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 = reduction<PvNode>(depth, moveCount);
1159 alpha = SpNode ? sp->alpha : alpha;
1160 Depth d = newDepth - ss->reduction;
1161 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1163 doFullDepthSearch = (value > alpha);
1165 ss->reduction = DEPTH_ZERO; // Restore original reduction
1168 // Step 15. Full depth search
1169 if (doFullDepthSearch)
1171 alpha = SpNode ? sp->alpha : alpha;
1172 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1174 // Step extra. pv search (only in PV nodes)
1175 // Search only for possible new PV nodes, if instead value >= beta then
1176 // parent node fails low with value <= alpha and tries another move.
1177 if (PvNode && value > alpha && (Root || value < beta))
1178 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1182 // Step 16. Undo move
1183 pos.undo_move(move);
1185 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1187 // Step 17. Check for new best move
1190 lock_grab(&(sp->lock));
1191 bestValue = sp->bestValue;
1195 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1200 sp->bestValue = value;
1204 if (PvNode && value < beta) // We want always alpha < beta
1212 sp->betaCutoff = true;
1214 if (value == value_mate_in(ply + 1))
1215 ss->mateKiller = move;
1217 ss->bestMove = move;
1220 sp->parentSstack->bestMove = move;
1226 // To avoid to exit with bestValue == -VALUE_INFINITE
1227 if (value > bestValue)
1230 // Finished searching the move. If StopRequest is true, the search
1231 // was aborted because the user interrupted the search or because we
1232 // ran out of time. In this case, the return value of the search cannot
1233 // be trusted, and we break out of the loop without updating the best
1238 // Remember searched nodes counts for this move
1239 mp.rm->nodes += pos.nodes_searched() - nodes;
1241 // Step 17. Check for new best move
1242 if (!isPvMove && value <= alpha)
1243 mp.rm->pv_score = -VALUE_INFINITE;
1246 // PV move or new best move!
1249 ss->bestMove = move;
1250 mp.rm->pv_score = value;
1251 mp.rm->extract_pv_from_tt(pos);
1253 // We record how often the best move has been changed in each
1254 // iteration. This information is used for time management: When
1255 // the best move changes frequently, we allocate some more time.
1256 if (!isPvMove && MultiPV == 1)
1257 Rml.bestMoveChanges++;
1259 Rml.sort_multipv(moveCount);
1261 // Update alpha. In multi-pv we don't use aspiration window, so
1262 // set alpha equal to minimum score among the PV lines.
1264 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1265 else if (value > alpha)
1268 } // PV move or new best move
1271 // Step 18. Check for split
1274 && depth >= ThreadsMgr.min_split_depth()
1275 && ThreadsMgr.active_threads() > 1
1277 && ThreadsMgr.available_thread_exists(threadID)
1279 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1280 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1281 threatMove, mateThreat, moveCount, &mp, PvNode);
1284 // Step 19. Check for mate and stalemate
1285 // All legal moves have been searched and if there are
1286 // no legal moves, it must be mate or stalemate.
1287 // If one move was excluded return fail low score.
1288 if (!SpNode && !moveCount)
1289 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1291 // Step 20. Update tables
1292 // If the search is not aborted, update the transposition table,
1293 // history counters, and killer moves.
1294 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1296 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1297 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1298 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1300 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1302 // Update killers and history only for non capture moves that fails high
1303 if ( bestValue >= beta
1304 && !pos.move_is_capture_or_promotion(move))
1306 update_history(pos, move, depth, movesSearched, playedMoveCount);
1307 update_killers(move, ss->killers);
1313 // Here we have the lock still grabbed
1314 sp->slaves[threadID] = 0;
1315 sp->nodes += pos.nodes_searched();
1316 lock_release(&(sp->lock));
1319 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1324 // qsearch() is the quiescence search function, which is called by the main
1325 // search function when the remaining depth is zero (or, to be more precise,
1326 // less than ONE_PLY).
