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, int depth, Value alpha, Value beta, int pvLine);
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 // Step 12. Futility pruning
214 // Futility margin for quiescence search
215 const Value FutilityMarginQS = Value(0x80);
217 // Futility lookup tables (initialized at startup) and their getter functions
218 Value FutilityMarginsMatrix[16][64]; // [depth][moveNumber]
219 int FutilityMoveCountArray[32]; // [depth]
221 inline Value futility_margin(Depth d, int mn) { return d < 7 * ONE_PLY ? FutilityMarginsMatrix[Max(d, 1)][Min(mn, 63)] : 2 * VALUE_INFINITE; }
222 inline int futility_move_count(Depth d) { return d < 16 * ONE_PLY ? FutilityMoveCountArray[d] : 512; }
224 // Step 14. Reduced search
226 // Reduction lookup tables (initialized at startup) and their getter functions
227 int8_t ReductionMatrix[2][64][64]; // [pv][depth][moveNumber]
229 template <NodeType PV>
230 inline Depth reduction(Depth d, int mn) { return (Depth) ReductionMatrix[PV][Min(d / 2, 63)][Min(mn, 63)]; }
232 // Easy move margin. An easy move candidate must be at least this much
233 // better than the second best move.
234 const Value EasyMoveMargin = Value(0x200);
237 /// Namespace variables
248 // Time management variables
249 int SearchStartTime, MaxNodes, MaxDepth, ExactMaxTime;
250 bool UseTimeManagement, InfiniteSearch, Pondering, StopOnPonderhit;
251 bool FirstRootMove, StopRequest, QuitRequest, AspirationFailLow;
256 std::ofstream LogFile;
258 // Multi-threads manager object
259 ThreadsManager ThreadsMgr;
261 // Node counters, used only by thread[0] but try to keep in different cache
262 // lines (64 bytes each) from the heavy multi-thread read accessed variables.
263 bool SendSearchedNodes;
265 int NodesBetweenPolls = 30000;
272 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove);
274 template <NodeType PvNode, bool SpNode, bool Root>
275 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
277 template <NodeType PvNode>
278 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply);
280 template <NodeType PvNode>
281 inline Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
283 return depth < ONE_PLY ? qsearch<PvNode>(pos, ss, alpha, beta, DEPTH_ZERO, ply)
284 : search<PvNode, false, false>(pos, ss, alpha, beta, depth, ply);
287 template <NodeType PvNode>
288 Depth extension(const Position& pos, Move m, bool captureOrPromotion, bool moveIsCheck, bool mateThreat, bool* dangerous);
290 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue);
291 bool connected_moves(const Position& pos, Move m1, Move m2);
292 bool value_is_mate(Value value);
293 Value value_to_tt(Value v, int ply);
294 Value value_from_tt(Value v, int ply);
295 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
296 bool connected_threat(const Position& pos, Move m, Move threat);
297 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
298 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
299 void update_killers(Move m, Move killers[]);
300 void update_gains(const Position& pos, Move move, Value before, Value after);
302 int current_search_time();
303 std::string value_to_uci(Value v);
304 std::string speed_to_uci(int64_t nodes);
305 void poll(const Position& pos);
306 void wait_for_stop_or_ponderhit();
308 #if !defined(_MSC_VER)
309 void* init_thread(void* threadID);
311 DWORD WINAPI init_thread(LPVOID threadID);
315 // MovePickerExt is an extended MovePicker used to choose at compile time
316 // the proper move source according to the type of node.
317 template<bool SpNode, bool Root> struct MovePickerExt;
319 // In Root nodes use RootMoveList Rml as source. Score and sort the root moves
320 // before to search them.
321 template<> struct MovePickerExt<false, true> : public MovePicker {
323 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b)
324 : MovePicker(p, ttm, d, h, ss, b), firstCall(true) {
326 Value score = VALUE_ZERO;
328 // Score root moves using the standard way used in main search, the moves
329 // are scored according to the order in which they are returned by MovePicker.
330 // This is the second order score that is used to compare the moves when
331 // the first order pv scores of both moves are equal.
332 while ((move = MovePicker::get_next_move()) != MOVE_NONE)
333 for (rm = Rml.begin(); rm != Rml.end(); ++rm)
334 if (rm->pv[0] == move)
336 rm->non_pv_score = score--;
344 Move get_next_move() {
351 return rm != Rml.end() ? rm->pv[0] : MOVE_NONE;
354 RootMoveList::iterator rm;
358 // In SpNodes use split point's shared MovePicker object as move source
359 template<> struct MovePickerExt<true, false> : public MovePicker {
361 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
362 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b),
365 Move get_next_move() { return mp->get_next_move(); }
367 RootMoveList::iterator rm; // Dummy, needed to compile
371 // Default case, create and use a MovePicker object as source
372 template<> struct MovePickerExt<false, false> : public MovePicker {
374 MovePickerExt(const Position& p, Move ttm, Depth d, const History& h,
375 SearchStack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {}
377 RootMoveList::iterator rm; // Dummy, needed to compile
387 /// init_threads(), exit_threads() and nodes_searched() are helpers to
388 /// give accessibility to some TM methods from outside of current file.
390 void init_threads() { ThreadsMgr.init_threads(); }
391 void exit_threads() { ThreadsMgr.exit_threads(); }
394 /// init_search() is called during startup. It initializes various lookup tables
398 int d; // depth (ONE_PLY == 2)
399 int hd; // half depth (ONE_PLY == 1)
402 // Init reductions array
403 for (hd = 1; hd < 64; hd++) for (mc = 1; mc < 64; mc++)
405 double pvRed = log(double(hd)) * log(double(mc)) / 3.0;
406 double nonPVRed = 0.33 + log(double(hd)) * log(double(mc)) / 2.25;
407 ReductionMatrix[PV][hd][mc] = (int8_t) ( pvRed >= 1.0 ? floor( pvRed * int(ONE_PLY)) : 0);
408 ReductionMatrix[NonPV][hd][mc] = (int8_t) (nonPVRed >= 1.0 ? floor(nonPVRed * int(ONE_PLY)) : 0);
411 // Init futility margins array
412 for (d = 1; d < 16; d++) for (mc = 0; mc < 64; mc++)
413 FutilityMarginsMatrix[d][mc] = Value(112 * int(log(double(d * d) / 2) / log(2.0) + 1.001) - 8 * mc + 45);
415 // Init futility move count array
416 for (d = 0; d < 32; d++)
417 FutilityMoveCountArray[d] = int(3.001 + 0.25 * pow(d, 2.0));
421 /// perft() is our utility to verify move generation is bug free. All the legal
422 /// moves up to given depth are generated and counted and the sum returned.
424 int64_t perft(Position& pos, Depth depth)
426 MoveStack mlist[MOVES_MAX];
431 // Generate all legal moves
432 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
434 // If we are at the last ply we don't need to do and undo
435 // the moves, just to count them.
436 if (depth <= ONE_PLY)
437 return int(last - mlist);
439 // Loop through all legal moves
441 for (MoveStack* cur = mlist; cur != last; cur++)
444 pos.do_move(m, st, ci, pos.move_is_check(m, ci));
445 sum += perft(pos, depth - ONE_PLY);
452 /// think() is the external interface to Stockfish's search, and is called when
453 /// the program receives the UCI 'go' command. It initializes various
454 /// search-related global variables, and calls id_loop(). It returns false
455 /// when a quit command is received during the search.
