha = alpha;
1354 ss->bestMove = ss->currentMove = MOVE_NONE;
1356 // Check for an instant draw or maximum ply reached
1357 if (pos.is_draw() || ply >= PLY_MAX - 1)
1360 // Decide whether or not to include checks, this fixes also the type of
1361 // TT entry depth that we are going to use. Note that in qsearch we use
1362 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1363 isCheck = pos.is_check();
1364 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1366 // Transposition table lookup. At PV nodes, we don't use the TT for
1367 // pruning, but only for move ordering.
1368 tte = TT.retrieve(pos.get_key());
1369 ttMove = (tte ? tte->move() : MOVE_NONE);
1371 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1373 ss->bestMove = ttMove; // Can be MOVE_NONE
1374 return value_from_tt(tte->value(), ply);
1377 // Evaluate the position statically
1380 bestValue = futilityBase = -VALUE_INFINITE;
1381 ss->eval = evalMargin = VALUE_NONE;
1382 enoughMaterial = false;
1388 assert(tte->static_value() != VALUE_NONE);
1390 evalMargin = tte->static_value_margin();
1391 ss->eval = bestValue = tte->static_value();
1394 ss->eval = bestValue = evaluate(pos, evalMargin);
1396 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1398 // Stand pat. Return immediately if static value is at least beta
1399 if (bestValue >= beta)
1402 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1407 if (PvNode && bestValue > alpha)
1410 // Futility pruning parameters, not needed when in check
1411 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1412 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1415 // Initialize a MovePicker object for the current position, and prepare
1416 // to search the moves. Because the depth is <= 0 here, only captures,
1417 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1419 MovePicker mp(pos, ttMove, depth, H);
1422 // Loop through the moves until no moves remain or a beta cutoff occurs
1423 while ( alpha < beta
1424 && (move = mp.get_next_move()) != MOVE_NONE)
1426 assert(move_is_ok(move));
1428 moveIsCheck = pos.move_is_check(move, ci);
1436 && !move_is_promotion(move)
1437 && !pos.move_is_passed_pawn_push(move))
1439 futilityValue = futilityBase
1440 + pos.endgame_value_of_piece_on(move_to(move))
1441 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1443 if (futilityValue < alpha)
1445 if (futilityValue > bestValue)
1446 bestValue = futilityValue;
1451 // Detect non-capture evasions that are candidate to be pruned
1452 evasionPrunable = isCheck
1453 && bestValue > value_mated_in(PLY_MAX)
1454 && !pos.move_is_capture(move)
1455 && !pos.can_castle(pos.side_to_move());
1457 // Don't search moves with negative SEE values
1459 && (!isCheck || evasionPrunable)
1461 && !move_is_promotion(move)
1462 && pos.see_sign(move) < 0)
1465 // Don't search useless checks
1470 && !pos.move_is_capture_or_promotion(move)
1471 && ss->eval + PawnValueMidgame / 4 < beta
1472 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1474 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1475 bestValue = ss->eval + PawnValueMidgame / 4;
1480 // Update current move
1481 ss->currentMove = move;
1483 // Make and search the move
1484 pos.do_move(move, st, ci, moveIsCheck);
1485 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1486 pos.undo_move(move);
1488 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1491 if (value > bestValue)
1497 ss->bestMove = move;
1502 // All legal moves have been searched. A special case: If we're in check
1503 // and no legal moves were found, it is checkmate.
1504 if (isCheck && bestValue == -VALUE_INFINITE)
1505 return value_mated_in(ply);
1507 // Update transposition table
1508 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1509 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1511 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1517 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1518 // it is used in RootMoveList to get an initial scoring.
