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 sort() { insertion_sort<RootMove, Base::iterator>(begin(), end()); }
150 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 // Time managment variables
258 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
259 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
260 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
265 std::ofstream LogFile;
267 // Multi-threads manager object
268 ThreadsManager ThreadsMgr;
270 // Node counters, used only by thread[0] but try to keep in different cache
271 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
272 bool SendSearchedNodes;
274 int NodesBetweenPolls = 30000;
281 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
283 template <NodeType PvNode, bool SpNode, bool Root>
284 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
286 template <NodeType PvNode>
287 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
289 template <NodeType PvNode>
290 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
292 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
293 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
296 template <NodeType PvNode>
297 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
299 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
300 bool connected_moves(const Position& pos, Move m1, Move m2);
301 bool value_is_mate(Value value);
302 Value value_to_tt(Value v, int ply);
303 Value value_from_tt(Value v, int ply);
304 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
305 bool connected_threat(const Position& pos, Move m, Move threat);
306 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
307 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
308 void update_killers(Move m, Move killers[]);
309 void update_gains(const Position& pos, Move move, Value before, Value after);
311 int current_search_time();
312 std::string value_to_uci(Value v);
313 int nps(const Position& pos);
314 void poll(const Position& pos);
315 void wait_for_stop_or_ponderhit();
316 void init_ss_array(SearchStack* ss, int size);
318 #if !defined(_MSC_VER)
319 void* init_thread(void* threadID);
321 DWORD WINAPI init_thread(LPVOID threadID);
325 // A dispatcher to choose among different move sources according to the type of node
326 template<bool SpNode, bool Root> struct MovePickerExt;
328 // In Root nodes use RootMoveList Rml as source. Score and sort the moves before to search them.
329 template<> struct MovePickerExt<false, true> : private MovePicker {
331 MovePickerExt(const Position& p, Move, Depth, const History& h, SearchStack* ss, Value beta)
332 : MovePicker(p, Rml[0].pv[0], ONE_PLY, h, ss, beta), firstCall(true) { // FIXME use depth
335 Value score = VALUE_ZERO;
337 // Score root moves using the standard way used in main search, the moves
338 // are scored according to the order in which are returned by MovePicker.
339 // This is the second order score that is used to compare the moves when
340 // the first order pv scores of both moves are equal.
341 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
342 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
343 if (rm->pv[0] == move)
345 rm->non_pv_score = score--;
353 Move get_next_move() {
360 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
362 int number_of_evasions() const { return (int)Rml.size(); }
364 RootMoveList::iterator rm;
368 // In SpNodes use split point's shared MovePicker as move source
369 template<> struct MovePickerExt<true, false> {
371 MovePickerExt(const Position&, Move, Depth, const History&, SearchStack* ss, Value)
374 Move get_next_move() { return mp->get_next_move(); }
375 int number_of_evasions() const { return mp->number_of_evasions(); }
377 RootMoveList::iterator rm; // Dummy, never used
381 // Normal case, create and use a MovePicker object as source
382 template<> struct MovePickerExt<false, false> : public MovePicker {
384 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
385 SearchStack* ss, Value beta) : MovePicker(p, ttm, d, h, ss, beta) {}
387 RootMoveList::iterator rm; // Dummy, never used
397 /// init_threads(), exit_threads() and nodes_searched() are helpers to
398 /// give accessibility to some TM methods from outside of current file.
400 void init_threads() { ThreadsMgr.init_threads(); }
401 void exit_threads() { ThreadsMgr.exit_threads(); }
404 /// init_search() is called during startup. It initializes various lookup tables
408 int d; // depth (ONE_PLY == 2)
409 int hd; // half depth (ONE_PLY == 1)
412 // Init reductions array
413 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
415 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
416 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
417 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
418 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
421 // Init futility margins array
422 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
423 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
425 // Init futility move count array
426 for (d = 0; d < 32; d++)
427 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
431 /// perft() is our utility to verify move generation is bug free. All the legal
432 /// moves up to given depth are generated and counted and the sum returned.
434 int64_t perft(Position& pos, Depth depth)
436 MoveStack mlist[MOVES_MAX];
441 // Generate all legal moves
442 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
444 // If we are at the last ply we don't need to do and undo
445 // the moves, just to count them.
446 if (depth <= ONE_PLY)
447 return int(last - mlist);
449 // Loop through all legal moves
451 for (MoveStack* cur = mlist; cur != last; cur++)
454 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
455 sum += perft(pos, depth - ONE_PLY);
462 /// think() is the external interface to Stockfish's search, and is called when
463 /// the program receives the UCI 'go' command. It initializes various
464 /// search-related global variables, and calls id_loop(). It returns false
465 /// when a quit command is received during the search.
467 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
468 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
470 // Initialize global search variables
471 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
473 SearchStartTime = get_system_time();
474 ExactMaxTime = maxTime;
477 InfiniteSearch = infinite;
479 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
481 // Look for a book move, only during games, not tests
482 if (UseTimeManagement && Options["OwnBook"].value<bool>())
484 if (Options["Book File"].value<std::string>() != OpeningBook.name())
485 OpeningBook.open(Options["Book File"].value<std::string>());
487 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
488 if (bookMove != MOVE_NONE)
491 wait_for_stop_or_ponderhit();
493 cout << "bestmove " << bookMove << endl;
498 // Read UCI option values
499 TT.set_size(Options["Hash"].value<int>());
500 if (Options["Clear Hash"].value<bool>())
502 Options["Clear Hash"].set_value("false");
506 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
507 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
508 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
509 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
510 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
511 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
512 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
513 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
514 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
515 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
516 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
517 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
518 MultiPV = Options["MultiPV"].value<int>();
519 UseLogFile = Options["Use Search Log"].value<bool>();
521 read_evaluation_uci_options(pos.side_to_move());
523 // Set the number of active threads
524 ThreadsMgr.read_uci_options();
525 init_eval(ThreadsMgr.active_threads());
527 // Wake up needed threads
528 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
529 ThreadsMgr.wake_sleeping_thread(i);
532 int myTime = time[pos.side_to_move()];
533 int myIncrement = increment[pos.side_to_move()];
534 if (UseTimeManagement)
535 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
537 // Set best NodesBetweenPolls interval to avoid lagging under
538 // heavy time pressure.
