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); }
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, PonderSearch, StopOnPonderhit;
258 bool FirstRootMove, AbortSearch, Quit, 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.
271 int NodesBetweenPolls = 30000;
278 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
279 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
281 template <NodeType PvNode, bool SpNode>
282 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
284 template <NodeType PvNode>
285 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
287 template <NodeType PvNode>
288 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
290 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
291 : search<PvNode, false>(pos, ss, alpha, beta, depth, ply);
294 template <NodeType PvNode>
295 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
297 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
298 bool connected_moves(const Position& pos, Move m1, Move m2);
299 bool value_is_mate(Value value);
300 Value value_to_tt(Value v, int ply);
301 Value value_from_tt(Value v, int ply);
302 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
303 bool connected_threat(const Position& pos, Move m, Move threat);
304 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
305 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
306 void update_killers(Move m, SearchStack* ss);
307 void update_gains(const Position& pos, Move move, Value before, Value after);
309 int current_search_time();
310 std::string value_to_uci(Value v);
311 int nps(const Position& pos);
312 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 = 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 Move ponderMove = MOVE_NONE;
495 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
497 // Print final search statistics
498 cout << "info nodes " << pos.nodes_searched()
499 << " nps " << nps(pos)
500 << " time " << current_search_time() << endl;
502 // If we are pondering or in infinite search, we shouldn't print the
503 // best move before we are told to do so.
504 if (!AbortSearch && (PonderSearch || InfiniteSearch))
505 wait_for_stop_or_ponderhit();
507 // Could be both MOVE_NONE when searching on a stalemate position
508 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
513 dbg_print_mean(LogFile);
515 if (dbg_show_hit_rate)
516 dbg_print_hit_rate(LogFile);
518 LogFile << "\nNodes: " << pos.nodes_searched()
519 << "\nNodes/second: " << nps(pos)
520 << "\nBest move: " << move_to_san(pos, bestMove);
523 pos.do_move(bestMove, st);
524 LogFile << "\nPonder move: "
525 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
532 // This makes all the threads to go to sleep
533 ThreadsMgr.set_active_threads(1);
541 // id_loop() is the main iterative deepening loop. It calls root_search
542 // repeatedly with increasing depth until the allocated thinking time has
543 // been consumed, the user stops the search, or the maximum search depth is
546 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
548 SearchStack ss[PLY_MAX_PLUS_2];
550 Move EasyMove = MOVE_NONE;
551 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
553 // Moves to search are verified, scored and sorted
554 RootMoveList rml(pos, searchMoves);
556 // Handle special case of searching on a mate/stale position
559 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
561 cout << "info depth " << 1
562 << " score " << value_to_uci(s) << endl;
570 init_ss_array(ss, PLY_MAX_PLUS_2);
571 ValueByIteration[1] = rml[0].pv_score;
574 // Send initial RootMoveList scoring (iteration 1)
575 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
576 << "info depth " << Iteration
577 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
579 // Is one move significantly better than others after initial scoring ?
581 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
582 EasyMove = rml[0].pv[0];
584 // Iterative deepening loop
585 while (Iteration < PLY_MAX)
587 // Initialize iteration
589 BestMoveChangesByIteration[Iteration] = 0;
591 cout << "info depth " << Iteration << endl;
593 // Calculate dynamic aspiration window based on previous iterations
594 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
596 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
597 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
599 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
600 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
602 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
603 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
606 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
608 // Search to the current depth, rml is updated and sorted
609 value = root_search(pos, ss, alpha, beta, depth, rml);
612 break; // Value cannot be trusted. Break out immediately!
614 //Save info about search result
615 ValueByIteration[Iteration] = value;
617 // Drop the easy move if differs from the new best move
618 if (rml[0].pv[0] != EasyMove)
619 EasyMove = MOVE_NONE;
621 if (UseTimeManagement)
624 bool stopSearch = false;
626 // Stop search early if there is only a single legal move,
627 // we search up to Iteration 6 anyway to get a proper score.
628 if (Iteration >= 6 && rml.size() == 1)
631 // Stop search early when the last two iterations returned a mate score
633 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
634 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
637 // Stop search early if one move seems to be much better than the others
639 && EasyMove == rml[0].pv[0]
640 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
641 && current_search_time() > TimeMgr.available_time() / 16)
642 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
643 && current_search_time() > TimeMgr.available_time() / 32)))
646 // Add some extra time if the best move has changed during the last two iterations
647 if (Iteration > 5 && Iteration <= 50)
648 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
649 BestMoveChangesByIteration[Iteration-1]);
651 // Stop search if most of MaxSearchTime is consumed at the end of the
652 // iteration. We probably don't have enough time to search the first
653 // move at the next iteration anyway.
654 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
660 StopOnPonderhit = true;
666 if (MaxDepth && Iteration >= MaxDepth)
670 *ponderMove = rml[0].pv[1];
675 // root_search() is the function which searches the root node. It is
676 // similar to search_pv except that it prints some information to the
677 // standard output and handles the fail low/high loops.
679 Value root_search(Position& pos, SearchStack* ss, Value alpha,
680 Value beta, Depth depth, RootMoveList& rml) {
686 Value value, oldAlpha;
687 bool isCheck, moveIsCheck, captureOrPromotion, dangerous;
688 int researchCountFH, researchCountFL;
690 researchCountFH = researchCountFL = 0;
692 isCheck = pos.is_check();
694 // Step 1. Initialize node (polling is omitted at root)
695 ss->currentMove = ss->bestMove = MOVE_NONE;
697 // Step 2. Check for aborted search (omitted at root)
698 // Step 3. Mate distance pruning (omitted at root)
699 // Step 4. Transposition table lookup (omitted at root)
701 // Step 5. Evaluate the position statically
702 // At root we do this only to get reference value for child nodes
703 ss->evalMargin = VALUE_NONE;
704 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
706 // Step 6. Razoring (omitted at root)
707 // Step 7. Static null move pruning (omitted at root)
708 // Step 8. Null move search with verification search (omitted at root)
709 // Step 9. Internal iterative deepening (omitted at root)
711 // Step extra. Fail low loop
712 // We start with small aspiration window and in case of fail low, we research
713 // with bigger window until we are not failing low anymore.
716 // Sort the moves before to (re)search
717 rml.set_non_pv_scores(pos);
720 // Step 10. Loop through all moves in the root move list
721 for (int i = 0; i < (int)rml.size() && !AbortSearch; i++)
723 // This is used by time management
724 FirstRootMove = (i == 0);
726 // Save the current node count before the move is searched
727 nodes = pos.nodes_searched();
729 // Pick the next root move, and print the move and the move number to
730 // the standard output.
