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 std::string speed_to_uci(int64_t nodes);
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" << speed_to_uci(pos.nodes_searched()) << endl;
565 int t = current_search_time();
567 LogFile << "Nodes: " << pos.nodes_searched()
568 << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0)
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, 4 * 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 = (ss+1)->excludedMove = MOVE_NONE;
805 (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
806 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
808 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
814 // Step 2. Check for aborted search and immediate draw
816 || ThreadsMgr.cutoff_at_splitpoint(threadID)
818 || ply >= PLY_MAX - 1) && !Root)
821 // Step 3. Mate distance pruning
822 alpha = Max(value_mated_in(ply), alpha);
823 beta = Min(value_mate_in(ply+1), beta);
827 // Step 4. Transposition table lookup
828 // We don't want the score of a partial search to overwrite a previous full search
829 // TT value, so we use a different position key in case of an excluded move.
830 excludedMove = ss->excludedMove;
831 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
833 tte = TT.retrieve(posKey);
834 ttMove = tte ? tte->move() : MOVE_NONE;
836 // At PV nodes we check for exact scores, while at non-PV nodes we check for
837 // and return a fail high/low. Biggest advantage at probing at PV nodes is
838 // to have a smooth experience in analysis mode.
841 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
842 : ok_to_use_TT(tte, depth, beta, ply)))
845 ss->bestMove = ttMove; // Can be MOVE_NONE
846 return value_from_tt(tte->value(), ply);
849 // Step 5. Evaluate the position statically and
850 // update gain statistics of parent move.
852 ss->eval = ss->evalMargin = VALUE_NONE;
855 assert(tte->static_value() != VALUE_NONE);
857 ss->eval = tte->static_value();
858 ss->evalMargin = tte->static_value_margin();
859 refinedValue = refine_eval(tte, ss->eval, ply);
863 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
864 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
867 // Save gain for the parent non-capture move
868 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
870 // Step 6. Razoring (is omitted in PV nodes)
872 && depth < RazorDepth
874 && refinedValue < beta - razor_margin(depth)
875 && ttMove == MOVE_NONE
876 && !value_is_mate(beta)
877 && !pos.has_pawn_on_7th(pos.side_to_move()))
879 Value rbeta = beta - razor_margin(depth);
880 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
882 // Logically we should return (v + razor_margin(depth)), but
883 // surprisingly this did slightly weaker in tests.
887 // Step 7. Static null move pruning (is omitted in PV nodes)
888 // We're betting that the opponent doesn't have a move that will reduce
889 // the score by more than futility_margin(depth) if we do a null move.
892 && depth < RazorDepth
894 && refinedValue >= beta + futility_margin(depth, 0)
895 && !value_is_mate(beta)
896 && pos.non_pawn_material(pos.side_to_move()))
897 return refinedValue - futility_margin(depth, 0);
899 // Step 8. Null move search with verification search (is omitted in PV nodes)
904 && refinedValue >= beta
905 && !value_is_mate(beta)
906 && pos.non_pawn_material(pos.side_to_move()))
908 ss->currentMove = MOVE_NULL;
910 // Null move dynamic reduction based on depth
911 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
913 // Null move dynamic reduction based on value
914 if (refinedValue - beta > PawnValueMidgame)
917 pos.do_null_move(st);
918 (ss+1)->skipNullMove = true;
919 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
920 (ss+1)->skipNullMove = false;
921 pos.undo_null_move();
923 if (nullValue >= beta)
925 // Do not return unproven mate scores
926 if (nullValue >= value_mate_in(PLY_MAX))
929 if (depth < 6 * ONE_PLY)
932 // Do verification search at high depths
933 ss->skipNullMove = true;
934 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
935 ss->skipNullMove = false;
942 // The null move failed low, which means that we may be faced with
943 // some kind of threat. If the previous move was reduced, check if
944 // the move that refuted the null move was somehow connected to the
945 // move which was reduced. If a connection is found, return a fail
946 // low score (which will cause the reduced move to fail high in the
947 // parent node, which will trigger a re-search with full depth).
