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(const Position& pos, Value alpha, Value beta, int pvLine = 0);
137 Move pv[PLY_MAX_PLUS_2];
141 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
142 // with an handful of methods above the standard ones.
144 struct RootMoveList : public std::vector<RootMove> {
146 typedef std::vector<RootMove> Base;
148 RootMoveList(Position& pos, Move searchMoves[]);
149 void set_non_pv_scores(const Position& pos);
151 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
152 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n + 1); }
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& m) {
166 os.iword(0) = int(m);
175 // Maximum depth for razoring
176 const Depth RazorDepth = 4 * ONE_PLY;
178 // Dynamic razoring margin based on depth
179 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
181 // Maximum depth for use of dynamic threat detection when null move fails low
182 const Depth ThreatDepth = 5 * ONE_PLY;
184 // Step 9. Internal iterative deepening
186 // Minimum depth for use of internal iterative deepening
187 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
189 // At Non-PV nodes we do an internal iterative deepening search
190 // when the static evaluation is bigger then beta - IIDMargin.
191 const Value IIDMargin = Value(0x100);
193 // Step 11. Decide the new search depth
195 // Extensions. Configurable UCI options
196 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
197 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
198 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
200 // Minimum depth for use of singular extension
201 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
203 // If the TT move is at least SingularExtensionMargin better then the
204 // remaining ones we will extend it.
205 const Value SingularExtensionMargin = Value(0x20);
207 // Step 12. Futility pruning
209 // Futility margin for quiescence search
210 const Value FutilityMarginQS = Value(0x80);
212 // Futility lookup tables (initialized at startup) and their getter functions
213 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
214 int FutilityMoveCountArray[32]; // [depth]
216 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
217 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
219 // Step 14. Reduced search
221 // Reduction lookup tables (initialized at startup) and their getter functions
222 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
224 template <NodeType PV>
225 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
227 // Common adjustments
229 // Search depth at iteration 1
230 const Depth InitialDepth = ONE_PLY;
232 // Easy move margin. An easy move candidate must be at least this much
233 // better than the second best move.
234 const Value EasyMoveMargin = Value(0x200);
237 /// Namespace variables
245 // Scores and number of times the best move changed for each iteration
246 Value ValueByIteration[PLY_MAX_PLUS_2];
247 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
249 // Search window management
255 // Time managment variables
256 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
257 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
258 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
263 std::ofstream LogFile;
265 // Multi-threads manager object
266 ThreadsManager ThreadsMgr;
268 // Node counters, used only by thread[0] but try to keep in different cache
269 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
270 bool SendSearchedNodes;
272 int NodesBetweenPolls = 30000;
279 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
280 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
282 template <NodeType PvNode, bool SpNode>
283 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
285 template <NodeType PvNode>
286 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
288 template <NodeType PvNode>
289 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
291 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
292 : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
295 template <NodeType PvNode>
296 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
298 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
299 bool connected_moves(const Position& pos, Move m1, Move m2);
300 bool value_is_mate(Value value);
301 Value value_to_tt(Value v, int ply);
302 Value value_from_tt(Value v, int ply);
303 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
304 bool connected_threat(const Position& pos, Move m, Move threat);
305 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
306 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
307 void update_killers(Move m, SearchStack* ss);
308 void update_gains(const Position& pos, Move move, Value before, Value after);
310 int current_search_time();
311 std::string value_to_uci(Value v);
312 int nps(const Position& pos);
313 void poll(const Position& pos);
314 void wait_for_stop_or_ponderhit();
315 void init_ss_array(SearchStack* ss, int size);
317 #if !defined(_MSC_VER)
318 void* init_thread(void* threadID);
320 DWORD WINAPI init_thread(LPVOID threadID);
330 /// init_threads(), exit_threads() and nodes_searched() are helpers to
331 /// give accessibility to some TM methods from outside of current file.
333 void init_threads() { ThreadsMgr.init_threads(); }
334 void exit_threads() { ThreadsMgr.exit_threads(); }
337 /// init_search() is called during startup. It initializes various lookup tables
341 int d; // depth (ONE_PLY == 2)
342 int hd; // half depth (ONE_PLY == 1)
345 // Init reductions array
346 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
348 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
349 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
350 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
351 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
354 // Init futility margins array
355 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
356 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
358 // Init futility move count array
359 for (d = 0; d < 32; d++)
360 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
364 /// perft() is our utility to verify move generation is bug free. All the legal
365 /// moves up to given depth are generated and counted and the sum returned.
367 int perft(Position& pos, Depth depth)
369 MoveStack mlist[MOVES_MAX];
374 // Generate all legal moves
375 MoveStack* last = generate_moves(pos, mlist);
377 // If we are at the last ply we don't need to do and undo
378 // the moves, just to count them.
379 if (depth <= ONE_PLY)
380 return int(last - mlist);
382 // Loop through all legal moves
384 for (MoveStack* cur = mlist; cur != last; cur++)
387 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
388 sum += perft(pos, depth - ONE_PLY);
395 /// think() is the external interface to Stockfish's search, and is called when
396 /// the program receives the UCI 'go' command. It initializes various
397 /// search-related global variables, and calls root_search(). It returns false
398 /// when a quit command is received during the search.
400 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
401 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
403 // Initialize global search variables
404 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
406 SearchStartTime = get_system_time();
407 ExactMaxTime = maxTime;
410 InfiniteSearch = infinite;
412 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
414 // Look for a book move, only during games, not tests
415 if (UseTimeManagement && Options["OwnBook"].value<bool>())
417 if (Options["Book File"].value<std::string>() != OpeningBook.file_name())
418 OpeningBook.open(Options["Book File"].value<std::string>());
420 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
421 if (bookMove != MOVE_NONE)
424 wait_for_stop_or_ponderhit();
426 cout << "bestmove " << bookMove << endl;
431 // Read UCI option values
432 TT.set_size(Options["Hash"].value<int>());
433 if (Options["Clear Hash"].value<bool>())
435 Options["Clear Hash"].set_value("false");
439 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
440 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
441 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
442 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
443 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
444 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
445 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
446 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
447 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
448 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
449 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
450 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
451 MultiPV = Options["MultiPV"].value<int>();
452 UseLogFile = Options["Use Search Log"].value<bool>();
454 read_evaluation_uci_options(pos.side_to_move());
456 // Set the number of active threads
457 ThreadsMgr.read_uci_options();
458 init_eval(ThreadsMgr.active_threads());
460 // Wake up needed threads
461 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
462 ThreadsMgr.wake_sleeping_thread(i);
465 int myTime = time[pos.side_to_move()];
466 int myIncrement = increment[pos.side_to_move()];
467 if (UseTimeManagement)
468 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
470 // Set best NodesBetweenPolls interval to avoid lagging under
471 // heavy time pressure.
