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);
292 Value root_search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, RootMoveList& rml);
294 template <NodeType PvNode, bool SpNode, bool Root>
295 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
297 template <NodeType PvNode>
298 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
300 template <NodeType PvNode>
301 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
303 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
304 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
307 template <NodeType PvNode>
308 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
310 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
311 bool connected_moves(const Position& pos, Move m1, Move m2);
312 bool value_is_mate(Value value);
313 Value value_to_tt(Value v, int ply);
314 Value value_from_tt(Value v, int ply);
315 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
316 bool connected_threat(const Position& pos, Move m, Move threat);
317 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
318 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
319 void update_killers(Move m, Move killers[]);
320 void update_gains(const Position& pos, Move move, Value before, Value after);
322 int current_search_time();
323 std::string value_to_uci(Value v);
324 int nps(const Position& pos);
325 void poll(const Position& pos);
326 void wait_for_stop_or_ponderhit();
327 void init_ss_array(SearchStack* ss, int size);
329 #if !defined(_MSC_VER)
330 void* init_thread(void* threadID);
332 DWORD WINAPI init_thread(LPVOID threadID);
342 /// init_threads(), exit_threads() and nodes_searched() are helpers to
343 /// give accessibility to some TM methods from outside of current file.
345 void init_threads() { ThreadsMgr.init_threads(); }
346 void exit_threads() { ThreadsMgr.exit_threads(); }
349 /// init_search() is called during startup. It initializes various lookup tables
353 int d; // depth (ONE_PLY == 2)
354 int hd; // half depth (ONE_PLY == 1)
357 // Init reductions array
358 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
360 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
361 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
362 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
363 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
366 // Init futility margins array
367 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
368 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
370 // Init futility move count array
371 for (d = 0; d < 32; d++)
372 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
376 /// perft() is our utility to verify move generation is bug free. All the legal
377 /// moves up to given depth are generated and counted and the sum returned.
379 int64_t perft(Position& pos, Depth depth)
381 MoveStack mlist[MOVES_MAX];
386 // Generate all legal moves
387 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
389 // If we are at the last ply we don't need to do and undo
390 // the moves, just to count them.
391 if (depth <= ONE_PLY)
392 return int(last - mlist);
394 // Loop through all legal moves
396 for (MoveStack* cur = mlist; cur != last; cur++)
399 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
400 sum += perft(pos, depth - ONE_PLY);
407 /// think() is the external interface to Stockfish's search, and is called when
408 /// the program receives the UCI 'go' command. It initializes various
409 /// search-related global variables, and calls root_search(). It returns false
410 /// when a quit command is received during the search.
412 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
413 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
415 // Initialize global search variables
416 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
418 SearchStartTime = get_system_time();
419 ExactMaxTime = maxTime;
422 InfiniteSearch = infinite;
424 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
426 // Look for a book move, only during games, not tests
427 if (UseTimeManagement && Options["OwnBook"].value<bool>())
429 if (Options["Book File"].value<std::string>() != OpeningBook.name())
430 OpeningBook.open(Options["Book File"].value<std::string>());
432 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
433 if (bookMove != MOVE_NONE)
436 wait_for_stop_or_ponderhit();
438 cout << "bestmove " << bookMove << endl;
443 // Read UCI option values
444 TT.set_size(Options["Hash"].value<int>());
445 if (Options["Clear Hash"].value<bool>())
447 Options["Clear Hash"].set_value("false");
451 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
452 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
453 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
454 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
455 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
456 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
457 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
458 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
459 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
460 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
461 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
462 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
463 MultiPV = Options["MultiPV"].value<int>();
464 UseLogFile = Options["Use Search Log"].value<bool>();
466 read_evaluation_uci_options(pos.side_to_move());
468 // Set the number of active threads
469 ThreadsMgr.read_uci_options();
470 init_eval(ThreadsMgr.active_threads());
472 // Wake up needed threads
473 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
474 ThreadsMgr.wake_sleeping_thread(i);
477 int myTime = time[pos.side_to_move()];
478 int myIncrement = increment[pos.side_to_move()];
479 if (UseTimeManagement)
480 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
482 // Set best NodesBetweenPolls interval to avoid lagging under
483 // heavy time pressure.
485 NodesBetweenPolls = Min(MaxNodes, 30000);
486 else if (myTime && myTime < 1000)
487 NodesBetweenPolls = 1000;
488 else if (myTime && myTime < 5000)
489 NodesBetweenPolls = 5000;
491 NodesBetweenPolls = 30000;
493 // Write search information to log file
496 std::string name = Options["Search Log Filename"].value<std::string>();
497 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
499 LogFile << "Searching: " << pos.to_fen()
500 << "\ninfinite: " << infinite
501 << " ponder: " << ponder
502 << " time: " << myTime
503 << " increment: " << myIncrement
504 << " moves to go: " << movesToGo << endl;
507 // We're ready to start thinking. Call the iterative deepening loop function
508 Move ponderMove = MOVE_NONE;
509 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
511 // Print final search statistics
512 cout << "info nodes " << pos.nodes_searched()
513 << " nps " << nps(pos)
514 << " time " << current_search_time() << endl;
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
528 // Return from think() with unchanged position
529 pos.undo_move(bestMove);
534 // This makes all the threads to go to sleep
535 ThreadsMgr.set_active_threads(1);
537 // If we are pondering or in infinite search, we shouldn't print the
538 // best move before we are told to do so.
539 if (!StopRequest && (Pondering || InfiniteSearch))
540 wait_for_stop_or_ponderhit();
542 // Could be both MOVE_NONE when searching on a stalemate position
543 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
551 // id_loop() is the main iterative deepening loop. It calls root_search
552 // repeatedly with increasing depth until the allocated thinking time has
553 // been consumed, the user stops the search, or the maximum search depth is
556 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
558 SearchStack ss[PLY_MAX_PLUS_2];
560 Move EasyMove = MOVE_NONE;
561 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
562 int researchCountFL, researchCountFH;
564 // Moves to search are verified, scored and sorted
565 RootMoveList rml(pos, searchMoves);
568 // Handle special case of searching on a mate/stale position
571 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
573 cout << "info depth " << 1
574 << " score " << value_to_uci(s) << endl;
582 init_ss_array(ss, PLY_MAX_PLUS_2);
583 ValueByIteration[1] = rml[0].pv_score;
586 // Send initial RootMoveList scoring (iteration 1)
587 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
588 << "info depth " << Iteration
589 << "\n" << rml[0].pv_info_to_uci(pos, alpha, beta) << endl;
591 // Is one move significantly better than others after initial scoring ?
593 || rml[0].pv_score > rml[1].pv_score + EasyMoveMargin)
594 EasyMove = rml[0].pv[0];
596 // Iterative deepening loop
597 while (Iteration < PLY_MAX)
599 // Initialize iteration
601 BestMoveChangesByIteration[Iteration] = 0;
603 cout << "info depth " << Iteration << endl;
605 // Calculate dynamic aspiration window based on previous iterations
606 if (MultiPV == 1 && Iteration >= 6 && abs(ValueByIteration[Iteration - 1]) < VALUE_KNOWN_WIN)
608 int prevDelta1 = ValueByIteration[Iteration - 1] - ValueByIteration[Iteration - 2];
609 int prevDelta2 = ValueByIteration[Iteration - 2] - ValueByIteration[Iteration - 3];
611 AspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
612 AspirationDelta = (AspirationDelta + 7) / 8 * 8; // Round to match grainSize
614 alpha = Max(ValueByIteration[Iteration - 1] - AspirationDelta, -VALUE_INFINITE);
615 beta = Min(ValueByIteration[Iteration - 1] + AspirationDelta, VALUE_INFINITE);
618 depth = (Iteration - 2) * ONE_PLY + InitialDepth;
620 researchCountFL = researchCountFH = 0;
622 // We start with small aspiration window and in case of fail high/low, we
623 // research with bigger window until we are not failing high/low anymore.
