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, Depth depth, 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 void init(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); }
158 // When formatting a move for std::cout we must know if we are in Chess960
159 // or not. To keep using the handy operator<<() on the move the trick is to
160 // embed this flag in the stream itself. Function-like named enum set960 is
161 // used as a custom manipulator and the stream internal general-purpose array,
162 // accessed through ios_base::iword(), is used to pass the flag to the move's
163 // operator<<() that will use it to properly format castling moves.
166 std::ostream& operator<< (std::ostream& os, const set960& f) {
168 os.iword(0) = int(f);
173 // Overload operator << for moves to make it easier to print moves in
174 // coordinate notation compatible with UCI protocol.
175 std::ostream& operator<<(std::ostream& os, Move m) {
177 bool chess960 = (os.iword(0) != 0); // See set960()
178 return os << move_to_uci(m, chess960);
186 // Maximum depth for razoring
187 const Depth RazorDepth = 4 * ONE_PLY;
189 // Dynamic razoring margin based on depth
190 inline Value razor_margin(Depth d) { return Value(0x200 + 0x10 * int(d)); }
192 // Maximum depth for use of dynamic threat detection when null move fails low
193 const Depth ThreatDepth = 5 * ONE_PLY;
195 // Step 9. Internal iterative deepening
197 // Minimum depth for use of internal iterative deepening
198 const Depth IIDDepth[2] = { 8 * ONE_PLY /* non-PV */, 5 * ONE_PLY /* PV */};
200 // At Non-PV nodes we do an internal iterative deepening search
201 // when the static evaluation is bigger then beta - IIDMargin.
202 const Value IIDMargin = Value(0x100);
204 // Step 11. Decide the new search depth
206 // Extensions. Configurable UCI options
207 // Array index 0 is used at non-PV nodes, index 1 at PV nodes.
208 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
209 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
211 // Minimum depth for use of singular extension
212 const Depth SingularExtensionDepth[2] = { 8 * ONE_PLY /* non-PV */, 6 * ONE_PLY /* PV */};
214 // If the TT move is at least SingularExtensionMargin better then the
215 // remaining ones we will extend it.
216 const Value SingularExtensionMargin = Value(0x20);
218 // Step 12. Futility pruning
220 // Futility margin for quiescence search
221 const Value FutilityMarginQS = Value(0x80);
223 // Futility lookup tables (initialized at startup) and their getter functions
224 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
225 int FutilityMoveCountArray[32]; // [depth]
227 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
228 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
230 // Step 14. Reduced search
232 // Reduction lookup tables (initialized at startup) and their getter functions
233 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
235 template <NodeType PV>
236 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
238 // Common adjustments
240 // Search depth at iteration 1
241 const Depth InitialDepth = ONE_PLY;
243 // Easy move margin. An easy move candidate must be at least this much
244 // better than the second best move.
245 const Value EasyMoveMargin = Value(0x200);
248 /// Namespace variables
253 // Pointer to root move list
259 // Time managment variables
260 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
261 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
262 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
267 std::ofstream LogFile;
269 // Multi-threads manager object
270 ThreadsManager ThreadsMgr;
272 // Node counters, used only by thread[0] but try to keep in different cache
273 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
274 bool SendSearchedNodes;
276 int NodesBetweenPolls = 30000;
283 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
285 template <NodeType PvNode, bool SpNode, bool Root>
286 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
288 template <NodeType PvNode>
289 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
291 template <NodeType PvNode>
292 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
294 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
295 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
298 template <NodeType PvNode>
299 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
301 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
302 bool connected_moves(const Position& pos, Move m1, Move m2);
303 bool value_is_mate(Value value);
304 Value value_to_tt(Value v, int ply);
305 Value value_from_tt(Value v, int ply);
306 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
307 bool connected_threat(const Position& pos, Move m, Move threat);
308 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
309 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
310 void update_killers(Move m, Move killers[]);
311 void update_gains(const Position& pos, Move move, Value before, Value after);
313 int current_search_time();
314 std::string value_to_uci(Value v);
315 int nps(const Position& pos);
316 void poll(const Position& pos);
317 void wait_for_stop_or_ponderhit();
318 void init_ss_array(SearchStack* ss, int size);
320 #if !defined(_MSC_VER)
321 void* init_thread(void* threadID);
323 DWORD WINAPI init_thread(LPVOID threadID);
327 // A dispatcher to choose among different move sources according to the type of node
328 template<bool SpNode, bool Root> struct MovePickerExt;
330 // In Root nodes use RootMoveList Rml as source
331 template<> struct MovePickerExt<false, true> {
333 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack*, Value)
334 : rm(Rml.begin()), firstCall(true) {}
336 Move get_next_move() {
343 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
345 int number_of_evasions() const { return (int)Rml.size(); }
347 RootMoveList::iterator rm;
351 // In SpNodes use split point's shared MovePicker as move source
352 template<> struct MovePickerExt<true, false> {
354 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack* ss, Value)
357 Move get_next_move() { return mp->get_next_move(); }
358 int number_of_evasions() const { return mp->number_of_evasions(); }
360 RootMoveList::iterator rm; // Dummy, never used
364 // Normal case, create and use a MovePicker object as source
365 template<> struct MovePickerExt<false, false> : public MovePicker {
367 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
368 SearchStack* ss, Value beta) : MovePicker(p, ttm, d, h, ss, beta) {}
370 RootMoveList::iterator rm; // Dummy, never used
380 /// init_threads(), exit_threads() and nodes_searched() are helpers to
381 /// give accessibility to some TM methods from outside of current file.
383 void init_threads() { ThreadsMgr.init_threads(); }
384 void exit_threads() { ThreadsMgr.exit_threads(); }
387 /// init_search() is called during startup. It initializes various lookup tables
391 int d; // depth (ONE_PLY == 2)
392 int hd; // half depth (ONE_PLY == 1)
395 // Init reductions array
396 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
398 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
399 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
400 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
401 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
404 // Init futility margins array
405 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
406 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
408 // Init futility move count array
409 for (d = 0; d < 32; d++)
410 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
414 /// perft() is our utility to verify move generation is bug free. All the legal
415 /// moves up to given depth are generated and counted and the sum returned.
417 int64_t perft(Position& pos, Depth depth)
419 MoveStack mlist[MOVES_MAX];
424 // Generate all legal moves
425 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
427 // If we are at the last ply we don't need to do and undo
428 // the moves, just to count them.
429 if (depth <= ONE_PLY)
430 return int(last - mlist);
432 // Loop through all legal moves
434 for (MoveStack* cur = mlist; cur != last; cur++)
437 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
438 sum += perft(pos, depth - ONE_PLY);
445 /// think() is the external interface to Stockfish's search, and is called when
446 /// the program receives the UCI 'go' command. It initializes various
447 /// search-related global variables, and calls id_loop(). It returns false
448 /// when a quit command is received during the search.
