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);
136 Move pv[PLY_MAX_PLUS_2];
140 // RootMoveList struct is essentially a std::vector<> of RootMove objects,
141 // with an handful of methods above the standard ones.
143 struct RootMoveList : public std::vector<RootMove> {
145 typedef std::vector<RootMove> Base;
147 RootMoveList(Position& pos, Move searchMoves[]);
148 void set_non_pv_scores(const Position& pos);
150 void sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
151 void sort_multipv(int n) { insertion_sort<RootMove, Base::iterator>(begin(), begin() + n); }
155 // When formatting a move for std::cout we must know if we are in Chess960
156 // or not. To keep using the handy operator<<() on the move the trick is to
157 // embed this flag in the stream itself. Function-like named enum set960 is
158 // used as a custom manipulator and the stream internal general-purpose array,
159 // accessed through ios_base::iword(), is used to pass the flag to the move's
160 // operator<<() that will use it to properly format castling moves.
163 std::ostream& operator<< (std::ostream& os, const set960& m) {
165 os.iword(0) = int(m);
174 // Maximum depth for razoring
175 const Depth RazorDepth = 4 * ONE_PLY;
177 // Dynamic razoring margin based on depth
178 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
180 // Maximum depth for use of dynamic threat detection when null move fails low
181 const Depth ThreatDepth = 5 * ONE_PLY;
183 // Step 9. Internal iterative deepening
185 // Minimum depth for use of internal iterative deepening
186 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
188 // At Non-PV nodes we do an internal iterative deepening search
189 // when the static evaluation is bigger then beta - IIDMargin.
190 const Value IIDMargin = Value(0x100);
192 // Step 11. Decide the new search depth
194 // Extensions. Configurable UCI options
195 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
196 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
197 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
199 // Minimum depth for use of singular extension
200 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
202 // If the TT move is at least SingularExtensionMargin better then the
203 // remaining ones we will extend it.
204 const Value SingularExtensionMargin = Value(0x20);
206 // Step 12. Futility pruning
208 // Futility margin for quiescence search
209 const Value FutilityMarginQS = Value(0x80);
211 // Futility lookup tables (initialized at startup) and their getter functions
212 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
213 int FutilityMoveCountArray[32]; // [depth]
215 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
216 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
218 // Step 14. Reduced search
220 // Reduction lookup tables (initialized at startup) and their getter functions
221 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
223 template <NodeType PV>
224 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
226 // Common adjustments
228 // Search depth at iteration 1
229 const Depth InitialDepth = ONE_PLY;
231 // Easy move margin. An easy move candidate must be at least this much
232 // better than the second best move.
233 const Value EasyMoveMargin = Value(0x200);
236 /// Namespace variables
244 // Scores and number of times the best move changed for each iteration
245 Value ValueByIteration[PLY_MAX_PLUS_2];
246 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
248 // Search window management
254 // Time managment variables
255 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
256 bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit;
257 bool FirstRootMove, AbortSearch, Quit, AspirationFailLow;
262 std::ofstream LogFile;
264 // Multi-threads manager object
265 ThreadsManager ThreadsMgr;
267 // Node counters, used only by thread[0] but try to keep in different cache
268 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
270 int NodesBetweenPolls = 30000;
277 Value id_loop(Position& pos, Move searchMoves[]);
278 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
280 template <NodeType PvNode, bool SpNode>
281 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
283 template <NodeType PvNode>
284 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
286 template <NodeType PvNode>
287 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
289 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
290 : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
293 template <NodeType PvNode>
294 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
296 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
297 bool connected_moves(const Position& pos, Move m1, Move m2);
298 bool value_is_mate(Value value);
299 Value value_to_tt(Value v, int ply);
300 Value value_from_tt(Value v, int ply);
301 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
302 bool connected_threat(const Position& pos, Move m, Move threat);
303 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
304 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
305 void update_killers(Move m, SearchStack* ss);
306 void update_gains(const Position& pos, Move move, Value before, Value after);
308 int current_search_time();
309 std::string value_to_uci(Value v);
310 int nps(const Position& pos);
311 void poll(const Position& pos);
313 void wait_for_stop_or_ponderhit();
314 void init_ss_array(SearchStack* ss, int size);
315 void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value);
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 = AbortSearch = Quit = AspirationFailLow = false;
406 SearchStartTime = get_system_time();
407 ExactMaxTime = maxTime;
410 InfiniteSearch = infinite;
411 PonderSearch = ponder;
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>();
455 LogFile.open(Options["Search Log Filename"].value<std::string>().c_str(), std::ios::out | std::ios::app);
457 read_weights(pos.side_to_move());
459 // Set the number of active threads
460 ThreadsMgr.read_uci_options();
461 init_eval(ThreadsMgr.active_threads());
463 // Wake up needed threads
464 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
465 ThreadsMgr.wake_sleeping_thread(i);
468 int myTime = time[pos.side_to_move()];
469 int myIncrement = increment[pos.side_to_move()];
470 if (UseTimeManagement)
471 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
473 // Set best NodesBetweenPolls interval to avoid lagging under
474 // heavy time pressure.
476 NodesBetweenPolls = Min(MaxNodes, 30000);
477 else if (myTime && myTime < 1000)
478 NodesBetweenPolls = 1000;
479 else if (myTime && myTime < 5000)
480 NodesBetweenPolls = 5000;
482 NodesBetweenPolls = 30000;
484 // Write search information to log file
486 LogFile << "Searching: " << pos.to_fen() << endl
487 << "infinite: " << infinite
488 << " ponder: " << ponder
489 << " time: " << myTime
490 << " increment: " << myIncrement
491 << " moves to go: " << movesToGo << endl;
493 // We're ready to start thinking. Call the iterative deepening loop function
494 id_loop(pos, searchMoves);
499 // This makes all the threads to go to sleep
500 ThreadsMgr.set_active_threads(1);
508 // id_loop() is the main iterative deepening loop. It calls root_search
509 // repeatedly with increasing depth until the allocated thinking time has
510 // been consumed, the user stops the search, or the maximum search depth is
513 Value id_loop(Position& pos, Move searchMoves[]) {
515 SearchStack ss[PLY_MAX_PLUS_2];
517 Move EasyMove = MOVE_NONE;
518 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
520 // Moves to search are verified, copied, scored and sorted
521 RootMoveList rml(pos, searchMoves);
523 // Handle special case of searching on a mate/stale position
527 wait_for_stop_or_ponderhit();
529 return pos.is_check() ? -VALUE_MATE : VALUE_DRAW;
532 // Print RootMoveList startup scoring to the standard output,
533 // so to output information also for iteration 1.
534 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
535 << "info depth " << 1
536 << "\ninfo depth " << 1
537 << " score " << value_to_uci(rml[0].pv_score)
538 << " time " << current_search_time()
539 << " nodes " << pos.nodes_searched()
540 << " nps " << nps(pos)
541 << " pv " << rml[0].pv[0] << "\n";
546 init_ss_array(ss, PLY_MAX_PLUS_2);
547 ValueByIteration[1] = rml[0].pv_score;
550 // Is one move significantly better than others after initial scoring ?