948 if (nullValue == value_mated_in(ply + 2))
951 threatMove = (ss+1)->bestMove;
952 if ( depth < ThreatDepth
954 && threatMove != MOVE_NONE
955 && connected_moves(pos, (ss-1)->currentMove, threatMove))
960 // Step 9. Internal iterative deepening
961 if ( depth >= IIDDepth[PvNode]
962 && ttMove == MOVE_NONE
963 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
965 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
967 ss->skipNullMove = true;
968 search<PvNode>(pos, ss, alpha, beta, d, ply);
969 ss->skipNullMove = false;
971 ttMove = ss->bestMove;
972 tte = TT.retrieve(posKey);
975 // Expensive mate threat detection (only for PV nodes)
977 mateThreat = pos.has_mate_threat();
979 split_point_start: // At split points actual search starts from here
981 // Initialize a MovePicker object for the current position
982 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
984 ss->bestMove = MOVE_NONE;
985 futilityBase = ss->eval + ss->evalMargin;
986 singularExtensionNode = !Root
988 && depth >= SingularExtensionDepth[PvNode]
991 && !excludedMove // Do not allow recursive singular extension search
992 && (tte->type() & VALUE_TYPE_LOWER)
993 && tte->depth() >= depth - 3 * ONE_PLY;
996 lock_grab(&(sp->lock));
997 bestValue = sp->bestValue;
1000 // Step 10. Loop through moves
1001 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1002 while ( bestValue < beta
1003 && (move = mp.get_next_move()) != MOVE_NONE
1004 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1006 assert(move_is_ok(move));
1010 moveCount = ++sp->moveCount;
1011 lock_release(&(sp->lock));
1013 else if (move == excludedMove)
1020 // This is used by time management
1021 FirstRootMove = (moveCount == 1);
1023 // Save the current node count before the move is searched
1024 nodes = pos.nodes_searched();
1026 // If it's time to send nodes info, do it here where we have the
1027 // correct accumulated node counts searched by each thread.
1028 if (SendSearchedNodes)
1030 SendSearchedNodes = false;
1031 cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
1034 if (current_search_time() >= 1000)
1035 cout << "info currmove " << move
1036 << " currmovenumber " << moveCount << endl;
1039 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1040 moveIsCheck = pos.move_is_check(move, ci);
1041 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1043 // Step 11. Decide the new search depth
1044 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1046 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1047 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1048 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1049 // lower than ttValue minus a margin then we extend ttMove.
1050 if ( singularExtensionNode
1051 && move == tte->move()
1054 Value ttValue = value_from_tt(tte->value(), ply);
1056 if (abs(ttValue) < VALUE_KNOWN_WIN)
1058 Value b = ttValue - SingularExtensionMargin;
1059 ss->excludedMove = move;
1060 ss->skipNullMove = true;
1061 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1062 ss->skipNullMove = false;
1063 ss->excludedMove = MOVE_NONE;
1064 ss->bestMove = MOVE_NONE;
1070 // Update current move (this must be done after singular extension search)
1071 ss->currentMove = move;
1072 newDepth = depth - ONE_PLY + ext;
1074 // Step 12. Futility pruning (is omitted in PV nodes)
1076 && !captureOrPromotion
1080 && !move_is_castle(move))
1082 // Move count based pruning
1083 if ( moveCount >= futility_move_count(depth)
1084 && !(threatMove && connected_threat(pos, move, threatMove))
1085 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1088 lock_grab(&(sp->lock));
1093 // Value based pruning
1094 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1095 // but fixing this made program slightly weaker.
1096 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1097 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1098 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1100 if (futilityValueScaled < beta)
1104 lock_grab(&(sp->lock));
1105 if (futilityValueScaled > sp->bestValue)
1106 sp->bestValue = bestValue = futilityValueScaled;
1108 else if (futilityValueScaled > bestValue)
1109 bestValue = futilityValueScaled;
1114 // Prune moves with negative SEE at low depths
1115 if ( predictedDepth < 2 * ONE_PLY
1116 && bestValue > value_mated_in(PLY_MAX)
1117 && pos.see_sign(move) < 0)
1120 lock_grab(&(sp->lock));
1126 // Step 13. Make the move
1127 pos.do_move(move, st, ci, moveIsCheck);
1129 if (!SpNode && !captureOrPromotion)
1130 movesSearched[playedMoveCount++] = move;
1132 // Step extra. pv search (only in PV nodes)
1133 // The first move in list is the expected PV
1136 // Aspiration window is disabled in multi-pv case
1137 if (Root && MultiPV > 1)
1138 alpha = -VALUE_INFINITE;
1140 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1144 // Step 14. Reduced depth search
1145 // If the move fails high will be re-searched at full depth.
1146 bool doFullDepthSearch = true;
1148 if ( depth >= 3 * ONE_PLY
1149 && !captureOrPromotion
1151 && !move_is_castle(move)
1152 && ss->killers[0] != move
1153 && ss->killers[1] != move)
1155 ss->reduction = reduction<PvNode>(depth, moveCount);
1158 alpha = SpNode ? sp->alpha : alpha;
1159 Depth d = newDepth - ss->reduction;
1160 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1162 doFullDepthSearch = (value > alpha);
1164 ss->reduction = DEPTH_ZERO; // Restore original reduction
1167 // Step 15. Full depth search
1168 if (doFullDepthSearch)
1170 alpha = SpNode ? sp->alpha : alpha;
1171 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1173 // Step extra. pv search (only in PV nodes)
1174 // Search only for possible new PV nodes, if instead value >= beta then
1175 // parent node fails low with value <= alpha and tries another move.
