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 // Is one move significantly better than others after initial scoring ?
638 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
639 easyMove = Rml[0].pv[0];
641 // Iterative deepening loop
642 while (++iteration <= PLY_MAX && !StopRequest)
644 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
645 depth = (iteration - 1) * ONE_PLY;
647 if (MaxDepth && depth > MaxDepth * ONE_PLY)
650 cout << "info depth " << depth / ONE_PLY << endl;
652 // Calculate dynamic aspiration window based on previous iterations
653 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
655 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
656 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
658 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
659 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
661 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
662 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
665 // Start with a small aspiration window and, in case of fail high/low,
666 // research with bigger window until not failing high/low anymore.
669 // Search starting from ss+1 to allow calling update_gains()
670 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
672 // Send PV line to GUI and write to transposition table in case the
673 // relevant entries have been overwritten during the search.
674 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
676 Rml[i].insert_pv_in_tt(pos);
677 cout << set960(pos.is_chess960())
678 << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
681 // Value cannot be trusted. Break out immediately!
685 assert(value >= alpha);
687 // In case of failing high/low increase aspiration window and research,
688 // otherwise exit the fail high/low loop.
691 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
694 else if (value <= alpha)
696 AspirationFailLow = true;
697 StopOnPonderhit = false;
699 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
706 // Collect info about search result
707 bestMove = Rml[0].pv[0];
708 bestValues[iteration] = value;
709 bestMoveChanges[iteration] = Rml.bestMoveChanges;
711 // Drop the easy move if differs from the new best move
712 if (bestMove != easyMove)
713 easyMove = MOVE_NONE;
715 if (UseTimeManagement && !StopRequest)
718 bool noMoreTime = false;
720 // Stop search early when the last two iterations returned a mate score
722 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
723 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
726 // Stop search early if one move seems to be much better than the
727 // others or if there is only a single legal move. In this latter
728 // case we search up to Iteration 8 anyway to get a proper score.
730 && easyMove == bestMove
732 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
733 && current_search_time() > TimeMgr.available_time() / 16)
734 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
735 && current_search_time() > TimeMgr.available_time() / 32)))
738 // Add some extra time if the best move has changed during the last two iterations
739 if (iteration > 5 && iteration <= 50)
740 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
742 // Stop search if most of MaxSearchTime is consumed at the end of the
743 // iteration. We probably don't have enough time to search the first
744 // move at the next iteration anyway.
745 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
751 StopOnPonderhit = true;
758 *ponderMove = Rml[0].pv[1];
763 // search<>() is the main search function for both PV and non-PV nodes and for
764 // normal and SplitPoint nodes. When called just after a split point the search
765 // is simpler because we have already probed the hash table, done a null move
766 // search, and searched the first move before splitting, we don't have to repeat
767 // all this work again. We also don't need to store anything to the hash table
768 // here: This is taken care of after we return from the split point.
770 template <NodeType PvNode, bool SpNode, bool Root>
771 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
773 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
774 assert(beta > alpha && beta <= VALUE_INFINITE);
775 assert(PvNode || alpha == beta - 1);
776 assert((Root || ply > 0) && ply < PLY_MAX);
777 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
779 Move movesSearched[MOVES_MAX];
784 Move ttMove, move, excludedMove, threatMove;
787 Value bestValue, value, oldAlpha;
788 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
789 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
790 bool mateThreat = false;
791 int moveCount = 0, playedMoveCount = 0;
792 int threadID = pos.thread();
793 SplitPoint* sp = NULL;
795 refinedValue = bestValue = value = -VALUE_INFINITE;
797 isCheck = pos.is_check();
803 ttMove = excludedMove = MOVE_NONE;
804 threatMove = sp->threatMove;
805 mateThreat = sp->mateThreat;
806 goto split_point_start;
811 // Step 1. Initialize node and poll. Polling can abort search
812 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
813 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
815 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
821 // Step 2. Check for aborted search and immediate draw
823 || ThreadsMgr.cutoff_at_splitpoint(threadID)
825 || ply >= PLY_MAX - 1) && !Root)
828 // Step 3. Mate distance pruning
829 alpha = Max(value_mated_in(ply), alpha);
830 beta = Min(value_mate_in(ply+1), beta);
834 // Step 4. Transposition table lookup
835 // We don't want the score of a partial search to overwrite a previous full search
836 // TT value, so we use a different position key in case of an excluded move exists.
837 excludedMove = ss->excludedMove;
838 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
840 tte = TT.retrieve(posKey);
841 ttMove = tte ? tte->move() : MOVE_NONE;
843 // At PV nodes we check for exact scores, while at non-PV nodes we check for
844 // and return a fail high/low. Biggest advantage at probing at PV nodes is
845 // to have a smooth experience in analysis mode.
848 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
849 : ok_to_use_TT(tte, depth, beta, ply)))
852 ss->bestMove = ttMove; // Can be MOVE_NONE
853 return value_from_tt(tte->value(), ply);
856 // Step 5. Evaluate the position statically and
857 // update gain statistics of parent move.
859 ss->eval = ss->evalMargin = VALUE_NONE;
862 assert(tte->static_value() != VALUE_NONE);
864 ss->eval = tte->static_value();
865 ss->evalMargin = tte->static_value_margin();
866 refinedValue = refine_eval(tte, ss->eval, ply);
870 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
871 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
874 // Save gain for the parent non-capture move
875 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
877 // Step 6. Razoring (is omitted in PV nodes)
879 && depth < RazorDepth
881 && refinedValue < beta - razor_margin(depth)
882 && ttMove == MOVE_NONE
883 && !value_is_mate(beta)
884 && !pos.has_pawn_on_7th(pos.side_to_move()))
886 Value rbeta = beta - razor_margin(depth);
887 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
889 // Logically we should return (v + razor_margin(depth)), but
890 // surprisingly this did slightly weaker in tests.