552 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
553 EasyMove = rml[0].pv[0];
555 // Iterative deepening loop
556 while (Iteration < PLY_MAX)
558 // Initialize iteration
560 BestMoveChangesByIteration[Iteration] = 0;
562 cout << "info depth " << Iteration << endl;
564 // Calculate dynamic aspiration window based on previous iterations
565 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
567 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
568 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
570 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
571 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
573 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
574 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
577 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
579 // Search to the current depth, rml is updated and sorted
580 value = root_search(pos, ss, alpha, beta, depth, rml);
583 break; // Value cannot be trusted. Break out immediately!
585 //Save info about search result
586 ValueByIteration[Iteration] = value;
588 // Drop the easy move if differs from the new best move
589 if (rml[0].pv[0] != EasyMove)
590 EasyMove = MOVE_NONE;
592 if (UseTimeManagement)
595 bool stopSearch = false;
597 // Stop search early if there is only a single legal move,
598 // we search up to Iteration 6 anyway to get a proper score.
599 if (Iteration >= 6 && rml.size() == 1)
602 // Stop search early when the last two iterations returned a mate score
604 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
605 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
608 // Stop search early if one move seems to be much better than the others
610 && EasyMove == rml[0].pv[0]
611 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
612 && current_search_time() > TimeMgr.available_time() / 16)
613 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
614 && current_search_time() > TimeMgr.available_time() / 32)))
617 // Add some extra time if the best move has changed during the last two iterations
618 if (Iteration > 5 && Iteration <= 50)
619 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
620 BestMoveChangesByIteration[Iteration-1]);
622 // Stop search if most of MaxSearchTime is consumed at the end of the
623 // iteration. We probably don't have enough time to search the first
624 // move at the next iteration anyway.
625 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
631 StopOnPonderhit = true;
637 if (MaxDepth && Iteration >= MaxDepth)
641 // If we are pondering or in infinite search, we shouldn't print the
642 // best move before we are told to do so.
643 if (!AbortSearch && (PonderSearch || InfiniteSearch))
644 wait_for_stop_or_ponderhit();
646 // Print final search statistics
647 cout << "info nodes " << pos.nodes_searched()
648 << " nps " << nps(pos)
649 << " time " << current_search_time() << endl;
651 // Print the best move and the ponder move to the standard output
652 cout << "bestmove " << rml[0].pv[0];
654 if (rml[0].pv[1] != MOVE_NONE)
655 cout << " ponder " << rml[0].pv[1];
662 dbg_print_mean(LogFile);
664 if (dbg_show_hit_rate)
665 dbg_print_hit_rate(LogFile);
667 LogFile << "\nNodes: " << pos.nodes_searched()
668 << "\nNodes/second: " << nps(pos)
669 << "\nBest move: " << move_to_san(pos, rml[0].pv[0]);
672 pos.do_move(rml[0].pv[0], st);
673 LogFile << "\nPonder move: "
674 << move_to_san(pos, rml[0].pv[1]) // Works also with MOVE_NONE
677 return rml[0].pv_score;
681 // root_search() is the function which searches the root node. It is
682 // similar to search_pv except that it prints some information to the
683 // standard output and handles the fail low/high loops.
685 Value root_search(Position& pos, SearchStack* ss, Value alpha,
686 Value beta, Depth depth, RootMoveList& rml) {
692 Value value, oldAlpha;
693 bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
694 int researchCountFH, researchCountFL;
696 researchCountFH = researchCountFL = 0;
698 isCheck = pos.is_check();
700 // Step 1. Initialize node (polling is omitted at root)
701 ss->currentMove = ss->bestMove = MOVE_NONE;
703 // Step 2. Check for aborted search (omitted at root)
704 // Step 3. Mate distance pruning (omitted at root)
705 // Step 4. Transposition table lookup (omitted at root)
707 // Step 5. Evaluate the position statically
708 // At root we do this only to get reference value for child nodes
709 ss->evalMargin = VALUE_NONE;
710 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
712 // Step 6. Razoring (omitted at root)
713 // Step 7. Static null move pruning (omitted at root)
714 // Step 8. Null move search with verification search (omitted at root)
715 // Step 9. Internal iterative deepening (omitted at root)
717 // Step extra. Fail low loop
718 // We start with small aspiration window and in case of fail low, we research
719 // with bigger window until we are not failing low anymore.
722 // Sort the moves before to (re)search
723 rml.set_non_pv_scores(pos);
726 // Step 10. Loop through all moves in the root move list
727 for (int i = 0; i < (int)rml.size() && !AbortSearch; i++)
729 // This is used by time management
730 FirstRootMove = (i == 0);
732 // Save the current node count before the move is searched
733 nodes = pos.nodes_searched();
735 // Pick the next root move, and print the move and the move number to
736 // the standard output.
737 move = ss->currentMove = rml[i].pv[0];
739 if (current_search_time() >= 1000)
740 cout << "info currmove " << move
741 << " currmovenumber " << i + 1 << endl;
743 moveIsCheck = pos.move_is_check(move);
744 captureOrPromotion = pos.move_is_capture_or_promotion(move);
746 // Step 11. Decide the new search depth
747 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
748 newDepth = depth + ext;
750 // Step 12. Futility pruning (omitted at root)
752 // Step extra. Fail high loop
753 // If move fails high, we research with bigger window until we are not failing
755 value = -VALUE_INFINITE;
759 // Step 13. Make the move
760 pos.do_move(move, st, ci, moveIsCheck);
762 // Step extra. pv search
763 // We do pv search for first moves (i < MultiPV)
764 // and for fail high research (value > alpha)
765 if (i < MultiPV || value > alpha)
767 // Aspiration window is disabled in multi-pv case
769 alpha = -VALUE_INFINITE;
771 // Full depth PV search, done on first move or after a fail high
772 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
776 // Step 14. Reduced search
777 // if the move fails high will be re-searched at full depth
778 bool doFullDepthSearch = true;
780 if ( depth >= 3 * ONE_PLY
782 && !captureOrPromotion
783 && !move_is_castle(move))
785 ss->reduction = reduction<PV>(depth, i - MultiPV + 2);
788 assert(newDepth-ss->reduction >= ONE_PLY);
790 // Reduced depth non-pv search using alpha as upperbound
791 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
792 doFullDepthSearch = (value > alpha);
794 ss->reduction = DEPTH_ZERO; // Restore original reduction
797 // Step 15. Full depth search
798 if (doFullDepthSearch)
800 // Full depth non-pv search using alpha as upperbound
801 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
803 // If we are above alpha then research at same depth but as PV
804 // to get a correct score or eventually a fail high above beta.
806 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
810 // Step 16. Undo move
813 // Can we exit fail high loop ?
814 if (AbortSearch || value < beta)
817 // We are failing high and going to do a research. It's important to update
818 // the score before research in case we run out of time while researching.
820 rml[i].pv_score = value;
821 rml[i].extract_pv_from_tt(pos);
823 // Print information to the standard output
824 print_pv_info(pos, rml[i].pv, alpha, beta, value);
826 // Prepare for a research after a fail high, each time with a wider window
827 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
830 } // End of fail high loop
832 // Finished searching the move. If AbortSearch is true, the search
833 // was aborted because the user interrupted the search or because we
834 // ran out of time. In this case, the return value of the search cannot
835 // be trusted, and we break out of the loop without updating the best
840 // Remember searched nodes counts for this move
841 rml[i].nodes += pos.nodes_searched() - nodes;
843 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
844 assert(value < beta);
846 // Step 17. Check for new best move
847 if (value <= alpha && i >= MultiPV)
848 rml[i].pv_score = -VALUE_INFINITE;
851 // PV move or new best move!
