2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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/>.
43 #include "ucioption.h"
49 //// Local definitions
56 // IterationInfoType stores search results for each iteration
58 // Because we use relatively small (dynamic) aspiration window,
59 // there happens many fail highs and fail lows in root. And
60 // because we don't do researches in those cases, "value" stored
61 // here is not necessarily exact. Instead in case of fail high/low
62 // we guess what the right value might be and store our guess
63 // as a "speculated value" and then move on. Speculated values are
64 // used just to calculate aspiration window width, so also if are
65 // not exact is not big a problem.
67 struct IterationInfoType {
69 IterationInfoType(Value v = Value(0), Value sv = Value(0))
70 : value(v), speculatedValue(sv) {}
72 Value value, speculatedValue;
76 // The BetaCounterType class is used to order moves at ply one.
77 // Apart for the first one that has its score, following moves
78 // normally have score -VALUE_INFINITE, so are ordered according
79 // to the number of beta cutoffs occurred under their subtree during
80 // the last iteration. The counters are per thread variables to avoid
81 // concurrent accessing under SMP case.
83 struct BetaCounterType {
87 void add(Color us, Depth d, int threadID);
88 void read(Color us, int64_t& our, int64_t& their);
92 // The RootMove class is used for moves at the root at the tree. For each
93 // root move, we store a score, a node count, and a PV (really a refutation
94 // in the case of moves which fail low).
98 RootMove() { nodes = cumulativeNodes = ourBeta = theirBeta = 0ULL; }
100 // RootMove::operator<() is the comparison function used when
101 // sorting the moves. A move m1 is considered to be better
102 // than a move m2 if it has a higher score, or if the moves
103 // have equal score but m1 has the higher node count.
104 bool operator<(const RootMove& m) const {
106 return score != m.score ? score < m.score : theirBeta <= m.theirBeta;
111 int64_t nodes, cumulativeNodes, ourBeta, theirBeta;
112 Move pv[PLY_MAX_PLUS_2];
116 // The RootMoveList class is essentially an array of RootMove objects, with
117 // a handful of methods for accessing the data in the individual moves.
122 RootMoveList(Position& pos, Move searchMoves[]);
124 int move_count() const { return count; }
125 Move get_move(int moveNum) const { return moves[moveNum].move; }
126 Value get_move_score(int moveNum) const { return moves[moveNum].score; }
127 void set_move_score(int moveNum, Value score) { moves[moveNum].score = score; }
128 Move get_move_pv(int moveNum, int i) const { return moves[moveNum].pv[i]; }
129 int64_t get_move_cumulative_nodes(int moveNum) const { return moves[moveNum].cumulativeNodes; }
131 void set_move_nodes(int moveNum, int64_t nodes);
132 void set_beta_counters(int moveNum, int64_t our, int64_t their);
133 void set_move_pv(int moveNum, const Move pv[]);
135 void sort_multipv(int n);
138 static const int MaxRootMoves = 500;
139 RootMove moves[MaxRootMoves];
146 // Search depth at iteration 1
147 const Depth InitialDepth = OnePly;
149 // Depth limit for selective search
150 const Depth SelectiveDepth = 7 * OnePly;
152 // Use internal iterative deepening?
153 const bool UseIIDAtPVNodes = true;
154 const bool UseIIDAtNonPVNodes = true;
156 // Internal iterative deepening margin. At Non-PV moves, when
157 // UseIIDAtNonPVNodes is true, we do an internal iterative deepening
158 // search when the static evaluation is at most IIDMargin below beta.
159 const Value IIDMargin = Value(0x100);
161 // Easy move margin. An easy move candidate must be at least this much
162 // better than the second best move.
163 const Value EasyMoveMargin = Value(0x200);
165 // Problem margin. If the score of the first move at iteration N+1 has
166 // dropped by more than this since iteration N, the boolean variable
167 // "Problem" is set to true, which will make the program spend some extra
168 // time looking for a better move.
169 const Value ProblemMargin = Value(0x28);
171 // No problem margin. If the boolean "Problem" is true, and a new move
172 // is found at the root which is less than NoProblemMargin worse than the
173 // best move from the previous iteration, Problem is set back to false.
174 const Value NoProblemMargin = Value(0x14);
176 // Null move margin. A null move search will not be done if the static
177 // evaluation of the position is more than NullMoveMargin below beta.
178 const Value NullMoveMargin = Value(0x200);
180 // If the TT move is at least SingleReplyMargin better then the
181 // remaining ones we will extend it.
182 const Value SingleReplyMargin = Value(0x20);
184 // Margins for futility pruning in the quiescence search, and at frontier
185 // and near frontier nodes.
186 const Value FutilityMarginQS = Value(0x80);
188 Value FutilityMargins[2 * PLY_MAX_PLUS_2]; // Initialized at startup.
190 // Each move futility margin is decreased
191 const Value IncrementalFutilityMargin = Value(0x8);
193 // Depth limit for razoring
194 const Depth RazorDepth = 4 * OnePly;
196 /// Variables initialized by UCI options
198 // Depth limit for use of dynamic threat detection
201 // Last seconds noise filtering (LSN)
202 const bool UseLSNFiltering = true;
203 const int LSNTime = 4000; // In milliseconds
204 const Value LSNValue = value_from_centipawns(200);
205 bool loseOnTime = false;
207 // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
208 Depth CheckExtension[2], SingleEvasionExtension[2], PawnPushTo7thExtension[2];
209 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
211 // Iteration counters
213 BetaCounterType BetaCounter;
215 // Scores and number of times the best move changed for each iteration
216 IterationInfoType IterationInfo[PLY_MAX_PLUS_2];
217 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
219 // Search window management
225 // Time managment variables
228 int MaxNodes, MaxDepth;
229 int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime, ExactMaxTime;
230 bool UseTimeManagement, InfiniteSearch, PonderSearch, StopOnPonderhit;
231 bool AbortSearch, Quit;
232 bool FailHigh, FailLow, Problem;
234 // Show current line?
235 bool ShowCurrentLine;
239 std::ofstream LogFile;
241 // Natural logarithmic lookup table and its getter function
243 inline double ln(int i) { return lnArray[i]; }
245 // MP related variables
246 int ActiveThreads = 1;
247 Depth MinimumSplitDepth;
248 int MaxThreadsPerSplitPoint;
249 Thread Threads[THREAD_MAX];
252 bool AllThreadsShouldExit = false;
253 SplitPoint SplitPointStack[THREAD_MAX][ACTIVE_SPLIT_POINTS_MAX];
256 #if !defined(_MSC_VER)
257 pthread_cond_t WaitCond;
258 pthread_mutex_t WaitLock;
260 HANDLE SitIdleEvent[THREAD_MAX];
263 // Node counters, used only by thread[0] but try to keep in different
264 // cache lines (64 bytes each) from the heavy SMP read accessed variables.