626 // Sort the moves before to (re)search
627 rml.set_non_pv_scores(pos, rml[0].pv[0], ss);
630 // Search to the current depth, rml is updated and sorted
631 value = root_search(pos, ss, alpha, beta, depth, rml);
632 //value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
634 // Sort the moves before to return
637 // Write PV lines to transposition table, in case the relevant entries
638 // have been overwritten during the search.
639 for (int i = 0; i < Min(MultiPV, (int)rml.size()); i++)
640 rml[i].insert_pv_in_tt(pos);
645 assert(value >= alpha);
649 // Prepare for a research after a fail high, each time with a wider window
650 beta = Min(beta + AspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
653 else if (value <= alpha)
655 AspirationFailLow = true;
656 StopOnPonderhit = false;
658 // Prepare for a research after a fail low, each time with a wider window
659 alpha = Max(alpha - AspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
667 break; // Value cannot be trusted. Break out immediately!
669 //Save info about search result
670 ValueByIteration[Iteration] = value;
672 // Drop the easy move if differs from the new best move
673 if (rml[0].pv[0] != EasyMove)
674 EasyMove = MOVE_NONE;
676 if (UseTimeManagement)
679 bool stopSearch = false;
681 // Stop search early if there is only a single legal move,
682 // we search up to Iteration 6 anyway to get a proper score.
683 if (Iteration >= 6 && rml.size() == 1)
686 // Stop search early when the last two iterations returned a mate score
688 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
689 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
692 // Stop search early if one move seems to be much better than the others
694 && EasyMove == rml[0].pv[0]
695 && ( ( rml[0].nodes > (pos.nodes_searched() * 85) / 100
696 && current_search_time() > TimeMgr.available_time() / 16)
697 ||( rml[0].nodes > (pos.nodes_searched() * 98) / 100
698 && current_search_time() > TimeMgr.available_time() / 32)))
701 // Add some extra time if the best move has changed during the last two iterations
702 if (Iteration > 5 && Iteration <= 50)
703 TimeMgr.pv_instability(BestMoveChangesByIteration[Iteration],
704 BestMoveChangesByIteration[Iteration-1]);
706 // Stop search if most of MaxSearchTime is consumed at the end of the
707 // iteration. We probably don't have enough time to search the first
708 // move at the next iteration anyway.
709 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
715 StopOnPonderhit = true;
721 if (MaxDepth && Iteration >= MaxDepth)
725 *ponderMove = rml[0].pv[1];
730 // root_search() is the function which searches the root node. It is
731 // similar to search_pv except that it prints some information to the
732 // standard output and handles the fail low/high loops.
734 Value root_search(Position& pos, SearchStack* ss, Value alpha,
735 Value beta, Depth depth, RootMoveList& rml) {
737 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
738 assert(beta > alpha && beta <= VALUE_INFINITE);
739 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
741 Move movesSearched[MOVES_MAX];
747 Value bestValue, value, oldAlpha;
748 bool isCheck, moveIsCheck, captureOrPromotion, dangerous, isPvMove;
751 bestValue = value = -VALUE_INFINITE;
753 isCheck = pos.is_check();
755 // Step 1. Initialize node (polling is omitted at root)
756 ss->currentMove = ss->bestMove = MOVE_NONE;
757 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
759 // Step 2. Check for aborted search (omitted at root)
760 // Step 3. Mate distance pruning (omitted at root)
761 // Step 4. Transposition table lookup (omitted at root)
762 posKey = pos.get_key();
764 // Step 5. Evaluate the position statically
765 // At root we do this only to get reference value for child nodes
766 ss->evalMargin = VALUE_NONE;
767 ss->eval = isCheck ? VALUE_NONE : evaluate(pos, ss->evalMargin);
769 // Step 6. Razoring (omitted at root)
770 // Step 7. Static null move pruning (omitted at root)
771 // Step 8. Null move search with verification search (omitted at root)
772 // Step 9. Internal iterative deepening (omitted at root)
776 RootMoveList::iterator rm = rml.begin();
779 // Step 10. Loop through moves
780 // Loop through all legal moves until no moves remain or a beta cutoff occurs
781 while ( bestValue < beta
785 move = ss->currentMove = rm->pv[0];
786 movesSearched[moveCount++] = move;
787 isPvMove = (moveCount <= MultiPV);
789 // This is used by time management
790 FirstRootMove = (rm == rml.begin());
792 // Save the current node count before the move is searched
793 nodes = pos.nodes_searched();
795 // If it's time to send nodes info, do it here where we have the
796 // correct accumulated node counts searched by each thread.
797 if (SendSearchedNodes)
799 SendSearchedNodes = false;
800 cout << "info nodes " << nodes
801 << " nps " << nps(pos)
802 << " time " << current_search_time() << endl;
805 if (current_search_time() >= 1000)
806 cout << "info currmove " << move
807 << " currmovenumber " << moveCount << endl;
809 moveIsCheck = pos.move_is_check(move);
810 captureOrPromotion = pos.move_is_capture_or_promotion(move);
812 // Step 11. Decide the new search depth
813 ext = extension<PV>(pos, move, captureOrPromotion, moveIsCheck, false, false, &dangerous);
814 newDepth = depth + ext;
816 // Step 12. Futility pruning (omitted at root)
817 // Step 13. Make the move
818 pos.do_move(move, st, ci, moveIsCheck);
820 // Step extra. pv search
821 // We do pv search for PV moves
824 // Aspiration window is disabled in multi-pv case
826 alpha = -VALUE_INFINITE;
828 // Full depth PV search, done on first move or after a fail high
829 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
833 // Step 14. Reduced search
834 // if the move fails high will be re-searched at full depth
835 bool doFullDepthSearch = true;
837 if ( depth >= 3 * ONE_PLY
838 && !captureOrPromotion
840 && !move_is_castle(move)
841 && ss->killers[0] != move
842 && ss->killers[1] != move)
844 ss->reduction = reduction<PV>(depth, moveCount - MultiPV + 1);
848 Depth d = newDepth - ss->reduction;
849 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, 1);
851 doFullDepthSearch = (value > alpha);
853 ss->reduction = DEPTH_ZERO; // Restore original reduction
856 // Step 15. Full depth search
857 if (doFullDepthSearch)
859 // Full depth non-pv search using alpha as upperbound
860 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, 1);
862 // If we are above alpha then research at same depth but as PV
863 // to get a correct score or eventually a fail high above beta.
865 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, 1);
869 // Step 16. Undo move
872 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
874 // Finished searching the move. If StopRequest is true, the search
875 // was aborted because the user interrupted the search or because we
876 // ran out of time. In this case, the return value of the search cannot
877 // be trusted, and we break out of the loop without updating the best
882 // Remember searched nodes counts for this move
883 rm->nodes += pos.nodes_searched() - nodes;
885 // Step 17. Check for new best move
886 if (!isPvMove && value <= alpha)
887 rm->pv_score = -VALUE_INFINITE;
890 // PV move or new best move!
894 rm->pv_score = value;
895 rm->extract_pv_from_tt(pos);
897 // We record how often the best move has been changed in each
898 // iteration. This information is used for time managment: When
899 // the best move changes frequently, we allocate some more time.
900 if (!isPvMove && MultiPV == 1)
901 BestMoveChangesByIteration[Iteration]++;
903 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
904 // requires we send all the PV lines properly sorted.
