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], PawnPushTo7thExtension[2], PassedPawnExtension[2];
207 Depth 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 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;
359 RootMoveList::iterator rm;
363 // In SpNodes use split point's shared MovePicker object as move source
364 template<> struct MovePickerExt<true, false> : public MovePicker {
366 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
367 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
370 Move get_next_move() { return mp->get_next_move(); }
372 RootMoveList::iterator rm; // Dummy, needed to compile
376 // Default case, create and use a MovePicker object as source
377 template<> struct MovePickerExt<false, false> : public MovePicker {
379 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
380 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
382 RootMoveList::iterator rm; // Dummy, needed to compile
392 /// init_threads(), exit_threads() and nodes_searched() are helpers to
393 /// give accessibility to some TM methods from outside of current file.
395 void init_threads() { ThreadsMgr.init_threads(); }
396 void exit_threads() { ThreadsMgr.exit_threads(); }
399 /// init_search() is called during startup. It initializes various lookup tables
403 int d; // depth (ONE_PLY == 2)
404 int hd; // half depth (ONE_PLY == 1)
407 // Init reductions array
408 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
410 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
411 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
412 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
413 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
416 // Init futility margins array
417 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
418 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
420 // Init futility move count array
421 for (d = 0; d < 32; d++)
422 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
426 /// perft() is our utility to verify move generation is bug free. All the legal
427 /// moves up to given depth are generated and counted and the sum returned.
429 int64_t perft(Position& pos, Depth depth)
431 MoveStack mlist[MOVES_MAX];
436 // Generate all legal moves
437 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
439 // If we are at the last ply we don't need to do and undo
440 // the moves, just to count them.
441 if (depth <= ONE_PLY)
442 return int(last - mlist);
444 // Loop through all legal moves
446 for (MoveStack* cur = mlist; cur != last; cur++)
449 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
450 sum += perft(pos, depth - ONE_PLY);
457 /// think() is the external interface to Stockfish's search, and is called when
458 /// the program receives the UCI 'go' command. It initializes various
459 /// search-related global variables, and calls id_loop(). It returns false
460 /// when a quit command is received during the search.
462 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
463 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
465 // Initialize global search variables
466 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
468 SearchStartTime = get_system_time();
469 ExactMaxTime = maxTime;
472 InfiniteSearch = infinite;
474 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
476 // Look for a book move, only during games, not tests
477 if (UseTimeManagement && Options["OwnBook"].value<bool>())
479 if (Options["Book File"].value<std::string>() != OpeningBook.name())
480 OpeningBook.open(Options["Book File"].value<std::string>());
482 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
483 if (bookMove != MOVE_NONE)
486 wait_for_stop_or_ponderhit();
488 cout << "bestmove " << bookMove << endl;
493 // Read UCI option values
494 TT.set_size(Options["Hash"].value<int>());
495 if (Options["Clear Hash"].value<bool>())
497 Options["Clear Hash"].set_value("false");
501 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
502 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
503 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
504 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
505 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
506 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
507 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
508 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
509 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
510 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
511 MultiPV = Options["MultiPV"].value<int>();
512 UseLogFile = Options["Use Search Log"].value<bool>();
514 read_evaluation_uci_options(pos.side_to_move());
516 // Set the number of active threads
517 ThreadsMgr.read_uci_options();
518 init_eval(ThreadsMgr.active_threads());
520 // Wake up needed threads
521 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
522 ThreadsMgr.wake_sleeping_thread(i);
525 int myTime = time[pos.side_to_move()];
526 int myIncrement = increment[pos.side_to_move()];
527 if (UseTimeManagement)
528 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
530 // Set best NodesBetweenPolls interval to avoid lagging under
531 // heavy time pressure.
533 NodesBetweenPolls = Min(MaxNodes, 30000);
534 else if (myTime && myTime < 1000)
535 NodesBetweenPolls = 1000;
536 else if (myTime && myTime < 5000)
537 NodesBetweenPolls = 5000;
539 NodesBetweenPolls = 30000;
541 // Write search information to log file
544 std::string name = Options["Search Log Filename"].value<std::string>();
545 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
547 LogFile << "Searching: " << pos.to_fen()
548 << "\ninfinite: " << infinite
549 << " ponder: " << ponder
550 << " time: " << myTime
551 << " increment: " << myIncrement
552 << " moves to go: " << movesToGo << endl;
555 // We're ready to start thinking. Call the iterative deepening loop function
556 Move ponderMove = MOVE_NONE;
557 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
559 // Print final search statistics
560 cout << "info nodes " << pos.nodes_searched()
561 << " nps " << nps(pos)
562 << " time " << current_search_time() << endl;
566 LogFile << "\nNodes: " << pos.nodes_searched()
567 << "\nNodes/second: " << nps(pos)
568 << "\nBest move: " << move_to_san(pos, bestMove);
571 pos.do_move(bestMove, st);
572 LogFile << "\nPonder move: "
573 << move_to_san(pos, ponderMove) // Works also with MOVE_NONE
576 // Return from think() with unchanged position
577 pos.undo_move(bestMove);
582 // This makes all the threads to go to sleep
583 ThreadsMgr.set_active_threads(1);
585 // If we are pondering or in infinite search, we shouldn't print the
586 // best move before we are told to do so.
587 if (!StopRequest && (Pondering || InfiniteSearch))
588 wait_for_stop_or_ponderhit();
590 // Could be both MOVE_NONE when searching on a stalemate position
591 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
599 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
600 // with increasing depth until the allocated thinking time has been consumed,
601 // user stops the search, or the maximum search depth is reached.