266 int NodesBetweenPolls = 30000;
273 Value id_loop(const Position& pos, Move searchMoves[]);
274 Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta);
275 Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
276 Value search(Position& pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID, Move excludedMove = MOVE_NONE);
277 Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
278 void sp_search(SplitPoint* sp, int threadID);
279 void sp_search_pv(SplitPoint* sp, int threadID);
280 void init_node(SearchStack ss[], int ply, int threadID);
281 void update_pv(SearchStack ss[], int ply);
282 void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply);
283 bool connected_moves(const Position& pos, Move m1, Move m2);
284 bool value_is_mate(Value value);
285 bool move_is_killer(Move m, const SearchStack& ss);
286 Depth extension(const Position&, Move, bool, bool, bool, bool, bool, bool*);
287 bool ok_to_do_nullmove(const Position& pos);
288 bool ok_to_prune(const Position& pos, Move m, Move threat);
289 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
290 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply);
291 Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor);
292 void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount);
293 void update_killers(Move m, SearchStack& ss);
294 void update_gains(const Position& pos, Move move, Value before, Value after);
296 bool fail_high_ply_1();
297 int current_search_time();
301 void print_current_line(SearchStack ss[], int ply, int threadID);
302 void wait_for_stop_or_ponderhit();
303 void init_ss_array(SearchStack ss[]);
305 void idle_loop(int threadID, SplitPoint* waitSp);
306 void init_split_point_stack();
307 void destroy_split_point_stack();
308 bool thread_should_stop(int threadID);
309 bool thread_is_available(int slave, int master);
310 bool idle_thread_exists(int master);
311 bool split(const Position& pos, SearchStack* ss, int ply,
312 Value *alpha, Value *beta, Value *bestValue,
313 const Value futilityValue, Depth depth, int *moves,
314 MovePicker *mp, int master, bool pvNode);
315 void wake_sleeping_threads();
317 #if !defined(_MSC_VER)
318 void *init_thread(void *threadID);
320 DWORD WINAPI init_thread(LPVOID threadID);
331 /// perft() is our utility to verify move generation is bug free. All the legal
332 /// moves up to given depth are generated and counted and the sum returned.
334 int perft(Position& pos, Depth depth)
338 MovePicker mp = MovePicker(pos, MOVE_NONE, depth, H);
340 // If we are at the last ply we don't need to do and undo
341 // the moves, just to count them.
342 if (depth <= OnePly) // Replace with '<' to test also qsearch
344 while (mp.get_next_move()) sum++;
348 // Loop through all legal moves
350 while ((move = mp.get_next_move()) != MOVE_NONE)
353 pos.do_move(move, st, ci, pos.move_is_check(move, ci));
354 sum += perft(pos, depth - OnePly);
361 /// think() is the external interface to Stockfish's search, and is called when
362 /// the program receives the UCI 'go' command. It initializes various
363 /// search-related global variables, and calls root_search(). It returns false
364 /// when a quit command is received during the search.
366 bool think(const Position& pos, bool infinite, bool ponder, int side_to_move,
367 int time[], int increment[], int movesToGo, int maxDepth,
368 int maxNodes, int maxTime, Move searchMoves[]) {
370 // Initialize global search variables
371 Idle = StopOnPonderhit = AbortSearch = Quit = false;
372 FailHigh = FailLow = Problem = false;
374 SearchStartTime = get_system_time();
375 ExactMaxTime = maxTime;
378 InfiniteSearch = infinite;
379 PonderSearch = ponder;
380 UseTimeManagement = !ExactMaxTime && !MaxDepth && !MaxNodes && !InfiniteSearch;
382 // Look for a book move, only during games, not tests
383 if (UseTimeManagement && !ponder && get_option_value_bool("OwnBook"))
386 if (get_option_value_string("Book File") != OpeningBook.file_name())
387 OpeningBook.open(get_option_value_string("Book File"));
389 bookMove = OpeningBook.get_move(pos);
390 if (bookMove != MOVE_NONE)
392 cout << "bestmove " << bookMove << endl;
397 for (int i = 0; i < THREAD_MAX; i++)
399 Threads[i].nodes = 0ULL;
400 Threads[i].failHighPly1 = false;
403 if (button_was_pressed("New Game"))
404 loseOnTime = false; // Reset at the beginning of a new game
406 // Read UCI option values
407 TT.set_size(get_option_value_int("Hash"));
408 if (button_was_pressed("Clear Hash"))
411 bool PonderingEnabled = get_option_value_bool("Ponder");
412 MultiPV = get_option_value_int("MultiPV");
414 CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
415 CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)"));
417 SingleEvasionExtension[1] = Depth(get_option_value_int("Single Evasion Extension (PV nodes)"));
418 SingleEvasionExtension[0] = Depth(get_option_value_int("Single Evasion Extension (non-PV nodes)"));
420 PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
421 PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
423 PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
424 PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
426 PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
427 PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
429 MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
430 MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
432 ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
434 Chess960 = get_option_value_bool("UCI_Chess960");
435 ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
436 UseLogFile = get_option_value_bool("Use Search Log");
438 LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
440 MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
441 MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point");
443 read_weights(pos.side_to_move());
445 // Set the number of active threads
446 int newActiveThreads = get_option_value_int("Threads");
447 if (newActiveThreads != ActiveThreads)
449 ActiveThreads = newActiveThreads;
450 init_eval(ActiveThreads);
451 // HACK: init_eval() destroys the static castleRightsMask[] array in the
452 // Position class. The below line repairs the damage.
453 Position p(pos.to_fen());
457 // Wake up sleeping threads
458 wake_sleeping_threads();
460 for (int i = 1; i < ActiveThreads; i++)
461 assert(thread_is_available(i, 0));
464 int myTime = time[side_to_move];
465 int myIncrement = increment[side_to_move];
466 if (UseTimeManagement)
468 if (!movesToGo) // Sudden death time control
472 MaxSearchTime = myTime / 30 + myIncrement;
473 AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
475 else // Blitz game without increment
477 MaxSearchTime = myTime / 30;
478 AbsoluteMaxSearchTime = myTime / 8;
481 else // (x moves) / (y minutes)
485 MaxSearchTime = myTime / 2;
486 AbsoluteMaxSearchTime = (myTime > 3000)? (myTime - 500) : ((myTime * 3) / 4);
490 MaxSearchTime = myTime / Min(movesToGo, 20);
491 AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3);
495 if (PonderingEnabled)
497 MaxSearchTime += MaxSearchTime / 4;
498 MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
502 // Set best NodesBetweenPolls interval
504 NodesBetweenPolls = Min(MaxNodes, 30000);
505 else if (myTime && myTime < 1000)
506 NodesBetweenPolls = 1000;
507 else if (myTime && myTime < 5000)
508 NodesBetweenPolls = 5000;
510 NodesBetweenPolls = 30000;
512 // Write information to search log file
514 LogFile << "Searching: " << pos.to_fen() << endl
515 << "infinite: " << infinite
516 << " ponder: " << ponder
517 << " time: " << myTime
518 << " increment: " << myIncrement
519 << " moves to go: " << movesToGo << endl;
521 // LSN filtering. Used only for developing purpose. Disabled by default.