450 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
451 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
453 // Initialize global search variables
454 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
456 SearchStartTime = get_system_time();
457 ExactMaxTime = maxTime;
460 InfiniteSearch = infinite;
462 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
464 // Look for a book move, only during games, not tests
465 if (UseTimeManagement && Options["OwnBook"].value<bool>())
467 if (Options["Book File"].value<std::string>() != OpeningBook.name())
468 OpeningBook.open(Options["Book File"].value<std::string>());
470 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
471 if (bookMove != MOVE_NONE)
474 wait_for_stop_or_ponderhit();
476 cout << "bestmove " << bookMove << endl;
481 // Read UCI option values
482 TT.set_size(Options["Hash"].value<int>());
483 if (Options["Clear Hash"].value<bool>())
485 Options["Clear Hash"].set_value("false");
489 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
490 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
491 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
492 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
493 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
494 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
495 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
496 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
497 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
498 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
499 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
500 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
501 MultiPV = Options["MultiPV"].value<int>();
502 UseLogFile = Options["Use Search Log"].value<bool>();
504 read_evaluation_uci_options(pos.side_to_move());
506 // Set the number of active threads
507 ThreadsMgr.read_uci_options();
508 init_eval(ThreadsMgr.active_threads());
510 // Wake up needed threads
511 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
512 ThreadsMgr.wake_sleeping_thread(i);
515 int myTime = time[pos.side_to_move()];
516 int myIncrement = increment[pos.side_to_move()];
517 if (UseTimeManagement)
518 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
520 // Set best NodesBetweenPolls interval to avoid lagging under
521 // heavy time pressure.
523 NodesBetweenPolls = Min(MaxNodes, 30000);
524 else if (myTime && myTime < 1000)
525 NodesBetweenPolls = 1000;
526 else if (myTime && myTime < 5000)
527 NodesBetweenPolls = 5000;
529 NodesBetweenPolls = 30000;
531 // Write search information to log file
534 std::string name = Options["Search Log Filename"].value<std::string>();
535 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
537 LogFile << "Searching: " << pos.to_fen()
538 << "\ninfinite: " << infinite
539 << " ponder: " << ponder
540 << " time: " << myTime
541 << " increment: " << myIncrement
542 << " moves to go: " << movesToGo << endl;
545 // We're ready to start thinking. Call the iterative deepening loop function
546 Move ponderMove = MOVE_NONE;
547 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
549 // Print final search statistics
550 cout << "info nodes " << pos.nodes_searched()
551 << " nps " << nps(pos)
552 << " time " << current_search_time() << endl;
556 LogFile << "\nNodes: " << pos.nodes_searched()
557 << "\nNodes/second: " << nps(pos)
558 << "\nBest move: " << move_to_san(pos, bestMove);
561 pos.do_move(bestMove, st);
562 LogFile << "\nPonder move: "
563 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
566 // Return from think() with unchanged position
567 pos.undo_move(bestMove);
572 // This makes all the threads to go to sleep
573 ThreadsMgr.set_active_threads(1);
575 // If we are pondering or in infinite search, we shouldn't print the
576 // best move before we are told to do so.
577 if (!StopRequest && (Pondering || InfiniteSearch))
578 wait_for_stop_or_ponderhit();
580 // Could be both MOVE_NONE when searching on a stalemate position
581 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
589 // id_loop() is the main iterative deepening loop. It calls search()
590 // repeatedly with increasing depth until the allocated thinking time has
591 // been consumed, the user stops the search, or the maximum search depth is
594 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
596 SearchStack ss[PLY_MAX_PLUS_2];
599 Move EasyMove = MOVE_NONE;
600 Value value, alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
601 int researchCountFL, researchCountFH;
604 int bestMoveChanges[PLY_MAX_PLUS_2];
605 Value values[PLY_MAX_PLUS_2];
606 int aspirationDelta = 0;
608 // Moves to search are verified, scored and sorted
609 Rml.init(pos, searchMoves);
611 // Handle special case of searching on a mate/stale position
614 Value s = (pos.is_check() ? -VALUE_MATE : VALUE_DRAW);
616 cout << "info depth " << 1
617 << " score " << value_to_uci(s) << endl;
625 init_ss_array(ss, PLY_MAX_PLUS_2);
626 values[1] = Rml[0].pv_score;
629 // Send initial RootMoveList scoring (iteration 1)
630 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
631 << "info depth " << iteration
632 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
634 // Is one move significantly better than others after initial scoring ?
636 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
637 EasyMove = Rml[0].pv[0];
639 // Iterative deepening loop
640 while (iteration < PLY_MAX)
642 // Initialize iteration
644 Rml.bestMoveChanges = 0;
646 cout << "info depth " << iteration << endl;
648 // Calculate dynamic aspiration window based on previous iterations
649 if (MultiPV == 1 && iteration >= 6 && abs(values[iteration - 1]) < VALUE_KNOWN_WIN)
651 int prevDelta1 = values[iteration - 1] - values[iteration - 2];
652 int prevDelta2 = values[iteration - 2] - values[iteration - 3];
654 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
655 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
657 alpha = Max(values[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
658 beta = Min(values[iteration - 1] + aspirationDelta, VALUE_INFINITE);
661 depth = (iteration - 2) * ONE_PLY + InitialDepth;
663 researchCountFL = researchCountFH = 0;
665 // We start with small aspiration window and in case of fail high/low, we
666 // research with bigger window until we are not failing high/low anymore.
669 // Sort the moves before to (re)search
670 Rml.set_non_pv_scores(pos, Rml[0].pv[0], ss);
673 // Search to the current depth
674 value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
676 // Sort the moves and write PV lines to transposition table, in case
677 // the relevant entries have been overwritten during the search.
679 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
680 Rml[i].insert_pv_in_tt(pos);
682 bestMoveChanges[iteration] = Rml.bestMoveChanges;
687 assert(value >= alpha);
691 // Prepare for a research after a fail high, each time with a wider window
692 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
695 else if (value <= alpha)
697 AspirationFailLow = true;
698 StopOnPonderhit = false;
700 // Prepare for a research after a fail low, each time with a wider window
701 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
709 break; // Value cannot be trusted. Break out immediately!
711 //Save info about search result
712 values[iteration] = value;
714 // Drop the easy move if differs from the new best move
715 if (Rml[0].pv[0] != EasyMove)
716 EasyMove = MOVE_NONE;
718 if (UseTimeManagement)
721 bool noMoreTime = false;
723 // Stop search early if there is only a single legal move,
724 // we search up to Iteration 6 anyway to get a proper score.
725 if (iteration >= 6 && Rml.size() == 1)
728 // Stop search early when the last two iterations returned a mate score
730 && abs(values[iteration]) >= abs(VALUE_MATE) - 100
731 && abs(values[iteration-1]) >= abs(VALUE_MATE) - 100)
734 // Stop search early if one move seems to be much better than the others
736 && EasyMove == Rml[0].pv[0]
737 && ( ( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
738 && current_search_time() > TimeMgr.available_time() / 16)
739 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
740 && current_search_time() > TimeMgr.available_time() / 32)))
743 // Add some extra time if the best move has changed during the last two iterations
744 if (iteration > 5 && iteration <= 50)
745 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
747 // Stop search if most of MaxSearchTime is consumed at the end of the
748 // iteration. We probably don't have enough time to search the first
749 // move at the next iteration anyway.
750 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
756 StopOnPonderhit = true;
762 if (MaxDepth && iteration >= MaxDepth)
766 *ponderMove = Rml[0].pv[1];
771 // search<>() is the main search function for both PV and non-PV nodes and for
772 // normal and SplitPoint nodes. When called just after a split point the search
773 // is simpler because we have already probed the hash table, done a null move
774 // search, and searched the first move before splitting, we don't have to repeat
775 // all this work again. We also don't need to store anything to the hash table
776 // here: This is taken care of after we return from the split point.