473 NodesBetweenPolls = Min(MaxNodes, 30000);
474 else if (myTime && myTime < 1000)
475 NodesBetweenPolls = 1000;
476 else if (myTime && myTime < 5000)
477 NodesBetweenPolls = 5000;
479 NodesBetweenPolls = 30000;
481 // Write search information to log file
484 std::string name = Options["Search Log Filename"].value<std::string>();
485 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
487 LogFile << "Searching: " << pos.to_fen()
488 << "\ninfinite: " << infinite
489 << " ponder: " << ponder
490 << " time: " << myTime
491 << " increment: " << myIncrement
492 << " moves to go: " << movesToGo << endl;
495 // We're ready to start thinking. Call the iterative deepening loop function
496 Move ponderMove = MOVE_NONE;
497 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
499 // Print final search statistics
500 cout << "info nodes " << pos.nodes_searched()
501 << " nps " << nps(pos)
502 << " time " << current_search_time() << endl;
506 LogFile << "\nNodes: " << pos.nodes_searched()
507 << "\nNodes/second: " << nps(pos)
508 << "\nBest move: " << move_to_san(pos, bestMove);
511 pos.do_move(bestMove, st);
512 LogFile << "\nPonder move: "
513 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
519 // This makes all the threads to go to sleep
520 ThreadsMgr.set_active_threads(1);
522 // If we are pondering or in infinite search, we shouldn't print the
523 // best move before we are told to do so.
524 if (!StopRequest && (Pondering || InfiniteSearch))
525 wait_for_stop_or_ponderhit();
527 // Could be both MOVE_NONE when searching on a stalemate position
528 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
536 // id_loop() is the main iterative deepening loop. It calls root_search
537 // repeatedly with increasing depth until the allocated thinking time has
538 // been consumed, the user stops the search, or the maximum search depth is
541 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
543 SearchStack ss[PLY_MAX_PLUS_2];
545 Move EasyMove = MOVE_NONE;
546 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
548 // Moves to search are verified, scored and sorted
549 RootMoveList rml(pos, searchMoves);
551 // Handle special case of searching on a mate/stale position
554 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
556 cout << "info depth " << 1
557 << " score " << value_to_uci(s) << endl;
565 init_ss_array(ss, PLY_MAX_PLUS_2);
566 ValueByIteration[1] = rml[0].pv_score;
569 // Send initial RootMoveList scoring (iteration 1)
570 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
571 << "info depth " << Iteration
572 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
574 // Is one move significantly better than others after initial scoring ?
576 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
577 EasyMove = rml[0].pv[0];
579 // Iterative deepening loop
580 while (Iteration < PLY_MAX)
582 // Initialize iteration
584 BestMoveChangesByIteration[Iteration] = 0;
586 cout << "info depth " << Iteration << endl;
588 // Calculate dynamic aspiration window based on previous iterations
589 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
591 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
592 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
594 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
595 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
597 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
598 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
601 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
603 // Search to the current depth, rml is updated and sorted
604 value = root_search(pos, ss, alpha, beta, depth, rml);
607 break; // Value cannot be trusted. Break out immediately!
609 //Save info about search result
610 ValueByIteration[Iteration] = value;
612 // Drop the easy move if differs from the new best move
613 if (rml[0].pv[0] != EasyMove)
614 EasyMove = MOVE_NONE;
616 if (UseTimeManagement)
619 bool stopSearch = false;
621 // Stop search early if there is only a single legal move,
622 // we search up to Iteration 6 anyway to get a proper score.
623 if (Iteration >= 6 && rml.size() == 1)
626 // Stop search early when the last two iterations returned a mate score
628 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
629 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
632 // Stop search early if one move seems to be much better than the others
634 && EasyMove == rml[0].pv[0]
635 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
636 && current_search_time() > TimeMgr.available_time() / 16)
637 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
638 && current_search_time() > TimeMgr.available_time() / 32)))
641 // Add some extra time if the best move has changed during the last two iterations
642 if (Iteration > 5 && Iteration <= 50)
643 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
644 BestMoveChangesByIteration[Iteration-1]);
646 // Stop search if most of MaxSearchTime is consumed at the end of the
647 // iteration. We probably don't have enough time to search the first
648 // move at the next iteration anyway.
649 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
655 StopOnPonderhit = true;
661 if (MaxDepth && Iteration >= MaxDepth)
665 *ponderMove = rml[0].pv[1];
670 // root_search() is the function which searches the root node. It is
671 // similar to search_pv except that it prints some information to the
672 // standard output and handles the fail low/high loops.
674 Value root_search(Position& pos, SearchStack* ss, Value alpha,
675 Value beta, Depth depth, RootMoveList& rml) {
681 Value value, oldAlpha;
682 bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
683 int researchCountFH, researchCountFL;
685 researchCountFH = researchCountFL = 0;
687 isCheck = pos.is_check();
689 // Step 1. Initialize node (polling is omitted at root)
690 ss->currentMove = ss->bestMove = MOVE_NONE;
692 // Step 2. Check for aborted search (omitted at root)
693 // Step 3. Mate distance pruning (omitted at root)
694 // Step 4. Transposition table lookup (omitted at root)
696 // Step 5. Evaluate the position statically
697 // At root we do this only to get reference value for child nodes
698 ss->evalMargin = VALUE_NONE;
699 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
701 // Step 6. Razoring (omitted at root)
702 // Step 7. Static null move pruning (omitted at root)
703 // Step 8. Null move search with verification search (omitted at root)
704 // Step 9. Internal iterative deepening (omitted at root)
706 // Step extra. Fail low loop
707 // We start with small aspiration window and in case of fail low, we research
708 // with bigger window until we are not failing low anymore.
711 // Sort the moves before to (re)search
712 rml.set_non_pv_scores(pos);
715 // Step 10. Loop through all moves in the root move list
716 for (int i = 0; i < (int)rml.size() && !StopRequest; i++)
718 // This is used by time management
719 FirstRootMove = (i == 0);
721 // Save the current node count before the move is searched
722 nodes = pos.nodes_searched();
724 // If it's time to send nodes info, do it here where we have the
725 // correct accumulated node counts searched by each thread.
726 if (SendSearchedNodes)
728 SendSearchedNodes = false;
729 cout << "info nodes " << nodes
730 << " nps " << nps(pos)
731 << " time " << current_search_time() << endl;
734 // Pick the next root move, and print the move and the move number to
735 // the standard output.
736 move = ss->currentMove = rml[i].pv[0];
738 if (current_search_time() >= 1000)
739 cout << "info currmove " << move
740 << " currmovenumber " << i + 1 << endl;
742 moveIsCheck = pos.move_is_check(move);
743 captureOrPromotion = pos.move_is_capture_or_promotion(move);
745 // Step 11. Decide the new search depth
746 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
747 newDepth = depth + ext;
749 // Step 12. Futility pruning (omitted at root)
751 // Step extra. Fail high loop
752 // If move fails high, we research with bigger window until we are not failing
754 value = -VALUE_INFINITE;
758 // Step 13. Make the move
759 pos.do_move(move, st, ci, moveIsCheck);
761 // Step extra. pv search
762 // We do pv search for first moves (i < MultiPV)
763 // and for fail high research (value > alpha)
764 if (i < MultiPV || value > alpha)
766 // Aspiration window is disabled in multi-pv case
768 alpha = -VALUE_INFINITE;
770 // Full depth PV search, done on first move or after a fail high
771 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
775 // Step 14. Reduced search
776 // if the move fails high will be re-searched at full depth
777 bool doFullDepthSearch = true;
779 if ( depth >= 3 * ONE_PLY
781 && !captureOrPromotion
782 && !move_is_castle(move))
784 ss->reduction = reduction<PV>(depth, i - MultiPV + 2);
787 assert(newDepth-ss->reduction >= ONE_PLY);
789 // Reduced depth non-pv search using alpha as upperbound
790 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
791 doFullDepthSearch = (value > alpha);
793 ss->reduction = DEPTH_ZERO; // Restore original reduction
796 // Step 15. Full depth search
797 if (doFullDepthSearch)
799 // Full depth non-pv search using alpha as upperbound
800 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
802 // If we are above alpha then research at same depth but as PV
803 // to get a correct score or eventually a fail high above beta.