894 // Step 7. Static null move pruning (is omitted in PV nodes)
895 // We're betting that the opponent doesn't have a move that will reduce
896 // the score by more than futility_margin(depth) if we do a null move.
899 && depth < RazorDepth
901 && refinedValue >= beta + futility_margin(depth, 0)
902 && !value_is_mate(beta)
903 && pos.non_pawn_material(pos.side_to_move()))
904 return refinedValue - futility_margin(depth, 0);
906 // Step 8. Null move search with verification search (is omitted in PV nodes)
911 && refinedValue >= beta
912 && !value_is_mate(beta)
913 && pos.non_pawn_material(pos.side_to_move()))
915 ss->currentMove = MOVE_NULL;
917 // Null move dynamic reduction based on depth
918 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
920 // Null move dynamic reduction based on value
921 if (refinedValue - beta > PawnValueMidgame)
924 pos.do_null_move(st);
925 (ss+1)->skipNullMove = true;
926 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
927 (ss+1)->skipNullMove = false;
928 pos.undo_null_move();
930 if (nullValue >= beta)
932 // Do not return unproven mate scores
933 if (nullValue >= value_mate_in(PLY_MAX))
936 if (depth < 6 * ONE_PLY)
939 // Do verification search at high depths
940 ss->skipNullMove = true;
941 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
942 ss->skipNullMove = false;
949 // The null move failed low, which means that we may be faced with
950 // some kind of threat. If the previous move was reduced, check if
951 // the move that refuted the null move was somehow connected to the
952 // move which was reduced. If a connection is found, return a fail
953 // low score (which will cause the reduced move to fail high in the
954 // parent node, which will trigger a re-search with full depth).
955 if (nullValue == value_mated_in(ply + 2))
958 threatMove = (ss+1)->bestMove;
959 if ( depth < ThreatDepth
961 && threatMove != MOVE_NONE
962 && connected_moves(pos, (ss-1)->currentMove, threatMove))
967 // Step 9. Internal iterative deepening
968 if ( depth >= IIDDepth[PvNode]
969 && ttMove == MOVE_NONE
970 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
972 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
974 ss->skipNullMove = true;
975 search<PvNode>(pos, ss, alpha, beta, d, ply);
976 ss->skipNullMove = false;
978 ttMove = ss->bestMove;
979 tte = TT.retrieve(posKey);
982 // Expensive mate threat detection (only for PV nodes)
984 mateThreat = pos.has_mate_threat();
986 split_point_start: // At split points actual search starts from here
988 // Initialize a MovePicker object for the current position
989 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
991 ss->bestMove = MOVE_NONE;
992 futilityBase = ss->eval + ss->evalMargin;
993 singularExtensionNode = !Root
995 && depth >= SingularExtensionDepth[PvNode]
998 && !excludedMove // Do not allow recursive singular extension search
999 && (tte->type() & VALUE_TYPE_LOWER)
1000 && tte->depth() >= depth - 3 * ONE_PLY;
1003 lock_grab(&(sp->lock));
1004 bestValue = sp->bestValue;
1007 // Step 10. Loop through moves
1008 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1009 while ( bestValue < beta
1010 && (move = mp.get_next_move()) != MOVE_NONE
1011 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1013 assert(move_is_ok(move));
1017 moveCount = ++sp->moveCount;
1018 lock_release(&(sp->lock));
1020 else if (move == excludedMove)
1027 // This is used by time management
1028 FirstRootMove = (moveCount == 1);
1030 // Save the current node count before the move is searched
1031 nodes = pos.nodes_searched();
1033 // If it's time to send nodes info, do it here where we have the
1034 // correct accumulated node counts searched by each thread.
1035 if (SendSearchedNodes)
1037 SendSearchedNodes = false;
1038 cout << "info nodes " << nodes
1039 << " nps " << nps(pos)
1040 << " time " << current_search_time() << endl;
1043 if (current_search_time() >= 1000)
1044 cout << "info currmove " << move
1045 << " currmovenumber " << moveCount << endl;
1048 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1049 moveIsCheck = pos.move_is_check(move, ci);
1050 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1052 // Step 11. Decide the new search depth
1053 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1055 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1056 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1057 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1058 // lower then ttValue minus a margin then we extend ttMove.
1059 if ( singularExtensionNode
1060 && move == tte->move()
1063 Value ttValue = value_from_tt(tte->value(), ply);
1065 if (abs(ttValue) < VALUE_KNOWN_WIN)
1067 Value b = ttValue - SingularExtensionMargin;
1068 ss->excludedMove = move;
1069 ss->skipNullMove = true;
1070 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1071 ss->skipNullMove = false;
1072 ss->excludedMove = MOVE_NONE;
1073 ss->bestMove = MOVE_NONE;
1079 // Update current move (this must be done after singular extension search)
1080 ss->currentMove = move;
1081 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1083 // Step 12. Futility pruning (is omitted in PV nodes)
1085 && !captureOrPromotion
1089 && !move_is_castle(move))
1091 // Move count based pruning
1092 if ( moveCount >= futility_move_count(depth)
1093 && !(threatMove && connected_threat(pos, move, threatMove))
1094 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1097 lock_grab(&(sp->lock));
1102 // Value based pruning
1103 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1104 // but fixing this made program slightly weaker.