778 template <NodeType PvNode, bool SpNode, bool Root>
779 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
781 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
782 assert(beta > alpha && beta <= VALUE_INFINITE);
783 assert(PvNode || alpha == beta - 1);
784 assert((Root || ply > 0) && ply < PLY_MAX);
785 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
787 Move movesSearched[MOVES_MAX];
792 Move ttMove, move, excludedMove, threatMove;
795 Value bestValue, value, oldAlpha;
796 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
797 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
798 bool mateThreat = false;
800 int threadID = pos.thread();
801 SplitPoint* sp = NULL;
803 refinedValue = bestValue = value = -VALUE_INFINITE;
805 isCheck = pos.is_check();
811 ttMove = excludedMove = MOVE_NONE;
812 threatMove = sp->threatMove;
813 mateThreat = sp->mateThreat;
814 goto split_point_start;
816 else {} // Hack to fix icc's "statement is unreachable" warning
818 // Step 1. Initialize node and poll. Polling can abort search
819 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
820 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
824 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
830 // Step 2. Check for aborted search and immediate draw
832 || ThreadsMgr.cutoff_at_splitpoint(threadID)
834 || ply >= PLY_MAX - 1)
837 // Step 3. Mate distance pruning
838 alpha = Max(value_mated_in(ply), alpha);
839 beta = Min(value_mate_in(ply+1), beta);
844 // Step 4. Transposition table lookup
846 // We don't want the score of a partial search to overwrite a previous full search
847 // TT value, so we use a different position key in case of an excluded move exists.
848 excludedMove = ss->excludedMove;
849 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
851 tte = TT.retrieve(posKey);
852 ttMove = tte ? tte->move() : MOVE_NONE;
854 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
855 // This is to avoid problems in the following areas:
857 // * Repetition draw detection
858 // * Fifty move rule detection
859 // * Searching for a mate
860 // * Printing of full PV line
861 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
864 ss->bestMove = ttMove; // Can be MOVE_NONE
865 return value_from_tt(tte->value(), ply);
868 // Step 5. Evaluate the position statically and
869 // update gain statistics of parent move.
871 ss->eval = ss->evalMargin = VALUE_NONE;
874 assert(tte->static_value() != VALUE_NONE);
876 ss->eval = tte->static_value();
877 ss->evalMargin = tte->static_value_margin();
878 refinedValue = refine_eval(tte, ss->eval, ply);
882 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
883 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
886 // Save gain for the parent non-capture move
888 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
890 // Step 6. Razoring (is omitted in PV nodes)
892 && depth < RazorDepth
894 && refinedValue < beta - razor_margin(depth)
895 && ttMove == MOVE_NONE
896 && !value_is_mate(beta)
897 && !pos.has_pawn_on_7th(pos.side_to_move()))
899 Value rbeta = beta - razor_margin(depth);
900 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
902 // Logically we should return (v + razor_margin(depth)), but
903 // surprisingly this did slightly weaker in tests.
907 // Step 7. Static null move pruning (is omitted in PV nodes)
908 // We're betting that the opponent doesn't have a move that will reduce
909 // the score by more than futility_margin(depth) if we do a null move.
912 && depth < RazorDepth
914 && refinedValue >= beta + futility_margin(depth, 0)
915 && !value_is_mate(beta)
916 && pos.non_pawn_material(pos.side_to_move()))
917 return refinedValue - futility_margin(depth, 0);
919 // Step 8. Null move search with verification search (is omitted in PV nodes)
924 && refinedValue >= beta
925 && !value_is_mate(beta)
926 && pos.non_pawn_material(pos.side_to_move()))
928 ss->currentMove = MOVE_NULL;
930 // Null move dynamic reduction based on depth
931 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
933 // Null move dynamic reduction based on value
934 if (refinedValue - beta > PawnValueMidgame)
937 pos.do_null_move(st);
938 (ss+1)->skipNullMove = true;
939 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
940 (ss+1)->skipNullMove = false;
941 pos.undo_null_move();
943 if (nullValue >= beta)
945 // Do not return unproven mate scores
946 if (nullValue >= value_mate_in(PLY_MAX))
949 if (depth < 6 * ONE_PLY)
952 // Do verification search at high depths
953 ss->skipNullMove = true;
954 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
955 ss->skipNullMove = false;
962 // The null move failed low, which means that we may be faced with
963 // some kind of threat. If the previous move was reduced, check if
964 // the move that refuted the null move was somehow connected to the
965 // move which was reduced. If a connection is found, return a fail
966 // low score (which will cause the reduced move to fail high in the
967 // parent node, which will trigger a re-search with full depth).
968 if (nullValue == value_mated_in(ply + 2))
971 threatMove = (ss+1)->bestMove;
972 if ( depth < ThreatDepth
974 && threatMove != MOVE_NONE
975 && connected_moves(pos, (ss-1)->currentMove, threatMove))
980 // Step 9. Internal iterative deepening
982 && depth >= IIDDepth[PvNode]
983 && ttMove == MOVE_NONE
984 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
986 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
988 ss->skipNullMove = true;
989 search<PvNode>(pos, ss, alpha, beta, d, ply);
990 ss->skipNullMove = false;
992 ttMove = ss->bestMove;
993 tte = TT.retrieve(posKey);
996 // Expensive mate threat detection (only for PV nodes)
997 if (PvNode && !Root) // FIXME
998 mateThreat = pos.has_mate_threat();
1000 split_point_start: // At split points actual search starts from here
1002 // Initialize a MovePicker object for the current position
1003 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1005 ss->bestMove = MOVE_NONE;
1006 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1007 futilityBase = ss->eval + ss->evalMargin;
1008 singularExtensionNode = !Root
1010 && depth >= SingularExtensionDepth[PvNode]
1013 && !excludedMove // Do not allow recursive singular extension search
1014 && (tte->type() & VALUE_TYPE_LOWER)
1015 && tte->depth() >= depth - 3 * ONE_PLY;
1021 lock_grab(&(sp->lock));
1022 bestValue = sp->bestValue;
1025 // Step 10. Loop through moves
1026 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1027 while ( bestValue < beta
1028 && (move = mp.get_next_move()) != MOVE_NONE
1029 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1031 assert(move_is_ok(move));
1035 moveCount = ++sp->moveCount;
1036 lock_release(&(sp->lock));
1038 else if (move == excludedMove)
1041 movesSearched[moveCount++] = move;
1045 // This is used by time management
1046 FirstRootMove = (moveCount == 1);
1048 // Save the current node count before the move is searched
1049 nodes = pos.nodes_searched();
1051 // If it's time to send nodes info, do it here where we have the
1052 // correct accumulated node counts searched by each thread.
1053 if (SendSearchedNodes)
1055 SendSearchedNodes = false;
1056 cout << "info nodes " << nodes
1057 << " nps " << nps(pos)
1058 << " time " << current_search_time() << endl;
1061 if (current_search_time() >= 1000)
1062 cout << "info currmove " << move
1063 << " currmovenumber " << moveCount << endl;
1066 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1067 moveIsCheck = pos.move_is_check(move, ci);
1068 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1070 // Step 11. Decide the new search depth
1071 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1073 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1074 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1075 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1076 // lower then ttValue minus a margin then we extend ttMove.