805 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
809 // Step 16. Undo move
812 // Can we exit fail high loop ?
813 if (StopRequest || value < beta)
816 // We are failing high and going to do a research. It's important to update
817 // the score before research in case we run out of time while researching.
819 rml[i].pv_score = value;
820 rml[i].extract_pv_from_tt(pos);
822 // Inform GUI that PV has changed
823 cout << rml[i].pv_info_to_uci(pos, alpha, beta) << endl;
825 // Prepare for a research after a fail high, each time with a wider window
826 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
829 } // End of fail high loop
831 // Finished searching the move. If AbortSearch is true, the search
832 // was aborted because the user interrupted the search or because we
833 // ran out of time. In this case, the return value of the search cannot
834 // be trusted, and we break out of the loop without updating the best
839 // Remember searched nodes counts for this move
840 rml[i].nodes += pos.nodes_searched() - nodes;
842 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
843 assert(value < beta);
845 // Step 17. Check for new best move
846 if (value <= alpha && i >= MultiPV)
847 rml[i].pv_score = -VALUE_INFINITE;
850 // PV move or new best move!
854 rml[i].pv_score = value;
855 rml[i].extract_pv_from_tt(pos);
857 // We record how often the best move has been changed in each
858 // iteration. This information is used for time managment: When
859 // the best move changes frequently, we allocate some more time.
860 if (MultiPV == 1 && i > 0)
861 BestMoveChangesByIteration[Iteration]++;
863 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
864 // requires we send all the PV lines properly sorted.
867 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
868 cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
870 // Update alpha. In multi-pv we don't use aspiration window
873 // Raise alpha to setup proper non-pv search upper bound
877 else // Set alpha equal to minimum score among the PV lines
878 alpha = rml[Min(i, MultiPV - 1)].pv_score;
880 } // PV move or new best move
882 assert(alpha >= oldAlpha);
884 AspirationFailLow = (alpha == oldAlpha);
886 if (AspirationFailLow && StopOnPonderhit)
887 StopOnPonderhit = false;
891 // Can we exit fail low loop ?
892 if (StopRequest || !AspirationFailLow)
895 // Prepare for a research after a fail low, each time with a wider window
896 oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
901 // Sort the moves before to return
904 // Write PV lines to transposition table, in case the relevant entries
905 // have been overwritten during the search.
906 for (int i = 0; i < MultiPV; i++)
907 rml[i].insert_pv_in_tt(pos);
913 // search<>() is the main search function for both PV and non-PV nodes and for
914 // normal and SplitPoint nodes. When called just after a split point the search
915 // is simpler because we have already probed the hash table, done a null move
916 // search, and searched the first move before splitting, we don't have to repeat
917 // all this work again. We also don't need to store anything to the hash table
918 // here: This is taken care of after we return from the split point.
920 template <NodeType PvNode, bool SpNode>
921 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
923 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
924 assert(beta > alpha && beta <= VALUE_INFINITE);
925 assert(PvNode || alpha == beta - 1);
926 assert(ply > 0 && ply < PLY_MAX);
927 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
929 Move movesSearched[MOVES_MAX];
933 Move ttMove, move, excludedMove, threatMove;
936 Value bestValue, value, oldAlpha;
937 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
938 bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
939 bool mateThreat = false;
941 int threadID = pos.thread();
942 SplitPoint* sp = NULL;
943 refinedValue = bestValue = value = -VALUE_INFINITE;
945 isCheck = pos.is_check();
951 ttMove = excludedMove = MOVE_NONE;
952 threatMove = sp->threatMove;
953 mateThreat = sp->mateThreat;
954 goto split_point_start;
956 else {} // Hack to fix icc's "statement is unreachable" warning
958 // Step 1. Initialize node and poll. Polling can abort search
959 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
960 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
962 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
968 // Step 2. Check for aborted search and immediate draw
970 || ThreadsMgr.cutoff_at_splitpoint(threadID)
972 || ply >= PLY_MAX - 1)
975 // Step 3. Mate distance pruning
976 alpha = Max(value_mated_in(ply), alpha);
977 beta = Min(value_mate_in(ply+1), beta);
981 // Step 4. Transposition table lookup
983 // We don't want the score of a partial search to overwrite a previous full search
984 // TT value, so we use a different position key in case of an excluded move exists.
985 excludedMove = ss->excludedMove;
986 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
988 tte = TT.retrieve(posKey);
989 ttMove = tte ? tte->move() : MOVE_NONE;
991 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
992 // This is to avoid problems in the following areas:
994 // * Repetition draw detection
995 // * Fifty move rule detection
996 // * Searching for a mate
997 // * Printing of full PV line
998 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1001 ss->bestMove = ttMove; // Can be MOVE_NONE
1002 return value_from_tt(tte->value(), ply);
1005 // Step 5. Evaluate the position statically and
1006 // update gain statistics of parent move.
1008 ss->eval = ss->evalMargin = VALUE_NONE;
1011 assert(tte->static_value() != VALUE_NONE);
1013 ss->eval = tte->static_value();
1014 ss->evalMargin = tte->static_value_margin();
1015 refinedValue = refine_eval(tte, ss->eval, ply);
1019 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1020 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1023 // Save gain for the parent non-capture move
1024 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1026 // Step 6. Razoring (is omitted in PV nodes)
1028 && depth < RazorDepth
1030 && refinedValue < beta - razor_margin(depth)
1031 && ttMove == MOVE_NONE
1032 && !value_is_mate(beta)
1033 && !pos.has_pawn_on_7th(pos.side_to_move()))
1035 Value rbeta = beta - razor_margin(depth);
1036 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1038 // Logically we should return (v + razor_margin(depth)), but
1039 // surprisingly this did slightly weaker in tests.
1043 // Step 7. Static null move pruning (is omitted in PV nodes)
1044 // We're betting that the opponent doesn't have a move that will reduce
1045 // the score by more than futility_margin(depth) if we do a null move.
1047 && !ss->skipNullMove
1048 && depth < RazorDepth
1050 && refinedValue >= beta + futility_margin(depth, 0)
1051 && !value_is_mate(beta)
1052 && pos.non_pawn_material(pos.side_to_move()))
1053 return refinedValue - futility_margin(depth, 0);
1055 // Step 8. Null move search with verification search (is omitted in PV nodes)
1057 && !ss->skipNullMove
1060 && refinedValue >= beta
1061 && !value_is_mate(beta)
1062 && pos.non_pawn_material(pos.side_to_move()))
1064 ss->currentMove = MOVE_NULL;
1066 // Null move dynamic reduction based on depth
1067 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1069 // Null move dynamic reduction based on value
1070 if (refinedValue - beta > PawnValueMidgame)
1073 pos.do_null_move(st);
1074 (ss+1)->skipNullMove = true;
1075 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1076 (ss+1)->skipNullMove = false;
1077 pos.undo_null_move();
1079 if (nullValue >= beta)
1081 // Do not return unproven mate scores
1082 if (nullValue >= value_mate_in(PLY_MAX))
1085 if (depth < 6 * ONE_PLY)
1088 // Do verification search at high depths
1089 ss->skipNullMove = true;
1090 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1091 ss->skipNullMove = false;
1098 // The null move failed low, which means that we may be faced with
1099 // some kind of threat. If the previous move was reduced, check if
1100 // the move that refuted the null move was somehow connected to the
1101 // move which was reduced. If a connection is found, return a fail
1102 // low score (which will cause the reduced move to fail high in the
1103 // parent node, which will trigger a re-search with full depth).
