2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
45 #include "ucioption.h"
51 //// Local definitions
57 enum NodeType { NonPV, PV };
59 // Set to true to force running with one thread.
60 // Used for debugging SMP code.
61 const bool FakeSplit = false;
63 // Fast lookup table of sliding pieces indexed by Piece
64 const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 };
65 inline bool piece_is_slider(Piece p) { return Slidings[p]; }
67 // ThreadsManager class is used to handle all the threads related stuff in search,
68 // init, starting, parking and, the most important, launching a slave thread at a
69 // split point are what this class does. All the access to shared thread data is
70 // done through this class, so that we avoid using global variables instead.
72 class ThreadsManager {
73 /* As long as the single ThreadsManager object is defined as a global we don't
74 need to explicitly initialize to zero its data members because variables with
75 static storage duration are automatically set to zero before enter main()
81 int min_split_depth() const { return minimumSplitDepth; }
82 int active_threads() const { return activeThreads; }
83 void set_active_threads(int cnt) { activeThreads = cnt; }
85 void read_uci_options();
86 bool available_thread_exists(int master) const;
87 bool thread_is_available(int slave, int master) const;
88 bool cutoff_at_splitpoint(int threadID) const;
89 void wake_sleeping_thread(int threadID);
90 void idle_loop(int threadID, SplitPoint* sp);
93 void split(Position& pos, SearchStack* ss, int ply, Value* alpha, const Value beta, Value* bestValue,
94 Depth depth, Move threatMove, bool mateThreat, int moveCount, MovePicker* mp, bool pvNode);
97 Depth minimumSplitDepth;
98 int maxThreadsPerSplitPoint;
99 bool useSleepingThreads;
101 volatile bool allThreadsShouldExit;
102 Thread threads[MAX_THREADS];
103 Lock mpLock, sleepLock[MAX_THREADS];
104 WaitCondition sleepCond[MAX_THREADS];
108 // RootMove struct is used for moves at the root at the tree. For each root
109 // move, we store two scores, a node count, and a PV (really a refutation
110 // in the case of moves which fail low). Value pv_score is normally set at
111 // -VALUE_INFINITE for all non-pv moves, while non_pv_score is computed
112 // according to the order in which moves are returned by MovePicker.
117 RootMove(const RootMove& rm) { *this = rm; }
118 RootMove& operator=(const RootMove& rm);
120 // RootMove::operator<() is the comparison function used when
121 // sorting the moves. A move m1 is considered to be better
122 // than a move m2 if it has an higher pv_score, or if it has
123 // equal pv_score but m1 has the higher non_pv_score. In this
124 // way we are guaranteed that PV moves are always sorted as first.
125 bool operator<(const RootMove& m) const {
126 return pv_score != m.pv_score ? pv_score < m.pv_score
127 : non_pv_score < m.non_pv_score;
130 void extract_pv_from_tt(Position& pos);
131 void insert_pv_in_tt(Position& pos);
132 std::string pv_info_to_uci(Position& pos, 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, Move ttm, SearchStack* ss);
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& f) {
166 os.iword(0) = int(f);
171 // Overload operator << for moves to make it easier to print moves in
172 // coordinate notation compatible with UCI protocol.
173 std::ostream& operator<<(std::ostream& os, Move m) {
175 bool chess960 = (os.iword(0) != 0); // See set960()
176 return os << move_to_uci(m, chess960);
184 // Maximum depth for razoring
185 const Depth RazorDepth = 4 * ONE_PLY;
187 // Dynamic razoring margin based on depth
188 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
190 // Maximum depth for use of dynamic threat detection when null move fails low
191 const Depth ThreatDepth = 5 * ONE_PLY;
193 // Step 9. Internal iterative deepening
195 // Minimum depth for use of internal iterative deepening
196 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
198 // At Non-PV nodes we do an internal iterative deepening search
199 // when the static evaluation is bigger then beta - IIDMargin.
200 const Value IIDMargin = Value(0x100);
202 // Step 11. Decide the new search depth
204 // Extensions. Configurable UCI options
205 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
206 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
207 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
209 // Minimum depth for use of singular extension
210 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
212 // If the TT move is at least SingularExtensionMargin better then the
213 // remaining ones we will extend it.
214 const Value SingularExtensionMargin = Value(0x20);
216 // Step 12. Futility pruning
218 // Futility margin for quiescence search
219 const Value FutilityMarginQS = Value(0x80);
221 // Futility lookup tables (initialized at startup) and their getter functions
222 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
223 int FutilityMoveCountArray[32]; // [depth]
225 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
226 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
228 // Step 14. Reduced search
230 // Reduction lookup tables (initialized at startup) and their getter functions
231 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
233 template <NodeType PV>
234 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
236 // Common adjustments
238 // Search depth at iteration 1
239 const Depth InitialDepth = ONE_PLY;
241 // Easy move margin. An easy move candidate must be at least this much
242 // better than the second best move.
243 const Value EasyMoveMargin = Value(0x200);
246 /// Namespace variables
251 // Pointer to root move list
257 // Scores and number of times the best move changed for each iteration
258 Value ValueByIteration[PLY_MAX_PLUS_2];
259 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
261 // Search window management
267 // Time managment variables
268 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
269 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
270 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
275 std::ofstream LogFile;
277 // Multi-threads manager object
278 ThreadsManager ThreadsMgr;
280 // Node counters, used only by thread[0] but try to keep in different cache
281 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
282 bool SendSearchedNodes;
284 int NodesBetweenPolls = 30000;
291 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
293 template <NodeType PvNode, bool SpNode, bool Root>
294 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
296 template <NodeType PvNode>
297 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
299 template <NodeType PvNode>
300 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
302 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
303 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
306 template <NodeType PvNode>
307 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
309 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
310 bool connected_moves(const Position& pos, Move m1, Move m2);
311 bool value_is_mate(Value value);
312 Value value_to_tt(Value v, int ply);
313 Value value_from_tt(Value v, int ply);
314 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
315 bool connected_threat(const Position& pos, Move m, Move threat);
316 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
317 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
318 void update_killers(Move m, Move killers[]);
319 void update_gains(const Position& pos, Move move, Value before, Value after);
321 int current_search_time();
322 std::string value_to_uci(Value v);
323 int nps(const Position& pos);
324 void poll(const Position& pos);
325 void wait_for_stop_or_ponderhit();
326 void init_ss_array(SearchStack* ss, int size);
328 #if !defined(_MSC_VER)
329 void* init_thread(void* threadID);
331 DWORD WINAPI init_thread(LPVOID threadID);
341 /// init_threads(), exit_threads() and nodes_searched() are helpers to
342 /// give accessibility to some TM methods from outside of current file.
344 void init_threads() { ThreadsMgr.init_threads(); }
345 void exit_threads() { ThreadsMgr.exit_threads(); }
348 /// init_search() is called during startup. It initializes various lookup tables
352 int d; // depth (ONE_PLY == 2)
353 int hd; // half depth (ONE_PLY == 1)
356 // Init reductions array
357 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
359 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
360 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
361 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
362 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
365 // Init futility margins array
366 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
367 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
369 // Init futility move count array
370 for (d = 0; d < 32; d++)
371 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
375 /// perft() is our utility to verify move generation is bug free. All the legal
376 /// moves up to given depth are generated and counted and the sum returned.