525 // Step 2. If after last move we decided to lose on time, do it now!
526 while (SearchStartTime + myTime + 1000 > get_system_time())
530 // We're ready to start thinking. Call the iterative deepening loop function
531 Value v = id_loop(pos, searchMoves);
536 // Step 1. If this is sudden death game and our position is hopeless,
537 // decide to lose on time.
538 if ( !loseOnTime // If we already lost on time, go to step 3.
548 // Step 3. Now after stepping over the time limit, reset flag for next match.
561 /// init_threads() is called during startup. It launches all helper threads,
562 /// and initializes the split point stack and the global locks and condition
565 void init_threads() {
570 #if !defined(_MSC_VER)
571 pthread_t pthread[1];
574 // Init our logarithmic lookup table
575 for (i = 0; i < 512; i++)
576 lnArray[i] = log(double(i)); // log() returns base-e logarithm
578 for (i = 0; i < THREAD_MAX; i++)
579 Threads[i].activeSplitPoints = 0;
581 // Init futility margins array
582 FutilityMargins[0] = FutilityMargins[1] = Value(0);
584 for (i = 2; i < 2 * PLY_MAX_PLUS_2; i++)
586 FutilityMargins[i] = Value(112 * bitScanReverse32(i * i / 2)); // FIXME: test using log instead of BSR
589 // Initialize global locks
590 lock_init(&MPLock, NULL);
591 lock_init(&IOLock, NULL);
593 init_split_point_stack();
595 #if !defined(_MSC_VER)
596 pthread_mutex_init(&WaitLock, NULL);
597 pthread_cond_init(&WaitCond, NULL);
599 for (i = 0; i < THREAD_MAX; i++)
600 SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
603 // All threads except the main thread should be initialized to idle state
604 for (i = 1; i < THREAD_MAX; i++)
606 Threads[i].stop = false;
607 Threads[i].workIsWaiting = false;
608 Threads[i].idle = true;
609 Threads[i].running = false;
612 // Launch the helper threads
613 for (i = 1; i < THREAD_MAX; i++)
615 #if !defined(_MSC_VER)
616 ok = (pthread_create(pthread, NULL, init_thread, (void*)(&i)) == 0);
619 ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID) != NULL);
624 cout << "Failed to create thread number " << i << endl;
625 Application::exit_with_failure();
628 // Wait until the thread has finished launching
629 while (!Threads[i].running);
634 /// stop_threads() is called when the program exits. It makes all the
635 /// helper threads exit cleanly.
637 void stop_threads() {
639 ActiveThreads = THREAD_MAX; // HACK
640 Idle = false; // HACK
641 wake_sleeping_threads();
642 AllThreadsShouldExit = true;
643 for (int i = 1; i < THREAD_MAX; i++)
645 Threads[i].stop = true;
646 while (Threads[i].running);
648 destroy_split_point_stack();
652 /// nodes_searched() returns the total number of nodes searched so far in
653 /// the current search.
655 int64_t nodes_searched() {
657 int64_t result = 0ULL;
658 for (int i = 0; i < ActiveThreads; i++)
659 result += Threads[i].nodes;
664 // SearchStack::init() initializes a search stack. Used at the beginning of a
665 // new search from the root.
666 void SearchStack::init(int ply) {
668 pv[ply] = pv[ply + 1] = MOVE_NONE;
669 currentMove = threatMove = MOVE_NONE;
670 reduction = Depth(0);
675 void SearchStack::initKillers() {
677 mateKiller = MOVE_NONE;
678 for (int i = 0; i < KILLER_MAX; i++)
679 killers[i] = MOVE_NONE;
684 // id_loop() is the main iterative deepening loop. It calls root_search
685 // repeatedly with increasing depth until the allocated thinking time has
686 // been consumed, the user stops the search, or the maximum search depth is
689 Value id_loop(const Position& pos, Move searchMoves[]) {
692 SearchStack ss[PLY_MAX_PLUS_2];
694 // searchMoves are verified, copied, scored and sorted
695 RootMoveList rml(p, searchMoves);
697 if (rml.move_count() == 0)
700 wait_for_stop_or_ponderhit();
702 return pos.is_check()? -VALUE_MATE : VALUE_DRAW;
705 // Print RootMoveList c'tor startup scoring to the standard output,
706 // so that we print information also for iteration 1.
707 cout << "info depth " << 1 << "\ninfo depth " << 1
708 << " score " << value_to_string(rml.get_move_score(0))
709 << " time " << current_search_time()
710 << " nodes " << nodes_searched()
712 << " pv " << rml.get_move(0) << "\n";
718 IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0));
721 // Is one move significantly better than others after initial scoring ?
722 Move EasyMove = MOVE_NONE;
723 if ( rml.move_count() == 1
724 || rml.get_move_score(0) > rml.get_move_score(1) + EasyMoveMargin)
725 EasyMove = rml.get_move(0);
727 // Iterative deepening loop
728 while (Iteration < PLY_MAX)
730 // Initialize iteration
733 BestMoveChangesByIteration[Iteration] = 0;
737 cout << "info depth " << Iteration << endl;
739 // Calculate dynamic search window based on previous iterations
742 if (MultiPV == 1 && Iteration >= 6 && abs(IterationInfo[Iteration - 1].value) < VALUE_KNOWN_WIN)
744 int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
745 int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
747 int delta = Max(abs(prevDelta1) + abs(prevDelta2) / 2, 16);
749 delta = (delta + 7) / 8 * 8; // Round to match grainSize
750 AspirationDelta = delta;
752 alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE);
753 beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE);
757 alpha = - VALUE_INFINITE;
758 beta = VALUE_INFINITE;
761 // Search to the current depth
762 Value value = root_search(p, ss, rml, alpha, beta);
764 // Write PV to transposition table, in case the relevant entries have
765 // been overwritten during the search.
766 TT.insert_pv(p, ss[0].pv);
769 break; // Value cannot be trusted. Break out immediately!
