2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
45 #include "ucioption.h"
51 //// Local definitions
57 enum NodeType { NonPV, PV };
59 // Set to true to force running with one thread.
60 // Used for debugging SMP code.
61 const bool FakeSplit = false;
63 // Fast lookup table of sliding pieces indexed by Piece
64 const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
65 inline bool piece_is_slider(Piece p) { return Slidings[p]; }
67 // ThreadsManager class is used to handle all the threads related stuff in search,
68 // init, starting, parking and, the most important, launching a slave thread at a
69 // split point are what this class does. All the access to shared thread data is
70 // done through this class, so that we avoid using global variables instead.
72 class ThreadsManager {
73 /* As long as the single ThreadsManager object is defined as a global we don't
74 need to explicitly initialize to zero its data members because variables with
75 static storage duration are automatically set to zero before enter main()
81 int min_split_depth() const { return minimumSplitDepth; }
82 int active_threads() const { return activeThreads; }
83 void set_active_threads(int cnt) { activeThreads = cnt; }
85 void read_uci_options();
86 bool available_thread_exists(int master) const;
87 bool thread_is_available(int slave, int master) const;
88 bool cutoff_at_splitpoint(int threadID) const;
89 void wake_sleeping_thread(int threadID);
90 void idle_loop(int threadID, SplitPoint* sp);
93 void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
94 Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
97 Depth minimumSplitDepth;
98 int maxThreadsPerSplitPoint;
99 bool useSleepingThreads;
101 volatile bool allThreadsShouldExit;
102 Thread threads[MAX_THREADS];
103 Lock mpLock, sleepLock[MAX_THREADS];
104 WaitCondition sleepCond[MAX_THREADS];
108 // RootMove struct is used for moves at the root at the tree. For each root
109 // move, we store two scores, a node count, and a PV (really a refutation
110 // in the case of moves which fail low). Value pv_score is normally set at
111 // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
112 // according to the order in which moves are returned by MovePicker.
117 RootMove(const RootMove& rm) { *this = rm; }
118 RootMove& operator=(const RootMove& rm);
120 // RootMove::operator<() is the comparison function used when
121 // sorting the moves. A move m1 is considered to be better
122 // than a move m2 if it has an higher pv_score, or if it has
123 // equal pv_score but m1 has the higher non_pv_score. In this
124 // way we are guaranteed that PV moves are always sorted as first.
125 bool operator<(const RootMove& m) const {
126 return pv_score != m.pv_score ? pv_score < m.pv_score
127 : non_pv_score < m.non_pv_score;
130 void extract_pv_from_tt(Position& pos);
131 void insert_pv_in_tt(Position& pos);
132 std::string pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine);
137 Move pv[PLY_MAX_PLUS_2];
141 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
142 // with an handful of methods above the standard ones.
144 struct RootMoveList : public std::vector<RootMove> {
146 typedef std::vector<RootMove> Base;
148 void init(Position& pos, Move searchMoves[]);
149 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
150 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
156 // When formatting a move for std::cout we must know if we are in Chess960
157 // or not. To keep using the handy operator<<() on the move the trick is to
158 // embed this flag in the stream itself. Function-like named enum set960 is
159 // used as a custom manipulator and the stream internal general-purpose array,
160 // accessed through ios_base::iword(), is used to pass the flag to the move's
161 // operator<<() that will use it to properly format castling moves.
164 std::ostream& operator<< (std::ostream& os, const set960& f) {
166 os.iword(0) = int(f);
171 // Overload operator << for moves to make it easier to print moves in
172 // coordinate notation compatible with UCI protocol.
173 std::ostream& operator<<(std::ostream& os, Move m) {
175 bool chess960 = (os.iword(0) != 0); // See set960()
176 return os << move_to_uci(m, chess960);
184 // Maximum depth for razoring
185 const Depth RazorDepth = 4 * ONE_PLY;
187 // Dynamic razoring margin based on depth
188 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
190 // Maximum depth for use of dynamic threat detection when null move fails low
191 const Depth ThreatDepth = 5 * ONE_PLY;
193 // Step 9. Internal iterative deepening
195 // Minimum depth for use of internal iterative deepening
196 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
198 // At Non-PV nodes we do an internal iterative deepening search
199 // when the static evaluation is bigger then beta - IIDMargin.
200 const Value IIDMargin = Value(0x100);
202 // Step 11. Decide the new search depth
204 // Extensions. Configurable UCI options
205 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
206 Depth CheckExtension[2], PawnPushTo7thExtension[2], PassedPawnExtension[2];
207 Depth PawnEndgameExtension[2], MateThreatExtension[2];
209 // Minimum depth for use of singular extension
210 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
212 // If the TT move is at least SingularExtensionMargin better than 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 management 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 they 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 << "\nSearching: " << pos.to_fen()
548 << "\ninfinite: " << infinite
549 << " ponder: " << ponder
550 << " time: " << myTime
551 << " increment: " << myIncrement
552 << " moves to go: " << movesToGo
556 // We're ready to start thinking. Call the iterative deepening loop function
557 Move ponderMove = MOVE_NONE;
558 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
560 // Print final search statistics
561 cout << "info nodes " << pos.nodes_searched()
562 << " nps " << nps(pos)
563 << " time " << current_search_time() << endl;
567 LogFile << "Nodes: " << pos.nodes_searched()
568 << "\nNodes/second: " << nps(pos)
569 << "\nBest move: " << move_to_san(pos, bestMove);
572 pos.do_move(bestMove, st);
573 LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
574 pos.undo_move(bestMove); // Return from think() with unchanged position
578 // This makes all the threads to go to sleep
579 ThreadsMgr.set_active_threads(1);
581 // If we are pondering or in infinite search, we shouldn't print the
582 // best move before we are told to do so.
583 if (!StopRequest && (Pondering || InfiniteSearch))
584 wait_for_stop_or_ponderhit();
586 // Could be both MOVE_NONE when searching on a stalemate position
587 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
595 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
596 // with increasing depth until the allocated thinking time has been consumed,
597 // user stops the search, or the maximum search depth is reached.
599 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
601 SearchStack ss[PLY_MAX_PLUS_2];
602 Value bestValues[PLY_MAX_PLUS_2];
603 int bestMoveChanges[PLY_MAX_PLUS_2];
604 int depth, researchCountFL, researchCountFH, aspirationDelta;
605 Value value, alpha, beta;
606 Move bestMove, easyMove;
608 // Moves to search are verified, scored and sorted
609 Rml.init(pos, searchMoves);
611 // Initialize FIXME move before Rml.init()
614 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
615 *ponderMove = bestMove = easyMove = MOVE_NONE;
616 depth = aspirationDelta = 0;
617 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
618 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
620 // Handle special case of searching on a mate/stalemate position
623 cout << "info depth 0 score "
624 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
630 // Is one move significantly better than others after initial scoring ?