1176 if (PvNode && value > alpha && (Root || value < beta))
1177 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1181 // Step 16. Undo move
1182 pos.undo_move(move);
1184 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1186 // Step 17. Check for new best move
1189 lock_grab(&(sp->lock));
1190 bestValue = sp->bestValue;
1194 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1199 sp->bestValue = value;
1201 if (!Root && value > alpha)
1203 if (PvNode && value < beta) // We want always alpha < beta
1211 sp->betaCutoff = true;
1213 if (value == value_mate_in(ply + 1))
1214 ss->mateKiller = move;
1216 ss->bestMove = move;
1219 sp->ss->bestMove = move;
1225 // Finished searching the move. If StopRequest is true, the search
1226 // was aborted because the user interrupted the search or because we
1227 // ran out of time. In this case, the return value of the search cannot
1228 // be trusted, and we break out of the loop without updating the best
1233 // Remember searched nodes counts for this move
1234 mp.rm->nodes += pos.nodes_searched() - nodes;
1236 // PV move or new best move ?
1237 if (isPvMove || value > alpha)
1240 ss->bestMove = move;
1241 mp.rm->pv_score = value;
1242 mp.rm->extract_pv_from_tt(pos);
1244 // We record how often the best move has been changed in each
1245 // iteration. This information is used for time management: When
1246 // the best move changes frequently, we allocate some more time.
1247 if (!isPvMove && MultiPV == 1)
1248 Rml.bestMoveChanges++;
1250 Rml.sort_multipv(moveCount);
1252 // Update alpha. In multi-pv we don't use aspiration window, so
1253 // set alpha equal to minimum score among the PV lines.
1255 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1256 else if (value > alpha)
1260 mp.rm->pv_score = -VALUE_INFINITE;
1264 // Step 18. Check for split
1267 && depth >= ThreadsMgr.min_split_depth()
1268 && ThreadsMgr.active_threads() > 1
1270 && ThreadsMgr.available_thread_exists(threadID)
1272 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1273 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1274 threatMove, mateThreat, moveCount, &mp, PvNode);
1277 // Step 19. Check for mate and stalemate
1278 // All legal moves have been searched and if there are
1279 // no legal moves, it must be mate or stalemate.
1280 // If one move was excluded return fail low score.
1281 if (!SpNode && !moveCount)
1282 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1284 // Step 20. Update tables
1285 // If the search is not aborted, update the transposition table,
1286 // history counters, and killer moves.
1287 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1289 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1290 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1291 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1293 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1295 // Update killers and history only for non capture moves that fails high
1296 if ( bestValue >= beta
1297 && !pos.move_is_capture_or_promotion(move))
1299 update_history(pos, move, depth, movesSearched, playedMoveCount);
1300 update_killers(move, ss->killers);
1306 // Here we have the lock still grabbed
1307 sp->slaves[threadID] = 0;
1308 sp->nodes += pos.nodes_searched();
1309 lock_release(&(sp->lock));
1312 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1317 // qsearch() is the quiescence search function, which is called by the main
1318 // search function when the remaining depth is zero (or, to be more precise,
1319 // less than ONE_PLY).
1321 template <NodeType PvNode>
1322 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1324 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1325 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1326 assert(PvNode || alpha == beta - 1);
1328 assert(ply > 0 && ply < PLY_MAX);
1329 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1333 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1334 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1337 Value oldAlpha = alpha;
1339 ss->bestMove = ss->currentMove = MOVE_NONE;
1341 // Check for an instant draw or maximum ply reached
1342 if (pos.is_draw() || ply >= PLY_MAX - 1)
1345 // Decide whether or not to include checks, this fixes also the type of
1346 // TT entry depth that we are going to use. Note that in qsearch we use
1347 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1348 isCheck = pos.is_check();
1349 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1351 // Transposition table lookup. At PV nodes, we don't use the TT for
1352 // pruning, but only for move ordering.