855 rml[i].pv_score = value;
856 rml[i].extract_pv_from_tt(pos);
860 // We record how often the best move has been changed in each
861 // iteration. This information is used for time managment: When
862 // the best move changes frequently, we allocate some more time.
864 BestMoveChangesByIteration[Iteration]++;
866 // Print information to the standard output
867 print_pv_info(pos, rml[i].pv, alpha, beta, value);
869 // Raise alpha to setup proper non-pv search upper bound
876 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
878 cout << "info multipv " << j + 1
879 << " score " << value_to_uci(rml[j].pv_score)
880 << " depth " << (j <= i ? Iteration : Iteration - 1)
881 << " time " << current_search_time()
882 << " nodes " << pos.nodes_searched()
883 << " nps " << nps(pos)
886 for (int k = 0; rml[j].pv[k] != MOVE_NONE && k < PLY_MAX; k++)
887 cout << rml[j].pv[k] << " ";
891 alpha = rml[Min(i, MultiPV - 1)].pv_score;
893 } // PV move or new best move
895 assert(alpha >= oldAlpha);
897 AspirationFailLow = (alpha == oldAlpha);
899 if (AspirationFailLow && StopOnPonderhit)
900 StopOnPonderhit = false;
903 // Can we exit fail low loop ?
904 if (AbortSearch || !AspirationFailLow)
907 // Prepare for a research after a fail low, each time with a wider window
908 oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
913 // Sort the moves before to return
916 // Write PV lines to transposition table, in case the relevant entries
917 // have been overwritten during the search.
918 for (int i = 0; i < MultiPV; i++)
919 rml[i].insert_pv_in_tt(pos);
925 // search<>() is the main search function for both PV and non-PV nodes and for
926 // normal and SplitPoint nodes. When called just after a split point the search
927 // is simpler because we have already probed the hash table, done a null move
928 // search, and searched the first move before splitting, we don't have to repeat
929 // all this work again. We also don't need to store anything to the hash table
930 // here: This is taken care of after we return from the split point.
932 template <NodeType PvNode, bool SpNode>
933 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
935 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
936 assert(beta > alpha && beta <= VALUE_INFINITE);
937 assert(PvNode || alpha == beta - 1);
938 assert(ply > 0 && ply < PLY_MAX);
939 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
941 Move movesSearched[MOVES_MAX];
945 Move ttMove, move, excludedMove, threatMove;
948 Value bestValue, value, oldAlpha;
949 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
950 bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
951 bool mateThreat = false;
953 int threadID = pos.thread();
954 SplitPoint* sp = NULL;
955 refinedValue = bestValue = value = -VALUE_INFINITE;
957 isCheck = pos.is_check();
963 ttMove = excludedMove = MOVE_NONE;
964 threatMove = sp->threatMove;
965 mateThreat = sp->mateThreat;
966 goto split_point_start;
968 else {} // Hack to fix icc's "statement is unreachable" warning
970 // Step 1. Initialize node and poll. Polling can abort search
971 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
972 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
974 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
980 // Step 2. Check for aborted search and immediate draw
982 || ThreadsMgr.cutoff_at_splitpoint(threadID)
984 || ply >= PLY_MAX - 1)
987 // Step 3. Mate distance pruning
988 alpha = Max(value_mated_in(ply), alpha);
989 beta = Min(value_mate_in(ply+1), beta);
993 // Step 4. Transposition table lookup
995 // We don't want the score of a partial search to overwrite a previous full search
996 // TT value, so we use a different position key in case of an excluded move exists.
997 excludedMove = ss->excludedMove;
998 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
1000 tte = TT.retrieve(posKey);
1001 ttMove = tte ? tte->move() : MOVE_NONE;
1003 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
1004 // This is to avoid problems in the following areas:
1006 // * Repetition draw detection
1007 // * Fifty move rule detection
1008 // * Searching for a mate
1009 // * Printing of full PV line
1010 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1013 ss->bestMove = ttMove; // Can be MOVE_NONE
1014 return value_from_tt(tte->value(), ply);
1017 // Step 5. Evaluate the position statically and
1018 // update gain statistics of parent move.
1020 ss->eval = ss->evalMargin = VALUE_NONE;
1023 assert(tte->static_value() != VALUE_NONE);
1025 ss->eval = tte->static_value();
1026 ss->evalMargin = tte->static_value_margin();
1027 refinedValue = refine_eval(tte, ss->eval, ply);
1031 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1032 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1035 // Save gain for the parent non-capture move
1036 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1038 // Step 6. Razoring (is omitted in PV nodes)
1040 && depth < RazorDepth
1042 && refinedValue < beta - razor_margin(depth)
1043 && ttMove == MOVE_NONE
1044 && !value_is_mate(beta)
1045 && !pos.has_pawn_on_7th(pos.side_to_move()))
1047 Value rbeta = beta - razor_margin(depth);
1048 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1050 // Logically we should return (v + razor_margin(depth)), but
1051 // surprisingly this did slightly weaker in tests.
1055 // Step 7. Static null move pruning (is omitted in PV nodes)
1056 // We're betting that the opponent doesn't have a move that will reduce
1057 // the score by more than futility_margin(depth) if we do a null move.
1059 && !ss->skipNullMove
1060 && depth < RazorDepth
1062 && refinedValue >= beta + futility_margin(depth, 0)
1063 && !value_is_mate(beta)
1064 && pos.non_pawn_material(pos.side_to_move()))
1065 return refinedValue - futility_margin(depth, 0);
1067 // Step 8. Null move search with verification search (is omitted in PV nodes)
1069 && !ss->skipNullMove
1072 && refinedValue >= beta
1073 && !value_is_mate(beta)
1074 && pos.non_pawn_material(pos.side_to_move()))
1076 ss->currentMove = MOVE_NULL;
1078 // Null move dynamic reduction based on depth
1079 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1081 // Null move dynamic reduction based on value
1082 if (refinedValue - beta > PawnValueMidgame)
1085 pos.do_null_move(st);
1086 (ss+1)->skipNullMove = true;
1087 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1088 (ss+1)->skipNullMove = false;
1089 pos.undo_null_move();
1091 if (nullValue >= beta)
1093 // Do not return unproven mate scores
1094 if (nullValue >= value_mate_in(PLY_MAX))
1097 if (depth < 6 * ONE_PLY)
1100 // Do verification search at high depths
1101 ss->skipNullMove = true;
1102 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1103 ss->skipNullMove = false;
1110 // The null move failed low, which means that we may be faced with
1111 // some kind of threat. If the previous move was reduced, check if
1112 // the move that refuted the null move was somehow connected to the
1113 // move which was reduced. If a connection is found, return a fail
1114 // low score (which will cause the reduced move to fail high in the
1115 // parent node, which will trigger a re-search with full depth).