540 NodesBetweenPolls = Min(MaxNodes, 30000);
541 else if (myTime && myTime < 1000)
542 NodesBetweenPolls = 1000;
543 else if (myTime && myTime < 5000)
544 NodesBetweenPolls = 5000;
546 NodesBetweenPolls = 30000;
548 // Write search information to log file
551 std::string name = Options["Search Log Filename"].value<std::string>();
552 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
554 LogFile << "Searching: " << pos.to_fen()
555 << "\ninfinite: " << infinite
556 << " ponder: " << ponder
557 << " time: " << myTime
558 << " increment: " << myIncrement
559 << " moves to go: " << movesToGo << endl;
562 // We're ready to start thinking. Call the iterative deepening loop function
563 Move ponderMove = MOVE_NONE;
564 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
566 // Print final search statistics
567 cout << "info nodes " << pos.nodes_searched()
568 << " nps " << nps(pos)
569 << " time " << current_search_time() << endl;
573 LogFile << "\nNodes: " << pos.nodes_searched()
574 << "\nNodes/second: " << nps(pos)
575 << "\nBest move: " << move_to_san(pos, bestMove);
578 pos.do_move(bestMove, st);
579 LogFile << "\nPonder move: "
580 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
583 // Return from think() with unchanged position
584 pos.undo_move(bestMove);
589 // This makes all the threads to go to sleep
590 ThreadsMgr.set_active_threads(1);
592 // If we are pondering or in infinite search, we shouldn't print the
593 // best move before we are told to do so.
594 if (!StopRequest && (Pondering || InfiniteSearch))
595 wait_for_stop_or_ponderhit();
597 // Could be both MOVE_NONE when searching on a stalemate position
598 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
606 // id_loop() is the main iterative deepening loop. It calls search()
607 // repeatedly with increasing depth until the allocated thinking time has
608 // been consumed, the user stops the search, or the maximum search depth is
611 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
613 SearchStack ss[PLY_MAX_PLUS_2];
614 Value bestValues[PLY_MAX_PLUS_2];
615 int bestMoveChanges[PLY_MAX_PLUS_2];
616 int iteration, researchCountFL, researchCountFH, aspirationDelta;
617 Value value, alpha, beta;
621 // Moves to search are verified, scored and sorted
622 Rml.init(pos, searchMoves);
624 // Initialize FIXME move before Rml.init()
627 init_ss_array(ss, PLY_MAX_PLUS_2);
628 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
629 EasyMove = MOVE_NONE;
633 // Handle special case of searching on a mate/stale position
636 cout << "info depth " << iteration << " score "
637 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
643 // Send initial scoring (iteration 1)
644 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
645 << "info depth " << iteration
646 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
648 // Is one move significantly better than others after initial scoring ?
650 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
651 EasyMove = Rml[0].pv[0];
653 // Iterative deepening loop
654 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
656 cout << "info depth " << iteration << endl;
658 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
659 depth = (iteration - 2) * ONE_PLY + InitialDepth;
661 // Calculate dynamic aspiration window based on previous iterations
662 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
664 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
665 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
667 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
668 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
670 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
671 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
674 // We start with small aspiration window and in case of fail high/low, we
675 // research with bigger window until we are not failing high/low anymore.
678 // Search to the current depth
679 value = search<PV, false, true>(pos, ss, alpha, beta, depth, 0);
681 // Sort root moves and write PV lines to transposition table, in case
682 // the relevant entries have been overwritten during the search.
684 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
685 Rml[i].insert_pv_in_tt(pos);
687 // Value cannot be trusted. Break out immediately!
689 break; // FIXME move to 'while' condition
691 assert(value >= alpha);
693 bestMoveChanges[iteration] = Rml.bestMoveChanges; // FIXME move outside fail high/low loop
695 // In case of failing high/low increase aspiration window and research,
696 // otherwise exit the fail high/low loop.
699 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
702 else if (value <= alpha)
704 AspirationFailLow = true;
705 StopOnPonderhit = false;
707 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
714 //Save info about search result
715 bestValues[iteration] = value;
717 // Drop the easy move if differs from the new best move
718 if (Rml[0].pv[0] != EasyMove)
719 EasyMove = MOVE_NONE;
721 if (UseTimeManagement && !StopRequest)
724 bool noMoreTime = false;
726 // Stop search early if there is only a single legal move,
727 // we search up to Iteration 6 anyway to get a proper score.
728 if (iteration >= 6 && Rml.size() == 1)
731 // Stop search early when the last two iterations returned a mate score
733 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
734 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
737 // Stop search early if one move seems to be much better than the others
739 && EasyMove == Rml[0].pv[0]
740 && ( ( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
741 && current_search_time() > TimeMgr.available_time() / 16)
742 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
743 && current_search_time() > TimeMgr.available_time() / 32)))
746 // Add some extra time if the best move has changed during the last two iterations
747 if (iteration > 5 && iteration <= 50)
748 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
750 // Stop search if most of MaxSearchTime is consumed at the end of the
751 // iteration. We probably don't have enough time to search the first
752 // move at the next iteration anyway.
753 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
759 StopOnPonderhit = true;
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;
819 // Step 1. Initialize node and poll. Polling can abort search
820 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
821 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
823 if (!Root) // FIXME remove
825 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
831 // Step 2. Check for aborted search and immediate draw
833 || ThreadsMgr.cutoff_at_splitpoint(threadID)
835 || ply >= PLY_MAX - 1)
838 // Step 3. Mate distance pruning
839 alpha = Max(value_mated_in(ply), alpha);
840 beta = Min(value_mate_in(ply+1), beta);
845 // Step 4. Transposition table lookup
847 // We don't want the score of a partial search to overwrite a previous full search
848 // TT value, so we use a different position key in case of an excluded move exists.
849 excludedMove = ss->excludedMove;
850 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
852 tte = TT.retrieve(posKey);
853 ttMove = tte ? tte->move() : MOVE_NONE;
855 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
856 // This is to avoid problems in the following areas:
858 // * Repetition draw detection
859 // * Fifty move rule detection
860 // * Searching for a mate
861 // * Printing of full PV line
862 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
865 ss->bestMove = ttMove; // Can be MOVE_NONE
866 return value_from_tt(tte->value(), ply);
869 // Step 5. Evaluate the position statically and
870 // update gain statistics of parent move.
872 ss->eval = ss->evalMargin = VALUE_NONE;
875 assert(tte->static_value() != VALUE_NONE);
877 ss->eval = tte->static_value();
878 ss->evalMargin = tte->static_value_margin();
879 refinedValue = refine_eval(tte, ss->eval, ply);
883 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
884 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
887 // Save gain for the parent non-capture move
889 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
891 // Step 6. Razoring (is omitted in PV nodes)
893 && depth < RazorDepth
895 && refinedValue < beta - razor_margin(depth)
896 && ttMove == MOVE_NONE
897 && !value_is_mate(beta)
898 && !pos.has_pawn_on_7th(pos.side_to_move()))
900 Value rbeta = beta - razor_margin(depth);
901 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
903 // Logically we should return (v + razor_margin(depth)), but
904 // surprisingly this did slightly weaker in tests.