1105 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1106 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1107 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1109 if (futilityValueScaled < beta)
1113 lock_grab(&(sp->lock));
1114 if (futilityValueScaled > sp->bestValue)
1115 sp->bestValue = bestValue = futilityValueScaled;
1117 else if (futilityValueScaled > bestValue)
1118 bestValue = futilityValueScaled;
1123 // Prune moves with negative SEE at low depths
1124 if ( predictedDepth < 2 * ONE_PLY
1125 && bestValue > value_mated_in(PLY_MAX)
1126 && pos.see_sign(move) < 0)
1129 lock_grab(&(sp->lock));
1135 // Step 13. Make the move
1136 pos.do_move(move, st, ci, moveIsCheck);
1138 if (!SpNode && !captureOrPromotion)
1139 movesSearched[playedMoveCount++] = move;
1141 // Step extra. pv search (only in PV nodes)
1142 // The first move in list is the expected PV
1145 // Aspiration window is disabled in multi-pv case
1146 if (Root && MultiPV > 1)
1147 alpha = -VALUE_INFINITE;
1149 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1153 // Step 14. Reduced depth search
1154 // If the move fails high will be re-searched at full depth.
1155 bool doFullDepthSearch = true;
1157 if ( depth >= 3 * ONE_PLY
1158 && !captureOrPromotion
1160 && !move_is_castle(move)
1161 && ss->killers[0] != move
1162 && ss->killers[1] != move)
1164 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1165 : reduction<PvNode>(depth, moveCount);
1168 alpha = SpNode ? sp->alpha : alpha;
1169 Depth d = newDepth - ss->reduction;
1170 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1172 doFullDepthSearch = (value > alpha);
1174 ss->reduction = DEPTH_ZERO; // Restore original reduction
1177 // Step 15. Full depth search
1178 if (doFullDepthSearch)
1180 alpha = SpNode ? sp->alpha : alpha;
1181 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1183 // Step extra. pv search (only in PV nodes)
1184 // Search only for possible new PV nodes, if instead value >= beta then
1185 // parent node fails low with value <= alpha and tries another move.
1186 if (PvNode && value > alpha && (Root || value < beta))
1187 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1191 // Step 16. Undo move
1192 pos.undo_move(move);
1194 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1196 // Step 17. Check for new best move
1199 lock_grab(&(sp->lock));
1200 bestValue = sp->bestValue;
1204 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1209 sp->bestValue = value;
1213 if (PvNode && value < beta) // We want always alpha < beta
1221 sp->betaCutoff = true;
1223 if (value == value_mate_in(ply + 1))
1224 ss->mateKiller = move;
1226 ss->bestMove = move;
1229 sp->parentSstack->bestMove = move;
1235 // To avoid to exit with bestValue == -VALUE_INFINITE
1236 if (value > bestValue)
1239 // Finished searching the move. If StopRequest is true, the search
1240 // was aborted because the user interrupted the search or because we
1241 // ran out of time. In this case, the return value of the search cannot
1242 // be trusted, and we break out of the loop without updating the best
1247 // Remember searched nodes counts for this move
1248 mp.rm->nodes += pos.nodes_searched() - nodes;
1250 // Step 17. Check for new best move
1251 if (!isPvMove && value <= alpha)
1252 mp.rm->pv_score = -VALUE_INFINITE;
1255 // PV move or new best move!
1258 ss->bestMove = move;
1259 mp.rm->pv_score = value;
1260 mp.rm->extract_pv_from_tt(pos);
1262 // We record how often the best move has been changed in each
1263 // iteration. This information is used for time managment: When
1264 // the best move changes frequently, we allocate some more time.
1265 if (!isPvMove && MultiPV == 1)
1266 Rml.bestMoveChanges++;
1268 Rml.sort_multipv(moveCount);
1270 // Update alpha. In multi-pv we don't use aspiration window, so
1271 // set alpha equal to minimum score among the PV lines.
1273 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1274 else if (value > alpha)
1277 } // PV move or new best move
1280 // Step 18. Check for split
1283 && depth >= ThreadsMgr.min_split_depth()
1284 && ThreadsMgr.active_threads() > 1
1286 && ThreadsMgr.available_thread_exists(threadID)
1288 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1289 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1290 threatMove, mateThreat, moveCount, &mp, PvNode);
1293 // Step 19. Check for mate and stalemate
1294 // All legal moves have been searched and if there are
1295 // no legal moves, it must be mate or stalemate.
1296 // If one move was excluded return fail low score.
1297 if (!SpNode && !moveCount)
1298 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1300 // Step 20. Update tables
1301 // If the search is not aborted, update the transposition table,
1302 // history counters, and killer moves.
1303 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1305 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1306 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1307 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1309 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1311 // Update killers and history only for non capture moves that fails high
1312 if ( bestValue >= beta
1313 && !pos.move_is_capture_or_promotion(move))
1315 update_history(pos, move, depth, movesSearched, playedMoveCount);
1316 update_killers(move, ss->killers);
1322 // Here we have the lock still grabbed
1323 sp->slaves[threadID] = 0;
1324 sp->nodes += pos.nodes_searched();
1325 lock_release(&(sp->lock));
1328 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1333 // qsearch() is the quiescence search function, which is called by the main
1334 // search function when the remaining depth is zero (or, to be more precise,
1335 // less than ONE_PLY).
1337 template <NodeType PvNode>
1338 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1340 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1341 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1342 assert(PvNode || alpha == beta - 1);
1344 assert(ply > 0 && ply < PLY_MAX);
1345 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1349 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1350 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1353 Value oldAlpha = alpha;
1355 ss->bestMove = ss->currentMove = MOVE_NONE;
1357 // Check for an instant draw or maximum ply reached
1358 if (pos.is_draw() || ply >= PLY_MAX - 1)
1361 // Decide whether or not to include checks, this fixes also the type of
1362 // TT entry depth that we are going to use. Note that in qsearch we use
1363 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1364 isCheck = pos.is_check();
1365 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1367 // Transposition table lookup. At PV nodes, we don't use the TT for
1368 // pruning, but only for move ordering.