905 rml.sort_multipv(moveCount);
907 for (int j = 0; j < Min(MultiPV, (int)rml.size()); j++)
908 cout << rml[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
910 // Update alpha. In multi-pv we don't use aspiration window
913 // Raise alpha to setup proper non-pv search upper bound
915 alpha = bestValue = value;
917 else // Set alpha equal to minimum score among the PV lines
918 alpha = bestValue = rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
920 } // PV move or new best move
926 // Step 20. Update tables
927 // If the search is not aborted, update the transposition table,
928 // history counters, and killer moves.
931 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
932 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
933 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
935 TT.store(posKey, value_to_tt(bestValue, 0), vt, depth, move, ss->eval, ss->evalMargin);
937 // Update killers and history only for non capture moves that fails high
938 if ( bestValue >= beta
939 && !pos.move_is_capture_or_promotion(move))
941 update_history(pos, move, depth, movesSearched, moveCount);
942 update_killers(move, ss->killers);
946 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
952 // search<>() is the main search function for both PV and non-PV nodes and for
953 // normal and SplitPoint nodes. When called just after a split point the search
954 // is simpler because we have already probed the hash table, done a null move
955 // search, and searched the first move before splitting, we don't have to repeat
956 // all this work again. We also don't need to store anything to the hash table
957 // here: This is taken care of after we return from the split point.
959 template <NodeType PvNode, bool SpNode, bool Root>
960 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
962 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
963 assert(beta > alpha && beta <= VALUE_INFINITE);
964 assert(PvNode || alpha == beta - 1);
965 assert((Root || ply > 0) && ply < PLY_MAX);
966 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
968 Move movesSearched[MOVES_MAX];
970 RootMoveList::iterator rm;
974 Move ttMove, move, excludedMove, threatMove;
977 Value bestValue, value, oldAlpha;
978 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
979 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
980 bool mateThreat = false;
982 int threadID = pos.thread();
983 SplitPoint* sp = NULL;
985 refinedValue = bestValue = value = -VALUE_INFINITE;
987 isCheck = pos.is_check();
993 ttMove = excludedMove = MOVE_NONE;
994 threatMove = sp->threatMove;
995 mateThreat = sp->mateThreat;
996 goto split_point_start;
998 else {} // Hack to fix icc's "statement is unreachable" warning
1000 // Step 1. Initialize node and poll. Polling can abort search
1001 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
1002 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
1006 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
1012 // Step 2. Check for aborted search and immediate draw
1014 || ThreadsMgr.cutoff_at_splitpoint(threadID)
1016 || ply >= PLY_MAX - 1)
1019 // Step 3. Mate distance pruning
1020 alpha = Max(value_mated_in(ply), alpha);
1021 beta = Min(value_mate_in(ply+1), beta);
1026 // Step 4. Transposition table lookup
1028 // We don't want the score of a partial search to overwrite a previous full search
1029 // TT value, so we use a different position key in case of an excluded move exists.
1030 excludedMove = ss->excludedMove;
1031 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
1033 tte = TT.retrieve(posKey);
1034 ttMove = tte ? tte->move() : MOVE_NONE;
1036 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
1037 // This is to avoid problems in the following areas:
1039 // * Repetition draw detection
1040 // * Fifty move rule detection
1041 // * Searching for a mate
1042 // * Printing of full PV line
1043 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1046 ss->bestMove = ttMove; // Can be MOVE_NONE
1047 return value_from_tt(tte->value(), ply);
1050 // Step 5. Evaluate the position statically and
1051 // update gain statistics of parent move.
1053 ss->eval = ss->evalMargin = VALUE_NONE;
1056 assert(tte->static_value() != VALUE_NONE);
1058 ss->eval = tte->static_value();
1059 ss->evalMargin = tte->static_value_margin();
1060 refinedValue = refine_eval(tte, ss->eval, ply);
1064 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
1065 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
1068 // Save gain for the parent non-capture move
1070 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1072 // Step 6. Razoring (is omitted in PV nodes)
1074 && depth < RazorDepth
1076 && refinedValue < beta - razor_margin(depth)
1077 && ttMove == MOVE_NONE
1078 && !value_is_mate(beta)
1079 && !pos.has_pawn_on_7th(pos.side_to_move()))
1081 Value rbeta = beta - razor_margin(depth);
1082 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
1084 // Logically we should return (v + razor_margin(depth)), but
1085 // surprisingly this did slightly weaker in tests.
1089 // Step 7. Static null move pruning (is omitted in PV nodes)
1090 // We're betting that the opponent doesn't have a move that will reduce
1091 // the score by more than futility_margin(depth) if we do a null move.
1093 && !ss->skipNullMove
1094 && depth < RazorDepth
1096 && refinedValue >= beta + futility_margin(depth, 0)
1097 && !value_is_mate(beta)
1098 && pos.non_pawn_material(pos.side_to_move()))
1099 return refinedValue - futility_margin(depth, 0);
1101 // Step 8. Null move search with verification search (is omitted in PV nodes)
1103 && !ss->skipNullMove
1106 && refinedValue >= beta
1107 && !value_is_mate(beta)
1108 && pos.non_pawn_material(pos.side_to_move()))
1110 ss->currentMove = MOVE_NULL;
1112 // Null move dynamic reduction based on depth
1113 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
1115 // Null move dynamic reduction based on value
1116 if (refinedValue - beta > PawnValueMidgame)
1119 pos.do_null_move(st);
1120 (ss+1)->skipNullMove = true;
1121 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
1122 (ss+1)->skipNullMove = false;
1123 pos.undo_null_move();
1125 if (nullValue >= beta)
1127 // Do not return unproven mate scores
1128 if (nullValue >= value_mate_in(PLY_MAX))
1131 if (depth < 6 * ONE_PLY)
1134 // Do verification search at high depths
1135 ss->skipNullMove = true;
1136 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
1137 ss->skipNullMove = false;
1144 // The null move failed low, which means that we may be faced with
1145 // some kind of threat. If the previous move was reduced, check if
1146 // the move that refuted the null move was somehow connected to the
1147 // move which was reduced. If a connection is found, return a fail
1148 // low score (which will cause the reduced move to fail high in the
1149 // parent node, which will trigger a re-search with full depth).
1150 if (nullValue == value_mated_in(ply + 2))
1153 threatMove = (ss+1)->bestMove;
1154 if ( depth < ThreatDepth
1155 && (ss-1)->reduction
1156 && threatMove != MOVE_NONE
1157 && connected_moves(pos, (ss-1)->currentMove, threatMove))
1162 // Step 9. Internal iterative deepening
1164 && depth >= IIDDepth[PvNode]
1165 && ttMove == MOVE_NONE
1166 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
1168 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
1170 ss->skipNullMove = true;
1171 search<PvNode>(pos, ss, alpha, beta, d, ply);
1172 ss->skipNullMove = false;
1174 ttMove = ss->bestMove;
1175 tte = TT.retrieve(posKey);
1178 // Expensive mate threat detection (only for PV nodes)
1179 if (PvNode && !Root) // FIXME
1180 mateThreat = pos.has_mate_threat();
1182 split_point_start: // At split points actual search starts from here
1184 // Initialize a MovePicker object for the current position
1185 // FIXME currently MovePicker() c'tor is needless called also in SplitPoint
1186 MovePicker mpBase(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1187 MovePicker& mp = SpNode ? *sp->mp : mpBase;
1189 ss->bestMove = MOVE_NONE;
1190 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1191 futilityBase = ss->eval + ss->evalMargin;
1192 singularExtensionNode = !Root
1194 && depth >= SingularExtensionDepth[PvNode]
1197 && !excludedMove // Do not allow recursive singular extension search
1198 && (tte->type() & VALUE_TYPE_LOWER)
1199 && tte->depth() >= depth - 3 * ONE_PLY;
1208 lock_grab(&(sp->lock));
1209 bestValue = sp->bestValue;
1212 // Step 10. Loop through moves
1213 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1214 while ( bestValue < beta
1215 && (!Root || rm != Rml->end())
1216 && ( Root || (move = mp.get_next_move()) != MOVE_NONE)
1217 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1223 // This is used by time management
1224 FirstRootMove = (rm == Rml->begin());
1226 // Save the current node count before the move is searched
1227 nodes = pos.nodes_searched();
1229 // If it's time to send nodes info, do it here where we have the
1230 // correct accumulated node counts searched by each thread.
