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 // Easy move margin. An easy move candidate must be at least this much
237 // better than the second best move.
238 const Value EasyMoveMargin = Value(0x200);
241 /// Namespace variables
252 // Time managment variables
253 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
254 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
255 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
260 std::ofstream LogFile;
262 // Multi-threads manager object
263 ThreadsManager ThreadsMgr;
265 // Node counters, used only by thread[0] but try to keep in different cache
266 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
267 bool SendSearchedNodes;
269 int NodesBetweenPolls = 30000;
276 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
278 template <NodeType PvNode, bool SpNode, bool Root>
279 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
281 template <NodeType PvNode>
282 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
284 template <NodeType PvNode>
285 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
287 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
288 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
291 template <NodeType PvNode>
292 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous);
294 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
295 bool connected_moves(const Position& pos, Move m1, Move m2);
296 bool value_is_mate(Value value);
297 Value value_to_tt(Value v, int ply);
298 Value value_from_tt(Value v, int ply);
299 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
300 bool connected_threat(const Position& pos, Move m, Move threat);
301 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
302 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
303 void update_killers(Move m, Move killers[]);
304 void update_gains(const Position& pos, Move move, Value before, Value after);
305 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last);
307 int current_search_time();
308 std::string value_to_uci(Value v);
309 int nps(const Position& pos);
310 void poll(const Position& pos);
311 void wait_for_stop_or_ponderhit();
313 #if !defined(_MSC_VER)
314 void* init_thread(void* threadID);
316 DWORD WINAPI init_thread(LPVOID threadID);
320 // MovePickerExt is an extended MovePicker used to choose at compile time
321 // the proper move source according to the type of node.
322 template<bool SpNode, bool Root> struct MovePickerExt;
324 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
325 // before to search them.
326 template<> struct MovePickerExt<false, true> : public MovePicker {
328 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
329 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
331 Value score = VALUE_ZERO;
333 // Score root moves using the standard way used in main search, the moves
334 // are scored according to the order in which are returned by MovePicker.
335 // This is the second order score that is used to compare the moves when
336 // the first order pv scores of both moves are equal.
337 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
338 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
339 if (rm->pv[0] == move)
341 rm->non_pv_score = score--;
349 Move get_next_move() {
356 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
358 int number_of_evasions() const { return (int)Rml.size(); }
360 RootMoveList::iterator rm;
364 // In SpNodes use split point's shared MovePicker object as move source
365 template<> struct MovePickerExt<true, false> : public MovePicker {
367 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
368 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
371 Move get_next_move() { return mp->get_next_move(); }
373 RootMoveList::iterator rm; // Dummy, needed to compile
377 // Default case, create and use a MovePicker object as source
378 template<> struct MovePickerExt<false, false> : public MovePicker {
380 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
381 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
383 RootMoveList::iterator rm; // Dummy, needed to compile
393 /// init_threads(), exit_threads() and nodes_searched() are helpers to
394 /// give accessibility to some TM methods from outside of current file.
396 void init_threads() { ThreadsMgr.init_threads(); }
397 void exit_threads() { ThreadsMgr.exit_threads(); }
400 /// init_search() is called during startup. It initializes various lookup tables
404 int d; // depth (ONE_PLY == 2)
405 int hd; // half depth (ONE_PLY == 1)
408 // Init reductions array
409 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
411 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
412 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
413 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
414 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
417 // Init futility margins array
418 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
419 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
421 // Init futility move count array
422 for (d = 0; d < 32; d++)
423 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
427 /// perft() is our utility to verify move generation is bug free. All the legal
428 /// moves up to given depth are generated and counted and the sum returned.
430 int64_t perft(Position& pos, Depth depth)
432 MoveStack mlist[MOVES_MAX];
437 // Generate all legal moves
438 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
440 // If we are at the last ply we don't need to do and undo
441 // the moves, just to count them.
442 if (depth <= ONE_PLY)
443 return int(last - mlist);
445 // Loop through all legal moves
447 for (MoveStack* cur = mlist; cur != last; cur++)
450 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
451 sum += perft(pos, depth - ONE_PLY);
458 /// think() is the external interface to Stockfish's search, and is called when
459 /// the program receives the UCI 'go' command. It initializes various
460 /// search-related global variables, and calls id_loop(). It returns false
461 /// when a quit command is received during the search.
463 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
464 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
466 // Initialize global search variables
467 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
469 SearchStartTime = get_system_time();
470 ExactMaxTime = maxTime;
473 InfiniteSearch = infinite;
475 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
477 // Look for a book move, only during games, not tests
478 if (UseTimeManagement && Options["OwnBook"].value<bool>())
480 if (Options["Book File"].value<std::string>() != OpeningBook.name())
481 OpeningBook.open(Options["Book File"].value<std::string>());
483 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
484 if (bookMove != MOVE_NONE)
487 wait_for_stop_or_ponderhit();
489 cout << "bestmove " << bookMove << endl;
494 // Read UCI option values
495 TT.set_size(Options["Hash"].value<int>());
496 if (Options["Clear Hash"].value<bool>())
498 Options["Clear Hash"].set_value("false");
502 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
503 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
504 SingleEvasionExtension[1] = Options["Single Evasion Extension (PV nodes)"].value<Depth>();
505 SingleEvasionExtension[0] = Options["Single Evasion Extension (non-PV nodes)"].value<Depth>();
506 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
507 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
508 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
509 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
510 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
511 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
512 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
513 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
514 MultiPV = Options["MultiPV"].value<int>();
515 UseLogFile = Options["Use Search Log"].value<bool>();
517 read_evaluation_uci_options(pos.side_to_move());
519 // Set the number of active threads
520 ThreadsMgr.read_uci_options();
521 init_eval(ThreadsMgr.active_threads());
523 // Wake up needed threads
524 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
525 ThreadsMgr.wake_sleeping_thread(i);
528 int myTime = time[pos.side_to_move()];
529 int myIncrement = increment[pos.side_to_move()];
530 if (UseTimeManagement)
531 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
533 // Set best NodesBetweenPolls interval to avoid lagging under
534 // heavy time pressure.
536 NodesBetweenPolls = Min(MaxNodes, 30000);
537 else if (myTime && myTime < 1000)
538 NodesBetweenPolls = 1000;
539 else if (myTime && myTime < 5000)
540 NodesBetweenPolls = 5000;
542 NodesBetweenPolls = 30000;
544 // Write search information to log file
547 std::string name = Options["Search Log Filename"].value<std::string>();
548 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
550 LogFile << "Searching: " << pos.to_fen()
551 << "\ninfinite: " << infinite
552 << " ponder: " << ponder
553 << " time: " << myTime
554 << " increment: " << myIncrement
555 << " moves to go: " << movesToGo << endl;
558 // We're ready to start thinking. Call the iterative deepening loop function
559 Move ponderMove = MOVE_NONE;
560 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
562 // Print final search statistics
563 cout << "info nodes " << pos.nodes_searched()
564 << " nps " << nps(pos)
565 << " time " << current_search_time() << endl;
569 LogFile << "\nNodes: " << pos.nodes_searched()
570 << "\nNodes/second: " << nps(pos)
571 << "\nBest move: " << move_to_san(pos, bestMove);
574 pos.do_move(bestMove, st);
575 LogFile << "\nPonder move: "
576 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
579 // Return from think() with unchanged position
580 pos.undo_move(bestMove);
585 // This makes all the threads to go to sleep
586 ThreadsMgr.set_active_threads(1);
588 // If we are pondering or in infinite search, we shouldn't print the
589 // best move before we are told to do so.