1369 tte = TT.retrieve(pos.get_key());
1370 ttMove = (tte ? tte->move() : MOVE_NONE);
1372 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1374 ss->bestMove = ttMove; // Can be MOVE_NONE
1375 return value_from_tt(tte->value(), ply);
1378 // Evaluate the position statically
1381 bestValue = futilityBase = -VALUE_INFINITE;
1382 ss->eval = evalMargin = VALUE_NONE;
1383 enoughMaterial = false;
1389 assert(tte->static_value() != VALUE_NONE);
1391 evalMargin = tte->static_value_margin();
1392 ss->eval = bestValue = tte->static_value();
1395 ss->eval = bestValue = evaluate(pos, evalMargin);
1397 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1399 // Stand pat. Return immediately if static value is at least beta
1400 if (bestValue >= beta)
1403 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1408 if (PvNode && bestValue > alpha)
1411 // Futility pruning parameters, not needed when in check
1412 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1413 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1416 // Initialize a MovePicker object for the current position, and prepare
1417 // to search the moves. Because the depth is <= 0 here, only captures,
1418 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1420 MovePicker mp(pos, ttMove, depth, H);
1423 // Loop through the moves until no moves remain or a beta cutoff occurs
1424 while ( alpha < beta
1425 && (move = mp.get_next_move()) != MOVE_NONE)
1427 assert(move_is_ok(move));
1429 moveIsCheck = pos.move_is_check(move, ci);
1437 && !move_is_promotion(move)
1438 && !pos.move_is_passed_pawn_push(move))
1440 futilityValue = futilityBase
1441 + pos.endgame_value_of_piece_on(move_to(move))
1442 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1444 if (futilityValue < alpha)
1446 if (futilityValue > bestValue)
1447 bestValue = futilityValue;
1452 // Detect non-capture evasions that are candidate to be pruned
1453 evasionPrunable = isCheck
1454 && bestValue > value_mated_in(PLY_MAX)
1455 && !pos.move_is_capture(move)
1456 && !pos.can_castle(pos.side_to_move());
1458 // Don't search moves with negative SEE values
1460 && (!isCheck || evasionPrunable)
1462 && !move_is_promotion(move)
1463 && pos.see_sign(move) < 0)
1466 // Don't search useless checks
1471 && !pos.move_is_capture_or_promotion(move)
1472 && ss->eval + PawnValueMidgame / 4 < beta
1473 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1475 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1476 bestValue = ss->eval + PawnValueMidgame / 4;
1481 // Update current move
1482 ss->currentMove = move;
1484 // Make and search the move
1485 pos.do_move(move, st, ci, moveIsCheck);
1486 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1487 pos.undo_move(move);
1489 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1492 if (value > bestValue)
1498 ss->bestMove = move;
1503 // All legal moves have been searched. A special case: If we're in check
1504 // and no legal moves were found, it is checkmate.
1505 if (isCheck && bestValue == -VALUE_INFINITE)
1506 return value_mated_in(ply);
1508 // Update transposition table
1509 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1510 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1512 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1518 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1519 // it is used in RootMoveList to get an initial scoring.
1520 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1522 SearchStack ss[PLY_MAX_PLUS_2];
1525 memset(ss, 0, 4 * sizeof(SearchStack));
1526 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1528 for (MoveStack* cur = mlist; cur != last; cur++)
1530 ss[0].currentMove = cur->move;
1531 pos.do_move(cur->move, st);
1532 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1533 pos.undo_move(cur->move);
1538 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1539 // bestValue is updated only when returning false because in that case move
1542 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1544 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1545 Square from, to, ksq, victimSq;
1548 Value futilityValue, bv = *bestValue;
1550 from = move_from(move);
1552 them = opposite_color(pos.side_to_move());
1553 ksq = pos.king_square(them);
1554 kingAtt = pos.attacks_from<KING>(ksq);
1555 pc = pos.piece_on(from);
1557 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1558 oldAtt = pos.attacks_from(pc, from, occ);
1559 newAtt = pos.attacks_from(pc, to, occ);
1561 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1562 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1564 if (!(b && (b & (b - 1))))
1567 // Rule 2. Queen contact check is very dangerous
1568 if ( type_of_piece(pc) == QUEEN
1569 && bit_is_set(kingAtt, to))
1572 // Rule 3. Creating new double threats with checks
1573 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1577 victimSq = pop_1st_bit(&b);
1578 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1580 // Note that here we generate illegal "double move"!
1581 if ( futilityValue >= beta
1582 && pos.see_sign(make_move(from, victimSq)) >= 0)
1585 if (futilityValue > bv)
1589 // Update bestValue only if check is not dangerous (because we will prune the move)
1595 // connected_moves() tests whether two moves are 'connected' in the sense
1596 // that the first move somehow made the second move possible (for instance
1597 // if the moving piece is the same in both moves). The first move is assumed
1598 // to be the move that was made to reach the current position, while the
1599 // second move is assumed to be a move from the current position.
1601 bool connected_moves(const Position& pos, Move m1, Move m2) {
1603 Square f1, t1, f2, t2;
1606 assert(m1 && move_is_ok(m1));
1607 assert(m2 && move_is_ok(m2));
1609 // Case 1: The moving piece is the same in both moves
1615 // Case 2: The destination square for m2 was vacated by m1
1621 // Case 3: Moving through the vacated square
1622 if ( piece_is_slider(pos.piece_on(f2))
1623 && bit_is_set(squares_between(f2, t2), f1))
1626 // Case 4: The destination square for m2 is defended by the moving piece in m1
1627 p = pos.piece_on(t1);
1628 if (bit_is_set(pos.attacks_from(p, t1), t2))
1631 // Case 5: Discovered check, checking piece is the piece moved in m1
1632 if ( piece_is_slider(p)
1633 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1634 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1636 // discovered_check_candidates() works also if the Position's side to
1637 // move is the opposite of the checking piece.