603 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
605 SearchStack ss[PLY_MAX_PLUS_2];
606 Value bestValues[PLY_MAX_PLUS_2];
607 int bestMoveChanges[PLY_MAX_PLUS_2];
608 int iteration, researchCountFL, researchCountFH, aspirationDelta;
609 Value value, alpha, beta;
611 Move bestMove, easyMove;
613 // Moves to search are verified, scored and sorted
614 Rml.init(pos, searchMoves);
616 // Initialize FIXME move before Rml.init()
619 memset(ss, 0, PLY_MAX_PLUS_2 * sizeof(SearchStack));
620 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
621 *ponderMove = bestMove = easyMove = MOVE_NONE;
624 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
626 // Handle special case of searching on a mate/stale position
629 cout << "info depth " << iteration << " score "
630 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
636 // Send initial scoring (iteration 1)
637 cout << set960(pos.is_chess960()) // Is enough to set once at the beginning
638 << "info depth " << iteration
639 << "\n" << Rml[0].pv_info_to_uci(pos, ONE_PLY, alpha, beta) << endl;
641 // Is one move significantly better than others after initial scoring ?
643 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin)
644 easyMove = Rml[0].pv[0];
646 // Iterative deepening loop
647 while (++iteration <= PLY_MAX && (!MaxDepth || iteration <= MaxDepth) && !StopRequest)
649 cout << "info depth " << iteration << endl;
651 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
652 depth = (iteration - 1) * ONE_PLY;
654 // Calculate dynamic aspiration window based on previous iterations
655 if (MultiPV == 1 && iteration >= 6 && abs(bestValues[iteration - 1]) < VALUE_KNOWN_WIN)
657 int prevDelta1 = bestValues[iteration - 1] - bestValues[iteration - 2];
658 int prevDelta2 = bestValues[iteration - 2] - bestValues[iteration - 3];
660 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
661 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
663 alpha = Max(bestValues[iteration - 1] - aspirationDelta, -VALUE_INFINITE);
664 beta = Min(bestValues[iteration - 1] + aspirationDelta, VALUE_INFINITE);
667 // Start with a small aspiration window and, in case of fail high/low,
668 // research with bigger window until not failing high/low anymore.
671 // Search starting from ss+1 to allow calling update_gains()
672 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth, 0);
674 // Send PV line to GUI and write to transposition table in case the
675 // relevant entries have been overwritten during the search.
676 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
678 cout << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
679 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, 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 check for exact scores, while at non-PV nodes we check for
845 // and return a fail high/low. Biggest advantage at probing at PV nodes is
846 // to have a smooth experience in analysis mode.
849 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
850 : ok_to_use_TT(tte, depth, beta, ply)))
853 ss->bestMove = ttMove; // Can be MOVE_NONE
854 return value_from_tt(tte->value(), ply);
857 // Step 5. Evaluate the position statically and
858 // update gain statistics of parent move.
860 ss->eval = ss->evalMargin = VALUE_NONE;
863 assert(tte->static_value() != VALUE_NONE);
865 ss->eval = tte->static_value();
866 ss->evalMargin = tte->static_value_margin();
867 refinedValue = refine_eval(tte, ss->eval, ply);
871 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
872 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
875 // Save gain for the parent non-capture move
876 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
878 // Step 6. Razoring (is omitted in PV nodes)
880 && depth < RazorDepth
882 && refinedValue < beta - razor_margin(depth)
883 && ttMove == MOVE_NONE
884 && !value_is_mate(beta)
885 && !pos.has_pawn_on_7th(pos.side_to_move()))
887 Value rbeta = beta - razor_margin(depth);
888 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
890 // Logically we should return (v + razor_margin(depth)), but
891 // surprisingly this did slightly weaker in tests.
895 // Step 7. Static null move pruning (is omitted in PV nodes)
896 // We're betting that the opponent doesn't have a move that will reduce
897 // the score by more than futility_margin(depth) if we do a null move.
900 && depth < RazorDepth
902 && refinedValue >= beta + futility_margin(depth, 0)
903 && !value_is_mate(beta)
904 && pos.non_pawn_material(pos.side_to_move()))
905 return refinedValue - futility_margin(depth, 0);
907 // Step 8. Null move search with verification search (is omitted in PV nodes)
912 && refinedValue >= beta
913 && !value_is_mate(beta)
914 && pos.non_pawn_material(pos.side_to_move()))
916 ss->currentMove = MOVE_NULL;
918 // Null move dynamic reduction based on depth
919 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
921 // Null move dynamic reduction based on value
922 if (refinedValue - beta > PawnValueMidgame)
925 pos.do_null_move(st);
926 (ss+1)->skipNullMove = true;
927 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
928 (ss+1)->skipNullMove = false;
929 pos.undo_null_move();
931 if (nullValue >= beta)
933 // Do not return unproven mate scores
934 if (nullValue >= value_mate_in(PLY_MAX))
937 if (depth < 6 * ONE_PLY)
940 // Do verification search at high depths
941 ss->skipNullMove = true;
942 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
943 ss->skipNullMove = false;
950 // The null move failed low, which means that we may be faced with
951 // some kind of threat. If the previous move was reduced, check if
952 // the move that refuted the null move was somehow connected to the
953 // move which was reduced. If a connection is found, return a fail
954 // low score (which will cause the reduced move to fail high in the
955 // parent node, which will trigger a re-search with full depth).