1328 template <NodeType PvNode>
1329 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1331 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1332 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1333 assert(PvNode || alpha == beta - 1);
1335 assert(ply > 0 && ply < PLY_MAX);
1336 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1340 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1341 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1344 Value oldAlpha = alpha;
1346 ss->bestMove = ss->currentMove = MOVE_NONE;
1348 // Check for an instant draw or maximum ply reached
1349 if (pos.is_draw() || ply >= PLY_MAX - 1)
1352 // Decide whether or not to include checks, this fixes also the type of
1353 // TT entry depth that we are going to use. Note that in qsearch we use
1354 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1355 isCheck = pos.is_check();
1356 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1358 // Transposition table lookup. At PV nodes, we don't use the TT for
1359 // pruning, but only for move ordering.
1360 tte = TT.retrieve(pos.get_key());
1361 ttMove = (tte ? tte->move() : MOVE_NONE);
1363 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1365 ss->bestMove = ttMove; // Can be MOVE_NONE
1366 return value_from_tt(tte->value(), ply);
1369 // Evaluate the position statically
1372 bestValue = futilityBase = -VALUE_INFINITE;
1373 ss->eval = evalMargin = VALUE_NONE;
1374 enoughMaterial = false;
1380 assert(tte->static_value() != VALUE_NONE);
1382 evalMargin = tte->static_value_margin();
1383 ss->eval = bestValue = tte->static_value();
1386 ss->eval = bestValue = evaluate(pos, evalMargin);
1388 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1390 // Stand pat. Return immediately if static value is at least beta
1391 if (bestValue >= beta)
1394 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1399 if (PvNode && bestValue > alpha)
1402 // Futility pruning parameters, not needed when in check
1403 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1404 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1407 // Initialize a MovePicker object for the current position, and prepare
1408 // to search the moves. Because the depth is <= 0 here, only captures,
1409 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1411 MovePicker mp(pos, ttMove, depth, H);
1414 // Loop through the moves until no moves remain or a beta cutoff occurs
1415 while ( alpha < beta
1416 && (move = mp.get_next_move()) != MOVE_NONE)
1418 assert(move_is_ok(move));
1420 moveIsCheck = pos.move_is_check(move, ci);
1428 && !move_is_promotion(move)
1429 && !pos.move_is_passed_pawn_push(move))
1431 futilityValue = futilityBase
1432 + pos.endgame_value_of_piece_on(move_to(move))
1433 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1435 if (futilityValue < alpha)
1437 if (futilityValue > bestValue)
1438 bestValue = futilityValue;
1443 // Detect non-capture evasions that are candidate to be pruned
1444 evasionPrunable = isCheck
1445 && bestValue > value_mated_in(PLY_MAX)
1446 && !pos.move_is_capture(move)
1447 && !pos.can_castle(pos.side_to_move());
1449 // Don't search moves with negative SEE values
1451 && (!isCheck || evasionPrunable)
1453 && !move_is_promotion(move)
1454 && pos.see_sign(move) < 0)
1457 // Don't search useless checks
1462 && !pos.move_is_capture_or_promotion(move)
1463 && ss->eval + PawnValueMidgame / 4 < beta
1464 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1466 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1467 bestValue = ss->eval + PawnValueMidgame / 4;
1472 // Update current move
1473 ss->currentMove = move;
1475 // Make and search the move
1476 pos.do_move(move, st, ci, moveIsCheck);
1477 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1478 pos.undo_move(move);
1480 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1483 if (value > bestValue)
1489 ss->bestMove = move;
1494 // All legal moves have been searched. A special case: If we're in check
1495 // and no legal moves were found, it is checkmate.
1496 if (isCheck && bestValue == -VALUE_INFINITE)
1497 return value_mated_in(ply);
1499 // Update transposition table
1500 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1501 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1503 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1509 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1510 // it is used in RootMoveList to get an initial scoring.