1231 if (SendSearchedNodes)
1233 SendSearchedNodes = false;
1234 cout << "info nodes " << nodes
1235 << " nps " << nps(pos)
1236 << " time " << current_search_time() << endl;
1239 if (current_search_time() >= 1000)
1240 cout << "info currmove " << move
1241 << " currmovenumber " << moveCount << endl;
1244 assert(move_is_ok(move));
1248 moveCount = ++sp->moveCount;
1249 lock_release(&(sp->lock));
1251 else if (move == excludedMove)
1254 movesSearched[moveCount++] = move;
1256 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1257 moveIsCheck = pos.move_is_check(move, ci);
1258 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1260 // Step 11. Decide the new search depth
1261 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1263 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1264 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1265 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1266 // lower then ttValue minus a margin then we extend ttMove.
1267 if ( singularExtensionNode
1268 && move == tte->move()
1271 Value ttValue = value_from_tt(tte->value(), ply);
1273 if (abs(ttValue) < VALUE_KNOWN_WIN)
1275 Value b = ttValue - SingularExtensionMargin;
1276 ss->excludedMove = move;
1277 ss->skipNullMove = true;
1278 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1279 ss->skipNullMove = false;
1280 ss->excludedMove = MOVE_NONE;
1281 ss->bestMove = MOVE_NONE;
1287 // Update current move (this must be done after singular extension search)
1288 ss->currentMove = move;
1289 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1291 // Step 12. Futility pruning (is omitted in PV nodes)
1293 && !captureOrPromotion
1297 && !move_is_castle(move))
1299 // Move count based pruning
1300 if ( moveCount >= futility_move_count(depth)
1301 && !(threatMove && connected_threat(pos, move, threatMove))
1302 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1305 lock_grab(&(sp->lock));
1310 // Value based pruning
1311 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1312 // but fixing this made program slightly weaker.
1313 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1314 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1315 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1317 if (futilityValueScaled < beta)
1321 lock_grab(&(sp->lock));
1322 if (futilityValueScaled > sp->bestValue)
1323 sp->bestValue = bestValue = futilityValueScaled;
1325 else if (futilityValueScaled > bestValue)
1326 bestValue = futilityValueScaled;
1331 // Prune moves with negative SEE at low depths
1332 if ( predictedDepth < 2 * ONE_PLY
1333 && bestValue > value_mated_in(PLY_MAX)
1334 && pos.see_sign(move) < 0)
1337 lock_grab(&(sp->lock));
1343 // Step 13. Make the move
1344 pos.do_move(move, st, ci, moveIsCheck);
1346 // Step extra. pv search (only in PV nodes)
1347 // The first move in list is the expected PV
1350 // Aspiration window is disabled in multi-pv case
1351 if (Root && MultiPV > 1)
1352 alpha = -VALUE_INFINITE;
1354 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1358 // Step 14. Reduced depth search
1359 // If the move fails high will be re-searched at full depth.
1360 bool doFullDepthSearch = true;
1362 if ( depth >= 3 * ONE_PLY
1363 && !captureOrPromotion
1365 && !move_is_castle(move)
1366 && ss->killers[0] != move
1367 && ss->killers[1] != move)
1369 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1370 : reduction<PvNode>(depth, moveCount);
1373 alpha = SpNode ? sp->alpha : alpha;
1374 Depth d = newDepth - ss->reduction;
1375 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1377 doFullDepthSearch = (value > alpha);
1379 ss->reduction = DEPTH_ZERO; // Restore original reduction
1382 // Step 15. Full depth search
1383 if (doFullDepthSearch)
1385 alpha = SpNode ? sp->alpha : alpha;
1386 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1388 // Step extra. pv search (only in PV nodes)
1389 // Search only for possible new PV nodes, if instead value >= beta then
1390 // parent node fails low with value <= alpha and tries another move.
1391 if (PvNode && value > alpha && (Root || value < beta))
1392 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1396 // Step 16. Undo move
1397 pos.undo_move(move);
1399 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1401 // Step 17. Check for new best move
1404 lock_grab(&(sp->lock));
1405 bestValue = sp->bestValue;
1409 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1414 sp->bestValue = value;
1418 if (PvNode && value < beta) // We want always alpha < beta
1426 sp->betaCutoff = true;
1428 if (value == value_mate_in(ply + 1))
1429 ss->mateKiller = move;
1431 ss->bestMove = move;
1434 sp->parentSstack->bestMove = move;
1440 // Finished searching the move. If StopRequest is true, the search
1441 // was aborted because the user interrupted the search or because we
1442 // ran out of time. In this case, the return value of the search cannot
1443 // be trusted, and we break out of the loop without updating the best
1448 // Remember searched nodes counts for this move
1449 rm->nodes += pos.nodes_searched() - nodes;
1451 // Step 17. Check for new best move
1452 if (!isPvMove && value <= alpha)
1453 rm->pv_score = -VALUE_INFINITE;
1456 // PV move or new best move!
1459 ss->bestMove = move;
1460 rm->pv_score = value;
1461 rm->extract_pv_from_tt(pos);
1463 // We record how often the best move has been changed in each
1464 // iteration. This information is used for time managment: When
1465 // the best move changes frequently, we allocate some more time.
1466 if (!isPvMove && MultiPV == 1)
1467 BestMoveChangesByIteration[Iteration]++;
1469 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1470 // requires we send all the PV lines properly sorted.
1471 Rml->sort_multipv(moveCount);
1473 for (int j = 0; j < Min(MultiPV, (int)Rml->size()); j++)
1474 cout << (*Rml)[j].pv_info_to_uci(pos, alpha, beta, j) << endl;
1476 // Update alpha. In multi-pv we don't use aspiration window
1479 // Raise alpha to setup proper non-pv search upper bound
1481 alpha = bestValue = value;
1483 else // Set alpha equal to minimum score among the PV lines
1484 alpha = bestValue = (*Rml)[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1486 } // PV move or new best move
1491 // Step 18. Check for split
1494 && depth >= ThreadsMgr.min_split_depth()
1495 && ThreadsMgr.active_threads() > 1
1497 && ThreadsMgr.available_thread_exists(threadID)
1499 && !ThreadsMgr.cutoff_at_splitpoint(threadID)
1501 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1502 threatMove, mateThreat, moveCount, &mp, PvNode);
1505 // Step 19. Check for mate and stalemate
1506 // All legal moves have been searched and if there are
1507 // no legal moves, it must be mate or stalemate.
1508 // If one move was excluded return fail low score.
1509 if (!SpNode && !moveCount)
1510 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1512 // Step 20. Update tables
1513 // If the search is not aborted, update the transposition table,
1514 // history counters, and killer moves.
1515 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1517 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1518 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1519 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1521 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1523 // Update killers and history only for non capture moves that fails high
1524 if ( bestValue >= beta
1525 && !pos.move_is_capture_or_promotion(move))
1527 update_history(pos, move, depth, movesSearched, moveCount);
1528 update_killers(move, ss->killers);
1534 // Here we have the lock still grabbed
1535 sp->slaves[threadID] = 0;
1536 sp->nodes += pos.nodes_searched();
1537 lock_release(&(sp->lock));
1540 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1545 // qsearch() is the quiescence search function, which is called by the main
1546 // search function when the remaining depth is zero (or, to be more precise,
1547 // less than ONE_PLY).