956 if (nullValue == value_mated_in(ply + 2))
959 threatMove = (ss+1)->bestMove;
960 if ( depth < ThreatDepth
962 && threatMove != MOVE_NONE
963 && connected_moves(pos, (ss-1)->currentMove, threatMove))
968 // Step 9. Internal iterative deepening
969 if ( depth >= IIDDepth[PvNode]
970 && ttMove == MOVE_NONE
971 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
973 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
975 ss->skipNullMove = true;
976 search<PvNode>(pos, ss, alpha, beta, d, ply);
977 ss->skipNullMove = false;
979 ttMove = ss->bestMove;
980 tte = TT.retrieve(posKey);
983 // Expensive mate threat detection (only for PV nodes)
985 mateThreat = pos.has_mate_threat();
987 split_point_start: // At split points actual search starts from here
989 // Initialize a MovePicker object for the current position
990 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
992 ss->bestMove = MOVE_NONE;
993 futilityBase = ss->eval + ss->evalMargin;
994 singularExtensionNode = !Root
996 && depth >= SingularExtensionDepth[PvNode]
999 && !excludedMove // Do not allow recursive singular extension search
1000 && (tte->type() & VALUE_TYPE_LOWER)
1001 && tte->depth() >= depth - 3 * ONE_PLY;
1004 lock_grab(&(sp->lock));
1005 bestValue = sp->bestValue;
1008 // Step 10. Loop through moves
1009 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1010 while ( bestValue < beta
1011 && (move = mp.get_next_move()) != MOVE_NONE
1012 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1014 assert(move_is_ok(move));
1018 moveCount = ++sp->moveCount;
1019 lock_release(&(sp->lock));
1021 else if (move == excludedMove)
1028 // This is used by time management
1029 FirstRootMove = (moveCount == 1);
1031 // Save the current node count before the move is searched
1032 nodes = pos.nodes_searched();
1034 // If it's time to send nodes info, do it here where we have the
1035 // correct accumulated node counts searched by each thread.
1036 if (SendSearchedNodes)
1038 SendSearchedNodes = false;
1039 cout << "info nodes " << nodes
1040 << " nps " << nps(pos)
1041 << " time " << current_search_time() << endl;
1044 if (current_search_time() >= 1000)
1045 cout << "info currmove " << move
1046 << " currmovenumber " << moveCount << endl;
1049 isPvMove = (PvNode && moveCount <= (Root ? MultiPV : 1));
1050 moveIsCheck = pos.move_is_check(move, ci);
1051 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1053 // Step 11. Decide the new search depth
1054 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1056 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1057 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1058 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1059 // lower then ttValue minus a margin then we extend ttMove.
1060 if ( singularExtensionNode
1061 && move == tte->move()
1064 Value ttValue = value_from_tt(tte->value(), ply);
1066 if (abs(ttValue) < VALUE_KNOWN_WIN)
1068 Value b = ttValue - SingularExtensionMargin;
1069 ss->excludedMove = move;
1070 ss->skipNullMove = true;
1071 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1072 ss->skipNullMove = false;
1073 ss->excludedMove = MOVE_NONE;
1074 ss->bestMove = MOVE_NONE;
1080 // Update current move (this must be done after singular extension search)
1081 ss->currentMove = move;
1082 newDepth = depth - (!Root ? ONE_PLY : DEPTH_ZERO) + ext;
1084 // Step 12. Futility pruning (is omitted in PV nodes)
1086 && !captureOrPromotion
1090 && !move_is_castle(move))
1092 // Move count based pruning
1093 if ( moveCount >= futility_move_count(depth)
1094 && !(threatMove && connected_threat(pos, move, threatMove))
1095 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1098 lock_grab(&(sp->lock));
1103 // Value based pruning
1104 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1105 // but fixing this made program slightly weaker.
1106 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1107 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1108 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1110 if (futilityValueScaled < beta)
1114 lock_grab(&(sp->lock));
1115 if (futilityValueScaled > sp->bestValue)
1116 sp->bestValue = bestValue = futilityValueScaled;
1118 else if (futilityValueScaled > bestValue)
1119 bestValue = futilityValueScaled;
1124 // Prune moves with negative SEE at low depths
1125 if ( predictedDepth < 2 * ONE_PLY
1126 && bestValue > value_mated_in(PLY_MAX)
1127 && pos.see_sign(move) < 0)
1130 lock_grab(&(sp->lock));
1136 // Step 13. Make the move
1137 pos.do_move(move, st, ci, moveIsCheck);
1139 if (!SpNode && !captureOrPromotion)
1140 movesSearched[playedMoveCount++] = move;
1142 // Step extra. pv search (only in PV nodes)
1143 // The first move in list is the expected PV
1146 // Aspiration window is disabled in multi-pv case
1147 if (Root && MultiPV > 1)
1148 alpha = -VALUE_INFINITE;
1150 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1154 // Step 14. Reduced depth search
1155 // If the move fails high will be re-searched at full depth.
1156 bool doFullDepthSearch = true;
1158 if ( depth >= 3 * ONE_PLY
1159 && !captureOrPromotion
1161 && !move_is_castle(move)
1162 && ss->killers[0] != move
1163 && ss->killers[1] != move)
1165 ss->reduction = Root ? reduction<PvNode>(depth, moveCount - MultiPV + 1)
1166 : reduction<PvNode>(depth, moveCount);
1169 alpha = SpNode ? sp->alpha : alpha;
1170 Depth d = newDepth - ss->reduction;
1171 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1173 doFullDepthSearch = (value > alpha);
1175 ss->reduction = DEPTH_ZERO; // Restore original reduction
1178 // Step 15. Full depth search
1179 if (doFullDepthSearch)
1181 alpha = SpNode ? sp->alpha : alpha;
1182 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1184 // Step extra. pv search (only in PV nodes)
1185 // Search only for possible new PV nodes, if instead value >= beta then
1186 // parent node fails low with value <= alpha and tries another move.
1187 if (PvNode && value > alpha && (Root || value < beta))
1188 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1192 // Step 16. Undo move
1193 pos.undo_move(move);
1195 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1197 // Step 17. Check for new best move
1200 lock_grab(&(sp->lock));
1201 bestValue = sp->bestValue;
1205 if (!Root && value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1210 sp->bestValue = value;
1214 if (PvNode && value < beta) // We want always alpha < beta
1222 sp->betaCutoff = true;
1224 if (value == value_mate_in(ply + 1))
1225 ss->mateKiller = move;
1227 ss->bestMove = move;
1230 sp->parentSstack->bestMove = move;
1236 // To avoid to exit with bestValue == -VALUE_INFINITE
1237 if (value > bestValue)
1240 // Finished searching the move. If StopRequest is true, the search
1241 // was aborted because the user interrupted the search or because we
1242 // ran out of time. In this case, the return value of the search cannot
1243 // be trusted, and we break out of the loop without updating the best
1248 // Remember searched nodes counts for this move
1249 mp.rm->nodes += pos.nodes_searched() - nodes;
1251 // Step 17. Check for new best move
1252 if (!isPvMove && value <= alpha)
1253 mp.rm->pv_score = -VALUE_INFINITE;
1256 // PV move or new best move!