1116 if (nullValue == value_mated_in(ply + 2))
1119 threatMove = (ss+1)->bestMove;
1120 if ( depth < ThreatDepth
1121 && (ss-1)->reduction
1122 && threatMove != MOVE_NONE
1123 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1128 // Step 9. Internal iterative deepening
1129 if ( depth >= IIDDepth[PvNode]
1130 && ttMove == MOVE_NONE
1131 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1133 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1135 ss->skipNullMove = true;
1136 search<PvNode>(pos, ss, alpha, beta, d, ply);
1137 ss->skipNullMove = false;
1139 ttMove = ss->bestMove;
1140 tte = TT.retrieve(posKey);
1143 // Expensive mate threat detection (only for PV nodes)
1145 mateThreat = pos.has_mate_threat();
1147 split_point_start: // At split points actual search starts from here
1149 // Initialize a MovePicker object for the current position
1150 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1151 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1152 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1154 ss->bestMove = MOVE_NONE;
1155 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1156 futilityBase = ss->eval + ss->evalMargin;
1157 singularExtensionNode = !SpNode
1158 && depth >= SingularExtensionDepth[PvNode]
1161 && !excludedMove // Do not allow recursive singular extension search
1162 && (tte->type() & VALUE_TYPE_LOWER)
1163 && tte->depth() >= depth - 3 * ONE_PLY;
1166 lock_grab(&(sp->lock));
1167 bestValue = sp->bestValue;
1170 // Step 10. Loop through moves
1171 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1172 while ( bestValue < beta
1173 && (move = mp.get_next_move()) != MOVE_NONE
1174 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1176 assert(move_is_ok(move));
1180 moveCount = ++sp->moveCount;
1181 lock_release(&(sp->lock));
1183 else if (move == excludedMove)
1186 movesSearched[moveCount++] = move;
1188 moveIsCheck = pos.move_is_check(move, ci);
1189 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1191 // Step 11. Decide the new search depth
1192 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1194 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1195 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1196 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1197 // lower then ttValue minus a margin then we extend ttMove.
1198 if ( singularExtensionNode
1199 && move == tte->move()
1202 Value ttValue = value_from_tt(tte->value(), ply);
1204 if (abs(ttValue) < VALUE_KNOWN_WIN)
1206 Value b = ttValue - SingularExtensionMargin;
1207 ss->excludedMove = move;
1208 ss->skipNullMove = true;
1209 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1210 ss->skipNullMove = false;
1211 ss->excludedMove = MOVE_NONE;
1212 ss->bestMove = MOVE_NONE;
1218 // Update current move (this must be done after singular extension search)
1219 ss->currentMove = move;
1220 newDepth = depth - ONE_PLY + ext;
1222 // Step 12. Futility pruning (is omitted in PV nodes)
1224 && !captureOrPromotion
1228 && !move_is_castle(move))
1230 // Move count based pruning
1231 if ( moveCount >= futility_move_count(depth)
1232 && !(threatMove && connected_threat(pos, move, threatMove))
1233 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1236 lock_grab(&(sp->lock));
1241 // Value based pruning
1242 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1243 // but fixing this made program slightly weaker.
1244 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1245 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1246 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1248 if (futilityValueScaled < beta)
1252 lock_grab(&(sp->lock));
1253 if (futilityValueScaled > sp->bestValue)
1254 sp->bestValue = bestValue = futilityValueScaled;
1256 else if (futilityValueScaled > bestValue)
1257 bestValue = futilityValueScaled;
1262 // Prune moves with negative SEE at low depths
1263 if ( predictedDepth < 2 * ONE_PLY
1264 && bestValue > value_mated_in(PLY_MAX)
1265 && pos.see_sign(move) < 0)
1268 lock_grab(&(sp->lock));
1274 // Step 13. Make the move
1275 pos.do_move(move, st, ci, moveIsCheck);
1277 // Step extra. pv search (only in PV nodes)
1278 // The first move in list is the expected PV
1279 if (PvNode && moveCount == 1)
1280 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1283 // Step 14. Reduced depth search
1284 // If the move fails high will be re-searched at full depth.
1285 bool doFullDepthSearch = true;
1287 if ( depth >= 3 * ONE_PLY
1288 && !captureOrPromotion
1290 && !move_is_castle(move)
1291 && ss->killers[0] != move
1292 && ss->killers[1] != move)
1294 ss->reduction = reduction<PvNode>(depth, moveCount);
1298 alpha = SpNode ? sp->alpha : alpha;
1299 Depth d = newDepth - ss->reduction;
1300 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1302 doFullDepthSearch = (value > alpha);
1304 ss->reduction = DEPTH_ZERO; // Restore original reduction
1307 // Step 15. Full depth search
1308 if (doFullDepthSearch)
1310 alpha = SpNode ? sp->alpha : alpha;
1311 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1313 // Step extra. pv search (only in PV nodes)
1314 // Search only for possible new PV nodes, if instead value >= beta then
1315 // parent node fails low with value <= alpha and tries another move.
1316 if (PvNode && value > alpha && value < beta)
1317 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1321 // Step 16. Undo move
1322 pos.undo_move(move);
1324 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1326 // Step 17. Check for new best move
1329 lock_grab(&(sp->lock));
1330 bestValue = sp->bestValue;
1334 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1339 sp->bestValue = value;
1343 if (PvNode && value < beta) // We want always alpha < beta
1351 sp->betaCutoff = true;
1353 if (value == value_mate_in(ply + 1))
1354 ss->mateKiller = move;
1356 ss->bestMove = move;
1359 sp->parentSstack->bestMove = move;
1363 // Step 18. Check for split
1365 && depth >= ThreadsMgr.min_split_depth()
1366 && ThreadsMgr.active_threads() > 1
1368 && ThreadsMgr.available_thread_exists(threadID)
1370 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1372 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1373 threatMove, mateThreat, moveCount, &mp, PvNode);
1376 // Step 19. Check for mate and stalemate
1377 // All legal moves have been searched and if there are
1378 // no legal moves, it must be mate or stalemate.
1379 // If one move was excluded return fail low score.
1380 if (!SpNode && !moveCount)
1381 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1383 // Step 20. Update tables
1384 // If the search is not aborted, update the transposition table,
1385 // history counters, and killer moves.
1386 if (!SpNode && !AbortSearch && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1388 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1389 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1390 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1392 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1394 // Update killers and history only for non capture moves that fails high
1395 if ( bestValue >= beta
1396 && !pos.move_is_capture_or_promotion(move))
1398 update_history(pos, move, depth, movesSearched, moveCount);
1399 update_killers(move, ss);
1405 // Here we have the lock still grabbed
1406 sp->slaves[threadID] = 0;
1407 sp->nodes += pos.nodes_searched();
1408 lock_release(&(sp->lock));
1411 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1416 // qsearch() is the quiescence search function, which is called by the main
1417 // search function when the remaining depth is zero (or, to be more precise,
1418 // less than ONE_PLY).
1420 template <NodeType PvNode>
1421 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1423 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1424 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1425 assert(PvNode || alpha == beta - 1);
1427 assert(ply > 0 && ply < PLY_MAX);
1428 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1432 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1433 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1436 Value oldAlpha = alpha;
1438 ss->bestMove = ss->currentMove = MOVE_NONE;
1440 // Check for an instant draw or maximum ply reached
1441 if (pos.is_draw() || ply >= PLY_MAX - 1)
1444 // Decide whether or not to include checks, this fixes also the type of
1445 // TT entry depth that we are going to use. Note that in qsearch we use
1446 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1447 isCheck = pos.is_check();
1448 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1450 // Transposition table lookup. At PV nodes, we don't use the TT for
1451 // pruning, but only for move ordering.