1104 if (nullValue == value_mated_in(ply + 2))
1107 threatMove = (ss+1)->bestMove;
1108 if ( depth < ThreatDepth
1109 && (ss-1)->reduction
1110 && threatMove != MOVE_NONE
1111 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1116 // Step 9. Internal iterative deepening
1117 if ( depth >= IIDDepth[PvNode]
1118 && ttMove == MOVE_NONE
1119 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1121 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1123 ss->skipNullMove = true;
1124 search<PvNode>(pos, ss, alpha, beta, d, ply);
1125 ss->skipNullMove = false;
1127 ttMove = ss->bestMove;
1128 tte = TT.retrieve(posKey);
1131 // Expensive mate threat detection (only for PV nodes)
1133 mateThreat = pos.has_mate_threat();
1135 split_point_start: // At split points actual search starts from here
1137 // Initialize a MovePicker object for the current position
1138 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1139 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1140 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1142 ss->bestMove = MOVE_NONE;
1143 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1144 futilityBase = ss->eval + ss->evalMargin;
1145 singularExtensionNode = !SpNode
1146 && depth >= SingularExtensionDepth[PvNode]
1149 && !excludedMove // Do not allow recursive singular extension search
1150 && (tte->type() & VALUE_TYPE_LOWER)
1151 && tte->depth() >= depth - 3 * ONE_PLY;
1154 lock_grab(&(sp->lock));
1155 bestValue = sp->bestValue;
1158 // Step 10. Loop through moves
1159 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1160 while ( bestValue < beta
1161 && (move = mp.get_next_move()) != MOVE_NONE
1162 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1164 assert(move_is_ok(move));
1168 moveCount = ++sp->moveCount;
1169 lock_release(&(sp->lock));
1171 else if (move == excludedMove)
1174 movesSearched[moveCount++] = move;
1176 moveIsCheck = pos.move_is_check(move, ci);
1177 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1179 // Step 11. Decide the new search depth
1180 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1182 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1183 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1184 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1185 // lower then ttValue minus a margin then we extend ttMove.
1186 if ( singularExtensionNode
1187 && move == tte->move()
1190 Value ttValue = value_from_tt(tte->value(), ply);
1192 if (abs(ttValue) < VALUE_KNOWN_WIN)
1194 Value b = ttValue - SingularExtensionMargin;
1195 ss->excludedMove = move;
1196 ss->skipNullMove = true;
1197 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1198 ss->skipNullMove = false;
1199 ss->excludedMove = MOVE_NONE;
1200 ss->bestMove = MOVE_NONE;
1206 // Update current move (this must be done after singular extension search)
1207 ss->currentMove = move;
1208 newDepth = depth - ONE_PLY + ext;
1210 // Step 12. Futility pruning (is omitted in PV nodes)
1212 && !captureOrPromotion
1216 && !move_is_castle(move))
1218 // Move count based pruning
1219 if ( moveCount >= futility_move_count(depth)
1220 && !(threatMove && connected_threat(pos, move, threatMove))
1221 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1224 lock_grab(&(sp->lock));
1229 // Value based pruning
1230 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1231 // but fixing this made program slightly weaker.
1232 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1233 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1234 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1236 if (futilityValueScaled < beta)
1240 lock_grab(&(sp->lock));
1241 if (futilityValueScaled > sp->bestValue)
1242 sp->bestValue = bestValue = futilityValueScaled;
1244 else if (futilityValueScaled > bestValue)
1245 bestValue = futilityValueScaled;
1250 // Prune moves with negative SEE at low depths
1251 if ( predictedDepth < 2 * ONE_PLY
1252 && bestValue > value_mated_in(PLY_MAX)
1253 && pos.see_sign(move) < 0)
1256 lock_grab(&(sp->lock));
1262 // Step 13. Make the move
1263 pos.do_move(move, st, ci, moveIsCheck);
1265 // Step extra. pv search (only in PV nodes)
1266 // The first move in list is the expected PV
1267 if (PvNode && moveCount == 1)
1268 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1271 // Step 14. Reduced depth search
1272 // If the move fails high will be re-searched at full depth.
1273 bool doFullDepthSearch = true;
1275 if ( depth >= 3 * ONE_PLY
1276 && !captureOrPromotion
1278 && !move_is_castle(move)
1279 && ss->killers[0] != move
1280 && ss->killers[1] != move)
1282 ss->reduction = reduction<PvNode>(depth, moveCount);
1286 alpha = SpNode ? sp->alpha : alpha;
1287 Depth d = newDepth - ss->reduction;
1288 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1290 doFullDepthSearch = (value > alpha);
1292 ss->reduction = DEPTH_ZERO; // Restore original reduction
1295 // Step 15. Full depth search
1296 if (doFullDepthSearch)
1298 alpha = SpNode ? sp->alpha : alpha;
1299 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1301 // Step extra. pv search (only in PV nodes)
1302 // Search only for possible new PV nodes, if instead value >= beta then
1303 // parent node fails low with value <= alpha and tries another move.
1304 if (PvNode && value > alpha && value < beta)
1305 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1309 // Step 16. Undo move
1310 pos.undo_move(move);
1312 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1314 // Step 17. Check for new best move
1317 lock_grab(&(sp->lock));
1318 bestValue = sp->bestValue;
1322 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1327 sp->bestValue = value;
1331 if (PvNode && value < beta) // We want always alpha < beta
1339 sp->betaCutoff = true;
1341 if (value == value_mate_in(ply + 1))
1342 ss->mateKiller = move;
1344 ss->bestMove = move;
1347 sp->parentSstack->bestMove = move;
1351 // Step 18. Check for split
1353 && depth >= ThreadsMgr.min_split_depth()
1354 && ThreadsMgr.active_threads() > 1
1356 && ThreadsMgr.available_thread_exists(threadID)
1358 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1360 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1361 threatMove, mateThreat, moveCount, &mp, PvNode);
1364 // Step 19. Check for mate and stalemate
1365 // All legal moves have been searched and if there are
1366 // no legal moves, it must be mate or stalemate.
1367 // If one move was excluded return fail low score.
1368 if (!SpNode && !moveCount)
1369 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1371 // Step 20. Update tables
1372 // If the search is not aborted, update the transposition table,
1373 // history counters, and killer moves.
1374 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1376 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1377 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1378 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1380 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1382 // Update killers and history only for non capture moves that fails high
1383 if ( bestValue >= beta
1384 && !pos.move_is_capture_or_promotion(move))
1386 update_history(pos, move, depth, movesSearched, moveCount);
1387 update_killers(move, ss);
1393 // Here we have the lock still grabbed
1394 sp->slaves[threadID] = 0;
1395 sp->nodes += pos.nodes_searched();
1396 lock_release(&(sp->lock));
1399 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1404 // qsearch() is the quiescence search function, which is called by the main
1405 // search function when the remaining depth is zero (or, to be more precise,
1406 // less than ONE_PLY).
1408 template <NodeType PvNode>
1409 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1411 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1412 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1413 assert(PvNode || alpha == beta - 1);
1415 assert(ply > 0 && ply < PLY_MAX);
1416 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1420 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1421 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1424 Value oldAlpha = alpha;
1426 ss->bestMove = ss->currentMove = MOVE_NONE;
1428 // Check for an instant draw or maximum ply reached
1429 if (pos.is_draw() || ply >= PLY_MAX - 1)
1432 // Decide whether or not to include checks, this fixes also the type of
1433 // TT entry depth that we are going to use. Note that in qsearch we use
1434 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1435 isCheck = pos.is_check();
1436 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1438 // Transposition table lookup. At PV nodes, we don't use the TT for
1439 // pruning, but only for move ordering.