771 //Save info about search result
772 Value speculatedValue;
775 Value delta = value - IterationInfo[Iteration - 1].value;
782 speculatedValue = value + delta;
783 BestMoveChangesByIteration[Iteration] += 2; // Allocate more time
785 else if (value <= alpha)
787 assert(value == alpha);
791 speculatedValue = value + delta;
792 BestMoveChangesByIteration[Iteration] += 3; // Allocate more time
794 speculatedValue = value;
796 speculatedValue = Min(Max(speculatedValue, -VALUE_INFINITE), VALUE_INFINITE);
797 IterationInfo[Iteration] = IterationInfoType(value, speculatedValue);
799 // Drop the easy move if it differs from the new best move
800 if (ss[0].pv[0] != EasyMove)
801 EasyMove = MOVE_NONE;
805 if (UseTimeManagement)
808 bool stopSearch = false;
810 // Stop search early if there is only a single legal move,
811 // we search up to Iteration 6 anyway to get a proper score.
812 if (Iteration >= 6 && rml.move_count() == 1)
815 // Stop search early when the last two iterations returned a mate score
817 && abs(IterationInfo[Iteration].value) >= abs(VALUE_MATE) - 100
818 && abs(IterationInfo[Iteration-1].value) >= abs(VALUE_MATE) - 100)
821 // Stop search early if one move seems to be much better than the rest
822 int64_t nodes = nodes_searched();
826 && EasyMove == ss[0].pv[0]
827 && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100
828 && current_search_time() > MaxSearchTime / 16)
829 ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100
830 && current_search_time() > MaxSearchTime / 32)))
833 // Add some extra time if the best move has changed during the last two iterations
834 if (Iteration > 5 && Iteration <= 50)
835 ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2)
836 + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
838 // Stop search if most of MaxSearchTime is consumed at the end of the
839 // iteration. We probably don't have enough time to search the first
840 // move at the next iteration anyway.
841 if (current_search_time() > ((MaxSearchTime + ExtraSearchTime) * 80) / 128)
849 StopOnPonderhit = true;
853 if (MaxDepth && Iteration >= MaxDepth)
859 // If we are pondering or in infinite search, we shouldn't print the
860 // best move before we are told to do so.
861 if (!AbortSearch && (PonderSearch || InfiniteSearch))
862 wait_for_stop_or_ponderhit();
864 // Print final search statistics
865 cout << "info nodes " << nodes_searched()
867 << " time " << current_search_time()
868 << " hashfull " << TT.full() << endl;
870 // Print the best move and the ponder move to the standard output
871 if (ss[0].pv[0] == MOVE_NONE)
873 ss[0].pv[0] = rml.get_move(0);
874 ss[0].pv[1] = MOVE_NONE;
876 cout << "bestmove " << ss[0].pv[0];
877 if (ss[0].pv[1] != MOVE_NONE)
878 cout << " ponder " << ss[0].pv[1];
885 dbg_print_mean(LogFile);
887 if (dbg_show_hit_rate)
888 dbg_print_hit_rate(LogFile);
890 LogFile << "\nNodes: " << nodes_searched()
891 << "\nNodes/second: " << nps()
892 << "\nBest move: " << move_to_san(p, ss[0].pv[0]);
895 p.do_move(ss[0].pv[0], st);
896 LogFile << "\nPonder move: " << move_to_san(p, ss[0].pv[1]) << endl;
898 return rml.get_move_score(0);
902 // root_search() is the function which searches the root node. It is
903 // similar to search_pv except that it uses a different move ordering
904 // scheme and prints some information to the standard output.
906 Value root_search(Position& pos, SearchStack ss[], RootMoveList& rml, Value& oldAlpha, Value& beta) {
908 Value alpha = oldAlpha;
911 int researchCount = 0;
912 bool isCheck = pos.is_check();
914 // Evaluate the position statically
917 ss[0].eval = evaluate(pos, ei, 0);
919 ss[0].eval = VALUE_NONE;
921 while(1) // Fail low loop
924 // Loop through all the moves in the root move list
925 for (int i = 0; i < rml.move_count() && !AbortSearch; i++)
929 // We failed high, invalidate and skip next moves, leave node-counters
930 // and beta-counters as they are and quickly return, we will try to do
931 // a research at the next iteration with a bigger aspiration window.
932 rml.set_move_score(i, -VALUE_INFINITE);
938 Depth depth, ext, newDepth;
940 RootMoveNumber = i + 1;
943 // Save the current node count before the move is searched
944 nodes = nodes_searched();
946 // Reset beta cut-off counters
949 // Pick the next root move, and print the move and the move number to
950 // the standard output.
951 move = ss[0].currentMove = rml.get_move(i);
953 if (current_search_time() >= 1000)
954 cout << "info currmove " << move
955 << " currmovenumber " << RootMoveNumber << endl;
957 // Decide search depth for this move
958 bool moveIsCheck = pos.move_is_check(move);
959 bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
961 depth = (Iteration - 2) * OnePly + InitialDepth;
962 ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
963 newDepth = depth + ext;
965 value = - VALUE_INFINITE;
967 while (1) // Fail high loop
970 // Make the move, and search it
971 pos.do_move(move, st, ci, moveIsCheck);
973 if (i < MultiPV || value > alpha)
975 // Aspiration window is disabled in multi-pv case
977 alpha = -VALUE_INFINITE;
979 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
981 // If the value has dropped a lot compared to the last iteration,
982 // set the boolean variable Problem to true. This variable is used
983 // for time managment: When Problem is true, we try to complete the
984 // current iteration before playing a move.
985 Problem = ( Iteration >= 2
986 && value <= IterationInfo[Iteration - 1].value - ProblemMargin);
988 if (Problem && StopOnPonderhit)
989 StopOnPonderhit = false;
993 // Try to reduce non-pv search depth by one ply if move seems not problematic,
994 // if the move fails high will be re-searched at full depth.
995 bool doFullDepthSearch = true;
997 if ( depth >= 3*OnePly // FIXME was newDepth
999 && !captureOrPromotion
1000 && !move_is_castle(move))
1002 ss[0].reduction = calculate_reduction(0.5, RootMoveNumber - MultiPV + 1, depth, 6.0);
1003 if (ss[0].reduction)
1005 value = -search(pos, ss, -alpha, newDepth-ss[0].reduction, 1, true, 0);
1006 doFullDepthSearch = (value > alpha);
1010 if (doFullDepthSearch)
1012 ss[0].reduction = Depth(0);
1013 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
1017 // Fail high! Set the boolean variable FailHigh to true, and
1018 // re-search the move using a PV search. The variable FailHigh
1019 // is used for time managment: We try to avoid aborting the
1020 // search prematurely during a fail high research.
1022 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
1027 pos.undo_move(move);
1029 if (AbortSearch || value < beta)
1030 break; // We are not failing high
1032 // We are failing high and going to do a research. It's important to update score
1033 // before research in case we run out of time while researching.