1452 tte = TT.retrieve(pos.get_key());
1453 ttMove = (tte ? tte->move() : MOVE_NONE);
1455 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1457 ss->bestMove = ttMove; // Can be MOVE_NONE
1458 return value_from_tt(tte->value(), ply);
1461 // Evaluate the position statically
1464 bestValue = futilityBase = -VALUE_INFINITE;
1465 ss->eval = evalMargin = VALUE_NONE;
1466 enoughMaterial = false;
1472 assert(tte->static_value() != VALUE_NONE);
1474 evalMargin = tte->static_value_margin();
1475 ss->eval = bestValue = tte->static_value();
1478 ss->eval = bestValue = evaluate(pos, evalMargin);
1480 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1482 // Stand pat. Return immediately if static value is at least beta
1483 if (bestValue >= beta)
1486 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1491 if (PvNode && bestValue > alpha)
1494 // Futility pruning parameters, not needed when in check
1495 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1496 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1499 // Initialize a MovePicker object for the current position, and prepare
1500 // to search the moves. Because the depth is <= 0 here, only captures,
1501 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1503 MovePicker mp(pos, ttMove, depth, H);
1506 // Loop through the moves until no moves remain or a beta cutoff occurs
1507 while ( alpha < beta
1508 && (move = mp.get_next_move()) != MOVE_NONE)
1510 assert(move_is_ok(move));
1512 moveIsCheck = pos.move_is_check(move, ci);
1520 && !move_is_promotion(move)
1521 && !pos.move_is_passed_pawn_push(move))
1523 futilityValue = futilityBase
1524 + pos.endgame_value_of_piece_on(move_to(move))
1525 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1527 if (futilityValue < alpha)
1529 if (futilityValue > bestValue)
1530 bestValue = futilityValue;
1535 // Detect non-capture evasions that are candidate to be pruned
1536 evasionPrunable = isCheck
1537 && bestValue > value_mated_in(PLY_MAX)
1538 && !pos.move_is_capture(move)
1539 && !pos.can_castle(pos.side_to_move());
1541 // Don't search moves with negative SEE values
1543 && (!isCheck || evasionPrunable)
1545 && !move_is_promotion(move)
1546 && pos.see_sign(move) < 0)
1549 // Don't search useless checks
1554 && !pos.move_is_capture_or_promotion(move)
1555 && ss->eval + PawnValueMidgame / 4 < beta
1556 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1558 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1559 bestValue = ss->eval + PawnValueMidgame / 4;
1564 // Update current move
1565 ss->currentMove = move;
1567 // Make and search the move
1568 pos.do_move(move, st, ci, moveIsCheck);
1569 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1570 pos.undo_move(move);
1572 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1575 if (value > bestValue)
1581 ss->bestMove = move;
1586 // All legal moves have been searched. A special case: If we're in check
1587 // and no legal moves were found, it is checkmate.
1588 if (isCheck && bestValue == -VALUE_INFINITE)
1589 return value_mated_in(ply);
1591 // Update transposition table
1592 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1593 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1595 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1601 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1602 // bestValue is updated only when returning false because in that case move
1605 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1607 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1608 Square from, to, ksq, victimSq;
1611 Value futilityValue, bv = *bestValue;
1613 from = move_from(move);
1615 them = opposite_color(pos.side_to_move());
1616 ksq = pos.king_square(them);
1617 kingAtt = pos.attacks_from<KING>(ksq);
1618 pc = pos.piece_on(from);
1620 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1621 oldAtt = pos.attacks_from(pc, from, occ);
1622 newAtt = pos.attacks_from(pc, to, occ);
1624 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1625 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1627 if (!(b && (b & (b - 1))))
1630 // Rule 2. Queen contact check is very dangerous
1631 if ( type_of_piece(pc) == QUEEN
1632 && bit_is_set(kingAtt, to))
1635 // Rule 3. Creating new double threats with checks
1636 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1640 victimSq = pop_1st_bit(&b);
1641 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1643 // Note that here we generate illegal "double move"!
1644 if ( futilityValue >= beta
1645 && pos.see_sign(make_move(from, victimSq)) >= 0)
1648 if (futilityValue > bv)
1652 // Update bestValue only if check is not dangerous (because we will prune the move)
1658 // connected_moves() tests whether two moves are 'connected' in the sense
1659 // that the first move somehow made the second move possible (for instance
1660 // if the moving piece is the same in both moves). The first move is assumed
1661 // to be the move that was made to reach the current position, while the
1662 // second move is assumed to be a move from the current position.
1664 bool connected_moves(const Position& pos, Move m1, Move m2) {
1666 Square f1, t1, f2, t2;
1669 assert(m1 && move_is_ok(m1));
1670 assert(m2 && move_is_ok(m2));
1672 // Case 1: The moving piece is the same in both moves
1678 // Case 2: The destination square for m2 was vacated by m1
1684 // Case 3: Moving through the vacated square
1685 if ( piece_is_slider(pos.piece_on(f2))
1686 && bit_is_set(squares_between(f2, t2), f1))
1689 // Case 4: The destination square for m2 is defended by the moving piece in m1
1690 p = pos.piece_on(t1);
1691 if (bit_is_set(pos.attacks_from(p, t1), t2))
1694 // Case 5: Discovered check, checking piece is the piece moved in m1
1695 if ( piece_is_slider(p)
1696 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1697 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1699 // discovered_check_candidates() works also if the Position's side to
1700 // move is the opposite of the checking piece.
1701 Color them = opposite_color(pos.side_to_move());
1702 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1704 if (bit_is_set(dcCandidates, f2))
1711 // value_is_mate() checks if the given value is a mate one eventually
1712 // compensated for the ply.
1714 bool value_is_mate(Value value) {
1716 assert(abs(value) <= VALUE_INFINITE);
1718 return value <= value_mated_in(PLY_MAX)
1719 || value >= value_mate_in(PLY_MAX);
1723 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1724 // "plies to mate from the current ply". Non-mate scores are unchanged.
1725 // The function is called before storing a value to the transposition table.
1727 Value value_to_tt(Value v, int ply) {
1729 if (v >= value_mate_in(PLY_MAX))
1732 if (v <= value_mated_in(PLY_MAX))
1739 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1740 // the transposition table to a mate score corrected for the current ply.
1742 Value value_from_tt(Value v, int ply) {
1744 if (v >= value_mate_in(PLY_MAX))
1747 if (v <= value_mated_in(PLY_MAX))
1754 // extension() decides whether a move should be searched with normal depth,
1755 // or with extended depth. Certain classes of moves (checking moves, in
1756 // particular) are searched with bigger depth than ordinary moves and in
1757 // any case are marked as 'dangerous'. Note that also if a move is not
1758 // extended, as example because the corresponding UCI option is set to zero,
1759 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1760 template <NodeType PvNode>
1761 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1762 bool singleEvasion, bool mateThreat, bool* dangerous) {
1764 assert(m != MOVE_NONE);
1766 Depth result = DEPTH_ZERO;
1767 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1771 if (moveIsCheck && pos.see_sign(m) >= 0)
1772 result += CheckExtension[PvNode];
1775 result += SingleEvasionExtension[PvNode];
1778 result += MateThreatExtension[PvNode];
1781 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1783 Color c = pos.side_to_move();
1784 if (relative_rank(c, move_to(m)) == RANK_7)
1786 result += PawnPushTo7thExtension[PvNode];
1789 if (pos.pawn_is_passed(c, move_to(m)))
1791 result += PassedPawnExtension[PvNode];
1796 if ( captureOrPromotion
1797 && pos.type_of_piece_on(move_to(m)) != PAWN
1798 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1799 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1800 && !move_is_promotion(m)
1803 result += PawnEndgameExtension[PvNode];
1808 && captureOrPromotion
1809 && pos.type_of_piece_on(move_to(m)) != PAWN
1810 && pos.see_sign(m) >= 0)
1812 result += ONE_PLY / 2;
1816 return Min(result, ONE_PLY);
1820 // connected_threat() tests whether it is safe to forward prune a move or if
1821 // is somehow coonected to the threat move returned by null search.