457 bool think(Position& pos, bool infinite, bool ponder, int time[], int increment[],
458 int movesToGo, int maxDepth, int maxNodes, int maxTime, Move searchMoves[]) {
460 // Initialize global search variables
461 StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = SendSearchedNodes = false;
463 SearchStartTime = get_system_time();
464 ExactMaxTime = maxTime;
467 InfiniteSearch = infinite;
469 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
471 // Look for a book move, only during games, not tests
472 if (UseTimeManagement && Options["OwnBook"].value<bool>())
474 if (Options["Book File"].value<std::string>() != OpeningBook.name())
475 OpeningBook.open(Options["Book File"].value<std::string>());
477 Move bookMove = OpeningBook.get_move(pos, Options["Best Book Move"].value<bool>());
478 if (bookMove != MOVE_NONE)
481 wait_for_stop_or_ponderhit();
483 cout << "bestmove " << bookMove << endl;
488 // Read UCI option values
489 TT.set_size(Options["Hash"].value<int>());
490 if (Options["Clear Hash"].value<bool>())
492 Options["Clear Hash"].set_value("false");
496 CheckExtension[1] = Options["Check Extension (PV nodes)"].value<Depth>();
497 CheckExtension[0] = Options["Check Extension (non-PV nodes)"].value<Depth>();
498 PawnPushTo7thExtension[1] = Options["Pawn Push to 7th Extension (PV nodes)"].value<Depth>();
499 PawnPushTo7thExtension[0] = Options["Pawn Push to 7th Extension (non-PV nodes)"].value<Depth>();
500 PassedPawnExtension[1] = Options["Passed Pawn Extension (PV nodes)"].value<Depth>();
501 PassedPawnExtension[0] = Options["Passed Pawn Extension (non-PV nodes)"].value<Depth>();
502 PawnEndgameExtension[1] = Options["Pawn Endgame Extension (PV nodes)"].value<Depth>();
503 PawnEndgameExtension[0] = Options["Pawn Endgame Extension (non-PV nodes)"].value<Depth>();
504 MateThreatExtension[1] = Options["Mate Threat Extension (PV nodes)"].value<Depth>();
505 MateThreatExtension[0] = Options["Mate Threat Extension (non-PV nodes)"].value<Depth>();
506 MultiPV = Options["MultiPV"].value<int>();
507 UseLogFile = Options["Use Search Log"].value<bool>();
509 read_evaluation_uci_options(pos.side_to_move());
511 // Set the number of active threads
512 ThreadsMgr.read_uci_options();
513 init_eval(ThreadsMgr.active_threads());
515 // Wake up needed threads
516 for (int i = 1; i < ThreadsMgr.active_threads(); i++)
517 ThreadsMgr.wake_sleeping_thread(i);
520 int myTime = time[pos.side_to_move()];
521 int myIncrement = increment[pos.side_to_move()];
522 if (UseTimeManagement)
523 TimeMgr.init(myTime, myIncrement, movesToGo, pos.startpos_ply_counter());
525 // Set best NodesBetweenPolls interval to avoid lagging under
526 // heavy time pressure.
528 NodesBetweenPolls = Min(MaxNodes, 30000);
529 else if (myTime && myTime < 1000)
530 NodesBetweenPolls = 1000;
531 else if (myTime && myTime < 5000)
532 NodesBetweenPolls = 5000;
534 NodesBetweenPolls = 30000;
536 // Write search information to log file
539 std::string name = Options["Search Log Filename"].value<std::string>();
540 LogFile.open(name.c_str(), std::ios::out | std::ios::app);
542 LogFile << "\nSearching: " << pos.to_fen()
543 << "\ninfinite: " << infinite
544 << " ponder: " << ponder
545 << " time: " << myTime
546 << " increment: " << myIncrement
547 << " moves to go: " << movesToGo
551 // We're ready to start thinking. Call the iterative deepening loop function
552 Move ponderMove = MOVE_NONE;
553 Move bestMove = id_loop(pos, searchMoves, &ponderMove);
555 // Print final search statistics
556 cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
560 int t = current_search_time();
562 LogFile << "Nodes: " << pos.nodes_searched()
563 << "\nNodes/second: " << (t > 0 ? int(pos.nodes_searched() * 1000 / t) : 0)
564 << "\nBest move: " << move_to_san(pos, bestMove);
567 pos.do_move(bestMove, st);
568 LogFile << "\nPonder move: " << move_to_san(pos, ponderMove) << endl;
569 pos.undo_move(bestMove); // Return from think() with unchanged position
573 // This makes all the threads to go to sleep
574 ThreadsMgr.set_active_threads(1);
576 // If we are pondering or in infinite search, we shouldn't print the
577 // best move before we are told to do so.
578 if (!StopRequest && (Pondering || InfiniteSearch))
579 wait_for_stop_or_ponderhit();
581 // Could be both MOVE_NONE when searching on a stalemate position
582 cout << "bestmove " << bestMove << " ponder " << ponderMove << endl;
590 // id_loop() is the main iterative deepening loop. It calls search() repeatedly
591 // with increasing depth until the allocated thinking time has been consumed,
592 // user stops the search, or the maximum search depth is reached.
594 Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) {
596 SearchStack ss[PLY_MAX_PLUS_2];
597 Value bestValues[PLY_MAX_PLUS_2];
598 int bestMoveChanges[PLY_MAX_PLUS_2];
599 int depth, researchCountFL, researchCountFH, aspirationDelta;
600 Value value, alpha, beta;
601 Move bestMove, easyMove;
603 // Moves to search are verified and copied
604 Rml.init(pos, searchMoves);
606 // Initialize FIXME move before Rml.init()
609 memset(ss, 0, 4 * sizeof(SearchStack));
610 *ponderMove = bestMove = easyMove = MOVE_NONE;
611 depth = aspirationDelta = 0;
612 ss->currentMove = MOVE_NULL; // Hack to skip update_gains()
613 alpha = -VALUE_INFINITE, beta = VALUE_INFINITE;
615 // Handle special case of searching on a mate/stalemate position
618 cout << "info depth 0 score "
619 << value_to_uci(pos.is_check() ? -VALUE_MATE : VALUE_DRAW)
625 // Iterative deepening loop
626 while (++depth <= PLY_MAX && (!MaxDepth || depth <= MaxDepth) && !StopRequest)
628 Rml.bestMoveChanges = researchCountFL = researchCountFH = 0;
629 cout << "info depth " << depth << endl;
631 // Calculate dynamic aspiration window based on previous iterations
632 if (MultiPV == 1 && depth >= 5 && abs(bestValues[depth - 1]) < VALUE_KNOWN_WIN)
634 int prevDelta1 = bestValues[depth - 1] - bestValues[depth - 2];
635 int prevDelta2 = bestValues[depth - 2] - bestValues[depth - 3];
637 aspirationDelta = Min(Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16), 24);
638 aspirationDelta = (aspirationDelta + 7) / 8 * 8; // Round to match grainSize
640 alpha = Max(bestValues[depth - 1] - aspirationDelta, -VALUE_INFINITE);
641 beta = Min(bestValues[depth - 1] + aspirationDelta, VALUE_INFINITE);
644 // Start with a small aspiration window and, in case of fail high/low,
645 // research with bigger window until not failing high/low anymore.
648 // Search starting from ss+1 to allow calling update_gains()
649 value = search<PV, false, true>(pos, ss+1, alpha, beta, depth * ONE_PLY, 0);
651 // Send PV line to GUI and write to transposition table in case the
652 // relevant entries have been overwritten during the search.
653 for (int i = 0; i < Min(MultiPV, (int)Rml.size()); i++)
655 Rml[i].insert_pv_in_tt(pos);
656 cout << set960(pos.is_chess960())
657 << Rml[i].pv_info_to_uci(pos, depth, alpha, beta, i) << endl;
660 // Value cannot be trusted. Break out immediately!
664 assert(value >= alpha);
666 // In case of failing high/low increase aspiration window and research,
667 // otherwise exit the fail high/low loop.
670 beta = Min(beta + aspirationDelta * (1 << researchCountFH), VALUE_INFINITE);
673 else if (value <= alpha)
675 AspirationFailLow = true;
676 StopOnPonderhit = false;
678 alpha = Max(alpha - aspirationDelta * (1 << researchCountFL), -VALUE_INFINITE);
685 // Collect info about search result
686 bestMove = Rml[0].pv[0];
687 bestValues[depth] = value;
688 bestMoveChanges[depth] = Rml.bestMoveChanges;
691 LogFile << pretty_pv(pos, depth, value, current_search_time(), Rml[0].pv) << endl;
693 // Init easyMove after first iteration or drop if differs from the best move
694 if (depth == 1 && (Rml.size() == 1 || Rml[0].pv_score > Rml[1].pv_score + EasyMoveMargin))
696 else if (bestMove != easyMove)
697 easyMove = MOVE_NONE;
699 if (UseTimeManagement && !StopRequest)
702 bool noMoreTime = false;
704 // Stop search early when the last two iterations returned a mate score
706 && abs(bestValues[depth]) >= abs(VALUE_MATE) - 100
707 && abs(bestValues[depth - 1]) >= abs(VALUE_MATE) - 100)
710 // Stop search early if one move seems to be much better than the
711 // others or if there is only a single legal move. In this latter
712 // case we search up to Iteration 8 anyway to get a proper score.
714 && easyMove == bestMove
716 ||( Rml[0].nodes > (pos.nodes_searched() * 85) / 100
717 && current_search_time() > TimeMgr.available_time() / 16)
718 ||( Rml[0].nodes > (pos.nodes_searched() * 98) / 100
719 && current_search_time() > TimeMgr.available_time() / 32)))
722 // Add some extra time if the best move has changed during the last two iterations
723 if (depth > 4 && depth < 50)
724 TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth-1]);
726 // Stop search if most of MaxSearchTime is consumed at the end of the
727 // iteration. We probably don't have enough time to search the first
728 // move at the next iteration anyway.