731 move = ss->currentMove = rml[i].pv[0];
733 if (current_search_time() >= 1000)
734 cout << "info currmove " << move
735 << " currmovenumber " << i + 1 << endl;
737 moveIsCheck = pos.move_is_check(move);
738 captureOrPromotion = pos.move_is_capture_or_promotion(move);
740 // Step 11. Decide the new search depth
741 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
742 newDepth = depth + ext;
744 // Step 12. Futility pruning (omitted at root)
746 // Step extra. Fail high loop
747 // If move fails high, we research with bigger window until we are not failing
749 value = -VALUE_INFINITE;
753 // Step 13. Make the move
754 pos.do_move(move, st, ci, moveIsCheck);
756 // Step extra. pv search
757 // We do pv search for first moves (i < MultiPV)
758 // and for fail high research (value > alpha)
759 if (i < MultiPV || value > alpha)
761 // Aspiration window is disabled in multi-pv case
763 alpha = -VALUE_INFINITE;
765 // Full depth PV search, done on first move or after a fail high
766 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
770 // Step 14. Reduced search
771 // if the move fails high will be re-searched at full depth
772 bool doFullDepthSearch = true;
774 if ( depth >= 3 * ONE_PLY
776 && !captureOrPromotion
777 && !move_is_castle(move))
779 ss->reduction = reduction<PV>(depth, i - MultiPV + 2);
782 assert(newDepth-ss->reduction >= ONE_PLY);
784 // Reduced depth non-pv search using alpha as upperbound
785 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth-ss->reduction, 1);
786 doFullDepthSearch = (value > alpha);
788 ss->reduction = DEPTH_ZERO; // Restore original reduction
791 // Step 15. Full depth search
792 if (doFullDepthSearch)
794 // Full depth non-pv search using alpha as upperbound
795 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
797 // If we are above alpha then research at same depth but as PV
798 // to get a correct score or eventually a fail high above beta.
800 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
804 // Step 16. Undo move
807 // Can we exit fail high loop ?
808 if (AbortSearch || value < beta)
811 // We are failing high and going to do a research. It's important to update
812 // the score before research in case we run out of time while researching.
814 rml[i].pv_score = value;
815 rml[i].extract_pv_from_tt(pos);
817 // Inform GUI that PV has changed
818 cout << rml[i].pv_info_to_uci(pos, alpha, beta) << endl;
820 // Prepare for a research after a fail high, each time with a wider window
821 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
824 } // End of fail high loop
826 // Finished searching the move. If AbortSearch is true, the search
827 // was aborted because the user interrupted the search or because we
828 // ran out of time. In this case, the return value of the search cannot
829 // be trusted, and we break out of the loop without updating the best
834 // Remember searched nodes counts for this move
835 rml[i].nodes += pos.nodes_searched() - nodes;
837 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
838 assert(value < beta);
840 // Step 17. Check for new best move
841 if (value <= alpha && i >= MultiPV)
842 rml[i].pv_score = -VALUE_INFINITE;
845 // PV move or new best move!
849 rml[i].pv_score = value;
850 rml[i].extract_pv_from_tt(pos);
852 // We record how often the best move has been changed in each
853 // iteration. This information is used for time managment: When
854 // the best move changes frequently, we allocate some more time.
855 if (MultiPV == 1 && i > 0)
856 BestMoveChangesByIteration[Iteration]++;
858 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
859 // requires we send all the PV lines properly sorted.
862 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
863 cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
865 // Update alpha. In multi-pv we don't use aspiration window
868 // Raise alpha to setup proper non-pv search upper bound
872 else // Set alpha equal to minimum score among the PV lines
873 alpha = rml[Min(i, MultiPV - 1)].pv_score;
875 } // PV move or new best move
877 assert(alpha >= oldAlpha);
879 AspirationFailLow = (alpha == oldAlpha);
881 if (AspirationFailLow && StopOnPonderhit)
882 StopOnPonderhit = false;
886 // Can we exit fail low loop ?
887 if (AbortSearch || !AspirationFailLow)
890 // Prepare for a research after a fail low, each time with a wider window
891 oldAlpha = alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
896 // Sort the moves before to return
899 // Write PV lines to transposition table, in case the relevant entries
900 // have been overwritten during the search.
901 for (int i = 0; i < MultiPV; i++)
902 rml[i].insert_pv_in_tt(pos);
908 // search<>() is the main search function for both PV and non-PV nodes and for
909 // normal and SplitPoint nodes. When called just after a split point the search
910 // is simpler because we have already probed the hash table, done a null move
911 // search, and searched the first move before splitting, we don't have to repeat
912 // all this work again. We also don't need to store anything to the hash table
913 // here: This is taken care of after we return from the split point.
915 template <NodeType PvNode, bool SpNode>
916 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
918 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
919 assert(beta > alpha && beta <= VALUE_INFINITE);
920 assert(PvNode || alpha == beta - 1);
921 assert(ply > 0 && ply < PLY_MAX);
922 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
924 Move movesSearched[MOVES_MAX];
928 Move ttMove, move, excludedMove, threatMove;
931 Value bestValue, value, oldAlpha;
932 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
933 bool isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
934 bool mateThreat = false;
936 int threadID = pos.thread();
937 SplitPoint* sp = NULL;
938 refinedValue = bestValue = value = -VALUE_INFINITE;
940 isCheck = pos.is_check();
946 ttMove = excludedMove = MOVE_NONE;
947 threatMove = sp->threatMove;
948 mateThreat = sp->mateThreat;
949 goto split_point_start;
951 else {} // Hack to fix icc's "statement is unreachable" warning
953 // Step 1. Initialize node and poll. Polling can abort search
954 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
955 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
957 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
963 // Step 2. Check for aborted search and immediate draw
965 || ThreadsMgr.cutoff_at_splitpoint(threadID)
967 || ply >= PLY_MAX - 1)
970 // Step 3. Mate distance pruning
971 alpha = Max(value_mated_in(ply), alpha);
972 beta = Min(value_mate_in(ply+1), beta);
976 // Step 4. Transposition table lookup
978 // We don't want the score of a partial search to overwrite a previous full search
979 // TT value, so we use a different position key in case of an excluded move exists.
980 excludedMove = ss->excludedMove;
981 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
983 tte = TT.retrieve(posKey);
984 ttMove = tte ? tte->move() : MOVE_NONE;
986 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
987 // This is to avoid problems in the following areas:
989 // * Repetition draw detection
990 // * Fifty move rule detection
991 // * Searching for a mate
992 // * Printing of full PV line
993 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
996 ss->bestMove = ttMove; // Can be MOVE_NONE
997 return value_from_tt(tte->value(), ply);
1000 // Step 5. Evaluate the position statically and
1001 // update gain statistics of parent move.