1077 if ( singularExtensionNode
1078 && move == tte->move()
1081 Value ttValue = value_from_tt(tte->value(), ply);
1083 if (abs(ttValue) < VALUE_KNOWN_WIN)
1085 Value b = ttValue - SingularExtensionMargin;
1086 ss->excludedMove = move;
1087 ss->skipNullMove = true;
1088 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1089 ss->skipNullMove = false;
1090 ss->excludedMove = MOVE_NONE;
1091 ss->bestMove = MOVE_NONE;
1097 // Update current move (this must be done after singular extension search)
1098 ss->currentMove = move;
1099 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1101 // Step 12. Futility pruning (is omitted in PV nodes)
1103 && !captureOrPromotion
1107 && !move_is_castle(move))
1109 // Move count based pruning
1110 if ( moveCount >= futility_move_count(depth)
1111 && !(threatMove && connected_threat(pos, move, threatMove))
1112 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1115 lock_grab(&(sp->lock));
1120 // Value based pruning
1121 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1122 // but fixing this made program slightly weaker.
1123 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1124 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1125 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1127 if (futilityValueScaled < beta)
1131 lock_grab(&(sp->lock));
1132 if (futilityValueScaled > sp->bestValue)
1133 sp->bestValue = bestValue = futilityValueScaled;
1135 else if (futilityValueScaled > bestValue)
1136 bestValue = futilityValueScaled;
1141 // Prune moves with negative SEE at low depths
1142 if ( predictedDepth < 2 * ONE_PLY
1143 && bestValue > value_mated_in(PLY_MAX)
1144 && pos.see_sign(move) < 0)
1147 lock_grab(&(sp->lock));
1153 // Step 13. Make the move
1154 pos.do_move(move, st, ci, moveIsCheck);
1156 // Step extra. pv search (only in PV nodes)
1157 // The first move in list is the expected PV
1160 // Aspiration window is disabled in multi-pv case
1161 if (Root && MultiPV > 1)
1162 alpha = -VALUE_INFINITE;
1164 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1168 // Step 14. Reduced depth search
1169 // If the move fails high will be re-searched at full depth.
1170 bool doFullDepthSearch = true;
1172 if ( depth >= 3 * ONE_PLY
1173 && !captureOrPromotion
1175 && !move_is_castle(move)
1176 && ss->killers[0] != move
1177 && ss->killers[1] != move)
1179 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1180 : reduction<PvNode>(depth, moveCount);
1183 alpha = SpNode ? sp->alpha : alpha;
1184 Depth d = newDepth - ss->reduction;
1185 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1187 doFullDepthSearch = (value > alpha);
1189 ss->reduction = DEPTH_ZERO; // Restore original reduction
1192 // Step 15. Full depth search
1193 if (doFullDepthSearch)
1195 alpha = SpNode ? sp->alpha : alpha;
1196 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1198 // Step extra. pv search (only in PV nodes)
1199 // Search only for possible new PV nodes, if instead value >= beta then
1200 // parent node fails low with value <= alpha and tries another move.
1201 if (PvNode && value > alpha && (Root || value < beta))
1202 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1206 // Step 16. Undo move
1207 pos.undo_move(move);
1209 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1211 // Step 17. Check for new best move
1214 lock_grab(&(sp->lock));
1215 bestValue = sp->bestValue;
1219 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1224 sp->bestValue = value;
1228 if (PvNode && value < beta) // We want always alpha < beta
1236 sp->betaCutoff = true;
1238 if (value == value_mate_in(ply + 1))
1239 ss->mateKiller = move;
1241 ss->bestMove = move;
1244 sp->parentSstack->bestMove = move;
1250 // Finished searching the move. If StopRequest is true, the search
1251 // was aborted because the user interrupted the search or because we
1252 // ran out of time. In this case, the return value of the search cannot
1253 // be trusted, and we break out of the loop without updating the best
1258 // Remember searched nodes counts for this move
1259 mp.rm->nodes += pos.nodes_searched() - nodes;
1261 // Step 17. Check for new best move
1262 if (!isPvMove && value <= alpha)
1263 mp.rm->pv_score = -VALUE_INFINITE;
1266 // PV move or new best move!
1269 ss->bestMove = move;
1270 mp.rm->pv_score = value;
1271 mp.rm->extract_pv_from_tt(pos);
1273 // We record how often the best move has been changed in each
1274 // iteration. This information is used for time managment: When
1275 // the best move changes frequently, we allocate some more time.
1276 if (!isPvMove && MultiPV == 1)
1277 Rml.bestMoveChanges++;
1279 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1280 // requires we send all the PV lines properly sorted.
1281 Rml.sort_multipv(moveCount);
1283 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1284 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1286 // Update alpha. In multi-pv we don't use aspiration window
1289 // Raise alpha to setup proper non-pv search upper bound
1291 alpha = bestValue = value;
1293 else // Set alpha equal to minimum score among the PV lines
1294 alpha = bestValue = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1296 } // PV move or new best move
1299 // Step 18. Check for split
1302 && depth >= ThreadsMgr.min_split_depth()
1303 && ThreadsMgr.active_threads() > 1
1305 && ThreadsMgr.available_thread_exists(threadID)
1307 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1308 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1309 threatMove, mateThreat, moveCount, (MovePicker*)&mp, PvNode);
1312 // Step 19. Check for mate and stalemate
1313 // All legal moves have been searched and if there are
1314 // no legal moves, it must be mate or stalemate.
1315 // If one move was excluded return fail low score.
1316 if (!SpNode && !moveCount)
1317 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1319 // Step 20. Update tables
1320 // If the search is not aborted, update the transposition table,
1321 // history counters, and killer moves.
1322 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1324 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1325 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1326 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1328 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1330 // Update killers and history only for non capture moves that fails high
1331 if ( bestValue >= beta
1332 && !pos.move_is_capture_or_promotion(move))
1334 update_history(pos, move, depth, movesSearched, moveCount);
1335 update_killers(move, ss->killers);
1341 // Here we have the lock still grabbed
1342 sp->slaves[threadID] = 0;
1343 sp->nodes += pos.nodes_searched();
1344 lock_release(&(sp->lock));
1347 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1352 // qsearch() is the quiescence search function, which is called by the main
1353 // search function when the remaining depth is zero (or, to be more precise,
1354 // less than ONE_PLY).
1356 template <NodeType PvNode>
1357 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1359 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1360 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1361 assert(PvNode || alpha == beta - 1);
1363 assert(ply > 0 && ply < PLY_MAX);
1364 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1368 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1369 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1372 Value oldAlpha = alpha;
1374 ss->bestMove = ss->currentMove = MOVE_NONE;
1376 // Check for an instant draw or maximum ply reached
1377 if (pos.is_draw() || ply >= PLY_MAX - 1)
1380 // Decide whether or not to include checks, this fixes also the type of
1381 // TT entry depth that we are going to use. Note that in qsearch we use
1382 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1383 isCheck = pos.is_check();
1384 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1386 // Transposition table lookup. At PV nodes, we don't use the TT for
1387 // pruning, but only for move ordering.