1034 rml.set_move_score(i, value);
1036 TT.extract_pv(pos, ss[0].pv, PLY_MAX);
1037 rml.set_move_pv(i, ss[0].pv);
1039 // Print search information to the standard output
1040 cout << "info depth " << Iteration
1041 << " score " << value_to_string(value)
1042 << ((value >= beta) ? " lowerbound" :
1043 ((value <= alpha)? " upperbound" : ""))
1044 << " time " << current_search_time()
1045 << " nodes " << nodes_searched()
1049 for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
1050 cout << ss[0].pv[j] << " ";
1056 ValueType type = (value >= beta ? VALUE_TYPE_LOWER
1057 : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT));
1059 LogFile << pretty_pv(pos, current_search_time(), Iteration,
1060 nodes_searched(), value, type, ss[0].pv) << endl;
1063 // Prepare for research
1065 beta = Min(beta + AspirationDelta * (1 << researchCount), VALUE_INFINITE);
1067 } // End of fail high loop
1069 // Finished searching the move. If AbortSearch is true, the search
1070 // was aborted because the user interrupted the search or because we
1071 // ran out of time. In this case, the return value of the search cannot
1072 // be trusted, and we break out of the loop without updating the best
1077 // Remember beta-cutoff and searched nodes counts for this move. The
1078 // info is used to sort the root moves at the next iteration.
1080 BetaCounter.read(pos.side_to_move(), our, their);
1081 rml.set_beta_counters(i, our, their);
1082 rml.set_move_nodes(i, nodes_searched() - nodes);
1084 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
1086 if (value <= alpha && i >= MultiPV)
1087 rml.set_move_score(i, -VALUE_INFINITE);
1090 // PV move or new best move!
1093 rml.set_move_score(i, value);
1095 TT.extract_pv(pos, ss[0].pv, PLY_MAX);
1096 rml.set_move_pv(i, ss[0].pv);
1100 // We record how often the best move has been changed in each
1101 // iteration. This information is used for time managment: When
1102 // the best move changes frequently, we allocate some more time.
1104 BestMoveChangesByIteration[Iteration]++;
1106 // Print search information to the standard output
1107 cout << "info depth " << Iteration
1108 << " score " << value_to_string(value)
1109 << ((value >= beta) ? " lowerbound" :
1110 ((value <= alpha)? " upperbound" : ""))
1111 << " time " << current_search_time()
1112 << " nodes " << nodes_searched()
1116 for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
1117 cout << ss[0].pv[j] << " ";
1123 ValueType type = (value >= beta ? VALUE_TYPE_LOWER
1124 : (value <= alpha ? VALUE_TYPE_UPPER : VALUE_TYPE_EXACT));
1126 LogFile << pretty_pv(pos, current_search_time(), Iteration,
1127 nodes_searched(), value, type, ss[0].pv) << endl;
1132 // Reset the global variable Problem to false if the value isn't too
1133 // far below the final value from the last iteration.
1134 if (value > IterationInfo[Iteration - 1].value - NoProblemMargin)
1139 rml.sort_multipv(i);
1140 for (int j = 0; j < Min(MultiPV, rml.move_count()); j++)
1142 cout << "info multipv " << j + 1
1143 << " score " << value_to_string(rml.get_move_score(j))
1144 << " depth " << ((j <= i)? Iteration : Iteration - 1)
1145 << " time " << current_search_time()
1146 << " nodes " << nodes_searched()
1150 for (int k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
1151 cout << rml.get_move_pv(j, k) << " ";
1155 alpha = rml.get_move_score(Min(i, MultiPV-1));
1157 } // PV move or new best move
1159 assert(alpha >= oldAlpha);
1161 FailLow = (alpha == oldAlpha);
1164 if (AbortSearch || alpha > oldAlpha)
1165 break; // End search, we are not failing low
1167 // Prepare for research
1169 alpha = Max(alpha - AspirationDelta * (1 << researchCount), -VALUE_INFINITE);
1178 // search_pv() is the main search function for PV nodes.
1180 Value search_pv(Position& pos, SearchStack ss[], Value alpha, Value beta,
1181 Depth depth, int ply, int threadID) {
1183 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1184 assert(beta > alpha && beta <= VALUE_INFINITE);
1185 assert(ply >= 0 && ply < PLY_MAX);
1186 assert(threadID >= 0 && threadID < ActiveThreads);
1188 Move movesSearched[256];
1192 Depth ext, newDepth;
1193 Value oldAlpha, value;
1194 bool isCheck, mateThreat, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
1196 Value bestValue = value = -VALUE_INFINITE;
1199 return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
1201 // Initialize, and make an early exit in case of an aborted search,
1202 // an instant draw, maximum ply reached, etc.
1203 init_node(ss, ply, threadID);
1205 // After init_node() that calls poll()
1206 if (AbortSearch || thread_should_stop(threadID))
1209 if (pos.is_draw() || ply >= PLY_MAX - 1)
1212 // Mate distance pruning
1214 alpha = Max(value_mated_in(ply), alpha);
1215 beta = Min(value_mate_in(ply+1), beta);
1219 // Transposition table lookup. At PV nodes, we don't use the TT for
1220 // pruning, but only for move ordering. This is to avoid problems in
1221 // the following areas:
1223 // * Repetition draw detection
1224 // * Fifty move rule detection
1225 // * Searching for a mate
1226 // * Printing of full PV line
1228 tte = TT.retrieve(pos.get_key());
1229 ttMove = (tte ? tte->move() : MOVE_NONE);
1231 // Go with internal iterative deepening if we don't have a TT move
1232 if ( UseIIDAtPVNodes
1233 && depth >= 5*OnePly
1234 && ttMove == MOVE_NONE)
1236 search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
1237 ttMove = ss[ply].pv[ply];
1238 tte = TT.retrieve(pos.get_key());
1241 isCheck = pos.is_check();
1244 // Update gain statistics of the previous move that lead
1245 // us in this position.
1247 ss[ply].eval = evaluate(pos, ei, threadID);
1248 update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
1251 // Initialize a MovePicker object for the current position, and prepare
1252 // to search all moves
1253 mateThreat = pos.has_mate_threat(opposite_color(pos.side_to_move()));
1255 MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
1257 // Loop through all legal moves until no moves remain or a beta cutoff
1259 while ( alpha < beta
1260 && (move = mp.get_next_move()) != MOVE_NONE
1261 && !thread_should_stop(threadID))
1263 assert(move_is_ok(move));
1265 singleEvasion = (isCheck && mp.number_of_evasions() == 1);
1266 moveIsCheck = pos.move_is_check(move, ci);
1267 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1269 // Decide the new search depth
1270 ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1272 // Singular extension search. We extend the TT move if its value is much better than
1273 // its siblings. To verify this we do a reduced search on all the other moves but the
1274 // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
1275 if ( depth >= 6 * OnePly
1277 && move == tte->move()
1279 && is_lower_bound(tte->type())
1280 && tte->depth() >= depth - 3 * OnePly)
1282 Value ttValue = value_from_tt(tte->value(), ply);
1284 if (abs(ttValue) < VALUE_KNOWN_WIN)
1286 Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
1288 if (excValue < ttValue - SingleReplyMargin)
1293 newDepth = depth - OnePly + ext;
1295 // Update current move
1296 movesSearched[moveCount++] = ss[ply].currentMove = move;
1298 // Make and search the move
1299 pos.do_move(move, st, ci, moveIsCheck);
1301 if (moveCount == 1) // The first move in list is the PV
1302 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1305 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1306 // if the move fails high will be re-searched at full depth.