632 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
633 easyMove = Rml[0].pv[0];
635 // Iterative deepening loop
636 while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
638 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
639 cout << "info depth " << depth << endl;
641 // Calculate dynamic aspiration window based on previous iterations
642 if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
644 int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
645 int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
647 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
648 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
650 alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
651 beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
654 // Start with a small aspiration window and, in case of fail high/low,
655 // research with bigger window until not failing high/low anymore.
658 // Search starting from ss+1 to allow calling update_gains()
659 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth * ONE_PLY, 0);
661 // Send PV line to GUI and write to transposition table in case the
662 // relevant entries have been overwritten during the search.
663 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
665 Rml[i].insert_pv_in_tt(pos);
666 cout << set960(pos.is_chess960())
667 << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
670 // Value cannot be trusted. Break out immediately!
674 assert(value >= alpha);
676 // In case of failing high/low increase aspiration window and research,
677 // otherwise exit the fail high/low loop.
680 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
683 else if (value <= alpha)
685 AspirationFailLow = true;
686 StopOnPonderhit = false;
688 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
695 // Collect info about search result
696 bestMove = Rml[0].pv[0];
697 bestValues[depth] = value;
698 bestMoveChanges[depth] = Rml.bestMoveChanges;
701 LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
703 // Drop the easy move if differs from the new best move
704 if (bestMove != easyMove)
705 easyMove = MOVE_NONE;
707 if (UseTimeManagement && !StopRequest)
710 bool noMoreTime = false;
712 // Stop search early when the last two iterations returned a mate score
714 && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100
715 && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100)
718 // Stop search early if one move seems to be much better than the
719 // others or if there is only a single legal move. In this latter
720 // case we search up to Iteration 8 anyway to get a proper score.
722 && easyMove == bestMove
724 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
725 && current_search_time() > TimeMgr.available_time() / 16)
726 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
727 && current_search_time() > TimeMgr.available_time() / 32)))
730 // Add some extra time if the best move has changed during the last two iterations
731 if (depth > 4 && depth < 50)
732 TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]);
734 // Stop search if most of MaxSearchTime is consumed at the end of the
735 // iteration. We probably don't have enough time to search the first
736 // move at the next iteration anyway.
737 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
743 StopOnPonderhit = true;
750 *ponderMove = Rml[0].pv[1];
755 // search<>() is the main search function for both PV and non-PV nodes and for
756 // normal and SplitPoint nodes. When called just after a split point the search
757 // is simpler because we have already probed the hash table, done a null move
758 // search, and searched the first move before splitting, we don't have to repeat
759 // all this work again. We also don't need to store anything to the hash table
760 // here: This is taken care of after we return from the split point.
762 template <NodeType PvNode, bool SpNode, bool Root>
763 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
765 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
766 assert(beta > alpha && beta <= VALUE_INFINITE);
767 assert(PvNode || alpha == beta - 1);
768 assert((Root || ply > 0) && ply < PLY_MAX);
769 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
771 Move movesSearched[MOVES_MAX];
776 Move ttMove, move, excludedMove, threatMove;
779 Value bestValue, value, oldAlpha;
780 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
781 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
782 bool mateThreat = false;
783 int moveCount = 0, playedMoveCount = 0;
784 int threadID = pos.thread();
785 SplitPoint* sp = NULL;
787 refinedValue = bestValue = value = -VALUE_INFINITE;
789 isCheck = pos.is_check();
795 ttMove = excludedMove = MOVE_NONE;
796 threatMove = sp->threatMove;
797 mateThreat = sp->mateThreat;
798 goto split_point_start;
803 // Step 1. Initialize node and poll. Polling can abort search
804 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
805 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
807 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
813 // Step 2. Check for aborted search and immediate draw
815 || ThreadsMgr.cutoff_at_splitpoint(threadID)
817 || ply >= PLY_MAX - 1) && !Root)
820 // Step 3. Mate distance pruning
821 alpha = Max(value_mated_in(ply), alpha);
822 beta = Min(value_mate_in(ply+1), beta);
826 // Step 4. Transposition table lookup
827 // We don't want the score of a partial search to overwrite a previous full search
828 // TT value, so we use a different position key in case of an excluded move.
829 excludedMove = ss->excludedMove;
830 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
832 tte = TT.retrieve(posKey);
833 ttMove = tte ? tte->move() : MOVE_NONE;
835 // At PV nodes we check for exact scores, while at non-PV nodes we check for
836 // and return a fail high/low. Biggest advantage at probing at PV nodes is
837 // to have a smooth experience in analysis mode.
840 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
841 : ok_to_use_TT(tte, depth, beta, ply)))
844 ss->bestMove = ttMove; // Can be MOVE_NONE
845 return value_from_tt(tte->value(), ply);
848 // Step 5. Evaluate the position statically and
849 // update gain statistics of parent move.
851 ss->eval = ss->evalMargin = VALUE_NONE;
854 assert(tte->static_value() != VALUE_NONE);
856 ss->eval = tte->static_value();
857 ss->evalMargin = tte->static_value_margin();
858 refinedValue = refine_eval(tte, ss->eval, ply);
862 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
863 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
866 // Save gain for the parent non-capture move
867 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
869 // Step 6. Razoring (is omitted in PV nodes)
871 && depth < RazorDepth
873 && refinedValue < beta - razor_margin(depth)
874 && ttMove == MOVE_NONE
875 && !value_is_mate(beta)
876 && !pos.has_pawn_on_7th(pos.side_to_move()))
878 Value rbeta = beta - razor_margin(depth);
879 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
881 // Logically we should return (v + razor_margin(depth)), but
882 // surprisingly this did slightly weaker in tests.
886 // Step 7. Static null move pruning (is omitted in PV nodes)
887 // We're betting that the opponent doesn't have a move that will reduce
888 // the score by more than futility_margin(depth) if we do a null move.