1003 ss->eval = ss->evalMargin = VALUE_NONE;
1006 assert(tte->static_value() != VALUE_NONE);
1008 ss->eval = tte->static_value();
1009 ss->evalMargin = tte->static_value_margin();
1010 refinedValue = refine_eval(tte, ss->eval, ply);
1014 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1015 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1018 // Save gain for the parent non-capture move
1019 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1021 // Step 6. Razoring (is omitted in PV nodes)
1023 && depth < RazorDepth
1025 && refinedValue < beta - razor_margin(depth)
1026 && ttMove == MOVE_NONE
1027 && !value_is_mate(beta)
1028 && !pos.has_pawn_on_7th(pos.side_to_move()))
1030 Value rbeta = beta - razor_margin(depth);
1031 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1033 // Logically we should return (v + razor_margin(depth)), but
1034 // surprisingly this did slightly weaker in tests.
1038 // Step 7. Static null move pruning (is omitted in PV nodes)
1039 // We're betting that the opponent doesn't have a move that will reduce
1040 // the score by more than futility_margin(depth) if we do a null move.
1042 && !ss->skipNullMove
1043 && depth < RazorDepth
1045 && refinedValue >= beta + futility_margin(depth, 0)
1046 && !value_is_mate(beta)
1047 && pos.non_pawn_material(pos.side_to_move()))
1048 return refinedValue - futility_margin(depth, 0);
1050 // Step 8. Null move search with verification search (is omitted in PV nodes)
1052 && !ss->skipNullMove
1055 && refinedValue >= beta
1056 && !value_is_mate(beta)
1057 && pos.non_pawn_material(pos.side_to_move()))
1059 ss->currentMove = MOVE_NULL;
1061 // Null move dynamic reduction based on depth
1062 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1064 // Null move dynamic reduction based on value
1065 if (refinedValue - beta > PawnValueMidgame)
1068 pos.do_null_move(st);
1069 (ss+1)->skipNullMove = true;
1070 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1071 (ss+1)->skipNullMove = false;
1072 pos.undo_null_move();
1074 if (nullValue >= beta)
1076 // Do not return unproven mate scores
1077 if (nullValue >= value_mate_in(PLY_MAX))
1080 if (depth < 6 * ONE_PLY)
1083 // Do verification search at high depths
1084 ss->skipNullMove = true;
1085 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1086 ss->skipNullMove = false;
1093 // The null move failed low, which means that we may be faced with
1094 // some kind of threat. If the previous move was reduced, check if
1095 // the move that refuted the null move was somehow connected to the
1096 // move which was reduced. If a connection is found, return a fail
1097 // low score (which will cause the reduced move to fail high in the
1098 // parent node, which will trigger a re-search with full depth).
1099 if (nullValue == value_mated_in(ply + 2))
1102 threatMove = (ss+1)->bestMove;
1103 if ( depth < ThreatDepth
1104 && (ss-1)->reduction
1105 && threatMove != MOVE_NONE
1106 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1111 // Step 9. Internal iterative deepening
1112 if ( depth >= IIDDepth[PvNode]
1113 && ttMove == MOVE_NONE
1114 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1116 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1118 ss->skipNullMove = true;
1119 search<PvNode>(pos, ss, alpha, beta, d, ply);
1120 ss->skipNullMove = false;
1122 ttMove = ss->bestMove;
1123 tte = TT.retrieve(posKey);
1126 // Expensive mate threat detection (only for PV nodes)
1128 mateThreat = pos.has_mate_threat();
1130 split_point_start: // At split points actual search starts from here
1132 // Initialize a MovePicker object for the current position
1133 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1134 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1135 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1137 ss->bestMove = MOVE_NONE;
1138 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1139 futilityBase = ss->eval + ss->evalMargin;
1140 singularExtensionNode = !SpNode
1141 && depth >= SingularExtensionDepth[PvNode]
1144 && !excludedMove // Do not allow recursive singular extension search
1145 && (tte->type() & VALUE_TYPE_LOWER)
1146 && tte->depth() >= depth - 3 * ONE_PLY;
1149 lock_grab(&(sp->lock));
1150 bestValue = sp->bestValue;
1153 // Step 10. Loop through moves
1154 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1155 while ( bestValue < beta
1156 && (move = mp.get_next_move()) != MOVE_NONE
1157 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1159 assert(move_is_ok(move));
1163 moveCount = ++sp->moveCount;
1164 lock_release(&(sp->lock));
1166 else if (move == excludedMove)
1169 movesSearched[moveCount++] = move;
1171 moveIsCheck = pos.move_is_check(move, ci);
1172 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1174 // Step 11. Decide the new search depth
1175 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1177 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1178 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1179 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1180 // lower then ttValue minus a margin then we extend ttMove.
1181 if ( singularExtensionNode
1182 && move == tte->move()
1185 Value ttValue = value_from_tt(tte->value(), ply);
1187 if (abs(ttValue) < VALUE_KNOWN_WIN)
1189 Value b = ttValue - SingularExtensionMargin;
1190 ss->excludedMove = move;
1191 ss->skipNullMove = true;
1192 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1193 ss->skipNullMove = false;
1194 ss->excludedMove = MOVE_NONE;
1195 ss->bestMove = MOVE_NONE;
1201 // Update current move (this must be done after singular extension search)
1202 ss->currentMove = move;
1203 newDepth = depth - ONE_PLY + ext;
1205 // Step 12. Futility pruning (is omitted in PV nodes)
1207 && !captureOrPromotion
1211 && !move_is_castle(move))
1213 // Move count based pruning
1214 if ( moveCount >= futility_move_count(depth)
1215 && !(threatMove && connected_threat(pos, move, threatMove))
1216 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1219 lock_grab(&(sp->lock));
1224 // Value based pruning
1225 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1226 // but fixing this made program slightly weaker.
1227 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1228 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1229 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1231 if (futilityValueScaled < beta)
1235 lock_grab(&(sp->lock));
1236 if (futilityValueScaled > sp->bestValue)
1237 sp->bestValue = bestValue = futilityValueScaled;
1239 else if (futilityValueScaled > bestValue)
1240 bestValue = futilityValueScaled;
1245 // Prune moves with negative SEE at low depths
1246 if ( predictedDepth < 2 * ONE_PLY
1247 && bestValue > value_mated_in(PLY_MAX)
1248 && pos.see_sign(move) < 0)
1251 lock_grab(&(sp->lock));
1257 // Step 13. Make the move
1258 pos.do_move(move, st, ci, moveIsCheck);
1260 // Step extra. pv search (only in PV nodes)
1261 // The first move in list is the expected PV
1262 if (PvNode && moveCount == 1)
1263 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1266 // Step 14. Reduced depth search
1267 // If the move fails high will be re-searched at full depth.