1353 tte = TT.retrieve(pos.get_key());
1354 ttMove = (tte ? tte->move() : MOVE_NONE);
1356 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1358 ss->bestMove = ttMove; // Can be MOVE_NONE
1359 return value_from_tt(tte->value(), ply);
1362 // Evaluate the position statically
1365 bestValue = futilityBase = -VALUE_INFINITE;
1366 ss->eval = evalMargin = VALUE_NONE;
1367 enoughMaterial = false;
1373 assert(tte->static_value() != VALUE_NONE);
1375 evalMargin = tte->static_value_margin();
1376 ss->eval = bestValue = tte->static_value();
1379 ss->eval = bestValue = evaluate(pos, evalMargin);
1381 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1383 // Stand pat. Return immediately if static value is at least beta
1384 if (bestValue >= beta)
1387 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1392 if (PvNode && bestValue > alpha)
1395 // Futility pruning parameters, not needed when in check
1396 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1397 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1400 // Initialize a MovePicker object for the current position, and prepare
1401 // to search the moves. Because the depth is <= 0 here, only captures,
1402 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1404 MovePicker mp(pos, ttMove, depth, H);
1407 // Loop through the moves until no moves remain or a beta cutoff occurs
1408 while ( alpha < beta
1409 && (move = mp.get_next_move()) != MOVE_NONE)
1411 assert(move_is_ok(move));
1413 moveIsCheck = pos.move_is_check(move, ci);
1421 && !move_is_promotion(move)
1422 && !pos.move_is_passed_pawn_push(move))
1424 futilityValue = futilityBase
1425 + pos.endgame_value_of_piece_on(move_to(move))
1426 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1428 if (futilityValue < alpha)
1430 if (futilityValue > bestValue)
1431 bestValue = futilityValue;
1436 // Detect non-capture evasions that are candidate to be pruned
1437 evasionPrunable = isCheck
1438 && bestValue > value_mated_in(PLY_MAX)
1439 && !pos.move_is_capture(move)
1440 && !pos.can_castle(pos.side_to_move());
1442 // Don't search moves with negative SEE values
1444 && (!isCheck || evasionPrunable)
1446 && !move_is_promotion(move)
1447 && pos.see_sign(move) < 0)
1450 // Don't search useless checks
1455 && !pos.move_is_capture_or_promotion(move)
1456 && ss->eval + PawnValueMidgame / 4 < beta
1457 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1459 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1460 bestValue = ss->eval + PawnValueMidgame / 4;
1465 // Update current move
1466 ss->currentMove = move;
1468 // Make and search the move
1469 pos.do_move(move, st, ci, moveIsCheck);
1470 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1471 pos.undo_move(move);
1473 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1476 if (value > bestValue)
1482 ss->bestMove = move;
1487 // All legal moves have been searched. A special case: If we're in check
1488 // and no legal moves were found, it is checkmate.
1489 if (isCheck && bestValue == -VALUE_INFINITE)
1490 return value_mated_in(ply);
1492 // Update transposition table
1493 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1494 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1496 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1502 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1503 // it is used in RootMoveList to get an initial scoring.
1504 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1506 SearchStack ss[PLY_MAX_PLUS_2];
1509 memset(ss, 0, 4 * sizeof(SearchStack));
1510 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1512 for (MoveStack* cur = mlist; cur != last; cur++)
1514 ss[0].currentMove = cur->move;
1515 pos.do_move(cur->move, st);
1516 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1517 pos.undo_move(cur->move);
1522 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1523 // bestValue is updated only when returning false because in that case move
1526 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1528 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1529 Square from, to, ksq, victimSq;
1532 Value futilityValue, bv = *bestValue;
1534 from = move_from(move);
1536 them = opposite_color(pos.side_to_move());
1537 ksq = pos.king_square(them);
1538 kingAtt = pos.attacks_from<KING>(ksq);
1539 pc = pos.piece_on(from);
1541 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1542 oldAtt = pos.attacks_from(pc, from, occ);
1543 newAtt = pos.attacks_from(pc, to, occ);
1545 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1546 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1548 if (!(b && (b & (b - 1))))
1551 // Rule 2. Queen contact check is very dangerous
1552 if ( type_of_piece(pc) == QUEEN
1553 && bit_is_set(kingAtt, to))
1556 // Rule 3. Creating new double threats with checks
1557 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1561 victimSq = pop_1st_bit(&b);
1562 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1564 // Note that here we generate illegal "double move"!
1565 if ( futilityValue >= beta
1566 && pos.see_sign(make_move(from, victimSq)) >= 0)
1569 if (futilityValue > bv)
1573 // Update bestValue only if check is not dangerous (because we will prune the move)
1579 // connected_moves() tests whether two moves are 'connected' in the sense
1580 // that the first move somehow made the second move possible (for instance
1581 // if the moving piece is the same in both moves). The first move is assumed
1582 // to be the move that was made to reach the current position, while the
1583 // second move is assumed to be a move from the current position.
1585 bool connected_moves(const Position& pos, Move m1, Move m2) {
1587 Square f1, t1, f2, t2;
1590 assert(m1 && move_is_ok(m1));
1591 assert(m2 && move_is_ok(m2));
1593 // Case 1: The moving piece is the same in both moves
1599 // Case 2: The destination square for m2 was vacated by m1
1605 // Case 3: Moving through the vacated square
1606 if ( piece_is_slider(pos.piece_on(f2))
1607 && bit_is_set(squares_between(f2, t2), f1))
1610 // Case 4: The destination square for m2 is defended by the moving piece in m1
1611 p = pos.piece_on(t1);
1612 if (bit_is_set(pos.attacks_from(p, t1), t2))
1615 // Case 5: Discovered check, checking piece is the piece moved in m1
1616 if ( piece_is_slider(p)
1617 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1618 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1620 // discovered_check_candidates() works also if the Position's side to
1621 // move is the opposite of the checking piece.