1259 ss->bestMove = move;
1260 mp.rm->pv_score = value;
1261 mp.rm->extract_pv_from_tt(pos);
1263 // We record how often the best move has been changed in each
1264 // iteration. This information is used for time managment: When
1265 // the best move changes frequently, we allocate some more time.
1266 if (!isPvMove && MultiPV == 1)
1267 Rml.bestMoveChanges++;
1269 Rml.sort_multipv(moveCount);
1271 // Update alpha. In multi-pv we don't use aspiration window, so
1272 // set alpha equal to minimum score among the PV lines.
1274 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1275 else if (value > alpha)
1278 } // PV move or new best move
1281 // Step 18. Check for split
1284 && depth >= ThreadsMgr.min_split_depth()
1285 && ThreadsMgr.active_threads() > 1
1287 && ThreadsMgr.available_thread_exists(threadID)
1289 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1290 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1291 threatMove, mateThreat, moveCount, &mp, PvNode);
1294 // Step 19. Check for mate and stalemate
1295 // All legal moves have been searched and if there are
1296 // no legal moves, it must be mate or stalemate.
1297 // If one move was excluded return fail low score.
1298 if (!SpNode && !moveCount)
1299 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1301 // Step 20. Update tables
1302 // If the search is not aborted, update the transposition table,
1303 // history counters, and killer moves.
1304 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1306 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1307 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1308 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1310 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1312 // Update killers and history only for non capture moves that fails high
1313 if ( bestValue >= beta
1314 && !pos.move_is_capture_or_promotion(move))
1316 update_history(pos, move, depth, movesSearched, playedMoveCount);
1317 update_killers(move, ss->killers);
1323 // Here we have the lock still grabbed
1324 sp->slaves[threadID] = 0;
1325 sp->nodes += pos.nodes_searched();
1326 lock_release(&(sp->lock));
1329 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1334 // qsearch() is the quiescence search function, which is called by the main
1335 // search function when the remaining depth is zero (or, to be more precise,
1336 // less than ONE_PLY).
1338 template <NodeType PvNode>
1339 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1341 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1342 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1343 assert(PvNode || alpha == beta - 1);
1345 assert(ply > 0 && ply < PLY_MAX);
1346 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1350 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1351 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1354 Value oldAlpha = alpha;
1356 ss->bestMove = ss->currentMove = MOVE_NONE;
1358 // Check for an instant draw or maximum ply reached
1359 if (pos.is_draw() || ply >= PLY_MAX - 1)
1362 // Decide whether or not to include checks, this fixes also the type of
1363 // TT entry depth that we are going to use. Note that in qsearch we use
1364 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1365 isCheck = pos.is_check();
1366 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1368 // Transposition table lookup. At PV nodes, we don't use the TT for
1369 // pruning, but only for move ordering.
1370 tte = TT.retrieve(pos.get_key());
1371 ttMove = (tte ? tte->move() : MOVE_NONE);
1373 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1375 ss->bestMove = ttMove; // Can be MOVE_NONE
1376 return value_from_tt(tte->value(), ply);
1379 // Evaluate the position statically
1382 bestValue = futilityBase = -VALUE_INFINITE;
1383 ss->eval = evalMargin = VALUE_NONE;
1384 enoughMaterial = false;
1390 assert(tte->static_value() != VALUE_NONE);
1392 evalMargin = tte->static_value_margin();
1393 ss->eval = bestValue = tte->static_value();
1396 ss->eval = bestValue = evaluate(pos, evalMargin);
1398 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1400 // Stand pat. Return immediately if static value is at least beta
1401 if (bestValue >= beta)
1404 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1409 if (PvNode && bestValue > alpha)
1412 // Futility pruning parameters, not needed when in check
1413 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1414 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1417 // Initialize a MovePicker object for the current position, and prepare
1418 // to search the moves. Because the depth is <= 0 here, only captures,
1419 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1421 MovePicker mp(pos, ttMove, depth, H);
1424 // Loop through the moves until no moves remain or a beta cutoff occurs
1425 while ( alpha < beta
1426 && (move = mp.get_next_move()) != MOVE_NONE)
1428 assert(move_is_ok(move));
1430 moveIsCheck = pos.move_is_check(move, ci);
1438 && !move_is_promotion(move)
1439 && !pos.move_is_passed_pawn_push(move))
1441 futilityValue = futilityBase
1442 + pos.endgame_value_of_piece_on(move_to(move))
1443 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1445 if (futilityValue < alpha)
1447 if (futilityValue > bestValue)
1448 bestValue = futilityValue;
1453 // Detect non-capture evasions that are candidate to be pruned
1454 evasionPrunable = isCheck
1455 && bestValue > value_mated_in(PLY_MAX)
1456 && !pos.move_is_capture(move)
1457 && !pos.can_castle(pos.side_to_move());
1459 // Don't search moves with negative SEE values
1461 && (!isCheck || evasionPrunable)
1463 && !move_is_promotion(move)
1464 && pos.see_sign(move) < 0)
1467 // Don't search useless checks
1472 && !pos.move_is_capture_or_promotion(move)
1473 && ss->eval + PawnValueMidgame / 4 < beta
1474 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1476 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1477 bestValue = ss->eval + PawnValueMidgame / 4;
1482 // Update current move
1483 ss->currentMove = move;
1485 // Make and search the move
1486 pos.do_move(move, st, ci, moveIsCheck);
1487 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1488 pos.undo_move(move);
1490 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1493 if (value > bestValue)
1499 ss->bestMove = move;
1504 // All legal moves have been searched. A special case: If we're in check
1505 // and no legal moves were found, it is checkmate.