1268 bool doFullDepthSearch = true;
1270 if ( depth >= 3 * ONE_PLY
1271 && !captureOrPromotion
1273 && !move_is_castle(move)
1274 && ss->killers[0] != move
1275 && ss->killers[1] != move)
1277 ss->reduction = reduction<PvNode>(depth, moveCount);
1281 alpha = SpNode ? sp->alpha : alpha;
1282 Depth d = newDepth - ss->reduction;
1283 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1285 doFullDepthSearch = (value > alpha);
1287 ss->reduction = DEPTH_ZERO; // Restore original reduction
1290 // Step 15. Full depth search
1291 if (doFullDepthSearch)
1293 alpha = SpNode ? sp->alpha : alpha;
1294 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1296 // Step extra. pv search (only in PV nodes)
1297 // Search only for possible new PV nodes, if instead value >= beta then
1298 // parent node fails low with value <= alpha and tries another move.
1299 if (PvNode && value > alpha && value < beta)
1300 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1304 // Step 16. Undo move
1305 pos.undo_move(move);
1307 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1309 // Step 17. Check for new best move
1312 lock_grab(&(sp->lock));
1313 bestValue = sp->bestValue;
1317 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1322 sp->bestValue = value;
1326 if (PvNode && value < beta) // We want always alpha < beta
1334 sp->betaCutoff = true;
1336 if (value == value_mate_in(ply + 1))
1337 ss->mateKiller = move;
1339 ss->bestMove = move;
1342 sp->parentSstack->bestMove = move;
1346 // Step 18. Check for split
1348 && depth >= ThreadsMgr.min_split_depth()
1349 && ThreadsMgr.active_threads() > 1
1351 && ThreadsMgr.available_thread_exists(threadID)
1353 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1355 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1356 threatMove, mateThreat, moveCount, &mp, PvNode);
1359 // Step 19. Check for mate and stalemate
1360 // All legal moves have been searched and if there are
1361 // no legal moves, it must be mate or stalemate.
1362 // If one move was excluded return fail low score.
1363 if (!SpNode && !moveCount)
1364 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1366 // Step 20. Update tables
1367 // If the search is not aborted, update the transposition table,
1368 // history counters, and killer moves.
1369 if (!SpNode && !AbortSearch && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1371 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1372 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1373 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1375 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1377 // Update killers and history only for non capture moves that fails high
1378 if ( bestValue >= beta
1379 && !pos.move_is_capture_or_promotion(move))
1381 update_history(pos, move, depth, movesSearched, moveCount);
1382 update_killers(move, ss);
1388 // Here we have the lock still grabbed
1389 sp->slaves[threadID] = 0;
1390 sp->nodes += pos.nodes_searched();
1391 lock_release(&(sp->lock));
1394 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1399 // qsearch() is the quiescence search function, which is called by the main
1400 // search function when the remaining depth is zero (or, to be more precise,
1401 // less than ONE_PLY).
1403 template <NodeType PvNode>
1404 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1406 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1407 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1408 assert(PvNode || alpha == beta - 1);
1410 assert(ply > 0 && ply < PLY_MAX);
1411 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1415 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1416 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1419 Value oldAlpha = alpha;
1421 ss->bestMove = ss->currentMove = MOVE_NONE;
1423 // Check for an instant draw or maximum ply reached
1424 if (pos.is_draw() || ply >= PLY_MAX - 1)
1427 // Decide whether or not to include checks, this fixes also the type of
1428 // TT entry depth that we are going to use. Note that in qsearch we use
1429 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1430 isCheck = pos.is_check();
1431 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1433 // Transposition table lookup. At PV nodes, we don't use the TT for
1434 // pruning, but only for move ordering.
1435 tte = TT.retrieve(pos.get_key());
1436 ttMove = (tte ? tte->move() : MOVE_NONE);
1438 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1440 ss->bestMove = ttMove; // Can be MOVE_NONE
1441 return value_from_tt(tte->value(), ply);
1444 // Evaluate the position statically
1447 bestValue = futilityBase = -VALUE_INFINITE;
1448 ss->eval = evalMargin = VALUE_NONE;
1449 enoughMaterial = false;
1455 assert(tte->static_value() != VALUE_NONE);
1457 evalMargin = tte->static_value_margin();
1458 ss->eval = bestValue = tte->static_value();
1461 ss->eval = bestValue = evaluate(pos, evalMargin);
1463 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1465 // Stand pat. Return immediately if static value is at least beta
1466 if (bestValue >= beta)
1469 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1474 if (PvNode && bestValue > alpha)
1477 // Futility pruning parameters, not needed when in check
1478 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1479 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1482 // Initialize a MovePicker object for the current position, and prepare
1483 // to search the moves. Because the depth is <= 0 here, only captures,
1484 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1486 MovePicker mp(pos, ttMove, depth, H);
1489 // Loop through the moves until no moves remain or a beta cutoff occurs
1490 while ( alpha < beta
1491 && (move = mp.get_next_move()) != MOVE_NONE)
1493 assert(move_is_ok(move));
1495 moveIsCheck = pos.move_is_check(move, ci);
1503 && !move_is_promotion(move)
1504 && !pos.move_is_passed_pawn_push(move))
1506 futilityValue = futilityBase
1507 + pos.endgame_value_of_piece_on(move_to(move))
1508 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1510 if (futilityValue < alpha)
1512 if (futilityValue > bestValue)
1513 bestValue = futilityValue;
1518 // Detect non-capture evasions that are candidate to be pruned
1519 evasionPrunable = isCheck
1520 && bestValue > value_mated_in(PLY_MAX)
1521 && !pos.move_is_capture(move)
1522 && !pos.can_castle(pos.side_to_move());
1524 // Don't search moves with negative SEE values
1526 && (!isCheck || evasionPrunable)
1528 && !move_is_promotion(move)
1529 && pos.see_sign(move) < 0)
1532 // Don't search useless checks
1537 && !pos.move_is_capture_or_promotion(move)
1538 && ss->eval + PawnValueMidgame / 4 < beta
1539 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1541 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1542 bestValue = ss->eval + PawnValueMidgame / 4;
1547 // Update current move
1548 ss->currentMove = move;
1550 // Make and search the move
1551 pos.do_move(move, st, ci, moveIsCheck);
1552 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1553 pos.undo_move(move);
1555 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1558 if (value > bestValue)
1564 ss->bestMove = move;
1569 // All legal moves have been searched. A special case: If we're in check
1570 // and no legal moves were found, it is checkmate.