908 // Step 7. Static null move pruning (is omitted in PV nodes)
909 // We're betting that the opponent doesn't have a move that will reduce
910 // the score by more than futility_margin(depth) if we do a null move.
913 && depth < RazorDepth
915 && refinedValue >= beta + futility_margin(depth, 0)
916 && !value_is_mate(beta)
917 && pos.non_pawn_material(pos.side_to_move()))
918 return refinedValue - futility_margin(depth, 0);
920 // Step 8. Null move search with verification search (is omitted in PV nodes)
925 && refinedValue >= beta
926 && !value_is_mate(beta)
927 && pos.non_pawn_material(pos.side_to_move()))
929 ss->currentMove = MOVE_NULL;
931 // Null move dynamic reduction based on depth
932 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
934 // Null move dynamic reduction based on value
935 if (refinedValue - beta > PawnValueMidgame)
938 pos.do_null_move(st);
939 (ss+1)->skipNullMove = true;
940 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
941 (ss+1)->skipNullMove = false;
942 pos.undo_null_move();
944 if (nullValue >= beta)
946 // Do not return unproven mate scores
947 if (nullValue >= value_mate_in(PLY_MAX))
950 if (depth < 6 * ONE_PLY)
953 // Do verification search at high depths
954 ss->skipNullMove = true;
955 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
956 ss->skipNullMove = false;
963 // The null move failed low, which means that we may be faced with
964 // some kind of threat. If the previous move was reduced, check if
965 // the move that refuted the null move was somehow connected to the
966 // move which was reduced. If a connection is found, return a fail
967 // low score (which will cause the reduced move to fail high in the
968 // parent node, which will trigger a re-search with full depth).
969 if (nullValue == value_mated_in(ply + 2))
972 threatMove = (ss+1)->bestMove;
973 if ( depth < ThreatDepth
975 && threatMove != MOVE_NONE
976 && connected_moves(pos, (ss-1)->currentMove, threatMove))
981 // Step 9. Internal iterative deepening
983 && depth >= IIDDepth[PvNode]
984 && ttMove == MOVE_NONE
985 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
987 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
989 ss->skipNullMove = true;
990 search<PvNode>(pos, ss, alpha, beta, d, ply);
991 ss->skipNullMove = false;
993 ttMove = ss->bestMove;
994 tte = TT.retrieve(posKey);
997 // Expensive mate threat detection (only for PV nodes)
998 if (PvNode && !Root) // FIXME
999 mateThreat = pos.has_mate_threat();
1001 split_point_start: // At split points actual search starts from here
1003 // Initialize a MovePicker object for the current position
1004 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
1006 ss->bestMove = MOVE_NONE;
1007 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
1008 futilityBase = ss->eval + ss->evalMargin;
1009 singularExtensionNode = !Root
1011 && depth >= SingularExtensionDepth[PvNode]
1014 && !excludedMove // Do not allow recursive singular extension search
1015 && (tte->type() & VALUE_TYPE_LOWER)
1016 && tte->depth() >= depth - 3 * ONE_PLY;
1019 lock_grab(&(sp->lock));
1020 bestValue = sp->bestValue;
1023 // Step 10. Loop through moves
1024 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1025 while ( bestValue < beta
1026 && (move = mp.get_next_move()) != MOVE_NONE
1027 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1029 assert(move_is_ok(move));
1033 moveCount = ++sp->moveCount;
1034 lock_release(&(sp->lock));
1036 else if (move == excludedMove)
1039 movesSearched[moveCount++] = move;
1043 // This is used by time management
1044 FirstRootMove = (moveCount == 1);
1046 // Save the current node count before the move is searched
1047 nodes = pos.nodes_searched();
1049 // If it's time to send nodes info, do it here where we have the
1050 // correct accumulated node counts searched by each thread.
1051 if (SendSearchedNodes)
1053 SendSearchedNodes = false;
1054 cout << "info nodes " << nodes
1055 << " nps " << nps(pos)
1056 << " time " << current_search_time() << endl;
1059 if (current_search_time() >= 1000)
1060 cout << "info currmove " << move
1061 << " currmovenumber " << moveCount << endl;
1064 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1065 moveIsCheck = pos.move_is_check(move, ci);
1066 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1068 // Step 11. Decide the new search depth
1069 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1071 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1072 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1073 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1074 // lower then ttValue minus a margin then we extend ttMove.
1075 if ( singularExtensionNode
1076 && move == tte->move()
1079 Value ttValue = value_from_tt(tte->value(), ply);
1081 if (abs(ttValue) < VALUE_KNOWN_WIN)
1083 Value b = ttValue - SingularExtensionMargin;
1084 ss->excludedMove = move;
1085 ss->skipNullMove = true;
1086 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1087 ss->skipNullMove = false;
1088 ss->excludedMove = MOVE_NONE;
1089 ss->bestMove = MOVE_NONE;
1095 // Update current move (this must be done after singular extension search)
1096 ss->currentMove = move;
1097 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1099 // Step 12. Futility pruning (is omitted in PV nodes)
1101 && !captureOrPromotion
1105 && !move_is_castle(move))
1107 // Move count based pruning
1108 if ( moveCount >= futility_move_count(depth)
1109 && !(threatMove && connected_threat(pos, move, threatMove))
1110 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1113 lock_grab(&(sp->lock));
1118 // Value based pruning
1119 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1120 // but fixing this made program slightly weaker.
1121 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1122 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1123 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1125 if (futilityValueScaled < beta)
1129 lock_grab(&(sp->lock));
1130 if (futilityValueScaled > sp->bestValue)
1131 sp->bestValue = bestValue = futilityValueScaled;
1133 else if (futilityValueScaled > bestValue)
1134 bestValue = futilityValueScaled;
1139 // Prune moves with negative SEE at low depths
1140 if ( predictedDepth < 2 * ONE_PLY
1141 && bestValue > value_mated_in(PLY_MAX)
1142 && pos.see_sign(move) < 0)
1145 lock_grab(&(sp->lock));
1151 // Step 13. Make the move
1152 pos.do_move(move, st, ci, moveIsCheck);
1154 // Step extra. pv search (only in PV nodes)
1155 // The first move in list is the expected PV
1158 // Aspiration window is disabled in multi-pv case
1159 if (Root && MultiPV > 1)
1160 alpha = -VALUE_INFINITE;
1162 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1166 // Step 14. Reduced depth search
1167 // If the move fails high will be re-searched at full depth.