1506 if (isCheck && bestValue == -VALUE_INFINITE)
1507 return value_mated_in(ply);
1509 // Update transposition table
1510 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1511 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1513 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1519 // qsearch_scoring() scores each move of a list using a qsearch() evaluation,
1520 // it is used in RootMoveList to get an initial scoring.
1521 void qsearch_scoring(Position& pos, MoveStack* mlist, MoveStack* last) {
1523 SearchStack ss[PLY_MAX_PLUS_2];
1526 memset(ss, 0, 4 * sizeof(SearchStack));
1527 ss[0].eval = ss[0].evalMargin = VALUE_NONE;
1529 for (MoveStack* cur = mlist; cur != last; cur++)
1531 ss[0].currentMove = cur->move;
1532 pos.do_move(cur->move, st);
1533 cur->score = -qsearch<PV>(pos, ss+1, -VALUE_INFINITE, VALUE_INFINITE, DEPTH_ZERO, 1);
1534 pos.undo_move(cur->move);
1539 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1540 // bestValue is updated only when returning false because in that case move
1543 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1545 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1546 Square from, to, ksq, victimSq;
1549 Value futilityValue, bv = *bestValue;
1551 from = move_from(move);
1553 them = opposite_color(pos.side_to_move());
1554 ksq = pos.king_square(them);
1555 kingAtt = pos.attacks_from<KING>(ksq);
1556 pc = pos.piece_on(from);
1558 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1559 oldAtt = pos.attacks_from(pc, from, occ);
1560 newAtt = pos.attacks_from(pc, to, occ);
1562 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1563 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1565 if (!(b && (b & (b - 1))))
1568 // Rule 2. Queen contact check is very dangerous
1569 if ( type_of_piece(pc) == QUEEN
1570 && bit_is_set(kingAtt, to))
1573 // Rule 3. Creating new double threats with checks
1574 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1578 victimSq = pop_1st_bit(&b);
1579 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1581 // Note that here we generate illegal "double move"!
1582 if ( futilityValue >= beta
1583 && pos.see_sign(make_move(from, victimSq)) >= 0)
1586 if (futilityValue > bv)
1590 // Update bestValue only if check is not dangerous (because we will prune the move)
1596 // connected_moves() tests whether two moves are 'connected' in the sense
1597 // that the first move somehow made the second move possible (for instance
1598 // if the moving piece is the same in both moves). The first move is assumed
1599 // to be the move that was made to reach the current position, while the
1600 // second move is assumed to be a move from the current position.
1602 bool connected_moves(const Position& pos, Move m1, Move m2) {
1604 Square f1, t1, f2, t2;
1607 assert(m1 && move_is_ok(m1));
1608 assert(m2 && move_is_ok(m2));
1610 // Case 1: The moving piece is the same in both moves
1616 // Case 2: The destination square for m2 was vacated by m1
1622 // Case 3: Moving through the vacated square
1623 if ( piece_is_slider(pos.piece_on(f2))
1624 && bit_is_set(squares_between(f2, t2), f1))
1627 // Case 4: The destination square for m2 is defended by the moving piece in m1
1628 p = pos.piece_on(t1);
1629 if (bit_is_set(pos.attacks_from(p, t1), t2))
1632 // Case 5: Discovered check, checking piece is the piece moved in m1
1633 if ( piece_is_slider(p)
1634 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1635 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1637 // discovered_check_candidates() works also if the Position's side to
1638 // move is the opposite of the checking piece.
1639 Color them = opposite_color(pos.side_to_move());
1640 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1642 if (bit_is_set(dcCandidates, f2))
1649 // value_is_mate() checks if the given value is a mate one eventually
1650 // compensated for the ply.
1652 bool value_is_mate(Value value) {
1654 assert(abs(value) <= VALUE_INFINITE);
1656 return value <= value_mated_in(PLY_MAX)
1657 || value >= value_mate_in(PLY_MAX);
1661 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1662 // "plies to mate from the current ply". Non-mate scores are unchanged.
1663 // The function is called before storing a value to the transposition table.
1665 Value value_to_tt(Value v, int ply) {
1667 if (v >= value_mate_in(PLY_MAX))
1670 if (v <= value_mated_in(PLY_MAX))
1677 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1678 // the transposition table to a mate score corrected for the current ply.
1680 Value value_from_tt(Value v, int ply) {
1682 if (v >= value_mate_in(PLY_MAX))
1685 if (v <= value_mated_in(PLY_MAX))
1692 // extension() decides whether a move should be searched with normal depth,
1693 // or with extended depth. Certain classes of moves (checking moves, in
1694 // particular) are searched with bigger depth than ordinary moves and in
1695 // any case are marked as 'dangerous'. Note that also if a move is not
1696 // extended, as example because the corresponding UCI option is set to zero,
1697 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1698 template <NodeType PvNode>
1699 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1700 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1702 assert(m != MOVE_NONE);
1704 Depth result = DEPTH_ZERO;
1705 *dangerous = moveIsCheck | mateThreat;
1709 if (moveIsCheck && pos.see_sign(m) >= 0)
1710 result += CheckExtension[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 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1850 // update_killers() add a good move that produced a beta-cutoff
1851 // among the killer moves of that ply.
1853 void update_killers(Move m, Move killers[]) {
1855 if (m != killers[0])
1857 killers[1] = killers[0];
1863 // update_gains() updates the gains table of a non-capture move given
1864 // the static position evaluation before and after the move.
1866 void update_gains(const Position& pos, Move m, Value before, Value after) {
1869 && before != VALUE_NONE
1870 && after != VALUE_NONE
1871 && pos.captured_piece_type() == PIECE_TYPE_NONE
1872 && !move_is_special(m))
1873 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1877 // value_to_uci() converts a value to a string suitable for use with the UCI
1878 // protocol specifications:
1880 // cp <x> The score from the engine's point of view in centipawns.