1571 if (isCheck && bestValue == -VALUE_INFINITE)
1572 return value_mated_in(ply);
1574 // Update transposition table
1575 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1576 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1578 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1584 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1585 // bestValue is updated only when returning false because in that case move
1588 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1590 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1591 Square from, to, ksq, victimSq;
1594 Value futilityValue, bv = *bestValue;
1596 from = move_from(move);
1598 them = opposite_color(pos.side_to_move());
1599 ksq = pos.king_square(them);
1600 kingAtt = pos.attacks_from<KING>(ksq);
1601 pc = pos.piece_on(from);
1603 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1604 oldAtt = pos.attacks_from(pc, from, occ);
1605 newAtt = pos.attacks_from(pc, to, occ);
1607 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1608 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1610 if (!(b && (b & (b - 1))))
1613 // Rule 2. Queen contact check is very dangerous
1614 if ( type_of_piece(pc) == QUEEN
1615 && bit_is_set(kingAtt, to))
1618 // Rule 3. Creating new double threats with checks
1619 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1623 victimSq = pop_1st_bit(&b);
1624 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1626 // Note that here we generate illegal "double move"!
1627 if ( futilityValue >= beta
1628 && pos.see_sign(make_move(from, victimSq)) >= 0)
1631 if (futilityValue > bv)
1635 // Update bestValue only if check is not dangerous (because we will prune the move)
1641 // connected_moves() tests whether two moves are 'connected' in the sense
1642 // that the first move somehow made the second move possible (for instance
1643 // if the moving piece is the same in both moves). The first move is assumed
1644 // to be the move that was made to reach the current position, while the
1645 // second move is assumed to be a move from the current position.
1647 bool connected_moves(const Position& pos, Move m1, Move m2) {
1649 Square f1, t1, f2, t2;
1652 assert(m1 && move_is_ok(m1));
1653 assert(m2 && move_is_ok(m2));
1655 // Case 1: The moving piece is the same in both moves
1661 // Case 2: The destination square for m2 was vacated by m1
1667 // Case 3: Moving through the vacated square
1668 if ( piece_is_slider(pos.piece_on(f2))
1669 && bit_is_set(squares_between(f2, t2), f1))
1672 // Case 4: The destination square for m2 is defended by the moving piece in m1
1673 p = pos.piece_on(t1);
1674 if (bit_is_set(pos.attacks_from(p, t1), t2))
1677 // Case 5: Discovered check, checking piece is the piece moved in m1
1678 if ( piece_is_slider(p)
1679 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1680 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1682 // discovered_check_candidates() works also if the Position's side to
1683 // move is the opposite of the checking piece.
1684 Color them = opposite_color(pos.side_to_move());
1685 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1687 if (bit_is_set(dcCandidates, f2))
1694 // value_is_mate() checks if the given value is a mate one eventually
1695 // compensated for the ply.
1697 bool value_is_mate(Value value) {
1699 assert(abs(value) <= VALUE_INFINITE);
1701 return value <= value_mated_in(PLY_MAX)
1702 || value >= value_mate_in(PLY_MAX);
1706 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1707 // "plies to mate from the current ply". Non-mate scores are unchanged.
1708 // The function is called before storing a value to the transposition table.
1710 Value value_to_tt(Value v, int ply) {
1712 if (v >= value_mate_in(PLY_MAX))
1715 if (v <= value_mated_in(PLY_MAX))
1722 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1723 // the transposition table to a mate score corrected for the current ply.
1725 Value value_from_tt(Value v, int ply) {
1727 if (v >= value_mate_in(PLY_MAX))
1730 if (v <= value_mated_in(PLY_MAX))
1737 // extension() decides whether a move should be searched with normal depth,
1738 // or with extended depth. Certain classes of moves (checking moves, in
1739 // particular) are searched with bigger depth than ordinary moves and in
1740 // any case are marked as 'dangerous'. Note that also if a move is not
1741 // extended, as example because the corresponding UCI option is set to zero,
1742 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1743 template <NodeType PvNode>
1744 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1745 bool singleEvasion, bool mateThreat, bool* dangerous) {
1747 assert(m != MOVE_NONE);
1749 Depth result = DEPTH_ZERO;
1750 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1754 if (moveIsCheck && pos.see_sign(m) >= 0)
1755 result += CheckExtension[PvNode];
1758 result += SingleEvasionExtension[PvNode];
1761 result += MateThreatExtension[PvNode];
1764 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1766 Color c = pos.side_to_move();
1767 if (relative_rank(c, move_to(m)) == RANK_7)
1769 result += PawnPushTo7thExtension[PvNode];
1772 if (pos.pawn_is_passed(c, move_to(m)))
1774 result += PassedPawnExtension[PvNode];
1779 if ( captureOrPromotion
1780 && pos.type_of_piece_on(move_to(m)) != PAWN
1781 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1782 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1783 && !move_is_promotion(m)
1786 result += PawnEndgameExtension[PvNode];
1791 && captureOrPromotion
1792 && pos.type_of_piece_on(move_to(m)) != PAWN
1793 && pos.see_sign(m) >= 0)
1795 result += ONE_PLY / 2;
1799 return Min(result, ONE_PLY);
1803 // connected_threat() tests whether it is safe to forward prune a move or if
1804 // is somehow coonected to the threat move returned by null search.
1806 bool connected_threat(const Position& pos, Move m, Move threat) {
1808 assert(move_is_ok(m));
1809 assert(threat && move_is_ok(threat));
1810 assert(!pos.move_is_check(m));
1811 assert(!pos.move_is_capture_or_promotion(m));
1812 assert(!pos.move_is_passed_pawn_push(m));
1814 Square mfrom, mto, tfrom, tto;
1816 mfrom = move_from(m);
1818 tfrom = move_from(threat);
1819 tto = move_to(threat);
1821 // Case 1: Don't prune moves which move the threatened piece
1825 // Case 2: If the threatened piece has value less than or equal to the
1826 // value of the threatening piece, don't prune move which defend it.
1827 if ( pos.move_is_capture(threat)
1828 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1829 || pos.type_of_piece_on(tfrom) == KING)
1830 && pos.move_attacks_square(m, tto))
1833 // Case 3: If the moving piece in the threatened move is a slider, don't
1834 // prune safe moves which block its ray.
1835 if ( piece_is_slider(pos.piece_on(tfrom))
1836 && bit_is_set(squares_between(tfrom, tto), mto)
1837 && pos.see_sign(m) >= 0)
1844 // ok_to_use_TT() returns true if a transposition table score
1845 // can be used at a given point in search.
1847 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1849 Value v = value_from_tt(tte->value(), ply);
1851 return ( tte->depth() >= depth
1852 || v >= Max(value_mate_in(PLY_MAX), beta)
1853 || v < Min(value_mated_in(PLY_MAX), beta))
1855 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1856 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1860 // refine_eval() returns the transposition table score if
1861 // possible otherwise falls back on static position evaluation.