1168 bool doFullDepthSearch = true;
1170 if ( depth >= 3 * ONE_PLY
1171 && !captureOrPromotion
1173 && !move_is_castle(move)
1174 && ss->killers[0] != move
1175 && ss->killers[1] != move)
1177 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1178 : reduction<PvNode>(depth, moveCount);
1181 alpha = SpNode ? sp->alpha : alpha;
1182 Depth d = newDepth - ss->reduction;
1183 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1185 doFullDepthSearch = (value > alpha);
1187 ss->reduction = DEPTH_ZERO; // Restore original reduction
1190 // Step 15. Full depth search
1191 if (doFullDepthSearch)
1193 alpha = SpNode ? sp->alpha : alpha;
1194 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1196 // Step extra. pv search (only in PV nodes)
1197 // Search only for possible new PV nodes, if instead value >= beta then
1198 // parent node fails low with value <= alpha and tries another move.
1199 if (PvNode && value > alpha && (Root || value < beta))
1200 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1204 // Step 16. Undo move
1205 pos.undo_move(move);
1207 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1209 // Step 17. Check for new best move
1212 lock_grab(&(sp->lock));
1213 bestValue = sp->bestValue;
1217 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1222 sp->bestValue = value;
1226 if (PvNode && value < beta) // We want always alpha < beta
1234 sp->betaCutoff = true;
1236 if (value == value_mate_in(ply + 1))
1237 ss->mateKiller = move;
1239 ss->bestMove = move;
1242 sp->parentSstack->bestMove = move;
1248 // To avoid to exit with bestValue == -VALUE_INFINITE
1249 if (value > bestValue)
1252 // Finished searching the move. If StopRequest is true, the search
1253 // was aborted because the user interrupted the search or because we
1254 // ran out of time. In this case, the return value of the search cannot
1255 // be trusted, and we break out of the loop without updating the best
1260 // Remember searched nodes counts for this move
1261 mp.rm->nodes += pos.nodes_searched() - nodes;
1263 // Step 17. Check for new best move
1264 if (!isPvMove && value <= alpha)
1265 mp.rm->pv_score = -VALUE_INFINITE;
1268 // PV move or new best move!
1271 ss->bestMove = move;
1272 mp.rm->pv_score = value;
1273 mp.rm->extract_pv_from_tt(pos);
1275 // We record how often the best move has been changed in each
1276 // iteration. This information is used for time managment: When
1277 // the best move changes frequently, we allocate some more time.
1278 if (!isPvMove && MultiPV == 1)
1279 Rml.bestMoveChanges++;
1281 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1282 // requires we send all the PV lines properly sorted.
1283 Rml.sort_multipv(moveCount);
1285 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1286 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1288 // Update alpha. In multi-pv we don't use aspiration window, so
1289 // set alpha equal to minimum score among the PV lines.
1291 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1292 else if (value > alpha)
1295 } // PV move or new best move
1298 // Step 18. Check for split
1301 && depth >= ThreadsMgr.min_split_depth()
1302 && ThreadsMgr.active_threads() > 1
1304 && ThreadsMgr.available_thread_exists(threadID)
1306 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1307 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1308 threatMove, mateThreat, moveCount, (MovePicker*)&mp, PvNode);
1311 // Step 19. Check for mate and stalemate
1312 // All legal moves have been searched and if there are
1313 // no legal moves, it must be mate or stalemate.
1314 // If one move was excluded return fail low score.
1315 if (!SpNode && !moveCount)
1316 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1318 // Step 20. Update tables
1319 // If the search is not aborted, update the transposition table,
1320 // history counters, and killer moves.
1321 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1323 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1324 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1325 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1327 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1329 // Update killers and history only for non capture moves that fails high
1330 if ( bestValue >= beta
1331 && !pos.move_is_capture_or_promotion(move))
1333 update_history(pos, move, depth, movesSearched, moveCount);
1334 update_killers(move, ss->killers);
1340 // Here we have the lock still grabbed
1341 sp->slaves[threadID] = 0;
1342 sp->nodes += pos.nodes_searched();
1343 lock_release(&(sp->lock));
1346 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1351 // qsearch() is the quiescence search function, which is called by the main
1352 // search function when the remaining depth is zero (or, to be more precise,
1353 // less than ONE_PLY).
1355 template <NodeType PvNode>
1356 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1358 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1359 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1360 assert(PvNode || alpha == beta - 1);
1362 assert(ply > 0 && ply < PLY_MAX);
1363 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1367 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1368 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1371 Value oldAlpha = alpha;
1373 ss->bestMove = ss->currentMove = MOVE_NONE;
1375 // Check for an instant draw or maximum ply reached
1376 if (pos.is_draw() || ply >= PLY_MAX - 1)
1379 // Decide whether or not to include checks, this fixes also the type of
1380 // TT entry depth that we are going to use. Note that in qsearch we use
1381 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1382 isCheck = pos.is_check();
1383 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1385 // Transposition table lookup. At PV nodes, we don't use the TT for
1386 // pruning, but only for move ordering.
1387 tte = TT.retrieve(pos.get_key());
1388 ttMove = (tte ? tte->move() : MOVE_NONE);
1390 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1392 ss->bestMove = ttMove; // Can be MOVE_NONE
1393 return value_from_tt(tte->value(), ply);
1396 // Evaluate the position statically
1399 bestValue = futilityBase = -VALUE_INFINITE;
1400 ss->eval = evalMargin = VALUE_NONE;
1401 enoughMaterial = false;
1407 assert(tte->static_value() != VALUE_NONE);
1409 evalMargin = tte->static_value_margin();
1410 ss->eval = bestValue = tte->static_value();
1413 ss->eval = bestValue = evaluate(pos, evalMargin);
1415 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1417 // Stand pat. Return immediately if static value is at least beta
1418 if (bestValue >= beta)
1421 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1426 if (PvNode && bestValue > alpha)
1429 // Futility pruning parameters, not needed when in check
1430 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1431 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1434 // Initialize a MovePicker object for the current position, and prepare
1435 // to search the moves. Because the depth is <= 0 here, only captures,
1436 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1438 MovePicker mp(pos, ttMove, depth, H);
1441 // Loop through the moves until no moves remain or a beta cutoff occurs
1442 while ( alpha < beta
1443 && (move = mp.get_next_move()) != MOVE_NONE)
1445 assert(move_is_ok(move));
1447 moveIsCheck = pos.move_is_check(move, ci);
1455 && !move_is_promotion(move)
1456 && !pos.move_is_passed_pawn_push(move))
1458 futilityValue = futilityBase
1459 + pos.endgame_value_of_piece_on(move_to(move))
1460 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1462 if (futilityValue < alpha)
1464 if (futilityValue > bestValue)
1465 bestValue = futilityValue;
1470 // Detect non-capture evasions that are candidate to be pruned
1471 evasionPrunable = isCheck
1472 && bestValue > value_mated_in(PLY_MAX)
1473 && !pos.move_is_capture(move)
1474 && !pos.can_castle(pos.side_to_move());
1476 // Don't search moves with negative SEE values
1478 && (!isCheck || evasionPrunable)
1480 && !move_is_promotion(move)
1481 && pos.see_sign(move) < 0)
1484 // Don't search useless checks
1489 && !pos.move_is_capture_or_promotion(move)
1490 && ss->eval + PawnValueMidgame / 4 < beta
1491 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1493 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1494 bestValue = ss->eval + PawnValueMidgame / 4;
1499 // Update current move
1500 ss->currentMove = move;
1502 // Make and search the move
1503 pos.do_move(move, st, ci, moveIsCheck);
1504 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1505 pos.undo_move(move);
1507 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1510 if (value > bestValue)
1516 ss->bestMove = move;
1521 // All legal moves have been searched. A special case: If we're in check
1522 // and no legal moves were found, it is checkmate.