1511 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1513 SearchStack ss[PLY_MAX_PLUS_2];
1516 memset(ss, 0, 4 * sizeof(SearchStack));
1517 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1519 for (MoveStack* cur = mlist; cur != last; cur++)
1521 ss[0].currentMove = cur->move;
1522 pos.do_move(cur->move, st);
1523 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1524 pos.undo_move(cur->move);
1529 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1530 // bestValue is updated only when returning false because in that case move
1533 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1535 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1536 Square from, to, ksq, victimSq;
1539 Value futilityValue, bv = *bestValue;
1541 from = move_from(move);
1543 them = opposite_color(pos.side_to_move());
1544 ksq = pos.king_square(them);
1545 kingAtt = pos.attacks_from<KING>(ksq);
1546 pc = pos.piece_on(from);
1548 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1549 oldAtt = pos.attacks_from(pc, from, occ);
1550 newAtt = pos.attacks_from(pc, to, occ);
1552 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1553 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1555 if (!(b && (b & (b - 1))))
1558 // Rule 2. Queen contact check is very dangerous
1559 if ( type_of_piece(pc) == QUEEN
1560 && bit_is_set(kingAtt, to))
1563 // Rule 3. Creating new double threats with checks
1564 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1568 victimSq = pop_1st_bit(&b);
1569 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1571 // Note that here we generate illegal "double move"!
1572 if ( futilityValue >= beta
1573 && pos.see_sign(make_move(from, victimSq)) >= 0)
1576 if (futilityValue > bv)
1580 // Update bestValue only if check is not dangerous (because we will prune the move)
1586 // connected_moves() tests whether two moves are 'connected' in the sense
1587 // that the first move somehow made the second move possible (for instance
1588 // if the moving piece is the same in both moves). The first move is assumed
1589 // to be the move that was made to reach the current position, while the
1590 // second move is assumed to be a move from the current position.
1592 bool connected_moves(const Position& pos, Move m1, Move m2) {
1594 Square f1, t1, f2, t2;
1597 assert(m1 && move_is_ok(m1));
1598 assert(m2 && move_is_ok(m2));
1600 // Case 1: The moving piece is the same in both moves
1606 // Case 2: The destination square for m2 was vacated by m1
1612 // Case 3: Moving through the vacated square
1613 if ( piece_is_slider(pos.piece_on(f2))
1614 && bit_is_set(squares_between(f2, t2), f1))
1617 // Case 4: The destination square for m2 is defended by the moving piece in m1
1618 p = pos.piece_on(t1);
1619 if (bit_is_set(pos.attacks_from(p, t1), t2))
1622 // Case 5: Discovered check, checking piece is the piece moved in m1
1623 if ( piece_is_slider(p)
1624 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1625 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1627 // discovered_check_candidates() works also if the Position's side to
1628 // move is the opposite of the checking piece.
1629 Color them = opposite_color(pos.side_to_move());
1630 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1632 if (bit_is_set(dcCandidates, f2))
1639 // value_is_mate() checks if the given value is a mate one eventually
1640 // compensated for the ply.
1642 bool value_is_mate(Value value) {
1644 assert(abs(value) <= VALUE_INFINITE);
1646 return value <= value_mated_in(PLY_MAX)
1647 || value >= value_mate_in(PLY_MAX);
1651 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1652 // "plies to mate from the current ply". Non-mate scores are unchanged.
1653 // The function is called before storing a value to the transposition table.
1655 Value value_to_tt(Value v, int ply) {
1657 if (v >= value_mate_in(PLY_MAX))
1660 if (v <= value_mated_in(PLY_MAX))
1667 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1668 // the transposition table to a mate score corrected for the current ply.
1670 Value value_from_tt(Value v, int ply) {
1672 if (v >= value_mate_in(PLY_MAX))
1675 if (v <= value_mated_in(PLY_MAX))
1682 // extension() decides whether a move should be searched with normal depth,
1683 // or with extended depth. Certain classes of moves (checking moves, in
1684 // particular) are searched with bigger depth than ordinary moves and in
1685 // any case are marked as 'dangerous'. Note that also if a move is not
1686 // extended, as example because the corresponding UCI option is set to zero,
1687 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1688 template <NodeType PvNode>
1689 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1690 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1692 assert(m != MOVE_NONE);
1694 Depth result = DEPTH_ZERO;
1695 *dangerous = moveIsCheck | mateThreat;
1699 if (moveIsCheck && pos.see_sign(m) >= 0)
1700 result += CheckExtension[PvNode];
1703 result += MateThreatExtension[PvNode];
1706 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1708 Color c = pos.side_to_move();
1709 if (relative_rank(c, move_to(m)) == RANK_7)
1711 result += PawnPushTo7thExtension[PvNode];
1714 if (pos.pawn_is_passed(c, move_to(m)))
1716 result += PassedPawnExtension[PvNode];
1721 if ( captureOrPromotion
1722 && pos.type_of_piece_on(move_to(m)) != PAWN
1723 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1724 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1725 && !move_is_promotion(m)
1728 result += PawnEndgameExtension[PvNode];
1733 && captureOrPromotion
1734 && pos.type_of_piece_on(move_to(m)) != PAWN
1735 && pos.see_sign(m) >= 0)
1737 result += ONE_PLY / 2;
1741 return Min(result, ONE_PLY);
1745 // connected_threat() tests whether it is safe to forward prune a move or if
1746 // is somehow connected to the threat move returned by null search.