378 int64_t perft(Position& pos, Depth depth)
380 MoveStack mlist[MOVES_MAX];
385 // Generate all legal moves
386 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
388 // If we are at the last ply we don't need to do and undo
389 // the moves, just to count them.
390 if (depth <= ONE_PLY)
391 return int(last - mlist);
393 // Loop through all legal moves
395 for (MoveStack* cur = mlist; cur != last; cur++)
398 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
399 sum += perft(pos, depth - ONE_PLY);
406 /// think() is the external interface to Stockfish's search, and is called when
407 /// the program receives the UCI 'go' command. It initializes various
408 /// search-related global variables, and calls id_loop(). It returns false
409 /// when a quit command is received during the search.
411 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
412 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
414 // Initialize global search variables
415 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
417 SearchStartTime = get_system_time();
418 ExactMaxTime = maxTime;
421 InfiniteSearch = infinite;
423 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
425 // Look for a book move, only during games, not tests
426 if (UseTimeManagement && Options["OwnBook"].value<bool>())
428 if (Options["Book File"].value<std::string>() != OpeningBook.name())
429 OpeningBook.open(Options["Book File"].value<std::string>());
431 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
432 if (bookMove != MOVE_NONE)
435 wait_for_stop_or_ponderhit();
437 cout << "bestmove " << bookMove << endl;
442 // Read UCI option values
443 TT.set_size(Options["Hash"].value<int>());
444 if (Options["Clear Hash"].value<bool>())
446 Options["Clear Hash"].set_value("false");
450 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
451 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
452 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
453 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
454 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
455 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
456 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
457 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
458 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
459 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
460 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
461 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
462 MultiPV = Options["MultiPV"].value<int>();
463 UseLogFile = Options["Use Search Log"].value<bool>();
465 read_evaluation_uci_options(pos.side_to_move());
467 // Set the number of active threads
468 ThreadsMgr.read_uci_options();
469 init_eval(ThreadsMgr.active_threads());
471 // Wake up needed threads
472 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
473 ThreadsMgr.wake_sleeping_thread(i);
476 int myTime = time[pos.side_to_move()];
477 int myIncrement = increment[pos.side_to_move()];
478 if (UseTimeManagement)
479 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
481 // Set best NodesBetweenPolls interval to avoid lagging under
482 // heavy time pressure.
484 NodesBetweenPolls = Min(MaxNodes, 30000);
485 else if (myTime && myTime < 1000)
486 NodesBetweenPolls = 1000;
487 else if (myTime && myTime < 5000)
488 NodesBetweenPolls = 5000;
490 NodesBetweenPolls = 30000;
492 // Write search information to log file
495 std::string name = Options["Search Log Filename"].value<std::string>();
496 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
498 LogFile << "Searching: " << pos.to_fen()
499 << "\ninfinite: " << infinite
500 << " ponder: " << ponder
501 << " time: " << myTime
502 << " increment: " << myIncrement
503 << " moves to go: " << movesToGo << endl;
506 // We're ready to start thinking. Call the iterative deepening loop function
507 Move ponderMove = MOVE_NONE;
508 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
510 // Print final search statistics
511 cout << "info nodes " << pos.nodes_searched()
512 << " nps " << nps(pos)
513 << " time " << current_search_time() << endl;
517 LogFile << "\nNodes: " << pos.nodes_searched()
518 << "\nNodes/second: " << nps(pos)
519 << "\nBest move: " << move_to_san(pos, bestMove);
522 pos.do_move(bestMove, st);
523 LogFile << "\nPonder move: "
524 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
527 // Return from think() with unchanged position
528 pos.undo_move(bestMove);
533 // This makes all the threads to go to sleep
534 ThreadsMgr.set_active_threads(1);
536 // If we are pondering or in infinite search, we shouldn't print the
537 // best move before we are told to do so.
538 if (!StopRequest && (Pondering || InfiniteSearch))
539 wait_for_stop_or_ponderhit();
541 // Could be both MOVE_NONE when searching on a stalemate position
542 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
550 // id_loop() is the main iterative deepening loop. It calls search()
551 // repeatedly with increasing depth until the allocated thinking time has
552 // been consumed, the user stops the search, or the maximum search depth is
555 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
557 SearchStack ss[PLY_MAX_PLUS_2];
559 Move EasyMove = MOVE_NONE;
560 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
561 int researchCountFL, researchCountFH;
563 // Moves to search are verified, scored and sorted
564 RootMoveList rml(pos, searchMoves);
567 // Handle special case of searching on a mate/stale position
570 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
572 cout << "info depth " << 1
573 << " score " << value_to_uci(s) << endl;
581 init_ss_array(ss, PLY_MAX_PLUS_2);
582 ValueByIteration[1] = rml[0].pv_score;
585 // Send initial RootMoveList scoring (iteration 1)
586 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
587 << "info depth " << Iteration
588 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
590 // Is one move significantly better than others after initial scoring ?
592 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
593 EasyMove = rml[0].pv[0];
595 // Iterative deepening loop
596 while (Iteration < PLY_MAX)
598 // Initialize iteration
600 BestMoveChangesByIteration[Iteration] = 0;
602 cout << "info depth " << Iteration << endl;
604 // Calculate dynamic aspiration window based on previous iterations
605 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
607 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
608 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
610 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
611 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
613 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
614 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
617 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
619 researchCountFL = researchCountFH = 0;
621 // We start with small aspiration window and in case of fail high/low, we
622 // research with bigger window until we are not failing high/low anymore.
625 // Sort the moves before to (re)search
626 rml.set_non_pv_scores(pos, rml[0].pv[0], ss);
629 // Search to the current depth, rml is updated and sorted
630 value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
632 // Sort the moves before to return
635 // Write PV lines to transposition table, in case the relevant entries
636 // have been overwritten during the search.
637 for (int i = 0; i < Min(MultiPV, (int)rml.size()); i++)
638 rml[i].insert_pv_in_tt(pos);
643 assert(value >= alpha);
647 // Prepare for a research after a fail high, each time with a wider window
648 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
651 else if (value <= alpha)
653 AspirationFailLow = true;
654 StopOnPonderhit = false;
656 // Prepare for a research after a fail low, each time with a wider window
657 alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
665 break; // Value cannot be trusted. Break out immediately!
667 //Save info about search result
668 ValueByIteration[Iteration] = value;
670 // Drop the easy move if differs from the new best move
671 if (rml[0].pv[0] != EasyMove)
672 EasyMove = MOVE_NONE;
674 if (UseTimeManagement)
677 bool stopSearch = false;
679 // Stop search early if there is only a single legal move,
680 // we search up to Iteration 6 anyway to get a proper score.
681 if (Iteration >= 6 && rml.size() == 1)
684 // Stop search early when the last two iterations returned a mate score
686 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
687 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
690 // Stop search early if one move seems to be much better than the others
692 && EasyMove == rml[0].pv[0]
693 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
694 && current_search_time() > TimeMgr.available_time() / 16)
695 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
696 && current_search_time() > TimeMgr.available_time() / 32)))
699 // Add some extra time if the best move has changed during the last two iterations
700 if (Iteration > 5 && Iteration <= 50)
701 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
702 BestMoveChangesByIteration[Iteration-1]);
704 // Stop search if most of MaxSearchTime is consumed at the end of the
705 // iteration. We probably don't have enough time to search the first
706 // move at the next iteration anyway.