1523 if (isCheck && bestValue == -VALUE_INFINITE)
1524 return value_mated_in(ply);
1526 // Update transposition table
1527 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1528 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1530 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1536 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1537 // bestValue is updated only when returning false because in that case move
1540 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1542 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1543 Square from, to, ksq, victimSq;
1546 Value futilityValue, bv = *bestValue;
1548 from = move_from(move);
1550 them = opposite_color(pos.side_to_move());
1551 ksq = pos.king_square(them);
1552 kingAtt = pos.attacks_from<KING>(ksq);
1553 pc = pos.piece_on(from);
1555 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1556 oldAtt = pos.attacks_from(pc, from, occ);
1557 newAtt = pos.attacks_from(pc, to, occ);
1559 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1560 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1562 if (!(b && (b & (b - 1))))
1565 // Rule 2. Queen contact check is very dangerous
1566 if ( type_of_piece(pc) == QUEEN
1567 && bit_is_set(kingAtt, to))
1570 // Rule 3. Creating new double threats with checks
1571 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1575 victimSq = pop_1st_bit(&b);
1576 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1578 // Note that here we generate illegal "double move"!
1579 if ( futilityValue >= beta
1580 && pos.see_sign(make_move(from, victimSq)) >= 0)
1583 if (futilityValue > bv)
1587 // Update bestValue only if check is not dangerous (because we will prune the move)
1593 // connected_moves() tests whether two moves are 'connected' in the sense
1594 // that the first move somehow made the second move possible (for instance
1595 // if the moving piece is the same in both moves). The first move is assumed
1596 // to be the move that was made to reach the current position, while the
1597 // second move is assumed to be a move from the current position.
1599 bool connected_moves(const Position& pos, Move m1, Move m2) {
1601 Square f1, t1, f2, t2;
1604 assert(m1 && move_is_ok(m1));
1605 assert(m2 && move_is_ok(m2));
1607 // Case 1: The moving piece is the same in both moves
1613 // Case 2: The destination square for m2 was vacated by m1
1619 // Case 3: Moving through the vacated square
1620 if ( piece_is_slider(pos.piece_on(f2))
1621 && bit_is_set(squares_between(f2, t2), f1))
1624 // Case 4: The destination square for m2 is defended by the moving piece in m1
1625 p = pos.piece_on(t1);
1626 if (bit_is_set(pos.attacks_from(p, t1), t2))
1629 // Case 5: Discovered check, checking piece is the piece moved in m1
1630 if ( piece_is_slider(p)
1631 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1632 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1634 // discovered_check_candidates() works also if the Position's side to
1635 // move is the opposite of the checking piece.
1636 Color them = opposite_color(pos.side_to_move());
1637 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1639 if (bit_is_set(dcCandidates, f2))
1646 // value_is_mate() checks if the given value is a mate one eventually
1647 // compensated for the ply.
1649 bool value_is_mate(Value value) {
1651 assert(abs(value) <= VALUE_INFINITE);
1653 return value <= value_mated_in(PLY_MAX)
1654 || value >= value_mate_in(PLY_MAX);
1658 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1659 // "plies to mate from the current ply". Non-mate scores are unchanged.
1660 // The function is called before storing a value to the transposition table.
1662 Value value_to_tt(Value v, int ply) {
1664 if (v >= value_mate_in(PLY_MAX))
1667 if (v <= value_mated_in(PLY_MAX))
1674 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1675 // the transposition table to a mate score corrected for the current ply.
1677 Value value_from_tt(Value v, int ply) {
1679 if (v >= value_mate_in(PLY_MAX))
1682 if (v <= value_mated_in(PLY_MAX))
1689 // extension() decides whether a move should be searched with normal depth,
1690 // or with extended depth. Certain classes of moves (checking moves, in
1691 // particular) are searched with bigger depth than ordinary moves and in
1692 // any case are marked as 'dangerous'. Note that also if a move is not
1693 // extended, as example because the corresponding UCI option is set to zero,
1694 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1695 template <NodeType PvNode>
1696 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1697 bool singleEvasion, bool mateThreat, bool* dangerous) {
1699 assert(m != MOVE_NONE);
1701 Depth result = DEPTH_ZERO;
1702 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1706 if (moveIsCheck && pos.see_sign(m) >= 0)
1707 result += CheckExtension[PvNode];
1710 result += SingleEvasionExtension[PvNode];
1713 result += MateThreatExtension[PvNode];
1716 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1718 Color c = pos.side_to_move();
1719 if (relative_rank(c, move_to(m)) == RANK_7)
1721 result += PawnPushTo7thExtension[PvNode];
1724 if (pos.pawn_is_passed(c, move_to(m)))
1726 result += PassedPawnExtension[PvNode];
1731 if ( captureOrPromotion
1732 && pos.type_of_piece_on(move_to(m)) != PAWN
1733 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1734 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1735 && !move_is_promotion(m)
1738 result += PawnEndgameExtension[PvNode];
1743 && captureOrPromotion
1744 && pos.type_of_piece_on(move_to(m)) != PAWN
1745 && pos.see_sign(m) >= 0)
1747 result += ONE_PLY / 2;
1751 return Min(result, ONE_PLY);
1755 // connected_threat() tests whether it is safe to forward prune a move or if
1756 // is somehow coonected to the threat move returned by null search.
1758 bool connected_threat(const Position& pos, Move m, Move threat) {
1760 assert(move_is_ok(m));
1761 assert(threat && move_is_ok(threat));
1762 assert(!pos.move_is_check(m));
1763 assert(!pos.move_is_capture_or_promotion(m));
1764 assert(!pos.move_is_passed_pawn_push(m));
1766 Square mfrom, mto, tfrom, tto;
1768 mfrom = move_from(m);
1770 tfrom = move_from(threat);
1771 tto = move_to(threat);
1773 // Case 1: Don't prune moves which move the threatened piece
1777 // Case 2: If the threatened piece has value less than or equal to the
1778 // value of the threatening piece, don't prune move which defend it.