1748 bool connected_threat(const Position& pos, Move m, Move threat) {
1750 assert(move_is_ok(m));
1751 assert(threat && move_is_ok(threat));
1752 assert(!pos.move_is_check(m));
1753 assert(!pos.move_is_capture_or_promotion(m));
1754 assert(!pos.move_is_passed_pawn_push(m));
1756 Square mfrom, mto, tfrom, tto;
1758 mfrom = move_from(m);
1760 tfrom = move_from(threat);
1761 tto = move_to(threat);
1763 // Case 1: Don't prune moves which move the threatened piece
1767 // Case 2: If the threatened piece has value less than or equal to the
1768 // value of the threatening piece, don't prune moves which defend it.
1769 if ( pos.move_is_capture(threat)
1770 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1771 || pos.type_of_piece_on(tfrom) == KING)
1772 && pos.move_attacks_square(m, tto))
1775 // Case 3: If the moving piece in the threatened move is a slider, don't
1776 // prune safe moves which block its ray.
1777 if ( piece_is_slider(pos.piece_on(tfrom))
1778 && bit_is_set(squares_between(tfrom, tto), mto)
1779 && pos.see_sign(m) >= 0)
1786 // ok_to_use_TT() returns true if a transposition table score
1787 // can be used at a given point in search.
1789 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1791 Value v = value_from_tt(tte->value(), ply);
1793 return ( tte->depth() >= depth
1794 || v >= Max(value_mate_in(PLY_MAX), beta)
1795 || v < Min(value_mated_in(PLY_MAX), beta))
1797 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1798 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1802 // refine_eval() returns the transposition table score if
1803 // possible otherwise falls back on static position evaluation.
1805 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1809 Value v = value_from_tt(tte->value(), ply);
1811 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1812 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1819 // update_history() registers a good move that produced a beta-cutoff
1820 // in history and marks as failures all the other moves of that ply.
1822 void update_history(const Position& pos, Move move, Depth depth,
1823 Move movesSearched[], int moveCount) {
1825 Value bonus = Value(int(depth) * int(depth));
1827 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1829 for (int i = 0; i < moveCount - 1; i++)
1831 m = movesSearched[i];
1835 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1840 // update_killers() add a good move that produced a beta-cutoff
1841 // among the killer moves of that ply.
1843 void update_killers(Move m, Move killers[]) {
1845 if (m != killers[0])
1847 killers[1] = killers[0];
1853 // update_gains() updates the gains table of a non-capture move given
1854 // the static position evaluation before and after the move.
1856 void update_gains(const Position& pos, Move m, Value before, Value after) {
1859 && before != VALUE_NONE
1860 && after != VALUE_NONE
1861 && pos.captured_piece_type() == PIECE_TYPE_NONE
1862 && !move_is_special(m))
1863 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1867 // value_to_uci() converts a value to a string suitable for use with the UCI
1868 // protocol specifications:
1870 // cp <x> The score from the engine's point of view in centipawns.
1871 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1872 // use negative values for y.
1874 std::string value_to_uci(Value v) {
1876 std::stringstream s;
1878 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1879 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1881 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
1887 // current_search_time() returns the number of milliseconds which have passed
1888 // since the beginning of the current search.
