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 = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
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 don't use the TT for pruning, but only for move ordering.
842 // This is to avoid problems in the following areas:
844 // * Repetition draw detection
845 // * Fifty move rule detection
846 // * Searching for a mate
847 // * Printing of full PV line
848 if (!PvNode && tte && 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 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1268 // requires we send all the PV lines properly sorted.
1269 Rml.sort_multipv(moveCount);
1271 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1272 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1274 // Update alpha. In multi-pv we don't use aspiration window, so
1275 // set alpha equal to minimum score among the PV lines.
1277 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1278 else if (value > alpha)
1281 } // PV move or new best move
1284 // Step 18. Check for split
1287 && depth >= ThreadsMgr.min_split_depth()
1288 && ThreadsMgr.active_threads() > 1
1290 && ThreadsMgr.available_thread_exists(threadID)
1292 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1293 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1294 threatMove, mateThreat, moveCount, &mp, PvNode);
1297 // Step 19. Check for mate and stalemate
1298 // All legal moves have been searched and if there are
1299 // no legal moves, it must be mate or stalemate.
1300 // If one move was excluded return fail low score.
1301 if (!SpNode && !moveCount)
1302 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1304 // Step 20. Update tables
1305 // If the search is not aborted, update the transposition table,
1306 // history counters, and killer moves.
1307 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1309 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1310 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1311 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1313 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1315 // Update killers and history only for non capture moves that fails high
1316 if ( bestValue >= beta
1317 && !pos.move_is_capture_or_promotion(move))
1319 update_history(pos, move, depth, movesSearched, playedMoveCount);
1320 update_killers(move, ss->killers);
1326 // Here we have the lock still grabbed
1327 sp->slaves[threadID] = 0;
1328 sp->nodes += pos.nodes_searched();
1329 lock_release(&(sp->lock));
1332 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1337 // qsearch() is the quiescence search function, which is called by the main
1338 // search function when the remaining depth is zero (or, to be more precise,
1339 // less than ONE_PLY).
1341 template <NodeType PvNode>
1342 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1344 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1345 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1346 assert(PvNode || alpha == beta - 1);
1348 assert(ply > 0 && ply < PLY_MAX);
1349 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1353 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1354 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1357 Value oldAlpha = alpha;
1359 ss->bestMove = ss->currentMove = MOVE_NONE;
1361 // Check for an instant draw or maximum ply reached
1362 if (pos.is_draw() || ply >= PLY_MAX - 1)
1365 // Decide whether or not to include checks, this fixes also the type of
1366 // TT entry depth that we are going to use. Note that in qsearch we use
1367 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1368 isCheck = pos.is_check();
1369 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1371 // Transposition table lookup. At PV nodes, we don't use the TT for
1372 // pruning, but only for move ordering.
1373 tte = TT.retrieve(pos.get_key());
1374 ttMove = (tte ? tte->move() : MOVE_NONE);
1376 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1378 ss->bestMove = ttMove; // Can be MOVE_NONE
1379 return value_from_tt(tte->value(), ply);
1382 // Evaluate the position statically
1385 bestValue = futilityBase = -VALUE_INFINITE;
1386 ss->eval = evalMargin = VALUE_NONE;
1387 enoughMaterial = false;
1393 assert(tte->static_value() != VALUE_NONE);
1395 evalMargin = tte->static_value_margin();
1396 ss->eval = bestValue = tte->static_value();
1399 ss->eval = bestValue = evaluate(pos, evalMargin);
1401 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1403 // Stand pat. Return immediately if static value is at least beta
1404 if (bestValue >= beta)
1407 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1412 if (PvNode && bestValue > alpha)
1415 // Futility pruning parameters, not needed when in check