891 && depth < RazorDepth
893 && refinedValue >= beta + futility_margin(depth, 0)
894 && !value_is_mate(beta)
895 && pos.non_pawn_material(pos.side_to_move()))
896 return refinedValue - futility_margin(depth, 0);
898 // Step 8. Null move search with verification search (is omitted in PV nodes)
903 && refinedValue >= beta
904 && !value_is_mate(beta)
905 && pos.non_pawn_material(pos.side_to_move()))
907 ss->currentMove = MOVE_NULL;
909 // Null move dynamic reduction based on depth
910 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
912 // Null move dynamic reduction based on value
913 if (refinedValue - beta > PawnValueMidgame)
916 pos.do_null_move(st);
917 (ss+1)->skipNullMove = true;
918 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
919 (ss+1)->skipNullMove = false;
920 pos.undo_null_move();
922 if (nullValue >= beta)
924 // Do not return unproven mate scores
925 if (nullValue >= value_mate_in(PLY_MAX))
928 if (depth < 6 * ONE_PLY)
931 // Do verification search at high depths
932 ss->skipNullMove = true;
933 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
934 ss->skipNullMove = false;
941 // The null move failed low, which means that we may be faced with
942 // some kind of threat. If the previous move was reduced, check if
943 // the move that refuted the null move was somehow connected to the
944 // move which was reduced. If a connection is found, return a fail
945 // low score (which will cause the reduced move to fail high in the
946 // parent node, which will trigger a re-search with full depth).
947 if (nullValue == value_mated_in(ply + 2))
950 threatMove = (ss+1)->bestMove;
951 if ( depth < ThreatDepth
953 && threatMove != MOVE_NONE
954 && connected_moves(pos, (ss-1)->currentMove, threatMove))
959 // Step 9. Internal iterative deepening
960 if ( depth >= IIDDepth[PvNode]
961 && ttMove == MOVE_NONE
962 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
964 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
966 ss->skipNullMove = true;
967 search<PvNode>(pos, ss, alpha, beta, d, ply);
968 ss->skipNullMove = false;
970 ttMove = ss->bestMove;
971 tte = TT.retrieve(posKey);
974 // Expensive mate threat detection (only for PV nodes)
976 mateThreat = pos.has_mate_threat();
978 split_point_start: // At split points actual search starts from here
980 // Initialize a MovePicker object for the current position
981 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
983 ss->bestMove = MOVE_NONE;
984 futilityBase = ss->eval + ss->evalMargin;
985 singularExtensionNode = !Root
987 && depth >= SingularExtensionDepth[PvNode]
990 && !excludedMove // Do not allow recursive singular extension search
991 && (tte->type() & VALUE_TYPE_LOWER)
992 && tte->depth() >= depth - 3 * ONE_PLY;
995 lock_grab(&(sp->lock));
996 bestValue = sp->bestValue;
999 // Step 10. Loop through moves
1000 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1001 while ( bestValue < beta
1002 && (move = mp.get_next_move()) != MOVE_NONE
1003 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1005 assert(move_is_ok(move));
1009 moveCount = ++sp->moveCount;
1010 lock_release(&(sp->lock));
1012 else if (move == excludedMove)
1019 // This is used by time management
1020 FirstRootMove = (moveCount == 1);
1022 // Save the current node count before the move is searched
1023 nodes = pos.nodes_searched();
1025 // If it's time to send nodes info, do it here where we have the
1026 // correct accumulated node counts searched by each thread.
1027 if (SendSearchedNodes)
1029 SendSearchedNodes = false;
1030 cout << "info nodes " << nodes
1031 << " nps " << nps(pos)
1032 << " time " << current_search_time() << endl;
1035 if (current_search_time() >= 1000)
1036 cout << "info currmove " << move
1037 << " currmovenumber " << moveCount << endl;
1040 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1041 moveIsCheck = pos.move_is_check(move, ci);
1042 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1044 // Step 11. Decide the new search depth
1045 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1047 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1048 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1049 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1050 // lower than ttValue minus a margin then we extend ttMove.
1051 if ( singularExtensionNode
1052 && move == tte->move()
1055 Value ttValue = value_from_tt(tte->value(), ply);
1057 if (abs(ttValue) < VALUE_KNOWN_WIN)
1059 Value b = ttValue - SingularExtensionMargin;
1060 ss->excludedMove = move;
1061 ss->skipNullMove = true;
1062 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1063 ss->skipNullMove = false;
1064 ss->excludedMove = MOVE_NONE;
1065 ss->bestMove = MOVE_NONE;
1071 // Update current move (this must be done after singular extension search)
1072 ss->currentMove = move;
1073 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1075 // Step 12. Futility pruning (is omitted in PV nodes)
1077 && !captureOrPromotion
1081 && !move_is_castle(move))
1083 // Move count based pruning
1084 if ( moveCount >= futility_move_count(depth)
1085 && !(threatMove && connected_threat(pos, move, threatMove))
1086 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1089 lock_grab(&(sp->lock));
1094 // Value based pruning
1095 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1096 // but fixing this made program slightly weaker.
1097 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1098 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1099 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1101 if (futilityValueScaled < beta)
1105 lock_grab(&(sp->lock));
1106 if (futilityValueScaled > sp->bestValue)
1107 sp->bestValue = bestValue = futilityValueScaled;
1109 else if (futilityValueScaled > bestValue)
1110 bestValue = futilityValueScaled;
1115 // Prune moves with negative SEE at low depths
1116 if ( predictedDepth < 2 * ONE_PLY
1117 && bestValue > value_mated_in(PLY_MAX)
1118 && pos.see_sign(move) < 0)
1121 lock_grab(&(sp->lock));
1127 // Step 13. Make the move
1128 pos.do_move(move, st, ci, moveIsCheck);
1130 if (!SpNode && !captureOrPromotion)
1131 movesSearched[playedMoveCount++] = move;
1133 // Step extra. pv search (only in PV nodes)
1134 // The first move in list is the expected PV
1137 // Aspiration window is disabled in multi-pv case
1138 if (Root && MultiPV > 1)
1139 alpha = -VALUE_INFINITE;
1141 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1145 // Step 14. Reduced depth search
1146 // If the move fails high will be re-searched at full depth.
1147 bool doFullDepthSearch = true;
1149 if ( depth >= 3 * ONE_PLY
1150 && !captureOrPromotion
1152 && !move_is_castle(move)
1153 && ss->killers[0] != move
1154 && ss->killers[1] != move)
1156 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1157 : reduction<PvNode>(depth, moveCount);
1160 alpha = SpNode ? sp->alpha : alpha;
1161 Depth d = newDepth - ss->reduction;
1162 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1164 doFullDepthSearch = (value > alpha);
1166 ss->reduction = DEPTH_ZERO; // Restore original reduction
1169 // Step 15. Full depth search
1170 if (doFullDepthSearch)
1172 alpha = SpNode ? sp->alpha : alpha;
1173 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1175 // Step extra. pv search (only in PV nodes)
1176 // Search only for possible new PV nodes, if instead value >= beta then
1177 // parent node fails low with value <= alpha and tries another move.