1890 int current_search_time() {
1892 return get_system_time() - SearchStartTime;
1896 // nps() computes the current nodes/second count
1898 int nps(const Position& pos) {
1900 int t = current_search_time();
1901 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1905 // poll() performs two different functions: It polls for user input, and it
1906 // looks at the time consumed so far and decides if it's time to abort the
1909 void poll(const Position& pos) {
1911 static int lastInfoTime;
1912 int t = current_search_time();
1915 if (input_available())
1917 // We are line oriented, don't read single chars
1918 std::string command;
1920 if (!std::getline(std::cin, command))
1923 if (command == "quit")
1925 // Quit the program as soon as possible
1927 QuitRequest = StopRequest = true;
1930 else if (command == "stop")
1932 // Stop calculating as soon as possible, but still send the "bestmove"
1933 // and possibly the "ponder" token when finishing the search.
1937 else if (command == "ponderhit")
1939 // The opponent has played the expected move. GUI sends "ponderhit" if
1940 // we were told to ponder on the same move the opponent has played. We
1941 // should continue searching but switching from pondering to normal search.
1944 if (StopOnPonderhit)
1949 // Print search information
1953 else if (lastInfoTime > t)
1954 // HACK: Must be a new search where we searched less than
1955 // NodesBetweenPolls nodes during the first second of search.
1958 else if (t - lastInfoTime >= 1000)
1965 if (dbg_show_hit_rate)
1966 dbg_print_hit_rate();
1968 // Send info on searched nodes as soon as we return to root
1969 SendSearchedNodes = true;
1972 // Should we stop the search?
1976 bool stillAtFirstMove = FirstRootMove
1977 && !AspirationFailLow
1978 && t > TimeMgr.available_time();
1980 bool noMoreTime = t > TimeMgr.maximum_time()
1981 || stillAtFirstMove;
1983 if ( (UseTimeManagement && noMoreTime)
1984 || (ExactMaxTime && t >= ExactMaxTime)
1985 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1990 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1991 // while the program is pondering. The point is to work around a wrinkle in
1992 // the UCI protocol: When pondering, the engine is not allowed to give a
1993 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1994 // We simply wait here until one of these commands is sent, and return,
1995 // after which the bestmove and pondermove will be printed.
1997 void wait_for_stop_or_ponderhit() {
1999 std::string command;
2003 // Wait for a command from stdin
2004 if (!std::getline(std::cin, command))
2007 if (command == "quit")
2012 else if (command == "ponderhit" || command == "stop")
2018 // init_thread() is the function which is called when a new thread is
2019 // launched. It simply calls the idle_loop() function with the supplied
2020 // threadID. There are two versions of this function; one for POSIX
2021 // threads and one for Windows threads.
2023 #if !defined(_MSC_VER)
2025 void* init_thread(void* threadID) {
2027 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2033 DWORD WINAPI init_thread(LPVOID threadID) {
2035 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2042 /// The ThreadsManager class
2045 // read_uci_options() updates number of active threads and other internal
2046 // parameters according to the UCI options values. It is called before
2047 // to start a new search.
2049 void ThreadsManager::read_uci_options() {
2051 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2052 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2053 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2054 activeThreads = Options["Threads"].value<int>();
2058 // idle_loop() is where the threads are parked when they have no work to do.
2059 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2060 // object for which the current thread is the master.
2062 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2064 assert(threadID >= 0 && threadID < MAX_THREADS);
2067 bool allFinished = false;
2071 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2072 // master should exit as last one.
2073 if (allThreadsShouldExit)
2076 threads[threadID].state = THREAD_TERMINATED;
2080 // If we are not thinking, wait for a condition to be signaled
2081 // instead of wasting CPU time polling for work.
