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 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
621 *ponderMove = bestMove = easyMove = MOVE_NONE;
624 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
626 // Handle special case of searching on a mate/stale position
629 cout << "info depth " << iteration << " score "
630 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
636 // Send initial scoring (iteration 1)
637 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
638 << "info depth " << iteration
639 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
641 // Is one move significantly better than others after initial scoring ?
643 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
644 easyMove = Rml[0].pv[0];
646 // Iterative deepening loop
647 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
649 cout << "info depth " << iteration << endl;
651 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
652 depth = (iteration - 1) * ONE_PLY;
654 // Calculate dynamic aspiration window based on previous iterations
655 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
657 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
658 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
660 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 64);
661 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
663 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
664 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
667 // Start with a small aspiration window and, in case of fail high/low,
668 // research with bigger window until not failing high/low anymore.
671 // Search starting from ss+1 to allow calling update_gains()
672 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
674 // Write PV lines to transposition table, in case the relevant entries
675 // have been overwritten during the search.
676 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
677 Rml[i].insert_pv_in_tt(pos);
679 // Value cannot be trusted. Break out immediately!
683 assert(value >= alpha);
685 // In case of failing high/low increase aspiration window and research,
686 // otherwise exit the fail high/low loop.
689 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
692 else if (value <= alpha)
694 AspirationFailLow = true;
695 StopOnPonderhit = false;
697 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
704 // Collect info about search result
705 bestMove = Rml[0].pv[0];
706 bestValues[iteration] = value;
707 bestMoveChanges[iteration] = Rml.bestMoveChanges;
709 // Drop the easy move if differs from the new best move
710 if (bestMove != easyMove)
711 easyMove = MOVE_NONE;
713 if (UseTimeManagement && !StopRequest)
716 bool noMoreTime = false;
718 // Stop search early when the last two iterations returned a mate score
720 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
721 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
724 // Stop search early if one move seems to be much better than the
725 // others or if there is only a single legal move. In this latter
726 // case we search up to Iteration 8 anyway to get a proper score.
728 && easyMove == bestMove
730 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
731 && current_search_time() > TimeMgr.available_time() / 16)
732 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
733 && current_search_time() > TimeMgr.available_time() / 32)))
736 // Add some extra time if the best move has changed during the last two iterations
737 if (iteration > 5 && iteration <= 50)
738 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
740 // Stop search if most of MaxSearchTime is consumed at the end of the
741 // iteration. We probably don't have enough time to search the first
742 // move at the next iteration anyway.
743 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
749 StopOnPonderhit = true;
756 *ponderMove = Rml[0].pv[1];
761 // search<>() is the main search function for both PV and non-PV nodes and for
762 // normal and SplitPoint nodes. When called just after a split point the search
763 // is simpler because we have already probed the hash table, done a null move
764 // search, and searched the first move before splitting, we don't have to repeat
765 // all this work again. We also don't need to store anything to the hash table
766 // here: This is taken care of after we return from the split point.
768 template <NodeType PvNode, bool SpNode, bool Root>
769 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
771 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
772 assert(beta > alpha && beta <= VALUE_INFINITE);
773 assert(PvNode || alpha == beta - 1);
774 assert((Root || ply > 0) && ply < PLY_MAX);
775 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
777 Move movesSearched[MOVES_MAX];
782 Move ttMove, move, excludedMove, threatMove;
785 Value bestValue, value, oldAlpha;
786 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
787 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
788 bool mateThreat = false;
789 int moveCount = 0, playedMoveCount = 0;
790 int threadID = pos.thread();
791 SplitPoint* sp = NULL;
793 refinedValue = bestValue = value = -VALUE_INFINITE;
795 isCheck = pos.is_check();
801 ttMove = excludedMove = MOVE_NONE;
802 threatMove = sp->threatMove;
803 mateThreat = sp->mateThreat;
804 goto split_point_start;
809 // Step 1. Initialize node and poll. Polling can abort search
810 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
811 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
813 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
819 // Step 2. Check for aborted search and immediate draw
821 || ThreadsMgr.cutoff_at_splitpoint(threadID)
823 || ply >= PLY_MAX - 1) && !Root)
826 // Step 3. Mate distance pruning
827 alpha = Max(value_mated_in(ply), alpha);
828 beta = Min(value_mate_in(ply+1), beta);
832 // Step 4. Transposition table lookup
833 // We don't want the score of a partial search to overwrite a previous full search
834 // TT value, so we use a different position key in case of an excluded move exists.
835 excludedMove = ss->excludedMove;
836 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
838 tte = TT.retrieve(posKey);
839 ttMove = tte ? tte->move() : MOVE_NONE;
841 // At PV nodes we check for exact scores, while at non-PV nodes we check for
842 // and return a fail high/low. Biggest advantage at probing at PV nodes is
843 // to have a smooth experience in analysis mode.
846 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
847 : ok_to_use_TT(tte, depth, beta, ply)))
850 ss->bestMove = ttMove; // Can be MOVE_NONE
851 return value_from_tt(tte->value(), ply);
854 // Step 5. Evaluate the position statically and
855 // update gain statistics of parent move.
857 ss->eval = ss->evalMargin = VALUE_NONE;
860 assert(tte->static_value() != VALUE_NONE);
862 ss->eval = tte->static_value();
863 ss->evalMargin = tte->static_value_margin();
864 refinedValue = refine_eval(tte, ss->eval, ply);
868 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
869 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
872 // Save gain for the parent non-capture move
873 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
875 // Step 6. Razoring (is omitted in PV nodes)
877 && depth < RazorDepth
879 && refinedValue < beta - razor_margin(depth)
880 && ttMove == MOVE_NONE
881 && !value_is_mate(beta)
882 && !pos.has_pawn_on_7th(pos.side_to_move()))
884 Value rbeta = beta - razor_margin(depth);
885 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
887 // Logically we should return (v + razor_margin(depth)), but
888 // surprisingly this did slightly weaker in tests.