1388 tte = TT.retrieve(pos.get_key());
1389 ttMove = (tte ? tte->move() : MOVE_NONE);
1391 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1393 ss->bestMove = ttMove; // Can be MOVE_NONE
1394 return value_from_tt(tte->value(), ply);
1397 // Evaluate the position statically
1400 bestValue = futilityBase = -VALUE_INFINITE;
1401 ss->eval = evalMargin = VALUE_NONE;
1402 enoughMaterial = false;
1408 assert(tte->static_value() != VALUE_NONE);
1410 evalMargin = tte->static_value_margin();
1411 ss->eval = bestValue = tte->static_value();
1414 ss->eval = bestValue = evaluate(pos, evalMargin);
1416 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1418 // Stand pat. Return immediately if static value is at least beta
1419 if (bestValue >= beta)
1422 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1427 if (PvNode && bestValue > alpha)
1430 // Futility pruning parameters, not needed when in check
1431 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1432 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1435 // Initialize a MovePicker object for the current position, and prepare
1436 // to search the moves. Because the depth is <= 0 here, only captures,
1437 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1439 MovePicker mp(pos, ttMove, depth, H);
1442 // Loop through the moves until no moves remain or a beta cutoff occurs
1443 while ( alpha < beta
1444 && (move = mp.get_next_move()) != MOVE_NONE)
1446 assert(move_is_ok(move));
1448 moveIsCheck = pos.move_is_check(move, ci);
1456 && !move_is_promotion(move)
1457 && !pos.move_is_passed_pawn_push(move))
1459 futilityValue = futilityBase
1460 + pos.endgame_value_of_piece_on(move_to(move))
1461 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1463 if (futilityValue < alpha)
1465 if (futilityValue > bestValue)
1466 bestValue = futilityValue;
1471 // Detect non-capture evasions that are candidate to be pruned
1472 evasionPrunable = isCheck
1473 && bestValue > value_mated_in(PLY_MAX)
1474 && !pos.move_is_capture(move)
1475 && !pos.can_castle(pos.side_to_move());
1477 // Don't search moves with negative SEE values
1479 && (!isCheck || evasionPrunable)
1481 && !move_is_promotion(move)
1482 && pos.see_sign(move) < 0)
1485 // Don't search useless checks
1490 && !pos.move_is_capture_or_promotion(move)
1491 && ss->eval + PawnValueMidgame / 4 < beta
1492 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1494 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1495 bestValue = ss->eval + PawnValueMidgame / 4;
1500 // Update current move
1501 ss->currentMove = move;
1503 // Make and search the move
1504 pos.do_move(move, st, ci, moveIsCheck);
1505 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1506 pos.undo_move(move);
1508 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1511 if (value > bestValue)
1517 ss->bestMove = move;
1522 // All legal moves have been searched. A special case: If we're in check
1523 // and no legal moves were found, it is checkmate.
1524 if (isCheck && bestValue == -VALUE_INFINITE)
1525 return value_mated_in(ply);
1527 // Update transposition table
1528 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1529 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1531 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1537 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1538 // bestValue is updated only when returning false because in that case move
1541 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1543 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1544 Square from, to, ksq, victimSq;
1547 Value futilityValue, bv = *bestValue;
1549 from = move_from(move);
1551 them = opposite_color(pos.side_to_move());
1552 ksq = pos.king_square(them);
1553 kingAtt = pos.attacks_from<KING>(ksq);
1554 pc = pos.piece_on(from);
1556 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1557 oldAtt = pos.attacks_from(pc, from, occ);
1558 newAtt = pos.attacks_from(pc, to, occ);
1560 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1561 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1563 if (!(b && (b & (b - 1))))
1566 // Rule 2. Queen contact check is very dangerous
1567 if ( type_of_piece(pc) == QUEEN
1568 && bit_is_set(kingAtt, to))
1571 // Rule 3. Creating new double threats with checks
1572 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1576 victimSq = pop_1st_bit(&b);
1577 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1579 // Note that here we generate illegal "double move"!
1580 if ( futilityValue >= beta
1581 && pos.see_sign(make_move(from, victimSq)) >= 0)
1584 if (futilityValue > bv)
1588 // Update bestValue only if check is not dangerous (because we will prune the move)
1594 // connected_moves() tests whether two moves are 'connected' in the sense
1595 // that the first move somehow made the second move possible (for instance
1596 // if the moving piece is the same in both moves). The first move is assumed
1597 // to be the move that was made to reach the current position, while the
1598 // second move is assumed to be a move from the current position.
1600 bool connected_moves(const Position& pos, Move m1, Move m2) {
1602 Square f1, t1, f2, t2;
1605 assert(m1 && move_is_ok(m1));
1606 assert(m2 && move_is_ok(m2));
1608 // Case 1: The moving piece is the same in both moves
1614 // Case 2: The destination square for m2 was vacated by m1
1620 // Case 3: Moving through the vacated square
1621 if ( piece_is_slider(pos.piece_on(f2))
1622 && bit_is_set(squares_between(f2, t2), f1))
1625 // Case 4: The destination square for m2 is defended by the moving piece in m1
1626 p = pos.piece_on(t1);
1627 if (bit_is_set(pos.attacks_from(p, t1), t2))
1630 // Case 5: Discovered check, checking piece is the piece moved in m1
1631 if ( piece_is_slider(p)
1632 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1633 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1635 // discovered_check_candidates() works also if the Position's side to
1636 // move is the opposite of the checking piece.
1637 Color them = opposite_color(pos.side_to_move());
1638 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1640 if (bit_is_set(dcCandidates, f2))
1647 // value_is_mate() checks if the given value is a mate one eventually
1648 // compensated for the ply.
1650 bool value_is_mate(Value value) {
1652 assert(abs(value) <= VALUE_INFINITE);
1654 return value <= value_mated_in(PLY_MAX)
1655 || value >= value_mate_in(PLY_MAX);
1659 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1660 // "plies to mate from the current ply". Non-mate scores are unchanged.
1661 // The function is called before storing a value to the transposition table.
1663 Value value_to_tt(Value v, int ply) {
1665 if (v >= value_mate_in(PLY_MAX))
1668 if (v <= value_mated_in(PLY_MAX))
1675 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1676 // the transposition table to a mate score corrected for the current ply.
1678 Value value_from_tt(Value v, int ply) {
1680 if (v >= value_mate_in(PLY_MAX))
1683 if (v <= value_mated_in(PLY_MAX))
1690 // extension() decides whether a move should be searched with normal depth,
1691 // or with extended depth. Certain classes of moves (checking moves, in
1692 // particular) are searched with bigger depth than ordinary moves and in
1693 // any case are marked as 'dangerous'. Note that also if a move is not
1694 // extended, as example because the corresponding UCI option is set to zero,
1695 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1696 template <NodeType PvNode>
1697 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1698 bool singleEvasion, bool mateThreat, bool* dangerous) {
1700 assert(m != MOVE_NONE);
1702 Depth result = DEPTH_ZERO;
1703 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1707 if (moveIsCheck && pos.see_sign(m) >= 0)
1708 result += CheckExtension[PvNode];
1711 result += SingleEvasionExtension[PvNode];
1714 result += MateThreatExtension[PvNode];
1717 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1719 Color c = pos.side_to_move();
1720 if (relative_rank(c, move_to(m)) == RANK_7)
1722 result += PawnPushTo7thExtension[PvNode];
1725 if (pos.pawn_is_passed(c, move_to(m)))
1727 result += PassedPawnExtension[PvNode];
1732 if ( captureOrPromotion
1733 && pos.type_of_piece_on(move_to(m)) != PAWN
1734 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1735 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1736 && !move_is_promotion(m)
1739 result += PawnEndgameExtension[PvNode];
1744 && captureOrPromotion
1745 && pos.type_of_piece_on(move_to(m)) != PAWN
1746 && pos.see_sign(m) >= 0)
1748 result += ONE_PLY / 2;
1752 return Min(result, ONE_PLY);
1756 // connected_threat() tests whether it is safe to forward prune a move or if
1757 // is somehow coonected to the threat move returned by null search.