1440 tte = TT.retrieve(pos.get_key());
1441 ttMove = (tte ? tte->move() : MOVE_NONE);
1443 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1445 ss->bestMove = ttMove; // Can be MOVE_NONE
1446 return value_from_tt(tte->value(), ply);
1449 // Evaluate the position statically
1452 bestValue = futilityBase = -VALUE_INFINITE;
1453 ss->eval = evalMargin = VALUE_NONE;
1454 enoughMaterial = false;
1460 assert(tte->static_value() != VALUE_NONE);
1462 evalMargin = tte->static_value_margin();
1463 ss->eval = bestValue = tte->static_value();
1466 ss->eval = bestValue = evaluate(pos, evalMargin);
1468 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1470 // Stand pat. Return immediately if static value is at least beta
1471 if (bestValue >= beta)
1474 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1479 if (PvNode && bestValue > alpha)
1482 // Futility pruning parameters, not needed when in check
1483 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1484 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1487 // Initialize a MovePicker object for the current position, and prepare
1488 // to search the moves. Because the depth is <= 0 here, only captures,
1489 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1491 MovePicker mp(pos, ttMove, depth, H);
1494 // Loop through the moves until no moves remain or a beta cutoff occurs
1495 while ( alpha < beta
1496 && (move = mp.get_next_move()) != MOVE_NONE)
1498 assert(move_is_ok(move));
1500 moveIsCheck = pos.move_is_check(move, ci);
1508 && !move_is_promotion(move)
1509 && !pos.move_is_passed_pawn_push(move))
1511 futilityValue = futilityBase
1512 + pos.endgame_value_of_piece_on(move_to(move))
1513 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1515 if (futilityValue < alpha)
1517 if (futilityValue > bestValue)
1518 bestValue = futilityValue;
1523 // Detect non-capture evasions that are candidate to be pruned
1524 evasionPrunable = isCheck
1525 && bestValue > value_mated_in(PLY_MAX)
1526 && !pos.move_is_capture(move)
1527 && !pos.can_castle(pos.side_to_move());
1529 // Don't search moves with negative SEE values
1531 && (!isCheck || evasionPrunable)
1533 && !move_is_promotion(move)
1534 && pos.see_sign(move) < 0)
1537 // Don't search useless checks
1542 && !pos.move_is_capture_or_promotion(move)
1543 && ss->eval + PawnValueMidgame / 4 < beta
1544 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1546 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1547 bestValue = ss->eval + PawnValueMidgame / 4;
1552 // Update current move
1553 ss->currentMove = move;
1555 // Make and search the move
1556 pos.do_move(move, st, ci, moveIsCheck);
1557 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1558 pos.undo_move(move);
1560 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1563 if (value > bestValue)
1569 ss->bestMove = move;
1574 // All legal moves have been searched. A special case: If we're in check
1575 // and no legal moves were found, it is checkmate.
1576 if (isCheck && bestValue == -VALUE_INFINITE)
1577 return value_mated_in(ply);
1579 // Update transposition table
1580 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1581 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1583 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1589 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1590 // bestValue is updated only when returning false because in that case move
1593 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1595 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1596 Square from, to, ksq, victimSq;
1599 Value futilityValue, bv = *bestValue;
1601 from = move_from(move);
1603 them = opposite_color(pos.side_to_move());
1604 ksq = pos.king_square(them);
1605 kingAtt = pos.attacks_from<KING>(ksq);
1606 pc = pos.piece_on(from);
1608 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1609 oldAtt = pos.attacks_from(pc, from, occ);
1610 newAtt = pos.attacks_from(pc, to, occ);
1612 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1613 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1615 if (!(b && (b & (b - 1))))
1618 // Rule 2. Queen contact check is very dangerous
1619 if ( type_of_piece(pc) == QUEEN
1620 && bit_is_set(kingAtt, to))
1623 // Rule 3. Creating new double threats with checks
1624 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1628 victimSq = pop_1st_bit(&b);
1629 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1631 // Note that here we generate illegal "double move"!
1632 if ( futilityValue >= beta
1633 && pos.see_sign(make_move(from, victimSq)) >= 0)
1636 if (futilityValue > bv)
1640 // Update bestValue only if check is not dangerous (because we will prune the move)
1646 // connected_moves() tests whether two moves are 'connected' in the sense
1647 // that the first move somehow made the second move possible (for instance
1648 // if the moving piece is the same in both moves). The first move is assumed
1649 // to be the move that was made to reach the current position, while the
1650 // second move is assumed to be a move from the current position.
1652 bool connected_moves(const Position& pos, Move m1, Move m2) {
1654 Square f1, t1, f2, t2;
1657 assert(m1 && move_is_ok(m1));
1658 assert(m2 && move_is_ok(m2));
1660 // Case 1: The moving piece is the same in both moves
1666 // Case 2: The destination square for m2 was vacated by m1
1672 // Case 3: Moving through the vacated square
1673 if ( piece_is_slider(pos.piece_on(f2))
1674 && bit_is_set(squares_between(f2, t2), f1))
1677 // Case 4: The destination square for m2 is defended by the moving piece in m1
1678 p = pos.piece_on(t1);
1679 if (bit_is_set(pos.attacks_from(p, t1), t2))
1682 // Case 5: Discovered check, checking piece is the piece moved in m1
1683 if ( piece_is_slider(p)
1684 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1685 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1687 // discovered_check_candidates() works also if the Position's side to
1688 // move is the opposite of the checking piece.
1689 Color them = opposite_color(pos.side_to_move());
1690 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1692 if (bit_is_set(dcCandidates, f2))
1699 // value_is_mate() checks if the given value is a mate one eventually
1700 // compensated for the ply.
1702 bool value_is_mate(Value value) {
1704 assert(abs(value) <= VALUE_INFINITE);
1706 return value <= value_mated_in(PLY_MAX)
1707 || value >= value_mate_in(PLY_MAX);
1711 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1712 // "plies to mate from the current ply". Non-mate scores are unchanged.
1713 // The function is called before storing a value to the transposition table.
1715 Value value_to_tt(Value v, int ply) {
1717 if (v >= value_mate_in(PLY_MAX))
1720 if (v <= value_mated_in(PLY_MAX))
1727 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1728 // the transposition table to a mate score corrected for the current ply.