1622 Color them = opposite_color(pos.side_to_move());
1623 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1625 if (bit_is_set(dcCandidates, f2))
1632 // value_is_mate() checks if the given value is a mate one eventually
1633 // compensated for the ply.
1635 bool value_is_mate(Value value) {
1637 assert(abs(value) <= VALUE_INFINITE);
1639 return value <= value_mated_in(PLY_MAX)
1640 || value >= value_mate_in(PLY_MAX);
1644 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1645 // "plies to mate from the current ply". Non-mate scores are unchanged.
1646 // The function is called before storing a value to the transposition table.
1648 Value value_to_tt(Value v, int ply) {
1650 if (v >= value_mate_in(PLY_MAX))
1653 if (v <= value_mated_in(PLY_MAX))
1660 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1661 // the transposition table to a mate score corrected for the current ply.
1663 Value value_from_tt(Value v, int ply) {
1665 if (v >= value_mate_in(PLY_MAX))
1668 if (v <= value_mated_in(PLY_MAX))
1675 // extension() decides whether a move should be searched with normal depth,
1676 // or with extended depth. Certain classes of moves (checking moves, in
1677 // particular) are searched with bigger depth than ordinary moves and in
1678 // any case are marked as 'dangerous'. Note that also if a move is not
1679 // extended, as example because the corresponding UCI option is set to zero,
1680 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1681 template <NodeType PvNode>
1682 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1683 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1685 assert(m != MOVE_NONE);
1687 Depth result = DEPTH_ZERO;
1688 *dangerous = moveIsCheck | mateThreat;
1692 if (moveIsCheck && pos.see_sign(m) >= 0)
1693 result += CheckExtension[PvNode];
1696 result += MateThreatExtension[PvNode];
1699 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1701 Color c = pos.side_to_move();
1702 if (relative_rank(c, move_to(m)) == RANK_7)
1704 result += PawnPushTo7thExtension[PvNode];
1707 if (pos.pawn_is_passed(c, move_to(m)))
1709 result += PassedPawnExtension[PvNode];
1714 if ( captureOrPromotion
1715 && pos.type_of_piece_on(move_to(m)) != PAWN
1716 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1717 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1718 && !move_is_promotion(m)
1721 result += PawnEndgameExtension[PvNode];
1726 && captureOrPromotion
1727 && pos.type_of_piece_on(move_to(m)) != PAWN
1728 && pos.see_sign(m) >= 0)
1730 result += ONE_PLY / 2;
1734 return Min(result, ONE_PLY);
1738 // connected_threat() tests whether it is safe to forward prune a move or if
1739 // is somehow connected to the threat move returned by null search.
1741 bool connected_threat(const Position& pos, Move m, Move threat) {
1743 assert(move_is_ok(m));
1744 assert(threat && move_is_ok(threat));
1745 assert(!pos.move_is_check(m));
1746 assert(!pos.move_is_capture_or_promotion(m));
1747 assert(!pos.move_is_passed_pawn_push(m));
1749 Square mfrom, mto, tfrom, tto;
1751 mfrom = move_from(m);
1753 tfrom = move_from(threat);
1754 tto = move_to(threat);
1756 // Case 1: Don't prune moves which move the threatened piece
1760 // Case 2: If the threatened piece has value less than or equal to the
1761 // value of the threatening piece, don't prune moves which defend it.
1762 if ( pos.move_is_capture(threat)
1763 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1764 || pos.type_of_piece_on(tfrom) == KING)
1765 && pos.move_attacks_square(m, tto))
1768 // Case 3: If the moving piece in the threatened move is a slider, don't
1769 // prune safe moves which block its ray.
1770 if ( piece_is_slider(pos.piece_on(tfrom))
1771 && bit_is_set(squares_between(tfrom, tto), mto)
1772 && pos.see_sign(m) >= 0)
1779 // ok_to_use_TT() returns true if a transposition table score
1780 // can be used at a given point in search.
1782 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1784 Value v = value_from_tt(tte->value(), ply);
1786 return ( tte->depth() >= depth
1787 || v >= Max(value_mate_in(PLY_MAX), beta)
1788 || v < Min(value_mated_in(PLY_MAX), beta))
1790 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1791 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1795 // refine_eval() returns the transposition table score if
1796 // possible otherwise falls back on static position evaluation.
1798 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1802 Value v = value_from_tt(tte->value(), ply);
1804 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1805 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1812 // update_history() registers a good move that produced a beta-cutoff
1813 // in history and marks as failures all the other moves of that ply.