1549 template <NodeType PvNode>
1550 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1552 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1553 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1554 assert(PvNode || alpha == beta - 1);
1556 assert(ply > 0 && ply < PLY_MAX);
1557 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1561 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1562 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1565 Value oldAlpha = alpha;
1567 ss->bestMove = ss->currentMove = MOVE_NONE;
1569 // Check for an instant draw or maximum ply reached
1570 if (pos.is_draw() || ply >= PLY_MAX - 1)
1573 // Decide whether or not to include checks, this fixes also the type of
1574 // TT entry depth that we are going to use. Note that in qsearch we use
1575 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1576 isCheck = pos.is_check();
1577 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1579 // Transposition table lookup. At PV nodes, we don't use the TT for
1580 // pruning, but only for move ordering.
1581 tte = TT.retrieve(pos.get_key());
1582 ttMove = (tte ? tte->move() : MOVE_NONE);
1584 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1586 ss->bestMove = ttMove; // Can be MOVE_NONE
1587 return value_from_tt(tte->value(), ply);
1590 // Evaluate the position statically
1593 bestValue = futilityBase = -VALUE_INFINITE;
1594 ss->eval = evalMargin = VALUE_NONE;
1595 enoughMaterial = false;
1601 assert(tte->static_value() != VALUE_NONE);
1603 evalMargin = tte->static_value_margin();
1604 ss->eval = bestValue = tte->static_value();
1607 ss->eval = bestValue = evaluate(pos, evalMargin);
1609 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1611 // Stand pat. Return immediately if static value is at least beta
1612 if (bestValue >= beta)
1615 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1620 if (PvNode && bestValue > alpha)
1623 // Futility pruning parameters, not needed when in check
1624 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1625 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1628 // Initialize a MovePicker object for the current position, and prepare
1629 // to search the moves. Because the depth is <= 0 here, only captures,
1630 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1632 MovePicker mp(pos, ttMove, depth, H);
1635 // Loop through the moves until no moves remain or a beta cutoff occurs
1636 while ( alpha < beta
1637 && (move = mp.get_next_move()) != MOVE_NONE)
1639 assert(move_is_ok(move));
1641 moveIsCheck = pos.move_is_check(move, ci);
1649 && !move_is_promotion(move)
1650 && !pos.move_is_passed_pawn_push(move))
1652 futilityValue = futilityBase
1653 + pos.endgame_value_of_piece_on(move_to(move))
1654 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1656 if (futilityValue < alpha)
1658 if (futilityValue > bestValue)
1659 bestValue = futilityValue;
1664 // Detect non-capture evasions that are candidate to be pruned
1665 evasionPrunable = isCheck
1666 && bestValue > value_mated_in(PLY_MAX)
1667 && !pos.move_is_capture(move)
1668 && !pos.can_castle(pos.side_to_move());
1670 // Don't search moves with negative SEE values
1672 && (!isCheck || evasionPrunable)
1674 && !move_is_promotion(move)
1675 && pos.see_sign(move) < 0)
1678 // Don't search useless checks
1683 && !pos.move_is_capture_or_promotion(move)
1684 && ss->eval + PawnValueMidgame / 4 < beta
1685 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1687 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1688 bestValue = ss->eval + PawnValueMidgame / 4;
1693 // Update current move
1694 ss->currentMove = move;
1696 // Make and search the move
1697 pos.do_move(move, st, ci, moveIsCheck);
1698 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1699 pos.undo_move(move);
1701 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1704 if (value > bestValue)
1710 ss->bestMove = move;
1715 // All legal moves have been searched. A special case: If we're in check
1716 // and no legal moves were found, it is checkmate.
1717 if (isCheck && bestValue == -VALUE_INFINITE)
1718 return value_mated_in(ply);
1720 // Update transposition table
1721 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1722 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1724 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1730 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1731 // bestValue is updated only when returning false because in that case move
1734 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1736 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1737 Square from, to, ksq, victimSq;
1740 Value futilityValue, bv = *bestValue;
1742 from = move_from(move);
1744 them = opposite_color(pos.side_to_move());
1745 ksq = pos.king_square(them);
1746 kingAtt = pos.attacks_from<KING>(ksq);
1747 pc = pos.piece_on(from);
1749 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1750 oldAtt = pos.attacks_from(pc, from, occ);
1751 newAtt = pos.attacks_from(pc, to, occ);
1753 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1754 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1756 if (!(b && (b & (b - 1))))
1759 // Rule 2. Queen contact check is very dangerous
1760 if ( type_of_piece(pc) == QUEEN
1761 && bit_is_set(kingAtt, to))
1764 // Rule 3. Creating new double threats with checks
1765 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1769 victimSq = pop_1st_bit(&b);
1770 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1772 // Note that here we generate illegal "double move"!
1773 if ( futilityValue >= beta
1774 && pos.see_sign(make_move(from, victimSq)) >= 0)
1777 if (futilityValue > bv)
1781 // Update bestValue only if check is not dangerous (because we will prune the move)
1787 // connected_moves() tests whether two moves are 'connected' in the sense
1788 // that the first move somehow made the second move possible (for instance
1789 // if the moving piece is the same in both moves). The first move is assumed
1790 // to be the move that was made to reach the current position, while the
1791 // second move is assumed to be a move from the current position.
1793 bool connected_moves(const Position& pos, Move m1, Move m2) {
1795 Square f1, t1, f2, t2;
1798 assert(m1 && move_is_ok(m1));
1799 assert(m2 && move_is_ok(m2));
1801 // Case 1: The moving piece is the same in both moves
1807 // Case 2: The destination square for m2 was vacated by m1
1813 // Case 3: Moving through the vacated square
1814 if ( piece_is_slider(pos.piece_on(f2))
1815 && bit_is_set(squares_between(f2, t2), f1))
1818 // Case 4: The destination square for m2 is defended by the moving piece in m1
1819 p = pos.piece_on(t1);
1820 if (bit_is_set(pos.attacks_from(p, t1), t2))
1823 // Case 5: Discovered check, checking piece is the piece moved in m1
1824 if ( piece_is_slider(p)
1825 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1826 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1828 // discovered_check_candidates() works also if the Position's side to
1829 // move is the opposite of the checking piece.
1830 Color them = opposite_color(pos.side_to_move());
1831 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1833 if (bit_is_set(dcCandidates, f2))
1840 // value_is_mate() checks if the given value is a mate one eventually
1841 // compensated for the ply.
1843 bool value_is_mate(Value value) {
1845 assert(abs(value) <= VALUE_INFINITE);
1847 return value <= value_mated_in(PLY_MAX)
1848 || value >= value_mate_in(PLY_MAX);
1852 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1853 // "plies to mate from the current ply". Non-mate scores are unchanged.
1854 // The function is called before storing a value to the transposition table.
1856 Value value_to_tt(Value v, int ply) {
1858 if (v >= value_mate_in(PLY_MAX))
1861 if (v <= value_mated_in(PLY_MAX))
1868 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1869 // the transposition table to a mate score corrected for the current ply.