1759 bool connected_threat(const Position& pos, Move m, Move threat) {
1761 assert(move_is_ok(m));
1762 assert(threat && move_is_ok(threat));
1763 assert(!pos.move_is_check(m));
1764 assert(!pos.move_is_capture_or_promotion(m));
1765 assert(!pos.move_is_passed_pawn_push(m));
1767 Square mfrom, mto, tfrom, tto;
1769 mfrom = move_from(m);
1771 tfrom = move_from(threat);
1772 tto = move_to(threat);
1774 // Case 1: Don't prune moves which move the threatened piece
1778 // Case 2: If the threatened piece has value less than or equal to the
1779 // value of the threatening piece, don't prune move which defend it.
1780 if ( pos.move_is_capture(threat)
1781 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1782 || pos.type_of_piece_on(tfrom) == KING)
1783 && pos.move_attacks_square(m, tto))
1786 // Case 3: If the moving piece in the threatened move is a slider, don't
1787 // prune safe moves which block its ray.
1788 if ( piece_is_slider(pos.piece_on(tfrom))
1789 && bit_is_set(squares_between(tfrom, tto), mto)
1790 && pos.see_sign(m) >= 0)
1797 // ok_to_use_TT() returns true if a transposition table score
1798 // can be used at a given point in search.
1800 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1802 Value v = value_from_tt(tte->value(), ply);
1804 return ( tte->depth() >= depth
1805 || v >= Max(value_mate_in(PLY_MAX), beta)
1806 || v < Min(value_mated_in(PLY_MAX), beta))
1808 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1809 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1813 // refine_eval() returns the transposition table score if
1814 // possible otherwise falls back on static position evaluation.
1816 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1820 Value v = value_from_tt(tte->value(), ply);
1822 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1823 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1830 // update_history() registers a good move that produced a beta-cutoff
1831 // in history and marks as failures all the other moves of that ply.
1833 void update_history(const Position& pos, Move move, Depth depth,
1834 Move movesSearched[], int moveCount) {
1836 Value bonus = Value(int(depth) * int(depth));
1838 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1840 for (int i = 0; i < moveCount - 1; i++)
1842 m = movesSearched[i];
1846 if (!pos.move_is_capture_or_promotion(m))
1847 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1852 // update_killers() add a good move that produced a beta-cutoff
1853 // among the killer moves of that ply.
1855 void update_killers(Move m, Move killers[]) {
1857 if (m == killers[0])
1860 killers[1] = killers[0];
1865 // update_gains() updates the gains table of a non-capture move given
1866 // the static position evaluation before and after the move.
1868 void update_gains(const Position& pos, Move m, Value before, Value after) {
1871 && before != VALUE_NONE
1872 && after != VALUE_NONE
1873 && pos.captured_piece_type() == PIECE_TYPE_NONE
1874 && !move_is_special(m))
1875 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1879 // init_ss_array() does a fast reset of the first entries of a SearchStack
1880 // array and of all the excludedMove and skipNullMove entries.
1882 void init_ss_array(SearchStack* ss, int size) {
1884 for (int i = 0; i < size; i++, ss++)
1886 ss->excludedMove = MOVE_NONE;
1887 ss->skipNullMove = false;
1888 ss->reduction = DEPTH_ZERO;
1892 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1897 // value_to_uci() converts a value to a string suitable for use with the UCI
1898 // protocol specifications:
1900 // cp <x> The score from the engine's point of view in centipawns.
1901 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1902 // use negative values for y.
1904 std::string value_to_uci(Value v) {
1906 std::stringstream s;
1908 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1909 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1911 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1917 // current_search_time() returns the number of milliseconds which have passed
1918 // since the beginning of the current search.
1920 int current_search_time() {
1922 return get_system_time() - SearchStartTime;
1926 // nps() computes the current nodes/second count
1928 int nps(const Position& pos) {
1930 int t = current_search_time();
1931 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1935 // poll() performs two different functions: It polls for user input, and it
1936 // looks at the time consumed so far and decides if it's time to abort the
1939 void poll(const Position& pos) {
1941 static int lastInfoTime;
1942 int t = current_search_time();
1945 if (input_available())
1947 // We are line oriented, don't read single chars
1948 std::string command;
1950 if (!std::getline(std::cin, command))
1953 if (command == "quit")
1955 // Quit the program as soon as possible
1957 QuitRequest = StopRequest = true;
1960 else if (command == "stop")
1962 // Stop calculating as soon as possible, but still send the "bestmove"
1963 // and possibly the "ponder" token when finishing the search.
1967 else if (command == "ponderhit")
1969 // The opponent has played the expected move. GUI sends "ponderhit" if
1970 // we were told to ponder on the same move the opponent has played. We
1971 // should continue searching but switching from pondering to normal search.
1974 if (StopOnPonderhit)
1979 // Print search information
1983 else if (lastInfoTime > t)
1984 // HACK: Must be a new search where we searched less than
1985 // NodesBetweenPolls nodes during the first second of search.
1988 else if (t - lastInfoTime >= 1000)
1995 if (dbg_show_hit_rate)
1996 dbg_print_hit_rate();
1998 // Send info on searched nodes as soon as we return to root
1999 SendSearchedNodes = true;
2002 // Should we stop the search?
2006 bool stillAtFirstMove = FirstRootMove
2007 && !AspirationFailLow
2008 && t > TimeMgr.available_time();
2010 bool noMoreTime = t > TimeMgr.maximum_time()
2011 || stillAtFirstMove;
2013 if ( (UseTimeManagement && noMoreTime)
2014 || (ExactMaxTime && t >= ExactMaxTime)
2015 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2020 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2021 // while the program is pondering. The point is to work around a wrinkle in
2022 // the UCI protocol: When pondering, the engine is not allowed to give a
2023 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2024 // We simply wait here until one of these commands is sent, and return,
2025 // after which the bestmove and pondermove will be printed.
2027 void wait_for_stop_or_ponderhit() {
2029 std::string command;
2033 // Wait for a command from stdin
2034 if (!std::getline(std::cin, command))
2037 if (command == "quit")
2042 else if (command == "ponderhit" || command == "stop")
2048 // init_thread() is the function which is called when a new thread is
2049 // launched. It simply calls the idle_loop() function with the supplied
2050 // threadID. There are two versions of this function; one for POSIX
2051 // threads and one for Windows threads.
2053 #if !defined(_MSC_VER)
2055 void* init_thread(void* threadID) {
2057 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2063 DWORD WINAPI init_thread(LPVOID threadID) {
2065 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2072 /// The ThreadsManager class
2075 // read_uci_options() updates number of active threads and other internal
2076 // parameters according to the UCI options values. It is called before
2077 // to start a new search.
2079 void ThreadsManager::read_uci_options() {
2081 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2082 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2083 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2084 activeThreads = Options["Threads"].value<int>();
2088 // idle_loop() is where the threads are parked when they have no work to do.