1416 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1417 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1420 // Initialize a MovePicker object for the current position, and prepare
1421 // to search the moves. Because the depth is <= 0 here, only captures,
1422 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1424 MovePicker mp(pos, ttMove, depth, H);
1427 // Loop through the moves until no moves remain or a beta cutoff occurs
1428 while ( alpha < beta
1429 && (move = mp.get_next_move()) != MOVE_NONE)
1431 assert(move_is_ok(move));
1433 moveIsCheck = pos.move_is_check(move, ci);
1441 && !move_is_promotion(move)
1442 && !pos.move_is_passed_pawn_push(move))
1444 futilityValue = futilityBase
1445 + pos.endgame_value_of_piece_on(move_to(move))
1446 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1448 if (futilityValue < alpha)
1450 if (futilityValue > bestValue)
1451 bestValue = futilityValue;
1456 // Detect non-capture evasions that are candidate to be pruned
1457 evasionPrunable = isCheck
1458 && bestValue > value_mated_in(PLY_MAX)
1459 && !pos.move_is_capture(move)
1460 && !pos.can_castle(pos.side_to_move());
1462 // Don't search moves with negative SEE values
1464 && (!isCheck || evasionPrunable)
1466 && !move_is_promotion(move)
1467 && pos.see_sign(move) < 0)
1470 // Don't search useless checks
1475 && !pos.move_is_capture_or_promotion(move)
1476 && ss->eval + PawnValueMidgame / 4 < beta
1477 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1479 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1480 bestValue = ss->eval + PawnValueMidgame / 4;
1485 // Update current move
1486 ss->currentMove = move;
1488 // Make and search the move
1489 pos.do_move(move, st, ci, moveIsCheck);
1490 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1491 pos.undo_move(move);
1493 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1496 if (value > bestValue)
1502 ss->bestMove = move;
1507 // All legal moves have been searched. A special case: If we're in check
1508 // and no legal moves were found, it is checkmate.
1509 if (isCheck && bestValue == -VALUE_INFINITE)
1510 return value_mated_in(ply);
1512 // Update transposition table
1513 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1514 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1516 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1522 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1523 // it is used in RootMoveList to get an initial scoring.
1524 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1526 SearchStack ss[PLY_MAX_PLUS_2];
1529 memset(ss, 0, 4 * sizeof(SearchStack));
1530 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1532 for (MoveStack* cur = mlist; cur != last; cur++)
1534 ss[0].currentMove = cur->move;
1535 pos.do_move(cur->move, st);
1536 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1537 pos.undo_move(cur->move);
1542 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1543 // bestValue is updated only when returning false because in that case move
1546 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1548 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1549 Square from, to, ksq, victimSq;
1552 Value futilityValue, bv = *bestValue;
1554 from = move_from(move);
1556 them = opposite_color(pos.side_to_move());
1557 ksq = pos.king_square(them);
1558 kingAtt = pos.attacks_from<KING>(ksq);
1559 pc = pos.piece_on(from);
1561 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1562 oldAtt = pos.attacks_from(pc, from, occ);
1563 newAtt = pos.attacks_from(pc, to, occ);
1565 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1566 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1568 if (!(b && (b & (b - 1))))
1571 // Rule 2. Queen contact check is very dangerous
1572 if ( type_of_piece(pc) == QUEEN
1573 && bit_is_set(kingAtt, to))
1576 // Rule 3. Creating new double threats with checks
1577 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1581 victimSq = pop_1st_bit(&b);
1582 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1584 // Note that here we generate illegal "double move"!
1585 if ( futilityValue >= beta
1586 && pos.see_sign(make_move(from, victimSq)) >= 0)
1589 if (futilityValue > bv)
1593 // Update bestValue only if check is not dangerous (because we will prune the move)
1599 // connected_moves() tests whether two moves are 'connected' in the sense
1600 // that the first move somehow made the second move possible (for instance
1601 // if the moving piece is the same in both moves). The first move is assumed
1602 // to be the move that was made to reach the current position, while the
1603 // second move is assumed to be a move from the current position.