892 // Step 7. Static null move pruning (is omitted in PV nodes)
893 // We're betting that the opponent doesn't have a move that will reduce
894 // the score by more than futility_margin(depth) if we do a null move.
897 && depth < RazorDepth
899 && refinedValue >= beta + futility_margin(depth, 0)
900 && !value_is_mate(beta)
901 && pos.non_pawn_material(pos.side_to_move()))
902 return refinedValue - futility_margin(depth, 0);
904 // Step 8. Null move search with verification search (is omitted in PV nodes)
909 && refinedValue >= beta
910 && !value_is_mate(beta)
911 && pos.non_pawn_material(pos.side_to_move()))
913 ss->currentMove = MOVE_NULL;
915 // Null move dynamic reduction based on depth
916 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
918 // Null move dynamic reduction based on value
919 if (refinedValue - beta > PawnValueMidgame)
922 pos.do_null_move(st);
923 (ss+1)->skipNullMove = true;
924 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
925 (ss+1)->skipNullMove = false;
926 pos.undo_null_move();
928 if (nullValue >= beta)
930 // Do not return unproven mate scores
931 if (nullValue >= value_mate_in(PLY_MAX))
934 if (depth < 6 * ONE_PLY)
937 // Do verification search at high depths
938 ss->skipNullMove = true;
939 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
940 ss->skipNullMove = false;
947 // The null move failed low, which means that we may be faced with
948 // some kind of threat. If the previous move was reduced, check if
949 // the move that refuted the null move was somehow connected to the
950 // move which was reduced. If a connection is found, return a fail
951 // low score (which will cause the reduced move to fail high in the
952 // parent node, which will trigger a re-search with full depth).
953 if (nullValue == value_mated_in(ply + 2))
956 threatMove = (ss+1)->bestMove;
957 if ( depth < ThreatDepth
959 && threatMove != MOVE_NONE
960 && connected_moves(pos, (ss-1)->currentMove, threatMove))
965 // Step 9. Internal iterative deepening
966 if ( depth >= IIDDepth[PvNode]
967 && ttMove == MOVE_NONE
968 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
970 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
972 ss->skipNullMove = true;
973 search<PvNode>(pos, ss, alpha, beta, d, ply);
974 ss->skipNullMove = false;
976 ttMove = ss->bestMove;
977 tte = TT.retrieve(posKey);
980 // Expensive mate threat detection (only for PV nodes)
982 mateThreat = pos.has_mate_threat();
984 split_point_start: // At split points actual search starts from here
986 // Initialize a MovePicker object for the current position
987 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
989 ss->bestMove = MOVE_NONE;
990 futilityBase = ss->eval + ss->evalMargin;
991 singularExtensionNode = !Root
993 && depth >= SingularExtensionDepth[PvNode]
996 && !excludedMove // Do not allow recursive singular extension search
997 && (tte->type() & VALUE_TYPE_LOWER)
998 && tte->depth() >= depth - 3 * ONE_PLY;
1001 lock_grab(&(sp->lock));
1002 bestValue = sp->bestValue;
1005 // Step 10. Loop through moves
1006 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1007 while ( bestValue < beta
1008 && (move = mp.get_next_move()) != MOVE_NONE
1009 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1011 assert(move_is_ok(move));
1015 moveCount = ++sp->moveCount;
1016 lock_release(&(sp->lock));
1018 else if (move == excludedMove)
1025 // This is used by time management
1026 FirstRootMove = (moveCount == 1);
1028 // Save the current node count before the move is searched
1029 nodes = pos.nodes_searched();
1031 // If it's time to send nodes info, do it here where we have the
1032 // correct accumulated node counts searched by each thread.
1033 if (SendSearchedNodes)
1035 SendSearchedNodes = false;
1036 cout << "info nodes " << nodes
1037 << " nps " << nps(pos)
1038 << " time " << current_search_time() << endl;
1041 if (current_search_time() >= 1000)
1042 cout << "info currmove " << move
1043 << " currmovenumber " << moveCount << endl;
1046 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1047 moveIsCheck = pos.move_is_check(move, ci);
1048 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1050 // Step 11. Decide the new search depth
1051 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1053 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1054 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1055 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1056 // lower then ttValue minus a margin then we extend ttMove.
1057 if ( singularExtensionNode
1058 && move == tte->move()
1061 Value ttValue = value_from_tt(tte->value(), ply);
1063 if (abs(ttValue) < VALUE_KNOWN_WIN)
1065 Value b = ttValue - SingularExtensionMargin;
1066 ss->excludedMove = move;
1067 ss->skipNullMove = true;
1068 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1069 ss->skipNullMove = false;
1070 ss->excludedMove = MOVE_NONE;
1071 ss->bestMove = MOVE_NONE;
1077 // Update current move (this must be done after singular extension search)
1078 ss->currentMove = move;
1079 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1081 // Step 12. Futility pruning (is omitted in PV nodes)
1083 && !captureOrPromotion
1087 && !move_is_castle(move))
1089 // Move count based pruning
1090 if ( moveCount >= futility_move_count(depth)
1091 && !(threatMove && connected_threat(pos, move, threatMove))
1092 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1095 lock_grab(&(sp->lock));
1100 // Value based pruning
1101 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1102 // but fixing this made program slightly weaker.