707 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
713 StopOnPonderhit = true;
719 if (MaxDepth && Iteration >= MaxDepth)
723 *ponderMove = rml[0].pv[1];
728 // search<>() is the main search function for both PV and non-PV nodes and for
729 // normal and SplitPoint nodes. When called just after a split point the search
730 // is simpler because we have already probed the hash table, done a null move
731 // search, and searched the first move before splitting, we don't have to repeat
732 // all this work again. We also don't need to store anything to the hash table
733 // here: This is taken care of after we return from the split point.
735 template <NodeType PvNode, bool SpNode, bool Root>
736 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
738 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
739 assert(beta > alpha && beta <= VALUE_INFINITE);
740 assert(PvNode || alpha == beta - 1);
741 assert((Root || ply > 0) && ply < PLY_MAX);
742 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
744 Move movesSearched[MOVES_MAX];
746 RootMoveList::iterator rm;
750 Move ttMove, move, excludedMove, threatMove;
753 Value bestValue, value, oldAlpha;
754 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
755 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
756 bool mateThreat = false;
758 int threadID = pos.thread();
759 SplitPoint* sp = NULL;
761 refinedValue = bestValue = value = -VALUE_INFINITE;
763 isCheck = pos.is_check();
769 ttMove = excludedMove = MOVE_NONE;
770 threatMove = sp->threatMove;
771 mateThreat = sp->mateThreat;
772 goto split_point_start;
774 else {} // Hack to fix icc's "statement is unreachable" warning
776 // Step 1. Initialize node and poll. Polling can abort search
777 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
778 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
782 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
788 // Step 2. Check for aborted search and immediate draw
790 || ThreadsMgr.cutoff_at_splitpoint(threadID)
792 || ply >= PLY_MAX - 1)
795 // Step 3. Mate distance pruning
796 alpha = Max(value_mated_in(ply), alpha);
797 beta = Min(value_mate_in(ply+1), beta);
802 // Step 4. Transposition table lookup
804 // We don't want the score of a partial search to overwrite a previous full search
805 // TT value, so we use a different position key in case of an excluded move exists.
806 excludedMove = ss->excludedMove;
807 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
809 tte = TT.retrieve(posKey);
810 ttMove = tte ? tte->move() : MOVE_NONE;
812 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
813 // This is to avoid problems in the following areas:
815 // * Repetition draw detection
816 // * Fifty move rule detection
817 // * Searching for a mate
818 // * Printing of full PV line
819 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
822 ss->bestMove = ttMove; // Can be MOVE_NONE
823 return value_from_tt(tte->value(), ply);
826 // Step 5. Evaluate the position statically and
827 // update gain statistics of parent move.
829 ss->eval = ss->evalMargin = VALUE_NONE;
832 assert(tte->static_value() != VALUE_NONE);
834 ss->eval = tte->static_value();
835 ss->evalMargin = tte->static_value_margin();
836 refinedValue = refine_eval(tte, ss->eval, ply);
840 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
841 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
844 // Save gain for the parent non-capture move
846 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
848 // Step 6. Razoring (is omitted in PV nodes)
850 && depth < RazorDepth
852 && refinedValue < beta - razor_margin(depth)
853 && ttMove == MOVE_NONE
854 && !value_is_mate(beta)
855 && !pos.has_pawn_on_7th(pos.side_to_move()))
857 Value rbeta = beta - razor_margin(depth);
858 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
860 // Logically we should return (v + razor_margin(depth)), but
861 // surprisingly this did slightly weaker in tests.
865 // Step 7. Static null move pruning (is omitted in PV nodes)
866 // We're betting that the opponent doesn't have a move that will reduce
867 // the score by more than futility_margin(depth) if we do a null move.
870 && depth < RazorDepth
872 && refinedValue >= beta + futility_margin(depth, 0)
873 && !value_is_mate(beta)
874 && pos.non_pawn_material(pos.side_to_move()))
875 return refinedValue - futility_margin(depth, 0);
877 // Step 8. Null move search with verification search (is omitted in PV nodes)
882 && refinedValue >= beta
883 && !value_is_mate(beta)
884 && pos.non_pawn_material(pos.side_to_move()))
886 ss->currentMove = MOVE_NULL;
888 // Null move dynamic reduction based on depth
889 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
891 // Null move dynamic reduction based on value
892 if (refinedValue - beta > PawnValueMidgame)
895 pos.do_null_move(st);
896 (ss+1)->skipNullMove = true;
897 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
898 (ss+1)->skipNullMove = false;
899 pos.undo_null_move();
901 if (nullValue >= beta)
903 // Do not return unproven mate scores
904 if (nullValue >= value_mate_in(PLY_MAX))
907 if (depth < 6 * ONE_PLY)
910 // Do verification search at high depths
911 ss->skipNullMove = true;
912 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
913 ss->skipNullMove = false;
920 // The null move failed low, which means that we may be faced with
921 // some kind of threat. If the previous move was reduced, check if
922 // the move that refuted the null move was somehow connected to the
923 // move which was reduced. If a connection is found, return a fail
924 // low score (which will cause the reduced move to fail high in the
925 // parent node, which will trigger a re-search with full depth).
926 if (nullValue == value_mated_in(ply + 2))
929 threatMove = (ss+1)->bestMove;
930 if ( depth < ThreatDepth
932 && threatMove != MOVE_NONE
933 && connected_moves(pos, (ss-1)->currentMove, threatMove))
938 // Step 9. Internal iterative deepening
940 && depth >= IIDDepth[PvNode]
941 && ttMove == MOVE_NONE
942 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
944 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
946 ss->skipNullMove = true;
947 search<PvNode>(pos, ss, alpha, beta, d, ply);
948 ss->skipNullMove = false;
950 ttMove = ss->bestMove;
951 tte = TT.retrieve(posKey);
954 // Expensive mate threat detection (only for PV nodes)
955 if (PvNode && !Root) // FIXME
956 mateThreat = pos.has_mate_threat();
958 split_point_start: // At split points actual search starts from here
960 // Initialize a MovePicker object for the current position
961 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
962 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
963 MovePicker& mp = SpNode ? *sp->mp : mpBase;
965 ss->bestMove = MOVE_NONE;
966 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
967 futilityBase = ss->eval + ss->evalMargin;
968 singularExtensionNode = !Root
970 && depth >= SingularExtensionDepth[PvNode]
973 && !excludedMove // Do not allow recursive singular extension search
974 && (tte->type() & VALUE_TYPE_LOWER)
975 && tte->depth() >= depth - 3 * ONE_PLY;
984 lock_grab(&(sp->lock));
985 bestValue = sp->bestValue;
988 // Step 10. Loop through moves
989 // Loop through all legal moves until no moves remain or a beta cutoff occurs
990 while ( bestValue < beta
991 && (!Root || rm != Rml->end())
992 && ( Root || (move = mp.get_next_move()) != MOVE_NONE)
993 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
999 // This is used by time management
1000 FirstRootMove = (rm == Rml->begin());
1002 // Save the current node count before the move is searched
1003 nodes = pos.nodes_searched();
1005 // If it's time to send nodes info, do it here where we have the
1006 // correct accumulated node counts searched by each thread.