1519 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1521 SearchStack ss[PLY_MAX_PLUS_2];
1524 memset(ss, 0, 4 * sizeof(SearchStack));
1525 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1527 for (MoveStack* cur = mlist; cur != last; cur++)
1529 ss[0].currentMove = cur->move;
1530 pos.do_move(cur->move, st);
1531 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1532 pos.undo_move(cur->move);
1537 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1538 // bestValue is updated only when returning false because in that case move
1541 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1543 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1544 Square from, to, ksq, victimSq;
1547 Value futilityValue, bv = *bestValue;
1549 from = move_from(move);
1551 them = opposite_color(pos.side_to_move());
1552 ksq = pos.king_square(them);
1553 kingAtt = pos.attacks_from<KING>(ksq);
1554 pc = pos.piece_on(from);
1556 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1557 oldAtt = pos.attacks_from(pc, from, occ);
1558 newAtt = pos.attacks_from(pc, to, occ);
1560 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1561 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1563 if (!(b && (b & (b - 1))))
1566 // Rule 2. Queen contact check is very dangerous
1567 if ( type_of_piece(pc) == QUEEN
1568 && bit_is_set(kingAtt, to))
1571 // Rule 3. Creating new double threats with checks
1572 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1576 victimSq = pop_1st_bit(&b);
1577 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1579 // Note that here we generate illegal "double move"!
1580 if ( futilityValue >= beta
1581 && pos.see_sign(make_move(from, victimSq)) >= 0)
1584 if (futilityValue > bv)
1588 // Update bestValue only if check is not dangerous (because we will prune the move)
1594 // connected_moves() tests whether two moves are 'connected' in the sense
1595 // that the first move somehow made the second move possible (for instance
1596 // if the moving piece is the same in both moves). The first move is assumed
1597 // to be the move that was made to reach the current position, while the
1598 // second move is assumed to be a move from the current position.
1600 bool connected_moves(const Position& pos, Move m1, Move m2) {
1602 Square f1, t1, f2, t2;
1605 assert(m1 && move_is_ok(m1));
1606 assert(m2 && move_is_ok(m2));
1608 // Case 1: The moving piece is the same in both moves
1614 // Case 2: The destination square for m2 was vacated by m1
1620 // Case 3: Moving through the vacated square
1621 if ( piece_is_slider(pos.piece_on(f2))
1622 && bit_is_set(squares_between(f2, t2), f1))
1625 // Case 4: The destination square for m2 is defended by the moving piece in m1
1626 p = pos.piece_on(t1);
1627 if (bit_is_set(pos.attacks_from(p, t1), t2))
1630 // Case 5: Discovered check, checking piece is the piece moved in m1
1631 if ( piece_is_slider(p)
1632 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1633 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1635 // discovered_check_candidates() works also if the Position's side to
1636 // move is the opposite of the checking piece.
1637 Color them = opposite_color(pos.side_to_move());
1638 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1640 if (bit_is_set(dcCandidates, f2))
1647 // value_is_mate() checks if the given value is a mate one eventually
1648 // compensated for the ply.
1650 bool value_is_mate(Value value) {
1652 assert(abs(value) <= VALUE_INFINITE);
1654 return value <= value_mated_in(PLY_MAX)
1655 || value >= value_mate_in(PLY_MAX);
1659 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1660 // "plies to mate from the current ply". Non-mate scores are unchanged.
1661 // The function is called before storing a value to the transposition table.
1663 Value value_to_tt(Value v, int ply) {
1665 if (v >= value_mate_in(PLY_MAX))
1668 if (v <= value_mated_in(PLY_MAX))
1675 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1676 // the transposition table to a mate score corrected for the current ply.
1678 Value value_from_tt(Value v, int ply) {
1680 if (v >= value_mate_in(PLY_MAX))
1683 if (v <= value_mated_in(PLY_MAX))
1690 // extension() decides whether a move should be searched with normal depth,
1691 // or with extended depth. Certain classes of moves (checking moves, in
1692 // particular) are searched with bigger depth than ordinary moves and in
1693 // any case are marked as 'dangerous'. Note that also if a move is not
1694 // extended, as example because the corresponding UCI option is set to zero,
1695 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1696 template <NodeType PvNode>
1697 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1698 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1700 assert(m != MOVE_NONE);
1702 Depth result = DEPTH_ZERO;
1703 *dangerous = moveIsCheck | mateThreat;
1707 if (moveIsCheck && pos.see_sign(m) >= 0)
1708 result += CheckExtension[PvNode];
1711 result += MateThreatExtension[PvNode];
1714 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1716 Color c = pos.side_to_move();
1717 if (relative_rank(c, move_to(m)) == RANK_7)
1719 result += PawnPushTo7thExtension[PvNode];
1722 if (pos.pawn_is_passed(c, move_to(m)))
1724 result += PassedPawnExtension[PvNode];
1729 if ( captureOrPromotion
1730 && pos.type_of_piece_on(move_to(m)) != PAWN
1731 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1732 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1733 && !move_is_promotion(m)
1736 result += PawnEndgameExtension[PvNode];
1741 && captureOrPromotion
1742 && pos.type_of_piece_on(move_to(m)) != PAWN
1743 && pos.see_sign(m) >= 0)
1745 result += ONE_PLY / 2;
1749 return Min(result, ONE_PLY);
1753 // connected_threat() tests whether it is safe to forward prune a move or if
1754 // is somehow coonected to the threat move returned by null search.