1779 if ( pos.move_is_capture(threat)
1780 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1781 || pos.type_of_piece_on(tfrom) == KING)
1782 && pos.move_attacks_square(m, tto))
1785 // Case 3: If the moving piece in the threatened move is a slider, don't
1786 // prune safe moves which block its ray.
1787 if ( piece_is_slider(pos.piece_on(tfrom))
1788 && bit_is_set(squares_between(tfrom, tto), mto)
1789 && pos.see_sign(m) >= 0)
1796 // ok_to_use_TT() returns true if a transposition table score
1797 // can be used at a given point in search.
1799 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1801 Value v = value_from_tt(tte->value(), ply);
1803 return ( tte->depth() >= depth
1804 || v >= Max(value_mate_in(PLY_MAX), beta)
1805 || v < Min(value_mated_in(PLY_MAX), beta))
1807 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1808 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1812 // refine_eval() returns the transposition table score if
1813 // possible otherwise falls back on static position evaluation.
1815 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1819 Value v = value_from_tt(tte->value(), ply);
1821 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1822 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1829 // update_history() registers a good move that produced a beta-cutoff
1830 // in history and marks as failures all the other moves of that ply.
1832 void update_history(const Position& pos, Move move, Depth depth,
1833 Move movesSearched[], int moveCount) {
1835 Value bonus = Value(int(depth) * int(depth));
1837 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1839 for (int i = 0; i < moveCount - 1; i++)
1841 m = movesSearched[i];
1845 if (!pos.move_is_capture_or_promotion(m))
1846 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1851 // update_killers() add a good move that produced a beta-cutoff
1852 // among the killer moves of that ply.
1854 void update_killers(Move m, Move killers[]) {
1856 if (m == killers[0])
1859 killers[1] = killers[0];
1864 // update_gains() updates the gains table of a non-capture move given
1865 // the static position evaluation before and after the move.
1867 void update_gains(const Position& pos, Move m, Value before, Value after) {
1870 && before != VALUE_NONE
1871 && after != VALUE_NONE
1872 && pos.captured_piece_type() == PIECE_TYPE_NONE
1873 && !move_is_special(m))
1874 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1878 // init_ss_array() does a fast reset of the first entries of a SearchStack
1879 // array and of all the excludedMove and skipNullMove entries.
1881 void init_ss_array(SearchStack* ss, int size) {
1883 for (int i = 0; i < size; i++, ss++)
1885 ss->excludedMove = MOVE_NONE;
1886 ss->skipNullMove = false;
1887 ss->reduction = DEPTH_ZERO;
1891 ss->killers[0] = ss->killers[1] = ss->mateKiller = MOVE_NONE;
1896 // value_to_uci() converts a value to a string suitable for use with the UCI
1897 // protocol specifications:
1899 // cp <x> The score from the engine's point of view in centipawns.
1900 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1901 // use negative values for y.
1903 std::string value_to_uci(Value v) {
1905 std::stringstream s;
1907 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1908 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1910 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1916 // current_search_time() returns the number of milliseconds which have passed
1917 // since the beginning of the current search.
1919 int current_search_time() {
1921 return get_system_time() - SearchStartTime;
1925 // nps() computes the current nodes/second count
1927 int nps(const Position& pos) {
1929 int t = current_search_time();
1930 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1934 // poll() performs two different functions: It polls for user input, and it
1935 // looks at the time consumed so far and decides if it's time to abort the
1938 void poll(const Position& pos) {
1940 static int lastInfoTime;
1941 int t = current_search_time();
1944 if (input_available())
1946 // We are line oriented, don't read single chars
1947 std::string command;
1949 if (!std::getline(std::cin, command))
1952 if (command == "quit")
1954 // Quit the program as soon as possible
1956 QuitRequest = StopRequest = true;
1959 else if (command == "stop")
1961 // Stop calculating as soon as possible, but still send the "bestmove"
1962 // and possibly the "ponder" token when finishing the search.
1966 else if (command == "ponderhit")
1968 // The opponent has played the expected move. GUI sends "ponderhit" if
1969 // we were told to ponder on the same move the opponent has played. We
1970 // should continue searching but switching from pondering to normal search.
1973 if (StopOnPonderhit)
1978 // Print search information
1982 else if (lastInfoTime > t)
1983 // HACK: Must be a new search where we searched less than
1984 // NodesBetweenPolls nodes during the first second of search.
1987 else if (t - lastInfoTime >= 1000)
1994 if (dbg_show_hit_rate)
1995 dbg_print_hit_rate();
1997 // Send info on searched nodes as soon as we return to root
1998 SendSearchedNodes = true;
2001 // Should we stop the search?
2005 bool stillAtFirstMove = FirstRootMove
2006 && !AspirationFailLow
2007 && t > TimeMgr.available_time();
2009 bool noMoreTime = t > TimeMgr.maximum_time()
2010 || stillAtFirstMove;
2012 if ( (UseTimeManagement && noMoreTime)
2013 || (ExactMaxTime && t >= ExactMaxTime)
2014 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2019 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2020 // while the program is pondering. The point is to work around a wrinkle in
2021 // the UCI protocol: When pondering, the engine is not allowed to give a
2022 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2023 // We simply wait here until one of these commands is sent, and return,
2024 // after which the bestmove and pondermove will be printed.
2026 void wait_for_stop_or_ponderhit() {
2028 std::string command;
2032 // Wait for a command from stdin
2033 if (!std::getline(std::cin, command))
2036 if (command == "quit")
2041 else if (command == "ponderhit" || command == "stop")
2047 // init_thread() is the function which is called when a new thread is
2048 // launched. It simply calls the idle_loop() function with the supplied
2049 // threadID. There are two versions of this function; one for POSIX
2050 // threads and one for Windows threads.
2052 #if !defined(_MSC_VER)
2054 void* init_thread(void* threadID) {
2056 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2062 DWORD WINAPI init_thread(LPVOID threadID) {
2064 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2071 /// The ThreadsManager class
2074 // read_uci_options() updates number of active threads and other internal
2075 // parameters according to the UCI options values. It is called before
2076 // to start a new search.
2078 void ThreadsManager::read_uci_options() {
2080 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2081 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2082 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2083 activeThreads = Options["Threads"].value<int>();
2087 // idle_loop() is where the threads are parked when they have no work to do.
2088 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2089 // object for which the current thread is the master.
2091 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2093 assert(threadID >= 0 && threadID < MAX_THREADS);
2096 bool allFinished = false;
2100 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2101 // master should exit as last one.
2102 if (allThreadsShouldExit)
2105 threads[threadID].state = THREAD_TERMINATED;
2109 // If we are not thinking, wait for a condition to be signaled
2110 // instead of wasting CPU time polling for work.