1307 bool doFullDepthSearch = true;
1309 if ( depth >= 3*OnePly
1311 && !captureOrPromotion
1312 && !move_is_castle(move)
1313 && !move_is_killer(move, ss[ply]))
1315 ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 6.0);
1316 if (ss[ply].reduction)
1318 value = -search(pos, ss, -alpha, newDepth-ss[ply].reduction, ply+1, true, threadID);
1319 doFullDepthSearch = (value > alpha);
1323 if (doFullDepthSearch) // Go with full depth non-pv search
1325 ss[ply].reduction = Depth(0);
1326 value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
1327 if (value > alpha && value < beta)
1329 // When the search fails high at ply 1 while searching the first
1330 // move at the root, set the flag failHighPly1. This is used for
1331 // time managment: We don't want to stop the search early in
1332 // such cases, because resolving the fail high at ply 1 could
1333 // result in a big drop in score at the root.
1334 if (ply == 1 && RootMoveNumber == 1)
1335 Threads[threadID].failHighPly1 = true;
1337 // A fail high occurred. Re-search at full window (pv search)
1338 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1339 Threads[threadID].failHighPly1 = false;
1343 pos.undo_move(move);
1345 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1348 if (value > bestValue)
1355 if (value == value_mate_in(ply + 1))
1356 ss[ply].mateKiller = move;
1358 // If we are at ply 1, and we are searching the first root move at
1359 // ply 0, set the 'Problem' variable if the score has dropped a lot
1360 // (from the computer's point of view) since the previous iteration.
1363 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
1368 if ( ActiveThreads > 1
1370 && depth >= MinimumSplitDepth
1372 && idle_thread_exists(threadID)
1374 && !thread_should_stop(threadID)
1375 && split(pos, ss, ply, &alpha, &beta, &bestValue, VALUE_NONE,
1376 depth, &moveCount, &mp, threadID, true))
1380 // All legal moves have been searched. A special case: If there were
1381 // no legal moves, it must be mate or stalemate.
1383 return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
1385 // If the search is not aborted, update the transposition table,
1386 // history counters, and killer moves.
1387 if (AbortSearch || thread_should_stop(threadID))
1390 if (bestValue <= oldAlpha)
1391 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
1393 else if (bestValue >= beta)
1395 BetaCounter.add(pos.side_to_move(), depth, threadID);
1396 move = ss[ply].pv[ply];
1397 if (!pos.move_is_capture_or_promotion(move))
1399 update_history(pos, move, depth, movesSearched, moveCount);
1400 update_killers(move, ss[ply]);
1402 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move);
1405 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]);
1411 // search() is the search function for zero-width nodes.
1413 Value search(Position& pos, SearchStack ss[], Value beta, Depth depth,
1414 int ply, bool allowNullmove, int threadID, Move excludedMove) {
1416 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1417 assert(ply >= 0 && ply < PLY_MAX);
1418 assert(threadID >= 0 && threadID < ActiveThreads);
1420 Move movesSearched[256];
1425 Depth ext, newDepth;
1426 Value bestValue, staticValue, nullValue, value, futilityValue, futilityValueScaled;
1427 bool isCheck, singleEvasion, moveIsCheck, captureOrPromotion, dangerous;
1428 bool mateThreat = false;
1430 futilityValue = staticValue = bestValue = value = -VALUE_INFINITE;
1433 return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1435 // Initialize, and make an early exit in case of an aborted search,
1436 // an instant draw, maximum ply reached, etc.
1437 init_node(ss, ply, threadID);
1439 // After init_node() that calls poll()
1440 if (AbortSearch || thread_should_stop(threadID))
1443 if (pos.is_draw() || ply >= PLY_MAX - 1)
1446 // Mate distance pruning
1447 if (value_mated_in(ply) >= beta)
1450 if (value_mate_in(ply + 1) < beta)
1453 // We don't want the score of a partial search to overwrite a previous full search
1454 // TT value, so we use a different position key in case of an excluded move exsists.
1455 Key posKey = excludedMove ? pos.get_exclusion_key() : pos.get_key();
1457 // Transposition table lookup
1458 tte = TT.retrieve(posKey);
1459 ttMove = (tte ? tte->move() : MOVE_NONE);
1461 if (tte && ok_to_use_TT(tte, depth, beta, ply))
1463 ss[ply].currentMove = ttMove; // Can be MOVE_NONE
1464 return value_from_tt(tte->value(), ply);
1467 isCheck = pos.is_check();
1469 // Calculate depth dependant futility pruning parameters
1470 const int FutilityMoveCountMargin = 3 + (1 << (3 * int(depth) / 8));
1472 // Evaluate the position statically
1475 if (tte && (tte->type() & VALUE_TYPE_EVAL))
1476 staticValue = value_from_tt(tte->value(), ply);
1479 staticValue = evaluate(pos, ei, threadID);
1480 ss[ply].evalInfo = &ei;
1483 ss[ply].eval = staticValue;
1484 futilityValue = staticValue + FutilityMargins[int(depth)]; //FIXME: Remove me, only for split
1485 staticValue = refine_eval(tte, staticValue, ply); // Enhance accuracy with TT value if possible
1486 update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
1489 // Do a "stand pat". If we are above beta by a good margin then
1490 // return immediately.
1491 // FIXME: test with added condition 'allowNullmove || depth <= OnePly' and !value_is_mate(beta)
1492 // FIXME: test with modified condition 'depth < RazorDepth'
1494 && depth < SelectiveDepth
1495 && staticValue - FutilityMargins[int(depth)] >= beta)
1496 return staticValue - FutilityMargins[int(depth)];
1502 && !value_is_mate(beta)
1503 && ok_to_do_nullmove(pos)
1504 && staticValue >= beta - NullMoveMargin)
1506 ss[ply].currentMove = MOVE_NULL;
1508 pos.do_null_move(st);
1510 // Null move dynamic reduction based on depth
1511 int R = 3 + (depth >= 5 * OnePly ? depth / 8 : 0);
1513 // Null move dynamic reduction based on value
1514 if (staticValue - beta > PawnValueMidgame)
1517 nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
1519 pos.undo_null_move();
1521 if (nullValue >= beta)
1523 if (depth < 6 * OnePly)
1526 // Do zugzwang verification search
1527 Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
1531 // The null move failed low, which means that we may be faced with
1532 // some kind of threat. If the previous move was reduced, check if
1533 // the move that refuted the null move was somehow connected to the
1534 // move which was reduced. If a connection is found, return a fail
1535 // low score (which will cause the reduced move to fail high in the
1536 // parent node, which will trigger a re-search with full depth).