590 if (!StopRequest && (Pondering || InfiniteSearch))
591 wait_for_stop_or_ponderhit();
593 // Could be both MOVE_NONE when searching on a stalemate position
594 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
602 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
603 // with increasing depth until the allocated thinking time has been consumed,
604 // user stops the search, or the maximum search depth is reached.
606 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
608 SearchStack ss[PLY_MAX_PLUS_2];
609 Value bestValues[PLY_MAX_PLUS_2];
610 int bestMoveChanges[PLY_MAX_PLUS_2];
611 int iteration, researchCountFL, researchCountFH, aspirationDelta;
612 Value value, alpha, beta;
614 Move bestMove, easyMove;
616 // Moves to search are verified, scored and sorted
617 Rml.init(pos, searchMoves);
619 // Initialize FIXME move before Rml.init()
622 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
623 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
624 *ponderMove = bestMove = easyMove = MOVE_NONE;
627 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
629 // Handle special case of searching on a mate/stale position
632 cout << "info depth " << iteration << " score "
633 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
639 // Send initial scoring (iteration 1)
640 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
641 << "info depth " << iteration
642 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
644 // Is one move significantly better than others after initial scoring ?
646 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
647 easyMove = Rml[0].pv[0];
649 // Iterative deepening loop
650 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
652 cout << "info depth " << iteration << endl;
654 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
655 depth = (iteration - 1) * ONE_PLY;
657 // Calculate dynamic aspiration window based on previous iterations
658 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
660 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
661 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
663 aspirationDelta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
664 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
666 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
667 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
670 // Start with a small aspiration window and, in case of fail high/low,
671 // research with bigger window until not failing high/low anymore.
674 // Search starting from ss+1 to allow calling update_gains()
675 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
677 // Write PV lines to transposition table, in case the relevant entries
678 // 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 // Value cannot be trusted. Break out immediately!
686 assert(value >= alpha);
688 // In case of failing high/low increase aspiration window and research,
689 // otherwise exit the fail high/low loop.
692 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
695 else if (value <= alpha)
697 AspirationFailLow = true;
698 StopOnPonderhit = false;
700 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
707 // Collect info about search result
708 bestMove = Rml[0].pv[0];
709 bestValues[iteration] = value;
710 bestMoveChanges[iteration] = Rml.bestMoveChanges;
712 // Drop the easy move if differs from the new best move
713 if (bestMove != easyMove)
714 easyMove = MOVE_NONE;
716 if (UseTimeManagement && !StopRequest)
719 bool noMoreTime = false;
721 // Stop search early when the last two iterations returned a mate score
723 && abs(bestValues[iteration]) >= abs(VALUE_MATE) - 100
724 && abs(bestValues[iteration-1]) >= abs(VALUE_MATE) - 100)
727 // Stop search early if one move seems to be much better than the
728 // others or if there is only a single legal move. In this latter
729 // case we search up to Iteration 8 anyway to get a proper score.
731 && easyMove == bestMove
733 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
734 && current_search_time() > TimeMgr.available_time() / 16)
735 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
736 && current_search_time() > TimeMgr.available_time() / 32)))
739 // Add some extra time if the best move has changed during the last two iterations
740 if (iteration > 5 && iteration <= 50)
741 TimeMgr.pv_instability(bestMoveChanges[iteration], bestMoveChanges[iteration-1]);
743 // Stop search if most of MaxSearchTime is consumed at the end of the
744 // iteration. We probably don't have enough time to search the first
745 // move at the next iteration anyway.
746 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
752 StopOnPonderhit = true;
759 *ponderMove = Rml[0].pv[1];
764 // search<>() is the main search function for both PV and non-PV nodes and for
765 // normal and SplitPoint nodes. When called just after a split point the search
766 // is simpler because we have already probed the hash table, done a null move
767 // search, and searched the first move before splitting, we don't have to repeat
768 // all this work again. We also don't need to store anything to the hash table
769 // here: This is taken care of after we return from the split point.
771 template <NodeType PvNode, bool SpNode, bool Root>
772 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
774 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
775 assert(beta > alpha && beta <= VALUE_INFINITE);
776 assert(PvNode || alpha == beta - 1);
777 assert((Root || ply > 0) && ply < PLY_MAX);
778 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
780 Move movesSearched[MOVES_MAX];
785 Move ttMove, move, excludedMove, threatMove;
788 Value bestValue, value, oldAlpha;
789 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
790 bool isPvMove, isCheck, singleEvasion, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
791 bool mateThreat = false;
792 int moveCount = 0, playedMoveCount = 0;
793 int threadID = pos.thread();
794 SplitPoint* sp = NULL;
796 refinedValue = bestValue = value = -VALUE_INFINITE;
798 isCheck = pos.is_check();
804 ttMove = excludedMove = MOVE_NONE;
805 threatMove = sp->threatMove;
806 mateThreat = sp->mateThreat;
807 goto split_point_start;
812 // Step 1. Initialize node and poll. Polling can abort search
813 ss->currentMove = ss->bestMove = threatMove = MOVE_NONE;
814 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
816 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
822 // Step 2. Check for aborted search and immediate draw
824 || ThreadsMgr.cutoff_at_splitpoint(threadID)
826 || ply >= PLY_MAX - 1) && !Root)
829 // Step 3. Mate distance pruning
830 alpha = Max(value_mated_in(ply), alpha);
831 beta = Min(value_mate_in(ply+1), beta);
835 // Step 4. Transposition table lookup
836 // We don't want the score of a partial search to overwrite a previous full search
837 // TT value, so we use a different position key in case of an excluded move exists.
838 excludedMove = ss->excludedMove;
839 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
841 tte = TT.retrieve(posKey);
842 ttMove = tte ? tte->move() : MOVE_NONE;
844 // At PV nodes, we don't use the TT for pruning, but only for move ordering.
845 // This is to avoid problems in the following areas:
847 // * Repetition draw detection
848 // * Fifty move rule detection
849 // * Searching for a mate
850 // * Printing of full PV line
851 if (!PvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
854 ss->bestMove = ttMove; // Can be MOVE_NONE
855 return value_from_tt(tte->value(), ply);
858 // Step 5. Evaluate the position statically and
859 // update gain statistics of parent move.