1178 if (PvNode && value > alpha && (Root || value < beta))
1179 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1183 // Step 16. Undo move
1184 pos.undo_move(move);
1186 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1188 // Step 17. Check for new best move
1191 lock_grab(&(sp->lock));
1192 bestValue = sp->bestValue;
1196 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1201 sp->bestValue = value;
1205 if (PvNode && value < beta) // We want always alpha < beta
1213 sp->betaCutoff = true;
1215 if (value == value_mate_in(ply + 1))
1216 ss->mateKiller = move;
1218 ss->bestMove = move;
1221 sp->parentSstack->bestMove = move;
1227 // To avoid to exit with bestValue == -VALUE_INFINITE
1228 if (value > bestValue)
1231 // Finished searching the move. If StopRequest is true, the search
1232 // was aborted because the user interrupted the search or because we
1233 // ran out of time. In this case, the return value of the search cannot
1234 // be trusted, and we break out of the loop without updating the best
1239 // Remember searched nodes counts for this move
1240 mp.rm->nodes += pos.nodes_searched() - nodes;
1242 // Step 17. Check for new best move
1243 if (!isPvMove && value <= alpha)
1244 mp.rm->pv_score = -VALUE_INFINITE;
1247 // PV move or new best move!
1250 ss->bestMove = move;
1251 mp.rm->pv_score = value;
1252 mp.rm->extract_pv_from_tt(pos);
1254 // We record how often the best move has been changed in each
1255 // iteration. This information is used for time management: When
1256 // the best move changes frequently, we allocate some more time.
1257 if (!isPvMove && MultiPV == 1)
1258 Rml.bestMoveChanges++;
1260 Rml.sort_multipv(moveCount);
1262 // Update alpha. In multi-pv we don't use aspiration window, so
1263 // set alpha equal to minimum score among the PV lines.
1265 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1266 else if (value > alpha)
1269 } // PV move or new best move
1272 // Step 18. Check for split
1275 && depth >= ThreadsMgr.min_split_depth()
1276 && ThreadsMgr.active_threads() > 1
1278 && ThreadsMgr.available_thread_exists(threadID)
1280 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1281 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1282 threatMove, mateThreat, moveCount, &mp, PvNode);
1285 // Step 19. Check for mate and stalemate
1286 // All legal moves have been searched and if there are
1287 // no legal moves, it must be mate or stalemate.
1288 // If one move was excluded return fail low score.
1289 if (!SpNode && !moveCount)
1290 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1292 // Step 20. Update tables
1293 // If the search is not aborted, update the transposition table,
1294 // history counters, and killer moves.
1295 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1297 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1298 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1299 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1301 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1303 // Update killers and history only for non capture moves that fails high
1304 if ( bestValue >= beta
1305 && !pos.move_is_capture_or_promotion(move))
1307 update_history(pos, move, depth, movesSearched, playedMoveCount);
1308 update_killers(move, ss->killers);
1314 // Here we have the lock still grabbed
1315 sp->slaves[threadID] = 0;
1316 sp->nodes += pos.nodes_searched();
1317 lock_release(&(sp->lock));
1320 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1325 // qsearch() is the quiescence search function, which is called by the main
1326 // search function when the remaining depth is zero (or, to be more precise,
1327 // less than ONE_PLY).
1329 template <NodeType PvNode>
1330 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1332 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1333 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1334 assert(PvNode || alpha == beta - 1);
1336 assert(ply > 0 && ply < PLY_MAX);
1337 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1341 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1342 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1345 Value oldAlpha = alpha;
1347 ss->bestMove = ss->currentMove = MOVE_NONE;
1349 // Check for an instant draw or maximum ply reached
1350 if (pos.is_draw() || ply >= PLY_MAX - 1)
1353 // Decide whether or not to include checks, this fixes also the type of
1354 // TT entry depth that we are going to use. Note that in qsearch we use
1355 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1356 isCheck = pos.is_check();
1357 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1359 // Transposition table lookup. At PV nodes, we don't use the TT for
1360 // pruning, but only for move ordering.
1361 tte = TT.retrieve(pos.get_key());
1362 ttMove = (tte ? tte->move() : MOVE_NONE);
1364 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1366 ss->bestMove = ttMove; // Can be MOVE_NONE
1367 return value_from_tt(tte->value(), ply);
1370 // Evaluate the position statically
1373 bestValue = futilityBase = -VALUE_INFINITE;
1374 ss->eval = evalMargin = VALUE_NONE;
1375 enoughMaterial = false;
1381 assert(tte->static_value() != VALUE_NONE);
1383 evalMargin = tte->static_value_margin();
1384 ss->eval = bestValue = tte->static_value();
1387 ss->eval = bestValue = evaluate(pos, evalMargin);
1389 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1391 // Stand pat. Return immediately if static value is at least beta
1392 if (bestValue >= beta)
1395 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1400 if (PvNode && bestValue > alpha)
1403 // Futility pruning parameters, not needed when in check
1404 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1405 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1408 // Initialize a MovePicker object for the current position, and prepare
1409 // to search the moves. Because the depth is <= 0 here, only captures,
1410 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1412 MovePicker mp(pos, ttMove, depth, H);
1415 // Loop through the moves until no moves remain or a beta cutoff occurs
1416 while ( alpha < beta
1417 && (move = mp.get_next_move()) != MOVE_NONE)
1419 assert(move_is_ok(move));
1421 moveIsCheck = pos.move_is_check(move, ci);
1429 && !move_is_promotion(move)
1430 && !pos.move_is_passed_pawn_push(move))
1432 futilityValue = futilityBase
1433 + pos.endgame_value_of_piece_on(move_to(move))
1434 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1436 if (futilityValue < alpha)
1438 if (futilityValue > bestValue)
1439 bestValue = futilityValue;
1444 // Detect non-capture evasions that are candidate to be pruned
1445 evasionPrunable = isCheck
1446 && bestValue > value_mated_in(PLY_MAX)
1447 && !pos.move_is_capture(move)
1448 && !pos.can_castle(pos.side_to_move());
1450 // Don't search moves with negative SEE values
1452 && (!isCheck || evasionPrunable)
1454 && !move_is_promotion(move)
1455 && pos.see_sign(move) < 0)
1458 // Don't search useless checks
1463 && !pos.move_is_capture_or_promotion(move)
1464 && ss->eval + PawnValueMidgame / 4 < beta
1465 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1467 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1468 bestValue = ss->eval + PawnValueMidgame / 4;
1473 // Update current move
1474 ss->currentMove = move;
1476 // Make and search the move
1477 pos.do_move(move, st, ci, moveIsCheck);
1478 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1479 pos.undo_move(move);
1481 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1484 if (value > bestValue)
1490 ss->bestMove = move;
1495 // All legal moves have been searched. A special case: If we're in check
1496 // and no legal moves were found, it is checkmate.