1638 Color them = opposite_color(pos.side_to_move());
1639 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1641 if (bit_is_set(dcCandidates, f2))
1648 // value_is_mate() checks if the given value is a mate one eventually
1649 // compensated for the ply.
1651 bool value_is_mate(Value value) {
1653 assert(abs(value) <= VALUE_INFINITE);
1655 return value <= value_mated_in(PLY_MAX)
1656 || value >= value_mate_in(PLY_MAX);
1660 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1661 // "plies to mate from the current ply". Non-mate scores are unchanged.
1662 // The function is called before storing a value to the transposition table.
1664 Value value_to_tt(Value v, int ply) {
1666 if (v >= value_mate_in(PLY_MAX))
1669 if (v <= value_mated_in(PLY_MAX))
1676 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1677 // the transposition table to a mate score corrected for the current ply.
1679 Value value_from_tt(Value v, int ply) {
1681 if (v >= value_mate_in(PLY_MAX))
1684 if (v <= value_mated_in(PLY_MAX))
1691 // extension() decides whether a move should be searched with normal depth,
1692 // or with extended depth. Certain classes of moves (checking moves, in
1693 // particular) are searched with bigger depth than ordinary moves and in
1694 // any case are marked as 'dangerous'. Note that also if a move is not
1695 // extended, as example because the corresponding UCI option is set to zero,
1696 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1697 template <NodeType PvNode>
1698 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1699 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1701 assert(m != MOVE_NONE);
1703 Depth result = DEPTH_ZERO;
1704 *dangerous = moveIsCheck | mateThreat;
1708 if (moveIsCheck && pos.see_sign(m) >= 0)
1709 result += CheckExtension[PvNode];
1712 result += MateThreatExtension[PvNode];
1715 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1717 Color c = pos.side_to_move();
1718 if (relative_rank(c, move_to(m)) == RANK_7)
1720 result += PawnPushTo7thExtension[PvNode];
1723 if (pos.pawn_is_passed(c, move_to(m)))
1725 result += PassedPawnExtension[PvNode];
1730 if ( captureOrPromotion
1731 && pos.type_of_piece_on(move_to(m)) != PAWN
1732 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1733 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1734 && !move_is_promotion(m)
1737 result += PawnEndgameExtension[PvNode];
1742 && captureOrPromotion
1743 && pos.type_of_piece_on(move_to(m)) != PAWN
1744 && pos.see_sign(m) >= 0)
1746 result += ONE_PLY / 2;
1750 return Min(result, ONE_PLY);
1754 // connected_threat() tests whether it is safe to forward prune a move or if
1755 // is somehow coonected to the threat move returned by null search.
1757 bool connected_threat(const Position& pos, Move m, Move threat) {
1759 assert(move_is_ok(m));
1760 assert(threat && move_is_ok(threat));
1761 assert(!pos.move_is_check(m));
1762 assert(!pos.move_is_capture_or_promotion(m));
1763 assert(!pos.move_is_passed_pawn_push(m));
1765 Square mfrom, mto, tfrom, tto;
1767 mfrom = move_from(m);
1769 tfrom = move_from(threat);
1770 tto = move_to(threat);
1772 // Case 1: Don't prune moves which move the threatened piece
1776 // Case 2: If the threatened piece has value less than or equal to the
1777 // value of the threatening piece, don't prune move which defend it.
1778 if ( pos.move_is_capture(threat)
1779 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1780 || pos.type_of_piece_on(tfrom) == KING)
1781 && pos.move_attacks_square(m, tto))
1784 // Case 3: If the moving piece in the threatened move is a slider, don't
1785 // prune safe moves which block its ray.
1786 if ( piece_is_slider(pos.piece_on(tfrom))
1787 && bit_is_set(squares_between(tfrom, tto), mto)
1788 && pos.see_sign(m) >= 0)
1795 // ok_to_use_TT() returns true if a transposition table score
1796 // can be used at a given point in search.
1798 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1800 Value v = value_from_tt(tte->value(), ply);
1802 return ( tte->depth() >= depth
1803 || v >= Max(value_mate_in(PLY_MAX), beta)
1804 || v < Min(value_mated_in(PLY_MAX), beta))
1806 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1807 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1811 // refine_eval() returns the transposition table score if
1812 // possible otherwise falls back on static position evaluation.
1814 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1818 Value v = value_from_tt(tte->value(), ply);
1820 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1821 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1828 // update_history() registers a good move that produced a beta-cutoff
1829 // in history and marks as failures all the other moves of that ply.
1831 void update_history(const Position& pos, Move move, Depth depth,
1832 Move movesSearched[], int moveCount) {
1834 Value bonus = Value(int(depth) * int(depth));
1836 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1838 for (int i = 0; i < moveCount - 1; i++)
1840 m = movesSearched[i];
1844 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1849 // update_killers() add a good move that produced a beta-cutoff
1850 // among the killer moves of that ply.
1852 void update_killers(Move m, Move killers[]) {
1854 if (m != killers[0])
1856 killers[1] = killers[0];
1862 // update_gains() updates the gains table of a non-capture move given
1863 // the static position evaluation before and after the move.
1865 void update_gains(const Position& pos, Move m, Value before, Value after) {
1868 && before != VALUE_NONE
1869 && after != VALUE_NONE
1870 && pos.captured_piece_type() == PIECE_TYPE_NONE
1871 && !move_is_special(m))
1872 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1876 // value_to_uci() converts a value to a string suitable for use with the UCI
1877 // protocol specifications:
1879 // cp <x> The score from the engine's point of view in centipawns.
1880 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1881 // use negative values for y.