861 ss->eval = ss->evalMargin = VALUE_NONE;
864 assert(tte->static_value() != VALUE_NONE);
866 ss->eval = tte->static_value();
867 ss->evalMargin = tte->static_value_margin();
868 refinedValue = refine_eval(tte, ss->eval, ply);
872 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
873 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
876 // Save gain for the parent non-capture move
877 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
879 // Step 6. Razoring (is omitted in PV nodes)
881 && depth < RazorDepth
883 && refinedValue < beta - razor_margin(depth)
884 && ttMove == MOVE_NONE
885 && !value_is_mate(beta)
886 && !pos.has_pawn_on_7th(pos.side_to_move()))
888 Value rbeta = beta - razor_margin(depth);
889 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
891 // Logically we should return (v + razor_margin(depth)), but
892 // surprisingly this did slightly weaker in tests.
896 // Step 7. Static null move pruning (is omitted in PV nodes)
897 // We're betting that the opponent doesn't have a move that will reduce
898 // the score by more than futility_margin(depth) if we do a null move.
901 && depth < RazorDepth
903 && refinedValue >= beta + futility_margin(depth, 0)
904 && !value_is_mate(beta)
905 && pos.non_pawn_material(pos.side_to_move()))
906 return refinedValue - futility_margin(depth, 0);
908 // Step 8. Null move search with verification search (is omitted in PV nodes)
913 && refinedValue >= beta
914 && !value_is_mate(beta)
915 && pos.non_pawn_material(pos.side_to_move()))
917 ss->currentMove = MOVE_NULL;
919 // Null move dynamic reduction based on depth
920 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
922 // Null move dynamic reduction based on value
923 if (refinedValue - beta > PawnValueMidgame)
926 pos.do_null_move(st);
927 (ss+1)->skipNullMove = true;
928 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
929 (ss+1)->skipNullMove = false;
930 pos.undo_null_move();
932 if (nullValue >= beta)
934 // Do not return unproven mate scores
935 if (nullValue >= value_mate_in(PLY_MAX))
938 if (depth < 6 * ONE_PLY)
941 // Do verification search at high depths
942 ss->skipNullMove = true;
943 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
944 ss->skipNullMove = false;
951 // The null move failed low, which means that we may be faced with
952 // some kind of threat. If the previous move was reduced, check if
953 // the move that refuted the null move was somehow connected to the
954 // move which was reduced. If a connection is found, return a fail
955 // low score (which will cause the reduced move to fail high in the
956 // parent node, which will trigger a re-search with full depth).
957 if (nullValue == value_mated_in(ply + 2))
960 threatMove = (ss+1)->bestMove;
961 if ( depth < ThreatDepth
963 && threatMove != MOVE_NONE
964 && connected_moves(pos, (ss-1)->currentMove, threatMove))
969 // Step 9. Internal iterative deepening
970 if ( depth >= IIDDepth[PvNode]
971 && ttMove == MOVE_NONE
972 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
974 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
976 ss->skipNullMove = true;
977 search<PvNode>(pos, ss, alpha, beta, d, ply);
978 ss->skipNullMove = false;
980 ttMove = ss->bestMove;
981 tte = TT.retrieve(posKey);
984 // Expensive mate threat detection (only for PV nodes)
986 mateThreat = pos.has_mate_threat();
988 split_point_start: // At split points actual search starts from here
990 // Initialize a MovePicker object for the current position
991 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
993 ss->bestMove = MOVE_NONE;
994 singleEvasion = !SpNode && isCheck && mp.number_of_evasions() == 1;
995 futilityBase = ss->eval + ss->evalMargin;
996 singularExtensionNode = !Root
998 && depth >= SingularExtensionDepth[PvNode]
1001 && !excludedMove // Do not allow recursive singular extension search
1002 && (tte->type() & VALUE_TYPE_LOWER)
1003 && tte->depth() >= depth - 3 * ONE_PLY;
1006 lock_grab(&(sp->lock));
1007 bestValue = sp->bestValue;
1010 // Step 10. Loop through moves
1011 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1012 while ( bestValue < beta
1013 && (move = mp.get_next_move()) != MOVE_NONE
1014 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1016 assert(move_is_ok(move));
1020 moveCount = ++sp->moveCount;
1021 lock_release(&(sp->lock));
1023 else if (move == excludedMove)
1030 // This is used by time management
1031 FirstRootMove = (moveCount == 1);
1033 // Save the current node count before the move is searched
1034 nodes = pos.nodes_searched();
1036 // If it's time to send nodes info, do it here where we have the
1037 // correct accumulated node counts searched by each thread.
1038 if (SendSearchedNodes)
1040 SendSearchedNodes = false;
1041 cout << "info nodes " << nodes
1042 << " nps " << nps(pos)
1043 << " time " << current_search_time() << endl;
1046 if (current_search_time() >= 1000)
1047 cout << "info currmove " << move
1048 << " currmovenumber " << moveCount << endl;
1051 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1052 moveIsCheck = pos.move_is_check(move, ci);
1053 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1055 // Step 11. Decide the new search depth
1056 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1058 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1059 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1060 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1061 // lower then ttValue minus a margin then we extend ttMove.
1062 if ( singularExtensionNode
1063 && move == tte->move()
1066 Value ttValue = value_from_tt(tte->value(), ply);
1068 if (abs(ttValue) < VALUE_KNOWN_WIN)
1070 Value b = ttValue - SingularExtensionMargin;
1071 ss->excludedMove = move;
1072 ss->skipNullMove = true;
1073 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1074 ss->skipNullMove = false;
1075 ss->excludedMove = MOVE_NONE;
1076 ss->bestMove = MOVE_NONE;
1082 // Update current move (this must be done after singular extension search)
1083 ss->currentMove = move;
1084 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1086 // Step 12. Futility pruning (is omitted in PV nodes)
1088 && !captureOrPromotion
1092 && !move_is_castle(move))
1094 // Move count based pruning
1095 if ( moveCount >= futility_move_count(depth)
1096 && !(threatMove && connected_threat(pos, move, threatMove))
1097 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1100 lock_grab(&(sp->lock));
1105 // Value based pruning
1106 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1107 // but fixing this made program slightly weaker.
1108 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1109 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1110 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1112 if (futilityValueScaled < beta)
1116 lock_grab(&(sp->lock));
1117 if (futilityValueScaled > sp->bestValue)
1118 sp->bestValue = bestValue = futilityValueScaled;
1120 else if (futilityValueScaled > bestValue)
1121 bestValue = futilityValueScaled;
1126 // Prune moves with negative SEE at low depths
1127 if ( predictedDepth < 2 * ONE_PLY
1128 && bestValue > value_mated_in(PLY_MAX)
1129 && pos.see_sign(move) < 0)
1132 lock_grab(&(sp->lock));
1138 // Step 13. Make the move
1139 pos.do_move(move, st, ci, moveIsCheck);
1141 if (!SpNode && !captureOrPromotion)
1142 movesSearched[playedMoveCount++] = move;
1144 // Step extra. pv search (only in PV nodes)
1145 // The first move in list is the expected PV
1148 // Aspiration window is disabled in multi-pv case
1149 if (Root && MultiPV > 1)
1150 alpha = -VALUE_INFINITE;
1152 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1156 // Step 14. Reduced depth search
1157 // If the move fails high will be re-searched at full depth.