1881 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1882 // use negative values for y.
1884 std::string value_to_uci(Value v) {
1886 std::stringstream s;
1888 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1889 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1891 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2 );
1897 // current_search_time() returns the number of milliseconds which have passed
1898 // since the beginning of the current search.
1900 int current_search_time() {
1902 return get_system_time() - SearchStartTime;
1906 // nps() computes the current nodes/second count
1908 int nps(const Position& pos) {
1910 int t = current_search_time();
1911 return (t > 0 ? int((pos.nodes_searched() * 1000) / t) : 0);
1915 // poll() performs two different functions: It polls for user input, and it
1916 // looks at the time consumed so far and decides if it's time to abort the
1919 void poll(const Position& pos) {
1921 static int lastInfoTime;
1922 int t = current_search_time();
1925 if (input_available())
1927 // We are line oriented, don't read single chars
1928 std::string command;
1930 if (!std::getline(std::cin, command))
1933 if (command == "quit")
1935 // Quit the program as soon as possible
1937 QuitRequest = StopRequest = true;
1940 else if (command == "stop")
1942 // Stop calculating as soon as possible, but still send the "bestmove"
1943 // and possibly the "ponder" token when finishing the search.
1947 else if (command == "ponderhit")
1949 // The opponent has played the expected move. GUI sends "ponderhit" if
1950 // we were told to ponder on the same move the opponent has played. We
1951 // should continue searching but switching from pondering to normal search.
1954 if (StopOnPonderhit)
1959 // Print search information
1963 else if (lastInfoTime > t)
1964 // HACK: Must be a new search where we searched less than
1965 // NodesBetweenPolls nodes during the first second of search.
1968 else if (t - lastInfoTime >= 1000)
1975 if (dbg_show_hit_rate)
1976 dbg_print_hit_rate();
1978 // Send info on searched nodes as soon as we return to root
1979 SendSearchedNodes = true;
1982 // Should we stop the search?
1986 bool stillAtFirstMove = FirstRootMove
1987 && !AspirationFailLow
1988 && t > TimeMgr.available_time();
1990 bool noMoreTime = t > TimeMgr.maximum_time()
1991 || stillAtFirstMove;
1993 if ( (UseTimeManagement && noMoreTime)
1994 || (ExactMaxTime && t >= ExactMaxTime)
1995 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
2000 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2001 // while the program is pondering. The point is to work around a wrinkle in
2002 // the UCI protocol: When pondering, the engine is not allowed to give a
2003 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2004 // We simply wait here until one of these commands is sent, and return,
2005 // after which the bestmove and pondermove will be printed.
2007 void wait_for_stop_or_ponderhit() {
2009 std::string command;
2013 // Wait for a command from stdin
2014 if (!std::getline(std::cin, command))
2017 if (command == "quit")
2022 else if (command == "ponderhit" || command == "stop")
2028 // init_thread() is the function which is called when a new thread is
2029 // launched. It simply calls the idle_loop() function with the supplied
2030 // threadID. There are two versions of this function; one for POSIX
2031 // threads and one for Windows threads.
2033 #if !defined(_MSC_VER)
2035 void* init_thread(void* threadID) {
2037 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2043 DWORD WINAPI init_thread(LPVOID threadID) {
2045 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2052 /// The ThreadsManager class
2055 // read_uci_options() updates number of active threads and other internal
2056 // parameters according to the UCI options values. It is called before
2057 // to start a new search.
2059 void ThreadsManager::read_uci_options() {
2061 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2062 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2063 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2064 activeThreads = Options["Threads"].value<int>();
2068 // idle_loop() is where the threads are parked when they have no work to do.
2069 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2070 // object for which the current thread is the master.
2072 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2074 assert(threadID >= 0 && threadID < MAX_THREADS);
2077 bool allFinished = false;
2081 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2082 // master should exit as last one.
2083 if (allThreadsShouldExit)
2086 threads[threadID].state = THREAD_TERMINATED;
2090 // If we are not thinking, wait for a condition to be signaled
2091 // instead of wasting CPU time polling for work.
2092 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2093 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2095 assert(!sp || useSleepingThreads);
2096 assert(threadID != 0 || useSleepingThreads);
2098 if (threads[threadID].state == THREAD_INITIALIZING)
2099 threads[threadID].state = THREAD_AVAILABLE;
2101 // Grab the lock to avoid races with wake_sleeping_thread()
2102 lock_grab(&sleepLock[threadID]);
2104 // If we are master and all slaves have finished do not go to sleep
2105 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2106 allFinished = (i == activeThreads);
2108 if (allFinished || allThreadsShouldExit)
2110 lock_release(&sleepLock[threadID]);
2114 // Do sleep here after retesting sleep conditions
2115 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2116 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2118 lock_release(&sleepLock[threadID]);
2121 // If this thread has been assigned work, launch a search
2122 if (threads[threadID].state == THREAD_WORKISWAITING)
2124 assert(!allThreadsShouldExit);
2126 threads[threadID].state = THREAD_SEARCHING;
2128 // Here we call search() with SplitPoint template parameter set to true
2129 SplitPoint* tsp = threads[threadID].splitPoint;
2130 Position pos(*tsp->pos, threadID);
2131 SearchStack* ss = tsp->sstack[threadID] + 1;
2135 search<PV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2137 search<NonPV, true, false>(pos, ss, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2139 assert(threads[threadID].state == THREAD_SEARCHING);
2141 threads[threadID].state = THREAD_AVAILABLE;
2143 // Wake up master thread so to allow it to return from the idle loop in
2144 // case we are the last slave of the split point.
2145 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2146 wake_sleeping_thread(tsp->master);
2149 // If this thread is the master of a split point and all slaves have
2150 // finished their work at this split point, return from the idle loop.
2151 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2152 allFinished = (i == activeThreads);
2156 // Because sp->slaves[] is reset under lock protection,
2157 // be sure sp->lock has been released before to return.