1730 Value value_from_tt(Value v, int ply) {
1732 if (v >= value_mate_in(PLY_MAX))
1735 if (v <= value_mated_in(PLY_MAX))
1742 // extension() decides whether a move should be searched with normal depth,
1743 // or with extended depth. Certain classes of moves (checking moves, in
1744 // particular) are searched with bigger depth than ordinary moves and in
1745 // any case are marked as 'dangerous'. Note that also if a move is not
1746 // extended, as example because the corresponding UCI option is set to zero,
1747 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1748 template <NodeType PvNode>
1749 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1750 bool singleEvasion, bool mateThreat, bool* dangerous) {
1752 assert(m != MOVE_NONE);
1754 Depth result = DEPTH_ZERO;
1755 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1759 if (moveIsCheck && pos.see_sign(m) >= 0)
1760 result += CheckExtension[PvNode];
1763 result += SingleEvasionExtension[PvNode];
1766 result += MateThreatExtension[PvNode];
1769 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1771 Color c = pos.side_to_move();
1772 if (relative_rank(c, move_to(m)) == RANK_7)
1774 result += PawnPushTo7thExtension[PvNode];
1777 if (pos.pawn_is_passed(c, move_to(m)))
1779 result += PassedPawnExtension[PvNode];
1784 if ( captureOrPromotion
1785 && pos.type_of_piece_on(move_to(m)) != PAWN
1786 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1787 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1788 && !move_is_promotion(m)
1791 result += PawnEndgameExtension[PvNode];
1796 && captureOrPromotion
1797 && pos.type_of_piece_on(move_to(m)) != PAWN
1798 && pos.see_sign(m) >= 0)
1800 result += ONE_PLY / 2;
1804 return Min(result, ONE_PLY);
1808 // connected_threat() tests whether it is safe to forward prune a move or if
1809 // is somehow coonected to the threat move returned by null search.
1811 bool connected_threat(const Position& pos, Move m, Move threat) {
1813 assert(move_is_ok(m));
1814 assert(threat && move_is_ok(threat));
1815 assert(!pos.move_is_check(m));
1816 assert(!pos.move_is_capture_or_promotion(m));
1817 assert(!pos.move_is_passed_pawn_push(m));
1819 Square mfrom, mto, tfrom, tto;
1821 mfrom = move_from(m);
1823 tfrom = move_from(threat);
1824 tto = move_to(threat);
1826 // Case 1: Don't prune moves which move the threatened piece
1830 // Case 2: If the threatened piece has value less than or equal to the
1831 // value of the threatening piece, don't prune move which defend it.
1832 if ( pos.move_is_capture(threat)
1833 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1834 || pos.type_of_piece_on(tfrom) == KING)
1835 && pos.move_attacks_square(m, tto))
1838 // Case 3: If the moving piece in the threatened move is a slider, don't
1839 // prune safe moves which block its ray.
1840 if ( piece_is_slider(pos.piece_on(tfrom))
1841 && bit_is_set(squares_between(tfrom, tto), mto)
1842 && pos.see_sign(m) >= 0)
1849 // ok_to_use_TT() returns true if a transposition table score
1850 // can be used at a given point in search.
1852 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1854 Value v = value_from_tt(tte->value(), ply);
1856 return ( tte->depth() >= depth
1857 || v >= Max(value_mate_in(PLY_MAX), beta)
1858 || v < Min(value_mated_in(PLY_MAX), beta))
1860 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1861 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1865 // refine_eval() returns the transposition table score if
1866 // possible otherwise falls back on static position evaluation.
1868 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1872 Value v = value_from_tt(tte->value(), ply);
1874 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1875 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1882 // update_history() registers a good move that produced a beta-cutoff
1883 // in history and marks as failures all the other moves of that ply.
1885 void update_history(const Position& pos, Move move, Depth depth,
1886 Move movesSearched[], int moveCount) {
1889 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
1891 for (int i = 0; i < moveCount - 1; i++)
1893 m = movesSearched[i];
1897 if (!pos.move_is_capture_or_promotion(m))
1898 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
1903 // update_killers() add a good move that produced a beta-cutoff
1904 // among the killer moves of that ply.
1906 void update_killers(Move m, SearchStack* ss) {
1908 if (m == ss->killers[0])
1911 ss->killers[1] = ss->killers[0];
1916 // update_gains() updates the gains table of a non-capture move given
1917 // the static position evaluation before and after the move.
1919 void update_gains(const Position& pos, Move m, Value before, Value after) {
1922 && before != VALUE_NONE
1923 && after != VALUE_NONE
1924 && pos.captured_piece_type() == PIECE_TYPE_NONE
1925 && !move_is_special(m))
1926 H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1930 // init_ss_array() does a fast reset of the first entries of a SearchStack
1931 // array and of all the excludedMove and skipNullMove entries.
1933 void init_ss_array(SearchStack* ss, int size) {
1935 for (int i = 0; i < size; i++, ss++)
1937 ss->excludedMove = MOVE_NONE;
1938 ss->skipNullMove = false;
1939 ss->reduction = DEPTH_ZERO;
1943 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1948 // value_to_uci() converts a value to a string suitable for use with the UCI
1949 // protocol specifications:
1951 // cp <x> The score from the engine's point of view in centipawns.
1952 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1953 // use negative values for y.
1955 std::string value_to_uci(Value v) {
1957 std::stringstream s;
1959 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1960 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1962 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1968 // current_search_time() returns the number of milliseconds which have passed
1969 // since the beginning of the current search.
1971 int current_search_time() {
1973 return get_system_time() - SearchStartTime;
1977 // nps() computes the current nodes/second count
1979 int nps(const Position& pos) {
1981 int t = current_search_time();
1982 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1986 // poll() performs two different functions: It polls for user input, and it
1987 // looks at the time consumed so far and decides if it's time to abort the
1990 void poll(const Position& pos) {
1992 static int lastInfoTime;
1993 int t = current_search_time();
1996 if (data_available())
1998 // We are line oriented, don't read single chars
1999 std::string command;
2001 if (!std::getline(std::cin, command))
2004 if (command == "quit")
2006 // Quit the program as soon as possible
2008 QuitRequest = StopRequest = true;
2011 else if (command == "stop")
2013 // Stop calculating as soon as possible, but still send the "bestmove"
2014 // and possibly the "ponder" token when finishing the search.
2018 else if (command == "ponderhit")
2020 // The opponent has played the expected move. GUI sends "ponderhit" if
2021 // we were told to ponder on the same move the opponent has played. We
2022 // should continue searching but switching from pondering to normal search.
2025 if (StopOnPonderhit)
2030 // Print search information
2034 else if (lastInfoTime > t)
2035 // HACK: Must be a new search where we searched less than
2036 // NodesBetweenPolls nodes during the first second of search.
2039 else if (t - lastInfoTime >= 1000)
2046 if (dbg_show_hit_rate)
2047 dbg_print_hit_rate();
2049 // Send info on searched nodes as soon as we return to root
2050 SendSearchedNodes = true;
2053 // Should we stop the search?
2057 bool stillAtFirstMove = FirstRootMove
2058 && !AspirationFailLow
2059 && t > TimeMgr.available_time();
2061 bool noMoreTime = t > TimeMgr.maximum_time()
2062 || stillAtFirstMove;
2064 if ( (UseTimeManagement && noMoreTime)
2065 || (ExactMaxTime && t >= ExactMaxTime)
2066 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2071 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2072 // while the program is pondering. The point is to work around a wrinkle in
2073 // the UCI protocol: When pondering, the engine is not allowed to give a
2074 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2075 // We simply wait here until one of these commands is sent, and return,
2076 // after which the bestmove and pondermove will be printed.
2078 void wait_for_stop_or_ponderhit() {
2080 std::string command;
2084 // Wait for a command from stdin
2085 if (!std::getline(std::cin, command))
2088 if (command == "quit")
2093 else if (command == "ponderhit" || command == "stop")
2099 // init_thread() is the function which is called when a new thread is
2100 // launched. It simply calls the idle_loop() function with the supplied
2101 // threadID. There are two versions of this function; one for POSIX
2102 // threads and one for Windows threads.
2104 #if !defined(_MSC_VER)
2106 void* init_thread(void* threadID) {
2108 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2114 DWORD WINAPI init_thread(LPVOID threadID) {
2116 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2123 /// The ThreadsManager class
2126 // read_uci_options() updates number of active threads and other internal
2127 // parameters according to the UCI options values. It is called before
2128 // to start a new search.