1605 bool connected_moves(const Position& pos, Move m1, Move m2) {
1607 Square f1, t1, f2, t2;
1610 assert(m1 && move_is_ok(m1));
1611 assert(m2 && move_is_ok(m2));
1613 // Case 1: The moving piece is the same in both moves
1619 // Case 2: The destination square for m2 was vacated by m1
1625 // Case 3: Moving through the vacated square
1626 if ( piece_is_slider(pos.piece_on(f2))
1627 && bit_is_set(squares_between(f2, t2), f1))
1630 // Case 4: The destination square for m2 is defended by the moving piece in m1
1631 p = pos.piece_on(t1);
1632 if (bit_is_set(pos.attacks_from(p, t1), t2))
1635 // Case 5: Discovered check, checking piece is the piece moved in m1
1636 if ( piece_is_slider(p)
1637 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1638 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1640 // discovered_check_candidates() works also if the Position's side to
1641 // move is the opposite of the checking piece.
1642 Color them = opposite_color(pos.side_to_move());
1643 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1645 if (bit_is_set(dcCandidates, f2))
1652 // value_is_mate() checks if the given value is a mate one eventually
1653 // compensated for the ply.
1655 bool value_is_mate(Value value) {
1657 assert(abs(value) <= VALUE_INFINITE);
1659 return value <= value_mated_in(PLY_MAX)
1660 || value >= value_mate_in(PLY_MAX);
1664 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1665 // "plies to mate from the current ply". Non-mate scores are unchanged.
1666 // The function is called before storing a value to the transposition table.
1668 Value value_to_tt(Value v, int ply) {
1670 if (v >= value_mate_in(PLY_MAX))
1673 if (v <= value_mated_in(PLY_MAX))
1680 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1681 // the transposition table to a mate score corrected for the current ply.
1683 Value value_from_tt(Value v, int ply) {
1685 if (v >= value_mate_in(PLY_MAX))
1688 if (v <= value_mated_in(PLY_MAX))
1695 // extension() decides whether a move should be searched with normal depth,
1696 // or with extended depth. Certain classes of moves (checking moves, in
1697 // particular) are searched with bigger depth than ordinary moves and in
1698 // any case are marked as 'dangerous'. Note that also if a move is not
1699 // extended, as example because the corresponding UCI option is set to zero,
1700 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1701 template <NodeType PvNode>
1702 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1703 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1705 assert(m != MOVE_NONE);
1707 Depth result = DEPTH_ZERO;
1708 *dangerous = moveIsCheck | mateThreat;
1712 if (moveIsCheck && pos.see_sign(m) >= 0)
1713 result += CheckExtension[PvNode];
1716 result += MateThreatExtension[PvNode];
1719 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1721 Color c = pos.side_to_move();
1722 if (relative_rank(c, move_to(m)) == RANK_7)
1724 result += PawnPushTo7thExtension[PvNode];
1727 if (pos.pawn_is_passed(c, move_to(m)))
1729 result += PassedPawnExtension[PvNode];
1734 if ( captureOrPromotion
1735 && pos.type_of_piece_on(move_to(m)) != PAWN
1736 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1737 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1738 && !move_is_promotion(m)
1741 result += PawnEndgameExtension[PvNode];
1746 && captureOrPromotion
1747 && pos.type_of_piece_on(move_to(m)) != PAWN
1748 && pos.see_sign(m) >= 0)
1750 result += ONE_PLY / 2;
1754 return Min(result, ONE_PLY);
1758 // connected_threat() tests whether it is safe to forward prune a move or if
1759 // is somehow coonected to the threat move returned by null search.
1761 bool connected_threat(const Position& pos, Move m, Move threat) {
1763 assert(move_is_ok(m));
1764 assert(threat && move_is_ok(threat));
1765 assert(!pos.move_is_check(m));
1766 assert(!pos.move_is_capture_or_promotion(m));
1767 assert(!pos.move_is_passed_pawn_push(m));
1769 Square mfrom, mto, tfrom, tto;
1771 mfrom = move_from(m);
1773 tfrom = move_from(threat);
1774 tto = move_to(threat);
1776 // Case 1: Don't prune moves which move the threatened piece
1780 // Case 2: If the threatened piece has value less than or equal to the
1781 // value of the threatening piece, don't prune move which defend it.