2082 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2083 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2085 assert(!sp || useSleepingThreads);
2086 assert(threadID != 0 || useSleepingThreads);
2088 if (threads[threadID].state == THREAD_INITIALIZING)
2089 threads[threadID].state = THREAD_AVAILABLE;
2091 // Grab the lock to avoid races with wake_sleeping_thread()
2092 lock_grab(&sleepLock[threadID]);
2094 // If we are master and all slaves have finished do not go to sleep
2095 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2096 allFinished = (i == activeThreads);
2098 if (allFinished || allThreadsShouldExit)
2100 lock_release(&sleepLock[threadID]);
2104 // Do sleep here after retesting sleep conditions
2105 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2106 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2108 lock_release(&sleepLock[threadID]);
2111 // If this thread has been assigned work, launch a search
2112 if (threads[threadID].state == THREAD_WORKISWAITING)
2114 assert(!allThreadsShouldExit);
2116 threads[threadID].state = THREAD_SEARCHING;
2118 // Here we call search() with SplitPoint template parameter set to true
2119 SplitPoint* tsp = threads[threadID].splitPoint;
2120 Position pos(*tsp->pos, threadID);
2121 SearchStack* ss = tsp->sstack[threadID] + 1;
2125 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2127 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2129 assert(threads[threadID].state == THREAD_SEARCHING);
2131 threads[threadID].state = THREAD_AVAILABLE;
2133 // Wake up master thread so to allow it to return from the idle loop in
2134 // case we are the last slave of the split point.
2135 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2136 wake_sleeping_thread(tsp->master);
2139 // If this thread is the master of a split point and all slaves have
2140 // finished their work at this split point, return from the idle loop.
2141 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2142 allFinished = (i == activeThreads);
2146 // Because sp->slaves[] is reset under lock protection,
2147 // be sure sp->lock has been released before to return.
2148 lock_grab(&(sp->lock));
2149 lock_release(&(sp->lock));
2151 // In helpful master concept a master can help only a sub-tree, and
2152 // because here is all finished is not possible master is booked.
2153 assert(threads[threadID].state == THREAD_AVAILABLE);
2155 threads[threadID].state = THREAD_SEARCHING;
2162 // init_threads() is called during startup. It launches all helper threads,
2163 // and initializes the split point stack and the global locks and condition
2166 void ThreadsManager::init_threads() {
2168 int i, arg[MAX_THREADS];
2171 // Initialize global locks
2174 for (i = 0; i < MAX_THREADS; i++)
2176 lock_init(&sleepLock[i]);
2177 cond_init(&sleepCond[i]);
2180 // Initialize splitPoints[] locks
2181 for (i = 0; i < MAX_THREADS; i++)
2182 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2183 lock_init(&(threads[i].splitPoints[j].lock));
2185 // Will be set just before program exits to properly end the threads
2186 allThreadsShouldExit = false;
2188 // Threads will be put all threads to sleep as soon as created
2191 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2192 threads[0].state = THREAD_SEARCHING;
2193 for (i = 1; i < MAX_THREADS; i++)
2194 threads[i].state = THREAD_INITIALIZING;
2196 // Launch the helper threads
2197 for (i = 1; i < MAX_THREADS; i++)
2201 #if !defined(_MSC_VER)
2202 pthread_t pthread[1];
2203 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2204 pthread_detach(pthread[0]);
2206 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2210 cout << "Failed to create thread number " << i << endl;
2214 // Wait until the thread has finished launching and is gone to sleep
2215 while (threads[i].state == THREAD_INITIALIZING) {}
2220 // exit_threads() is called when the program exits. It makes all the
2221 // helper threads exit cleanly.
2223 void ThreadsManager::exit_threads() {
2225 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2227 // Wake up all the threads and waits for termination
2228 for (int i = 1; i < MAX_THREADS; i++)
2230 wake_sleeping_thread(i);
2231 while (threads[i].state != THREAD_TERMINATED) {}
2234 // Now we can safely destroy the locks
2235 for (int i = 0; i < MAX_THREADS; i++)
2236 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2237 lock_destroy(&(threads[i].splitPoints[j].lock));
2239 lock_destroy(&mpLock);
2241 // Now we can safely destroy the wait conditions
2242 for (int i = 0; i < MAX_THREADS; i++)
2244 lock_destroy(&sleepLock[i]);
2245 cond_destroy(&sleepCond[i]);
2250 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2251 // the thread's currently active split point, or in some ancestor of
2252 // the current split point.
2254 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2256 assert(threadID >= 0 && threadID < activeThreads);
2258 SplitPoint* sp = threads[threadID].splitPoint;
2260 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2265 // thread_is_available() checks whether the thread with threadID "slave" is
2266 // available to help the thread with threadID "master" at a split point. An
2267 // obvious requirement is that "slave" must be idle. With more than two
2268 // threads, this is not by itself sufficient: If "slave" is the master of
2269 // some active split point, it is only available as a slave to the other
2270 // threads which are busy searching the split point at the top of "slave"'s
2271 // split point stack (the "helpful master concept" in YBWC terminology).