1103 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1104 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1105 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1107 if (futilityValueScaled < beta)
1111 lock_grab(&(sp->lock));
1112 if (futilityValueScaled > sp->bestValue)
1113 sp->bestValue = bestValue = futilityValueScaled;
1115 else if (futilityValueScaled > bestValue)
1116 bestValue = futilityValueScaled;
1121 // Prune moves with negative SEE at low depths
1122 if ( predictedDepth < 2 * ONE_PLY
1123 && bestValue > value_mated_in(PLY_MAX)
1124 && pos.see_sign(move) < 0)
1127 lock_grab(&(sp->lock));
1133 // Step 13. Make the move
1134 pos.do_move(move, st, ci, moveIsCheck);
1136 if (!SpNode && !captureOrPromotion)
1137 movesSearched[playedMoveCount++] = move;
1139 // Step extra. pv search (only in PV nodes)
1140 // The first move in list is the expected PV
1143 // Aspiration window is disabled in multi-pv case
1144 if (Root && MultiPV > 1)
1145 alpha = -VALUE_INFINITE;
1147 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1151 // Step 14. Reduced depth search
1152 // If the move fails high will be re-searched at full depth.
1153 bool doFullDepthSearch = true;
1155 if ( depth >= 3 * ONE_PLY
1156 && !captureOrPromotion
1158 && !move_is_castle(move)
1159 && ss->killers[0] != move
1160 && ss->killers[1] != move)
1162 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1163 : reduction<PvNode>(depth, moveCount);
1166 alpha = SpNode ? sp->alpha : alpha;
1167 Depth d = newDepth - ss->reduction;
1168 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1170 doFullDepthSearch = (value > alpha);
1172 ss->reduction = DEPTH_ZERO; // Restore original reduction
1175 // Step 15. Full depth search
1176 if (doFullDepthSearch)
1178 alpha = SpNode ? sp->alpha : alpha;
1179 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1181 // Step extra. pv search (only in PV nodes)
1182 // Search only for possible new PV nodes, if instead value >= beta then
1183 // parent node fails low with value <= alpha and tries another move.
1184 if (PvNode && value > alpha && (Root || value < beta))
1185 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1189 // Step 16. Undo move
1190 pos.undo_move(move);
1192 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1194 // Step 17. Check for new best move
1197 lock_grab(&(sp->lock));
1198 bestValue = sp->bestValue;
1202 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1207 sp->bestValue = value;
1211 if (PvNode && value < beta) // We want always alpha < beta
1219 sp->betaCutoff = true;
1221 if (value == value_mate_in(ply + 1))
1222 ss->mateKiller = move;
1224 ss->bestMove = move;
1227 sp->parentSstack->bestMove = move;
1233 // To avoid to exit with bestValue == -VALUE_INFINITE
1234 if (value > bestValue)
1237 // Finished searching the move. If StopRequest is true, the search
1238 // was aborted because the user interrupted the search or because we
1239 // ran out of time. In this case, the return value of the search cannot
1240 // be trusted, and we break out of the loop without updating the best
1245 // Remember searched nodes counts for this move
1246 mp.rm->nodes += pos.nodes_searched() - nodes;
1248 // Step 17. Check for new best move
1249 if (!isPvMove && value <= alpha)
1250 mp.rm->pv_score = -VALUE_INFINITE;
1253 // PV move or new best move!
1256 ss->bestMove = move;
1257 mp.rm->pv_score = value;
1258 mp.rm->extract_pv_from_tt(pos);
1260 // We record how often the best move has been changed in each
1261 // iteration. This information is used for time managment: When
1262 // the best move changes frequently, we allocate some more time.
1263 if (!isPvMove && MultiPV == 1)
1264 Rml.bestMoveChanges++;
1266 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1267 // requires we send all the PV lines properly sorted.
1268 Rml.sort_multipv(moveCount);
1270 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1271 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1273 // Update alpha. In multi-pv we don't use aspiration window, so
1274 // set alpha equal to minimum score among the PV lines.
1276 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1277 else if (value > alpha)
1280 } // PV move or new best move
1283 // Step 18. Check for split
1286 && depth >= ThreadsMgr.min_split_depth()
1287 && ThreadsMgr.active_threads() > 1
1289 && ThreadsMgr.available_thread_exists(threadID)
1291 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1292 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1293 threatMove, mateThreat, moveCount, &mp, PvNode);
1296 // Step 19. Check for mate and stalemate
1297 // All legal moves have been searched and if there are
1298 // no legal moves, it must be mate or stalemate.
1299 // If one move was excluded return fail low score.
1300 if (!SpNode && !moveCount)
1301 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1303 // Step 20. Update tables
1304 // If the search is not aborted, update the transposition table,
1305 // history counters, and killer moves.
1306 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1308 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1309 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1310 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1312 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1314 // Update killers and history only for non capture moves that fails high
1315 if ( bestValue >= beta
1316 && !pos.move_is_capture_or_promotion(move))
1318 update_history(pos, move, depth, movesSearched, playedMoveCount);
1319 update_killers(move, ss->killers);
1325 // Here we have the lock still grabbed
1326 sp->slaves[threadID] = 0;
1327 sp->nodes += pos.nodes_searched();
1328 lock_release(&(sp->lock));
1331 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1336 // qsearch() is the quiescence search function, which is called by the main
1337 // search function when the remaining depth is zero (or, to be more precise,
1338 // less than ONE_PLY).
1340 template <NodeType PvNode>
1341 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1343 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1344 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1345 assert(PvNode || alpha == beta - 1);
1347 assert(ply > 0 && ply < PLY_MAX);
1348 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1352 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1353 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1356 Value oldAlpha = alpha;
1358 ss->bestMove = ss->currentMove = MOVE_NONE;
1360 // Check for an instant draw or maximum ply reached
1361 if (pos.is_draw() || ply >= PLY_MAX - 1)
1364 // Decide whether or not to include checks, this fixes also the type of
1365 // TT entry depth that we are going to use. Note that in qsearch we use
1366 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1367 isCheck = pos.is_check();
1368 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1370 // Transposition table lookup. At PV nodes, we don't use the TT for
1371 // pruning, but only for move ordering.