1823 bool connected_threat(const Position& pos, Move m, Move threat) {
1825 assert(move_is_ok(m));
1826 assert(threat && move_is_ok(threat));
1827 assert(!pos.move_is_check(m));
1828 assert(!pos.move_is_capture_or_promotion(m));
1829 assert(!pos.move_is_passed_pawn_push(m));
1831 Square mfrom, mto, tfrom, tto;
1833 mfrom = move_from(m);
1835 tfrom = move_from(threat);
1836 tto = move_to(threat);
1838 // Case 1: Don't prune moves which move the threatened piece
1842 // Case 2: If the threatened piece has value less than or equal to the
1843 // value of the threatening piece, don't prune move which defend it.
1844 if ( pos.move_is_capture(threat)
1845 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1846 || pos.type_of_piece_on(tfrom) == KING)
1847 && pos.move_attacks_square(m, tto))
1850 // Case 3: If the moving piece in the threatened move is a slider, don't
1851 // prune safe moves which block its ray.
1852 if ( piece_is_slider(pos.piece_on(tfrom))
1853 && bit_is_set(squares_between(tfrom, tto), mto)
1854 && pos.see_sign(m) >= 0)
1861 // ok_to_use_TT() returns true if a transposition table score
1862 // can be used at a given point in search.
1864 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1866 Value v = value_from_tt(tte->value(), ply);
1868 return ( tte->depth() >= depth
1869 || v >= Max(value_mate_in(PLY_MAX), beta)
1870 || v < Min(value_mated_in(PLY_MAX), beta))
1872 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1873 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1877 // refine_eval() returns the transposition table score if
1878 // possible otherwise falls back on static position evaluation.
1880 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1884 Value v = value_from_tt(tte->value(), ply);
1886 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1887 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1894 // update_history() registers a good move that produced a beta-cutoff
1895 // in history and marks as failures all the other moves of that ply.
1897 void update_history(const Position& pos, Move move, Depth depth,
1898 Move movesSearched[], int moveCount) {
1901 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
1903 for (int i = 0; i < moveCount - 1; i++)
1905 m = movesSearched[i];
1909 if (!pos.move_is_capture_or_promotion(m))
1910 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
1915 // update_killers() add a good move that produced a beta-cutoff
1916 // among the killer moves of that ply.
1918 void update_killers(Move m, SearchStack* ss) {
1920 if (m == ss->killers[0])
1923 ss->killers[1] = ss->killers[0];
1928 // update_gains() updates the gains table of a non-capture move given
1929 // the static position evaluation before and after the move.
1931 void update_gains(const Position& pos, Move m, Value before, Value after) {
1934 && before != VALUE_NONE
1935 && after != VALUE_NONE
1936 && pos.captured_piece_type() == PIECE_TYPE_NONE
1937 && !move_is_special(m))
1938 H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1942 // current_search_time() returns the number of milliseconds which have passed
1943 // since the beginning of the current search.
1945 int current_search_time() {
1947 return get_system_time() - SearchStartTime;
1951 // value_to_uci() converts a value to a string suitable for use with the UCI
1952 // protocol specifications:
1954 // cp <x> The score from the engine's point of view in centipawns.
1955 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1956 // use negative values for y.
1958 std::string value_to_uci(Value v) {
1960 std::stringstream s;
1962 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1963 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1965 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1970 // nps() computes the current nodes/second count.
1972 int nps(const Position& pos) {
1974 int t = current_search_time();
1975 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1979 // poll() performs two different functions: It polls for user input, and it
1980 // looks at the time consumed so far and decides if it's time to abort the
1983 void poll(const Position& pos) {
1985 static int lastInfoTime;
1986 int t = current_search_time();
1989 if (data_available())
1991 // We are line oriented, don't read single chars
1992 std::string command;
1994 if (!std::getline(std::cin, command))
1997 if (command == "quit")
2000 PonderSearch = false;
2004 else if (command == "stop")
2007 PonderSearch = false;
2009 else if (command == "ponderhit")
2013 // Print search information
2017 else if (lastInfoTime > t)
2018 // HACK: Must be a new search where we searched less than
2019 // NodesBetweenPolls nodes during the first second of search.
2022 else if (t - lastInfoTime >= 1000)
2029 if (dbg_show_hit_rate)
2030 dbg_print_hit_rate();
2032 cout << "info nodes " << pos.nodes_searched() << " nps " << nps(pos)
2033 << " time " << t << endl;
2036 // Should we stop the search?
2040 bool stillAtFirstMove = FirstRootMove
2041 && !AspirationFailLow
2042 && t > TimeMgr.available_time();
2044 bool noMoreTime = t > TimeMgr.maximum_time()
2045 || stillAtFirstMove;
2047 if ( (Iteration >= 3 && UseTimeManagement && noMoreTime)
2048 || (ExactMaxTime && t >= ExactMaxTime)
2049 || (Iteration >= 3 && MaxNodes && pos.nodes_searched() >= MaxNodes))
2054 // ponderhit() is called when the program is pondering (i.e. thinking while
2055 // it's the opponent's turn to move) in order to let the engine know that
2056 // it correctly predicted the opponent's move.
2060 int t = current_search_time();
2061 PonderSearch = false;
2063 bool stillAtFirstMove = FirstRootMove
2064 && !AspirationFailLow
2065 && t > TimeMgr.available_time();
2067 bool noMoreTime = t > TimeMgr.maximum_time()
2068 || stillAtFirstMove;
2070 if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit))
2075 // init_ss_array() does a fast reset of the first entries of a SearchStack
2076 // array and of all the excludedMove and skipNullMove entries.
2078 void init_ss_array(SearchStack* ss, int size) {
2080 for (int i = 0; i < size; i++, ss++)
2082 ss->excludedMove = MOVE_NONE;
2083 ss->skipNullMove = false;
2084 ss->reduction = DEPTH_ZERO;
2088 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
2093 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2094 // while the program is pondering. The point is to work around a wrinkle in
2095 // the UCI protocol: When pondering, the engine is not allowed to give a
2096 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2097 // We simply wait here until one of these commands is sent, and return,
2098 // after which the bestmove and pondermove will be printed (in id_loop()).
2100 void wait_for_stop_or_ponderhit() {
2102 std::string command;
2106 if (!std::getline(std::cin, command))
2109 if (command == "quit")
2114 else if (command == "ponderhit" || command == "stop")
2120 // print_pv_info() prints to standard output and eventually to log file information on
2121 // the current PV line. It is called at each iteration or after a new pv is found.
2123 void print_pv_info(const Position& pos, Move pv[], Value alpha, Value beta, Value value) {
2125 cout << "info depth " << Iteration
2126 << " score " << value_to_uci(value)
2127 << (value >= beta ? " lowerbound" : value <= alpha ? " upperbound" : "")
2128 << " time " << current_search_time()
2129 << " nodes " << pos.nodes_searched()
2130 << " nps " << nps(pos)
2133 for (Move* m = pv; *m != MOVE_NONE; m++)
2140 ValueType t = value >= beta ? VALUE_TYPE_LOWER :
2141 value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2143 LogFile << pretty_pv(pos, current_search_time(), Iteration, value, t, pv) << endl;
2148 // init_thread() is the function which is called when a new thread is
2149 // launched. It simply calls the idle_loop() function with the supplied
2150 // threadID. There are two versions of this function; one for POSIX
2151 // threads and one for Windows threads.