1497 if (isCheck && bestValue == -VALUE_INFINITE)
1498 return value_mated_in(ply);
1500 // Update transposition table
1501 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1502 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1504 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1510 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1511 // it is used in RootMoveList to get an initial scoring.
1512 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1514 SearchStack ss[PLY_MAX_PLUS_2];
1517 memset(ss, 0, 4 * sizeof(SearchStack));
1518 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1520 for (MoveStack* cur = mlist; cur != last; cur++)
1522 ss[0].currentMove = cur->move;
1523 pos.do_move(cur->move, st);
1524 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1525 pos.undo_move(cur->move);
1530 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1531 // bestValue is updated only when returning false because in that case move
1534 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1536 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1537 Square from, to, ksq, victimSq;
1540 Value futilityValue, bv = *bestValue;
1542 from = move_from(move);
1544 them = opposite_color(pos.side_to_move());
1545 ksq = pos.king_square(them);
1546 kingAtt = pos.attacks_from<KING>(ksq);
1547 pc = pos.piece_on(from);
1549 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1550 oldAtt = pos.attacks_from(pc, from, occ);
1551 newAtt = pos.attacks_from(pc, to, occ);
1553 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1554 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1556 if (!(b && (b & (b - 1))))
1559 // Rule 2. Queen contact check is very dangerous
1560 if ( type_of_piece(pc) == QUEEN
1561 && bit_is_set(kingAtt, to))
1564 // Rule 3. Creating new double threats with checks
1565 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1569 victimSq = pop_1st_bit(&b);
1570 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1572 // Note that here we generate illegal "double move"!
1573 if ( futilityValue >= beta
1574 && pos.see_sign(make_move(from, victimSq)) >= 0)
1577 if (futilityValue > bv)
1581 // Update bestValue only if check is not dangerous (because we will prune the move)
1587 // connected_moves() tests whether two moves are 'connected' in the sense
1588 // that the first move somehow made the second move possible (for instance
1589 // if the moving piece is the same in both moves). The first move is assumed
1590 // to be the move that was made to reach the current position, while the
1591 // second move is assumed to be a move from the current position.
1593 bool connected_moves(const Position& pos, Move m1, Move m2) {
1595 Square f1, t1, f2, t2;
1598 assert(m1 && move_is_ok(m1));
1599 assert(m2 && move_is_ok(m2));
1601 // Case 1: The moving piece is the same in both moves
1607 // Case 2: The destination square for m2 was vacated by m1
1613 // Case 3: Moving through the vacated square
1614 if ( piece_is_slider(pos.piece_on(f2))
1615 && bit_is_set(squares_between(f2, t2), f1))
1618 // Case 4: The destination square for m2 is defended by the moving piece in m1
1619 p = pos.piece_on(t1);
1620 if (bit_is_set(pos.attacks_from(p, t1), t2))
1623 // Case 5: Discovered check, checking piece is the piece moved in m1
1624 if ( piece_is_slider(p)
1625 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1626 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1628 // discovered_check_candidates() works also if the Position's side to
1629 // move is the opposite of the checking piece.
1630 Color them = opposite_color(pos.side_to_move());
1631 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1633 if (bit_is_set(dcCandidates, f2))
1640 // value_is_mate() checks if the given value is a mate one eventually
1641 // compensated for the ply.
1643 bool value_is_mate(Value value) {
1645 assert(abs(value) <= VALUE_INFINITE);
1647 return value <= value_mated_in(PLY_MAX)
1648 || value >= value_mate_in(PLY_MAX);
1652 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1653 // "plies to mate from the current ply". Non-mate scores are unchanged.
1654 // The function is called before storing a value to the transposition table.
1656 Value value_to_tt(Value v, int ply) {
1658 if (v >= value_mate_in(PLY_MAX))
1661 if (v <= value_mated_in(PLY_MAX))
1668 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1669 // the transposition table to a mate score corrected for the current ply.
1671 Value value_from_tt(Value v, int ply) {
1673 if (v >= value_mate_in(PLY_MAX))
1676 if (v <= value_mated_in(PLY_MAX))
1683 // extension() decides whether a move should be searched with normal depth,
1684 // or with extended depth. Certain classes of moves (checking moves, in
1685 // particular) are searched with bigger depth than ordinary moves and in
1686 // any case are marked as 'dangerous'. Note that also if a move is not
1687 // extended, as example because the corresponding UCI option is set to zero,
1688 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1689 template <NodeType PvNode>
1690 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1691 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1693 assert(m != MOVE_NONE);
1695 Depth result = DEPTH_ZERO;
1696 *dangerous = moveIsCheck | mateThreat;
1700 if (moveIsCheck && pos.see_sign(m) >= 0)
1701 result += CheckExtension[PvNode];
1704 result += MateThreatExtension[PvNode];
1707 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1709 Color c = pos.side_to_move();
1710 if (relative_rank(c, move_to(m)) == RANK_7)
1712 result += PawnPushTo7thExtension[PvNode];
1715 if (pos.pawn_is_passed(c, move_to(m)))
1717 result += PassedPawnExtension[PvNode];
1722 if ( captureOrPromotion
1723 && pos.type_of_piece_on(move_to(m)) != PAWN
1724 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1725 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1726 && !move_is_promotion(m)
1729 result += PawnEndgameExtension[PvNode];
1734 && captureOrPromotion
1735 && pos.type_of_piece_on(move_to(m)) != PAWN
1736 && pos.see_sign(m) >= 0)
1738 result += ONE_PLY / 2;
1742 return Min(result, ONE_PLY);
1746 // connected_threat() tests whether it is safe to forward prune a move or if
1747 // is somehow connected to the threat move returned by null search.
1749 bool connected_threat(const Position& pos, Move m, Move threat) {
1751 assert(move_is_ok(m));
1752 assert(threat && move_is_ok(threat));
1753 assert(!pos.move_is_check(m));
1754 assert(!pos.move_is_capture_or_promotion(m));
1755 assert(!pos.move_is_passed_pawn_push(m));
1757 Square mfrom, mto, tfrom, tto;
1759 mfrom = move_from(m);
1761 tfrom = move_from(threat);
1762 tto = move_to(threat);
1764 // Case 1: Don't prune moves which move the threatened piece
1768 // Case 2: If the threatened piece has value less than or equal to the
1769 // value of the threatening piece, don't prune moves which defend it.