1756 bool connected_threat(const Position& pos, Move m, Move threat) {
1758 assert(move_is_ok(m));
1759 assert(threat && move_is_ok(threat));
1760 assert(!pos.move_is_check(m));
1761 assert(!pos.move_is_capture_or_promotion(m));
1762 assert(!pos.move_is_passed_pawn_push(m));
1764 Square mfrom, mto, tfrom, tto;
1766 mfrom = move_from(m);
1768 tfrom = move_from(threat);
1769 tto = move_to(threat);
1771 // Case 1: Don't prune moves which move the threatened piece
1775 // Case 2: If the threatened piece has value less than or equal to the
1776 // value of the threatening piece, don't prune move which defend it.
1777 if ( pos.move_is_capture(threat)
1778 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1779 || pos.type_of_piece_on(tfrom) == KING)
1780 && pos.move_attacks_square(m, tto))
1783 // Case 3: If the moving piece in the threatened move is a slider, don't
1784 // prune safe moves which block its ray.
1785 if ( piece_is_slider(pos.piece_on(tfrom))
1786 && bit_is_set(squares_between(tfrom, tto), mto)
1787 && pos.see_sign(m) >= 0)
1794 // ok_to_use_TT() returns true if a transposition table score
1795 // can be used at a given point in search.
1797 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1799 Value v = value_from_tt(tte->value(), ply);
1801 return ( tte->depth() >= depth
1802 || v >= Max(value_mate_in(PLY_MAX), beta)
1803 || v < Min(value_mated_in(PLY_MAX), beta))
1805 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1806 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1810 // refine_eval() returns the transposition table score if
1811 // possible otherwise falls back on static position evaluation.
1813 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1817 Value v = value_from_tt(tte->value(), ply);
1819 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1820 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1827 // update_history() registers a good move that produced a beta-cutoff
1828 // in history and marks as failures all the other moves of that ply.
1830 void update_history(const Position& pos, Move move, Depth depth,
1831 Move movesSearched[], int moveCount) {
1833 Value bonus = Value(int(depth) * int(depth));
1835 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1837 for (int i = 0; i < moveCount - 1; i++)
1839 m = movesSearched[i];
1843 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1848 // update_killers() add a good move that produced a beta-cutoff
1849 // among the killer moves of that ply.
1851 void update_killers(Move m, Move killers[]) {
1853 if (m != killers[0])
1855 killers[1] = killers[0];
1861 // update_gains() updates the gains table of a non-capture move given
1862 // the static position evaluation before and after the move.
1864 void update_gains(const Position& pos, Move m, Value before, Value after) {
1867 && before != VALUE_NONE
1868 && after != VALUE_NONE
1869 && pos.captured_piece_type() == PIECE_TYPE_NONE
1870 && !move_is_special(m))
1871 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1875 // value_to_uci() converts a value to a string suitable for use with the UCI
1876 // protocol specifications:
1878 // cp <x> The score from the engine's point of view in centipawns.
1879 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1880 // use negative values for y.
1882 std::string value_to_uci(Value v) {
1884 std::stringstream s;
1886 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1887 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1889 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1895 // current_search_time() returns the number of milliseconds which have passed
1896 // since the beginning of the current search.