1883 std::string value_to_uci(Value v) {
1885 std::stringstream s;
1887 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1888 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1890 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1896 // current_search_time() returns the number of milliseconds which have passed
1897 // since the beginning of the current search.
1899 int current_search_time() {
1901 return get_system_time() - SearchStartTime;
1905 // nps() computes the current nodes/second count
1907 int nps(const Position& pos) {
1909 int t = current_search_time();
1910 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1914 // poll() performs two different functions: It polls for user input, and it
1915 // looks at the time consumed so far and decides if it's time to abort the
1918 void poll(const Position& pos) {
1920 static int lastInfoTime;
1921 int t = current_search_time();
1924 if (input_available())
1926 // We are line oriented, don't read single chars
1927 std::string command;
1929 if (!std::getline(std::cin, command))
1932 if (command == "quit")
1934 // Quit the program as soon as possible
1936 QuitRequest = StopRequest = true;
1939 else if (command == "stop")
1941 // Stop calculating as soon as possible, but still send the "bestmove"
1942 // and possibly the "ponder" token when finishing the search.
1946 else if (command == "ponderhit")
1948 // The opponent has played the expected move. GUI sends "ponderhit" if
1949 // we were told to ponder on the same move the opponent has played. We
1950 // should continue searching but switching from pondering to normal search.
1953 if (StopOnPonderhit)
1958 // Print search information
1962 else if (lastInfoTime > t)
1963 // HACK: Must be a new search where we searched less than
1964 // NodesBetweenPolls nodes during the first second of search.
1967 else if (t - lastInfoTime >= 1000)
1974 if (dbg_show_hit_rate)
1975 dbg_print_hit_rate();
1977 // Send info on searched nodes as soon as we return to root
1978 SendSearchedNodes = true;
1981 // Should we stop the search?
1985 bool stillAtFirstMove = FirstRootMove
1986 && !AspirationFailLow
1987 && t > TimeMgr.available_time();
1989 bool noMoreTime = t > TimeMgr.maximum_time()
1990 || stillAtFirstMove;
1992 if ( (UseTimeManagement && noMoreTime)
1993 || (ExactMaxTime && t >= ExactMaxTime)
1994 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1999 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2000 // while the program is pondering. The point is to work around a wrinkle in
2001 // the UCI protocol: When pondering, the engine is not allowed to give a
2002 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2003 // We simply wait here until one of these commands is sent, and return,
2004 // after which the bestmove and pondermove will be printed.
2006 void wait_for_stop_or_ponderhit() {
2008 std::string command;
2012 // Wait for a command from stdin
2013 if (!std::getline(std::cin, command))
2016 if (command == "quit")
2021 else if (command == "ponderhit" || command == "stop")
2027 // init_thread() is the function which is called when a new thread is
2028 // launched. It simply calls the idle_loop() function with the supplied
2029 // threadID. There are two versions of this function; one for POSIX
2030 // threads and one for Windows threads.
2032 #if !defined(_MSC_VER)
2034 void* init_thread(void* threadID) {
2036 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2042 DWORD WINAPI init_thread(LPVOID threadID) {
2044 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2051 /// The ThreadsManager class
2054 // read_uci_options() updates number of active threads and other internal
2055 // parameters according to the UCI options values. It is called before
2056 // to start a new search.
2058 void ThreadsManager::read_uci_options() {
2060 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2061 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2062 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2063 activeThreads = Options["Threads"].value<int>();
2067 // idle_loop() is where the threads are parked when they have no work to do.
2068 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2069 // object for which the current thread is the master.
2071 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2073 assert(threadID >= 0 && threadID < MAX_THREADS);
2076 bool allFinished = false;
2080 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2081 // master should exit as last one.
2082 if (allThreadsShouldExit)
2085 threads[threadID].state = THREAD_TERMINATED;
2089 // If we are not thinking, wait for a condition to be signaled
2090 // instead of wasting CPU time polling for work.
2091 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2092 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2094 assert(!sp || useSleepingThreads);
2095 assert(threadID != 0 || useSleepingThreads);
2097 if (threads[threadID].state == THREAD_INITIALIZING)
2098 threads[threadID].state = THREAD_AVAILABLE;
2100 // Grab the lock to avoid races with wake_sleeping_thread()
2101 lock_grab(&sleepLock[threadID]);
2103 // If we are master and all slaves have finished do not go to sleep
2104 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2105 allFinished = (i == activeThreads);
2107 if (allFinished || allThreadsShouldExit)
2109 lock_release(&sleepLock[threadID]);
2113 // Do sleep here after retesting sleep conditions
2114 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2115 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2117 lock_release(&sleepLock[threadID]);
2120 // If this thread has been assigned work, launch a search
2121 if (threads[threadID].state == THREAD_WORKISWAITING)
2123 assert(!allThreadsShouldExit);
2125 threads[threadID].state = THREAD_SEARCHING;
2127 // Here we call search() with SplitPoint template parameter set to true
2128 SplitPoint* tsp = threads[threadID].splitPoint;
2129 Position pos(*tsp->pos, threadID);
2130 SearchStack* ss = tsp->sstack[threadID] + 1;
2134 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2136 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2138 assert(threads[threadID].state == THREAD_SEARCHING);
2140 threads[threadID].state = THREAD_AVAILABLE;
2142 // Wake up master thread so to allow it to return from the idle loop in
2143 // case we are the last slave of the split point.
2144 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2145 wake_sleeping_thread(tsp->master);
2148 // If this thread is the master of a split point and all slaves have
2149 // finished their work at this split point, return from the idle loop.
2150 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2151 allFinished = (i == activeThreads);
2155 // Because sp->slaves[] is reset under lock protection,
2156 // be sure sp->lock has been released before to return.