1782 if ( pos.move_is_capture(threat)
1783 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1784 || pos.type_of_piece_on(tfrom) == KING)
1785 && pos.move_attacks_square(m, tto))
1788 // Case 3: If the moving piece in the threatened move is a slider, don't
1789 // prune safe moves which block its ray.
1790 if ( piece_is_slider(pos.piece_on(tfrom))
1791 && bit_is_set(squares_between(tfrom, tto), mto)
1792 && pos.see_sign(m) >= 0)
1799 // ok_to_use_TT() returns true if a transposition table score
1800 // can be used at a given point in search.
1802 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1804 Value v = value_from_tt(tte->value(), ply);
1806 return ( tte->depth() >= depth
1807 || v >= Max(value_mate_in(PLY_MAX), beta)
1808 || v < Min(value_mated_in(PLY_MAX), beta))
1810 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1811 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1815 // refine_eval() returns the transposition table score if
1816 // possible otherwise falls back on static position evaluation.
1818 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1822 Value v = value_from_tt(tte->value(), ply);
1824 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1825 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1832 // update_history() registers a good move that produced a beta-cutoff
1833 // in history and marks as failures all the other moves of that ply.
1835 void update_history(const Position& pos, Move move, Depth depth,
1836 Move movesSearched[], int moveCount) {
1838 Value bonus = Value(int(depth) * int(depth));
1840 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1842 for (int i = 0; i < moveCount - 1; i++)
1844 m = movesSearched[i];
1848 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1853 // update_killers() add a good move that produced a beta-cutoff
1854 // among the killer moves of that ply.
1856 void update_killers(Move m, Move killers[]) {
1858 if (m != killers[0])
1860 killers[1] = killers[0];
1866 // update_gains() updates the gains table of a non-capture move given
1867 // the static position evaluation before and after the move.
1869 void update_gains(const Position& pos, Move m, Value before, Value after) {
1872 && before != VALUE_NONE
1873 && after != VALUE_NONE
1874 && pos.captured_piece_type() == PIECE_TYPE_NONE
1875 && !move_is_special(m))
1876 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1880 // value_to_uci() converts a value to a string suitable for use with the UCI
1881 // protocol specifications:
1883 // cp <x> The score from the engine's point of view in centipawns.
1884 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1885 // use negative values for y.
1887 std::string value_to_uci(Value v) {
1889 std::stringstream s;
1891 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1892 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1894 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1900 // current_search_time() returns the number of milliseconds which have passed
1901 // since the beginning of the current search.
1903 int current_search_time() {
1905 return get_system_time() - SearchStartTime;
1909 // nps() computes the current nodes/second count
1911 int nps(const Position& pos) {
1913 int t = current_search_time();
1914 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1918 // poll() performs two different functions: It polls for user input, and it
1919 // looks at the time consumed so far and decides if it's time to abort the
1922 void poll(const Position& pos) {
1924 static int lastInfoTime;
1925 int t = current_search_time();
1928 if (input_available())
1930 // We are line oriented, don't read single chars
1931 std::string command;
1933 if (!std::getline(std::cin, command))
1936 if (command == "quit")
1938 // Quit the program as soon as possible
1940 QuitRequest = StopRequest = true;
1943 else if (command == "stop")
1945 // Stop calculating as soon as possible, but still send the "bestmove"
1946 // and possibly the "ponder" token when finishing the search.
1950 else if (command == "ponderhit")
1952 // The opponent has played the expected move. GUI sends "ponderhit" if
1953 // we were told to ponder on the same move the opponent has played. We
1954 // should continue searching but switching from pondering to normal search.
1957 if (StopOnPonderhit)
1962 // Print search information
1966 else if (lastInfoTime > t)
1967 // HACK: Must be a new search where we searched less than
1968 // NodesBetweenPolls nodes during the first second of search.