1372 tte = TT.retrieve(pos.get_key());
1373 ttMove = (tte ? tte->move() : MOVE_NONE);
1375 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1377 ss->bestMove = ttMove; // Can be MOVE_NONE
1378 return value_from_tt(tte->value(), ply);
1381 // Evaluate the position statically
1384 bestValue = futilityBase = -VALUE_INFINITE;
1385 ss->eval = evalMargin = VALUE_NONE;
1386 enoughMaterial = false;
1392 assert(tte->static_value() != VALUE_NONE);
1394 evalMargin = tte->static_value_margin();
1395 ss->eval = bestValue = tte->static_value();
1398 ss->eval = bestValue = evaluate(pos, evalMargin);
1400 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1402 // Stand pat. Return immediately if static value is at least beta
1403 if (bestValue >= beta)
1406 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1411 if (PvNode && bestValue > alpha)
1414 // Futility pruning parameters, not needed when in check
1415 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1416 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1419 // Initialize a MovePicker object for the current position, and prepare
1420 // to search the moves. Because the depth is <= 0 here, only captures,
1421 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1423 MovePicker mp(pos, ttMove, depth, H);
1426 // Loop through the moves until no moves remain or a beta cutoff occurs
1427 while ( alpha < beta
1428 && (move = mp.get_next_move()) != MOVE_NONE)
1430 assert(move_is_ok(move));
1432 moveIsCheck = pos.move_is_check(move, ci);
1440 && !move_is_promotion(move)
1441 && !pos.move_is_passed_pawn_push(move))
1443 futilityValue = futilityBase
1444 + pos.endgame_value_of_piece_on(move_to(move))
1445 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1447 if (futilityValue < alpha)
1449 if (futilityValue > bestValue)
1450 bestValue = futilityValue;
1455 // Detect non-capture evasions that are candidate to be pruned
1456 evasionPrunable = isCheck
1457 && bestValue > value_mated_in(PLY_MAX)
1458 && !pos.move_is_capture(move)
1459 && !pos.can_castle(pos.side_to_move());
1461 // Don't search moves with negative SEE values
1463 && (!isCheck || evasionPrunable)
1465 && !move_is_promotion(move)
1466 && pos.see_sign(move) < 0)
1469 // Don't search useless checks
1474 && !pos.move_is_capture_or_promotion(move)
1475 && ss->eval + PawnValueMidgame / 4 < beta
1476 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1478 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1479 bestValue = ss->eval + PawnValueMidgame / 4;
1484 // Update current move
1485 ss->currentMove = move;
1487 // Make and search the move
1488 pos.do_move(move, st, ci, moveIsCheck);
1489 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1490 pos.undo_move(move);
1492 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1495 if (value > bestValue)
1501 ss->bestMove = move;
1506 // All legal moves have been searched. A special case: If we're in check
1507 // and no legal moves were found, it is checkmate.
1508 if (isCheck && bestValue == -VALUE_INFINITE)
1509 return value_mated_in(ply);
1511 // Update transposition table
1512 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1513 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1515 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1521 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1522 // it is used in RootMoveList to get an initial scoring.
1523 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1525 SearchStack ss[PLY_MAX_PLUS_2];
1528 memset(ss, 0, 4 * sizeof(SearchStack));
1529 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1531 for (MoveStack* cur = mlist; cur != last; cur++)
1533 ss[0].currentMove = cur->move;
1534 pos.do_move(cur->move, st);
1535 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1536 pos.undo_move(cur->move);
1541 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1542 // bestValue is updated only when returning false because in that case move
1545 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1547 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1548 Square from, to, ksq, victimSq;
1551 Value futilityValue, bv = *bestValue;
1553 from = move_from(move);
1555 them = opposite_color(pos.side_to_move());
1556 ksq = pos.king_square(them);
1557 kingAtt = pos.attacks_from<KING>(ksq);
1558 pc = pos.piece_on(from);
1560 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1561 oldAtt = pos.attacks_from(pc, from, occ);
1562 newAtt = pos.attacks_from(pc, to, occ);
1564 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1565 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1567 if (!(b && (b & (b - 1))))
1570 // Rule 2. Queen contact check is very dangerous
1571 if ( type_of_piece(pc) == QUEEN
1572 && bit_is_set(kingAtt, to))
1575 // Rule 3. Creating new double threats with checks
1576 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1580 victimSq = pop_1st_bit(&b);
1581 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1583 // Note that here we generate illegal "double move"!
1584 if ( futilityValue >= beta
1585 && pos.see_sign(make_move(from, victimSq)) >= 0)
1588 if (futilityValue > bv)
1592 // Update bestValue only if check is not dangerous (because we will prune the move)
1598 // connected_moves() tests whether two moves are 'connected' in the sense
1599 // that the first move somehow made the second move possible (for instance
1600 // if the moving piece is the same in both moves). The first move is assumed
1601 // to be the move that was made to reach the current position, while the
1602 // second move is assumed to be a move from the current position.
1604 bool connected_moves(const Position& pos, Move m1, Move m2) {
1606 Square f1, t1, f2, t2;
1609 assert(m1 && move_is_ok(m1));
1610 assert(m2 && move_is_ok(m2));
1612 // Case 1: The moving piece is the same in both moves
1618 // Case 2: The destination square for m2 was vacated by m1
1624 // Case 3: Moving through the vacated square
1625 if ( piece_is_slider(pos.piece_on(f2))
1626 && bit_is_set(squares_between(f2, t2), f1))
1629 // Case 4: The destination square for m2 is defended by the moving piece in m1
1630 p = pos.piece_on(t1);
1631 if (bit_is_set(pos.attacks_from(p, t1), t2))
1634 // Case 5: Discovered check, checking piece is the piece moved in m1
1635 if ( piece_is_slider(p)
1636 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1637 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1639 // discovered_check_candidates() works also if the Position's side to
1640 // move is the opposite of the checking piece.