1863 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1867 Value v = value_from_tt(tte->value(), ply);
1869 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1870 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1877 // update_history() registers a good move that produced a beta-cutoff
1878 // in history and marks as failures all the other moves of that ply.
1880 void update_history(const Position& pos, Move move, Depth depth,
1881 Move movesSearched[], int moveCount) {
1884 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
1886 for (int i = 0; i < moveCount - 1; i++)
1888 m = movesSearched[i];
1892 if (!pos.move_is_capture_or_promotion(m))
1893 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
1898 // update_killers() add a good move that produced a beta-cutoff
1899 // among the killer moves of that ply.
1901 void update_killers(Move m, SearchStack* ss) {
1903 if (m == ss->killers[0])
1906 ss->killers[1] = ss->killers[0];
1911 // update_gains() updates the gains table of a non-capture move given
1912 // the static position evaluation before and after the move.
1914 void update_gains(const Position& pos, Move m, Value before, Value after) {
1917 && before != VALUE_NONE
1918 && after != VALUE_NONE
1919 && pos.captured_piece_type() == PIECE_TYPE_NONE
1920 && !move_is_special(m))
1921 H.set_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1925 // current_search_time() returns the number of milliseconds which have passed
1926 // since the beginning of the current search.
1928 int current_search_time() {
1930 return get_system_time() - SearchStartTime;
1934 // value_to_uci() converts a value to a string suitable for use with the UCI
1935 // protocol specifications:
1937 // cp <x> The score from the engine's point of view in centipawns.
1938 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1939 // use negative values for y.
1941 std::string value_to_uci(Value v) {
1943 std::stringstream s;
1945 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1946 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1948 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1953 // nps() computes the current nodes/second count.
1955 int nps(const Position& pos) {
1957 int t = current_search_time();
1958 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1962 // poll() performs two different functions: It polls for user input, and it
1963 // looks at the time consumed so far and decides if it's time to abort the
1966 void poll(const Position& pos) {
1968 static int lastInfoTime;
1969 int t = current_search_time();
1972 if (data_available())
1974 // We are line oriented, don't read single chars
1975 std::string command;
1977 if (!std::getline(std::cin, command))
1980 if (command == "quit")
1983 PonderSearch = false;
1987 else if (command == "stop")
1990 PonderSearch = false;
1992 else if (command == "ponderhit")
1996 // Print search information
2000 else if (lastInfoTime > t)
2001 // HACK: Must be a new search where we searched less than
2002 // NodesBetweenPolls nodes during the first second of search.
2005 else if (t - lastInfoTime >= 1000)
2012 if (dbg_show_hit_rate)
2013 dbg_print_hit_rate();
2015 cout << "info nodes " << pos.nodes_searched() << " nps " << nps(pos)
2016 << " time " << t << endl;
2019 // Should we stop the search?
2023 bool stillAtFirstMove = FirstRootMove
2024 && !AspirationFailLow
2025 && t > TimeMgr.available_time();
2027 bool noMoreTime = t > TimeMgr.maximum_time()
2028 || stillAtFirstMove;
2030 if ( (Iteration >= 3 && UseTimeManagement && noMoreTime)
2031 || (ExactMaxTime && t >= ExactMaxTime)
2032 || (Iteration >= 3 && MaxNodes && pos.nodes_searched() >= MaxNodes))
2037 // ponderhit() is called when the program is pondering (i.e. thinking while
2038 // it's the opponent's turn to move) in order to let the engine know that
2039 // it correctly predicted the opponent's move.
2043 int t = current_search_time();
2044 PonderSearch = false;
2046 bool stillAtFirstMove = FirstRootMove
2047 && !AspirationFailLow
2048 && t > TimeMgr.available_time();
2050 bool noMoreTime = t > TimeMgr.maximum_time()
2051 || stillAtFirstMove;
2053 if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit))
2058 // init_ss_array() does a fast reset of the first entries of a SearchStack
2059 // array and of all the excludedMove and skipNullMove entries.
2061 void init_ss_array(SearchStack* ss, int size) {
2063 for (int i = 0; i < size; i++, ss++)
2065 ss->excludedMove = MOVE_NONE;
2066 ss->skipNullMove = false;
2067 ss->reduction = DEPTH_ZERO;
2071 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
2076 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2077 // while the program is pondering. The point is to work around a wrinkle in
2078 // the UCI protocol: When pondering, the engine is not allowed to give a
2079 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2080 // We simply wait here until one of these commands is sent, and return,
2081 // after which the bestmove and pondermove will be printed (in id_loop()).
2083 void wait_for_stop_or_ponderhit() {
2085 std::string command;
2089 if (!std::getline(std::cin, command))
2092 if (command == "quit")
2097 else if (command == "ponderhit" || command == "stop")
2103 // init_thread() is the function which is called when a new thread is
2104 // launched. It simply calls the idle_loop() function with the supplied
2105 // threadID. There are two versions of this function; one for POSIX
2106 // threads and one for Windows threads.
2108 #if !defined(_MSC_VER)
2110 void* init_thread(void* threadID) {
2112 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2118 DWORD WINAPI init_thread(LPVOID threadID) {
2120 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2127 /// The ThreadsManager class
2130 // read_uci_options() updates number of active threads and other internal
2131 // parameters according to the UCI options values. It is called before
2132 // to start a new search.
2134 void ThreadsManager::read_uci_options() {
2136 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2137 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2138 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2139 activeThreads = Options["Threads"].value<int>();
2143 // idle_loop() is where the threads are parked when they have no work to do.
2144 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2145 // object for which the current thread is the master.
2147 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2149 assert(threadID >= 0 && threadID < MAX_THREADS);
2152 bool allFinished = false;
2156 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2157 // master should exit as last one.
2158 if (allThreadsShouldExit)
2161 threads[threadID].state = THREAD_TERMINATED;
2165 // If we are not thinking, wait for a condition to be signaled
2166 // instead of wasting CPU time polling for work.
2167 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2168 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2170 assert(!sp || useSleepingThreads);
2171 assert(threadID != 0 || useSleepingThreads);
2173 if (threads[threadID].state == THREAD_INITIALIZING)
2174 threads[threadID].state = THREAD_AVAILABLE;
2176 // Grab the lock to avoid races with wake_sleeping_thread()
2177 lock_grab(&sleepLock[threadID]);
2179 // If we are master and all slaves have finished do not go to sleep
2180 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2181 allFinished = (i == activeThreads);
2183 if (allFinished || allThreadsShouldExit)
2185 lock_release(&sleepLock[threadID]);
2189 // Do sleep here after retesting sleep conditions
2190 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2191 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2193 lock_release(&sleepLock[threadID]);
2196 // If this thread has been assigned work, launch a search
2197 if (threads[threadID].state == THREAD_WORKISWAITING)
2199 assert(!allThreadsShouldExit);
2201 threads[threadID].state = THREAD_SEARCHING;
2203 // Here we call search() with SplitPoint template parameter set to true
2204 SplitPoint* tsp = threads[threadID].splitPoint;
2205 Position pos(*tsp->pos, threadID);
2206 SearchStack* ss = tsp->sstack[threadID] + 1;
2210 search<PV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2212 search<NonPV, true>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2214 assert(threads[threadID].state == THREAD_SEARCHING);
2216 threads[threadID].state = THREAD_AVAILABLE;
2218 // Wake up master thread so to allow it to return from the idle loop in
2219 // case we are the last slave of the split point.