1537 if (nullValue == value_mated_in(ply + 2))
1540 ss[ply].threatMove = ss[ply + 1].currentMove;
1541 if ( depth < ThreatDepth
1542 && ss[ply - 1].reduction
1543 && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
1547 // Null move search not allowed, try razoring
1548 else if ( !value_is_mate(beta)
1550 && depth < RazorDepth
1551 && staticValue < beta - (NullMoveMargin + 16 * depth)
1552 && ss[ply - 1].currentMove != MOVE_NULL
1553 && ttMove == MOVE_NONE
1554 && !pos.has_pawn_on_7th(pos.side_to_move()))
1556 Value rbeta = beta - (NullMoveMargin + 16 * depth);
1557 Value v = qsearch(pos, ss, rbeta-1, rbeta, Depth(0), ply, threadID);
1562 // Go with internal iterative deepening if we don't have a TT move
1563 if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
1564 !isCheck && ss[ply].eval >= beta - IIDMargin)
1566 search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
1567 ttMove = ss[ply].pv[ply];
1568 tte = TT.retrieve(pos.get_key());
1571 // Initialize a MovePicker object for the current position, and prepare
1572 // to search all moves.
1573 MovePicker mp = MovePicker(pos, ttMove, depth, H, &ss[ply]);
1576 // Loop through all legal moves until no moves remain or a beta cutoff occurs
1577 while ( bestValue < beta
1578 && (move = mp.get_next_move()) != MOVE_NONE
1579 && !thread_should_stop(threadID))
1581 assert(move_is_ok(move));
1583 if (move == excludedMove)
1586 moveIsCheck = pos.move_is_check(move, ci);
1587 singleEvasion = (isCheck && mp.number_of_evasions() == 1);
1588 captureOrPromotion = pos.move_is_capture_or_promotion(move);
1590 // Decide the new search depth
1591 ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, singleEvasion, mateThreat, &dangerous);
1593 // Singular extension search. We extend the TT move if its value is much better than
1594 // its siblings. To verify this we do a reduced search on all the other moves but the
1595 // ttMove, if result is lower then ttValue minus a margin then we extend ttMove.
1596 if ( depth >= 8 * OnePly
1598 && move == tte->move()
1599 && !excludedMove // Do not allow recursive single-reply search
1601 && is_lower_bound(tte->type())
1602 && tte->depth() >= depth - 3 * OnePly)
1604 Value ttValue = value_from_tt(tte->value(), ply);
1606 if (abs(ttValue) < VALUE_KNOWN_WIN)
1608 Value excValue = search(pos, ss, ttValue - SingleReplyMargin, depth / 2, ply, false, threadID, move);
1610 if (excValue < ttValue - SingleReplyMargin)
1615 newDepth = depth - OnePly + ext;
1617 // Update current move
1618 movesSearched[moveCount++] = ss[ply].currentMove = move;
1620 // Futility pruning for captures
1621 // FIXME: test disabling 'Futility pruning for captures'
1622 // FIXME: test with 'newDepth < RazorDepth'
1623 Color them = opposite_color(pos.side_to_move());
1626 && newDepth < SelectiveDepth
1628 && pos.move_is_capture(move)
1629 && !pos.move_is_check(move, ci)
1630 && !move_is_promotion(move)
1632 && !move_is_ep(move)
1633 && (pos.type_of_piece_on(move_to(move)) != PAWN || !pos.pawn_is_passed(them, move_to(move)))) // Do not prune passed pawn captures
1635 int preFutilityValueMargin = 0;
1637 if (newDepth >= OnePly)
1638 preFutilityValueMargin = FutilityMargins[int(newDepth)];
1640 Value futilityCaptureValue = ss[ply].eval + pos.endgame_value_of_piece_on(move_to(move)) + preFutilityValueMargin + ei.futilityMargin + 90;
1642 if (futilityCaptureValue < beta)
1644 if (futilityCaptureValue > bestValue)
1645 bestValue = futilityCaptureValue;
1653 && !captureOrPromotion
1654 && !move_is_castle(move)
1657 // Move count based pruning
1658 if ( moveCount >= FutilityMoveCountMargin
1659 && ok_to_prune(pos, move, ss[ply].threatMove)
1660 && bestValue > value_mated_in(PLY_MAX))
1663 // Value based pruning
1664 Depth predictedDepth = newDepth;
1666 //FIXME: We are ignoring condition: depth >= 3*OnePly, BUG??
1667 ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 3.0);
1668 if (ss[ply].reduction)
1669 predictedDepth -= ss[ply].reduction;
1671 if (predictedDepth < SelectiveDepth)
1673 int preFutilityValueMargin = 0;
1674 if (predictedDepth >= OnePly)
1675 preFutilityValueMargin = FutilityMargins[int(predictedDepth)];
1677 preFutilityValueMargin += H.gain(pos.piece_on(move_from(move)), move_from(move), move_to(move)) + 45;
1679 futilityValueScaled = ss[ply].eval + preFutilityValueMargin - moveCount * IncrementalFutilityMargin;
1681 if (futilityValueScaled < beta)
1683 if (futilityValueScaled > bestValue)
1684 bestValue = futilityValueScaled;
1690 // Make and search the move
1691 pos.do_move(move, st, ci, moveIsCheck);
1693 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1694 // if the move fails high will be re-searched at full depth.
1695 bool doFullDepthSearch = true;
1697 if ( depth >= 3*OnePly
1699 && !captureOrPromotion
1700 && !move_is_castle(move)
1701 && !move_is_killer(move, ss[ply]))
1703 ss[ply].reduction = calculate_reduction(0.5, moveCount, depth, 3.0);
1704 if (ss[ply].reduction)
1706 value = -search(pos, ss, -(beta-1), newDepth-ss[ply].reduction, ply+1, true, threadID);
1707 doFullDepthSearch = (value >= beta);
1711 if (doFullDepthSearch) // Go with full depth non-pv search
1713 ss[ply].reduction = Depth(0);
1714 value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
1716 pos.undo_move(move);
1718 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1721 if (value > bestValue)
1727 if (value == value_mate_in(ply + 1))
1728 ss[ply].mateKiller = move;
1732 if ( ActiveThreads > 1
1734 && depth >= MinimumSplitDepth
1736 && idle_thread_exists(threadID)
1738 && !thread_should_stop(threadID)
1739 && split(pos, ss, ply, &beta, &beta, &bestValue, futilityValue, //FIXME: SMP & futilityValue
1740 depth, &moveCount, &mp, threadID, false))
1744 // All legal moves have been searched. A special case: If there were
1745 // no legal moves, it must be mate or stalemate.