2111 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2112 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2114 assert(!sp || useSleepingThreads);
2115 assert(threadID != 0 || useSleepingThreads);
2117 if (threads[threadID].state == THREAD_INITIALIZING)
2118 threads[threadID].state = THREAD_AVAILABLE;
2120 // Grab the lock to avoid races with wake_sleeping_thread()
2121 lock_grab(&sleepLock[threadID]);
2123 // If we are master and all slaves have finished do not go to sleep
2124 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2125 allFinished = (i == activeThreads);
2127 if (allFinished || allThreadsShouldExit)
2129 lock_release(&sleepLock[threadID]);
2133 // Do sleep here after retesting sleep conditions
2134 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2135 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2137 lock_release(&sleepLock[threadID]);
2140 // If this thread has been assigned work, launch a search
2141 if (threads[threadID].state == THREAD_WORKISWAITING)
2143 assert(!allThreadsShouldExit);
2145 threads[threadID].state = THREAD_SEARCHING;
2147 // Here we call search() with SplitPoint template parameter set to true
2148 SplitPoint* tsp = threads[threadID].splitPoint;
2149 Position pos(*tsp->pos, threadID);
2150 SearchStack* ss = tsp->sstack[threadID] + 1;
2154 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2156 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2158 assert(threads[threadID].state == THREAD_SEARCHING);
2160 threads[threadID].state = THREAD_AVAILABLE;
2162 // Wake up master thread so to allow it to return from the idle loop in
2163 // case we are the last slave of the split point.
2164 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2165 wake_sleeping_thread(tsp->master);
2168 // If this thread is the master of a split point and all slaves have
2169 // finished their work at this split point, return from the idle loop.
2170 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2171 allFinished = (i == activeThreads);
2175 // Because sp->slaves[] is reset under lock protection,
2176 // be sure sp->lock has been released before to return.
2177 lock_grab(&(sp->lock));
2178 lock_release(&(sp->lock));
2180 // In helpful master concept a master can help only a sub-tree, and
2181 // because here is all finished is not possible master is booked.
2182 assert(threads[threadID].state == THREAD_AVAILABLE);
2184 threads[threadID].state = THREAD_SEARCHING;
2191 // init_threads() is called during startup. It launches all helper threads,
2192 // and initializes the split point stack and the global locks and condition
2195 void ThreadsManager::init_threads() {
2197 int i, arg[MAX_THREADS];
2200 // Initialize global locks
2203 for (i = 0; i < MAX_THREADS; i++)
2205 lock_init(&sleepLock[i]);
2206 cond_init(&sleepCond[i]);
2209 // Initialize splitPoints[] locks
2210 for (i = 0; i < MAX_THREADS; i++)
2211 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2212 lock_init(&(threads[i].splitPoints[j].lock));
2214 // Will be set just before program exits to properly end the threads
2215 allThreadsShouldExit = false;
2217 // Threads will be put all threads to sleep as soon as created
2220 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2221 threads[0].state = THREAD_SEARCHING;
2222 for (i = 1; i < MAX_THREADS; i++)
2223 threads[i].state = THREAD_INITIALIZING;
2225 // Launch the helper threads
2226 for (i = 1; i < MAX_THREADS; i++)
2230 #if !defined(_MSC_VER)
2231 pthread_t pthread[1];
2232 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2233 pthread_detach(pthread[0]);
2235 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2239 cout << "Failed to create thread number " << i << endl;
2243 // Wait until the thread has finished launching and is gone to sleep
2244 while (threads[i].state == THREAD_INITIALIZING) {}
2249 // exit_threads() is called when the program exits. It makes all the
2250 // helper threads exit cleanly.
2252 void ThreadsManager::exit_threads() {
2254 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2256 // Wake up all the threads and waits for termination
2257 for (int i = 1; i < MAX_THREADS; i++)
2259 wake_sleeping_thread(i);
2260 while (threads[i].state != THREAD_TERMINATED) {}
2263 // Now we can safely destroy the locks
2264 for (int i = 0; i < MAX_THREADS; i++)
2265 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2266 lock_destroy(&(threads[i].splitPoints[j].lock));
2268 lock_destroy(&mpLock);
2270 // Now we can safely destroy the wait conditions
2271 for (int i = 0; i < MAX_THREADS; i++)
2273 lock_destroy(&sleepLock[i]);
2274 cond_destroy(&sleepCond[i]);
2279 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2280 // the thread's currently active split point, or in some ancestor of
2281 // the current split point.
2283 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2285 assert(threadID >= 0 && threadID < activeThreads);
2287 SplitPoint* sp = threads[threadID].splitPoint;
2289 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2294 // thread_is_available() checks whether the thread with threadID "slave" is
2295 // available to help the thread with threadID "master" at a split point. An
2296 // obvious requirement is that "slave" must be idle. With more than two
2297 // threads, this is not by itself sufficient: If "slave" is the master of
2298 // some active split point, it is only available as a slave to the other
2299 // threads which are busy searching the split point at the top of "slave"'s
2300 // split point stack (the "helpful master concept" in YBWC terminology).
2302 bool ThreadsManager::thread_is_available(int slave, int master) const {
2304 assert(slave >= 0 && slave < activeThreads);
2305 assert(master >= 0 && master < activeThreads);
2306 assert(activeThreads > 1);
2308 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2311 // Make a local copy to be sure doesn't change under our feet
2312 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2314 // No active split points means that the thread is available as
2315 // a slave for any other thread.
2316 if (localActiveSplitPoints == 0 || activeThreads == 2)
2319 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2320 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2321 // could have been set to 0 by another thread leading to an out of bound access.
2322 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2329 // available_thread_exists() tries to find an idle thread which is available as
2330 // a slave for the thread with threadID "master".
2332 bool ThreadsManager::available_thread_exists(int master) const {
2334 assert(master >= 0 && master < activeThreads);
2335 assert(activeThreads > 1);
2337 for (int i = 0; i < activeThreads; i++)
2338 if (thread_is_available(i, master))
2345 // split() does the actual work of distributing the work at a node between
2346 // several available threads. If it does not succeed in splitting the
2347 // node (because no idle threads are available, or because we have no unused
2348 // split point objects), the function immediately returns. If splitting is
2349 // possible, a SplitPoint object is initialized with all the data that must be
2350 // copied to the helper threads and we tell our helper threads that they have
2351 // been assigned work. This will cause them to instantly leave their idle loops and
2352 // call search().When all threads have returned from search() then split() returns.
2354 template <bool Fake>
2355 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2356 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2357 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2358 assert(pos.is_ok());
2359 assert(ply > 0 && ply < PLY_MAX);
2360 assert(*bestValue >= -VALUE_INFINITE);
2361 assert(*bestValue <= *alpha);
2362 assert(*alpha < beta);
2363 assert(beta <= VALUE_INFINITE);
2364 assert(depth > DEPTH_ZERO);
2365 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2366 assert(activeThreads > 1);
2368 int i, master = pos.thread();
2369 Thread& masterThread = threads[master];
2373 // If no other thread is available to help us, or if we have too many
2374 // active split points, don't split.