729 if (current_search_time() > (TimeMgr.available_time() * 80) / 128)
735 StopOnPonderhit = true;
742 *ponderMove = Rml[0].pv[1];
747 // search<>() is the main search function for both PV and non-PV nodes and for
748 // normal and SplitPoint nodes. When called just after a split point the search
749 // is simpler because we have already probed the hash table, done a null move
750 // search, and searched the first move before splitting, we don't have to repeat
751 // all this work again. We also don't need to store anything to the hash table
752 // here: This is taken care of after we return from the split point.
754 template <NodeType PvNode, bool SpNode, bool Root>
755 Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
757 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
758 assert(beta > alpha && beta <= VALUE_INFINITE);
759 assert(PvNode || alpha == beta - 1);
760 assert((Root || ply > 0) && ply < PLY_MAX);
761 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
763 Move movesSearched[MOVES_MAX];
768 Move ttMove, move, excludedMove, threatMove;
771 Value bestValue, value, oldAlpha;
772 Value refinedValue, nullValue, futilityBase, futilityValueScaled; // Non-PV specific
773 bool isPvMove, isCheck, singularExtensionNode, moveIsCheck, captureOrPromotion, dangerous;
774 bool mateThreat = false;
775 int moveCount = 0, playedMoveCount = 0;
776 int threadID = pos.thread();
777 SplitPoint* sp = NULL;
779 refinedValue = bestValue = value = -VALUE_INFINITE;
781 isCheck = pos.is_check();
787 ttMove = excludedMove = MOVE_NONE;
788 threatMove = sp->threatMove;
789 mateThreat = sp->mateThreat;
790 goto split_point_start;
795 // Step 1. Initialize node and poll. Polling can abort search
796 ss->currentMove = ss->bestMove = threatMove = (ss+1)->excludedMove = MOVE_NONE;
797 (ss+1)->skipNullMove = false; (ss+1)->reduction = DEPTH_ZERO;
798 (ss+2)->killers[0] = (ss+2)->killers[1] = (ss+2)->mateKiller = MOVE_NONE;
800 if (threadID == 0 && ++NodesSincePoll > NodesBetweenPolls)
806 // Step 2. Check for aborted search and immediate draw
808 || ThreadsMgr.cutoff_at_splitpoint(threadID)
810 || ply >= PLY_MAX - 1) && !Root)
813 // Step 3. Mate distance pruning
814 alpha = Max(value_mated_in(ply), alpha);
815 beta = Min(value_mate_in(ply+1), beta);
819 // Step 4. Transposition table lookup
820 // We don't want the score of a partial search to overwrite a previous full search
821 // TT value, so we use a different position key in case of an excluded move.
822 excludedMove = ss->excludedMove;
823 posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
825 tte = TT.retrieve(posKey);
826 ttMove = tte ? tte->move() : MOVE_NONE;
828 // At PV nodes we check for exact scores, while at non-PV nodes we check for
829 // and return a fail high/low. Biggest advantage at probing at PV nodes is
830 // to have a smooth experience in analysis mode.
833 && (PvNode ? tte->depth() >= depth && tte->type() == VALUE_TYPE_EXACT
834 : ok_to_use_TT(tte, depth, beta, ply)))
837 ss->bestMove = ttMove; // Can be MOVE_NONE
838 return value_from_tt(tte->value(), ply);
841 // Step 5. Evaluate the position statically and
842 // update gain statistics of parent move.
844 ss->eval = ss->evalMargin = VALUE_NONE;
847 assert(tte->static_value() != VALUE_NONE);
849 ss->eval = tte->static_value();
850 ss->evalMargin = tte->static_value_margin();
851 refinedValue = refine_eval(tte, ss->eval, ply);
855 refinedValue = ss->eval = evaluate(pos, ss->evalMargin);
856 TT.store(posKey, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, MOVE_NONE, ss->eval, ss->evalMargin);
859 // Save gain for the parent non-capture move
860 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
862 // Step 6. Razoring (is omitted in PV nodes)
864 && depth < RazorDepth
866 && refinedValue < beta - razor_margin(depth)
867 && ttMove == MOVE_NONE
868 && !value_is_mate(beta)
869 && !pos.has_pawn_on_7th(pos.side_to_move()))
871 Value rbeta = beta - razor_margin(depth);
872 Value v = qsearch<NonPV>(pos, ss, rbeta-1, rbeta, DEPTH_ZERO, ply);
874 // Logically we should return (v + razor_margin(depth)), but
875 // surprisingly this did slightly weaker in tests.
879 // Step 7. Static null move pruning (is omitted in PV nodes)
880 // We're betting that the opponent doesn't have a move that will reduce
881 // the score by more than futility_margin(depth) if we do a null move.
884 && depth < RazorDepth
886 && refinedValue >= beta + futility_margin(depth, 0)
887 && !value_is_mate(beta)
888 && pos.non_pawn_material(pos.side_to_move()))
889 return refinedValue - futility_margin(depth, 0);
891 // Step 8. Null move search with verification search (is omitted in PV nodes)
896 && refinedValue >= beta
897 && !value_is_mate(beta)
898 && pos.non_pawn_material(pos.side_to_move()))
900 ss->currentMove = MOVE_NULL;
902 // Null move dynamic reduction based on depth
903 int R = 3 + (depth >= 5 * ONE_PLY ? depth / 8 : 0);
905 // Null move dynamic reduction based on value
906 if (refinedValue - beta > PawnValueMidgame)
909 pos.do_null_move(st);
910 (ss+1)->skipNullMove = true;
911 nullValue = -search<NonPV>(pos, ss+1, -beta, -alpha, depth-R*ONE_PLY, ply+1);
912 (ss+1)->skipNullMove = false;
913 pos.undo_null_move();
915 if (nullValue >= beta)
917 // Do not return unproven mate scores
918 if (nullValue >= value_mate_in(PLY_MAX))
921 if (depth < 6 * ONE_PLY)
924 // Do verification search at high depths
925 ss->skipNullMove = true;
926 Value v = search<NonPV>(pos, ss, alpha, beta, depth-R*ONE_PLY, ply);
927 ss->skipNullMove = false;
934 // The null move failed low, which means that we may be faced with
935 // some kind of threat. If the previous move was reduced, check if
936 // the move that refuted the null move was somehow connected to the
937 // move which was reduced. If a connection is found, return a fail
938 // low score (which will cause the reduced move to fail high in the
939 // parent node, which will trigger a re-search with full depth).
940 if (nullValue == value_mated_in(ply + 2))
943 threatMove = (ss+1)->bestMove;
944 if ( depth < ThreatDepth
946 && threatMove != MOVE_NONE
947 && connected_moves(pos, (ss-1)->currentMove, threatMove))
952 // Step 9. Internal iterative deepening
953 if ( depth >= IIDDepth[PvNode]
954 && ttMove == MOVE_NONE
955 && (PvNode || (!isCheck && ss->eval >= beta - IIDMargin)))
957 Depth d = (PvNode ? depth - 2 * ONE_PLY : depth / 2);
959 ss->skipNullMove = true;
960 search<PvNode>(pos, ss, alpha, beta, d, ply);
961 ss->skipNullMove = false;
963 ttMove = ss->bestMove;
964 tte = TT.retrieve(posKey);
967 // Expensive mate threat detection (only for PV nodes)
969 mateThreat = pos.has_mate_threat();
971 split_point_start: // At split points actual search starts from here
973 // Initialize a MovePicker object for the current position
974 MovePickerExt<SpNode, Root> mp(pos, ttMove, depth, H, ss, (PvNode ? -VALUE_INFINITE : beta));
976 ss->bestMove = MOVE_NONE;
977 futilityBase = ss->eval + ss->evalMargin;
978 singularExtensionNode = !Root
980 && depth >= SingularExtensionDepth[PvNode]
983 && !excludedMove // Do not allow recursive singular extension search
984 && (tte->type() & VALUE_TYPE_LOWER)
985 && tte->depth() >= depth - 3 * ONE_PLY;
988 lock_grab(&(sp->lock));
989 bestValue = sp->bestValue;
992 // Step 10. Loop through moves
993 // Loop through all legal moves until no moves remain or a beta cutoff occurs
994 while ( bestValue < beta
995 && (move = mp.get_next_move()) != MOVE_NONE
996 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
998 assert(move_is_ok(move));
1002 moveCount = ++sp->moveCount;
1003 lock_release(&(sp->lock));
1005 else if (move == excludedMove)
1012 // This is used by time management
1013 FirstRootMove = (moveCount == 1);
1015 // Save the current node count before the move is searched
1016 nodes = pos.nodes_searched();
1018 // If it's time to send nodes info, do it here where we have the
1019 // correct accumulated node counts searched by each thread.