1641 Color them = opposite_color(pos.side_to_move());
1642 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1644 if (bit_is_set(dcCandidates, f2))
1651 // value_is_mate() checks if the given value is a mate one eventually
1652 // compensated for the ply.
1654 bool value_is_mate(Value value) {
1656 assert(abs(value) <= VALUE_INFINITE);
1658 return value <= value_mated_in(PLY_MAX)
1659 || value >= value_mate_in(PLY_MAX);
1663 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1664 // "plies to mate from the current ply". Non-mate scores are unchanged.
1665 // The function is called before storing a value to the transposition table.
1667 Value value_to_tt(Value v, int ply) {
1669 if (v >= value_mate_in(PLY_MAX))
1672 if (v <= value_mated_in(PLY_MAX))
1679 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1680 // the transposition table to a mate score corrected for the current ply.
1682 Value value_from_tt(Value v, int ply) {
1684 if (v >= value_mate_in(PLY_MAX))
1687 if (v <= value_mated_in(PLY_MAX))
1694 // extension() decides whether a move should be searched with normal depth,
1695 // or with extended depth. Certain classes of moves (checking moves, in
1696 // particular) are searched with bigger depth than ordinary moves and in
1697 // any case are marked as 'dangerous'. Note that also if a move is not
1698 // extended, as example because the corresponding UCI option is set to zero,
1699 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1700 template <NodeType PvNode>
1701 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1702 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1704 assert(m != MOVE_NONE);
1706 Depth result = DEPTH_ZERO;
1707 *dangerous = moveIsCheck | mateThreat;
1711 if (moveIsCheck && pos.see_sign(m) >= 0)
1712 result += CheckExtension[PvNode];
1715 result += MateThreatExtension[PvNode];
1718 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1720 Color c = pos.side_to_move();
1721 if (relative_rank(c, move_to(m)) == RANK_7)
1723 result += PawnPushTo7thExtension[PvNode];
1726 if (pos.pawn_is_passed(c, move_to(m)))
1728 result += PassedPawnExtension[PvNode];
1733 if ( captureOrPromotion
1734 && pos.type_of_piece_on(move_to(m)) != PAWN
1735 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1736 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1737 && !move_is_promotion(m)
1740 result += PawnEndgameExtension[PvNode];
1745 && captureOrPromotion
1746 && pos.type_of_piece_on(move_to(m)) != PAWN
1747 && pos.see_sign(m) >= 0)
1749 result += ONE_PLY / 2;
1753 return Min(result, ONE_PLY);
1757 // connected_threat() tests whether it is safe to forward prune a move or if
1758 // is somehow coonected to the threat move returned by null search.
1760 bool connected_threat(const Position& pos, Move m, Move threat) {
1762 assert(move_is_ok(m));
1763 assert(threat && move_is_ok(threat));
1764 assert(!pos.move_is_check(m));
1765 assert(!pos.move_is_capture_or_promotion(m));
1766 assert(!pos.move_is_passed_pawn_push(m));
1768 Square mfrom, mto, tfrom, tto;
1770 mfrom = move_from(m);
1772 tfrom = move_from(threat);
1773 tto = move_to(threat);
1775 // Case 1: Don't prune moves which move the threatened piece
1779 // Case 2: If the threatened piece has value less than or equal to the
1780 // value of the threatening piece, don't prune move which defend it.
1781 if ( pos.move_is_capture(threat)
1782 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1783 || pos.type_of_piece_on(tfrom) == KING)
1784 && pos.move_attacks_square(m, tto))
1787 // Case 3: If the moving piece in the threatened move is a slider, don't
1788 // prune safe moves which block its ray.
1789 if ( piece_is_slider(pos.piece_on(tfrom))
1790 && bit_is_set(squares_between(tfrom, tto), mto)
1791 && pos.see_sign(m) >= 0)
1798 // ok_to_use_TT() returns true if a transposition table score
1799 // can be used at a given point in search.
1801 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1803 Value v = value_from_tt(tte->value(), ply);
1805 return ( tte->depth() >= depth
1806 || v >= Max(value_mate_in(PLY_MAX), beta)
1807 || v < Min(value_mated_in(PLY_MAX), beta))
1809 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1810 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1814 // refine_eval() returns the transposition table score if
1815 // possible otherwise falls back on static position evaluation.
1817 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1821 Value v = value_from_tt(tte->value(), ply);
1823 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1824 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1831 // update_history() registers a good move that produced a beta-cutoff
1832 // in history and marks as failures all the other moves of that ply.
1834 void update_history(const Position& pos, Move move, Depth depth,
1835 Move movesSearched[], int moveCount) {
1837 Value bonus = Value(int(depth) * int(depth));
1839 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1841 for (int i = 0; i < moveCount - 1; i++)
1843 m = movesSearched[i];
1847 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1852 // update_killers() add a good move that produced a beta-cutoff
1853 // among the killer moves of that ply.
1855 void update_killers(Move m, Move killers[]) {
1857 if (m != killers[0])
1859 killers[1] = killers[0];
1865 // update_gains() updates the gains table of a non-capture move given
1866 // the static position evaluation before and after the move.
1868 void update_gains(const Position& pos, Move m, Value before, Value after) {
1871 && before != VALUE_NONE
1872 && after != VALUE_NONE
1873 && pos.captured_piece_type() == PIECE_TYPE_NONE
1874 && !move_is_special(m))
1875 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1879 // value_to_uci() converts a value to a string suitable for use with the UCI
1880 // protocol specifications:
1882 // cp <x> The score from the engine's point of view in centipawns.