1815 void update_history(const Position& pos, Move move, Depth depth,
1816 Move movesSearched[], int moveCount) {
1818 Value bonus = Value(int(depth) * int(depth));
1820 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1822 for (int i = 0; i < moveCount - 1; i++)
1824 m = movesSearched[i];
1828 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1833 // update_killers() add a good move that produced a beta-cutoff
1834 // among the killer moves of that ply.
1836 void update_killers(Move m, Move killers[]) {
1838 if (m != killers[0])
1840 killers[1] = killers[0];
1846 // update_gains() updates the gains table of a non-capture move given
1847 // the static position evaluation before and after the move.
1849 void update_gains(const Position& pos, Move m, Value before, Value after) {
1852 && before != VALUE_NONE
1853 && after != VALUE_NONE
1854 && pos.captured_piece_type() == PIECE_TYPE_NONE
1855 && !move_is_special(m))
1856 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1859 // current_search_time() returns the number of milliseconds which have passed
1860 // since the beginning of the current search.
1862 int current_search_time() {
1864 return get_system_time() - SearchStartTime;
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 // speed_to_uci() returns a string with time stats of current search suitable
1889 // to be sent to UCI gui.
1891 std::string speed_to_uci(int64_t nodes) {
1893 std::stringstream s;
1894 int t = current_search_time();
1896 s << " nodes " << nodes
1897 << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
1904 // poll() performs two different functions: It polls for user input, and it
1905 // looks at the time consumed so far and decides if it's time to abort the
1908 void poll(const Position& pos) {
1910 static int lastInfoTime;
1911 int t = current_search_time();
1914 if (input_available())
1916 // We are line oriented, don't read single chars
1917 std::string command;
1919 if (!std::getline(std::cin, command))
1922 if (command == "quit")
1924 // Quit the program as soon as possible
1926 QuitRequest = StopRequest = true;
1929 else if (command == "stop")
1931 // Stop calculating as soon as possible, but still send the "bestmove"
1932 // and possibly the "ponder" token when finishing the search.
1936 else if (command == "ponderhit")
1938 // The opponent has played the expected move. GUI sends "ponderhit" if
1939 // we were told to ponder on the same move the opponent has played. We
1940 // should continue searching but switching from pondering to normal search.
1943 if (StopOnPonderhit)
1948 // Print search information
1952 else if (lastInfoTime > t)
1953 // HACK: Must be a new search where we searched less than
1954 // NodesBetweenPolls nodes during the first second of search.
1957 else if (t - lastInfoTime >= 1000)
1964 if (dbg_show_hit_rate)
1965 dbg_print_hit_rate();
1967 // Send info on searched nodes as soon as we return to root
1968 SendSearchedNodes = true;
1971 // Should we stop the search?
1975 bool stillAtFirstMove = FirstRootMove
1976 && !AspirationFailLow
1977 && t > TimeMgr.available_time();
1979 bool noMoreTime = t > TimeMgr.maximum_time()
1980 || stillAtFirstMove;
1982 if ( (UseTimeManagement && noMoreTime)
1983 || (ExactMaxTime && t >= ExactMaxTime)
1984 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1989 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1990 // while the program is pondering. The point is to work around a wrinkle in
1991 // the UCI protocol: When pondering, the engine is not allowed to give a
1992 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1993 // We simply wait here until one of these commands is sent, and return,
1994 // after which the bestmove and pondermove will be printed.
1996 void wait_for_stop_or_ponderhit() {
1998 std::string command;
2002 // Wait for a command from stdin
2003 if (!std::getline(std::cin, command))
2006 if (command == "quit")
2011 else if (command == "ponderhit" || command == "stop")
2017 // init_thread() is the function which is called when a new thread is
2018 // launched. It simply calls the idle_loop() function with the supplied
2019 // threadID. There are two versions of this function; one for POSIX
2020 // threads and one for Windows threads.
2022 #if !defined(_MSC_VER)
2024 void* init_thread(void* threadID) {
2026 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2032 DWORD WINAPI init_thread(LPVOID threadID) {
2034 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2041 /// The ThreadsManager class
2044 // read_uci_options() updates number of active threads and other internal
2045 // parameters according to the UCI options values. It is called before
2046 // to start a new search.
2048 void ThreadsManager::read_uci_options() {
2050 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2051 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2052 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2053 activeThreads = Options["Threads"].value<int>();
2057 // idle_loop() is where the threads are parked when they have no work to do.
2058 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2059 // object for which the current thread is the master.
2061 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2063 assert(threadID >= 0 && threadID < MAX_THREADS);
2066 bool allFinished = false;
2070 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2071 // master should exit as last one.
2072 if (allThreadsShouldExit)
2075 threads[threadID].state = THREAD_TERMINATED;
2079 // If we are not thinking, wait for a condition to be signaled
2080 // instead of wasting CPU time polling for work.