1158 bool doFullDepthSearch = true;
1160 if ( depth >= 3 * ONE_PLY
1161 && !captureOrPromotion
1163 && !move_is_castle(move)
1164 && ss->killers[0] != move
1165 && ss->killers[1] != move)
1167 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1168 : reduction<PvNode>(depth, moveCount);
1171 alpha = SpNode ? sp->alpha : alpha;
1172 Depth d = newDepth - ss->reduction;
1173 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1175 doFullDepthSearch = (value > alpha);
1177 ss->reduction = DEPTH_ZERO; // Restore original reduction
1180 // Step 15. Full depth search
1181 if (doFullDepthSearch)
1183 alpha = SpNode ? sp->alpha : alpha;
1184 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1186 // Step extra. pv search (only in PV nodes)
1187 // Search only for possible new PV nodes, if instead value >= beta then
1188 // parent node fails low with value <= alpha and tries another move.
1189 if (PvNode && value > alpha && (Root || value < beta))
1190 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1194 // Step 16. Undo move
1195 pos.undo_move(move);
1197 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1199 // Step 17. Check for new best move
1202 lock_grab(&(sp->lock));
1203 bestValue = sp->bestValue;
1207 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1212 sp->bestValue = value;
1216 if (PvNode && value < beta) // We want always alpha < beta
1224 sp->betaCutoff = true;
1226 if (value == value_mate_in(ply + 1))
1227 ss->mateKiller = move;
1229 ss->bestMove = move;
1232 sp->parentSstack->bestMove = move;
1238 // To avoid to exit with bestValue == -VALUE_INFINITE
1239 if (value > bestValue)
1242 // Finished searching the move. If StopRequest is true, the search
1243 // was aborted because the user interrupted the search or because we
1244 // ran out of time. In this case, the return value of the search cannot
1245 // be trusted, and we break out of the loop without updating the best
1250 // Remember searched nodes counts for this move
1251 mp.rm->nodes += pos.nodes_searched() - nodes;
1253 // Step 17. Check for new best move
1254 if (!isPvMove && value <= alpha)
1255 mp.rm->pv_score = -VALUE_INFINITE;
1258 // PV move or new best move!
1261 ss->bestMove = move;
1262 mp.rm->pv_score = value;
1263 mp.rm->extract_pv_from_tt(pos);
1265 // We record how often the best move has been changed in each
1266 // iteration. This information is used for time managment: When
1267 // the best move changes frequently, we allocate some more time.
1268 if (!isPvMove && MultiPV == 1)
1269 Rml.bestMoveChanges++;
1271 // Inform GUI that PV has changed, in case of multi-pv UCI protocol
1272 // requires we send all the PV lines properly sorted.
1273 Rml.sort_multipv(moveCount);
1275 for (int j = 0; j < Min(MultiPV, (int)Rml.size()); j++)
1276 cout << Rml[j].pv_info_to_uci(pos, depth, alpha, beta, j) << endl;
1278 // Update alpha. In multi-pv we don't use aspiration window, so
1279 // set alpha equal to minimum score among the PV lines.
1281 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1282 else if (value > alpha)
1285 } // PV move or new best move
1288 // Step 18. Check for split
1291 && depth >= ThreadsMgr.min_split_depth()
1292 && ThreadsMgr.active_threads() > 1
1294 && ThreadsMgr.available_thread_exists(threadID)
1296 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1297 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1298 threatMove, mateThreat, moveCount, &mp, PvNode);
1301 // Step 19. Check for mate and stalemate
1302 // All legal moves have been searched and if there are
1303 // no legal moves, it must be mate or stalemate.
1304 // If one move was excluded return fail low score.
1305 if (!SpNode && !moveCount)
1306 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1308 // Step 20. Update tables
1309 // If the search is not aborted, update the transposition table,
1310 // history counters, and killer moves.
1311 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1313 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1314 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1315 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1317 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1319 // Update killers and history only for non capture moves that fails high
1320 if ( bestValue >= beta
1321 && !pos.move_is_capture_or_promotion(move))
1323 update_history(pos, move, depth, movesSearched, playedMoveCount);
1324 update_killers(move, ss->killers);
1330 // Here we have the lock still grabbed
1331 sp->slaves[threadID] = 0;
1332 sp->nodes += pos.nodes_searched();
1333 lock_release(&(sp->lock));
1336 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1341 // qsearch() is the quiescence search function, which is called by the main
1342 // search function when the remaining depth is zero (or, to be more precise,
1343 // less than ONE_PLY).
1345 template <NodeType PvNode>
1346 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1348 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1349 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1350 assert(PvNode || alpha == beta - 1);
1352 assert(ply > 0 && ply < PLY_MAX);
1353 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1357 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1358 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1361 Value oldAlpha = alpha;
1363 ss->bestMove = ss->currentMove = MOVE_NONE;
1365 // Check for an instant draw or maximum ply reached
1366 if (pos.is_draw() || ply >= PLY_MAX - 1)
1369 // Decide whether or not to include checks, this fixes also the type of
1370 // TT entry depth that we are going to use. Note that in qsearch we use
1371 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1372 isCheck = pos.is_check();
1373 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1375 // Transposition table lookup. At PV nodes, we don't use the TT for
1376 // pruning, but only for move ordering.