1898 int current_search_time() {
1900 return get_system_time() - SearchStartTime;
1904 // nps() computes the current nodes/second count
1906 int nps(const Position& pos) {
1908 int t = current_search_time();
1909 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1913 // poll() performs two different functions: It polls for user input, and it
1914 // looks at the time consumed so far and decides if it's time to abort the
1917 void poll(const Position& pos) {
1919 static int lastInfoTime;
1920 int t = current_search_time();
1923 if (input_available())
1925 // We are line oriented, don't read single chars
1926 std::string command;
1928 if (!std::getline(std::cin, command))
1931 if (command == "quit")
1933 // Quit the program as soon as possible
1935 QuitRequest = StopRequest = true;
1938 else if (command == "stop")
1940 // Stop calculating as soon as possible, but still send the "bestmove"
1941 // and possibly the "ponder" token when finishing the search.
1945 else if (command == "ponderhit")
1947 // The opponent has played the expected move. GUI sends "ponderhit" if
1948 // we were told to ponder on the same move the opponent has played. We
1949 // should continue searching but switching from pondering to normal search.
1952 if (StopOnPonderhit)
1957 // Print search information
1961 else if (lastInfoTime > t)
1962 // HACK: Must be a new search where we searched less than
1963 // NodesBetweenPolls nodes during the first second of search.
1966 else if (t - lastInfoTime >= 1000)
1973 if (dbg_show_hit_rate)
1974 dbg_print_hit_rate();
1976 // Send info on searched nodes as soon as we return to root
1977 SendSearchedNodes = true;
1980 // Should we stop the search?
1984 bool stillAtFirstMove = FirstRootMove
1985 && !AspirationFailLow
1986 && t > TimeMgr.available_time();
1988 bool noMoreTime = t > TimeMgr.maximum_time()
1989 || stillAtFirstMove;
1991 if ( (UseTimeManagement && noMoreTime)
1992 || (ExactMaxTime && t >= ExactMaxTime)
1993 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1998 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1999 // while the program is pondering. The point is to work around a wrinkle in
2000 // the UCI protocol: When pondering, the engine is not allowed to give a
2001 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2002 // We simply wait here until one of these commands is sent, and return,
2003 // after which the bestmove and pondermove will be printed.
2005 void wait_for_stop_or_ponderhit() {
2007 std::string command;
2011 // Wait for a command from stdin
2012 if (!std::getline(std::cin, command))
2015 if (command == "quit")
2020 else if (command == "ponderhit" || command == "stop")
2026 // init_thread() is the function which is called when a new thread is
2027 // launched. It simply calls the idle_loop() function with the supplied
2028 // threadID. There are two versions of this function; one for POSIX
2029 // threads and one for Windows threads.
2031 #if !defined(_MSC_VER)
2033 void* init_thread(void* threadID) {
2035 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2041 DWORD WINAPI init_thread(LPVOID threadID) {
2043 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2050 /// The ThreadsManager class
2053 // read_uci_options() updates number of active threads and other internal
2054 // parameters according to the UCI options values. It is called before
2055 // to start a new search.
2057 void ThreadsManager::read_uci_options() {
2059 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2060 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2061 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2062 activeThreads = Options["Threads"].value<int>();
2066 // idle_loop() is where the threads are parked when they have no work to do.
2067 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2068 // object for which the current thread is the master.
2070 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2072 assert(threadID >= 0 && threadID < MAX_THREADS);
2075 bool allFinished = false;
2079 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2080 // master should exit as last one.
2081 if (allThreadsShouldExit)
2084 threads[threadID].state = THREAD_TERMINATED;
2088 // If we are not thinking, wait for a condition to be signaled
2089 // instead of wasting CPU time polling for work.
2090 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2091 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2093 assert(!sp || useSleepingThreads);
2094 assert(threadID != 0 || useSleepingThreads);
2096 if (threads[threadID].state == THREAD_INITIALIZING)
2097 threads[threadID].state = THREAD_AVAILABLE;
2099 // Grab the lock to avoid races with wake_sleeping_thread()
2100 lock_grab(&sleepLock[threadID]);
2102 // If we are master and all slaves have finished do not go to sleep
2103 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2104 allFinished = (i == activeThreads);
2106 if (allFinished || allThreadsShouldExit)
2108 lock_release(&sleepLock[threadID]);
2112 // Do sleep here after retesting sleep conditions
2113 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2114 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2116 lock_release(&sleepLock[threadID]);
2119 // If this thread has been assigned work, launch a search
2120 if (threads[threadID].state == THREAD_WORKISWAITING)
2122 assert(!allThreadsShouldExit);
2124 threads[threadID].state = THREAD_SEARCHING;
2126 // Here we call search() with SplitPoint template parameter set to true
2127 SplitPoint* tsp = threads[threadID].splitPoint;
2128 Position pos(*tsp->pos, threadID);
2129 SearchStack* ss = tsp->sstack[threadID] + 1;
2133 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2135 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2137 assert(threads[threadID].state == THREAD_SEARCHING);
2139 threads[threadID].state = THREAD_AVAILABLE;
2141 // Wake up master thread so to allow it to return from the idle loop in
2142 // case we are the last slave of the split point.