1020 if (SendSearchedNodes)
1022 SendSearchedNodes = false;
1023 cout << "info" << speed_to_uci(pos.nodes_searched()) << endl;
1026 if (current_search_time() >= 1000)
1027 cout << "info currmove " << move
1028 << " currmovenumber " << moveCount << endl;
1031 // At Root and at first iteration do a PV search on all the moves
1032 // to score root moves. Otherwise only the first one is the PV.
1033 isPvMove = (PvNode && moveCount <= (Root ? MultiPV + 1000 * (depth <= ONE_PLY) : 1));
1034 moveIsCheck = pos.move_is_check(move, ci);
1035 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1037 // Step 11. Decide the new search depth
1038 ext = extension<PvNode>(pos, move, captureOrPromotion, moveIsCheck, mateThreat, &dangerous);
1040 // Singular extension search. If all moves but one fail low on a search of (alpha-s, beta-s),
1041 // and just one fails high on (alpha, beta), then that move is singular and should be extended.
1042 // To verify this we do a reduced search on all the other moves but the ttMove, if result is
1043 // lower than ttValue minus a margin then we extend ttMove.
1044 if ( singularExtensionNode
1045 && move == tte->move()
1048 Value ttValue = value_from_tt(tte->value(), ply);
1050 if (abs(ttValue) < VALUE_KNOWN_WIN)
1052 Value b = ttValue - depth;
1053 ss->excludedMove = move;
1054 ss->skipNullMove = true;
1055 Value v = search<NonPV>(pos, ss, b - 1, b, depth / 2, ply);
1056 ss->skipNullMove = false;
1057 ss->excludedMove = MOVE_NONE;
1058 ss->bestMove = MOVE_NONE;
1064 // Update current move (this must be done after singular extension search)
1065 ss->currentMove = move;
1066 newDepth = depth - ONE_PLY + ext;
1068 // Step 12. Futility pruning (is omitted in PV nodes)
1070 && !captureOrPromotion
1074 && !move_is_castle(move))
1076 // Move count based pruning
1077 if ( moveCount >= futility_move_count(depth)
1078 && !(threatMove && connected_threat(pos, move, threatMove))
1079 && bestValue > value_mated_in(PLY_MAX)) // FIXME bestValue is racy
1082 lock_grab(&(sp->lock));
1087 // Value based pruning
1088 // We illogically ignore reduction condition depth >= 3*ONE_PLY for predicted depth,
1089 // but fixing this made program slightly weaker.
1090 Depth predictedDepth = newDepth - reduction<NonPV>(depth, moveCount);
1091 futilityValueScaled = futilityBase + futility_margin(predictedDepth, moveCount)
1092 + H.gain(pos.piece_on(move_from(move)), move_to(move));
1094 if (futilityValueScaled < beta)
1098 lock_grab(&(sp->lock));
1099 if (futilityValueScaled > sp->bestValue)
1100 sp->bestValue = bestValue = futilityValueScaled;
1102 else if (futilityValueScaled > bestValue)
1103 bestValue = futilityValueScaled;
1108 // Prune moves with negative SEE at low depths
1109 if ( predictedDepth < 2 * ONE_PLY
1110 && bestValue > value_mated_in(PLY_MAX)
1111 && pos.see_sign(move) < 0)
1114 lock_grab(&(sp->lock));
1120 // Step 13. Make the move
1121 pos.do_move(move, st, ci, moveIsCheck);
1123 if (!SpNode && !captureOrPromotion)
1124 movesSearched[playedMoveCount++] = move;
1126 // Step extra. pv search (only in PV nodes)
1127 // The first move in list is the expected PV
1130 // Aspiration window is disabled in multi-pv case
1131 if (Root && MultiPV > 1)
1132 alpha = -VALUE_INFINITE;
1134 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1138 // Step 14. Reduced depth search
1139 // If the move fails high will be re-searched at full depth.
1140 bool doFullDepthSearch = true;
1142 if ( depth >= 3 * ONE_PLY
1143 && !captureOrPromotion
1145 && !move_is_castle(move)
1146 && ss->killers[0] != move
1147 && ss->killers[1] != move)
1149 ss->reduction = reduction<PvNode>(depth, moveCount);
1152 alpha = SpNode ? sp->alpha : alpha;
1153 Depth d = newDepth - ss->reduction;
1154 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, ply+1);
1156 doFullDepthSearch = (value > alpha);
1158 ss->reduction = DEPTH_ZERO; // Restore original reduction
1161 // Step 15. Full depth search
1162 if (doFullDepthSearch)
1164 alpha = SpNode ? sp->alpha : alpha;
1165 value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, ply+1);
1167 // Step extra. pv search (only in PV nodes)
1168 // Search only for possible new PV nodes, if instead value >= beta then
1169 // parent node fails low with value <= alpha and tries another move.
1170 if (PvNode && value > alpha && (Root || value < beta))
1171 value = -search<PV>(pos, ss+1, -beta, -alpha, newDepth, ply+1);
1175 // Step 16. Undo move
1176 pos.undo_move(move);
1178 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1180 // Step 17. Check for new best move
1183 lock_grab(&(sp->lock));
1184 bestValue = sp->bestValue;
1188 if (value > bestValue && !(SpNode && ThreadsMgr.cutoff_at_splitpoint(threadID)))
1193 sp->bestValue = value;
1195 if (!Root && value > alpha)
1197 if (PvNode && value < beta) // We want always alpha < beta
1205 sp->betaCutoff = true;
1207 if (value == value_mate_in(ply + 1))
1208 ss->mateKiller = move;
1210 ss->bestMove = move;
1213 sp->ss->bestMove = move;
1219 // Finished searching the move. If StopRequest is true, the search
1220 // was aborted because the user interrupted the search or because we
1221 // ran out of time. In this case, the return value of the search cannot
1222 // be trusted, and we break out of the loop without updating the best
1227 // Remember searched nodes counts for this move
1228 mp.rm->nodes += pos.nodes_searched() - nodes;
1230 // PV move or new best move ?
1231 if (isPvMove || value > alpha)
1234 ss->bestMove = move;
1235 mp.rm->pv_score = value;
1236 mp.rm->extract_pv_from_tt(pos);
1238 // We record how often the best move has been changed in each
1239 // iteration. This information is used for time management: When
1240 // the best move changes frequently, we allocate some more time.
1241 if (!isPvMove && MultiPV == 1)
1242 Rml.bestMoveChanges++;
1244 Rml.sort_multipv(moveCount);
1246 // Update alpha. In multi-pv we don't use aspiration window, so
1247 // set alpha equal to minimum score among the PV lines.
1249 alpha = Rml[Min(moveCount, MultiPV) - 1].pv_score; // FIXME why moveCount?
1250 else if (value > alpha)
1254 mp.rm->pv_score = -VALUE_INFINITE;
1258 // Step 18. Check for split
1261 && depth >= ThreadsMgr.min_split_depth()
1262 && ThreadsMgr.active_threads() > 1
1264 && ThreadsMgr.available_thread_exists(threadID)
1266 && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1267 ThreadsMgr.split<FakeSplit>(pos, ss, ply, &alpha, beta, &bestValue, depth,
1268 threatMove, mateThreat, moveCount, &mp, PvNode);
1271 // Step 19. Check for mate and stalemate
1272 // All legal moves have been searched and if there are
1273 // no legal moves, it must be mate or stalemate.
1274 // If one move was excluded return fail low score.
1275 if (!SpNode && !moveCount)
1276 return excludedMove ? oldAlpha : isCheck ? value_mated_in(ply) : VALUE_DRAW;
1278 // Step 20. Update tables
1279 // If the search is not aborted, update the transposition table,
1280 // history counters, and killer moves.
1281 if (!SpNode && !StopRequest && !ThreadsMgr.cutoff_at_splitpoint(threadID))
1283 move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove;
1284 vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER
1285 : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT;
1287 TT.store(posKey, value_to_tt(bestValue, ply), vt, depth, move, ss->eval, ss->evalMargin);
1289 // Update killers and history only for non capture moves that fails high
1290 if ( bestValue >= beta
1291 && !pos.move_is_capture_or_promotion(move))
1293 update_history(pos, move, depth, movesSearched, playedMoveCount);
1294 update_killers(move, ss->killers);
1300 // Here we have the lock still grabbed
1301 sp->slaves[threadID] = 0;
1302 sp->nodes += pos.nodes_searched();
1303 lock_release(&(sp->lock));
1306 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1311 // qsearch() is the quiescence search function, which is called by the main
1312 // search function when the remaining depth is zero (or, to be more precise,
1313 // less than ONE_PLY).