1377 tte = TT.retrieve(pos.get_key());
1378 ttMove = (tte ? tte->move() : MOVE_NONE);
1380 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1382 ss->bestMove = ttMove; // Can be MOVE_NONE
1383 return value_from_tt(tte->value(), ply);
1386 // Evaluate the position statically
1389 bestValue = futilityBase = -VALUE_INFINITE;
1390 ss->eval = evalMargin = VALUE_NONE;
1391 enoughMaterial = false;
1397 assert(tte->static_value() != VALUE_NONE);
1399 evalMargin = tte->static_value_margin();
1400 ss->eval = bestValue = tte->static_value();
1403 ss->eval = bestValue = evaluate(pos, evalMargin);
1405 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1407 // Stand pat. Return immediately if static value is at least beta
1408 if (bestValue >= beta)
1411 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1416 if (PvNode && bestValue > alpha)
1419 // Futility pruning parameters, not needed when in check
1420 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1421 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1424 // Initialize a MovePicker object for the current position, and prepare
1425 // to search the moves. Because the depth is <= 0 here, only captures,
1426 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1428 MovePicker mp(pos, ttMove, depth, H);
1431 // Loop through the moves until no moves remain or a beta cutoff occurs
1432 while ( alpha < beta
1433 && (move = mp.get_next_move()) != MOVE_NONE)
1435 assert(move_is_ok(move));
1437 moveIsCheck = pos.move_is_check(move, ci);
1445 && !move_is_promotion(move)
1446 && !pos.move_is_passed_pawn_push(move))
1448 futilityValue = futilityBase
1449 + pos.endgame_value_of_piece_on(move_to(move))
1450 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1452 if (futilityValue < alpha)
1454 if (futilityValue > bestValue)
1455 bestValue = futilityValue;
1460 // Detect non-capture evasions that are candidate to be pruned
1461 evasionPrunable = isCheck
1462 && bestValue > value_mated_in(PLY_MAX)
1463 && !pos.move_is_capture(move)
1464 && !pos.can_castle(pos.side_to_move());
1466 // Don't search moves with negative SEE values
1468 && (!isCheck || evasionPrunable)
1470 && !move_is_promotion(move)
1471 && pos.see_sign(move) < 0)
1474 // Don't search useless checks
1479 && !pos.move_is_capture_or_promotion(move)
1480 && ss->eval + PawnValueMidgame / 4 < beta
1481 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1483 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1484 bestValue = ss->eval + PawnValueMidgame / 4;
1489 // Update current move
1490 ss->currentMove = move;
1492 // Make and search the move
1493 pos.do_move(move, st, ci, moveIsCheck);
1494 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1495 pos.undo_move(move);
1497 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1500 if (value > bestValue)
1506 ss->bestMove = move;
1511 // All legal moves have been searched. A special case: If we're in check
1512 // and no legal moves were found, it is checkmate.
1513 if (isCheck && bestValue == -VALUE_INFINITE)
1514 return value_mated_in(ply);
1516 // Update transposition table
1517 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1518 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1520 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1526 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1527 // it is used in RootMoveList to get an initial scoring.
1528 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1530 SearchStack ss[PLY_MAX_PLUS_2];
1533 memset(ss, 0, 4 * sizeof(SearchStack));
1534 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1536 for (MoveStack* cur = mlist; cur != last; cur++)
1538 ss[0].currentMove = cur->move;
1539 pos.do_move(cur->move, st);
1540 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1541 pos.undo_move(cur->move);
1546 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1547 // bestValue is updated only when returning false because in that case move
1550 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1552 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1553 Square from, to, ksq, victimSq;
1556 Value futilityValue, bv = *bestValue;
1558 from = move_from(move);
1560 them = opposite_color(pos.side_to_move());
1561 ksq = pos.king_square(them);
1562 kingAtt = pos.attacks_from<KING>(ksq);
1563 pc = pos.piece_on(from);
1565 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1566 oldAtt = pos.attacks_from(pc, from, occ);
1567 newAtt = pos.attacks_from(pc, to, occ);
1569 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1570 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1572 if (!(b && (b & (b - 1))))
1575 // Rule 2. Queen contact check is very dangerous
1576 if ( type_of_piece(pc) == QUEEN
1577 && bit_is_set(kingAtt, to))
1580 // Rule 3. Creating new double threats with checks
1581 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1585 victimSq = pop_1st_bit(&b);
1586 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1588 // Note that here we generate illegal "double move"!
1589 if ( futilityValue >= beta
1590 && pos.see_sign(make_move(from, victimSq)) >= 0)
1593 if (futilityValue > bv)
1597 // Update bestValue only if check is not dangerous (because we will prune the move)
1603 // connected_moves() tests whether two moves are 'connected' in the sense
1604 // that the first move somehow made the second move possible (for instance
1605 // if the moving piece is the same in both moves). The first move is assumed
1606 // to be the move that was made to reach the current position, while the
1607 // second move is assumed to be a move from the current position.
1609 bool connected_moves(const Position& pos, Move m1, Move m2) {
1611 Square f1, t1, f2, t2;
1614 assert(m1 && move_is_ok(m1));
1615 assert(m2 && move_is_ok(m2));
1617 // Case 1: The moving piece is the same in both moves
1623 // Case 2: The destination square for m2 was vacated by m1
1629 // Case 3: Moving through the vacated square
1630 if ( piece_is_slider(pos.piece_on(f2))
1631 && bit_is_set(squares_between(f2, t2), f1))
1634 // Case 4: The destination square for m2 is defended by the moving piece in m1
1635 p = pos.piece_on(t1);
1636 if (bit_is_set(pos.attacks_from(p, t1), t2))
1639 // Case 5: Discovered check, checking piece is the piece moved in m1
1640 if ( piece_is_slider(p)
1641 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1642 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1644 // discovered_check_candidates() works also if the Position's side to
1645 // move is the opposite of the checking piece.
1646 Color them = opposite_color(pos.side_to_move());
1647 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1649 if (bit_is_set(dcCandidates, f2))
1656 // value_is_mate() checks if the given value is a mate one eventually
1657 // compensated for the ply.
1659 bool value_is_mate(Value value) {
1661 assert(abs(value) <= VALUE_INFINITE);
1663 return value <= value_mated_in(PLY_MAX)
1664 || value >= value_mate_in(PLY_MAX);
1668 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1669 // "plies to mate from the current ply". Non-mate scores are unchanged.
1670 // The function is called before storing a value to the transposition table.
1672 Value value_to_tt(Value v, int ply) {
1674 if (v >= value_mate_in(PLY_MAX))
1677 if (v <= value_mated_in(PLY_MAX))
1684 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1685 // the transposition table to a mate score corrected for the current ply.
1687 Value value_from_tt(Value v, int ply) {
1689 if (v >= value_mate_in(PLY_MAX))
1692 if (v <= value_mated_in(PLY_MAX))
1699 // extension() decides whether a move should be searched with normal depth,
1700 // or with extended depth. Certain classes of moves (checking moves, in
1701 // particular) are searched with bigger depth than ordinary moves and in
1702 // any case are marked as 'dangerous'. Note that also if a move is not
1703 // extended, as example because the corresponding UCI option is set to zero,
1704 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1705 template <NodeType PvNode>
1706 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck,
1707 bool singleEvasion, bool mateThreat, bool* dangerous) {
1709 assert(m != MOVE_NONE);
1711 Depth result = DEPTH_ZERO;
1712 *dangerous = moveIsCheck | singleEvasion | mateThreat;
1716 if (moveIsCheck && pos.see_sign(m) >= 0)
1717 result += CheckExtension[PvNode];
1720 result += SingleEvasionExtension[PvNode];
1723 result += MateThreatExtension[PvNode];
1726 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1728 Color c = pos.side_to_move();
1729 if (relative_rank(c, move_to(m)) == RANK_7)
1731 result += PawnPushTo7thExtension[PvNode];
1734 if (pos.pawn_is_passed(c, move_to(m)))
1736 result += PassedPawnExtension[PvNode];
1741 if ( captureOrPromotion
1742 && pos.type_of_piece_on(move_to(m)) != PAWN
1743 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1744 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1745 && !move_is_promotion(m)
1748 result += PawnEndgameExtension[PvNode];
1753 && captureOrPromotion
1754 && pos.type_of_piece_on(move_to(m)) != PAWN
1755 && pos.see_sign(m) >= 0)
1757 result += ONE_PLY / 2;
1761 return Min(result, ONE_PLY);
1765 // connected_threat() tests whether it is safe to forward prune a move or if
1766 // is somehow coonected to the threat move returned by null search.