2143 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2144 wake_sleeping_thread(tsp->master);
2147 // If this thread is the master of a split point and all slaves have
2148 // finished their work at this split point, return from the idle loop.
2149 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2150 allFinished = (i == activeThreads);
2154 // Because sp->slaves[] is reset under lock protection,
2155 // be sure sp->lock has been released before to return.
2156 lock_grab(&(sp->lock));
2157 lock_release(&(sp->lock));
2159 // In helpful master concept a master can help only a sub-tree, and
2160 // because here is all finished is not possible master is booked.
2161 assert(threads[threadID].state == THREAD_AVAILABLE);
2163 threads[threadID].state = THREAD_SEARCHING;
2170 // init_threads() is called during startup. It launches all helper threads,
2171 // and initializes the split point stack and the global locks and condition
2174 void ThreadsManager::init_threads() {
2176 int i, arg[MAX_THREADS];
2179 // Initialize global locks
2182 for (i = 0; i < MAX_THREADS; i++)
2184 lock_init(&sleepLock[i]);
2185 cond_init(&sleepCond[i]);
2188 // Initialize splitPoints[] locks
2189 for (i = 0; i < MAX_THREADS; i++)
2190 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2191 lock_init(&(threads[i].splitPoints[j].lock));
2193 // Will be set just before program exits to properly end the threads
2194 allThreadsShouldExit = false;
2196 // Threads will be put all threads to sleep as soon as created
2199 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2200 threads[0].state = THREAD_SEARCHING;
2201 for (i = 1; i < MAX_THREADS; i++)
2202 threads[i].state = THREAD_INITIALIZING;
2204 // Launch the helper threads
2205 for (i = 1; i < MAX_THREADS; i++)
2209 #if !defined(_MSC_VER)
2210 pthread_t pthread[1];
2211 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2212 pthread_detach(pthread[0]);
2214 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2218 cout << "Failed to create thread number " << i << endl;
2222 // Wait until the thread has finished launching and is gone to sleep
2223 while (threads[i].state == THREAD_INITIALIZING) {}
2228 // exit_threads() is called when the program exits. It makes all the
2229 // helper threads exit cleanly.
2231 void ThreadsManager::exit_threads() {
2233 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2235 // Wake up all the threads and waits for termination
2236 for (int i = 1; i < MAX_THREADS; i++)
2238 wake_sleeping_thread(i);
2239 while (threads[i].state != THREAD_TERMINATED) {}
2242 // Now we can safely destroy the locks
2243 for (int i = 0; i < MAX_THREADS; i++)
2244 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2245 lock_destroy(&(threads[i].splitPoints[j].lock));
2247 lock_destroy(&mpLock);
2249 // Now we can safely destroy the wait conditions
2250 for (int i = 0; i < MAX_THREADS; i++)
2252 lock_destroy(&sleepLock[i]);
2253 cond_destroy(&sleepCond[i]);
2258 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2259 // the thread's currently active split point, or in some ancestor of
2260 // the current split point.
2262 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2264 assert(threadID >= 0 && threadID < activeThreads);
2266 SplitPoint* sp = threads[threadID].splitPoint;
2268 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2273 // thread_is_available() checks whether the thread with threadID "slave" is
2274 // available to help the thread with threadID "master" at a split point. An
2275 // obvious requirement is that "slave" must be idle. With more than two
2276 // threads, this is not by itself sufficient: If "slave" is the master of
2277 // some active split point, it is only available as a slave to the other
2278 // threads which are busy searching the split point at the top of "slave"'s
2279 // split point stack (the "helpful master concept" in YBWC terminology).