1007 if (SendSearchedNodes)
1009 SendSearchedNodes = false;
1010 cout << "info nodes " << nodes
1011 << " nps " << nps(pos)
1012 << " time " << current_search_time() << endl;
1015 if (current_search_time() >= 1000)
1016 cout << "info currmove " << move
1017 << " currmovenumber " << moveCount << endl;
1020 assert(move_is_ok(move));
1024 moveCount = ++sp->moveCount;
1025 lock_release(&(sp->lock));
1027 else if (move == excludedMove)
1030 movesSearched[moveCount++] = move;
1032 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1033 moveIsCheck = pos.move_is_check(move, ci);
1034 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1036 // Step 11. Decide the new search depth
1037 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1039 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1040 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1041 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1042 // lower then ttValue minus a margin then we extend ttMove.
1043 if ( singularExtensionNode
1044 && move == tte->move()
1047 Value ttValue = value_from_tt(tte->value(), ply);
1049 if (abs(ttValue) < VALUE_KNOWN_WIN)
1051 Value b = ttValue - SingularExtensionMargin;
1052 ss->excludedMove = move;
1053 ss->skipNullMove = true;
1054 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1055 ss->skipNullMove = false;
1056 ss->excludedMove = MOVE_NONE;
1057 ss->bestMove = MOVE_NONE;
1063 // Update current move (this must be done after singular extension search)
1064 ss->currentMove = move;
1065 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1067 // Step 12. Futility pruning (is omitted in PV nodes)
1069 && !captureOrPromotion
1073 && !move_is_castle(move))
1075 // Move count based pruning
1076 if ( moveCount >= futility_move_count(depth)
1077 && !(threatMove && connected_threat(pos, move, threatMove))
1078 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1081 lock_grab(&(sp->lock));
1086 // Value based pruning
1087 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1088 // but fixing this made program slightly weaker.
1089 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1090 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1091 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1093 if (futilityValueScaled < beta)
1097 lock_grab(&(sp->lock));
1098 if (futilityValueScaled > sp->bestValue)
1099 sp->bestValue = bestValue = futilityValueScaled;
1101 else if (futilityValueScaled > bestValue)
1102 bestValue = futilityValueScaled;
1107 // Prune moves with negative SEE at low depths
1108 if ( predictedDepth < 2 * ONE_PLY
1109 && bestValue > value_mated_in(PLY_MAX)
1110 && pos.see_sign(move) < 0)
1113 lock_grab(&(sp->lock));
1119 // Step 13. Make the move
1120 pos.do_move(move, st, ci, moveIsCheck);
1122 // Step extra. pv search (only in PV nodes)
1123 // The first move in list is the expected PV
1126 // Aspiration window is disabled in multi-pv case
1127 if (Root && MultiPV > 1)
1128 alpha = -VALUE_INFINITE;
1130 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1134 // Step 14. Reduced depth search
1135 // If the move fails high will be re-searched at full depth.
1136 bool doFullDepthSearch = true;
1138 if ( depth >= 3 * ONE_PLY
1139 && !captureOrPromotion
1141 && !move_is_castle(move)
1142 && ss->killers[0] != move
1143 && ss->killers[1] != move)
1145 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1146 : reduction<PvNode>(depth, moveCount);
1149 alpha = SpNode ? sp->alpha : alpha;
1150 Depth d = newDepth - ss->reduction;
1151 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1153 doFullDepthSearch = (value > alpha);
1155 ss->reduction = DEPTH_ZERO; // Restore original reduction
1158 // Step 15. Full depth search
1159 if (doFullDepthSearch)
1161 alpha = SpNode ? sp->alpha : alpha;
1162 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1164 // Step extra. pv search (only in PV nodes)
1165 // Search only for possible new PV nodes, if instead value >= beta then
1166 // parent node fails low with value <= alpha and tries another move.
1167 if (PvNode && value > alpha && (Root || value < beta))
1168 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1172 // Step 16. Undo move
1173 pos.undo_move(move);
1175 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1177 // Step 17. Check for new best move
1180 lock_grab(&(sp->lock));
1181 bestValue = sp->bestValue;
1185 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1190 sp->bestValue = value;
1194 if (PvNode && value < beta) // We want always alpha < beta
1202 sp->betaCutoff = true;
1204 if (value == value_mate_in(ply + 1))
1205 ss->mateKiller = move;
1207 ss->bestMove = move;
1210 sp->parentSstack->bestMove = move;
1216 // Finished searching the move. If StopRequest is true, the search
1217 // was aborted because the user interrupted the search or because we
1218 // ran out of time. In this case, the return value of the search cannot
1219 // be trusted, and we break out of the loop without updating the best
1224 // Remember searched nodes counts for this move
1225 rm->nodes += pos.nodes_searched() - nodes;
1227 // Step 17. Check for new best move
1228 if (!isPvMove && value <= alpha)
1229 rm->pv_score = -VALUE_INFINITE;
1232 // PV move or new best move!
1235 ss->bestMove = move;
1236 rm->pv_score = value;
1237 rm->extract_pv_from_tt(pos);
1239 // We record how often the best move has been changed in each
1240 // iteration. This information is used for time managment: When
1241 // the best move changes frequently, we allocate some more time.
1242 if (!isPvMove && MultiPV == 1)
1243 BestMoveChangesByIteration[Iteration]++;
1245 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1246 // requires we send all the PV lines properly sorted.
1247 Rml->sort_multipv(moveCount);
1249 for (int j = 0; j < Min(MultiPV, (int)Rml->size()); j++)
1250 cout << (*Rml)[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
1252 // Update alpha. In multi-pv we don't use aspiration window
1255 // Raise alpha to setup proper non-pv search upper bound
1257 alpha = bestValue = value;
1259 else // Set alpha equal to minimum score among the PV lines
1260 alpha = bestValue = (*Rml)[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1262 } // PV move or new best move
1267 // Step 18. Check for split
1270 && depth >= ThreadsMgr.min_split_depth()
1271 && ThreadsMgr.active_threads() > 1
1273 && ThreadsMgr.available_thread_exists(threadID)
1275 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1277 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1278 threatMove, mateThreat, moveCount, &mp, PvNode);
1281 // Step 19. Check for mate and stalemate
1282 // All legal moves have been searched and if there are
1283 // no legal moves, it must be mate or stalemate.
1284 // If one move was excluded return fail low score.
1285 if (!SpNode && !moveCount)
1286 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1288 // Step 20. Update tables
1289 // If the search is not aborted, update the transposition table,
1290 // history counters, and killer moves.
1291 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1293 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1294 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1295 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1297 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1299 // Update killers and history only for non capture moves that fails high
1300 if ( bestValue >= beta
1301 && !pos.move_is_capture_or_promotion(move))
1303 update_history(pos, move, depth, movesSearched, moveCount);
1304 update_killers(move, ss->killers);
1310 // Here we have the lock still grabbed
1311 sp->slaves[threadID] = 0;
1312 sp->nodes += pos.nodes_searched();
1313 lock_release(&(sp->lock));
1316 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1321 // qsearch() is the quiescence search function, which is called by the main
1322 // search function when the remaining depth is zero (or, to be more precise,
1323 // less than ONE_PLY).
1325 template <NodeType PvNode>
1326 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1328 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1329 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1330 assert(PvNode || alpha == beta - 1);
1332 assert(ply > 0 && ply < PLY_MAX);
1333 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1337 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1338 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1341 Value oldAlpha = alpha;
1343 ss->bestMove = ss->currentMove = MOVE_NONE;
1345 // Check for an instant draw or maximum ply reached
1346 if (pos.is_draw() || ply >= PLY_MAX - 1)
1349 // Decide whether or not to include checks, this fixes also the type of
1350 // TT entry depth that we are going to use. Note that in qsearch we use
1351 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1352 isCheck = pos.is_check();
1353 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1355 // Transposition table lookup. At PV nodes, we don't use the TT for
1356 // pruning, but only for move ordering.