1871 Value value_from_tt(Value v, int ply) {
1873 if (v >= value_mate_in(PLY_MAX))
1876 if (v <= value_mated_in(PLY_MAX))
1883 // extension() decides whether a move should be searched with normal depth,
1884 // or with extended depth. Certain classes of moves (checking moves, in
1885 // particular) are searched with bigger depth than ordinary moves and in
1886 // any case are marked as 'dangerous'. Note that also if a move is not
1887 // extended, as example because the corresponding UCI option is set to zero,
1888 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1889 template <NodeType PvNode>
1890 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1891 bool singleEvasion, bool mateThreat, bool* dangerous) {
1893 assert(m != MOVE_NONE);
1895 Depth result = DEPTH_ZERO;
1896 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1900 if (moveIsCheck && pos.see_sign(m) >= 0)
1901 result += CheckExtension[PvNode];
1904 result += SingleEvasionExtension[PvNode];
1907 result += MateThreatExtension[PvNode];
1910 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1912 Color c = pos.side_to_move();
1913 if (relative_rank(c, move_to(m)) == RANK_7)
1915 result += PawnPushTo7thExtension[PvNode];
1918 if (pos.pawn_is_passed(c, move_to(m)))
1920 result += PassedPawnExtension[PvNode];
1925 if ( captureOrPromotion
1926 && pos.type_of_piece_on(move_to(m)) != PAWN
1927 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1928 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1929 && !move_is_promotion(m)
1932 result += PawnEndgameExtension[PvNode];
1937 && captureOrPromotion
1938 && pos.type_of_piece_on(move_to(m)) != PAWN
1939 && pos.see_sign(m) >= 0)
1941 result += ONE_PLY / 2;
1945 return Min(result, ONE_PLY);
1949 // connected_threat() tests whether it is safe to forward prune a move or if
1950 // is somehow coonected to the threat move returned by null search.
1952 bool connected_threat(const Position& pos, Move m, Move threat) {
1954 assert(move_is_ok(m));
1955 assert(threat && move_is_ok(threat));
1956 assert(!pos.move_is_check(m));
1957 assert(!pos.move_is_capture_or_promotion(m));
1958 assert(!pos.move_is_passed_pawn_push(m));
1960 Square mfrom, mto, tfrom, tto;
1962 mfrom = move_from(m);
1964 tfrom = move_from(threat);
1965 tto = move_to(threat);
1967 // Case 1: Don't prune moves which move the threatened piece
1971 // Case 2: If the threatened piece has value less than or equal to the
1972 // value of the threatening piece, don't prune move which defend it.
1973 if ( pos.move_is_capture(threat)
1974 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1975 || pos.type_of_piece_on(tfrom) == KING)
1976 && pos.move_attacks_square(m, tto))
1979 // Case 3: If the moving piece in the threatened move is a slider, don't
1980 // prune safe moves which block its ray.
1981 if ( piece_is_slider(pos.piece_on(tfrom))
1982 && bit_is_set(squares_between(tfrom, tto), mto)
1983 && pos.see_sign(m) >= 0)
1990 // ok_to_use_TT() returns true if a transposition table score
1991 // can be used at a given point in search.
1993 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1995 Value v = value_from_tt(tte->value(), ply);
1997 return ( tte->depth() >= depth
1998 || v >= Max(value_mate_in(PLY_MAX), beta)
1999 || v < Min(value_mated_in(PLY_MAX), beta))
2001 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
2002 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
2006 // refine_eval() returns the transposition table score if
2007 // possible otherwise falls back on static position evaluation.
2009 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
2013 Value v = value_from_tt(tte->value(), ply);
2015 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
2016 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
2023 // update_history() registers a good move that produced a beta-cutoff
2024 // in history and marks as failures all the other moves of that ply.
2026 void update_history(const Position& pos, Move move, Depth depth,
2027 Move movesSearched[], int moveCount) {
2029 Value bonus = Value(int(depth) * int(depth));
2031 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
2033 for (int i = 0; i < moveCount - 1; i++)
2035 m = movesSearched[i];
2039 if (!pos.move_is_capture_or_promotion(m))
2040 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
2045 // update_killers() add a good move that produced a beta-cutoff
2046 // among the killer moves of that ply.
2048 void update_killers(Move m, Move killers[]) {
2050 if (m == killers[0])
2053 killers[1] = killers[0];
2058 // update_gains() updates the gains table of a non-capture move given
2059 // the static position evaluation before and after the move.
2061 void update_gains(const Position& pos, Move m, Value before, Value after) {
2064 && before != VALUE_NONE
2065 && after != VALUE_NONE
2066 && pos.captured_piece_type() == PIECE_TYPE_NONE
2067 && !move_is_special(m))
2068 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
2072 // init_ss_array() does a fast reset of the first entries of a SearchStack
2073 // array and of all the excludedMove and skipNullMove entries.
2075 void init_ss_array(SearchStack* ss, int size) {
2077 for (int i = 0; i < size; i++, ss++)
2079 ss->excludedMove = MOVE_NONE;
2080 ss->skipNullMove = false;
2081 ss->reduction = DEPTH_ZERO;
2085 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
2090 // value_to_uci() converts a value to a string suitable for use with the UCI
2091 // protocol specifications:
2093 // cp <x> The score from the engine's point of view in centipawns.
2094 // mate <y> Mate in y moves, not plies. If the engine is getting mated
2095 // use negative values for y.
2097 std::string value_to_uci(Value v) {
2099 std::stringstream s;
2101 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
2102 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
2104 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
2110 // current_search_time() returns the number of milliseconds which have passed
2111 // since the beginning of the current search.
2113 int current_search_time() {
2115 return get_system_time() - SearchStartTime;
2119 // nps() computes the current nodes/second count
2121 int nps(const Position& pos) {
2123 int t = current_search_time();
2124 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
2128 // poll() performs two different functions: It polls for user input, and it
2129 // looks at the time consumed so far and decides if it's time to abort the
2132 void poll(const Position& pos) {
2134 static int lastInfoTime;
2135 int t = current_search_time();
2138 if (input_available())
2140 // We are line oriented, don't read single chars
2141 std::string command;
2143 if (!std::getline(std::cin, command))
2146 if (command == "quit")
2148 // Quit the program as soon as possible
2150 QuitRequest = StopRequest = true;
2153 else if (command == "stop")
2155 // Stop calculating as soon as possible, but still send the "bestmove"
2156 // and possibly the "ponder" token when finishing the search.
2160 else if (command == "ponderhit")
2162 // The opponent has played the expected move. GUI sends "ponderhit" if
2163 // we were told to ponder on the same move the opponent has played. We
2164 // should continue searching but switching from pondering to normal search.
2167 if (StopOnPonderhit)
2172 // Print search information
2176 else if (lastInfoTime > t)
2177 // HACK: Must be a new search where we searched less than
2178 // NodesBetweenPolls nodes during the first second of search.
2181 else if (t - lastInfoTime >= 1000)
2188 if (dbg_show_hit_rate)
2189 dbg_print_hit_rate();
2191 // Send info on searched nodes as soon as we return to root
2192 SendSearchedNodes = true;
2195 // Should we stop the search?
2199 bool stillAtFirstMove = FirstRootMove
2200 && !AspirationFailLow
2201 && t > TimeMgr.available_time();
2203 bool noMoreTime = t > TimeMgr.maximum_time()
2204 || stillAtFirstMove;
2206 if ( (UseTimeManagement && noMoreTime)
2207 || (ExactMaxTime && t >= ExactMaxTime)
2208 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2213 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2214 // while the program is pondering. The point is to work around a wrinkle in
2215 // the UCI protocol: When pondering, the engine is not allowed to give a
2216 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2217 // We simply wait here until one of these commands is sent, and return,
2218 // after which the bestmove and pondermove will be printed.