2281 bool ThreadsManager::thread_is_available(int slave, int master) const {
2283 assert(slave >= 0 && slave < activeThreads);
2284 assert(master >= 0 && master < activeThreads);
2285 assert(activeThreads > 1);
2287 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2290 // Make a local copy to be sure doesn't change under our feet
2291 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2293 // No active split points means that the thread is available as
2294 // a slave for any other thread.
2295 if (localActiveSplitPoints == 0 || activeThreads == 2)
2298 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2299 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2300 // could have been set to 0 by another thread leading to an out of bound access.
2301 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2308 // available_thread_exists() tries to find an idle thread which is available as
2309 // a slave for the thread with threadID "master".
2311 bool ThreadsManager::available_thread_exists(int master) const {
2313 assert(master >= 0 && master < activeThreads);
2314 assert(activeThreads > 1);
2316 for (int i = 0; i < activeThreads; i++)
2317 if (thread_is_available(i, master))
2324 // split() does the actual work of distributing the work at a node between
2325 // several available threads. If it does not succeed in splitting the
2326 // node (because no idle threads are available, or because we have no unused
2327 // split point objects), the function immediately returns. If splitting is
2328 // possible, a SplitPoint object is initialized with all the data that must be
2329 // copied to the helper threads and we tell our helper threads that they have
2330 // been assigned work. This will cause them to instantly leave their idle loops and
2331 // call search().When all threads have returned from search() then split() returns.
2333 template <bool Fake>
2334 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2335 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2336 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2337 assert(pos.is_ok());
2338 assert(ply > 0 && ply < PLY_MAX);
2339 assert(*bestValue >= -VALUE_INFINITE);
2340 assert(*bestValue <= *alpha);
2341 assert(*alpha < beta);
2342 assert(beta <= VALUE_INFINITE);
2343 assert(depth > DEPTH_ZERO);
2344 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2345 assert(activeThreads > 1);
2347 int i, master = pos.thread();
2348 Thread& masterThread = threads[master];
2352 // If no other thread is available to help us, or if we have too many
2353 // active split points, don't split.
2354 if ( !available_thread_exists(master)
2355 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2357 lock_release(&mpLock);
2361 // Pick the next available split point object from the split point stack
2362 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2364 // Initialize the split point object
2365 splitPoint.parent = masterThread.splitPoint;
2366 splitPoint.master = master;
2367 splitPoint.betaCutoff = false;
2368 splitPoint.ply = ply;
2369 splitPoint.depth = depth;
2370 splitPoint.threatMove = threatMove;
2371 splitPoint.mateThreat = mateThreat;
2372 splitPoint.alpha = *alpha;
2373 splitPoint.beta = beta;
2374 splitPoint.pvNode = pvNode;
2375 splitPoint.bestValue = *bestValue;
2377 splitPoint.moveCount = moveCount;
2378 splitPoint.pos = &pos;
2379 splitPoint.nodes = 0;
2380 splitPoint.parentSstack = ss;
2381 for (i = 0; i < activeThreads; i++)
2382 splitPoint.slaves[i] = 0;
2384 masterThread.splitPoint = &splitPoint;
2386 // If we are here it means we are not available
2387 assert(masterThread.state != THREAD_AVAILABLE);
2389 int workersCnt = 1; // At least the master is included
2391 // Allocate available threads setting state to THREAD_BOOKED
2392 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2393 if (thread_is_available(i, master))
2395 threads[i].state = THREAD_BOOKED;
2396 threads[i].splitPoint = &splitPoint;
2397 splitPoint.slaves[i] = 1;
2401 assert(Fake || workersCnt > 1);
2403 // We can release the lock because slave threads are already booked and master is not available
2404 lock_release(&mpLock);
2406 // Tell the threads that they have work to do. This will make them leave
2407 // their idle loop. But before copy search stack tail for each thread.