2220 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2221 wake_sleeping_thread(tsp->master);
2224 // If this thread is the master of a split point and all slaves have
2225 // finished their work at this split point, return from the idle loop.
2226 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2227 allFinished = (i == activeThreads);
2231 // Because sp->slaves[] is reset under lock protection,
2232 // be sure sp->lock has been released before to return.
2233 lock_grab(&(sp->lock));
2234 lock_release(&(sp->lock));
2236 // In helpful master concept a master can help only a sub-tree, and
2237 // because here is all finished is not possible master is booked.
2238 assert(threads[threadID].state == THREAD_AVAILABLE);
2240 threads[threadID].state = THREAD_SEARCHING;
2247 // init_threads() is called during startup. It launches all helper threads,
2248 // and initializes the split point stack and the global locks and condition
2251 void ThreadsManager::init_threads() {
2253 int i, arg[MAX_THREADS];
2256 // Initialize global locks
2259 for (i = 0; i < MAX_THREADS; i++)
2261 lock_init(&sleepLock[i]);
2262 cond_init(&sleepCond[i]);
2265 // Initialize splitPoints[] locks
2266 for (i = 0; i < MAX_THREADS; i++)
2267 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2268 lock_init(&(threads[i].splitPoints[j].lock));
2270 // Will be set just before program exits to properly end the threads
2271 allThreadsShouldExit = false;
2273 // Threads will be put all threads to sleep as soon as created
2276 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2277 threads[0].state = THREAD_SEARCHING;
2278 for (i = 1; i < MAX_THREADS; i++)
2279 threads[i].state = THREAD_INITIALIZING;
2281 // Launch the helper threads
2282 for (i = 1; i < MAX_THREADS; i++)
2286 #if !defined(_MSC_VER)
2287 pthread_t pthread[1];
2288 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2289 pthread_detach(pthread[0]);
2291 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2295 cout << "Failed to create thread number " << i << endl;
2299 // Wait until the thread has finished launching and is gone to sleep
2300 while (threads[i].state == THREAD_INITIALIZING) {}
2305 // exit_threads() is called when the program exits. It makes all the
2306 // helper threads exit cleanly.
2308 void ThreadsManager::exit_threads() {
2310 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2312 // Wake up all the threads and waits for termination
2313 for (int i = 1; i < MAX_THREADS; i++)
2315 wake_sleeping_thread(i);
2316 while (threads[i].state != THREAD_TERMINATED) {}
2319 // Now we can safely destroy the locks
2320 for (int i = 0; i < MAX_THREADS; i++)
2321 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2322 lock_destroy(&(threads[i].splitPoints[j].lock));
2324 lock_destroy(&mpLock);
2326 // Now we can safely destroy the wait conditions
2327 for (int i = 0; i < MAX_THREADS; i++)
2329 lock_destroy(&sleepLock[i]);
2330 cond_destroy(&sleepCond[i]);
2335 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2336 // the thread's currently active split point, or in some ancestor of
2337 // the current split point.
2339 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2341 assert(threadID >= 0 && threadID < activeThreads);
2343 SplitPoint* sp = threads[threadID].splitPoint;
2345 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2350 // thread_is_available() checks whether the thread with threadID "slave" is
2351 // available to help the thread with threadID "master" at a split point. An
2352 // obvious requirement is that "slave" must be idle. With more than two
2353 // threads, this is not by itself sufficient: If "slave" is the master of
2354 // some active split point, it is only available as a slave to the other
2355 // threads which are busy searching the split point at the top of "slave"'s
2356 // split point stack (the "helpful master concept" in YBWC terminology).
2358 bool ThreadsManager::thread_is_available(int slave, int master) const {
2360 assert(slave >= 0 && slave < activeThreads);
2361 assert(master >= 0 && master < activeThreads);
2362 assert(activeThreads > 1);
2364 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2367 // Make a local copy to be sure doesn't change under our feet
2368 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2370 // No active split points means that the thread is available as
2371 // a slave for any other thread.
2372 if (localActiveSplitPoints == 0 || activeThreads == 2)
2375 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2376 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2377 // could have been set to 0 by another thread leading to an out of bound access.
2378 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2385 // available_thread_exists() tries to find an idle thread which is available as
2386 // a slave for the thread with threadID "master".
2388 bool ThreadsManager::available_thread_exists(int master) const {
2390 assert(master >= 0 && master < activeThreads);
2391 assert(activeThreads > 1);
2393 for (int i = 0; i < activeThreads; i++)
2394 if (thread_is_available(i, master))
2401 // split() does the actual work of distributing the work at a node between
2402 // several available threads. If it does not succeed in splitting the
2403 // node (because no idle threads are available, or because we have no unused
2404 // split point objects), the function immediately returns. If splitting is
2405 // possible, a SplitPoint object is initialized with all the data that must be
2406 // copied to the helper threads and we tell our helper threads that they have
2407 // been assigned work. This will cause them to instantly leave their idle loops and
2408 // call search().When all threads have returned from search() then split() returns.
2410 template <bool Fake>
2411 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2412 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2413 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2414 assert(pos.is_ok());
2415 assert(ply > 0 && ply < PLY_MAX);
2416 assert(*bestValue >= -VALUE_INFINITE);
2417 assert(*bestValue <= *alpha);
2418 assert(*alpha < beta);
2419 assert(beta <= VALUE_INFINITE);
2420 assert(depth > DEPTH_ZERO);
2421 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2422 assert(activeThreads > 1);
2424 int i, master = pos.thread();
2425 Thread& masterThread = threads[master];
2429 // If no other thread is available to help us, or if we have too many
2430 // active split points, don't split.