1768 bool connected_threat(const Position& pos, Move m, Move threat) {
1770 assert(move_is_ok(m));
1771 assert(threat && move_is_ok(threat));
1772 assert(!pos.move_is_check(m));
1773 assert(!pos.move_is_capture_or_promotion(m));
1774 assert(!pos.move_is_passed_pawn_push(m));
1776 Square mfrom, mto, tfrom, tto;
1778 mfrom = move_from(m);
1780 tfrom = move_from(threat);
1781 tto = move_to(threat);
1783 // Case 1: Don't prune moves which move the threatened piece
1787 // Case 2: If the threatened piece has value less than or equal to the
1788 // value of the threatening piece, don't prune move which defend it.
1789 if ( pos.move_is_capture(threat)
1790 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1791 || pos.type_of_piece_on(tfrom) == KING)
1792 && pos.move_attacks_square(m, tto))
1795 // Case 3: If the moving piece in the threatened move is a slider, don't
1796 // prune safe moves which block its ray.
1797 if ( piece_is_slider(pos.piece_on(tfrom))
1798 && bit_is_set(squares_between(tfrom, tto), mto)
1799 && pos.see_sign(m) >= 0)
1806 // ok_to_use_TT() returns true if a transposition table score
1807 // can be used at a given point in search.
1809 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1811 Value v = value_from_tt(tte->value(), ply);
1813 return ( tte->depth() >= depth
1814 || v >= Max(value_mate_in(PLY_MAX), beta)
1815 || v < Min(value_mated_in(PLY_MAX), beta))
1817 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1818 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1822 // refine_eval() returns the transposition table score if
1823 // possible otherwise falls back on static position evaluation.
1825 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1829 Value v = value_from_tt(tte->value(), ply);
1831 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1832 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1839 // update_history() registers a good move that produced a beta-cutoff
1840 // in history and marks as failures all the other moves of that ply.
1842 void update_history(const Position& pos, Move move, Depth depth,
1843 Move movesSearched[], int moveCount) {
1845 Value bonus = Value(int(depth) * int(depth));
1847 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1849 for (int i = 0; i < moveCount - 1; i++)
1851 m = movesSearched[i];
1855 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1860 // update_killers() add a good move that produced a beta-cutoff
1861 // among the killer moves of that ply.
1863 void update_killers(Move m, Move killers[]) {
1865 if (m != killers[0])
1867 killers[1] = killers[0];
1873 // update_gains() updates the gains table of a non-capture move given
1874 // the static position evaluation before and after the move.
1876 void update_gains(const Position& pos, Move m, Value before, Value after) {
1879 && before != VALUE_NONE
1880 && after != VALUE_NONE
1881 && pos.captured_piece_type() == PIECE_TYPE_NONE
1882 && !move_is_special(m))
1883 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1887 // value_to_uci() converts a value to a string suitable for use with the UCI
1888 // protocol specifications:
1890 // cp <x> The score from the engine's point of view in centipawns.
1891 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1892 // use negative values for y.
1894 std::string value_to_uci(Value v) {
1896 std::stringstream s;
1898 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1899 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1901 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1907 // current_search_time() returns the number of milliseconds which have passed
1908 // since the beginning of the current search.
1910 int current_search_time() {
1912 return get_system_time() - SearchStartTime;
1916 // nps() computes the current nodes/second count
1918 int nps(const Position& pos) {
1920 int t = current_search_time();
1921 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1925 // poll() performs two different functions: It polls for user input, and it
1926 // looks at the time consumed so far and decides if it's time to abort the
1929 void poll(const Position& pos) {
1931 static int lastInfoTime;
1932 int t = current_search_time();
1935 if (input_available())
1937 // We are line oriented, don't read single chars
1938 std::string command;
1940 if (!std::getline(std::cin, command))
1943 if (command == "quit")
1945 // Quit the program as soon as possible
1947 QuitRequest = StopRequest = true;
1950 else if (command == "stop")
1952 // Stop calculating as soon as possible, but still send the "bestmove"
1953 // and possibly the "ponder" token when finishing the search.
1957 else if (command == "ponderhit")
1959 // The opponent has played the expected move. GUI sends "ponderhit" if
1960 // we were told to ponder on the same move the opponent has played. We
1961 // should continue searching but switching from pondering to normal search.
1964 if (StopOnPonderhit)
1969 // Print search information
1973 else if (lastInfoTime > t)
1974 // HACK: Must be a new search where we searched less than
1975 // NodesBetweenPolls nodes during the first second of search.
1978 else if (t - lastInfoTime >= 1000)
1985 if (dbg_show_hit_rate)
1986 dbg_print_hit_rate();
1988 // Send info on searched nodes as soon as we return to root
1989 SendSearchedNodes = true;
1992 // Should we stop the search?
1996 bool stillAtFirstMove = FirstRootMove
1997 && !AspirationFailLow
1998 && t > TimeMgr.available_time();
2000 bool noMoreTime = t > TimeMgr.maximum_time()
2001 || stillAtFirstMove;
2003 if ( (UseTimeManagement && noMoreTime)
2004 || (ExactMaxTime && t >= ExactMaxTime)
2005 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2010 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2011 // while the program is pondering. The point is to work around a wrinkle in
2012 // the UCI protocol: When pondering, the engine is not allowed to give a
2013 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2014 // We simply wait here until one of these commands is sent, and return,
2015 // after which the bestmove and pondermove will be printed.
2017 void wait_for_stop_or_ponderhit() {
2019 std::string command;
2023 // Wait for a command from stdin
2024 if (!std::getline(std::cin, command))
2027 if (command == "quit")
2032 else if (command == "ponderhit" || command == "stop")
2038 // init_thread() is the function which is called when a new thread is
2039 // launched. It simply calls the idle_loop() function with the supplied
2040 // threadID. There are two versions of this function; one for POSIX
2041 // threads and one for Windows threads.
2043 #if !defined(_MSC_VER)
2045 void* init_thread(void* threadID) {
2047 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2053 DWORD WINAPI init_thread(LPVOID threadID) {
2055 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2062 /// The ThreadsManager class
2065 // read_uci_options() updates number of active threads and other internal
2066 // parameters according to the UCI options values. It is called before
2067 // to start a new search.
2069 void ThreadsManager::read_uci_options() {
2071 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2072 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2073 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2074 activeThreads = Options["Threads"].value<int>();
2078 // idle_loop() is where the threads are parked when they have no work to do.