2157 lock_grab(&(sp->lock));
2158 lock_release(&(sp->lock));
2160 // In helpful master concept a master can help only a sub-tree, and
2161 // because here is all finished is not possible master is booked.
2162 assert(threads[threadID].state == THREAD_AVAILABLE);
2164 threads[threadID].state = THREAD_SEARCHING;
2171 // init_threads() is called during startup. It launches all helper threads,
2172 // and initializes the split point stack and the global locks and condition
2175 void ThreadsManager::init_threads() {
2177 int i, arg[MAX_THREADS];
2180 // Initialize global locks
2183 for (i = 0; i < MAX_THREADS; i++)
2185 lock_init(&sleepLock[i]);
2186 cond_init(&sleepCond[i]);
2189 // Initialize splitPoints[] locks
2190 for (i = 0; i < MAX_THREADS; i++)
2191 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2192 lock_init(&(threads[i].splitPoints[j].lock));
2194 // Will be set just before program exits to properly end the threads
2195 allThreadsShouldExit = false;
2197 // Threads will be put all threads to sleep as soon as created
2200 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2201 threads[0].state = THREAD_SEARCHING;
2202 for (i = 1; i < MAX_THREADS; i++)
2203 threads[i].state = THREAD_INITIALIZING;
2205 // Launch the helper threads
2206 for (i = 1; i < MAX_THREADS; i++)
2210 #if !defined(_MSC_VER)
2211 pthread_t pthread[1];
2212 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2213 pthread_detach(pthread[0]);
2215 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2219 cout << "Failed to create thread number " << i << endl;
2223 // Wait until the thread has finished launching and is gone to sleep
2224 while (threads[i].state == THREAD_INITIALIZING) {}
2229 // exit_threads() is called when the program exits. It makes all the
2230 // helper threads exit cleanly.
2232 void ThreadsManager::exit_threads() {
2234 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2236 // Wake up all the threads and waits for termination
2237 for (int i = 1; i < MAX_THREADS; i++)
2239 wake_sleeping_thread(i);
2240 while (threads[i].state != THREAD_TERMINATED) {}
2243 // Now we can safely destroy the locks
2244 for (int i = 0; i < MAX_THREADS; i++)
2245 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2246 lock_destroy(&(threads[i].splitPoints[j].lock));
2248 lock_destroy(&mpLock);
2250 // Now we can safely destroy the wait conditions
2251 for (int i = 0; i < MAX_THREADS; i++)
2253 lock_destroy(&sleepLock[i]);
2254 cond_destroy(&sleepCond[i]);
2259 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2260 // the thread's currently active split point, or in some ancestor of
2261 // the current split point.
2263 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2265 assert(threadID >= 0 && threadID < activeThreads);
2267 SplitPoint* sp = threads[threadID].splitPoint;
2269 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2274 // thread_is_available() checks whether the thread with threadID "slave" is
2275 // available to help the thread with threadID "master" at a split point. An
2276 // obvious requirement is that "slave" must be idle. With more than two
2277 // threads, this is not by itself sufficient: If "slave" is the master of
2278 // some active split point, it is only available as a slave to the other
2279 // threads which are busy searching the split point at the top of "slave"'s
2280 // split point stack (the "helpful master concept" in YBWC terminology).
2282 bool ThreadsManager::thread_is_available(int slave, int master) const {
2284 assert(slave >= 0 && slave < activeThreads);
2285 assert(master >= 0 && master < activeThreads);
2286 assert(activeThreads > 1);
2288 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2291 // Make a local copy to be sure doesn't change under our feet
2292 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2294 // No active split points means that the thread is available as
2295 // a slave for any other thread.
2296 if (localActiveSplitPoints == 0 || activeThreads == 2)
2299 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2300 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2301 // could have been set to 0 by another thread leading to an out of bound access.
2302 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2309 // available_thread_exists() tries to find an idle thread which is available as
2310 // a slave for the thread with threadID "master".
2312 bool ThreadsManager::available_thread_exists(int master) const {
2314 assert(master >= 0 && master < activeThreads);
2315 assert(activeThreads > 1);
2317 for (int i = 0; i < activeThreads; i++)
2318 if (thread_is_available(i, master))
2325 // split() does the actual work of distributing the work at a node between
2326 // several available threads. If it does not succeed in splitting the
2327 // node (because no idle threads are available, or because we have no unused
2328 // split point objects), the function immediately returns. If splitting is
2329 // possible, a SplitPoint object is initialized with all the data that must be
2330 // copied to the helper threads and we tell our helper threads that they have
2331 // been assigned work. This will cause them to instantly leave their idle loops and
2332 // call search().When all threads have returned from search() then split() returns.
2334 template <bool Fake>
2335 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2336 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2337 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2338 assert(pos.is_ok());
2339 assert(ply > 0 && ply < PLY_MAX);
2340 assert(*bestValue >= -VALUE_INFINITE);
2341 assert(*bestValue <= *alpha);
2342 assert(*alpha < beta);
2343 assert(beta <= VALUE_INFINITE);
2344 assert(depth > DEPTH_ZERO);
2345 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2346 assert(activeThreads > 1);
2348 int i, master = pos.thread();
2349 Thread& masterThread = threads[master];
2353 // If no other thread is available to help us, or if we have too many
2354 // active split points, don't split.