2089 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2090 // object for which the current thread is the master.
2092 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2094 assert(threadID >= 0 && threadID < MAX_THREADS);
2097 bool allFinished = false;
2101 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2102 // master should exit as last one.
2103 if (allThreadsShouldExit)
2106 threads[threadID].state = THREAD_TERMINATED;
2110 // If we are not thinking, wait for a condition to be signaled
2111 // instead of wasting CPU time polling for work.
2112 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2113 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2115 assert(!sp || useSleepingThreads);
2116 assert(threadID != 0 || useSleepingThreads);
2118 if (threads[threadID].state == THREAD_INITIALIZING)
2119 threads[threadID].state = THREAD_AVAILABLE;
2121 // Grab the lock to avoid races with wake_sleeping_thread()
2122 lock_grab(&sleepLock[threadID]);
2124 // If we are master and all slaves have finished do not go to sleep
2125 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2126 allFinished = (i == activeThreads);
2128 if (allFinished || allThreadsShouldExit)
2130 lock_release(&sleepLock[threadID]);
2134 // Do sleep here after retesting sleep conditions
2135 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2136 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2138 lock_release(&sleepLock[threadID]);
2141 // If this thread has been assigned work, launch a search
2142 if (threads[threadID].state == THREAD_WORKISWAITING)
2144 assert(!allThreadsShouldExit);
2146 threads[threadID].state = THREAD_SEARCHING;
2148 // Here we call search() with SplitPoint template parameter set to true
2149 SplitPoint* tsp = threads[threadID].splitPoint;
2150 Position pos(*tsp->pos, threadID);
2151 SearchStack* ss = tsp->sstack[threadID] + 1;
2155 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2157 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2159 assert(threads[threadID].state == THREAD_SEARCHING);
2161 threads[threadID].state = THREAD_AVAILABLE;
2163 // Wake up master thread so to allow it to return from the idle loop in
2164 // case we are the last slave of the split point.
2165 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2166 wake_sleeping_thread(tsp->master);
2169 // If this thread is the master of a split point and all slaves have
2170 // finished their work at this split point, return from the idle loop.
2171 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2172 allFinished = (i == activeThreads);
2176 // Because sp->slaves[] is reset under lock protection,
2177 // be sure sp->lock has been released before to return.
2178 lock_grab(&(sp->lock));
2179 lock_release(&(sp->lock));
2181 // In helpful master concept a master can help only a sub-tree, and
2182 // because here is all finished is not possible master is booked.
2183 assert(threads[threadID].state == THREAD_AVAILABLE);
2185 threads[threadID].state = THREAD_SEARCHING;
2192 // init_threads() is called during startup. It launches all helper threads,
2193 // and initializes the split point stack and the global locks and condition
2196 void ThreadsManager::init_threads() {
2198 int i, arg[MAX_THREADS];
2201 // Initialize global locks
2204 for (i = 0; i < MAX_THREADS; i++)
2206 lock_init(&sleepLock[i]);
2207 cond_init(&sleepCond[i]);
2210 // Initialize splitPoints[] locks
2211 for (i = 0; i < MAX_THREADS; i++)
2212 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2213 lock_init(&(threads[i].splitPoints[j].lock));
2215 // Will be set just before program exits to properly end the threads
2216 allThreadsShouldExit = false;
2218 // Threads will be put all threads to sleep as soon as created
2221 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2222 threads[0].state = THREAD_SEARCHING;
2223 for (i = 1; i < MAX_THREADS; i++)
2224 threads[i].state = THREAD_INITIALIZING;
2226 // Launch the helper threads
2227 for (i = 1; i < MAX_THREADS; i++)
2231 #if !defined(_MSC_VER)
2232 pthread_t pthread[1];
2233 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2234 pthread_detach(pthread[0]);
2236 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2240 cout << "Failed to create thread number " << i << endl;
2244 // Wait until the thread has finished launching and is gone to sleep
2245 while (threads[i].state == THREAD_INITIALIZING) {}
2250 // exit_threads() is called when the program exits. It makes all the
2251 // helper threads exit cleanly.
2253 void ThreadsManager::exit_threads() {
2255 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2257 // Wake up all the threads and waits for termination
2258 for (int i = 1; i < MAX_THREADS; i++)
2260 wake_sleeping_thread(i);
2261 while (threads[i].state != THREAD_TERMINATED) {}
2264 // Now we can safely destroy the locks
2265 for (int i = 0; i < MAX_THREADS; i++)
2266 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2267 lock_destroy(&(threads[i].splitPoints[j].lock));
2269 lock_destroy(&mpLock);
2271 // Now we can safely destroy the wait conditions
2272 for (int i = 0; i < MAX_THREADS; i++)
2274 lock_destroy(&sleepLock[i]);
2275 cond_destroy(&sleepCond[i]);
2280 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2281 // the thread's currently active split point, or in some ancestor of
2282 // the current split point.
2284 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2286 assert(threadID >= 0 && threadID < activeThreads);
2288 SplitPoint* sp = threads[threadID].splitPoint;
2290 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2295 // thread_is_available() checks whether the thread with threadID "slave" is
2296 // available to help the thread with threadID "master" at a split point. An
2297 // obvious requirement is that "slave" must be idle. With more than two
2298 // threads, this is not by itself sufficient: If "slave" is the master of
2299 // some active split point, it is only available as a slave to the other
2300 // threads which are busy searching the split point at the top of "slave"'s
2301 // split point stack (the "helpful master concept" in YBWC terminology).
2303 bool ThreadsManager::thread_is_available(int slave, int master) const {
2305 assert(slave >= 0 && slave < activeThreads);
2306 assert(master >= 0 && master < activeThreads);
2307 assert(activeThreads > 1);
2309 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2312 // Make a local copy to be sure doesn't change under our feet
2313 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2315 // No active split points means that the thread is available as
2316 // a slave for any other thread.
2317 if (localActiveSplitPoints == 0 || activeThreads == 2)
2320 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2321 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2322 // could have been set to 0 by another thread leading to an out of bound access.
2323 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2330 // available_thread_exists() tries to find an idle thread which is available as
2331 // a slave for the thread with threadID "master".
2333 bool ThreadsManager::available_thread_exists(int master) const {
2335 assert(master >= 0 && master < activeThreads);
2336 assert(activeThreads > 1);
2338 for (int i = 0; i < activeThreads; i++)
2339 if (thread_is_available(i, master))
2346 // split() does the actual work of distributing the work at a node between
2347 // several available threads. If it does not succeed in splitting the
2348 // node (because no idle threads are available, or because we have no unused
2349 // split point objects), the function immediately returns. If splitting is
2350 // possible, a SplitPoint object is initialized with all the data that must be
2351 // copied to the helper threads and we tell our helper threads that they have
2352 // been assigned work. This will cause them to instantly leave their idle loops and
2353 // call search().When all threads have returned from search() then split() returns.
2355 template <bool Fake>
2356 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2357 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2358 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2359 assert(pos.is_ok());
2360 assert(ply > 0 && ply < PLY_MAX);
2361 assert(*bestValue >= -VALUE_INFINITE);
2362 assert(*bestValue <= *alpha);
2363 assert(*alpha < beta);
2364 assert(beta <= VALUE_INFINITE);
2365 assert(depth > DEPTH_ZERO);
2366 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2367 assert(activeThreads > 1);
2369 int i, master = pos.thread();
2370 Thread& masterThread = threads[master];
2374 // If no other thread is available to help us, or if we have too many
2375 // active split points, don't split.