1357 tte = TT.retrieve(pos.get_key());
1358 ttMove = (tte ? tte->move() : MOVE_NONE);
1360 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1362 ss->bestMove = ttMove; // Can be MOVE_NONE
1363 return value_from_tt(tte->value(), ply);
1366 // Evaluate the position statically
1369 bestValue = futilityBase = -VALUE_INFINITE;
1370 ss->eval = evalMargin = VALUE_NONE;
1371 enoughMaterial = false;
1377 assert(tte->static_value() != VALUE_NONE);
1379 evalMargin = tte->static_value_margin();
1380 ss->eval = bestValue = tte->static_value();
1383 ss->eval = bestValue = evaluate(pos, evalMargin);
1385 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1387 // Stand pat. Return immediately if static value is at least beta
1388 if (bestValue >= beta)
1391 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1396 if (PvNode && bestValue > alpha)
1399 // Futility pruning parameters, not needed when in check
1400 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1401 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1404 // Initialize a MovePicker object for the current position, and prepare
1405 // to search the moves. Because the depth is <= 0 here, only captures,
1406 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1408 MovePicker mp(pos, ttMove, depth, H);
1411 // Loop through the moves until no moves remain or a beta cutoff occurs
1412 while ( alpha < beta
1413 && (move = mp.get_next_move()) != MOVE_NONE)
1415 assert(move_is_ok(move));
1417 moveIsCheck = pos.move_is_check(move, ci);
1425 && !move_is_promotion(move)
1426 && !pos.move_is_passed_pawn_push(move))
1428 futilityValue = futilityBase
1429 + pos.endgame_value_of_piece_on(move_to(move))
1430 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1432 if (futilityValue < alpha)
1434 if (futilityValue > bestValue)
1435 bestValue = futilityValue;
1440 // Detect non-capture evasions that are candidate to be pruned
1441 evasionPrunable = isCheck
1442 && bestValue > value_mated_in(PLY_MAX)
1443 && !pos.move_is_capture(move)
1444 && !pos.can_castle(pos.side_to_move());
1446 // Don't search moves with negative SEE values
1448 && (!isCheck || evasionPrunable)
1450 && !move_is_promotion(move)
1451 && pos.see_sign(move) < 0)
1454 // Don't search useless checks
1459 && !pos.move_is_capture_or_promotion(move)
1460 && ss->eval + PawnValueMidgame / 4 < beta
1461 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1463 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1464 bestValue = ss->eval + PawnValueMidgame / 4;
1469 // Update current move
1470 ss->currentMove = move;
1472 // Make and search the move
1473 pos.do_move(move, st, ci, moveIsCheck);
1474 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1475 pos.undo_move(move);
1477 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1480 if (value > bestValue)
1486 ss->bestMove = move;
1491 // All legal moves have been searched. A special case: If we're in check
1492 // and no legal moves were found, it is checkmate.
1493 if (isCheck && bestValue == -VALUE_INFINITE)
1494 return value_mated_in(ply);
1496 // Update transposition table
1497 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1498 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1500 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1506 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1507 // bestValue is updated only when returning false because in that case move
1510 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1512 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1513 Square from, to, ksq, victimSq;
1516 Value futilityValue, bv = *bestValue;
1518 from = move_from(move);
1520 them = opposite_color(pos.side_to_move());
1521 ksq = pos.king_square(them);
1522 kingAtt = pos.attacks_from<KING>(ksq);
1523 pc = pos.piece_on(from);
1525 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1526 oldAtt = pos.attacks_from(pc, from, occ);
1527 newAtt = pos.attacks_from(pc, to, occ);
1529 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1530 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1532 if (!(b && (b & (b - 1))))
1535 // Rule 2. Queen contact check is very dangerous
1536 if ( type_of_piece(pc) == QUEEN
1537 && bit_is_set(kingAtt, to))
1540 // Rule 3. Creating new double threats with checks
1541 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1545 victimSq = pop_1st_bit(&b);
1546 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1548 // Note that here we generate illegal "double move"!
1549 if ( futilityValue >= beta
1550 && pos.see_sign(make_move(from, victimSq)) >= 0)
1553 if (futilityValue > bv)
1557 // Update bestValue only if check is not dangerous (because we will prune the move)
1563 // connected_moves() tests whether two moves are 'connected' in the sense
1564 // that the first move somehow made the second move possible (for instance
1565 // if the moving piece is the same in both moves). The first move is assumed
1566 // to be the move that was made to reach the current position, while the
1567 // second move is assumed to be a move from the current position.
1569 bool connected_moves(const Position& pos, Move m1, Move m2) {
1571 Square f1, t1, f2, t2;
1574 assert(m1 && move_is_ok(m1));
1575 assert(m2 && move_is_ok(m2));
1577 // Case 1: The moving piece is the same in both moves
1583 // Case 2: The destination square for m2 was vacated by m1
1589 // Case 3: Moving through the vacated square
1590 if ( piece_is_slider(pos.piece_on(f2))
1591 && bit_is_set(squares_between(f2, t2), f1))
1594 // Case 4: The destination square for m2 is defended by the moving piece in m1
1595 p = pos.piece_on(t1);
1596 if (bit_is_set(pos.attacks_from(p, t1), t2))
1599 // Case 5: Discovered check, checking piece is the piece moved in m1
1600 if ( piece_is_slider(p)
1601 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1602 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1604 // discovered_check_candidates() works also if the Position's side to
1605 // move is the opposite of the checking piece.
1606 Color them = opposite_color(pos.side_to_move());
1607 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1609 if (bit_is_set(dcCandidates, f2))
1616 // value_is_mate() checks if the given value is a mate one eventually
1617 // compensated for the ply.
1619 bool value_is_mate(Value value) {
1621 assert(abs(value) <= VALUE_INFINITE);
1623 return value <= value_mated_in(PLY_MAX)
1624 || value >= value_mate_in(PLY_MAX);
1628 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1629 // "plies to mate from the current ply". Non-mate scores are unchanged.
1630 // The function is called before storing a value to the transposition table.
1632 Value value_to_tt(Value v, int ply) {
1634 if (v >= value_mate_in(PLY_MAX))
1637 if (v <= value_mated_in(PLY_MAX))
1644 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1645 // the transposition table to a mate score corrected for the current ply.
1647 Value value_from_tt(Value v, int ply) {
1649 if (v >= value_mate_in(PLY_MAX))
1652 if (v <= value_mated_in(PLY_MAX))
1659 // extension() decides whether a move should be searched with normal depth,
1660 // or with extended depth. Certain classes of moves (checking moves, in
1661 // particular) are searched with bigger depth than ordinary moves and in
1662 // any case are marked as 'dangerous'. Note that also if a move is not
1663 // extended, as example because the corresponding UCI option is set to zero,
1664 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1665 template <NodeType PvNode>
1666 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1667 bool singleEvasion, bool mateThreat, bool* dangerous) {
1669 assert(m != MOVE_NONE);
1671 Depth result = DEPTH_ZERO;
1672 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1676 if (moveIsCheck && pos.see_sign(m) >= 0)
1677 result += CheckExtension[PvNode];
1680 result += SingleEvasionExtension[PvNode];
1683 result += MateThreatExtension[PvNode];
1686 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1688 Color c = pos.side_to_move();
1689 if (relative_rank(c, move_to(m)) == RANK_7)
1691 result += PawnPushTo7thExtension[PvNode];
1694 if (pos.pawn_is_passed(c, move_to(m)))
1696 result += PassedPawnExtension[PvNode];
1701 if ( captureOrPromotion
1702 && pos.type_of_piece_on(move_to(m)) != PAWN
1703 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1704 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1705 && !move_is_promotion(m)
1708 result += PawnEndgameExtension[PvNode];
1713 && captureOrPromotion
1714 && pos.type_of_piece_on(move_to(m)) != PAWN
1715 && pos.see_sign(m) >= 0)
1717 result += ONE_PLY / 2;
1721 return Min(result, ONE_PLY);
1725 // connected_threat() tests whether it is safe to forward prune a move or if
1726 // is somehow coonected to the threat move returned by null search.