2431 if ( !available_thread_exists(master)
2432 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2434 lock_release(&mpLock);
2438 // Pick the next available split point object from the split point stack
2439 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2441 // Initialize the split point object
2442 splitPoint.parent = masterThread.splitPoint;
2443 splitPoint.master = master;
2444 splitPoint.betaCutoff = false;
2445 splitPoint.ply = ply;
2446 splitPoint.depth = depth;
2447 splitPoint.threatMove = threatMove;
2448 splitPoint.mateThreat = mateThreat;
2449 splitPoint.alpha = *alpha;
2450 splitPoint.beta = beta;
2451 splitPoint.pvNode = pvNode;
2452 splitPoint.bestValue = *bestValue;
2454 splitPoint.moveCount = moveCount;
2455 splitPoint.pos = &pos;
2456 splitPoint.nodes = 0;
2457 splitPoint.parentSstack = ss;
2458 for (i = 0; i < activeThreads; i++)
2459 splitPoint.slaves[i] = 0;
2461 masterThread.splitPoint = &splitPoint;
2463 // If we are here it means we are not available
2464 assert(masterThread.state != THREAD_AVAILABLE);
2466 int workersCnt = 1; // At least the master is included
2468 // Allocate available threads setting state to THREAD_BOOKED
2469 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2470 if (thread_is_available(i, master))
2472 threads[i].state = THREAD_BOOKED;
2473 threads[i].splitPoint = &splitPoint;
2474 splitPoint.slaves[i] = 1;
2478 assert(Fake || workersCnt > 1);
2480 // We can release the lock because slave threads are already booked and master is not available
2481 lock_release(&mpLock);
2483 // Tell the threads that they have work to do. This will make them leave
2484 // their idle loop. But before copy search stack tail for each thread.
2485 for (i = 0; i < activeThreads; i++)
2486 if (i == master || splitPoint.slaves[i])
2488 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2490 assert(i == master || threads[i].state == THREAD_BOOKED);
2492 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2494 if (useSleepingThreads && i != master)
2495 wake_sleeping_thread(i);
2498 // Everything is set up. The master thread enters the idle loop, from
2499 // which it will instantly launch a search, because its state is
2500 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2501 // idle loop, which means that the main thread will return from the idle
2502 // loop when all threads have finished their work at this split point.
2503 idle_loop(master, &splitPoint);
2505 // We have returned from the idle loop, which means that all threads are
2506 // finished. Update alpha and bestValue, and return.
2509 *alpha = splitPoint.alpha;
2510 *bestValue = splitPoint.bestValue;
2511 masterThread.activeSplitPoints--;
2512 masterThread.splitPoint = splitPoint.parent;
2513 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2515 lock_release(&mpLock);
2519 // wake_sleeping_thread() wakes up the thread with the given threadID
2520 // when it is time to start a new search.
2522 void ThreadsManager::wake_sleeping_thread(int threadID) {
2524 lock_grab(&sleepLock[threadID]);
2525 cond_signal(&sleepCond[threadID]);
2526 lock_release(&sleepLock[threadID]);
2530 /// RootMove and RootMoveList method's definitions
2532 RootMove::RootMove() {
2535 pv_score = non_pv_score = -VALUE_INFINITE;
2539 RootMove& RootMove::operator=(const RootMove& rm) {
2541 const Move* src = rm.pv;
2544 // Avoid a costly full rm.pv[] copy
2545 do *dst++ = *src; while (*src++ != MOVE_NONE);
2548 pv_score = rm.pv_score;
2549 non_pv_score = rm.non_pv_score;
2553 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2554 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2555 // allow to always have a ponder move even when we fail high at root and also a
2556 // long PV to print that is important for position analysis.
2558 void RootMove::extract_pv_from_tt(Position& pos) {
2560 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2564 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2566 pos.do_move(pv[0], *st++);
2568 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2569 && tte->move() != MOVE_NONE
2570 && move_is_legal(pos, tte->move())
2572 && (!pos.is_draw() || ply < 2))
2574 pv[ply] = tte->move();
2575 pos.do_move(pv[ply++], *st++);
2577 pv[ply] = MOVE_NONE;
2579 do pos.undo_move(pv[--ply]); while (ply);
2582 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2583 // the PV back into the TT. This makes sure the old PV moves are searched
2584 // first, even if the old TT entries have been overwritten.
2586 void RootMove::insert_pv_in_tt(Position& pos) {
2588 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2591 Value v, m = VALUE_NONE;
2594 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2598 tte = TT.retrieve(k);
2600 // Don't overwrite exsisting correct entries
2601 if (!tte || tte->move() != pv[ply])
2603 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2604 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2606 pos.do_move(pv[ply], *st++);
2608 } while (pv[++ply] != MOVE_NONE);
2610 do pos.undo_move(pv[--ply]); while (ply);
2613 // pv_info_to_uci() returns a string with information on the current PV line
2614 // formatted according to UCI specification and eventually writes the info
2615 // to a log file. It is called at each iteration or after a new pv is found.
2617 std::string RootMove::pv_info_to_uci(const Position& pos, Value alpha, Value beta, int pvLine) {
2619 std::stringstream s;
2621 s << "info depth " << Iteration // FIXME
2622 << " multipv " << pvLine + 1
2623 << " score " << value_to_uci(pv_score)
2624 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2625 << " time " << current_search_time()
2626 << " nodes " << pos.nodes_searched()
2627 << " nps " << nps(pos)
2630 for (Move* m = pv; *m != MOVE_NONE; m++)
2633 if (UseLogFile && pvLine == 0)
2635 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2636 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2638 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2644 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2646 SearchStack ss[PLY_MAX_PLUS_2];
2647 MoveStack mlist[MOVES_MAX];
2651 // Initialize search stack
2652 init_ss_array(ss, PLY_MAX_PLUS_2);
2653 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2655 // Generate all legal moves
2656 MoveStack* last = generate_moves(pos, mlist);
2658 // Add each move to the RootMoveList's vector
2659 for (MoveStack* cur = mlist; cur != last; cur++)
2661 // If we have a searchMoves[] list then verify cur->move
2662 // is in the list before to add it.
2663 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2665 if (searchMoves[0] && *sm != cur->move)
2668 // Find a quick score for the move and add to the list
2669 pos.do_move(cur->move, st);
2672 rm.pv[0] = ss[0].currentMove = cur->move;
2673 rm.pv[1] = MOVE_NONE;
2674 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2677 pos.undo_move(cur->move);
2682 // Score root moves using the standard way used in main search, the moves
2683 // are scored according to the order in which are returned by MovePicker.
2684 // This is the second order score that is used to compare the moves when
2685 // the first order pv scores of both moves are equal.
2687 void RootMoveList::set_non_pv_scores(const Position& pos)
2690 Value score = VALUE_ZERO;
2691 MovePicker mp(pos, MOVE_NONE, ONE_PLY, H);
2693 while ((move = mp.get_next_move()) != MOVE_NONE)
2694 for (Base::iterator it = begin(); it != end(); ++it)
2695 if (it->pv[0] == move)
2697 it->non_pv_score = score--;