1315 template <NodeType PvNode>
1316 Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth, int ply) {
1318 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1319 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1320 assert(PvNode || alpha == beta - 1);
1322 assert(ply > 0 && ply < PLY_MAX);
1323 assert(pos.thread() >= 0 && pos.thread() < ThreadsMgr.active_threads());
1327 Value bestValue, value, evalMargin, futilityValue, futilityBase;
1328 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1331 Value oldAlpha = alpha;
1333 ss->bestMove = ss->currentMove = MOVE_NONE;
1335 // Check for an instant draw or maximum ply reached
1336 if (pos.is_draw() || ply >= PLY_MAX - 1)
1339 // Decide whether or not to include checks, this fixes also the type of
1340 // TT entry depth that we are going to use. Note that in qsearch we use
1341 // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
1342 isCheck = pos.is_check();
1343 ttDepth = (isCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS);
1345 // Transposition table lookup. At PV nodes, we don't use the TT for
1346 // pruning, but only for move ordering.
1347 tte = TT.retrieve(pos.get_key());
1348 ttMove = (tte ? tte->move() : MOVE_NONE);
1350 if (!PvNode && tte && ok_to_use_TT(tte, ttDepth, beta, ply))
1352 ss->bestMove = ttMove; // Can be MOVE_NONE
1353 return value_from_tt(tte->value(), ply);
1356 // Evaluate the position statically
1359 bestValue = futilityBase = -VALUE_INFINITE;
1360 ss->eval = evalMargin = VALUE_NONE;
1361 enoughMaterial = false;
1367 assert(tte->static_value() != VALUE_NONE);
1369 evalMargin = tte->static_value_margin();
1370 ss->eval = bestValue = tte->static_value();
1373 ss->eval = bestValue = evaluate(pos, evalMargin);
1375 update_gains(pos, (ss-1)->currentMove, (ss-1)->eval, ss->eval);
1377 // Stand pat. Return immediately if static value is at least beta
1378 if (bestValue >= beta)
1381 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, DEPTH_NONE, MOVE_NONE, ss->eval, evalMargin);
1386 if (PvNode && bestValue > alpha)
1389 // Futility pruning parameters, not needed when in check
1390 futilityBase = ss->eval + evalMargin + FutilityMarginQS;
1391 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1394 // Initialize a MovePicker object for the current position, and prepare
1395 // to search the moves. Because the depth is <= 0 here, only captures,
1396 // queen promotions and checks (only if depth >= DEPTH_QS_CHECKS) will
1398 MovePicker mp(pos, ttMove, depth, H);
1401 // Loop through the moves until no moves remain or a beta cutoff occurs
1402 while ( alpha < beta
1403 && (move = mp.get_next_move()) != MOVE_NONE)
1405 assert(move_is_ok(move));
1407 moveIsCheck = pos.move_is_check(move, ci);
1415 && !move_is_promotion(move)
1416 && !pos.move_is_passed_pawn_push(move))
1418 futilityValue = futilityBase
1419 + pos.endgame_value_of_piece_on(move_to(move))
1420 + (move_is_ep(move) ? PawnValueEndgame : VALUE_ZERO);
1422 if (futilityValue < alpha)
1424 if (futilityValue > bestValue)
1425 bestValue = futilityValue;
1429 // Prune moves with negative or equal SEE
1430 if ( futilityBase < beta
1431 && depth < DEPTH_ZERO
1432 && pos.see(move) <= 0)
1436 // Detect non-capture evasions that are candidate to be pruned
1437 evasionPrunable = isCheck
1438 && bestValue > value_mated_in(PLY_MAX)
1439 && !pos.move_is_capture(move)
1440 && !pos.can_castle(pos.side_to_move());
1442 // Don't search moves with negative SEE values
1444 && (!isCheck || evasionPrunable)
1446 && !move_is_promotion(move)
1447 && pos.see_sign(move) < 0)
1450 // Don't search useless checks
1455 && !pos.move_is_capture_or_promotion(move)
1456 && ss->eval + PawnValueMidgame / 4 < beta
1457 && !check_is_dangerous(pos, move, futilityBase, beta, &bestValue))
1459 if (ss->eval + PawnValueMidgame / 4 > bestValue)
1460 bestValue = ss->eval + PawnValueMidgame / 4;
1465 // Update current move
1466 ss->currentMove = move;
1468 // Make and search the move
1469 pos.do_move(move, st, ci, moveIsCheck);
1470 value = -qsearch<PvNode>(pos, ss+1, -beta, -alpha, depth-ONE_PLY, ply+1);
1471 pos.undo_move(move);
1473 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1476 if (value > bestValue)
1482 ss->bestMove = move;
1487 // All legal moves have been searched. A special case: If we're in check
1488 // and no legal moves were found, it is checkmate.
1489 if (isCheck && bestValue == -VALUE_INFINITE)
1490 return value_mated_in(ply);
1492 // Update transposition table
1493 ValueType vt = (bestValue <= oldAlpha ? VALUE_TYPE_UPPER : bestValue >= beta ? VALUE_TYPE_LOWER : VALUE_TYPE_EXACT);
1494 TT.store(pos.get_key(), value_to_tt(bestValue, ply), vt, ttDepth, ss->bestMove, ss->eval, evalMargin);
1496 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1502 // check_is_dangerous() tests if a checking move can be pruned in qsearch().
1503 // bestValue is updated only when returning false because in that case move
1506 bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bestValue)
1508 Bitboard b, occ, oldAtt, newAtt, kingAtt;
1509 Square from, to, ksq, victimSq;
1512 Value futilityValue, bv = *bestValue;
1514 from = move_from(move);
1516 them = opposite_color(pos.side_to_move());
1517 ksq = pos.king_square(them);
1518 kingAtt = pos.attacks_from<KING>(ksq);
1519 pc = pos.piece_on(from);
1521 occ = pos.occupied_squares() & ~(1ULL << from) & ~(1ULL << ksq);
1522 oldAtt = pos.attacks_from(pc, from, occ);
1523 newAtt = pos.attacks_from(pc, to, occ);
1525 // Rule 1. Checks which give opponent's king at most one escape square are dangerous
1526 b = kingAtt & ~pos.pieces_of_color(them) & ~newAtt & ~(1ULL << to);
1528 if (!(b && (b & (b - 1))))
1531 // Rule 2. Queen contact check is very dangerous
1532 if ( type_of_piece(pc) == QUEEN
1533 && bit_is_set(kingAtt, to))
1536 // Rule 3. Creating new double threats with checks
1537 b = pos.pieces_of_color(them) & newAtt & ~oldAtt & ~(1ULL << ksq);
1541 victimSq = pop_1st_bit(&b);
1542 futilityValue = futilityBase + pos.endgame_value_of_piece_on(victimSq);
1544 // Note that here we generate illegal "double move"!
1545 if ( futilityValue >= beta
1546 && pos.see_sign(make_move(from, victimSq)) >= 0)
1549 if (futilityValue > bv)
1553 // Update bestValue only if check is not dangerous (because we will prune the move)
1559 // connected_moves() tests whether two moves are 'connected' in the sense
1560 // that the first move somehow made the second move possible (for instance
1561 // if the moving piece is the same in both moves). The first move is assumed
1562 // to be the move that was made to reach the current position, while the
1563 // second move is assumed to be a move from the current position.
1565 bool connected_moves(const Position& pos, Move m1, Move m2) {
1567 Square f1, t1, f2, t2;
1570 assert(m1 && move_is_ok(m1));
1571 assert(m2 && move_is_ok(m2));
1573 // Case 1: The moving piece is the same in both moves
1579 // Case 2: The destination square for m2 was vacated by m1
1585 // Case 3: Moving through the vacated square
1586 if ( piece_is_slider(pos.piece_on(f2))
1587 && bit_is_set(squares_between(f2, t2), f1))
1590 // Case 4: The destination square for m2 is defended by the moving piece in m1
1591 p = pos.piece_on(t1);
1592 if (bit_is_set(pos.attacks_from(p, t1), t2))
1595 // Case 5: Discovered check, checking piece is the piece moved in m1
1596 if ( piece_is_slider(p)
1597 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
1598 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
1600 // discovered_check_candidates() works also if the Position's side to
1601 // move is the opposite of the checking piece.
1602 Color them = opposite_color(pos.side_to_move());
1603 Bitboard dcCandidates = pos.discovered_check_candidates(them);
1605 if (bit_is_set(dcCandidates, f2))
1612 // value_is_mate() checks if the given value is a mate one eventually
1613 // compensated for the ply.
1615 bool value_is_mate(Value value) {
1617 assert(abs(value) <= VALUE_INFINITE);
1619 return value <= value_mated_in(PLY_MAX)
1620 || value >= value_mate_in(PLY_MAX);
1624 // value_to_tt() adjusts a mate score from "plies to mate from the root" to
1625 // "plies to mate from the current ply". Non-mate scores are unchanged.