1770 if ( pos.move_is_capture(threat)
1771 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1772 || pos.type_of_piece_on(tfrom) == KING)
1773 && pos.move_attacks_square(m, tto))
1776 // Case 3: If the moving piece in the threatened move is a slider, don't
1777 // prune safe moves which block its ray.
1778 if ( piece_is_slider(pos.piece_on(tfrom))
1779 && bit_is_set(squares_between(tfrom, tto), mto)
1780 && pos.see_sign(m) >= 0)
1787 // ok_to_use_TT() returns true if a transposition table score
1788 // can be used at a given point in search.
1790 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1792 Value v = value_from_tt(tte->value(), ply);
1794 return ( tte->depth() >= depth
1795 || v >= Max(value_mate_in(PLY_MAX), beta)
1796 || v < Min(value_mated_in(PLY_MAX), beta))
1798 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1799 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1803 // refine_eval() returns the transposition table score if
1804 // possible otherwise falls back on static position evaluation.
1806 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1810 Value v = value_from_tt(tte->value(), ply);
1812 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1813 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1820 // update_history() registers a good move that produced a beta-cutoff
1821 // in history and marks as failures all the other moves of that ply.
1823 void update_history(const Position& pos, Move move, Depth depth,
1824 Move movesSearched[], int moveCount) {
1826 Value bonus = Value(int(depth) * int(depth));
1828 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1830 for (int i = 0; i < moveCount - 1; i++)
1832 m = movesSearched[i];
1836 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1841 // update_killers() add a good move that produced a beta-cutoff
1842 // among the killer moves of that ply.
1844 void update_killers(Move m, Move killers[]) {
1846 if (m != killers[0])
1848 killers[1] = killers[0];
1854 // update_gains() updates the gains table of a non-capture move given
1855 // the static position evaluation before and after the move.
1857 void update_gains(const Position& pos, Move m, Value before, Value after) {
1860 && before != VALUE_NONE
1861 && after != VALUE_NONE
1862 && pos.captured_piece_type() == PIECE_TYPE_NONE
1863 && !move_is_special(m))
1864 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1868 // value_to_uci() converts a value to a string suitable for use with the UCI
1869 // protocol specifications:
1871 // cp <x> The score from the engine's point of view in centipawns.
1872 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1873 // use negative values for y.
1875 std::string value_to_uci(Value v) {
1877 std::stringstream s;
1879 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1880 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1882 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
1888 // current_search_time() returns the number of milliseconds which have passed
1889 // since the beginning of the current search.
1891 int current_search_time() {
1893 return get_system_time() - SearchStartTime;
1897 // nps() computes the current nodes/second count
1899 int nps(const Position& pos) {
1901 int t = current_search_time();
1902 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1906 // poll() performs two different functions: It polls for user input, and it
1907 // looks at the time consumed so far and decides if it's time to abort the
1910 void poll(const Position& pos) {
1912 static int lastInfoTime;
1913 int t = current_search_time();
1916 if (input_available())
1918 // We are line oriented, don't read single chars
1919 std::string command;
1921 if (!std::getline(std::cin, command))
1924 if (command == "quit")
1926 // Quit the program as soon as possible
1928 QuitRequest = StopRequest = true;
1931 else if (command == "stop")
1933 // Stop calculating as soon as possible, but still send the "bestmove"
1934 // and possibly the "ponder" token when finishing the search.
1938 else if (command == "ponderhit")
1940 // The opponent has played the expected move. GUI sends "ponderhit" if
1941 // we were told to ponder on the same move the opponent has played. We
1942 // should continue searching but switching from pondering to normal search.
1945 if (StopOnPonderhit)
1950 // Print search information
1954 else if (lastInfoTime > t)
1955 // HACK: Must be a new search where we searched less than
1956 // NodesBetweenPolls nodes during the first second of search.
1959 else if (t - lastInfoTime >= 1000)
1966 if (dbg_show_hit_rate)
1967 dbg_print_hit_rate();
1969 // Send info on searched nodes as soon as we return to root
1970 SendSearchedNodes = true;
1973 // Should we stop the search?
1977 bool stillAtFirstMove = FirstRootMove
1978 && !AspirationFailLow
1979 && t > TimeMgr.available_time();
1981 bool noMoreTime = t > TimeMgr.maximum_time()
1982 || stillAtFirstMove;
1984 if ( (UseTimeManagement && noMoreTime)
1985 || (ExactMaxTime && t >= ExactMaxTime)
1986 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1991 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1992 // while the program is pondering. The point is to work around a wrinkle in
1993 // the UCI protocol: When pondering, the engine is not allowed to give a
1994 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1995 // We simply wait here until one of these commands is sent, and return,
1996 // after which the bestmove and pondermove will be printed.
1998 void wait_for_stop_or_ponderhit() {
2000 std::string command;
2004 // Wait for a command from stdin
2005 if (!std::getline(std::cin, command))
2008 if (command == "quit")
2013 else if (command == "ponderhit" || command == "stop")
2019 // init_thread() is the function which is called when a new thread is
2020 // launched. It simply calls the idle_loop() function with the supplied
2021 // threadID. There are two versions of this function; one for POSIX
2022 // threads and one for Windows threads.
2024 #if !defined(_MSC_VER)
2026 void* init_thread(void* threadID) {
2028 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2034 DWORD WINAPI init_thread(LPVOID threadID) {
2036 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2043 /// The ThreadsManager class
2046 // read_uci_options() updates number of active threads and other internal
2047 // parameters according to the UCI options values. It is called before
2048 // to start a new search.
2050 void ThreadsManager::read_uci_options() {
2052 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2053 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2054 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2055 activeThreads = Options["Threads"].value<int>();
2059 // idle_loop() is where the threads are parked when they have no work to do.
2060 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2061 // object for which the current thread is the master.
2063 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2065 assert(threadID >= 0 && threadID < MAX_THREADS);
2068 bool allFinished = false;
2072 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2073 // master should exit as last one.
2074 if (allThreadsShouldExit)
2077 threads[threadID].state = THREAD_TERMINATED;
2081 // If we are not thinking, wait for a condition to be signaled
2082 // instead of wasting CPU time polling for work.