2130 void ThreadsManager::read_uci_options() {
2132 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2133 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2134 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2135 activeThreads = Options["Threads"].value<int>();
2139 // idle_loop() is where the threads are parked when they have no work to do.
2140 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2141 // object for which the current thread is the master.
2143 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2145 assert(threadID >= 0 && threadID < MAX_THREADS);
2148 bool allFinished = false;
2152 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2153 // master should exit as last one.
2154 if (allThreadsShouldExit)
2157 threads[threadID].state = THREAD_TERMINATED;
2161 // If we are not thinking, wait for a condition to be signaled
2162 // instead of wasting CPU time polling for work.
2163 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2164 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2166 assert(!sp || useSleepingThreads);
2167 assert(threadID != 0 || useSleepingThreads);
2169 if (threads[threadID].state == THREAD_INITIALIZING)
2170 threads[threadID].state = THREAD_AVAILABLE;
2172 // Grab the lock to avoid races with wake_sleeping_thread()
2173 lock_grab(&sleepLock[threadID]);
2175 // If we are master and all slaves have finished do not go to sleep
2176 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2177 allFinished = (i == activeThreads);
2179 if (allFinished || allThreadsShouldExit)
2181 lock_release(&sleepLock[threadID]);
2185 // Do sleep here after retesting sleep conditions
2186 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2187 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2189 lock_release(&sleepLock[threadID]);
2192 // If this thread has been assigned work, launch a search
2193 if (threads[threadID].state == THREAD_WORKISWAITING)
2195 assert(!allThreadsShouldExit);
2197 threads[threadID].state = THREAD_SEARCHING;
2199 // Here we call search() with SplitPoint template parameter set to true
2200 SplitPoint* tsp = threads[threadID].splitPoint;
2201 Position pos(*tsp->pos, threadID);
2202 SearchStack* ss = tsp->sstack[threadID] + 1;
2206 search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2208 search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2210 assert(threads[threadID].state == THREAD_SEARCHING);
2212 threads[threadID].state = THREAD_AVAILABLE;
2214 // Wake up master thread so to allow it to return from the idle loop in
2215 // case we are the last slave of the split point.
2216 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2217 wake_sleeping_thread(tsp->master);
2220 // If this thread is the master of a split point and all slaves have
2221 // finished their work at this split point, return from the idle loop.
2222 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2223 allFinished = (i == activeThreads);
2227 // Because sp->slaves[] is reset under lock protection,
2228 // be sure sp->lock has been released before to return.
2229 lock_grab(&(sp->lock));
2230 lock_release(&(sp->lock));
2232 // In helpful master concept a master can help only a sub-tree, and
2233 // because here is all finished is not possible master is booked.
2234 assert(threads[threadID].state == THREAD_AVAILABLE);
2236 threads[threadID].state = THREAD_SEARCHING;
2243 // init_threads() is called during startup. It launches all helper threads,
2244 // and initializes the split point stack and the global locks and condition
2247 void ThreadsManager::init_threads() {
2249 int i, arg[MAX_THREADS];
2252 // Initialize global locks
2255 for (i = 0; i < MAX_THREADS; i++)
2257 lock_init(&sleepLock[i]);
2258 cond_init(&sleepCond[i]);
2261 // Initialize splitPoints[] locks
2262 for (i = 0; i < MAX_THREADS; i++)
2263 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2264 lock_init(&(threads[i].splitPoints[j].lock));
2266 // Will be set just before program exits to properly end the threads
2267 allThreadsShouldExit = false;
2269 // Threads will be put all threads to sleep as soon as created
2272 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2273 threads[0].state = THREAD_SEARCHING;
2274 for (i = 1; i < MAX_THREADS; i++)
2275 threads[i].state = THREAD_INITIALIZING;
2277 // Launch the helper threads
2278 for (i = 1; i < MAX_THREADS; i++)
2282 #if !defined(_MSC_VER)
2283 pthread_t pthread[1];
2284 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2285 pthread_detach(pthread[0]);
2287 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2291 cout << "Failed to create thread number " << i << endl;
2295 // Wait until the thread has finished launching and is gone to sleep
2296 while (threads[i].state == THREAD_INITIALIZING) {}
2301 // exit_threads() is called when the program exits. It makes all the
2302 // helper threads exit cleanly.
2304 void ThreadsManager::exit_threads() {
2306 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2308 // Wake up all the threads and waits for termination
2309 for (int i = 1; i < MAX_THREADS; i++)
2311 wake_sleeping_thread(i);
2312 while (threads[i].state != THREAD_TERMINATED) {}
2315 // Now we can safely destroy the locks
2316 for (int i = 0; i < MAX_THREADS; i++)
2317 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2318 lock_destroy(&(threads[i].splitPoints[j].lock));
2320 lock_destroy(&mpLock);
2322 // Now we can safely destroy the wait conditions
2323 for (int i = 0; i < MAX_THREADS; i++)
2325 lock_destroy(&sleepLock[i]);
2326 cond_destroy(&sleepCond[i]);
2331 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2332 // the thread's currently active split point, or in some ancestor of
2333 // the current split point.
2335 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2337 assert(threadID >= 0 && threadID < activeThreads);
2339 SplitPoint* sp = threads[threadID].splitPoint;
2341 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2346 // thread_is_available() checks whether the thread with threadID "slave" is
2347 // available to help the thread with threadID "master" at a split point. An
2348 // obvious requirement is that "slave" must be idle. With more than two
2349 // threads, this is not by itself sufficient: If "slave" is the master of
2350 // some active split point, it is only available as a slave to the other
2351 // threads which are busy searching the split point at the top of "slave"'s
2352 // split point stack (the "helpful master concept" in YBWC terminology).
2354 bool ThreadsManager::thread_is_available(int slave, int master) const {
2356 assert(slave >= 0 && slave < activeThreads);
2357 assert(master >= 0 && master < activeThreads);
2358 assert(activeThreads > 1);
2360 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2363 // Make a local copy to be sure doesn't change under our feet
2364 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2366 // No active split points means that the thread is available as
2367 // a slave for any other thread.
2368 if (localActiveSplitPoints == 0 || activeThreads == 2)
2371 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2372 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2373 // could have been set to 0 by another thread leading to an out of bound access.
2374 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2381 // available_thread_exists() tries to find an idle thread which is available as
2382 // a slave for the thread with threadID "master".
2384 bool ThreadsManager::available_thread_exists(int master) const {
2386 assert(master >= 0 && master < activeThreads);
2387 assert(activeThreads > 1);
2389 for (int i = 0; i < activeThreads; i++)
2390 if (thread_is_available(i, master))
2397 // split() does the actual work of distributing the work at a node between
2398 // several available threads. If it does not succeed in splitting the
2399 // node (because no idle threads are available, or because we have no unused
2400 // split point objects), the function immediately returns. If splitting is
2401 // possible, a SplitPoint object is initialized with all the data that must be
2402 // copied to the helper threads and we tell our helper threads that they have
2403 // been assigned work. This will cause them to instantly leave their idle loops and
2404 // call search().When all threads have returned from search() then split() returns.