2273 bool ThreadsManager::thread_is_available(int slave, int master) const {
2275 assert(slave >= 0 && slave < activeThreads);
2276 assert(master >= 0 && master < activeThreads);
2277 assert(activeThreads > 1);
2279 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2282 // Make a local copy to be sure doesn't change under our feet
2283 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2285 // No active split points means that the thread is available as
2286 // a slave for any other thread.
2287 if (localActiveSplitPoints == 0 || activeThreads == 2)
2290 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2291 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2292 // could have been set to 0 by another thread leading to an out of bound access.
2293 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2300 // available_thread_exists() tries to find an idle thread which is available as
2301 // a slave for the thread with threadID "master".
2303 bool ThreadsManager::available_thread_exists(int master) const {
2305 assert(master >= 0 && master < activeThreads);
2306 assert(activeThreads > 1);
2308 for (int i = 0; i < activeThreads; i++)
2309 if (thread_is_available(i, master))
2316 // split() does the actual work of distributing the work at a node between
2317 // several available threads. If it does not succeed in splitting the
2318 // node (because no idle threads are available, or because we have no unused
2319 // split point objects), the function immediately returns. If splitting is
2320 // possible, a SplitPoint object is initialized with all the data that must be
2321 // copied to the helper threads and we tell our helper threads that they have
2322 // been assigned work. This will cause them to instantly leave their idle loops and
2323 // call search().When all threads have returned from search() then split() returns.
2325 template <bool Fake>
2326 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2327 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2328 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2329 assert(pos.is_ok());
2330 assert(ply > 0 && ply < PLY_MAX);
2331 assert(*bestValue >= -VALUE_INFINITE);
2332 assert(*bestValue <= *alpha);
2333 assert(*alpha < beta);
2334 assert(beta <= VALUE_INFINITE);
2335 assert(depth > DEPTH_ZERO);
2336 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2337 assert(activeThreads > 1);
2339 int i, master = pos.thread();
2340 Thread& masterThread = threads[master];
2344 // If no other thread is available to help us, or if we have too many
2345 // active split points, don't split.
2346 if ( !available_thread_exists(master)
2347 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2349 lock_release(&mpLock);
2353 // Pick the next available split point object from the split point stack
2354 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2356 // Initialize the split point object
2357 splitPoint.parent = masterThread.splitPoint;
2358 splitPoint.master = master;
2359 splitPoint.betaCutoff = false;
2360 splitPoint.ply = ply;
2361 splitPoint.depth = depth;
2362 splitPoint.threatMove = threatMove;
2363 splitPoint.mateThreat = mateThreat;
2364 splitPoint.alpha = *alpha;
2365 splitPoint.beta = beta;
2366 splitPoint.pvNode = pvNode;
2367 splitPoint.bestValue = *bestValue;
2369 splitPoint.moveCount = moveCount;
2370 splitPoint.pos = &pos;
2371 splitPoint.nodes = 0;
2372 splitPoint.parentSstack = ss;
2373 for (i = 0; i < activeThreads; i++)
2374 splitPoint.slaves[i] = 0;
2376 masterThread.splitPoint = &splitPoint;
2378 // If we are here it means we are not available
2379 assert(masterThread.state != THREAD_AVAILABLE);
2381 int workersCnt = 1; // At least the master is included
2383 // Allocate available threads setting state to THREAD_BOOKED
2384 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2385 if (thread_is_available(i, master))
2387 threads[i].state = THREAD_BOOKED;
2388 threads[i].splitPoint = &splitPoint;
2389 splitPoint.slaves[i] = 1;
2393 assert(Fake || workersCnt > 1);
2395 // We can release the lock because slave threads are already booked and master is not available
2396 lock_release(&mpLock);
2398 // Tell the threads that they have work to do. This will make them leave
2399 // their idle loop. But before copy search stack tail for each thread.