1971 else if (t - lastInfoTime >= 1000)
1978 if (dbg_show_hit_rate)
1979 dbg_print_hit_rate();
1981 // Send info on searched nodes as soon as we return to root
1982 SendSearchedNodes = true;
1985 // Should we stop the search?
1989 bool stillAtFirstMove = FirstRootMove
1990 && !AspirationFailLow
1991 && t > TimeMgr.available_time();
1993 bool noMoreTime = t > TimeMgr.maximum_time()
1994 || stillAtFirstMove;
1996 if ( (UseTimeManagement && noMoreTime)
1997 || (ExactMaxTime && t >= ExactMaxTime)
1998 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2003 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2004 // while the program is pondering. The point is to work around a wrinkle in
2005 // the UCI protocol: When pondering, the engine is not allowed to give a
2006 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2007 // We simply wait here until one of these commands is sent, and return,
2008 // after which the bestmove and pondermove will be printed.
2010 void wait_for_stop_or_ponderhit() {
2012 std::string command;
2016 // Wait for a command from stdin
2017 if (!std::getline(std::cin, command))
2020 if (command == "quit")
2025 else if (command == "ponderhit" || command == "stop")
2031 // init_thread() is the function which is called when a new thread is
2032 // launched. It simply calls the idle_loop() function with the supplied
2033 // threadID. There are two versions of this function; one for POSIX
2034 // threads and one for Windows threads.
2036 #if !defined(_MSC_VER)
2038 void* init_thread(void* threadID) {
2040 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2046 DWORD WINAPI init_thread(LPVOID threadID) {
2048 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2055 /// The ThreadsManager class
2058 // read_uci_options() updates number of active threads and other internal
2059 // parameters according to the UCI options values. It is called before
2060 // to start a new search.
2062 void ThreadsManager::read_uci_options() {
2064 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2065 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2066 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2067 activeThreads = Options["Threads"].value<int>();
2071 // idle_loop() is where the threads are parked when they have no work to do.
2072 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2073 // object for which the current thread is the master.
2075 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2077 assert(threadID >= 0 && threadID < MAX_THREADS);
2080 bool allFinished = false;
2084 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2085 // master should exit as last one.
2086 if (allThreadsShouldExit)
2089 threads[threadID].state = THREAD_TERMINATED;
2093 // If we are not thinking, wait for a condition to be signaled
2094 // instead of wasting CPU time polling for work.
2095 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2096 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2098 assert(!sp || useSleepingThreads);
2099 assert(threadID != 0 || useSleepingThreads);
2101 if (threads[threadID].state == THREAD_INITIALIZING)
2102 threads[threadID].state = THREAD_AVAILABLE;
2104 // Grab the lock to avoid races with wake_sleeping_thread()
2105 lock_grab(&sleepLock[threadID]);
2107 // If we are master and all slaves have finished do not go to sleep
2108 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2109 allFinished = (i == activeThreads);
2111 if (allFinished || allThreadsShouldExit)
2113 lock_release(&sleepLock[threadID]);
2117 // Do sleep here after retesting sleep conditions
2118 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2119 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2121 lock_release(&sleepLock[threadID]);
2124 // If this thread has been assigned work, launch a search
2125 if (threads[threadID].state == THREAD_WORKISWAITING)
2127 assert(!allThreadsShouldExit);
2129 threads[threadID].state = THREAD_SEARCHING;
2131 // Here we call search() with SplitPoint template parameter set to true
2132 SplitPoint* tsp = threads[threadID].splitPoint;
2133 Position pos(*tsp->pos, threadID);
2134 SearchStack* ss = tsp->sstack[threadID] + 1;
2138 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2140 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2142 assert(threads[threadID].state == THREAD_SEARCHING);
2144 threads[threadID].state = THREAD_AVAILABLE;
2146 // Wake up master thread so to allow it to return from the idle loop in
2147 // case we are the last slave of the split point.