2079 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2080 // object for which the current thread is the master.
2082 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2084 assert(threadID >= 0 && threadID < MAX_THREADS);
2087 bool allFinished = false;
2091 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2092 // master should exit as last one.
2093 if (allThreadsShouldExit)
2096 threads[threadID].state = THREAD_TERMINATED;
2100 // If we are not thinking, wait for a condition to be signaled
2101 // instead of wasting CPU time polling for work.
2102 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2103 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2105 assert(!sp || useSleepingThreads);
2106 assert(threadID != 0 || useSleepingThreads);
2108 if (threads[threadID].state == THREAD_INITIALIZING)
2109 threads[threadID].state = THREAD_AVAILABLE;
2111 // Grab the lock to avoid races with wake_sleeping_thread()
2112 lock_grab(&sleepLock[threadID]);
2114 // If we are master and all slaves have finished do not go to sleep
2115 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2116 allFinished = (i == activeThreads);
2118 if (allFinished || allThreadsShouldExit)
2120 lock_release(&sleepLock[threadID]);
2124 // Do sleep here after retesting sleep conditions
2125 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2126 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2128 lock_release(&sleepLock[threadID]);
2131 // If this thread has been assigned work, launch a search
2132 if (threads[threadID].state == THREAD_WORKISWAITING)
2134 assert(!allThreadsShouldExit);
2136 threads[threadID].state = THREAD_SEARCHING;
2138 // Here we call search() with SplitPoint template parameter set to true
2139 SplitPoint* tsp = threads[threadID].splitPoint;
2140 Position pos(*tsp->pos, threadID);
2141 SearchStack* ss = tsp->sstack[threadID] + 1;
2145 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2147 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2149 assert(threads[threadID].state == THREAD_SEARCHING);
2151 threads[threadID].state = THREAD_AVAILABLE;
2153 // Wake up master thread so to allow it to return from the idle loop in
2154 // case we are the last slave of the split point.
2155 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2156 wake_sleeping_thread(tsp->master);
2159 // If this thread is the master of a split point and all slaves have
2160 // finished their work at this split point, return from the idle loop.
2161 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2162 allFinished = (i == activeThreads);
2166 // Because sp->slaves[] is reset under lock protection,
2167 // be sure sp->lock has been released before to return.
2168 lock_grab(&(sp->lock));
2169 lock_release(&(sp->lock));
2171 // In helpful master concept a master can help only a sub-tree, and
2172 // because here is all finished is not possible master is booked.
2173 assert(threads[threadID].state == THREAD_AVAILABLE);
2175 threads[threadID].state = THREAD_SEARCHING;
2182 // init_threads() is called during startup. It launches all helper threads,
2183 // and initializes the split point stack and the global locks and condition
2186 void ThreadsManager::init_threads() {
2188 int i, arg[MAX_THREADS];
2191 // Initialize global locks
2194 for (i = 0; i < MAX_THREADS; i++)
2196 lock_init(&sleepLock[i]);
2197 cond_init(&sleepCond[i]);
2200 // Initialize splitPoints[] locks
2201 for (i = 0; i < MAX_THREADS; i++)
2202 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2203 lock_init(&(threads[i].splitPoints[j].lock));
2205 // Will be set just before program exits to properly end the threads
2206 allThreadsShouldExit = false;
2208 // Threads will be put all threads to sleep as soon as created
2211 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2212 threads[0].state = THREAD_SEARCHING;
2213 for (i = 1; i < MAX_THREADS; i++)
2214 threads[i].state = THREAD_INITIALIZING;
2216 // Launch the helper threads
2217 for (i = 1; i < MAX_THREADS; i++)
2221 #if !defined(_MSC_VER)
2222 pthread_t pthread[1];
2223 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2224 pthread_detach(pthread[0]);
2226 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2230 cout << "Failed to create thread number " << i << endl;
2234 // Wait until the thread has finished launching and is gone to sleep
2235 while (threads[i].state == THREAD_INITIALIZING) {}
2240 // exit_threads() is called when the program exits. It makes all the
2241 // helper threads exit cleanly.
2243 void ThreadsManager::exit_threads() {
2245 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2247 // Wake up all the threads and waits for termination
2248 for (int i = 1; i < MAX_THREADS; i++)
2250 wake_sleeping_thread(i);
2251 while (threads[i].state != THREAD_TERMINATED) {}
2254 // Now we can safely destroy the locks
2255 for (int i = 0; i < MAX_THREADS; i++)
2256 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2257 lock_destroy(&(threads[i].splitPoints[j].lock));
2259 lock_destroy(&mpLock);
2261 // Now we can safely destroy the wait conditions
2262 for (int i = 0; i < MAX_THREADS; i++)
2264 lock_destroy(&sleepLock[i]);
2265 cond_destroy(&sleepCond[i]);
2270 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2271 // the thread's currently active split point, or in some ancestor of
2272 // the current split point.
2274 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2276 assert(threadID >= 0 && threadID < activeThreads);
2278 SplitPoint* sp = threads[threadID].splitPoint;
2280 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2285 // thread_is_available() checks whether the thread with threadID "slave" is
2286 // available to help the thread with threadID "master" at a split point. An
2287 // obvious requirement is that "slave" must be idle. With more than two
2288 // threads, this is not by itself sufficient: If "slave" is the master of
2289 // some active split point, it is only available as a slave to the other
2290 // threads which are busy searching the split point at the top of "slave"'s
2291 // split point stack (the "helpful master concept" in YBWC terminology).
2293 bool ThreadsManager::thread_is_available(int slave, int master) const {
2295 assert(slave >= 0 && slave < activeThreads);
2296 assert(master >= 0 && master < activeThreads);
2297 assert(activeThreads > 1);
2299 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2302 // Make a local copy to be sure doesn't change under our feet
2303 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2305 // No active split points means that the thread is available as
2306 // a slave for any other thread.
2307 if (localActiveSplitPoints == 0 || activeThreads == 2)
2310 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2311 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2312 // could have been set to 0 by another thread leading to an out of bound access.
2313 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2320 // available_thread_exists() tries to find an idle thread which is available as
2321 // a slave for the thread with threadID "master".
2323 bool ThreadsManager::available_thread_exists(int master) const {
2325 assert(master >= 0 && master < activeThreads);
2326 assert(activeThreads > 1);
2328 for (int i = 0; i < activeThreads; i++)
2329 if (thread_is_available(i, master))
2336 // split() does the actual work of distributing the work at a node between
2337 // several available threads. If it does not succeed in splitting the
2338 // node (because no idle threads are available, or because we have no unused
2339 // split point objects), the function immediately returns. If splitting is
2340 // possible, a SplitPoint object is initialized with all the data that must be
2341 // copied to the helper threads and we tell our helper threads that they have
2342 // been assigned work. This will cause them to instantly leave their idle loops and
2343 // call search().When all threads have returned from search() then split() returns.