2083 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2084 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2086 assert(!sp || useSleepingThreads);
2087 assert(threadID != 0 || useSleepingThreads);
2089 if (threads[threadID].state == THREAD_INITIALIZING)
2090 threads[threadID].state = THREAD_AVAILABLE;
2092 // Grab the lock to avoid races with wake_sleeping_thread()
2093 lock_grab(&sleepLock[threadID]);
2095 // If we are master and all slaves have finished do not go to sleep
2096 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2097 allFinished = (i == activeThreads);
2099 if (allFinished || allThreadsShouldExit)
2101 lock_release(&sleepLock[threadID]);
2105 // Do sleep here after retesting sleep conditions
2106 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2107 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2109 lock_release(&sleepLock[threadID]);
2112 // If this thread has been assigned work, launch a search
2113 if (threads[threadID].state == THREAD_WORKISWAITING)
2115 assert(!allThreadsShouldExit);
2117 threads[threadID].state = THREAD_SEARCHING;
2119 // Here we call search() with SplitPoint template parameter set to true
2120 SplitPoint* tsp = threads[threadID].splitPoint;
2121 Position pos(*tsp->pos, threadID);
2122 SearchStack* ss = tsp->sstack[threadID] + 1;
2126 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2128 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2130 assert(threads[threadID].state == THREAD_SEARCHING);
2132 threads[threadID].state = THREAD_AVAILABLE;
2134 // Wake up master thread so to allow it to return from the idle loop in
2135 // case we are the last slave of the split point.
2136 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2137 wake_sleeping_thread(tsp->master);
2140 // If this thread is the master of a split point and all slaves have
2141 // finished their work at this split point, return from the idle loop.
2142 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2143 allFinished = (i == activeThreads);
2147 // Because sp->slaves[] is reset under lock protection,
2148 // be sure sp->lock has been released before to return.
2149 lock_grab(&(sp->lock));
2150 lock_release(&(sp->lock));
2152 // In helpful master concept a master can help only a sub-tree, and
2153 // because here is all finished is not possible master is booked.
2154 assert(threads[threadID].state == THREAD_AVAILABLE);
2156 threads[threadID].state = THREAD_SEARCHING;
2163 // init_threads() is called during startup. It launches all helper threads,
2164 // and initializes the split point stack and the global locks and condition
2167 void ThreadsManager::init_threads() {
2169 int i, arg[MAX_THREADS];
2172 // Initialize global locks
2175 for (i = 0; i < MAX_THREADS; i++)
2177 lock_init(&sleepLock[i]);
2178 cond_init(&sleepCond[i]);
2181 // Initialize splitPoints[] locks
2182 for (i = 0; i < MAX_THREADS; i++)
2183 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2184 lock_init(&(threads[i].splitPoints[j].lock));
2186 // Will be set just before program exits to properly end the threads
2187 allThreadsShouldExit = false;
2189 // Threads will be put all threads to sleep as soon as created
2192 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2193 threads[0].state = THREAD_SEARCHING;
2194 for (i = 1; i < MAX_THREADS; i++)
2195 threads[i].state = THREAD_INITIALIZING;
2197 // Launch the helper threads
2198 for (i = 1; i < MAX_THREADS; i++)
2202 #if !defined(_MSC_VER)
2203 pthread_t pthread[1];
2204 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2205 pthread_detach(pthread[0]);
2207 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2211 cout << "Failed to create thread number " << i << endl;
2215 // Wait until the thread has finished launching and is gone to sleep
2216 while (threads[i].state == THREAD_INITIALIZING) {}
2221 // exit_threads() is called when the program exits. It makes all the
2222 // helper threads exit cleanly.
2224 void ThreadsManager::exit_threads() {
2226 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2228 // Wake up all the threads and waits for termination
2229 for (int i = 1; i < MAX_THREADS; i++)
2231 wake_sleeping_thread(i);
2232 while (threads[i].state != THREAD_TERMINATED) {}
2235 // Now we can safely destroy the locks
2236 for (int i = 0; i < MAX_THREADS; i++)
2237 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2238 lock_destroy(&(threads[i].splitPoints[j].lock));
2240 lock_destroy(&mpLock);
2242 // Now we can safely destroy the wait conditions
2243 for (int i = 0; i < MAX_THREADS; i++)
2245 lock_destroy(&sleepLock[i]);
2246 cond_destroy(&sleepCond[i]);
2251 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2252 // the thread's currently active split point, or in some ancestor of
2253 // the current split point.
2255 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2257 assert(threadID >= 0 && threadID < activeThreads);
2259 SplitPoint* sp = threads[threadID].splitPoint;
2261 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2266 // thread_is_available() checks whether the thread with threadID "slave" is
2267 // available to help the thread with threadID "master" at a split point. An
2268 // obvious requirement is that "slave" must be idle. With more than two
2269 // threads, this is not by itself sufficient: If "slave" is the master of
2270 // some active split point, it is only available as a slave to the other
2271 // threads which are busy searching the split point at the top of "slave"'s
2272 // split point stack (the "helpful master concept" in YBWC terminology).
2274 bool ThreadsManager::thread_is_available(int slave, int master) const {
2276 assert(slave >= 0 && slave < activeThreads);
2277 assert(master >= 0 && master < activeThreads);
2278 assert(activeThreads > 1);
2280 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2283 // Make a local copy to be sure doesn't change under our feet
2284 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2286 // No active split points means that the thread is available as
2287 // a slave for any other thread.
2288 if (localActiveSplitPoints == 0 || activeThreads == 2)
2291 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2292 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2293 // could have been set to 0 by another thread leading to an out of bound access.
2294 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2301 // available_thread_exists() tries to find an idle thread which is available as
2302 // a slave for the thread with threadID "master".
2304 bool ThreadsManager::available_thread_exists(int master) const {
2306 assert(master >= 0 && master < activeThreads);
2307 assert(activeThreads > 1);
2309 for (int i = 0; i < activeThreads; i++)
2310 if (thread_is_available(i, master))
2317 // split() does the actual work of distributing the work at a node between
2318 // several available threads. If it does not succeed in splitting the
2319 // node (because no idle threads are available, or because we have no unused
2320 // split point objects), the function immediately returns. If splitting is
2321 // possible, a SplitPoint object is initialized with all the data that must be
2322 // copied to the helper threads and we tell our helper threads that they have
2323 // been assigned work. This will cause them to instantly leave their idle loops and
2324 // call search().When all threads have returned from search() then split() returns.