2081 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2082 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2084 assert(!sp || useSleepingThreads);
2085 assert(threadID != 0 || useSleepingThreads);
2087 if (threads[threadID].state == THREAD_INITIALIZING)
2088 threads[threadID].state = THREAD_AVAILABLE;
2090 // Grab the lock to avoid races with wake_sleeping_thread()
2091 lock_grab(&sleepLock[threadID]);
2093 // If we are master and all slaves have finished do not go to sleep
2094 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2095 allFinished = (i == activeThreads);
2097 if (allFinished || allThreadsShouldExit)
2099 lock_release(&sleepLock[threadID]);
2103 // Do sleep here after retesting sleep conditions
2104 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2105 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2107 lock_release(&sleepLock[threadID]);
2110 // If this thread has been assigned work, launch a search
2111 if (threads[threadID].state == THREAD_WORKISWAITING)
2113 assert(!allThreadsShouldExit);
2115 threads[threadID].state = THREAD_SEARCHING;
2117 // Copy SplitPoint position and search stack and call search()
2118 // with SplitPoint template parameter set to true.
2119 SearchStack ss[PLY_MAX_PLUS_2];
2120 SplitPoint* tsp = threads[threadID].splitPoint;
2121 Position pos(*tsp->pos, threadID);
2123 memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
2127 search<PV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2129 search<NonPV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2131 assert(threads[threadID].state == THREAD_SEARCHING);
2133 threads[threadID].state = THREAD_AVAILABLE;
2135 // Wake up master thread so to allow it to return from the idle loop in
2136 // case we are the last slave of the split point.
2137 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2138 wake_sleeping_thread(tsp->master);
2141 // If this thread is the master of a split point and all slaves have
2142 // finished their work at this split point, return from the idle loop.
2143 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2144 allFinished = (i == activeThreads);
2148 // Because sp->slaves[] is reset under lock protection,
2149 // be sure sp->lock has been released before to return.
2150 lock_grab(&(sp->lock));
2151 lock_release(&(sp->lock));
2153 // In helpful master concept a master can help only a sub-tree, and
2154 // because here is all finished is not possible master is booked.
2155 assert(threads[threadID].state == THREAD_AVAILABLE);
2157 threads[threadID].state = THREAD_SEARCHING;
2164 // init_threads() is called during startup. It launches all helper threads,
2165 // and initializes the split point stack and the global locks and condition
2168 void ThreadsManager::init_threads() {
2170 int i, arg[MAX_THREADS];
2173 // Initialize global locks
2176 for (i = 0; i < MAX_THREADS; i++)
2178 lock_init(&sleepLock[i]);
2179 cond_init(&sleepCond[i]);
2182 // Initialize splitPoints[] locks
2183 for (i = 0; i < MAX_THREADS; i++)
2184 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2185 lock_init(&(threads[i].splitPoints[j].lock));
2187 // Will be set just before program exits to properly end the threads
2188 allThreadsShouldExit = false;
2190 // Threads will be put all threads to sleep as soon as created
2193 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2194 threads[0].state = THREAD_SEARCHING;
2195 for (i = 1; i < MAX_THREADS; i++)
2196 threads[i].state = THREAD_INITIALIZING;
2198 // Launch the helper threads
2199 for (i = 1; i < MAX_THREADS; i++)
2203 #if !defined(_MSC_VER)
2204 pthread_t pthread[1];
2205 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2206 pthread_detach(pthread[0]);
2208 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2212 cout << "Failed to create thread number " << i << endl;
2216 // Wait until the thread has finished launching and is gone to sleep
2217 while (threads[i].state == THREAD_INITIALIZING) {}
2222 // exit_threads() is called when the program exits. It makes all the
2223 // helper threads exit cleanly.
2225 void ThreadsManager::exit_threads() {
2227 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2229 // Wake up all the threads and waits for termination
2230 for (int i = 1; i < MAX_THREADS; i++)
2232 wake_sleeping_thread(i);
2233 while (threads[i].state != THREAD_TERMINATED) {}
2236 // Now we can safely destroy the locks
2237 for (int i = 0; i < MAX_THREADS; i++)
2238 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2239 lock_destroy(&(threads[i].splitPoints[j].lock));
2241 lock_destroy(&mpLock);
2243 // Now we can safely destroy the wait conditions
2244 for (int i = 0; i < MAX_THREADS; i++)
2246 lock_destroy(&sleepLock[i]);
2247 cond_destroy(&sleepCond[i]);
2252 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2253 // the thread's currently active split point, or in some ancestor of
2254 // the current split point.
2256 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2258 assert(threadID >= 0 && threadID < activeThreads);
2260 SplitPoint* sp = threads[threadID].splitPoint;
2262 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2267 // thread_is_available() checks whether the thread with threadID "slave" is
2268 // available to help the thread with threadID "master" at a split point. An
2269 // obvious requirement is that "slave" must be idle. With more than two
2270 // threads, this is not by itself sufficient: If "slave" is the master of
2271 // some active split point, it is only available as a slave to the other
2272 // threads which are busy searching the split point at the top of "slave"'s
2273 // split point stack (the "helpful master concept" in YBWC terminology).