2406 template <bool Fake>
2407 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2408 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2409 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2410 assert(pos.is_ok());
2411 assert(ply > 0 && ply < PLY_MAX);
2412 assert(*bestValue >= -VALUE_INFINITE);
2413 assert(*bestValue <= *alpha);
2414 assert(*alpha < beta);
2415 assert(beta <= VALUE_INFINITE);
2416 assert(depth > DEPTH_ZERO);
2417 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2418 assert(activeThreads > 1);
2420 int i, master = pos.thread();
2421 Thread& masterThread = threads[master];
2425 // If no other thread is available to help us, or if we have too many
2426 // active split points, don't split.
2427 if ( !available_thread_exists(master)
2428 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2430 lock_release(&mpLock);
2434 // Pick the next available split point object from the split point stack
2435 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2437 // Initialize the split point object
2438 splitPoint.parent = masterThread.splitPoint;
2439 splitPoint.master = master;
2440 splitPoint.betaCutoff = false;
2441 splitPoint.ply = ply;
2442 splitPoint.depth = depth;
2443 splitPoint.threatMove = threatMove;
2444 splitPoint.mateThreat = mateThreat;
2445 splitPoint.alpha = *alpha;
2446 splitPoint.beta = beta;
2447 splitPoint.pvNode = pvNode;
2448 splitPoint.bestValue = *bestValue;
2450 splitPoint.moveCount = moveCount;
2451 splitPoint.pos = &pos;
2452 splitPoint.nodes = 0;
2453 splitPoint.parentSstack = ss;
2454 for (i = 0; i < activeThreads; i++)
2455 splitPoint.slaves[i] = 0;
2457 masterThread.splitPoint = &splitPoint;
2459 // If we are here it means we are not available
2460 assert(masterThread.state != THREAD_AVAILABLE);
2462 int workersCnt = 1; // At least the master is included
2464 // Allocate available threads setting state to THREAD_BOOKED
2465 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2466 if (thread_is_available(i, master))
2468 threads[i].state = THREAD_BOOKED;
2469 threads[i].splitPoint = &splitPoint;
2470 splitPoint.slaves[i] = 1;
2474 assert(Fake || workersCnt > 1);
2476 // We can release the lock because slave threads are already booked and master is not available
2477 lock_release(&mpLock);
2479 // Tell the threads that they have work to do. This will make them leave
2480 // their idle loop. But before copy search stack tail for each thread.
2481 for (i = 0; i < activeThreads; i++)
2482 if (i == master || splitPoint.slaves[i])
2484 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2486 assert(i == master || threads[i].state == THREAD_BOOKED);
2488 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2490 if (useSleepingThreads && i != master)
2491 wake_sleeping_thread(i);
2494 // Everything is set up. The master thread enters the idle loop, from
2495 // which it will instantly launch a search, because its state is
2496 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2497 // idle loop, which means that the main thread will return from the idle
2498 // loop when all threads have finished their work at this split point.
2499 idle_loop(master, &splitPoint);
2501 // We have returned from the idle loop, which means that all threads are
2502 // finished. Update alpha and bestValue, and return.
2505 *alpha = splitPoint.alpha;
2506 *bestValue = splitPoint.bestValue;
2507 masterThread.activeSplitPoints--;
2508 masterThread.splitPoint = splitPoint.parent;
2509 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2511 lock_release(&mpLock);
2515 // wake_sleeping_thread() wakes up the thread with the given threadID
2516 // when it is time to start a new search.
2518 void ThreadsManager::wake_sleeping_thread(int threadID) {
2520 lock_grab(&sleepLock[threadID]);
2521 cond_signal(&sleepCond[threadID]);
2522 lock_release(&sleepLock[threadID]);
2526 /// RootMove and RootMoveList method's definitions
2528 RootMove::RootMove() {
2531 pv_score = non_pv_score = -VALUE_INFINITE;
2535 RootMove& RootMove::operator=(const RootMove& rm) {
2537 const Move* src = rm.pv;
2540 // Avoid a costly full rm.pv[] copy
2541 do *dst++ = *src; while (*src++ != MOVE_NONE);
2544 pv_score = rm.pv_score;
2545 non_pv_score = rm.non_pv_score;
2549 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2550 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2551 // allow to always have a ponder move even when we fail high at root and also a
2552 // long PV to print that is important for position analysis.
2554 void RootMove::extract_pv_from_tt(Position& pos) {
2556 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2560 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2562 pos.do_move(pv[0], *st++);
2564 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2565 && tte->move() != MOVE_NONE
2566 && move_is_legal(pos, tte->move())
2568 && (!pos.is_draw() || ply < 2))
2570 pv[ply] = tte->move();
2571 pos.do_move(pv[ply++], *st++);
2573 pv[ply] = MOVE_NONE;
2575 do pos.undo_move(pv[--ply]); while (ply);
2578 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2579 // the PV back into the TT. This makes sure the old PV moves are searched
2580 // first, even if the old TT entries have been overwritten.
2582 void RootMove::insert_pv_in_tt(Position& pos) {
2584 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2587 Value v, m = VALUE_NONE;
2590 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2594 tte = TT.retrieve(k);
2596 // Don't overwrite exsisting correct entries
2597 if (!tte || tte->move() != pv[ply])
2599 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2600 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2602 pos.do_move(pv[ply], *st++);
2604 } while (pv[++ply] != MOVE_NONE);
2606 do pos.undo_move(pv[--ply]); while (ply);
2609 // pv_info_to_uci() returns a string with information on the current PV line
2610 // formatted according to UCI specification and eventually writes the info
2611 // to a log file. It is called at each iteration or after a new pv is found.
2613 std::string RootMove::pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine) {
2615 std::stringstream s, l;
2618 while (*m != MOVE_NONE)
2621 s << "info depth " << Iteration // FIXME
2622 << " seldepth " << int(m - pv)
2623 << " multipv " << pvLine + 1
2624 << " score " << value_to_uci(pv_score)
2625 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2626 << " time " << current_search_time()
2627 << " nodes " << pos.nodes_searched()
2628 << " nps " << nps(pos)
2629 << " pv " << l.str();
2631 if (UseLogFile && pvLine == 0)
2633 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2634 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2636 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2642 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2644 SearchStack ss[PLY_MAX_PLUS_2];
2645 MoveStack mlist[MOVES_MAX];
2649 // Initialize search stack
2650 init_ss_array(ss, PLY_MAX_PLUS_2);
2651 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2653 // Generate all legal moves
2654 MoveStack* last = generate_moves(pos, mlist);
2656 // Add each move to the RootMoveList's vector
2657 for (MoveStack* cur = mlist; cur != last; cur++)
2659 // If we have a searchMoves[] list then verify cur->move
2660 // is in the list before to add it.
2661 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2663 if (searchMoves[0] && *sm != cur->move)
2666 // Find a quick score for the move and add to the list
2667 pos.do_move(cur->move, st);
2670 rm.pv[0] = ss[0].currentMove = cur->move;
2671 rm.pv[1] = MOVE_NONE;
2672 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2675 pos.undo_move(cur->move);
2680 // Score root moves using the standard way used in main search, the moves
2681 // are scored according to the order in which are returned by MovePicker.
2682 // This is the second order score that is used to compare the moves when
2683 // the first order pv scores of both moves are equal.
2685 void RootMoveList::set_non_pv_scores(const Position& pos)
2688 Value score = VALUE_ZERO;
2689 MovePicker mp(pos, MOVE_NONE, ONE_PLY, H);
2691 while ((move = mp.get_next_move()) != MOVE_NONE)
2692 for (Base::iterator it = begin(); it != end(); ++it)
2693 if (it->pv[0] == move)
2695 it->non_pv_score = score--;