1626 // The function is called before storing a value to the transposition table.
1628 Value value_to_tt(Value v, int ply) {
1630 if (v >= value_mate_in(PLY_MAX))
1633 if (v <= value_mated_in(PLY_MAX))
1640 // value_from_tt() is the inverse of value_to_tt(): It adjusts a mate score from
1641 // the transposition table to a mate score corrected for the current ply.
1643 Value value_from_tt(Value v, int ply) {
1645 if (v >= value_mate_in(PLY_MAX))
1648 if (v <= value_mated_in(PLY_MAX))
1655 // extension() decides whether a move should be searched with normal depth,
1656 // or with extended depth. Certain classes of moves (checking moves, in
1657 // particular) are searched with bigger depth than ordinary moves and in
1658 // any case are marked as 'dangerous'. Note that also if a move is not
1659 // extended, as example because the corresponding UCI option is set to zero,
1660 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
1661 template <NodeType PvNode>
1662 Depth extension(const Position& pos, Move m, bool captureOrPromotion,
1663 bool moveIsCheck, bool mateThreat, bool* dangerous) {
1665 assert(m != MOVE_NONE);
1667 Depth result = DEPTH_ZERO;
1668 *dangerous = moveIsCheck | mateThreat;
1672 if (moveIsCheck && pos.see_sign(m) >= 0)
1673 result += CheckExtension[PvNode];
1676 result += MateThreatExtension[PvNode];
1679 if (pos.type_of_piece_on(move_from(m)) == PAWN)
1681 Color c = pos.side_to_move();
1682 if (relative_rank(c, move_to(m)) == RANK_7)
1684 result += PawnPushTo7thExtension[PvNode];
1687 if (pos.pawn_is_passed(c, move_to(m)))
1689 result += PassedPawnExtension[PvNode];
1694 if ( captureOrPromotion
1695 && pos.type_of_piece_on(move_to(m)) != PAWN
1696 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1697 - pos.midgame_value_of_piece_on(move_to(m)) == VALUE_ZERO)
1698 && !move_is_promotion(m)
1701 result += PawnEndgameExtension[PvNode];
1706 && captureOrPromotion
1707 && pos.type_of_piece_on(move_to(m)) != PAWN
1708 && pos.see_sign(m) >= 0)
1710 result += ONE_PLY / 2;
1714 return Min(result, ONE_PLY);
1718 // connected_threat() tests whether it is safe to forward prune a move or if
1719 // is somehow connected to the threat move returned by null search.
1721 bool connected_threat(const Position& pos, Move m, Move threat) {
1723 assert(move_is_ok(m));
1724 assert(threat && move_is_ok(threat));
1725 assert(!pos.move_is_check(m));
1726 assert(!pos.move_is_capture_or_promotion(m));
1727 assert(!pos.move_is_passed_pawn_push(m));
1729 Square mfrom, mto, tfrom, tto;
1731 mfrom = move_from(m);
1733 tfrom = move_from(threat);
1734 tto = move_to(threat);
1736 // Case 1: Don't prune moves which move the threatened piece
1740 // Case 2: If the threatened piece has value less than or equal to the
1741 // value of the threatening piece, don't prune moves which defend it.
1742 if ( pos.move_is_capture(threat)
1743 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
1744 || pos.type_of_piece_on(tfrom) == KING)
1745 && pos.move_attacks_square(m, tto))
1748 // Case 3: If the moving piece in the threatened move is a slider, don't
1749 // prune safe moves which block its ray.
1750 if ( piece_is_slider(pos.piece_on(tfrom))
1751 && bit_is_set(squares_between(tfrom, tto), mto)
1752 && pos.see_sign(m) >= 0)
1759 // ok_to_use_TT() returns true if a transposition table score
1760 // can be used at a given point in search.
1762 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
1764 Value v = value_from_tt(tte->value(), ply);
1766 return ( tte->depth() >= depth
1767 || v >= Max(value_mate_in(PLY_MAX), beta)
1768 || v < Min(value_mated_in(PLY_MAX), beta))
1770 && ( ((tte->type() & VALUE_TYPE_LOWER) && v >= beta)
1771 || ((tte->type() & VALUE_TYPE_UPPER) && v < beta));
1775 // refine_eval() returns the transposition table score if
1776 // possible otherwise falls back on static position evaluation.
1778 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
1782 Value v = value_from_tt(tte->value(), ply);
1784 if ( ((tte->type() & VALUE_TYPE_LOWER) && v >= defaultEval)
1785 || ((tte->type() & VALUE_TYPE_UPPER) && v < defaultEval))
1792 // update_history() registers a good move that produced a beta-cutoff
1793 // in history and marks as failures all the other moves of that ply.
1795 void update_history(const Position& pos, Move move, Depth depth,
1796 Move movesSearched[], int moveCount) {
1798 Value bonus = Value(int(depth) * int(depth));
1800 H.update(pos.piece_on(move_from(move)), move_to(move), bonus);
1802 for (int i = 0; i < moveCount - 1; i++)
1804 m = movesSearched[i];
1808 H.update(pos.piece_on(move_from(m)), move_to(m), -bonus);
1813 // update_killers() add a good move that produced a beta-cutoff
1814 // among the killer moves of that ply.
1816 void update_killers(Move m, Move killers[]) {
1818 if (m != killers[0])
1820 killers[1] = killers[0];
1826 // update_gains() updates the gains table of a non-capture move given
1827 // the static position evaluation before and after the move.
1829 void update_gains(const Position& pos, Move m, Value before, Value after) {
1832 && before != VALUE_NONE
1833 && after != VALUE_NONE
1834 && pos.captured_piece_type() == PIECE_TYPE_NONE
1835 && !move_is_special(m))
1836 H.update_gain(pos.piece_on(move_to(m)), move_to(m), -(before + after));
1839 // current_search_time() returns the number of milliseconds which have passed
1840 // since the beginning of the current search.
1842 int current_search_time() {
1844 return get_system_time() - SearchStartTime;
1848 // value_to_uci() converts a value to a string suitable for use with the UCI
1849 // protocol specifications:
1851 // cp <x> The score from the engine's point of view in centipawns.
1852 // mate <y> Mate in y moves, not plies. If the engine is getting mated
1853 // use negative values for y.
1855 std::string value_to_uci(Value v) {
1857 std::stringstream s;
1859 if (abs(v) < VALUE_MATE - PLY_MAX * ONE_PLY)
1860 s << "cp " << int(v) * 100 / int(PawnValueMidgame); // Scale to centipawns
1862 s << "mate " << (v > 0 ? (VALUE_MATE - v + 1) / 2 : -(VALUE_MATE + v) / 2);
1868 // speed_to_uci() returns a string with time stats of current search suitable
1869 // to be sent to UCI gui.
1871 std::string speed_to_uci(int64_t nodes) {
1873 std::stringstream s;
1874 int t = current_search_time();
1876 s << " nodes " << nodes
1877 << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0)
1884 // poll() performs two different functions: It polls for user input, and it
1885 // looks at the time consumed so far and decides if it's time to abort the
1888 void poll(const Position& pos) {
1890 static int lastInfoTime;
1891 int t = current_search_time();
1894 if (input_available())
1896 // We are line oriented, don't read single chars
1897 std::string command;
1899 if (!std::getline(std::cin, command))
1902 if (command == "quit")
1904 // Quit the program as soon as possible
1906 QuitRequest = StopRequest = true;
1909 else if (command == "stop")
1911 // Stop calculating as soon as possible, but still send the "bestmove"
1912 // and possibly the "ponder" token when finishing the search.
1916 else if (command == "ponderhit")
1918 // The opponent has played the expected move. GUI sends "ponderhit" if
1919 // we were told to ponder on the same move the opponent has played. We
1920 // should continue searching but switching from pondering to normal search.
1923 if (StopOnPonderhit)
1928 // Print search information
1932 else if (lastInfoTime > t)
1933 // HACK: Must be a new search where we searched less than
1934 // NodesBetweenPolls nodes during the first second of search.
1937 else if (t - lastInfoTime >= 1000)
1944 if (dbg_show_hit_rate)
1945 dbg_print_hit_rate();
1947 // Send info on searched nodes as soon as we return to root
1948 SendSearchedNodes = true;
1951 // Should we stop the search?
1955 bool stillAtFirstMove = FirstRootMove
1956 && !AspirationFailLow
1957 && t > TimeMgr.available_time();
1959 bool noMoreTime = t > TimeMgr.maximum_time()
1960 || stillAtFirstMove;
1962 if ( (UseTimeManagement && noMoreTime)
1963 || (ExactMaxTime && t >= ExactMaxTime)
1964 || (MaxNodes && pos.nodes_searched() >= MaxNodes)) // FIXME
1969 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
1970 // while the program is pondering. The point is to work around a wrinkle in
1971 // the UCI protocol: When pondering, the engine is not allowed to give a
1972 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
1973 // We simply wait here until one of these commands is sent, and return,
1974 // after which the bestmove and pondermove will be printed.