2375 if ( !available_thread_exists(master)
2376 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2378 lock_release(&mpLock);
2382 // Pick the next available split point object from the split point stack
2383 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2385 // Initialize the split point object
2386 splitPoint.parent = masterThread.splitPoint;
2387 splitPoint.master = master;
2388 splitPoint.betaCutoff = false;
2389 splitPoint.ply = ply;
2390 splitPoint.depth = depth;
2391 splitPoint.threatMove = threatMove;
2392 splitPoint.mateThreat = mateThreat;
2393 splitPoint.alpha = *alpha;
2394 splitPoint.beta = beta;
2395 splitPoint.pvNode = pvNode;
2396 splitPoint.bestValue = *bestValue;
2398 splitPoint.moveCount = moveCount;
2399 splitPoint.pos = &pos;
2400 splitPoint.nodes = 0;
2401 splitPoint.parentSstack = ss;
2402 for (i = 0; i < activeThreads; i++)
2403 splitPoint.slaves[i] = 0;
2405 masterThread.splitPoint = &splitPoint;
2407 // If we are here it means we are not available
2408 assert(masterThread.state != THREAD_AVAILABLE);
2410 int workersCnt = 1; // At least the master is included
2412 // Allocate available threads setting state to THREAD_BOOKED
2413 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2414 if (thread_is_available(i, master))
2416 threads[i].state = THREAD_BOOKED;
2417 threads[i].splitPoint = &splitPoint;
2418 splitPoint.slaves[i] = 1;
2422 assert(Fake || workersCnt > 1);
2424 // We can release the lock because slave threads are already booked and master is not available
2425 lock_release(&mpLock);
2427 // Tell the threads that they have work to do. This will make them leave
2428 // their idle loop. But before copy search stack tail for each thread.
2429 for (i = 0; i < activeThreads; i++)
2430 if (i == master || splitPoint.slaves[i])
2432 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2434 assert(i == master || threads[i].state == THREAD_BOOKED);
2436 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2438 if (useSleepingThreads && i != master)
2439 wake_sleeping_thread(i);
2442 // Everything is set up. The master thread enters the idle loop, from
2443 // which it will instantly launch a search, because its state is
2444 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2445 // idle loop, which means that the main thread will return from the idle
2446 // loop when all threads have finished their work at this split point.
2447 idle_loop(master, &splitPoint);
2449 // We have returned from the idle loop, which means that all threads are
2450 // finished. Update alpha and bestValue, and return.
2453 *alpha = splitPoint.alpha;
2454 *bestValue = splitPoint.bestValue;
2455 masterThread.activeSplitPoints--;
2456 masterThread.splitPoint = splitPoint.parent;
2457 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2459 lock_release(&mpLock);
2463 // wake_sleeping_thread() wakes up the thread with the given threadID
2464 // when it is time to start a new search.
2466 void ThreadsManager::wake_sleeping_thread(int threadID) {
2468 lock_grab(&sleepLock[threadID]);
2469 cond_signal(&sleepCond[threadID]);
2470 lock_release(&sleepLock[threadID]);
2474 /// RootMove and RootMoveList method's definitions
2476 RootMove::RootMove() {
2479 pv_score = non_pv_score = -VALUE_INFINITE;
2483 RootMove& RootMove::operator=(const RootMove& rm) {
2485 const Move* src = rm.pv;
2488 // Avoid a costly full rm.pv[] copy
2489 do *dst++ = *src; while (*src++ != MOVE_NONE);
2492 pv_score = rm.pv_score;
2493 non_pv_score = rm.non_pv_score;
2497 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2498 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2499 // allow to always have a ponder move even when we fail high at root and also a
2500 // long PV to print that is important for position analysis.
2502 void RootMove::extract_pv_from_tt(Position& pos) {
2504 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2508 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2510 pos.do_move(pv[0], *st++);
2512 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2513 && tte->move() != MOVE_NONE
2514 && move_is_legal(pos, tte->move())
2516 && (!pos.is_draw() || ply < 2))
2518 pv[ply] = tte->move();
2519 pos.do_move(pv[ply++], *st++);
2521 pv[ply] = MOVE_NONE;
2523 do pos.undo_move(pv[--ply]); while (ply);
2526 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2527 // the PV back into the TT. This makes sure the old PV moves are searched
2528 // first, even if the old TT entries have been overwritten.
2530 void RootMove::insert_pv_in_tt(Position& pos) {
2532 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2535 Value v, m = VALUE_NONE;
2538 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2542 tte = TT.retrieve(k);
2544 // Don't overwrite exsisting correct entries
2545 if (!tte || tte->move() != pv[ply])
2547 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2548 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2550 pos.do_move(pv[ply], *st++);
2552 } while (pv[++ply] != MOVE_NONE);
2554 do pos.undo_move(pv[--ply]); while (ply);
2557 // pv_info_to_uci() returns a string with information on the current PV line
2558 // formatted according to UCI specification and eventually writes the info
2559 // to a log file. It is called at each iteration or after a new pv is found.
2561 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2563 std::stringstream s, l;
2566 while (*m != MOVE_NONE)
2569 s << "info depth " << depth / ONE_PLY
2570 << " seldepth " << int(m - pv)
2571 << " multipv " << pvLine + 1
2572 << " score " << value_to_uci(pv_score)
2573 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2574 << " time " << current_search_time()
2575 << " nodes " << pos.nodes_searched()
2576 << " nps " << nps(pos)
2577 << " pv " << l.str();
2579 if (UseLogFile && pvLine == 0)
2581 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2582 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2584 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2590 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2592 SearchStack ss[PLY_MAX_PLUS_2];
2593 MoveStack mlist[MOVES_MAX];
2597 // Initialize search stack
2598 init_ss_array(ss, PLY_MAX_PLUS_2);
2599 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
2600 bestMoveChanges = 0;
2603 // Generate all legal moves
2604 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2606 // Add each move to the RootMoveList's vector
2607 for (MoveStack* cur = mlist; cur != last; cur++)
2609 // If we have a searchMoves[] list then verify cur->move
2610 // is in the list before to add it.
2611 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2613 if (searchMoves[0] && *sm != cur->move)
2616 // Find a quick score for the move and add to the list
2617 pos.do_move(cur->move, st);
2620 rm.pv[0] = ss[0].currentMove = cur->move;
2621 rm.pv[1] = MOVE_NONE;
2622 rm.pv_score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
2625 pos.undo_move(cur->move);