1728 bool connected_threat(const Position& pos, Move m, Move threat) {
1730 assert(move_is_ok(m));
1731 assert(threat && move_is_ok(threat));
1732 assert(!pos.move_is_check(m));
1733 assert(!pos.move_is_capture_or_promotion(m));
1734 assert(!pos.move_is_passed_pawn_push(m));
1736 Square mfrom, mto, tfrom, tto;
1738 mfrom = move_from(m);
1740 tfrom = move_from(threat);
1741 tto = move_to(threat);
1743 // Case 1: Don't prune moves which move the threatened piece
1747 // Case 2: If the threatened piece has value less than or equal to the
1748 // value of the threatening piece, don't prune move which defend it.
1749 if ( pos.move_is_capture(threat)
1750 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1751 || pos.type_of_piece_on(tfrom) == KING)
1752 && pos.move_attacks_square(m, tto))
1755 // Case 3: If the moving piece in the threatened move is a slider, don't
1756 // prune safe moves which block its ray.
1757 if ( piece_is_slider(pos.piece_on(tfrom))
1758 && bit_is_set(squares_between(tfrom, tto), mto)
1759 && pos.see_sign(m) >= 0)
1766 // ok_to_use_TT() returns true if a transposition table score
1767 // can be used at a given point in search.
1769 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1771 Value v = value_from_tt(tte->value(), ply);
1773 return ( tte->depth() >= depth
1774 || v >= Max(value_mate_in(PLY_MAX), beta)
1775 || v < Min(value_mated_in(PLY_MAX), beta))
1777 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1778 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1782 // refine_eval() returns the transposition table score if
1783 // possible otherwise falls back on static position evaluation.
1785 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1789 Value v = value_from_tt(tte->value(), ply);
1791 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1792 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1799 // update_history() registers a good move that produced a beta-cutoff
1800 // in history and marks as failures all the other moves of that ply.
1802 void update_history(const Position& pos, Move move, Depth depth,
1803 Move movesSearched[], int moveCount) {
1805 Value bonus = Value(int(depth) * int(depth));
1807 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1809 for (int i = 0; i < moveCount - 1; i++)
1811 m = movesSearched[i];
1815 if (!pos.move_is_capture_or_promotion(m))
1816 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1821 // update_killers() add a good move that produced a beta-cutoff
1822 // among the killer moves of that ply.
1824 void update_killers(Move m, Move killers[]) {
1826 if (m == killers[0])
1829 killers[1] = killers[0];
1834 // update_gains() updates the gains table of a non-capture move given
1835 // the static position evaluation before and after the move.
1837 void update_gains(const Position& pos, Move m, Value before, Value after) {
1840 && before != VALUE_NONE
1841 && after != VALUE_NONE
1842 && pos.captured_piece_type() == PIECE_TYPE_NONE
1843 && !move_is_special(m))
1844 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1848 // init_ss_array() does a fast reset of the first entries of a SearchStack
1849 // array and of all the excludedMove and skipNullMove entries.
1851 void init_ss_array(SearchStack* ss, int size) {
1853 for (int i = 0; i < size; i++, ss++)
1855 ss->excludedMove = MOVE_NONE;
1856 ss->skipNullMove = false;
1857 ss->reduction = DEPTH_ZERO;
1861 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1866 // value_to_uci() converts a value to a string suitable for use with the UCI
1867 // protocol specifications:
1869 // cp <x> The score from the engine's point of view in centipawns.
1870 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1871 // use negative values for y.
1873 std::string value_to_uci(Value v) {
1875 std::stringstream s;
1877 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1878 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1880 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1886 // current_search_time() returns the number of milliseconds which have passed
1887 // since the beginning of the current search.
1889 int current_search_time() {
1891 return get_system_time() - SearchStartTime;
1895 // nps() computes the current nodes/second count
1897 int nps(const Position& pos) {
1899 int t = current_search_time();
1900 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1904 // poll() performs two different functions: It polls for user input, and it
1905 // looks at the time consumed so far and decides if it's time to abort the
1908 void poll(const Position& pos) {
1910 static int lastInfoTime;
1911 int t = current_search_time();
1914 if (input_available())
1916 // We are line oriented, don't read single chars
1917 std::string command;
1919 if (!std::getline(std::cin, command))
1922 if (command == "quit")
1924 // Quit the program as soon as possible
1926 QuitRequest = StopRequest = true;
1929 else if (command == "stop")
1931 // Stop calculating as soon as possible, but still send the "bestmove"
1932 // and possibly the "ponder" token when finishing the search.
1936 else if (command == "ponderhit")
1938 // The opponent has played the expected move. GUI sends "ponderhit" if
1939 // we were told to ponder on the same move the opponent has played. We
1940 // should continue searching but switching from pondering to normal search.
1943 if (StopOnPonderhit)
1948 // Print search information
1952 else if (lastInfoTime > t)
1953 // HACK: Must be a new search where we searched less than
1954 // NodesBetweenPolls nodes during the first second of search.
1957 else if (t - lastInfoTime >= 1000)
1964 if (dbg_show_hit_rate)
1965 dbg_print_hit_rate();
1967 // Send info on searched nodes as soon as we return to root
1968 SendSearchedNodes = true;
1971 // Should we stop the search?
1975 bool stillAtFirstMove = FirstRootMove
1976 && !AspirationFailLow
1977 && t > TimeMgr.available_time();
1979 bool noMoreTime = t > TimeMgr.maximum_time()
1980 || stillAtFirstMove;
1982 if ( (UseTimeManagement && noMoreTime)
1983 || (ExactMaxTime && t >= ExactMaxTime)
1984 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1989 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1990 // while the program is pondering. The point is to work around a wrinkle in
1991 // the UCI protocol: When pondering, the engine is not allowed to give a
1992 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1993 // We simply wait here until one of these commands is sent, and return,
1994 // after which the bestmove and pondermove will be printed.
1996 void wait_for_stop_or_ponderhit() {
1998 std::string command;
2002 // Wait for a command from stdin
2003 if (!std::getline(std::cin, command))
2006 if (command == "quit")
2011 else if (command == "ponderhit" || command == "stop")
2017 // init_thread() is the function which is called when a new thread is
2018 // launched. It simply calls the idle_loop() function with the supplied
2019 // threadID. There are two versions of this function; one for POSIX
2020 // threads and one for Windows threads.
2022 #if !defined(_MSC_VER)
2024 void* init_thread(void* threadID) {
2026 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2032 DWORD WINAPI init_thread(LPVOID threadID) {
2034 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2041 /// The ThreadsManager class
2044 // read_uci_options() updates number of active threads and other internal
2045 // parameters according to the UCI options values. It is called before
2046 // to start a new search.