1976 void wait_for_stop_or_ponderhit() {
1978 std::string command;
1982 // Wait for a command from stdin
1983 if (!std::getline(std::cin, command))
1986 if (command == "quit")
1991 else if (command == "ponderhit" || command == "stop")
1997 // init_thread() is the function which is called when a new thread is
1998 // launched. It simply calls the idle_loop() function with the supplied
1999 // threadID. There are two versions of this function; one for POSIX
2000 // threads and one for Windows threads.
2002 #if !defined(_MSC_VER)
2004 void* init_thread(void* threadID) {
2006 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2012 DWORD WINAPI init_thread(LPVOID threadID) {
2014 ThreadsMgr.idle_loop(*(int*)threadID, NULL);
2021 /// The ThreadsManager class
2024 // read_uci_options() updates number of active threads and other internal
2025 // parameters according to the UCI options values. It is called before
2026 // to start a new search.
2028 void ThreadsManager::read_uci_options() {
2030 maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
2031 minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
2032 useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
2033 activeThreads = Options["Threads"].value<int>();
2037 // idle_loop() is where the threads are parked when they have no work to do.
2038 // The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint
2039 // object for which the current thread is the master.
2041 void ThreadsManager::idle_loop(int threadID, SplitPoint* sp) {
2043 assert(threadID >= 0 && threadID < MAX_THREADS);
2046 bool allFinished = false;
2050 // Slave threads can exit as soon as AllThreadsShouldExit raises,
2051 // master should exit as last one.
2052 if (allThreadsShouldExit)
2055 threads[threadID].state = THREAD_TERMINATED;
2059 // If we are not thinking, wait for a condition to be signaled
2060 // instead of wasting CPU time polling for work.
2061 while ( threadID >= activeThreads || threads[threadID].state == THREAD_INITIALIZING
2062 || (useSleepingThreads && threads[threadID].state == THREAD_AVAILABLE))
2064 assert(!sp || useSleepingThreads);
2065 assert(threadID != 0 || useSleepingThreads);
2067 if (threads[threadID].state == THREAD_INITIALIZING)
2068 threads[threadID].state = THREAD_AVAILABLE;
2070 // Grab the lock to avoid races with wake_sleeping_thread()
2071 lock_grab(&sleepLock[threadID]);
2073 // If we are master and all slaves have finished do not go to sleep
2074 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2075 allFinished = (i == activeThreads);
2077 if (allFinished || allThreadsShouldExit)
2079 lock_release(&sleepLock[threadID]);
2083 // Do sleep here after retesting sleep conditions
2084 if (threadID >= activeThreads || threads[threadID].state == THREAD_AVAILABLE)
2085 cond_wait(&sleepCond[threadID], &sleepLock[threadID]);
2087 lock_release(&sleepLock[threadID]);
2090 // If this thread has been assigned work, launch a search
2091 if (threads[threadID].state == THREAD_WORKISWAITING)
2093 assert(!allThreadsShouldExit);
2095 threads[threadID].state = THREAD_SEARCHING;
2097 // Copy SplitPoint position and search stack and call search()
2098 // with SplitPoint template parameter set to true.
2099 SearchStack ss[PLY_MAX_PLUS_2];
2100 SplitPoint* tsp = threads[threadID].splitPoint;
2101 Position pos(*tsp->pos, threadID);
2103 memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack));
2107 search<PV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2109 search<NonPV, true, false>(pos, ss+1, tsp->alpha, tsp->beta, tsp->depth, tsp->ply);
2111 assert(threads[threadID].state == THREAD_SEARCHING);
2113 threads[threadID].state = THREAD_AVAILABLE;
2115 // Wake up master thread so to allow it to return from the idle loop in
2116 // case we are the last slave of the split point.
2117 if (useSleepingThreads && threadID != tsp->master && threads[tsp->master].state == THREAD_AVAILABLE)
2118 wake_sleeping_thread(tsp->master);
2121 // If this thread is the master of a split point and all slaves have
2122 // finished their work at this split point, return from the idle loop.
2123 for (i = 0; sp && i < activeThreads && !sp->slaves[i]; i++) {}
2124 allFinished = (i == activeThreads);
2128 // Because sp->slaves[] is reset under lock protection,
2129 // be sure sp->lock has been released before to return.
2130 lock_grab(&(sp->lock));
2131 lock_release(&(sp->lock));
2133 // In helpful master concept a master can help only a sub-tree, and
2134 // because here is all finished is not possible master is booked.
2135 assert(threads[threadID].state == THREAD_AVAILABLE);
2137 threads[threadID].state = THREAD_SEARCHING;
2144 // init_threads() is called during startup. It launches all helper threads,
2145 // and initializes the split point stack and the global locks and condition
2148 void ThreadsManager::init_threads() {
2150 int i, arg[MAX_THREADS];
2153 // Initialize global locks
2156 for (i = 0; i < MAX_THREADS; i++)
2158 lock_init(&sleepLock[i]);
2159 cond_init(&sleepCond[i]);
2162 // Initialize splitPoints[] locks
2163 for (i = 0; i < MAX_THREADS; i++)
2164 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2165 lock_init(&(threads[i].splitPoints[j].lock));
2167 // Will be set just before program exits to properly end the threads
2168 allThreadsShouldExit = false;
2170 // Threads will be put all threads to sleep as soon as created
2173 // All threads except the main thread should be initialized to THREAD_INITIALIZING
2174 threads[0].state = THREAD_SEARCHING;
2175 for (i = 1; i < MAX_THREADS; i++)
2176 threads[i].state = THREAD_INITIALIZING;
2178 // Launch the helper threads
2179 for (i = 1; i < MAX_THREADS; i++)
2183 #if !defined(_MSC_VER)
2184 pthread_t pthread[1];
2185 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
2186 pthread_detach(pthread[0]);
2188 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
2192 cout << "Failed to create thread number " << i << endl;
2196 // Wait until the thread has finished launching and is gone to sleep
2197 while (threads[i].state == THREAD_INITIALIZING) {}
2202 // exit_threads() is called when the program exits. It makes all the
2203 // helper threads exit cleanly.
2205 void ThreadsManager::exit_threads() {
2207 allThreadsShouldExit = true; // Let the woken up threads to exit idle_loop()
2209 // Wake up all the threads and waits for termination
2210 for (int i = 1; i < MAX_THREADS; i++)
2212 wake_sleeping_thread(i);
2213 while (threads[i].state != THREAD_TERMINATED) {}
2216 // Now we can safely destroy the locks
2217 for (int i = 0; i < MAX_THREADS; i++)
2218 for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
2219 lock_destroy(&(threads[i].splitPoints[j].lock));
2221 lock_destroy(&mpLock);
2223 // Now we can safely destroy the wait conditions
2224 for (int i = 0; i < MAX_THREADS; i++)
2226 lock_destroy(&sleepLock[i]);
2227 cond_destroy(&sleepCond[i]);
2232 // cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
2233 // the thread's currently active split point, or in some ancestor of
2234 // the current split point.
2236 bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
2238 assert(threadID >= 0 && threadID < activeThreads);
2240 SplitPoint* sp = threads[threadID].splitPoint;
2242 for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
2247 // thread_is_available() checks whether the thread with threadID "slave" is
2248 // available to help the thread with threadID "master" at a split point. An
2249 // obvious requirement is that "slave" must be idle. With more than two
2250 // threads, this is not by itself sufficient: If "slave" is the master of
2251 // some active split point, it is only available as a slave to the other
2252 // threads which are busy searching the split point at the top of "slave"'s
2253 // split point stack (the "helpful master concept" in YBWC terminology).
2255 bool ThreadsManager::thread_is_available(int slave, int master) const {
2257 assert(slave >= 0 && slave < activeThreads);
2258 assert(master >= 0 && master < activeThreads);
2259 assert(activeThreads > 1);
2261 if (threads[slave].state != THREAD_AVAILABLE || slave == master)
2264 // Make a local copy to be sure doesn't change under our feet
2265 int localActiveSplitPoints = threads[slave].activeSplitPoints;
2267 // No active split points means that the thread is available as
2268 // a slave for any other thread.
2269 if (localActiveSplitPoints == 0 || activeThreads == 2)
2272 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
2273 // that is known to be > 0, instead of threads[slave].activeSplitPoints that
2274 // could have been set to 0 by another thread leading to an out of bound access.