2220 void wait_for_stop_or_ponderhit() {
2222 std::string command;
2226 // Wait for a command from stdin
2227 if (!std::getline(std::cin, command))
2230 if (command == "quit")
2235 else if (command == "ponderhit" || command == "stop")
2241 // init_thread() is the function which is called when a new thread is
2242 // launched. It simply calls the idle_loop() function with the supplied
2243 // threadID. There are two versions of this function; one for POSIX
2244 // threads and one for Windows threads.
2246 #if !defined(_MSC_VER)
2248 void* init_thread(void* threadID) {
2250 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2256 DWORD WINAPI init_thread(LPVOID threadID) {
2258 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2265 /// The ThreadsManager class
2268 // read_uci_options() updates number of active threads and other internal
2269 // parameters according to the UCI options values. It is called before
2270 // to start a new search.
2272 void ThreadsManager::read_uci_options() {
2274 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2275 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2276 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2277 activeThreads = Options["Threads"].value<int>();
2281 // idle_loop() is where the threads are parked when they have no work to do.
2282 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2283 // object for which the current thread is the master.
2285 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2287 assert(threadID >= 0 && threadID < MAX_THREADS);
2290 bool allFinished = false;
2294 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2295 // master should exit as last one.
2296 if (allThreadsShouldExit)
2299 threads[threadID].state = THREAD_TERMINATED;
2303 // If we are not thinking, wait for a condition to be signaled
2304 // instead of wasting CPU time polling for work.
2305 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2306 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2308 assert(!sp || useSleepingThreads);
2309 assert(threadID != 0 || useSleepingThreads);
2311 if (threads[threadID].state == THREAD_INITIALIZING)
2312 threads[threadID].state = THREAD_AVAILABLE;
2314 // Grab the lock to avoid races with wake_sleeping_thread()
2315 lock_grab(&sleepLock[threadID]);
2317 // If we are master and all slaves have finished do not go to sleep
2318 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2319 allFinished = (i == activeThreads);
2321 if (allFinished || allThreadsShouldExit)
2323 lock_release(&sleepLock[threadID]);
2327 // Do sleep here after retesting sleep conditions
2328 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2329 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2331 lock_release(&sleepLock[threadID]);
2334 // If this thread has been assigned work, launch a search
2335 if (threads[threadID].state == THREAD_WORKISWAITING)
2337 assert(!allThreadsShouldExit);
2339 threads[threadID].state = THREAD_SEARCHING;
2341 // Here we call search() with SplitPoint template parameter set to true
2342 SplitPoint* tsp = threads[threadID].splitPoint;
2343 Position pos(*tsp->pos, threadID);
2344 SearchStack* ss = tsp->sstack[threadID] + 1;
2348 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2350 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2352 assert(threads[threadID].state == THREAD_SEARCHING);
2354 threads[threadID].state = THREAD_AVAILABLE;
2356 // Wake up master thread so to allow it to return from the idle loop in
2357 // case we are the last slave of the split point.
2358 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2359 wake_sleeping_thread(tsp->master);
2362 // If this thread is the master of a split point and all slaves have
2363 // finished their work at this split point, return from the idle loop.
2364 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2365 allFinished = (i == activeThreads);
2369 // Because sp->slaves[] is reset under lock protection,
2370 // be sure sp->lock has been released before to return.
2371 lock_grab(&(sp->lock));
2372 lock_release(&(sp->lock));
2374 // In helpful master concept a master can help only a sub-tree, and
2375 // because here is all finished is not possible master is booked.
2376 assert(threads[threadID].state == THREAD_AVAILABLE);
2378 threads[threadID].state = THREAD_SEARCHING;
2385 // init_threads() is called during startup. It launches all helper threads,
2386 // and initializes the split point stack and the global locks and condition
2389 void ThreadsManager::init_threads() {
2391 int i, arg[MAX_THREADS];
2394 // Initialize global locks
2397 for (i = 0; i < MAX_THREADS; i++)
2399 lock_init(&sleepLock[i]);
2400 cond_init(&sleepCond[i]);
2403 // Initialize splitPoints[] locks
2404 for (i = 0; i < MAX_THREADS; i++)
2405 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2406 lock_init(&(threads[i].splitPoints[j].lock));
2408 // Will be set just before program exits to properly end the threads
2409 allThreadsShouldExit = false;
2411 // Threads will be put all threads to sleep as soon as created
2414 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2415 threads[0].state = THREAD_SEARCHING;
2416 for (i = 1; i < MAX_THREADS; i++)
2417 threads[i].state = THREAD_INITIALIZING;
2419 // Launch the helper threads
2420 for (i = 1; i < MAX_THREADS; i++)
2424 #if !defined(_MSC_VER)
2425 pthread_t pthread[1];
2426 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2427 pthread_detach(pthread[0]);
2429 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2433 cout << "Failed to create thread number " << i << endl;
2437 // Wait until the thread has finished launching and is gone to sleep
2438 while (threads[i].state == THREAD_INITIALIZING) {}
2443 // exit_threads() is called when the program exits. It makes all the
2444 // helper threads exit cleanly.
2446 void ThreadsManager::exit_threads() {
2448 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2450 // Wake up all the threads and waits for termination
2451 for (int i = 1; i < MAX_THREADS; i++)
2453 wake_sleeping_thread(i);
2454 while (threads[i].state != THREAD_TERMINATED) {}
2457 // Now we can safely destroy the locks
2458 for (int i = 0; i < MAX_THREADS; i++)
2459 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2460 lock_destroy(&(threads[i].splitPoints[j].lock));
2462 lock_destroy(&mpLock);
2464 // Now we can safely destroy the wait conditions
2465 for (int i = 0; i < MAX_THREADS; i++)
2467 lock_destroy(&sleepLock[i]);
2468 cond_destroy(&sleepCond[i]);
2473 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2474 // the thread's currently active split point, or in some ancestor of
2475 // the current split point.
2477 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2479 assert(threadID >= 0 && threadID < activeThreads);
2481 SplitPoint* sp = threads[threadID].splitPoint;
2483 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2488 // thread_is_available() checks whether the thread with threadID "slave" is
2489 // available to help the thread with threadID "master" at a split point. An
2490 // obvious requirement is that "slave" must be idle. With more than two
2491 // threads, this is not by itself sufficient: If "slave" is the master of
2492 // some active split point, it is only available as a slave to the other
2493 // threads which are busy searching the split point at the top of "slave"'s
2494 // split point stack (the "helpful master concept" in YBWC terminology).
2496 bool ThreadsManager::thread_is_available(int slave, int master) const {
2498 assert(slave >= 0 && slave < activeThreads);
2499 assert(master >= 0 && master < activeThreads);
2500 assert(activeThreads > 1);
2502 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2505 // Make a local copy to be sure doesn't change under our feet
2506 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2508 // No active split points means that the thread is available as
2509 // a slave for any other thread.
2510 if (localActiveSplitPoints == 0 || activeThreads == 2)
2513 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2514 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2515 // could have been set to 0 by another thread leading to an out of bound access.
2516 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2523 // available_thread_exists() tries to find an idle thread which is available as
2524 // a slave for the thread with threadID "master".
2526 bool ThreadsManager::available_thread_exists(int master) const {
2528 assert(master >= 0 && master < activeThreads);
2529 assert(activeThreads > 1);
2531 for (int i = 0; i < activeThreads; i++)
2532 if (thread_is_available(i, master))
2539 // split() does the actual work of distributing the work at a node between
2540 // several available threads. If it does not succeed in splitting the
2541 // node (because no idle threads are available, or because we have no unused
2542 // split point objects), the function immediately returns. If splitting is
2543 // possible, a SplitPoint object is initialized with all the data that must be
2544 // copied to the helper threads and we tell our helper threads that they have
2545 // been assigned work. This will cause them to instantly leave their idle loops and
2546 // call search().When all threads have returned from search() then split() returns.