2326 template <bool Fake>
2327 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2328 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2329 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2330 assert(pos.is_ok());
2331 assert(ply > 0 && ply < PLY_MAX);
2332 assert(*bestValue >= -VALUE_INFINITE);
2333 assert(*bestValue <= *alpha);
2334 assert(*alpha < beta);
2335 assert(beta <= VALUE_INFINITE);
2336 assert(depth > DEPTH_ZERO);
2337 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2338 assert(activeThreads > 1);
2340 int i, master = pos.thread();
2341 Thread& masterThread = threads[master];
2345 // If no other thread is available to help us, or if we have too many
2346 // active split points, don't split.
2347 if ( !available_thread_exists(master)
2348 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2350 lock_release(&mpLock);
2354 // Pick the next available split point object from the split point stack
2355 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2357 // Initialize the split point object
2358 splitPoint.parent = masterThread.splitPoint;
2359 splitPoint.master = master;
2360 splitPoint.betaCutoff = false;
2361 splitPoint.ply = ply;
2362 splitPoint.depth = depth;
2363 splitPoint.threatMove = threatMove;
2364 splitPoint.mateThreat = mateThreat;
2365 splitPoint.alpha = *alpha;
2366 splitPoint.beta = beta;
2367 splitPoint.pvNode = pvNode;
2368 splitPoint.bestValue = *bestValue;
2370 splitPoint.moveCount = moveCount;
2371 splitPoint.pos = &pos;
2372 splitPoint.nodes = 0;
2373 splitPoint.parentSstack = ss;
2374 for (i = 0; i < activeThreads; i++)
2375 splitPoint.slaves[i] = 0;
2377 masterThread.splitPoint = &splitPoint;
2379 // If we are here it means we are not available
2380 assert(masterThread.state != THREAD_AVAILABLE);
2382 int workersCnt = 1; // At least the master is included
2384 // Allocate available threads setting state to THREAD_BOOKED
2385 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2386 if (thread_is_available(i, master))
2388 threads[i].state = THREAD_BOOKED;
2389 threads[i].splitPoint = &splitPoint;
2390 splitPoint.slaves[i] = 1;
2394 assert(Fake || workersCnt > 1);
2396 // We can release the lock because slave threads are already booked and master is not available
2397 lock_release(&mpLock);
2399 // Tell the threads that they have work to do. This will make them leave
2400 // their idle loop. But before copy search stack tail for each thread.
2401 for (i = 0; i < activeThreads; i++)
2402 if (i == master || splitPoint.slaves[i])
2404 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2406 assert(i == master || threads[i].state == THREAD_BOOKED);
2408 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2410 if (useSleepingThreads && i != master)
2411 wake_sleeping_thread(i);
2414 // Everything is set up. The master thread enters the idle loop, from
2415 // which it will instantly launch a search, because its state is
2416 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2417 // idle loop, which means that the main thread will return from the idle
2418 // loop when all threads have finished their work at this split point.
2419 idle_loop(master, &splitPoint);
2421 // We have returned from the idle loop, which means that all threads are
2422 // finished. Update alpha and bestValue, and return.
2425 *alpha = splitPoint.alpha;
2426 *bestValue = splitPoint.bestValue;
2427 masterThread.activeSplitPoints--;
2428 masterThread.splitPoint = splitPoint.parent;
2429 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2431 lock_release(&mpLock);
2435 // wake_sleeping_thread() wakes up the thread with the given threadID
2436 // when it is time to start a new search.
2438 void ThreadsManager::wake_sleeping_thread(int threadID) {
2440 lock_grab(&sleepLock[threadID]);
2441 cond_signal(&sleepCond[threadID]);
2442 lock_release(&sleepLock[threadID]);
2446 /// RootMove and RootMoveList method's definitions
2448 RootMove::RootMove() {
2451 pv_score = non_pv_score = -VALUE_INFINITE;
2455 RootMove& RootMove::operator=(const RootMove& rm) {
2457 const Move* src = rm.pv;
2460 // Avoid a costly full rm.pv[] copy
2461 do *dst++ = *src; while (*src++ != MOVE_NONE);
2464 pv_score = rm.pv_score;
2465 non_pv_score = rm.non_pv_score;
2469 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2470 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2471 // allow to always have a ponder move even when we fail high at root and also a
2472 // long PV to print that is important for position analysis.
2474 void RootMove::extract_pv_from_tt(Position& pos) {
2476 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2480 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2482 pos.do_move(pv[0], *st++);
2484 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2485 && tte->move() != MOVE_NONE
2486 && move_is_legal(pos, tte->move())
2488 && (!pos.is_draw() || ply < 2))
2490 pv[ply] = tte->move();
2491 pos.do_move(pv[ply++], *st++);
2493 pv[ply] = MOVE_NONE;
2495 do pos.undo_move(pv[--ply]); while (ply);
2498 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2499 // the PV back into the TT. This makes sure the old PV moves are searched
2500 // first, even if the old TT entries have been overwritten.
2502 void RootMove::insert_pv_in_tt(Position& pos) {
2504 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2507 Value v, m = VALUE_NONE;
2510 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2514 tte = TT.retrieve(k);
2516 // Don't overwrite existing correct entries
2517 if (!tte || tte->move() != pv[ply])
2519 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2520 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2522 pos.do_move(pv[ply], *st++);
2524 } while (pv[++ply] != MOVE_NONE);
2526 do pos.undo_move(pv[--ply]); while (ply);
2529 // pv_info_to_uci() returns a string with information on the current PV line
2530 // formatted according to UCI specification. It is called at each iteration
2531 // or after a new pv is found.
2533 std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
2535 std::stringstream s, l;
2538 while (*m != MOVE_NONE)
2541 s << "info depth " << depth
2542 << " seldepth " << int(m - pv)
2543 << " multipv " << pvLine + 1
2544 << " score " << value_to_uci(pv_score)
2545 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2546 << " time " << current_search_time()
2547 << " nodes " << pos.nodes_searched()
2548 << " nps " << nps(pos)
2549 << " pv " << l.str();
2555 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2557 MoveStack mlist[MOVES_MAX];
2561 bestMoveChanges = 0;
2563 // Generate all legal moves and score them
2564 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2565 qsearch_scoring(pos, mlist, last);
2567 // Add each move to the RootMoveList's vector
2568 for (MoveStack* cur = mlist; cur != last; cur++)
2570 // If we have a searchMoves[] list then verify cur->move
2571 // is in the list before to add it.
2572 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2574 if (searchMoves[0] && *sm != cur->move)
2578 rm.pv[0] = cur->move;
2579 rm.pv[1] = MOVE_NONE;
2580 rm.pv_score = Value(cur->score);