2148 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2149 wake_sleeping_thread(tsp->master);
2152 // If this thread is the master of a split point and all slaves have
2153 // finished their work at this split point, return from the idle loop.
2154 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2155 allFinished = (i == activeThreads);
2159 // Because sp->slaves[] is reset under lock protection,
2160 // be sure sp->lock has been released before to return.
2161 lock_grab(&(sp->lock));
2162 lock_release(&(sp->lock));
2164 // In helpful master concept a master can help only a sub-tree, and
2165 // because here is all finished is not possible master is booked.
2166 assert(threads[threadID].state == THREAD_AVAILABLE);
2168 threads[threadID].state = THREAD_SEARCHING;
2175 // init_threads() is called during startup. It launches all helper threads,
2176 // and initializes the split point stack and the global locks and condition
2179 void ThreadsManager::init_threads() {
2181 int i, arg[MAX_THREADS];
2184 // Initialize global locks
2187 for (i = 0; i < MAX_THREADS; i++)
2189 lock_init(&sleepLock[i]);
2190 cond_init(&sleepCond[i]);
2193 // Initialize splitPoints[] locks
2194 for (i = 0; i < MAX_THREADS; i++)
2195 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2196 lock_init(&(threads[i].splitPoints[j].lock));
2198 // Will be set just before program exits to properly end the threads
2199 allThreadsShouldExit = false;
2201 // Threads will be put all threads to sleep as soon as created
2204 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2205 threads[0].state = THREAD_SEARCHING;
2206 for (i = 1; i < MAX_THREADS; i++)
2207 threads[i].state = THREAD_INITIALIZING;
2209 // Launch the helper threads
2210 for (i = 1; i < MAX_THREADS; i++)
2214 #if !defined(_MSC_VER)
2215 pthread_t pthread[1];
2216 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2217 pthread_detach(pthread[0]);
2219 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2223 cout << "Failed to create thread number " << i << endl;
2227 // Wait until the thread has finished launching and is gone to sleep
2228 while (threads[i].state == THREAD_INITIALIZING) {}
2233 // exit_threads() is called when the program exits. It makes all the
2234 // helper threads exit cleanly.
2236 void ThreadsManager::exit_threads() {
2238 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2240 // Wake up all the threads and waits for termination
2241 for (int i = 1; i < MAX_THREADS; i++)
2243 wake_sleeping_thread(i);
2244 while (threads[i].state != THREAD_TERMINATED) {}
2247 // Now we can safely destroy the locks
2248 for (int i = 0; i < MAX_THREADS; i++)
2249 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2250 lock_destroy(&(threads[i].splitPoints[j].lock));
2252 lock_destroy(&mpLock);
2254 // Now we can safely destroy the wait conditions
2255 for (int i = 0; i < MAX_THREADS; i++)
2257 lock_destroy(&sleepLock[i]);
2258 cond_destroy(&sleepCond[i]);
2263 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2264 // the thread's currently active split point, or in some ancestor of
2265 // the current split point.
2267 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2269 assert(threadID >= 0 && threadID < activeThreads);
2271 SplitPoint* sp = threads[threadID].splitPoint;
2273 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2278 // thread_is_available() checks whether the thread with threadID "slave" is
2279 // available to help the thread with threadID "master" at a split point. An
2280 // obvious requirement is that "slave" must be idle. With more than two
2281 // threads, this is not by itself sufficient: If "slave" is the master of
2282 // some active split point, it is only available as a slave to the other
2283 // threads which are busy searching the split point at the top of "slave"'s
2284 // split point stack (the "helpful master concept" in YBWC terminology).
2286 bool ThreadsManager::thread_is_available(int slave, int master) const {
2288 assert(slave >= 0 && slave < activeThreads);
2289 assert(master >= 0 && master < activeThreads);
2290 assert(activeThreads > 1);
2292 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2295 // Make a local copy to be sure doesn't change under our feet
2296 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2298 // No active split points means that the thread is available as
2299 // a slave for any other thread.