2275 if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
2282 // available_thread_exists() tries to find an idle thread which is available as
2283 // a slave for the thread with threadID "master".
2285 bool ThreadsManager::available_thread_exists(int master) const {
2287 assert(master >= 0 && master < activeThreads);
2288 assert(activeThreads > 1);
2290 for (int i = 0; i < activeThreads; i++)
2291 if (thread_is_available(i, master))
2298 // split() does the actual work of distributing the work at a node between
2299 // several available threads. If it does not succeed in splitting the
2300 // node (because no idle threads are available, or because we have no unused
2301 // split point objects), the function immediately returns. If splitting is
2302 // possible, a SplitPoint object is initialized with all the data that must be
2303 // copied to the helper threads and we tell our helper threads that they have
2304 // been assigned work. This will cause them to instantly leave their idle loops and
2305 // call search().When all threads have returned from search() then split() returns.
2307 template <bool Fake>
2308 void ThreadsManager::split(Position& pos, SearchStack* ss, int ply, Value* alpha,
2309 const Value beta, Value* bestValue, Depth depth, Move threatMove,
2310 bool mateThreat, int moveCount, MovePicker* mp, bool pvNode) {
2311 assert(pos.is_ok());
2312 assert(ply > 0 && ply < PLY_MAX);
2313 assert(*bestValue >= -VALUE_INFINITE);
2314 assert(*bestValue <= *alpha);
2315 assert(*alpha < beta);
2316 assert(beta <= VALUE_INFINITE);
2317 assert(depth > DEPTH_ZERO);
2318 assert(pos.thread() >= 0 && pos.thread() < activeThreads);
2319 assert(activeThreads > 1);
2321 int i, master = pos.thread();
2322 Thread& masterThread = threads[master];
2326 // If no other thread is available to help us, or if we have too many
2327 // active split points, don't split.
2328 if ( !available_thread_exists(master)
2329 || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
2331 lock_release(&mpLock);
2335 // Pick the next available split point object from the split point stack
2336 SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
2338 // Initialize the split point object
2339 splitPoint.parent = masterThread.splitPoint;
2340 splitPoint.master = master;
2341 splitPoint.betaCutoff = false;
2342 splitPoint.ply = ply;
2343 splitPoint.depth = depth;
2344 splitPoint.threatMove = threatMove;
2345 splitPoint.mateThreat = mateThreat;
2346 splitPoint.alpha = *alpha;
2347 splitPoint.beta = beta;
2348 splitPoint.pvNode = pvNode;
2349 splitPoint.bestValue = *bestValue;
2351 splitPoint.moveCount = moveCount;
2352 splitPoint.pos = &pos;
2353 splitPoint.nodes = 0;
2355 for (i = 0; i < activeThreads; i++)
2356 splitPoint.slaves[i] = 0;
2358 masterThread.splitPoint = &splitPoint;
2360 // If we are here it means we are not available
2361 assert(masterThread.state != THREAD_AVAILABLE);
2363 int workersCnt = 1; // At least the master is included
2365 // Allocate available threads setting state to THREAD_BOOKED
2366 for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
2367 if (thread_is_available(i, master))
2369 threads[i].state = THREAD_BOOKED;
2370 threads[i].splitPoint = &splitPoint;
2371 splitPoint.slaves[i] = 1;
2375 assert(Fake || workersCnt > 1);
2377 // We can release the lock because slave threads are already booked and master is not available
2378 lock_release(&mpLock);
2380 // Tell the threads that they have work to do. This will make them leave
2382 for (i = 0; i < activeThreads; i++)
2383 if (i == master || splitPoint.slaves[i])
2385 assert(i == master || threads[i].state == THREAD_BOOKED);
2387 threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
2389 if (useSleepingThreads && i != master)
2390 wake_sleeping_thread(i);
2393 // Everything is set up. The master thread enters the idle loop, from
2394 // which it will instantly launch a search, because its state is
2395 // THREAD_WORKISWAITING. We send the split point as a second parameter to the
2396 // idle loop, which means that the main thread will return from the idle
2397 // loop when all threads have finished their work at this split point.
2398 idle_loop(master, &splitPoint);
2400 // We have returned from the idle loop, which means that all threads are
2401 // finished. Update alpha and bestValue, and return.
2404 *alpha = splitPoint.alpha;
2405 *bestValue = splitPoint.bestValue;
2406 masterThread.activeSplitPoints--;
2407 masterThread.splitPoint = splitPoint.parent;
2408 pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
2410 lock_release(&mpLock);
2414 // wake_sleeping_thread() wakes up the thread with the given threadID
2415 // when it is time to start a new search.
2417 void ThreadsManager::wake_sleeping_thread(int threadID) {
2419 lock_grab(&sleepLock[threadID]);
2420 cond_signal(&sleepCond[threadID]);
2421 lock_release(&sleepLock[threadID]);
2425 /// RootMove and RootMoveList method's definitions
2427 RootMove::RootMove() {
2430 pv_score = non_pv_score = -VALUE_INFINITE;
2434 RootMove& RootMove::operator=(const RootMove& rm) {
2436 const Move* src = rm.pv;
2439 // Avoid a costly full rm.pv[] copy
2440 do *dst++ = *src; while (*src++ != MOVE_NONE);
2443 pv_score = rm.pv_score;
2444 non_pv_score = rm.non_pv_score;
2448 // extract_pv_from_tt() builds a PV by adding moves from the transposition table.
2449 // We consider also failing high nodes and not only VALUE_TYPE_EXACT nodes. This
2450 // allow to always have a ponder move even when we fail high at root and also a
2451 // long PV to print that is important for position analysis.
2453 void RootMove::extract_pv_from_tt(Position& pos) {
2455 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2459 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2461 pos.do_move(pv[0], *st++);
2463 while ( (tte = TT.retrieve(pos.get_key())) != NULL
2464 && tte->move() != MOVE_NONE
2465 && move_is_legal(pos, tte->move())
2467 && (!pos.is_draw() || ply < 2))
2469 pv[ply] = tte->move();
2470 pos.do_move(pv[ply++], *st++);
2472 pv[ply] = MOVE_NONE;
2474 do pos.undo_move(pv[--ply]); while (ply);
2477 // insert_pv_in_tt() is called at the end of a search iteration, and inserts
2478 // the PV back into the TT. This makes sure the old PV moves are searched
2479 // first, even if the old TT entries have been overwritten.
2481 void RootMove::insert_pv_in_tt(Position& pos) {
2483 StateInfo state[PLY_MAX_PLUS_2], *st = state;
2486 Value v, m = VALUE_NONE;
2489 assert(pv[0] != MOVE_NONE && move_is_legal(pos, pv[0]));
2493 tte = TT.retrieve(k);
2495 // Don't overwrite existing correct entries
2496 if (!tte || tte->move() != pv[ply])
2498 v = (pos.is_check() ? VALUE_NONE : evaluate(pos, m));
2499 TT.store(k, VALUE_NONE, VALUE_TYPE_NONE, DEPTH_NONE, pv[ply], v, m);
2501 pos.do_move(pv[ply], *st++);
2503 } while (pv[++ply] != MOVE_NONE);
2505 do pos.undo_move(pv[--ply]); while (ply);
2508 // pv_info_to_uci() returns a string with information on the current PV line
2509 // formatted according to UCI specification. It is called at each iteration
2510 // or after a new pv is found.
2512 std::string RootMove::pv_info_to_uci(Position& pos, int depth, Value alpha, Value beta, int pvLine) {
2514 std::stringstream s, l;
2517 while (*m != MOVE_NONE)
2520 s << "info depth " << depth
2521 << " seldepth " << int(m - pv)
2522 << " multipv " << pvLine + 1
2523 << " score " << value_to_uci(pv_score)
2524 << (pv_score >= beta ? " lowerbound" : pv_score <= alpha ? " upperbound" : "")
2525 << speed_to_uci(pos.nodes_searched())
2526 << " pv " << l.str();
2532 void RootMoveList::init(Position& pos, Move searchMoves[]) {
2534 MoveStack mlist[MOVES_MAX];
2538 bestMoveChanges = 0;
2540 // Generate all legal moves and add them to RootMoveList
2541 MoveStack* last = generate<MV_LEGAL>(pos, mlist);
2542 for (MoveStack* cur = mlist; cur != last; cur++)
2544 // If we have a searchMoves[] list then verify cur->move
2545 // is in the list before to add it.
2546 for (sm = searchMoves; *sm && *sm != cur->move; sm++) {}
2548 if (searchMoves[0] && *sm != cur->move)
2552 rm.pv[0] = cur->move;
2553 rm.pv[1] = MOVE_NONE;
2554 rm.pv_score = -VALUE_INFINITE;