1883 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1884 // use negative values for y.
1886 std::string value_to_uci(Value v) {
1888 std::stringstream s;
1890 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1891 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1893 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1899 // current_search_time() returns the number of milliseconds which have passed
1900 // since the beginning of the current search.
1902 int current_search_time() {
1904 return get_system_time() - SearchStartTime;
1908 // nps() computes the current nodes/second count
1910 int nps(const Position& pos) {
1912 int t = current_search_time();
1913 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1917 // poll() performs two different functions: It polls for user input, and it
1918 // looks at the time consumed so far and decides if it's time to abort the
1921 void poll(const Position& pos) {
1923 static int lastInfoTime;
1924 int t = current_search_time();
1927 if (input_available())
1929 // We are line oriented, don't read single chars
1930 std::string command;
1932 if (!std::getline(std::cin, command))
1935 if (command == "quit")
1937 // Quit the program as soon as possible
1939 QuitRequest = StopRequest = true;
1942 else if (command == "stop")
1944 // Stop calculating as soon as possible, but still send the "bestmove"
1945 // and possibly the "ponder" token when finishing the search.
1949 else if (command == "ponderhit")
1951 // The opponent has played the expected move. GUI sends "ponderhit" if
1952 // we were told to ponder on the same move the opponent has played. We
1953 // should continue searching but switching from pondering to normal search.
1956 if (StopOnPonderhit)
1961 // Print search information
1965 else if (lastInfoTime > t)
1966 // HACK: Must be a new search where we searched less than
1967 // NodesBetweenPolls nodes during the first second of search.
1970 else if (t - lastInfoTime >= 1000)
1977 if (dbg_show_hit_rate)
1978 dbg_print_hit_rate();
1980 // Send info on searched nodes as soon as we return to root
1981 SendSearchedNodes = true;
1984 // Should we stop the search?
1988 bool stillAtFirstMove = FirstRootMove
1989 && !AspirationFailLow
1990 && t > TimeMgr.available_time();
1992 bool noMoreTime = t > TimeMgr.maximum_time()
1993 || stillAtFirstMove;
1995 if ( (UseTimeManagement && noMoreTime)
1996 || (ExactMaxTime && t >= ExactMaxTime)
1997 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2002 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2003 // while the program is pondering. The point is to work around a wrinkle in
2004 // the UCI protocol: When pondering, the engine is not allowed to give a
2005 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2006 // We simply wait here until one of these commands is sent, and return,
2007 // after which the bestmove and pondermove will be printed.
2009 void wait_for_stop_or_ponderhit() {
2011 std::string command;
2015 // Wait for a command from stdin
2016 if (!std::getline(std::cin, command))
2019 if (command == "quit")
2024 else if (command == "ponderhit" || command == "stop")
2030 // init_thread() is the function which is called when a new thread is
2031 // launched. It simply calls the idle_loop() function with the supplied
2032 // threadID. There are two versions of this function; one for POSIX
2033 // threads and one for Windows threads.
2035 #if !defined(_MSC_VER)
2037 void* init_thread(void* threadID) {
2039 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2045 DWORD WINAPI init_thread(LPVOID threadID) {
2047 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2054 /// The ThreadsManager class
2057 // read_uci_options() updates number of active threads and other internal
2058 // parameters according to the UCI options values. It is called before
2059 // to start a new search.
2061 void ThreadsManager::read_uci_options() {
2063 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2064 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2065 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2066 activeThreads = Options["Threads"].value<int>();
2070 // idle_loop() is where the threads are parked when they have no work to do.
2071 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2072 // object for which the current thread is the master.
2074 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2076 assert(threadID >= 0 && threadID < MAX_THREADS);
2079 bool allFinished = false;
2083 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2084 // master should exit as last one.
2085 if (allThreadsShouldExit)
2088 threads[threadID].state = THREAD_TERMINATED;
2092 // If we are not thinking, wait for a condition to be signaled
2093 // instead of wasting CPU time polling for work.
2094 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2095 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2097 assert(!sp || useSleepingThreads);
2098 assert(threadID != 0 || useSleepingThreads);
2100 if (threads[threadID].state == THREAD_INITIALIZING)
2101 threads[threadID].state = THREAD_AVAILABLE;
2103 // Grab the lock to avoid races with wake_sleeping_thread()
2104 lock_grab(&sleepLock[threadID]);
2106 // If we are master and all slaves have finished do not go to sleep
2107 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2108 allFinished = (i == activeThreads);
2110 if (allFinished || allThreadsShouldExit)
2112 lock_release(&sleepLock[threadID]);
2116 // Do sleep here after retesting sleep conditions
2117 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2118 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2120 lock_release(&sleepLock[threadID]);
2123 // If this thread has been assigned work, launch a search
2124 if (threads[threadID].state == THREAD_WORKISWAITING)
2126 assert(!allThreadsShouldExit);
2128 threads[threadID].state = THREAD_SEARCHING;
2130 // Here we call search() with SplitPoint template parameter set to true
2131 SplitPoint* tsp = threads[threadID].splitPoint;
2132 Position pos(*tsp->pos, threadID);
2133 SearchStack* ss = tsp->sstack[threadID] + 1;
2137 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2139 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2141 assert(threads[threadID].state == THREAD_SEARCHING);
2143 threads[threadID].state = THREAD_AVAILABLE;
2145 // Wake up master thread so to allow it to return from the idle loop in
2146 // case we are the last slave of the split point.
2147 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2148 wake_sleeping_thread(tsp->master);
2151 // If this thread is the master of a split point and all slaves have
2152 // finished their work at this split point, return from the idle loop.
2153 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2154 allFinished = (i == activeThreads);
2158 // Because sp->slaves[] is reset under lock protection,
2159 // be sure sp->lock has been released before to return.