2400 for (i = 0; i < activeThreads; i++)
2401 if (i == master || splitPoint.slaves[i])
2403 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2405 assert(i == master || threads[i].state == THREAD_BOOKED);
2407 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2409 if (useSleepingThreads && i != master)
2410 wake_sleeping_thread(i);
2413 // Everything is set up. The master thread enters the idle loop, from
2414 // which it will instantly launch a search, because its state is
2415 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2416 // idle loop, which means that the main thread will return from the idle
2417 // loop when all threads have finished their work at this split point.
2418 idle_loop(master, &splitPoint);
2420 // We have returned from the idle loop, which means that all threads are
2421 // finished. Update alpha and bestValue, and return.
2424 *alpha = splitPoint.alpha;
2425 *bestValue = splitPoint.bestValue;
2426 masterThread.activeSplitPoints--;
2427 masterThread.splitPoint = splitPoint.parent;
2428 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2430 lock_release(&mpLock);
2434 // wake_sleeping_thread() wakes up the thread with the given threadID
2435 // when it is time to start a new search.
2437 void ThreadsManager::wake_sleeping_thread(int threadID) {
2439 lock_grab(&sleepLock[threadID]);
2440 cond_signal(&sleepCond[threadID]);
2441 lock_release(&sleepLock[threadID]);
2445 /// RootMove and RootMoveList method's definitions
2447 RootMove::RootMove() {
2450 pv_score = non_pv_score = -VALUE_INFINITE;
2454 RootMove& RootMove::operator=(const RootMove& rm) {
2456 const Move* src = rm.pv;
2459 // Avoid a costly full rm.pv[] copy
2460 do *dst++ = *src; while (*src++ != MOVE_NONE);
2463 pv_score = rm.pv_score;
2464 non_pv_score = rm.non_pv_score;
2468 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2469 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2470 // allow to always have a ponder move even when we fail high at root and also a
2471 // long PV to print that is important for position analysis.
2473 void RootMove::extract_pv_from_tt(Position& pos) {
2475 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2479 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2481 pos.do_move(pv[0], *st++);
2483 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2484 && tte->move() != MOVE_NONE
2485 && move_is_legal(pos, tte->move())
2487 && (!pos.is_draw() || ply < 2))
2489 pv[ply] = tte->move();
2490 pos.do_move(pv[ply++], *st++);
2492 pv[ply] = MOVE_NONE;
2494 do pos.undo_move(pv[--ply]); while (ply);
2497 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2498 // the PV back into the TT. This makes sure the old PV moves are searched
2499 // first, even if the old TT entries have been overwritten.
2501 void RootMove::insert_pv_in_tt(Position& pos) {
2503 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2506 Value v, m = VALUE_NONE;
2509 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2513 tte = TT.retrieve(k);
2515 // Don't overwrite existing correct entries
2516 if (!tte || tte->move() != pv[ply])
2518 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2519 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2521 pos.do_move(pv[ply], *st++);
2523 } while (pv[++ply] != MOVE_NONE);
2525 do pos.undo_move(pv[--ply]); while (ply);
2528 // pv_info_to_uci() returns a string with information on the current PV line
2529 // formatted according to UCI specification. It is called at each iteration
2530 // or after a new pv is found.
2532 std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
2534 std::stringstream s, l;
2537 while (*m != MOVE_NONE)
2540 s << "info depth " << depth
2541 << " seldepth " << int(m - pv)
2542 << " multipv " << pvLine + 1
2543 << " score " << value_to_uci(pv_score)
2544 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2545 << " time " << current_search_time()
2546 << " nodes " << pos.nodes_searched()
2547 << " nps " << nps(pos)
2548 << " pv " << l.str();
2554 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2556 MoveStack mlist[MOVES_MAX];
2560 bestMoveChanges = 0;
2562 // Generate all legal moves and score them
2563 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2564 qsearch_scoring(pos, mlist, last);
2566 // Add each move to the RootMoveList's vector
2567 for (MoveStack* cur = mlist; cur != last; cur++)
2569 // If we have a searchMoves[] list then verify cur->move
2570 // is in the list before to add it.
2571 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2573 if (searchMoves[0] && *sm != cur->move)
2577 rm.pv[0] = cur->move;
2578 rm.pv[1] = MOVE_NONE;
2579 rm.pv_score = Value(cur->score);