2376 if ( !available_thread_exists(master)
2377 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2379 lock_release(&mpLock);
2383 // Pick the next available split point object from the split point stack
2384 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2386 // Initialize the split point object
2387 splitPoint.parent = masterThread.splitPoint;
2388 splitPoint.master = master;
2389 splitPoint.betaCutoff = false;
2390 splitPoint.ply = ply;
2391 splitPoint.depth = depth;
2392 splitPoint.threatMove = threatMove;
2393 splitPoint.mateThreat = mateThreat;
2394 splitPoint.alpha = *alpha;
2395 splitPoint.beta = beta;
2396 splitPoint.pvNode = pvNode;
2397 splitPoint.bestValue = *bestValue;
2399 splitPoint.moveCount = moveCount;
2400 splitPoint.pos = &pos;
2401 splitPoint.nodes = 0;
2402 splitPoint.parentSstack = ss;
2403 for (i = 0; i < activeThreads; i++)
2404 splitPoint.slaves[i] = 0;
2406 masterThread.splitPoint = &splitPoint;
2408 // If we are here it means we are not available
2409 assert(masterThread.state != THREAD_AVAILABLE);
2411 int workersCnt = 1; // At least the master is included
2413 // Allocate available threads setting state to THREAD_BOOKED
2414 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2415 if (thread_is_available(i, master))
2417 threads[i].state = THREAD_BOOKED;
2418 threads[i].splitPoint = &splitPoint;
2419 splitPoint.slaves[i] = 1;
2423 assert(Fake || workersCnt > 1);
2425 // We can release the lock because slave threads are already booked and master is not available
2426 lock_release(&mpLock);
2428 // Tell the threads that they have work to do. This will make them leave
2429 // their idle loop. But before copy search stack tail for each thread.
2430 for (i = 0; i < activeThreads; i++)
2431 if (i == master || splitPoint.slaves[i])
2433 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2435 assert(i == master || threads[i].state == THREAD_BOOKED);
2437 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2439 if (useSleepingThreads && i != master)
2440 wake_sleeping_thread(i);
2443 // Everything is set up. The master thread enters the idle loop, from
2444 // which it will instantly launch a search, because its state is
2445 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2446 // idle loop, which means that the main thread will return from the idle
2447 // loop when all threads have finished their work at this split point.
2448 idle_loop(master, &splitPoint);
2450 // We have returned from the idle loop, which means that all threads are
2451 // finished. Update alpha and bestValue, and return.
2454 *alpha = splitPoint.alpha;
2455 *bestValue = splitPoint.bestValue;
2456 masterThread.activeSplitPoints--;
2457 masterThread.splitPoint = splitPoint.parent;
2458 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2460 lock_release(&mpLock);
2464 // wake_sleeping_thread() wakes up the thread with the given threadID
2465 // when it is time to start a new search.
2467 void ThreadsManager::wake_sleeping_thread(int threadID) {
2469 lock_grab(&sleepLock[threadID]);
2470 cond_signal(&sleepCond[threadID]);
2471 lock_release(&sleepLock[threadID]);
2475 /// RootMove and RootMoveList method's definitions
2477 RootMove::RootMove() {
2480 pv_score = non_pv_score = -VALUE_INFINITE;
2484 RootMove& RootMove::operator=(const RootMove& rm) {
2486 const Move* src = rm.pv;
2489 // Avoid a costly full rm.pv[] copy
2490 do *dst++ = *src; while (*src++ != MOVE_NONE);
2493 pv_score = rm.pv_score;
2494 non_pv_score = rm.non_pv_score;
2498 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2499 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2500 // allow to always have a ponder move even when we fail high at root and also a
2501 // long PV to print that is important for position analysis.
2503 void RootMove::extract_pv_from_tt(Position& pos) {
2505 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2509 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2511 pos.do_move(pv[0], *st++);
2513 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2514 && tte->move() != MOVE_NONE
2515 && move_is_legal(pos, tte->move())
2517 && (!pos.is_draw() || ply < 2))
2519 pv[ply] = tte->move();
2520 pos.do_move(pv[ply++], *st++);
2522 pv[ply] = MOVE_NONE;
2524 do pos.undo_move(pv[--ply]); while (ply);
2527 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2528 // the PV back into the TT. This makes sure the old PV moves are searched
2529 // first, even if the old TT entries have been overwritten.
2531 void RootMove::insert_pv_in_tt(Position& pos) {
2533 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2536 Value v, m = VALUE_NONE;
2539 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2543 tte = TT.retrieve(k);
2545 // Don't overwrite exsisting correct entries
2546 if (!tte || tte->move() != pv[ply])
2548 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2549 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2551 pos.do_move(pv[ply], *st++);
2553 } while (pv[++ply] != MOVE_NONE);
2555 do pos.undo_move(pv[--ply]); while (ply);
2558 // pv_info_to_uci() returns a string with information on the current PV line
2559 // formatted according to UCI specification and eventually writes the info
2560 // to a log file. It is called at each iteration or after a new pv is found.
2562 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2564 std::stringstream s, l;
2567 while (*m != MOVE_NONE)
2570 s << "info depth " << depth / ONE_PLY
2571 << " seldepth " << int(m - pv)
2572 << " multipv " << pvLine + 1
2573 << " score " << value_to_uci(pv_score)
2574 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2575 << " time " << current_search_time()
2576 << " nodes " << pos.nodes_searched()
2577 << " nps " << nps(pos)
2578 << " pv " << l.str();
2580 if (UseLogFile && pvLine == 0)
2582 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2583 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2585 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2591 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2593 SearchStack ss[PLY_MAX_PLUS_2];
2594 MoveStack mlist[MOVES_MAX];
2598 // Initialize search stack
2599 init_ss_array(ss, PLY_MAX_PLUS_2);
2600 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2601 bestMoveChanges = 0;
2604 // Generate all legal moves
2605 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2607 // Add each move to the RootMoveList's vector
2608 for (MoveStack* cur = mlist; cur != last; cur++)
2610 // If we have a searchMoves[] list then verify cur->move
2611 // is in the list before to add it.
2612 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2614 if (searchMoves[0] && *sm != cur->move)
2617 // Find a quick score for the move and add to the list
2618 pos.do_move(cur->move, st);
2621 rm.pv[0] = ss[0].currentMove = cur->move;
2622 rm.pv[1] = MOVE_NONE;
2623 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2626 pos.undo_move(cur->move);
2631 // Score root moves using the standard way used in main search, the moves
2632 // are scored according to the order in which are returned by MovePicker.
2633 // This is the second order score that is used to compare the moves when
2634 // the first order pv scores of both moves are equal.
2636 void RootMoveList::set_non_pv_scores(const Position& pos, Move ttm, SearchStack* ss)
2639 Value score = VALUE_ZERO;
2640 MovePicker mp(pos, ttm, ONE_PLY, H, ss);
2642 while ((move = mp.get_next_move()) != MOVE_NONE)
2643 for (Base::iterator it = begin(); it != end(); ++it)
2644 if (it->pv[0] == move)
2646 it->non_pv_score = score--;