2345 template <bool Fake>
2346 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2347 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2348 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2349 assert(pos.is_ok());
2350 assert(ply > 0 && ply < PLY_MAX);
2351 assert(*bestValue >= -VALUE_INFINITE);
2352 assert(*bestValue <= *alpha);
2353 assert(*alpha < beta);
2354 assert(beta <= VALUE_INFINITE);
2355 assert(depth > DEPTH_ZERO);
2356 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2357 assert(activeThreads > 1);
2359 int i, master = pos.thread();
2360 Thread& masterThread = threads[master];
2364 // If no other thread is available to help us, or if we have too many
2365 // active split points, don't split.
2366 if ( !available_thread_exists(master)
2367 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2369 lock_release(&mpLock);
2373 // Pick the next available split point object from the split point stack
2374 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2376 // Initialize the split point object
2377 splitPoint.parent = masterThread.splitPoint;
2378 splitPoint.master = master;
2379 splitPoint.betaCutoff = false;
2380 splitPoint.ply = ply;
2381 splitPoint.depth = depth;
2382 splitPoint.threatMove = threatMove;
2383 splitPoint.mateThreat = mateThreat;
2384 splitPoint.alpha = *alpha;
2385 splitPoint.beta = beta;
2386 splitPoint.pvNode = pvNode;
2387 splitPoint.bestValue = *bestValue;
2389 splitPoint.moveCount = moveCount;
2390 splitPoint.pos = &pos;
2391 splitPoint.nodes = 0;
2392 splitPoint.parentSstack = ss;
2393 for (i = 0; i < activeThreads; i++)
2394 splitPoint.slaves[i] = 0;
2396 masterThread.splitPoint = &splitPoint;
2398 // If we are here it means we are not available
2399 assert(masterThread.state != THREAD_AVAILABLE);
2401 int workersCnt = 1; // At least the master is included
2403 // Allocate available threads setting state to THREAD_BOOKED
2404 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2405 if (thread_is_available(i, master))
2407 threads[i].state = THREAD_BOOKED;
2408 threads[i].splitPoint = &splitPoint;
2409 splitPoint.slaves[i] = 1;
2413 assert(Fake || workersCnt > 1);
2415 // We can release the lock because slave threads are already booked and master is not available
2416 lock_release(&mpLock);
2418 // Tell the threads that they have work to do. This will make them leave
2419 // their idle loop. But before copy search stack tail for each thread.
2420 for (i = 0; i < activeThreads; i++)
2421 if (i == master || splitPoint.slaves[i])
2423 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2425 assert(i == master || threads[i].state == THREAD_BOOKED);
2427 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2429 if (useSleepingThreads && i != master)
2430 wake_sleeping_thread(i);
2433 // Everything is set up. The master thread enters the idle loop, from
2434 // which it will instantly launch a search, because its state is
2435 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2436 // idle loop, which means that the main thread will return from the idle
2437 // loop when all threads have finished their work at this split point.
2438 idle_loop(master, &splitPoint);
2440 // We have returned from the idle loop, which means that all threads are
2441 // finished. Update alpha and bestValue, and return.
2444 *alpha = splitPoint.alpha;
2445 *bestValue = splitPoint.bestValue;
2446 masterThread.activeSplitPoints--;
2447 masterThread.splitPoint = splitPoint.parent;
2448 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2450 lock_release(&mpLock);
2454 // wake_sleeping_thread() wakes up the thread with the given threadID
2455 // when it is time to start a new search.
2457 void ThreadsManager::wake_sleeping_thread(int threadID) {
2459 lock_grab(&sleepLock[threadID]);
2460 cond_signal(&sleepCond[threadID]);
2461 lock_release(&sleepLock[threadID]);
2465 /// RootMove and RootMoveList method's definitions
2467 RootMove::RootMove() {
2470 pv_score = non_pv_score = -VALUE_INFINITE;
2474 RootMove& RootMove::operator=(const RootMove& rm) {
2476 const Move* src = rm.pv;
2479 // Avoid a costly full rm.pv[] copy
2480 do *dst++ = *src; while (*src++ != MOVE_NONE);
2483 pv_score = rm.pv_score;
2484 non_pv_score = rm.non_pv_score;
2488 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2489 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2490 // allow to always have a ponder move even when we fail high at root and also a
2491 // long PV to print that is important for position analysis.
2493 void RootMove::extract_pv_from_tt(Position& pos) {
2495 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2499 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2501 pos.do_move(pv[0], *st++);
2503 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2504 && tte->move() != MOVE_NONE
2505 && move_is_legal(pos, tte->move())
2507 && (!pos.is_draw() || ply < 2))
2509 pv[ply] = tte->move();
2510 pos.do_move(pv[ply++], *st++);
2512 pv[ply] = MOVE_NONE;
2514 do pos.undo_move(pv[--ply]); while (ply);
2517 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2518 // the PV back into the TT. This makes sure the old PV moves are searched
2519 // first, even if the old TT entries have been overwritten.
2521 void RootMove::insert_pv_in_tt(Position& pos) {
2523 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2526 Value v, m = VALUE_NONE;
2529 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2533 tte = TT.retrieve(k);
2535 // Don't overwrite exsisting correct entries
2536 if (!tte || tte->move() != pv[ply])
2538 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2539 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2541 pos.do_move(pv[ply], *st++);
2543 } while (pv[++ply] != MOVE_NONE);
2545 do pos.undo_move(pv[--ply]); while (ply);
2548 // pv_info_to_uci() returns a string with information on the current PV line
2549 // formatted according to UCI specification and eventually writes the info
2550 // to a log file. It is called at each iteration or after a new pv is found.
2552 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2554 std::stringstream s, l;
2557 while (*m != MOVE_NONE)
2560 s << "info depth " << depth / ONE_PLY
2561 << " seldepth " << int(m - pv)
2562 << " multipv " << pvLine + 1
2563 << " score " << value_to_uci(pv_score)
2564 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2565 << " time " << current_search_time()
2566 << " nodes " << pos.nodes_searched()
2567 << " nps " << nps(pos)
2568 << " pv " << l.str();
2570 if (UseLogFile && pvLine == 0)
2572 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2573 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2575 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2581 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2583 MoveStack mlist[MOVES_MAX];
2587 bestMoveChanges = 0;
2589 // Generate all legal moves and score them
2590 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2591 qsearch_scoring(pos, mlist, last);
2593 // Add each move to the RootMoveList's vector
2594 for (MoveStack* cur = mlist; cur != last; cur++)
2596 // If we have a searchMoves[] list then verify cur->move
2597 // is in the list before to add it.
2598 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2600 if (searchMoves[0] && *sm != cur->move)
2604 rm.pv[0] = cur->move;
2605 rm.pv[1] = MOVE_NONE;
2606 rm.pv_score = Value(cur->score);