2300 if (localActiveSplitPoints == 0 || activeThreads == 2)
2303 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2304 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2305 // could have been set to 0 by another thread leading to an out of bound access.
2306 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2313 // available_thread_exists() tries to find an idle thread which is available as
2314 // a slave for the thread with threadID "master".
2316 bool ThreadsManager::available_thread_exists(int master) const {
2318 assert(master >= 0 && master < activeThreads);
2319 assert(activeThreads > 1);
2321 for (int i = 0; i < activeThreads; i++)
2322 if (thread_is_available(i, master))
2329 // split() does the actual work of distributing the work at a node between
2330 // several available threads. If it does not succeed in splitting the
2331 // node (because no idle threads are available, or because we have no unused
2332 // split point objects), the function immediately returns. If splitting is
2333 // possible, a SplitPoint object is initialized with all the data that must be
2334 // copied to the helper threads and we tell our helper threads that they have
2335 // been assigned work. This will cause them to instantly leave their idle loops and
2336 // call search().When all threads have returned from search() then split() returns.
2338 template <bool Fake>
2339 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2340 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2341 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2342 assert(pos.is_ok());
2343 assert(ply > 0 && ply < PLY_MAX);
2344 assert(*bestValue >= -VALUE_INFINITE);
2345 assert(*bestValue <= *alpha);
2346 assert(*alpha < beta);
2347 assert(beta <= VALUE_INFINITE);
2348 assert(depth > DEPTH_ZERO);
2349 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2350 assert(activeThreads > 1);
2352 int i, master = pos.thread();
2353 Thread& masterThread = threads[master];
2357 // If no other thread is available to help us, or if we have too many
2358 // active split points, don't split.
2359 if ( !available_thread_exists(master)
2360 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2362 lock_release(&mpLock);
2366 // Pick the next available split point object from the split point stack
2367 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2369 // Initialize the split point object
2370 splitPoint.parent = masterThread.splitPoint;
2371 splitPoint.master = master;
2372 splitPoint.betaCutoff = false;
2373 splitPoint.ply = ply;
2374 splitPoint.depth = depth;
2375 splitPoint.threatMove = threatMove;
2376 splitPoint.mateThreat = mateThreat;
2377 splitPoint.alpha = *alpha;
2378 splitPoint.beta = beta;
2379 splitPoint.pvNode = pvNode;
2380 splitPoint.bestValue = *bestValue;
2382 splitPoint.moveCount = moveCount;
2383 splitPoint.pos = &pos;
2384 splitPoint.nodes = 0;
2385 splitPoint.parentSstack = ss;
2386 for (i = 0; i < activeThreads; i++)
2387 splitPoint.slaves[i] = 0;
2389 masterThread.splitPoint = &splitPoint;
2391 // If we are here it means we are not available
2392 assert(masterThread.state != THREAD_AVAILABLE);
2394 int workersCnt = 1; // At least the master is included
2396 // Allocate available threads setting state to THREAD_BOOKED
2397 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2398 if (thread_is_available(i, master))
2400 threads[i].state = THREAD_BOOKED;
2401 threads[i].splitPoint = &splitPoint;
2402 splitPoint.slaves[i] = 1;
2406 assert(Fake || workersCnt > 1);
2408 // We can release the lock because slave threads are already booked and master is not available
2409 lock_release(&mpLock);
2411 // Tell the threads that they have work to do. This will make them leave
2412 // their idle loop. But before copy search stack tail for each thread.
2413 for (i = 0; i < activeThreads; i++)
2414 if (i == master || splitPoint.slaves[i])
2416 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2418 assert(i == master || threads[i].state == THREAD_BOOKED);
2420 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2422 if (useSleepingThreads && i != master)
2423 wake_sleeping_thread(i);
2426 // Everything is set up. The master thread enters the idle loop, from
2427 // which it will instantly launch a search, because its state is
2428 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2429 // idle loop, which means that the main thread will return from the idle
2430 // loop when all threads have finished their work at this split point.