2408 for (i = 0; i < activeThreads; i++)
2409 if (i == master || splitPoint.slaves[i])
2411 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2413 assert(i == master || threads[i].state == THREAD_BOOKED);
2415 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2417 if (useSleepingThreads && i != master)
2418 wake_sleeping_thread(i);
2421 // Everything is set up. The master thread enters the idle loop, from
2422 // which it will instantly launch a search, because its state is
2423 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2424 // idle loop, which means that the main thread will return from the idle
2425 // loop when all threads have finished their work at this split point.
2426 idle_loop(master, &splitPoint);
2428 // We have returned from the idle loop, which means that all threads are
2429 // finished. Update alpha and bestValue, and return.
2432 *alpha = splitPoint.alpha;
2433 *bestValue = splitPoint.bestValue;
2434 masterThread.activeSplitPoints--;
2435 masterThread.splitPoint = splitPoint.parent;
2436 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2438 lock_release(&mpLock);
2442 // wake_sleeping_thread() wakes up the thread with the given threadID
2443 // when it is time to start a new search.
2445 void ThreadsManager::wake_sleeping_thread(int threadID) {
2447 lock_grab(&sleepLock[threadID]);
2448 cond_signal(&sleepCond[threadID]);
2449 lock_release(&sleepLock[threadID]);
2453 /// RootMove and RootMoveList method's definitions
2455 RootMove::RootMove() {
2458 pv_score = non_pv_score = -VALUE_INFINITE;
2462 RootMove& RootMove::operator=(const RootMove& rm) {
2464 const Move* src = rm.pv;
2467 // Avoid a costly full rm.pv[] copy
2468 do *dst++ = *src; while (*src++ != MOVE_NONE);
2471 pv_score = rm.pv_score;
2472 non_pv_score = rm.non_pv_score;
2476 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2477 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2478 // allow to always have a ponder move even when we fail high at root and also a
2479 // long PV to print that is important for position analysis.
2481 void RootMove::extract_pv_from_tt(Position& pos) {
2483 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2487 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2489 pos.do_move(pv[0], *st++);
2491 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2492 && tte->move() != MOVE_NONE
2493 && move_is_legal(pos, tte->move())
2495 && (!pos.is_draw() || ply < 2))
2497 pv[ply] = tte->move();
2498 pos.do_move(pv[ply++], *st++);
2500 pv[ply] = MOVE_NONE;
2502 do pos.undo_move(pv[--ply]); while (ply);
2505 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2506 // the PV back into the TT. This makes sure the old PV moves are searched
2507 // first, even if the old TT entries have been overwritten.
2509 void RootMove::insert_pv_in_tt(Position& pos) {
2511 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2514 Value v, m = VALUE_NONE;
2517 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2521 tte = TT.retrieve(k);
2523 // Don't overwrite exsisting correct entries
2524 if (!tte || tte->move() != pv[ply])
2526 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2527 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2529 pos.do_move(pv[ply], *st++);
2531 } while (pv[++ply] != MOVE_NONE);
2533 do pos.undo_move(pv[--ply]); while (ply);
2536 // pv_info_to_uci() returns a string with information on the current PV line
2537 // formatted according to UCI specification and eventually writes the info
2538 // to a log file. It is called at each iteration or after a new pv is found.
2540 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2542 std::stringstream s, l;
2545 while (*m != MOVE_NONE)
2548 s << "info depth " << depth / ONE_PLY
2549 << " seldepth " << int(m - pv)
2550 << " multipv " << pvLine + 1
2551 << " score " << value_to_uci(pv_score)
2552 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2553 << " time " << current_search_time()
2554 << " nodes " << pos.nodes_searched()
2555 << " nps " << nps(pos)
2556 << " pv " << l.str();
2558 if (UseLogFile && pvLine == 0)
2560 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2561 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2563 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2569 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2571 MoveStack mlist[MOVES_MAX];
2575 bestMoveChanges = 0;
2577 // Generate all legal moves and score them
2578 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2579 qsearch_scoring(pos, mlist, last);
2581 // Add each move to the RootMoveList's vector
2582 for (MoveStack* cur = mlist; cur != last; cur++)
2584 // If we have a searchMoves[] list then verify cur->move
2585 // is in the list before to add it.
2586 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2588 if (searchMoves[0] && *sm != cur->move)
2592 rm.pv[0] = cur->move;
2593 rm.pv[1] = MOVE_NONE;
2594 rm.pv_score = Value(cur->score);