2548 template <bool Fake>
2549 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2550 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2551 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2552 assert(pos.is_ok());
2553 assert(ply > 0 && ply < PLY_MAX);
2554 assert(*bestValue >= -VALUE_INFINITE);
2555 assert(*bestValue <= *alpha);
2556 assert(*alpha < beta);
2557 assert(beta <= VALUE_INFINITE);
2558 assert(depth > DEPTH_ZERO);
2559 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2560 assert(activeThreads > 1);
2562 int i, master = pos.thread();
2563 Thread& masterThread = threads[master];
2567 // If no other thread is available to help us, or if we have too many
2568 // active split points, don't split.
2569 if ( !available_thread_exists(master)
2570 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2572 lock_release(&mpLock);
2576 // Pick the next available split point object from the split point stack
2577 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2579 // Initialize the split point object
2580 splitPoint.parent = masterThread.splitPoint;
2581 splitPoint.master = master;
2582 splitPoint.betaCutoff = false;
2583 splitPoint.ply = ply;
2584 splitPoint.depth = depth;
2585 splitPoint.threatMove = threatMove;
2586 splitPoint.mateThreat = mateThreat;
2587 splitPoint.alpha = *alpha;
2588 splitPoint.beta = beta;
2589 splitPoint.pvNode = pvNode;
2590 splitPoint.bestValue = *bestValue;
2592 splitPoint.moveCount = moveCount;
2593 splitPoint.pos = &pos;
2594 splitPoint.nodes = 0;
2595 splitPoint.parentSstack = ss;
2596 for (i = 0; i < activeThreads; i++)
2597 splitPoint.slaves[i] = 0;
2599 masterThread.splitPoint = &splitPoint;
2601 // If we are here it means we are not available
2602 assert(masterThread.state != THREAD_AVAILABLE);
2604 int workersCnt = 1; // At least the master is included
2606 // Allocate available threads setting state to THREAD_BOOKED
2607 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2608 if (thread_is_available(i, master))
2610 threads[i].state = THREAD_BOOKED;
2611 threads[i].splitPoint = &splitPoint;
2612 splitPoint.slaves[i] = 1;
2616 assert(Fake || workersCnt > 1);
2618 // We can release the lock because slave threads are already booked and master is not available
2619 lock_release(&mpLock);
2621 // Tell the threads that they have work to do. This will make them leave
2622 // their idle loop. But before copy search stack tail for each thread.
2623 for (i = 0; i < activeThreads; i++)
2624 if (i == master || splitPoint.slaves[i])
2626 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2628 assert(i == master || threads[i].state == THREAD_BOOKED);
2630 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2632 if (useSleepingThreads && i != master)
2633 wake_sleeping_thread(i);
2636 // Everything is set up. The master thread enters the idle loop, from
2637 // which it will instantly launch a search, because its state is
2638 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2639 // idle loop, which means that the main thread will return from the idle
2640 // loop when all threads have finished their work at this split point.
2641 idle_loop(master, &splitPoint);
2643 // We have returned from the idle loop, which means that all threads are
2644 // finished. Update alpha and bestValue, and return.
2647 *alpha = splitPoint.alpha;
2648 *bestValue = splitPoint.bestValue;
2649 masterThread.activeSplitPoints--;
2650 masterThread.splitPoint = splitPoint.parent;
2651 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2653 lock_release(&mpLock);
2657 // wake_sleeping_thread() wakes up the thread with the given threadID
2658 // when it is time to start a new search.
2660 void ThreadsManager::wake_sleeping_thread(int threadID) {
2662 lock_grab(&sleepLock[threadID]);
2663 cond_signal(&sleepCond[threadID]);
2664 lock_release(&sleepLock[threadID]);
2668 /// RootMove and RootMoveList method's definitions
2670 RootMove::RootMove() {
2673 pv_score = non_pv_score = -VALUE_INFINITE;
2677 RootMove& RootMove::operator=(const RootMove& rm) {
2679 const Move* src = rm.pv;
2682 // Avoid a costly full rm.pv[] copy
2683 do *dst++ = *src; while (*src++ != MOVE_NONE);
2686 pv_score = rm.pv_score;
2687 non_pv_score = rm.non_pv_score;
2691 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2692 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2693 // allow to always have a ponder move even when we fail high at root and also a
2694 // long PV to print that is important for position analysis.
2696 void RootMove::extract_pv_from_tt(Position& pos) {
2698 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2702 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2704 pos.do_move(pv[0], *st++);
2706 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2707 && tte->move() != MOVE_NONE
2708 && move_is_legal(pos, tte->move())
2710 && (!pos.is_draw() || ply < 2))
2712 pv[ply] = tte->move();
2713 pos.do_move(pv[ply++], *st++);
2715 pv[ply] = MOVE_NONE;
2717 do pos.undo_move(pv[--ply]); while (ply);
2720 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2721 // the PV back into the TT. This makes sure the old PV moves are searched
2722 // first, even if the old TT entries have been overwritten.
2724 void RootMove::insert_pv_in_tt(Position& pos) {
2726 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2729 Value v, m = VALUE_NONE;
2732 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2736 tte = TT.retrieve(k);
2738 // Don't overwrite exsisting correct entries
2739 if (!tte || tte->move() != pv[ply])
2741 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2742 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2744 pos.do_move(pv[ply], *st++);
2746 } while (pv[++ply] != MOVE_NONE);
2748 do pos.undo_move(pv[--ply]); while (ply);
2751 // pv_info_to_uci() returns a string with information on the current PV line
2752 // formatted according to UCI specification and eventually writes the info
2753 // to a log file. It is called at each iteration or after a new pv is found.
2755 std::string RootMove::pv_info_to_uci(Position& pos, Value alpha, Value beta, int pvLine) {
2757 std::stringstream s, l;
2760 while (*m != MOVE_NONE)
2763 s << "info depth " << Iteration // FIXME
2764 << " seldepth " << int(m - pv)
2765 << " multipv " << pvLine + 1
2766 << " score " << value_to_uci(pv_score)
2767 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2768 << " time " << current_search_time()
2769 << " nodes " << pos.nodes_searched()
2770 << " nps " << nps(pos)
2771 << " pv " << l.str();
2773 if (UseLogFile && pvLine == 0)
2775 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2776 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2778 LogFile << pretty_pv(pos, current_search_time(), Iteration, pv_score, t, pv) << endl;
2784 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) {
2786 SearchStack ss[PLY_MAX_PLUS_2];
2787 MoveStack mlist[MOVES_MAX];
2791 // Initialize search stack
2792 init_ss_array(ss, PLY_MAX_PLUS_2);
2793 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2795 // Generate all legal moves
2796 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2798 // Add each move to the RootMoveList's vector
2799 for (MoveStack* cur = mlist; cur != last; cur++)
2801 // If we have a searchMoves[] list then verify cur->move
2802 // is in the list before to add it.
2803 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2805 if (searchMoves[0] && *sm != cur->move)
2808 // Find a quick score for the move and add to the list
2809 pos.do_move(cur->move, st);
2812 rm.pv[0] = ss[0].currentMove = cur->move;
2813 rm.pv[1] = MOVE_NONE;
2814 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2817 pos.undo_move(cur->move);
2822 // Score root moves using the standard way used in main search, the moves
2823 // are scored according to the order in which are returned by MovePicker.
2824 // This is the second order score that is used to compare the moves when
2825 // the first order pv scores of both moves are equal.
2827 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2830 Value score = VALUE_ZERO;
2831 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2833 while ((move = mp.get_next_move()) != MOVE_NONE)
2834 for (Base::iterator it = begin(); it != end(); ++it)
2835 if (it->pv[0] == move)
2837 it->non_pv_score = score--;