2048 void ThreadsManager::read_uci_options() {
2050 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2051 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2052 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2053 activeThreads = Options["Threads"].value<int>();
2057 // idle_loop() is where the threads are parked when they have no work to do.
2058 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2059 // object for which the current thread is the master.
2061 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2063 assert(threadID >= 0 && threadID < MAX_THREADS);
2066 bool allFinished = false;
2070 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2071 // master should exit as last one.
2072 if (allThreadsShouldExit)
2075 threads[threadID].state = THREAD_TERMINATED;
2079 // If we are not thinking, wait for a condition to be signaled
2080 // instead of wasting CPU time polling for work.
2081 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2082 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2084 assert(!sp || useSleepingThreads);
2085 assert(threadID != 0 || useSleepingThreads);
2087 if (threads[threadID].state == THREAD_INITIALIZING)
2088 threads[threadID].state = THREAD_AVAILABLE;
2090 // Grab the lock to avoid races with wake_sleeping_thread()
2091 lock_grab(&sleepLock[threadID]);
2093 // If we are master and all slaves have finished do not go to sleep
2094 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2095 allFinished = (i == activeThreads);
2097 if (allFinished || allThreadsShouldExit)
2099 lock_release(&sleepLock[threadID]);
2103 // Do sleep here after retesting sleep conditions
2104 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2105 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2107 lock_release(&sleepLock[threadID]);
2110 // If this thread has been assigned work, launch a search
2111 if (threads[threadID].state == THREAD_WORKISWAITING)
2113 assert(!allThreadsShouldExit);
2115 threads[threadID].state = THREAD_SEARCHING;
2117 // Here we call search() with SplitPoint template parameter set to true
2118 SplitPoint* tsp = threads[threadID].splitPoint;
2119 Position pos(*tsp->pos, threadID);
2120 SearchStack* ss = tsp->sstack[threadID] + 1;
2124 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2126 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2128 assert(threads[threadID].state == THREAD_SEARCHING);
2130 threads[threadID].state = THREAD_AVAILABLE;
2132 // Wake up master thread so to allow it to return from the idle loop in
2133 // case we are the last slave of the split point.
2134 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2135 wake_sleeping_thread(tsp->master);
2138 // If this thread is the master of a split point and all slaves have
2139 // finished their work at this split point, return from the idle loop.
2140 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2141 allFinished = (i == activeThreads);
2145 // Because sp->slaves[] is reset under lock protection,
2146 // be sure sp->lock has been released before to return.
2147 lock_grab(&(sp->lock));
2148 lock_release(&(sp->lock));
2150 // In helpful master concept a master can help only a sub-tree, and
2151 // because here is all finished is not possible master is booked.
2152 assert(threads[threadID].state == THREAD_AVAILABLE);
2154 threads[threadID].state = THREAD_SEARCHING;
2161 // init_threads() is called during startup. It launches all helper threads,
2162 // and initializes the split point stack and the global locks and condition
2165 void ThreadsManager::init_threads() {
2167 int i, arg[MAX_THREADS];
2170 // Initialize global locks
2173 for (i = 0; i < MAX_THREADS; i++)
2175 lock_init(&sleepLock[i]);
2176 cond_init(&sleepCond[i]);
2179 // Initialize splitPoints[] locks
2180 for (i = 0; i < MAX_THREADS; i++)
2181 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2182 lock_init(&(threads[i].splitPoints[j].lock));
2184 // Will be set just before program exits to properly end the threads
2185 allThreadsShouldExit = false;
2187 // Threads will be put all threads to sleep as soon as created
2190 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2191 threads[0].state = THREAD_SEARCHING;
2192 for (i = 1; i < MAX_THREADS; i++)
2193 threads[i].state = THREAD_INITIALIZING;
2195 // Launch the helper threads
2196 for (i = 1; i < MAX_THREADS; i++)
2200 #if !defined(_MSC_VER)
2201 pthread_t pthread[1];
2202 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2203 pthread_detach(pthread[0]);
2205 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2209 cout << "Failed to create thread number " << i << endl;
2213 // Wait until the thread has finished launching and is gone to sleep
2214 while (threads[i].state == THREAD_INITIALIZING) {}
2219 // exit_threads() is called when the program exits. It makes all the
2220 // helper threads exit cleanly.
2222 void ThreadsManager::exit_threads() {
2224 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2226 // Wake up all the threads and waits for termination
2227 for (int i = 1; i < MAX_THREADS; i++)
2229 wake_sleeping_thread(i);
2230 while (threads[i].state != THREAD_TERMINATED) {}
2233 // Now we can safely destroy the locks
2234 for (int i = 0; i < MAX_THREADS; i++)
2235 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2236 lock_destroy(&(threads[i].splitPoints[j].lock));
2238 lock_destroy(&mpLock);
2240 // Now we can safely destroy the wait conditions
2241 for (int i = 0; i < MAX_THREADS; i++)
2243 lock_destroy(&sleepLock[i]);
2244 cond_destroy(&sleepCond[i]);
2249 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2250 // the thread's currently active split point, or in some ancestor of
2251 // the current split point.
2253 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2255 assert(threadID >= 0 && threadID < activeThreads);
2257 SplitPoint* sp = threads[threadID].splitPoint;
2259 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2264 // thread_is_available() checks whether the thread with threadID "slave" is
2265 // available to help the thread with threadID "master" at a split point. An
2266 // obvious requirement is that "slave" must be idle. With more than two
2267 // threads, this is not by itself sufficient: If "slave" is the master of
2268 // some active split point, it is only available as a slave to the other
2269 // threads which are busy searching the split point at the top of "slave"'s
2270 // split point stack (the "helpful master concept" in YBWC terminology).
2272 bool ThreadsManager::thread_is_available(int slave, int master) const {
2274 assert(slave >= 0 && slave < activeThreads);
2275 assert(master >= 0 && master < activeThreads);
2276 assert(activeThreads > 1);
2278 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2281 // Make a local copy to be sure doesn't change under our feet
2282 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2284 // No active split points means that the thread is available as
2285 // a slave for any other thread.
2286 if (localActiveSplitPoints == 0 || activeThreads == 2)
2289 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2290 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2291 // could have been set to 0 by another thread leading to an out of bound access.
2292 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2299 // available_thread_exists() tries to find an idle thread which is available as
2300 // a slave for the thread with threadID "master".
2302 bool ThreadsManager::available_thread_exists(int master) const {
2304 assert(master >= 0 && master < activeThreads);
2305 assert(activeThreads > 1);
2307 for (int i = 0; i < activeThreads; i++)
2308 if (thread_is_available(i, master))
2315 // split() does the actual work of distributing the work at a node between
2316 // several available threads. If it does not succeed in splitting the
2317 // node (because no idle threads are available, or because we have no unused
2318 // split point objects), the function immediately returns. If splitting is
2319 // possible, a SplitPoint object is initialized with all the data that must be
2320 // copied to the helper threads and we tell our helper threads that they have
2321 // been assigned work. This will cause them to instantly leave their idle loops and
2322 // call search().When all threads have returned from search() then split() returns.