2431 idle_loop(master, &splitPoint);
2433 // We have returned from the idle loop, which means that all threads are
2434 // finished. Update alpha and bestValue, and return.
2437 *alpha = splitPoint.alpha;
2438 *bestValue = splitPoint.bestValue;
2439 masterThread.activeSplitPoints--;
2440 masterThread.splitPoint = splitPoint.parent;
2441 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2443 lock_release(&mpLock);
2447 // wake_sleeping_thread() wakes up the thread with the given threadID
2448 // when it is time to start a new search.
2450 void ThreadsManager::wake_sleeping_thread(int threadID) {
2452 lock_grab(&sleepLock[threadID]);
2453 cond_signal(&sleepCond[threadID]);
2454 lock_release(&sleepLock[threadID]);
2458 /// RootMove and RootMoveList method's definitions
2460 RootMove::RootMove() {
2463 pv_score = non_pv_score = -VALUE_INFINITE;
2467 RootMove& RootMove::operator=(const RootMove& rm) {
2469 const Move* src = rm.pv;
2472 // Avoid a costly full rm.pv[] copy
2473 do *dst++ = *src; while (*src++ != MOVE_NONE);
2476 pv_score = rm.pv_score;
2477 non_pv_score = rm.non_pv_score;
2481 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2482 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2483 // allow to always have a ponder move even when we fail high at root and also a
2484 // long PV to print that is important for position analysis.
2486 void RootMove::extract_pv_from_tt(Position& pos) {
2488 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2492 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2494 pos.do_move(pv[0], *st++);
2496 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2497 && tte->move() != MOVE_NONE
2498 && move_is_legal(pos, tte->move())
2500 && (!pos.is_draw() || ply < 2))
2502 pv[ply] = tte->move();
2503 pos.do_move(pv[ply++], *st++);
2505 pv[ply] = MOVE_NONE;
2507 do pos.undo_move(pv[--ply]); while (ply);
2510 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2511 // the PV back into the TT. This makes sure the old PV moves are searched
2512 // first, even if the old TT entries have been overwritten.
2514 void RootMove::insert_pv_in_tt(Position& pos) {
2516 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2519 Value v, m = VALUE_NONE;
2522 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2526 tte = TT.retrieve(k);
2528 // Don't overwrite exsisting correct entries
2529 if (!tte || tte->move() != pv[ply])
2531 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2532 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2534 pos.do_move(pv[ply], *st++);
2536 } while (pv[++ply] != MOVE_NONE);
2538 do pos.undo_move(pv[--ply]); while (ply);
2541 // pv_info_to_uci() returns a string with information on the current PV line
2542 // formatted according to UCI specification and eventually writes the info
2543 // to a log file. It is called at each iteration or after a new pv is found.
2545 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2547 std::stringstream s, l;
2550 while (*m != MOVE_NONE)
2553 s << "info depth " << depth / ONE_PLY
2554 << " seldepth " << int(m - pv)
2555 << " multipv " << pvLine + 1
2556 << " score " << value_to_uci(pv_score)
2557 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2558 << " time " << current_search_time()
2559 << " nodes " << pos.nodes_searched()
2560 << " nps " << nps(pos)
2561 << " pv " << l.str();
2563 if (UseLogFile && pvLine == 0)
2565 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2566 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2568 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2574 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2576 MoveStack mlist[MOVES_MAX];
2580 bestMoveChanges = 0;
2582 // Generate all legal moves and score them
2583 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2584 qsearch_scoring(pos, mlist, last);
2586 // Add each move to the RootMoveList's vector
2587 for (MoveStack* cur = mlist; cur != last; cur++)
2589 // If we have a searchMoves[] list then verify cur->move
2590 // is in the list before to add it.
2591 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2593 if (searchMoves[0] && *sm != cur->move)
2597 rm.pv[0] = cur->move;
2598 rm.pv[1] = MOVE_NONE;
2599 rm.pv_score = Value(cur->score);