2158 lock_grab(&(sp->lock));
2159 lock_release(&(sp->lock));
2161 // In helpful master concept a master can help only a sub-tree, and
2162 // because here is all finished is not possible master is booked.
2163 assert(threads[threadID].state == THREAD_AVAILABLE);
2165 threads[threadID].state = THREAD_SEARCHING;
2172 // init_threads() is called during startup. It launches all helper threads,
2173 // and initializes the split point stack and the global locks and condition
2176 void ThreadsManager::init_threads() {
2178 int i, arg[MAX_THREADS];
2181 // Initialize global locks
2184 for (i = 0; i < MAX_THREADS; i++)
2186 lock_init(&sleepLock[i]);
2187 cond_init(&sleepCond[i]);
2190 // Initialize splitPoints[] locks
2191 for (i = 0; i < MAX_THREADS; i++)
2192 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2193 lock_init(&(threads[i].splitPoints[j].lock));
2195 // Will be set just before program exits to properly end the threads
2196 allThreadsShouldExit = false;
2198 // Threads will be put all threads to sleep as soon as created
2201 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2202 threads[0].state = THREAD_SEARCHING;
2203 for (i = 1; i < MAX_THREADS; i++)
2204 threads[i].state = THREAD_INITIALIZING;
2206 // Launch the helper threads
2207 for (i = 1; i < MAX_THREADS; i++)
2211 #if !defined(_MSC_VER)
2212 pthread_t pthread[1];
2213 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2214 pthread_detach(pthread[0]);
2216 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2220 cout << "Failed to create thread number " << i << endl;
2224 // Wait until the thread has finished launching and is gone to sleep
2225 while (threads[i].state == THREAD_INITIALIZING) {}
2230 // exit_threads() is called when the program exits. It makes all the
2231 // helper threads exit cleanly.
2233 void ThreadsManager::exit_threads() {
2235 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2237 // Wake up all the threads and waits for termination
2238 for (int i = 1; i < MAX_THREADS; i++)
2240 wake_sleeping_thread(i);
2241 while (threads[i].state != THREAD_TERMINATED) {}
2244 // Now we can safely destroy the locks
2245 for (int i = 0; i < MAX_THREADS; i++)
2246 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2247 lock_destroy(&(threads[i].splitPoints[j].lock));
2249 lock_destroy(&mpLock);
2251 // Now we can safely destroy the wait conditions
2252 for (int i = 0; i < MAX_THREADS; i++)
2254 lock_destroy(&sleepLock[i]);
2255 cond_destroy(&sleepCond[i]);
2260 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2261 // the thread's currently active split point, or in some ancestor of
2262 // the current split point.
2264 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2266 assert(threadID >= 0 && threadID < activeThreads);
2268 SplitPoint* sp = threads[threadID].splitPoint;
2270 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2275 // thread_is_available() checks whether the thread with threadID "slave" is
2276 // available to help the thread with threadID "master" at a split point. An
2277 // obvious requirement is that "slave" must be idle. With more than two
2278 // threads, this is not by itself sufficient: If "slave" is the master of
2279 // some active split point, it is only available as a slave to the other
2280 // threads which are busy searching the split point at the top of "slave"'s
2281 // split point stack (the "helpful master concept" in YBWC terminology).
2283 bool ThreadsManager::thread_is_available(int slave, int master) const {
2285 assert(slave >= 0 && slave < activeThreads);
2286 assert(master >= 0 && master < activeThreads);
2287 assert(activeThreads > 1);
2289 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2292 // Make a local copy to be sure doesn't change under our feet
2293 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2295 // No active split points means that the thread is available as
2296 // a slave for any other thread.
2297 if (localActiveSplitPoints == 0 || activeThreads == 2)
2300 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2301 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2302 // could have been set to 0 by another thread leading to an out of bound access.
2303 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2310 // available_thread_exists() tries to find an idle thread which is available as
2311 // a slave for the thread with threadID "master".
2313 bool ThreadsManager::available_thread_exists(int master) const {
2315 assert(master >= 0 && master < activeThreads);
2316 assert(activeThreads > 1);
2318 for (int i = 0; i < activeThreads; i++)
2319 if (thread_is_available(i, master))
2326 // split() does the actual work of distributing the work at a node between
2327 // several available threads. If it does not succeed in splitting the
2328 // node (because no idle threads are available, or because we have no unused
2329 // split point objects), the function immediately returns. If splitting is
2330 // possible, a SplitPoint object is initialized with all the data that must be
2331 // copied to the helper threads and we tell our helper threads that they have
2332 // been assigned work. This will cause them to instantly leave their idle loops and
2333 // call search().When all threads have returned from search() then split() returns.
2335 template <bool Fake>
2336 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2337 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2338 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2339 assert(pos.is_ok());
2340 assert(ply > 0 && ply < PLY_MAX);
2341 assert(*bestValue >= -VALUE_INFINITE);
2342 assert(*bestValue <= *alpha);
2343 assert(*alpha < beta);
2344 assert(beta <= VALUE_INFINITE);
2345 assert(depth > DEPTH_ZERO);
2346 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2347 assert(activeThreads > 1);
2349 int i, master = pos.thread();
2350 Thread& masterThread = threads[master];
2354 // If no other thread is available to help us, or if we have too many
2355 // active split points, don't split.