2153 #if !defined(_MSC_VER)
2155 void* init_thread(void* threadID) {
2157 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2163 DWORD WINAPI init_thread(LPVOID threadID) {
2165 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2172 /// The ThreadsManager class
2175 // read_uci_options() updates number of active threads and other internal
2176 // parameters according to the UCI options values. It is called before
2177 // to start a new search.
2179 void ThreadsManager::read_uci_options() {
2181 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2182 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2183 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2184 activeThreads = Options["Threads"].value<int>();
2188 // idle_loop() is where the threads are parked when they have no work to do.
2189 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2190 // object for which the current thread is the master.
2192 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2194 assert(threadID >= 0 && threadID < MAX_THREADS);
2197 bool allFinished = false;
2201 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2202 // master should exit as last one.
2203 if (allThreadsShouldExit)
2206 threads[threadID].state = THREAD_TERMINATED;
2210 // If we are not thinking, wait for a condition to be signaled
2211 // instead of wasting CPU time polling for work.
2212 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2213 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2215 assert(!sp || useSleepingThreads);
2216 assert(threadID != 0 || useSleepingThreads);
2218 if (threads[threadID].state == THREAD_INITIALIZING)
2219 threads[threadID].state = THREAD_AVAILABLE;
2221 // Grab the lock to avoid races with wake_sleeping_thread()
2222 lock_grab(&sleepLock[threadID]);
2224 // If we are master and all slaves have finished do not go to sleep
2225 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2226 allFinished = (i == activeThreads);
2228 if (allFinished || allThreadsShouldExit)
2230 lock_release(&sleepLock[threadID]);
2234 // Do sleep here after retesting sleep conditions
2235 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2236 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2238 lock_release(&sleepLock[threadID]);
2241 // If this thread has been assigned work, launch a search
2242 if (threads[threadID].state == THREAD_WORKISWAITING)
2244 assert(!allThreadsShouldExit);
2246 threads[threadID].state = THREAD_SEARCHING;
2248 // Here we call search() with SplitPoint template parameter set to true
2249 SplitPoint* tsp = threads[threadID].splitPoint;
2250 Position pos(*tsp->pos, threadID);
2251 SearchStack* ss = tsp->sstack[threadID] + 1;
2255 search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2257 search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2259 assert(threads[threadID].state == THREAD_SEARCHING);
2261 threads[threadID].state = THREAD_AVAILABLE;
2263 // Wake up master thread so to allow it to return from the idle loop in
2264 // case we are the last slave of the split point.
2265 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2266 wake_sleeping_thread(tsp->master);
2269 // If this thread is the master of a split point and all slaves have
2270 // finished their work at this split point, return from the idle loop.
2271 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2272 allFinished = (i == activeThreads);
2276 // Because sp->slaves[] is reset under lock protection,
2277 // be sure sp->lock has been released before to return.
2278 lock_grab(&(sp->lock));
2279 lock_release(&(sp->lock));
2281 // In helpful master concept a master can help only a sub-tree, and
2282 // because here is all finished is not possible master is booked.
2283 assert(threads[threadID].state == THREAD_AVAILABLE);
2285 threads[threadID].state = THREAD_SEARCHING;
2292 // init_threads() is called during startup. It launches all helper threads,
2293 // and initializes the split point stack and the global locks and condition
2296 void ThreadsManager::init_threads() {
2298 int i, arg[MAX_THREADS];
2301 // Initialize global locks
2304 for (i = 0; i < MAX_THREADS; i++)
2306 lock_init(&sleepLock[i]);
2307 cond_init(&sleepCond[i]);
2310 // Initialize splitPoints[] locks
2311 for (i = 0; i < MAX_THREADS; i++)
2312 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2313 lock_init(&(threads[i].splitPoints[j].lock));
2315 // Will be set just before program exits to properly end the threads
2316 allThreadsShouldExit = false;
2318 // Threads will be put all threads to sleep as soon as created
2321 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2322 threads[0].state = THREAD_SEARCHING;
2323 for (i = 1; i < MAX_THREADS; i++)
2324 threads[i].state = THREAD_INITIALIZING;
2326 // Launch the helper threads
2327 for (i = 1; i < MAX_THREADS; i++)
2331 #if !defined(_MSC_VER)
2332 pthread_t pthread[1];
2333 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2334 pthread_detach(pthread[0]);
2336 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2340 cout << "Failed to create thread number " << i << endl;
2344 // Wait until the thread has finished launching and is gone to sleep
2345 while (threads[i].state == THREAD_INITIALIZING) {}
2350 // exit_threads() is called when the program exits. It makes all the
2351 // helper threads exit cleanly.
2353 void ThreadsManager::exit_threads() {
2355 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2357 // Wake up all the threads and waits for termination
2358 for (int i = 1; i < MAX_THREADS; i++)
2360 wake_sleeping_thread(i);
2361 while (threads[i].state != THREAD_TERMINATED) {}
2364 // Now we can safely destroy the locks
2365 for (int i = 0; i < MAX_THREADS; i++)
2366 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2367 lock_destroy(&(threads[i].splitPoints[j].lock));
2369 lock_destroy(&mpLock);
2371 // Now we can safely destroy the wait conditions
2372 for (int i = 0; i < MAX_THREADS; i++)
2374 lock_destroy(&sleepLock[i]);
2375 cond_destroy(&sleepCond[i]);
2380 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2381 // the thread's currently active split point, or in some ancestor of
2382 // the current split point.
2384 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2386 assert(threadID >= 0 && threadID < activeThreads);
2388 SplitPoint* sp = threads[threadID].splitPoint;
2390 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2395 // thread_is_available() checks whether the thread with threadID "slave" is
2396 // available to help the thread with threadID "master" at a split point. An
2397 // obvious requirement is that "slave" must be idle. With more than two
2398 // threads, this is not by itself sufficient: If "slave" is the master of
2399 // some active split point, it is only available as a slave to the other
2400 // threads which are busy searching the split point at the top of "slave"'s
2401 // split point stack (the "helpful master concept" in YBWC terminology).
2403 bool ThreadsManager::thread_is_available(int slave, int master) const {
2405 assert(slave >= 0 && slave < activeThreads);
2406 assert(master >= 0 && master < activeThreads);
2407 assert(activeThreads > 1);
2409 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2412 // Make a local copy to be sure doesn't change under our feet
2413 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2415 // No active split points means that the thread is available as
2416 // a slave for any other thread.
2417 if (localActiveSplitPoints == 0 || activeThreads == 2)
2420 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2421 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2422 // could have been set to 0 by another thread leading to an out of bound access.
2423 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2430 // available_thread_exists() tries to find an idle thread which is available as
2431 // a slave for the thread with threadID "master".