2160 lock_grab(&(sp->lock));
2161 lock_release(&(sp->lock));
2163 // In helpful master concept a master can help only a sub-tree, and
2164 // because here is all finished is not possible master is booked.
2165 assert(threads[threadID].state == THREAD_AVAILABLE);
2167 threads[threadID].state = THREAD_SEARCHING;
2174 // init_threads() is called during startup. It launches all helper threads,
2175 // and initializes the split point stack and the global locks and condition
2178 void ThreadsManager::init_threads() {
2180 int i, arg[MAX_THREADS];
2183 // Initialize global locks
2186 for (i = 0; i < MAX_THREADS; i++)
2188 lock_init(&sleepLock[i]);
2189 cond_init(&sleepCond[i]);
2192 // Initialize splitPoints[] locks
2193 for (i = 0; i < MAX_THREADS; i++)
2194 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2195 lock_init(&(threads[i].splitPoints[j].lock));
2197 // Will be set just before program exits to properly end the threads
2198 allThreadsShouldExit = false;
2200 // Threads will be put all threads to sleep as soon as created
2203 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2204 threads[0].state = THREAD_SEARCHING;
2205 for (i = 1; i < MAX_THREADS; i++)
2206 threads[i].state = THREAD_INITIALIZING;
2208 // Launch the helper threads
2209 for (i = 1; i < MAX_THREADS; i++)
2213 #if !defined(_MSC_VER)
2214 pthread_t pthread[1];
2215 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2216 pthread_detach(pthread[0]);
2218 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2222 cout << "Failed to create thread number " << i << endl;
2226 // Wait until the thread has finished launching and is gone to sleep
2227 while (threads[i].state == THREAD_INITIALIZING) {}
2232 // exit_threads() is called when the program exits. It makes all the
2233 // helper threads exit cleanly.
2235 void ThreadsManager::exit_threads() {
2237 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2239 // Wake up all the threads and waits for termination
2240 for (int i = 1; i < MAX_THREADS; i++)
2242 wake_sleeping_thread(i);
2243 while (threads[i].state != THREAD_TERMINATED) {}
2246 // Now we can safely destroy the locks
2247 for (int i = 0; i < MAX_THREADS; i++)
2248 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2249 lock_destroy(&(threads[i].splitPoints[j].lock));
2251 lock_destroy(&mpLock);
2253 // Now we can safely destroy the wait conditions
2254 for (int i = 0; i < MAX_THREADS; i++)
2256 lock_destroy(&sleepLock[i]);
2257 cond_destroy(&sleepCond[i]);
2262 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2263 // the thread's currently active split point, or in some ancestor of
2264 // the current split point.
2266 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2268 assert(threadID >= 0 && threadID < activeThreads);
2270 SplitPoint* sp = threads[threadID].splitPoint;
2272 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2277 // thread_is_available() checks whether the thread with threadID "slave" is
2278 // available to help the thread with threadID "master" at a split point. An
2279 // obvious requirement is that "slave" must be idle. With more than two
2280 // threads, this is not by itself sufficient: If "slave" is the master of
2281 // some active split point, it is only available as a slave to the other
2282 // threads which are busy searching the split point at the top of "slave"'s
2283 // split point stack (the "helpful master concept" in YBWC terminology).
2285 bool ThreadsManager::thread_is_available(int slave, int master) const {
2287 assert(slave >= 0 && slave < activeThreads);
2288 assert(master >= 0 && master < activeThreads);
2289 assert(activeThreads > 1);
2291 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2294 // Make a local copy to be sure doesn't change under our feet
2295 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2297 // No active split points means that the thread is available as
2298 // a slave for any other thread.
2299 if (localActiveSplitPoints == 0 || activeThreads == 2)
2302 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2303 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2304 // could have been set to 0 by another thread leading to an out of bound access.
2305 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2312 // available_thread_exists() tries to find an idle thread which is available as
2313 // a slave for the thread with threadID "master".
2315 bool ThreadsManager::available_thread_exists(int master) const {
2317 assert(master >= 0 && master < activeThreads);
2318 assert(activeThreads > 1);
2320 for (int i = 0; i < activeThreads; i++)
2321 if (thread_is_available(i, master))
2328 // split() does the actual work of distributing the work at a node between
2329 // several available threads. If it does not succeed in splitting the
2330 // node (because no idle threads are available, or because we have no unused
2331 // split point objects), the function immediately returns. If splitting is
2332 // possible, a SplitPoint object is initialized with all the data that must be
2333 // copied to the helper threads and we tell our helper threads that they have
2334 // been assigned work. This will cause them to instantly leave their idle loops and
2335 // call search().When all threads have returned from search() then split() returns.
2337 template <bool Fake>
2338 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2339 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2340 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2341 assert(pos.is_ok());
2342 assert(ply > 0 && ply < PLY_MAX);
2343 assert(*bestValue >= -VALUE_INFINITE);
2344 assert(*bestValue <= *alpha);
2345 assert(*alpha < beta);
2346 assert(beta <= VALUE_INFINITE);
2347 assert(depth > DEPTH_ZERO);
2348 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2349 assert(activeThreads > 1);
2351 int i, master = pos.thread();
2352 Thread& masterThread = threads[master];
2356 // If no other thread is available to help us, or if we have too many
2357 // active split points, don't split.