2275 bool ThreadsManager::thread_is_available(int slave, int master) const {
2277 assert(slave >= 0 && slave < activeThreads);
2278 assert(master >= 0 && master < activeThreads);
2279 assert(activeThreads > 1);
2281 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2284 // Make a local copy to be sure doesn't change under our feet
2285 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2287 // No active split points means that the thread is available as
2288 // a slave for any other thread.
2289 if (localActiveSplitPoints == 0 || activeThreads == 2)
2292 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2293 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2294 // could have been set to 0 by another thread leading to an out of bound access.
2295 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2302 // available_thread_exists() tries to find an idle thread which is available as
2303 // a slave for the thread with threadID "master".
2305 bool ThreadsManager::available_thread_exists(int master) const {
2307 assert(master >= 0 && master < activeThreads);
2308 assert(activeThreads > 1);
2310 for (int i = 0; i < activeThreads; i++)
2311 if (thread_is_available(i, master))
2318 // split() does the actual work of distributing the work at a node between
2319 // several available threads. If it does not succeed in splitting the
2320 // node (because no idle threads are available, or because we have no unused
2321 // split point objects), the function immediately returns. If splitting is
2322 // possible, a SplitPoint object is initialized with all the data that must be
2323 // copied to the helper threads and we tell our helper threads that they have
2324 // been assigned work. This will cause them to instantly leave their idle loops and
2325 // call search().When all threads have returned from search() then split() returns.
2327 template <bool Fake>
2328 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2329 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2330 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2331 assert(pos.is_ok());
2332 assert(ply > 0 && ply < PLY_MAX);
2333 assert(*bestValue >= -VALUE_INFINITE);
2334 assert(*bestValue <= *alpha);
2335 assert(*alpha < beta);
2336 assert(beta <= VALUE_INFINITE);
2337 assert(depth > DEPTH_ZERO);
2338 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2339 assert(activeThreads > 1);
2341 int i, master = pos.thread();
2342 Thread& masterThread = threads[master];
2346 // If no other thread is available to help us, or if we have too many
2347 // active split points, don't split.
2348 if ( !available_thread_exists(master)
2349 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2351 lock_release(&mpLock);
2355 // Pick the next available split point object from the split point stack
2356 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2358 // Initialize the split point object
2359 splitPoint.parent = masterThread.splitPoint;
2360 splitPoint.master = master;
2361 splitPoint.betaCutoff = false;
2362 splitPoint.ply = ply;
2363 splitPoint.depth = depth;
2364 splitPoint.threatMove = threatMove;
2365 splitPoint.mateThreat = mateThreat;
2366 splitPoint.alpha = *alpha;
2367 splitPoint.beta = beta;
2368 splitPoint.pvNode = pvNode;
2369 splitPoint.bestValue = *bestValue;
2371 splitPoint.moveCount = moveCount;
2372 splitPoint.pos = &pos;
2373 splitPoint.nodes = 0;
2375 for (i = 0; i < activeThreads; i++)
2376 splitPoint.slaves[i] = 0;
2378 masterThread.splitPoint = &splitPoint;
2380 // If we are here it means we are not available
2381 assert(masterThread.state != THREAD_AVAILABLE);
2383 int workersCnt = 1; // At least the master is included
2385 // Allocate available threads setting state to THREAD_BOOKED
2386 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2387 if (thread_is_available(i, master))
2389 threads[i].state = THREAD_BOOKED;
2390 threads[i].splitPoint = &splitPoint;
2391 splitPoint.slaves[i] = 1;
2395 assert(Fake || workersCnt > 1);
2397 // We can release the lock because slave threads are already booked and master is not available
2398 lock_release(&mpLock);
2400 // Tell the threads that they have work to do. This will make them leave
2402 for (i = 0; i < activeThreads; i++)
2403 if (i == master || splitPoint.slaves[i])
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 << speed_to_uci(pos.nodes_searched())
2546 << " pv " << l.str();
2552 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2554 MoveStack mlist[MOVES_MAX];
2558 bestMoveChanges = 0;
2560 // Generate all legal moves and score them
2561 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2562 qsearch_scoring(pos, mlist, last);
2564 // Add each move to the RootMoveList's vector
2565 for (MoveStack* cur = mlist; cur != last; cur++)
2567 // If we have a searchMoves[] list then verify cur->move
2568 // is in the list before to add it.
2569 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2571 if (searchMoves[0] && *sm != cur->move)
2575 rm.pv[0] = cur->move;
2576 rm.pv[1] = MOVE_NONE;
2577 rm.pv_score = Value(cur->score);