2433 bool ThreadsManager::available_thread_exists(int master) const {
2435 assert(master >= 0 && master < activeThreads);
2436 assert(activeThreads > 1);
2438 for (int i = 0; i < activeThreads; i++)
2439 if (thread_is_available(i, master))
2446 // split() does the actual work of distributing the work at a node between
2447 // several available threads. If it does not succeed in splitting the
2448 // node (because no idle threads are available, or because we have no unused
2449 // split point objects), the function immediately returns. If splitting is
2450 // possible, a SplitPoint object is initialized with all the data that must be
2451 // copied to the helper threads and we tell our helper threads that they have
2452 // been assigned work. This will cause them to instantly leave their idle loops and
2453 // call search().When all threads have returned from search() then split() returns.
2455 template <bool Fake>
2456 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2457 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2458 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2459 assert(pos.is_ok());
2460 assert(ply > 0 && ply < PLY_MAX);
2461 assert(*bestValue >= -VALUE_INFINITE);
2462 assert(*bestValue <= *alpha);
2463 assert(*alpha < beta);
2464 assert(beta <= VALUE_INFINITE);
2465 assert(depth > DEPTH_ZERO);
2466 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2467 assert(activeThreads > 1);
2469 int i, master = pos.thread();
2470 Thread& masterThread = threads[master];
2474 // If no other thread is available to help us, or if we have too many
2475 // active split points, don't split.
2476 if ( !available_thread_exists(master)
2477 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2479 lock_release(&mpLock);
2483 // Pick the next available split point object from the split point stack
2484 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2486 // Initialize the split point object
2487 splitPoint.parent = masterThread.splitPoint;
2488 splitPoint.master = master;
2489 splitPoint.betaCutoff = false;
2490 splitPoint.ply = ply;
2491 splitPoint.depth = depth;
2492 splitPoint.threatMove = threatMove;
2493 splitPoint.mateThreat = mateThreat;
2494 splitPoint.alpha = *alpha;
2495 splitPoint.beta = beta;
2496 splitPoint.pvNode = pvNode;
2497 splitPoint.bestValue = *bestValue;
2499 splitPoint.moveCount = moveCount;
2500 splitPoint.pos = &pos;
2501 splitPoint.nodes = 0;
2502 splitPoint.parentSstack = ss;
2503 for (i = 0; i < activeThreads; i++)
2504 splitPoint.slaves[i] = 0;
2506 masterThread.splitPoint = &splitPoint;
2508 // If we are here it means we are not available
2509 assert(masterThread.state != THREAD_AVAILABLE);
2511 int workersCnt = 1; // At least the master is included
2513 // Allocate available threads setting state to THREAD_BOOKED
2514 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2515 if (thread_is_available(i, master))
2517 threads[i].state = THREAD_BOOKED;
2518 threads[i].splitPoint = &splitPoint;
2519 splitPoint.slaves[i] = 1;
2523 assert(Fake || workersCnt > 1);
2525 // We can release the lock because slave threads are already booked and master is not available
2526 lock_release(&mpLock);
2528 // Tell the threads that they have work to do. This will make them leave
2529 // their idle loop. But before copy search stack tail for each thread.
2530 for (i = 0; i < activeThreads; i++)
2531 if (i == master || splitPoint.slaves[i])
2533 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2535 assert(i == master || threads[i].state == THREAD_BOOKED);
2537 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2539 if (useSleepingThreads && i != master)
2540 wake_sleeping_thread(i);
2543 // Everything is set up. The master thread enters the idle loop, from
2544 // which it will instantly launch a search, because its state is
2545 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2546 // idle loop, which means that the main thread will return from the idle
2547 // loop when all threads have finished their work at this split point.
2548 idle_loop(master, &splitPoint);
2550 // We have returned from the idle loop, which means that all threads are
2551 // finished. Update alpha and bestValue, and return.
2554 *alpha = splitPoint.alpha;
2555 *bestValue = splitPoint.bestValue;
2556 masterThread.activeSplitPoints--;
2557 masterThread.splitPoint = splitPoint.parent;
2558 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2560 lock_release(&mpLock);
2564 // wake_sleeping_thread() wakes up the thread with the given threadID
2565 // when it is time to start a new search.
2567 void ThreadsManager::wake_sleeping_thread(int threadID) {
2569 lock_grab(&sleepLock[threadID]);
2570 cond_signal(&sleepCond[threadID]);
2571 lock_release(&sleepLock[threadID]);
2575 /// RootMove and RootMoveList method's definitions
2577 RootMove::RootMove() {
2580 pv_score = non_pv_score = -VALUE_INFINITE;
2584 RootMove& RootMove::operator=(const RootMove& rm) {
2586 const Move* src = rm.pv;
2589 // Avoid a costly full rm.pv[] copy
2590 do *dst++ = *src; while (*src++ != MOVE_NONE);
2593 pv_score = rm.pv_score;
2594 non_pv_score = rm.non_pv_score;
2598 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2599 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2600 // allow to always have a ponder move even when we fail high at root and also a
2601 // long PV to print that is important for position analysis.
2603 void RootMove::extract_pv_from_tt(Position& pos) {
2605 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2609 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2611 pos.do_move(pv[0], *st++);
2613 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2614 && tte->move() != MOVE_NONE
2615 && move_is_legal(pos, tte->move())
2617 && (!pos.is_draw() || ply < 2))
2619 pv[ply] = tte->move();
2620 pos.do_move(pv[ply++], *st++);
2622 pv[ply] = MOVE_NONE;
2624 do pos.undo_move(pv[--ply]); while (ply);
2627 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2628 // the PV back into the TT. This makes sure the old PV moves are searched
2629 // first, even if the old TT entries have been overwritten.
2631 void RootMove::insert_pv_in_tt(Position& pos) {
2633 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2636 Value v, m = VALUE_NONE;
2639 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2643 tte = TT.retrieve(k);
2645 // Don't overwrite exsisting correct entries
2646 if (!tte || tte->move() != pv[ply])
2648 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2649 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2651 pos.do_move(pv[ply], *st++);
2653 } while (pv[++ply] != MOVE_NONE);
2655 do pos.undo_move(pv[--ply]); while (ply);
2659 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2661 SearchStack ss[PLY_MAX_PLUS_2];
2662 MoveStack mlist[MOVES_MAX];
2666 // Initialize search stack
2667 init_ss_array(ss, PLY_MAX_PLUS_2);
2668 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2670 // Generate all legal moves
2671 MoveStack* last = generate_moves(pos, mlist);
2673 // Add each move to the RootMoveList's vector
2674 for (MoveStack* cur = mlist; cur != last; cur++)
2676 // If we have a searchMoves[] list then verify cur->move
2677 // is in the list before to add it.
2678 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2680 if (searchMoves[0] && *sm != cur->move)
2683 // Find a quick score for the move and add to the list
2684 pos.do_move(cur->move, st);
2687 rm.pv[0] = ss[0].currentMove = cur->move;
2688 rm.pv[1] = MOVE_NONE;
2689 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2692 pos.undo_move(cur->move);
2697 // Score root moves using the standard way used in main search, the moves
2698 // are scored according to the order in which are returned by MovePicker.
2699 // This is the second order score that is used to compare the moves when
2700 // the first order pv scores of both moves are equal.
2702 void RootMoveList::set_non_pv_scores(const Position& pos)
2705 Value score = VALUE_ZERO;
2706 MovePicker mp(pos, MOVE_NONE, ONE_PLY, H);
2708 while ((move = mp.get_next_move()) != MOVE_NONE)
2709 for (Base::iterator it = begin(); it != end(); ++it)
2710 if (it->pv[0] == move)
2712 it->non_pv_score = score--;