2358 if ( !available_thread_exists(master)
2359 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2361 lock_release(&mpLock);
2365 // Pick the next available split point object from the split point stack
2366 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2368 // Initialize the split point object
2369 splitPoint.parent = masterThread.splitPoint;
2370 splitPoint.master = master;
2371 splitPoint.betaCutoff = false;
2372 splitPoint.ply = ply;
2373 splitPoint.depth = depth;
2374 splitPoint.threatMove = threatMove;
2375 splitPoint.mateThreat = mateThreat;
2376 splitPoint.alpha = *alpha;
2377 splitPoint.beta = beta;
2378 splitPoint.pvNode = pvNode;
2379 splitPoint.bestValue = *bestValue;
2381 splitPoint.moveCount = moveCount;
2382 splitPoint.pos = &pos;
2383 splitPoint.nodes = 0;
2384 splitPoint.parentSstack = ss;
2385 for (i = 0; i < activeThreads; i++)
2386 splitPoint.slaves[i] = 0;
2388 masterThread.splitPoint = &splitPoint;
2390 // If we are here it means we are not available
2391 assert(masterThread.state != THREAD_AVAILABLE);
2393 int workersCnt = 1; // At least the master is included
2395 // Allocate available threads setting state to THREAD_BOOKED
2396 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2397 if (thread_is_available(i, master))
2399 threads[i].state = THREAD_BOOKED;
2400 threads[i].splitPoint = &splitPoint;
2401 splitPoint.slaves[i] = 1;
2405 assert(Fake || workersCnt > 1);
2407 // We can release the lock because slave threads are already booked and master is not available
2408 lock_release(&mpLock);
2410 // Tell the threads that they have work to do. This will make them leave
2411 // their idle loop. But before copy search stack tail for each thread.
2412 for (i = 0; i < activeThreads; i++)
2413 if (i == master || splitPoint.slaves[i])
2415 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2417 assert(i == master || threads[i].state == THREAD_BOOKED);
2419 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2421 if (useSleepingThreads && i != master)
2422 wake_sleeping_thread(i);
2425 // Everything is set up. The master thread enters the idle loop, from
2426 // which it will instantly launch a search, because its state is
2427 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2428 // idle loop, which means that the main thread will return from the idle
2429 // loop when all threads have finished their work at this split point.
2430 idle_loop(master, &splitPoint);
2432 // We have returned from the idle loop, which means that all threads are
2433 // finished. Update alpha and bestValue, and return.
2436 *alpha = splitPoint.alpha;
2437 *bestValue = splitPoint.bestValue;
2438 masterThread.activeSplitPoints--;
2439 masterThread.splitPoint = splitPoint.parent;
2440 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2442 lock_release(&mpLock);
2446 // wake_sleeping_thread() wakes up the thread with the given threadID
2447 // when it is time to start a new search.
2449 void ThreadsManager::wake_sleeping_thread(int threadID) {
2451 lock_grab(&sleepLock[threadID]);
2452 cond_signal(&sleepCond[threadID]);
2453 lock_release(&sleepLock[threadID]);
2457 /// RootMove and RootMoveList method's definitions
2459 RootMove::RootMove() {
2462 pv_score = non_pv_score = -VALUE_INFINITE;
2466 RootMove& RootMove::operator=(const RootMove& rm) {
2468 const Move* src = rm.pv;
2471 // Avoid a costly full rm.pv[] copy
2472 do *dst++ = *src; while (*src++ != MOVE_NONE);
2475 pv_score = rm.pv_score;
2476 non_pv_score = rm.non_pv_score;
2480 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2481 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2482 // allow to always have a ponder move even when we fail high at root and also a
2483 // long PV to print that is important for position analysis.
2485 void RootMove::extract_pv_from_tt(Position& pos) {
2487 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2491 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2493 pos.do_move(pv[0], *st++);
2495 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2496 && tte->move() != MOVE_NONE
2497 && move_is_legal(pos, tte->move())
2499 && (!pos.is_draw() || ply < 2))
2501 pv[ply] = tte->move();
2502 pos.do_move(pv[ply++], *st++);
2504 pv[ply] = MOVE_NONE;
2506 do pos.undo_move(pv[--ply]); while (ply);
2509 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2510 // the PV back into the TT. This makes sure the old PV moves are searched
2511 // first, even if the old TT entries have been overwritten.
2513 void RootMove::insert_pv_in_tt(Position& pos) {
2515 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2518 Value v, m = VALUE_NONE;
2521 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2525 tte = TT.retrieve(k);
2527 // Don't overwrite exsisting correct entries
2528 if (!tte || tte->move() != pv[ply])
2530 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2531 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2533 pos.do_move(pv[ply], *st++);
2535 } while (pv[++ply] != MOVE_NONE);
2537 do pos.undo_move(pv[--ply]); while (ply);
2540 // pv_info_to_uci() returns a string with information on the current PV line
2541 // formatted according to UCI specification and eventually writes the info
2542 // to a log file. It is called at each iteration or after a new pv is found.
2544 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2546 std::stringstream s, l;
2549 while (*m != MOVE_NONE)
2552 s << "info depth " << depth / ONE_PLY
2553 << " seldepth " << int(m - pv)
2554 << " multipv " << pvLine + 1
2555 << " score " << value_to_uci(pv_score)
2556 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2557 << " time " << current_search_time()
2558 << " nodes " << pos.nodes_searched()
2559 << " nps " << nps(pos)
2560 << " pv " << l.str();
2562 if (UseLogFile && pvLine == 0)
2564 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2565 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2567 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2573 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2575 MoveStack mlist[MOVES_MAX];
2579 bestMoveChanges = 0;
2581 // Generate all legal moves and score them
2582 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2583 qsearch_scoring(pos, mlist, last);
2585 // Add each move to the RootMoveList's vector
2586 for (MoveStack* cur = mlist; cur != last; cur++)
2588 // If we have a searchMoves[] list then verify cur->move
2589 // is in the list before to add it.
2590 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2592 if (searchMoves[0] && *sm != cur->move)
2596 rm.pv[0] = cur->move;
2597 rm.pv[1] = MOVE_NONE;
2598 rm.pv_score = Value(cur->score);