2324 template <bool Fake>
2325 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2326 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2327 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2328 assert(pos.is_ok());
2329 assert(ply > 0 && ply < PLY_MAX);
2330 assert(*bestValue >= -VALUE_INFINITE);
2331 assert(*bestValue <= *alpha);
2332 assert(*alpha < beta);
2333 assert(beta <= VALUE_INFINITE);
2334 assert(depth > DEPTH_ZERO);
2335 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2336 assert(activeThreads > 1);
2338 int i, master = pos.thread();
2339 Thread& masterThread = threads[master];
2343 // If no other thread is available to help us, or if we have too many
2344 // active split points, don't split.
2345 if ( !available_thread_exists(master)
2346 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2348 lock_release(&mpLock);
2352 // Pick the next available split point object from the split point stack
2353 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2355 // Initialize the split point object
2356 splitPoint.parent = masterThread.splitPoint;
2357 splitPoint.master = master;
2358 splitPoint.betaCutoff = false;
2359 splitPoint.ply = ply;
2360 splitPoint.depth = depth;
2361 splitPoint.threatMove = threatMove;
2362 splitPoint.mateThreat = mateThreat;
2363 splitPoint.alpha = *alpha;
2364 splitPoint.beta = beta;
2365 splitPoint.pvNode = pvNode;
2366 splitPoint.bestValue = *bestValue;
2368 splitPoint.moveCount = moveCount;
2369 splitPoint.pos = &pos;
2370 splitPoint.nodes = 0;
2371 splitPoint.parentSstack = ss;
2372 for (i = 0; i < activeThreads; i++)
2373 splitPoint.slaves[i] = 0;
2375 masterThread.splitPoint = &splitPoint;
2377 // If we are here it means we are not available
2378 assert(masterThread.state != THREAD_AVAILABLE);
2380 int workersCnt = 1; // At least the master is included
2382 // Allocate available threads setting state to THREAD_BOOKED
2383 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2384 if (thread_is_available(i, master))
2386 threads[i].state = THREAD_BOOKED;
2387 threads[i].splitPoint = &splitPoint;
2388 splitPoint.slaves[i] = 1;
2392 assert(Fake || workersCnt > 1);
2394 // We can release the lock because slave threads are already booked and master is not available
2395 lock_release(&mpLock);
2397 // Tell the threads that they have work to do. This will make them leave
2398 // their idle loop. But before copy search stack tail for each thread.
2399 for (i = 0; i < activeThreads; i++)
2400 if (i == master || splitPoint.slaves[i])
2402 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2404 assert(i == master || threads[i].state == THREAD_BOOKED);
2406 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2408 if (useSleepingThreads && i != master)
2409 wake_sleeping_thread(i);
2412 // Everything is set up. The master thread enters the idle loop, from
2413 // which it will instantly launch a search, because its state is
2414 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2415 // idle loop, which means that the main thread will return from the idle
2416 // loop when all threads have finished their work at this split point.
2417 idle_loop(master, &splitPoint);
2419 // We have returned from the idle loop, which means that all threads are
2420 // finished. Update alpha and bestValue, and return.
2423 *alpha = splitPoint.alpha;
2424 *bestValue = splitPoint.bestValue;
2425 masterThread.activeSplitPoints--;
2426 masterThread.splitPoint = splitPoint.parent;
2427 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2429 lock_release(&mpLock);
2433 // wake_sleeping_thread() wakes up the thread with the given threadID
2434 // when it is time to start a new search.
2436 void ThreadsManager::wake_sleeping_thread(int threadID) {
2438 lock_grab(&sleepLock[threadID]);
2439 cond_signal(&sleepCond[threadID]);
2440 lock_release(&sleepLock[threadID]);
2444 /// RootMove and RootMoveList method's definitions
2446 RootMove::RootMove() {
2449 pv_score = non_pv_score = -VALUE_INFINITE;
2453 RootMove& RootMove::operator=(const RootMove& rm) {
2455 const Move* src = rm.pv;
2458 // Avoid a costly full rm.pv[] copy
2459 do *dst++ = *src; while (*src++ != MOVE_NONE);
2462 pv_score = rm.pv_score;
2463 non_pv_score = rm.non_pv_score;
2467 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2468 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2469 // allow to always have a ponder move even when we fail high at root and also a
2470 // long PV to print that is important for position analysis.
2472 void RootMove::extract_pv_from_tt(Position& pos) {
2474 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2478 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2480 pos.do_move(pv[0], *st++);
2482 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2483 && tte->move() != MOVE_NONE
2484 && move_is_legal(pos, tte->move())
2486 && (!pos.is_draw() || ply < 2))
2488 pv[ply] = tte->move();
2489 pos.do_move(pv[ply++], *st++);
2491 pv[ply] = MOVE_NONE;
2493 do pos.undo_move(pv[--ply]); while (ply);
2496 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2497 // the PV back into the TT. This makes sure the old PV moves are searched
2498 // first, even if the old TT entries have been overwritten.
2500 void RootMove::insert_pv_in_tt(Position& pos) {
2502 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2505 Value v, m = VALUE_NONE;
2508 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2512 tte = TT.retrieve(k);
2514 // Don't overwrite exsisting correct entries
2515 if (!tte || tte->move() != pv[ply])
2517 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2518 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2520 pos.do_move(pv[ply], *st++);
2522 } while (pv[++ply] != MOVE_NONE);
2524 do pos.undo_move(pv[--ply]); while (ply);
2527 // pv_info_to_uci() returns a string with information on the current PV line
2528 // formatted according to UCI specification and eventually writes the info
2529 // to a log file. It is called at each iteration or after a new pv is found.
2531 std::string RootMove::pv_info_to_uci(Position& pos, Value alpha, Value beta, int pvLine) {
2533 std::stringstream s, l;
2536 while (*m != MOVE_NONE)
2539 s << "info depth " << Iteration // FIXME
2540 << " seldepth " << int(m - pv)
2541 << " multipv " << pvLine + 1
2542 << " score " << value_to_uci(pv_score)
2543 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2544 << " time " << current_search_time()
2545 << " nodes " << pos.nodes_searched()
2546 << " nps " << nps(pos)
2547 << " pv " << l.str();
2549 if (UseLogFile && pvLine == 0)
2551 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2552 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2554 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2560 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2562 SearchStack ss[PLY_MAX_PLUS_2];
2563 MoveStack mlist[MOVES_MAX];
2567 // Initialize search stack
2568 init_ss_array(ss, PLY_MAX_PLUS_2);
2569 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2571 // Generate all legal moves
2572 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2574 // Add each move to the RootMoveList's vector
2575 for (MoveStack* cur = mlist; cur != last; cur++)
2577 // If we have a searchMoves[] list then verify cur->move
2578 // is in the list before to add it.
2579 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2581 if (searchMoves[0] && *sm != cur->move)
2584 // Find a quick score for the move and add to the list
2585 pos.do_move(cur->move, st);
2588 rm.pv[0] = ss[0].currentMove = cur->move;
2589 rm.pv[1] = MOVE_NONE;
2590 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2593 pos.undo_move(cur->move);
2598 // Score root moves using the standard way used in main search, the moves
2599 // are scored according to the order in which are returned by MovePicker.
2600 // This is the second order score that is used to compare the moves when
2601 // the first order pv scores of both moves are equal.
2603 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2606 Value score = VALUE_ZERO;
2607 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2609 while ((move = mp.get_next_move()) != MOVE_NONE)
2610 for (Base::iterator it = begin(); it != end(); ++it)
2611 if (it->pv[0] == move)
2613 it->non_pv_score = score--;