2356 if ( !available_thread_exists(master)
2357 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2359 lock_release(&mpLock);
2363 // Pick the next available split point object from the split point stack
2364 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2366 // Initialize the split point object
2367 splitPoint.parent = masterThread.splitPoint;
2368 splitPoint.master = master;
2369 splitPoint.betaCutoff = false;
2370 splitPoint.ply = ply;
2371 splitPoint.depth = depth;
2372 splitPoint.threatMove = threatMove;
2373 splitPoint.mateThreat = mateThreat;
2374 splitPoint.alpha = *alpha;
2375 splitPoint.beta = beta;
2376 splitPoint.pvNode = pvNode;
2377 splitPoint.bestValue = *bestValue;
2379 splitPoint.moveCount = moveCount;
2380 splitPoint.pos = &pos;
2381 splitPoint.nodes = 0;
2382 splitPoint.parentSstack = ss;
2383 for (i = 0; i < activeThreads; i++)
2384 splitPoint.slaves[i] = 0;
2386 masterThread.splitPoint = &splitPoint;
2388 // If we are here it means we are not available
2389 assert(masterThread.state != THREAD_AVAILABLE);
2391 int workersCnt = 1; // At least the master is included
2393 // Allocate available threads setting state to THREAD_BOOKED
2394 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2395 if (thread_is_available(i, master))
2397 threads[i].state = THREAD_BOOKED;
2398 threads[i].splitPoint = &splitPoint;
2399 splitPoint.slaves[i] = 1;
2403 assert(Fake || workersCnt > 1);
2405 // We can release the lock because slave threads are already booked and master is not available
2406 lock_release(&mpLock);
2408 // Tell the threads that they have work to do. This will make them leave
2409 // their idle loop. But before copy search stack tail for each thread.
2410 for (i = 0; i < activeThreads; i++)
2411 if (i == master || splitPoint.slaves[i])
2413 memcpy(splitPoint.sstack[i], ss - 1, 4 * sizeof(SearchStack));
2415 assert(i == master || threads[i].state == THREAD_BOOKED);
2417 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2419 if (useSleepingThreads && i != master)
2420 wake_sleeping_thread(i);
2423 // Everything is set up. The master thread enters the idle loop, from
2424 // which it will instantly launch a search, because its state is
2425 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2426 // idle loop, which means that the main thread will return from the idle
2427 // loop when all threads have finished their work at this split point.
2428 idle_loop(master, &splitPoint);
2430 // We have returned from the idle loop, which means that all threads are
2431 // finished. Update alpha and bestValue, and return.
2434 *alpha = splitPoint.alpha;
2435 *bestValue = splitPoint.bestValue;
2436 masterThread.activeSplitPoints--;
2437 masterThread.splitPoint = splitPoint.parent;
2438 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2440 lock_release(&mpLock);
2444 // wake_sleeping_thread() wakes up the thread with the given threadID
2445 // when it is time to start a new search.
2447 void ThreadsManager::wake_sleeping_thread(int threadID) {
2449 lock_grab(&sleepLock[threadID]);
2450 cond_signal(&sleepCond[threadID]);
2451 lock_release(&sleepLock[threadID]);
2455 /// RootMove and RootMoveList method's definitions
2457 RootMove::RootMove() {
2460 pv_score = non_pv_score = -VALUE_INFINITE;
2464 RootMove& RootMove::operator=(const RootMove& rm) {
2466 const Move* src = rm.pv;
2469 // Avoid a costly full rm.pv[] copy
2470 do *dst++ = *src; while (*src++ != MOVE_NONE);
2473 pv_score = rm.pv_score;
2474 non_pv_score = rm.non_pv_score;
2478 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2479 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2480 // allow to always have a ponder move even when we fail high at root and also a
2481 // long PV to print that is important for position analysis.
2483 void RootMove::extract_pv_from_tt(Position& pos) {
2485 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2489 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2491 pos.do_move(pv[0], *st++);
2493 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2494 && tte->move() != MOVE_NONE
2495 && move_is_legal(pos, tte->move())
2497 && (!pos.is_draw() || ply < 2))
2499 pv[ply] = tte->move();
2500 pos.do_move(pv[ply++], *st++);
2502 pv[ply] = MOVE_NONE;
2504 do pos.undo_move(pv[--ply]); while (ply);
2507 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2508 // the PV back into the TT. This makes sure the old PV moves are searched
2509 // first, even if the old TT entries have been overwritten.
2511 void RootMove::insert_pv_in_tt(Position& pos) {
2513 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2516 Value v, m = VALUE_NONE;
2519 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2523 tte = TT.retrieve(k);
2525 // Don't overwrite exsisting correct entries
2526 if (!tte || tte->move() != pv[ply])
2528 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2529 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2531 pos.do_move(pv[ply], *st++);
2533 } while (pv[++ply] != MOVE_NONE);
2535 do pos.undo_move(pv[--ply]); while (ply);
2538 // pv_info_to_uci() returns a string with information on the current PV line
2539 // formatted according to UCI specification and eventually writes the info
2540 // to a log file. It is called at each iteration or after a new pv is found.
2542 std::string RootMove::pv_info_to_uci(Position& pos, Depth depth, Value alpha, Value beta, int pvLine) {
2544 std::stringstream s, l;
2547 while (*m != MOVE_NONE)
2550 s << "info depth " << depth / ONE_PLY
2551 << " seldepth " << int(m - pv)
2552 << " multipv " << pvLine + 1
2553 << " score " << value_to_uci(pv_score)
2554 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2555 << " time " << current_search_time()
2556 << " nodes " << pos.nodes_searched()
2557 << " nps " << nps(pos)
2558 << " pv " << l.str();
2560 if (UseLogFile && pvLine == 0)
2562 ValueType t = pv_score >= beta ? VALUE_TYPE_LOWER :
2563 pv_score <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT;
2565 LogFile << pretty_pv(pos, current_search_time(), depth / ONE_PLY, pv_score, t, pv) << endl;
2571 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2573 MoveStack mlist[MOVES_MAX];
2577 bestMoveChanges = 0;
2579 // Generate all legal moves and score them
2580 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2581 qsearch_scoring(pos, mlist, last);
2583 // Add each move to the RootMoveList's vector
2584 for (MoveStack* cur = mlist; cur != last; cur++)
2586 // If we have a searchMoves[] list then verify cur->move
2587 // is in the list before to add it.
2588 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2590 if (searchMoves[0] && *sm != cur->move)
2594 rm.pv[0] = cur->move;
2595 rm.pv[1] = MOVE_NONE;
2596 rm.pv_score = Value(cur->score);