2355 if ( !available_thread_exists(master)
2356 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2358 lock_release(&mpLock);
2362 // Pick the next available split point object from the split point stack
2363 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2365 // Initialize the split point object
2366 splitPoint.parent = masterThread.splitPoint;
2367 splitPoint.master = master;
2368 splitPoint.betaCutoff = false;
2369 splitPoint.ply = ply;
2370 splitPoint.depth = depth;
2371 splitPoint.threatMove = threatMove;
2372 splitPoint.mateThreat = mateThreat;
2373 splitPoint.alpha = *alpha;
2374 splitPoint.beta = beta;
2375 splitPoint.pvNode = pvNode;
2376 splitPoint.bestValue = *bestValue;
2378 splitPoint.moveCount = moveCount;
2379 splitPoint.pos = &pos;
2380 splitPoint.nodes = 0;
2381 splitPoint.parentSstack = ss;
2382 for (i = 0; i < activeThreads; i++)
2383 splitPoint.slaves[i] = 0;
2385 masterThread.splitPoint = &splitPoint;
2387 // If we are here it means we are not available
2388 assert(masterThread.state != THREAD_AVAILABLE);
2390 int workersCnt = 1; // At least the master is included
2392 // Allocate available threads setting state to THREAD_BOOKED
2393 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2394 if (thread_is_available(i, master))
2396 threads[i].state = THREAD_BOOKED;
2397 threads[i].splitPoint = &splitPoint;
2398 splitPoint.slaves[i] = 1;
2402 assert(Fake || workersCnt > 1);
2404 // We can release the lock because slave threads are already booked and master is not available
2405 lock_release(&mpLock);
2407 // Tell the threads that they have work to do. This will make them leave
2408 // their idle loop. But before copy search stack tail for each thread.
2409 for (i = 0; i < activeThreads; i++)
2410 if (i == master || splitPoint.slaves[i])
2412 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2414 assert(i == master || threads[i].state == THREAD_BOOKED);
2416 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2418 if (useSleepingThreads && i != master)
2419 wake_sleeping_thread(i);
2422 // Everything is set up. The master thread enters the idle loop, from
2423 // which it will instantly launch a search, because its state is
2424 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2425 // idle loop, which means that the main thread will return from the idle
2426 // loop when all threads have finished their work at this split point.
2427 idle_loop(master, &splitPoint);
2429 // We have returned from the idle loop, which means that all threads are
2430 // finished. Update alpha and bestValue, and return.
2433 *alpha = splitPoint.alpha;
2434 *bestValue = splitPoint.bestValue;
2435 masterThread.activeSplitPoints--;
2436 masterThread.splitPoint = splitPoint.parent;
2437 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2439 lock_release(&mpLock);
2443 // wake_sleeping_thread() wakes up the thread with the given threadID
2444 // when it is time to start a new search.
2446 void ThreadsManager::wake_sleeping_thread(int threadID) {
2448 lock_grab(&sleepLock[threadID]);
2449 cond_signal(&sleepCond[threadID]);
2450 lock_release(&sleepLock[threadID]);
2454 /// RootMove and RootMoveList method's definitions
2456 RootMove::RootMove() {
2459 pv_score = non_pv_score = -VALUE_INFINITE;
2463 RootMove& RootMove::operator=(const RootMove& rm) {
2465 const Move* src = rm.pv;
2468 // Avoid a costly full rm.pv[] copy
2469 do *dst++ = *src; while (*src++ != MOVE_NONE);
2472 pv_score = rm.pv_score;
2473 non_pv_score = rm.non_pv_score;
2477 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2478 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2479 // allow to always have a ponder move even when we fail high at root and also a
2480 // long PV to print that is important for position analysis.
2482 void RootMove::extract_pv_from_tt(Position& pos) {
2484 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2488 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2490 pos.do_move(pv[0], *st++);
2492 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2493 && tte->move() != MOVE_NONE
2494 && move_is_legal(pos, tte->move())
2496 && (!pos.is_draw() || ply < 2))
2498 pv[ply] = tte->move();
2499 pos.do_move(pv[ply++], *st++);
2501 pv[ply] = MOVE_NONE;
2503 do pos.undo_move(pv[--ply]); while (ply);
2506 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2507 // the PV back into the TT. This makes sure the old PV moves are searched
2508 // first, even if the old TT entries have been overwritten.
2510 void RootMove::insert_pv_in_tt(Position& pos) {
2512 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2515 Value v, m = VALUE_NONE;
2518 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2522 tte = TT.retrieve(k);
2524 // Don't overwrite exsisting correct entries
2525 if (!tte || tte->move() != pv[ply])
2527 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2528 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2530 pos.do_move(pv[ply], *st++);
2532 } while (pv[++ply] != MOVE_NONE);
2534 do pos.undo_move(pv[--ply]); while (ply);
2537 // pv_info_to_uci() returns a string with information on the current PV line
2538 // formatted according to UCI specification and eventually writes the info
2539 // to a log file. It is called at each iteration or after a new pv is found.
2541 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2543 std::stringstream s, l;
2546 while (*m != MOVE_NONE)
2549 s << "info depth " << depth / ONE_PLY
2550 << " seldepth " << int(m - pv)
2551 << " multipv " << pvLine + 1
2552 << " score " << value_to_uci(pv_score)
2553 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2554 << " time " << current_search_time()
2555 << " nodes " << pos.nodes_searched()
2556 << " nps " << nps(pos)
2557 << " pv " << l.str();
2559 if (UseLogFile && pvLine == 0)
2561 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2562 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2564 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2570 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2572 MoveStack mlist[MOVES_MAX];
2576 bestMoveChanges = 0;
2578 // Generate all legal moves and score them
2579 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2580 qsearch_scoring(pos, mlist, last);
2582 // Add each move to the RootMoveList's vector
2583 for (MoveStack* cur = mlist; cur != last; cur++)
2585 // If we have a searchMoves[] list then verify cur->move
2586 // is in the list before to add it.
2587 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2589 if (searchMoves[0] && *sm != cur->move)
2593 rm.pv[0] = cur->move;
2594 rm.pv[1] = MOVE_NONE;
2595 rm.pv_score = Value(cur->score);