1747 return excludedMove ? beta - 1 : (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW);
1749 // If the search is not aborted, update the transposition table,
1750 // history counters, and killer moves.
1751 if (AbortSearch || thread_should_stop(threadID))
1754 if (bestValue < beta)
1755 TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
1758 BetaCounter.add(pos.side_to_move(), depth, threadID);
1759 move = ss[ply].pv[ply];
1760 TT.store(posKey, value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, move);
1761 if (!pos.move_is_capture_or_promotion(move))
1763 update_history(pos, move, depth, movesSearched, moveCount);
1764 update_killers(move, ss[ply]);
1769 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1775 // qsearch() is the quiescence search function, which is called by the main
1776 // search function when the remaining depth is zero (or, to be more precise,
1777 // less than OnePly).
1779 Value qsearch(Position& pos, SearchStack ss[], Value alpha, Value beta,
1780 Depth depth, int ply, int threadID) {
1782 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1783 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1785 assert(ply >= 0 && ply < PLY_MAX);
1786 assert(threadID >= 0 && threadID < ActiveThreads);
1791 Value staticValue, bestValue, value, futilityBase, futilityValue;
1792 bool isCheck, enoughMaterial, moveIsCheck, evasionPrunable;
1793 const TTEntry* tte = NULL;
1795 bool pvNode = (beta - alpha != 1);
1797 // Initialize, and make an early exit in case of an aborted search,
1798 // an instant draw, maximum ply reached, etc.
1799 init_node(ss, ply, threadID);
1801 // After init_node() that calls poll()
1802 if (AbortSearch || thread_should_stop(threadID))
1805 if (pos.is_draw() || ply >= PLY_MAX - 1)
1808 // Transposition table lookup. At PV nodes, we don't use the TT for
1809 // pruning, but only for move ordering.
1810 tte = TT.retrieve(pos.get_key());
1811 ttMove = (tte ? tte->move() : MOVE_NONE);
1813 if (!pvNode && tte && ok_to_use_TT(tte, depth, beta, ply))
1815 assert(tte->type() != VALUE_TYPE_EVAL);
1817 ss[ply].currentMove = ttMove; // Can be MOVE_NONE
1818 return value_from_tt(tte->value(), ply);
1821 isCheck = pos.is_check();
1823 // Evaluate the position statically
1825 staticValue = -VALUE_INFINITE;
1826 else if (tte && (tte->type() & VALUE_TYPE_EVAL))
1827 staticValue = value_from_tt(tte->value(), ply);
1829 staticValue = evaluate(pos, ei, threadID);
1833 ss[ply].eval = staticValue;
1834 update_gains(pos, ss[ply - 1].currentMove, ss[ply - 1].eval, ss[ply].eval);
1837 // Initialize "stand pat score", and return it immediately if it is
1839 bestValue = staticValue;
1841 if (bestValue >= beta)
1843 // Store the score to avoid a future costly evaluation() call
1844 if (!isCheck && !tte && ei.futilityMargin == 0)
1845 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EV_LO, Depth(-127*OnePly), MOVE_NONE);
1850 if (bestValue > alpha)
1853 // If we are near beta then try to get a cutoff pushing checks a bit further
1854 bool deepChecks = depth == -OnePly && staticValue >= beta - PawnValueMidgame / 8;
1856 // Initialize a MovePicker object for the current position, and prepare
1857 // to search the moves. Because the depth is <= 0 here, only captures,
1858 // queen promotions and checks (only if depth == 0 or depth == -OnePly
1859 // and we are near beta) will be generated.
1860 MovePicker mp = MovePicker(pos, ttMove, deepChecks ? Depth(0) : depth, H);
1862 enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame;
1863 futilityBase = staticValue + FutilityMarginQS + ei.futilityMargin;
1865 // Loop through the moves until no moves remain or a beta cutoff
1867 while ( alpha < beta
1868 && (move = mp.get_next_move()) != MOVE_NONE)
1870 assert(move_is_ok(move));
1872 moveIsCheck = pos.move_is_check(move, ci);
1874 // Update current move
1876 ss[ply].currentMove = move;
1884 && !move_is_promotion(move)
1885 && !pos.move_is_passed_pawn_push(move))
1887 futilityValue = futilityBase
1888 + pos.endgame_value_of_piece_on(move_to(move))
1889 + (move_is_ep(move) ? PawnValueEndgame : Value(0));
1891 if (futilityValue < alpha)
1893 if (futilityValue > bestValue)
1894 bestValue = futilityValue;
1899 // Detect blocking evasions that are candidate to be pruned
1900 evasionPrunable = isCheck
1901 && bestValue != -VALUE_INFINITE
1902 && !pos.move_is_capture(move)
1903 && pos.type_of_piece_on(move_from(move)) != KING
1904 && !pos.can_castle(pos.side_to_move());
1906 // Don't search moves with negative SEE values
1907 if ( (!isCheck || evasionPrunable)
1909 && !move_is_promotion(move)
1910 && pos.see_sign(move) < 0)
1913 // Make and search the move
1914 pos.do_move(move, st, ci, moveIsCheck);
1915 value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
1916 pos.undo_move(move);
1918 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1921 if (value > bestValue)
1932 // All legal moves have been searched. A special case: If we're in check
1933 // and no legal moves were found, it is checkmate.
1934 if (!moveCount && pos.is_check()) // Mate!
1935 return value_mated_in(ply);
1937 // Update transposition table
1938 Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
1939 if (bestValue < beta)
1941 // If bestValue isn't changed it means it is still the static evaluation
1942 // of the node, so keep this info to avoid a future evaluation() call.
1943 ValueType type = (bestValue == staticValue && !ei.futilityMargin ? VALUE_TYPE_EV_UP : VALUE_TYPE_UPPER);
1944 TT.store(pos.get_key(), value_to_tt(bestValue, ply), type, d, MOVE_NONE);
1948 move = ss[ply].pv[ply];
1949 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, move);
1951 // Update killers only for good checking moves
1952 if (!pos.move_is_capture_or_promotion(move))
1953 update_killers(move, ss[ply]);
1956 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1962 // sp_search() is used to search from a split point. This function is called
1963 // by each thread working at the split point. It is similar to the normal
1964 // search() function, but simpler. Because we have already probed the hash
1965 // table, done a null move search, and searched the first move before
1966 // splitting, we don't have to repeat all this work in sp_search(). We
1967 // also don't need to store anything to the hash table here: This is taken
1968 // care of after we return from the split point.
1970 void sp_search(SplitPoint* sp, int threadID) {
1972 assert(threadID >= 0 && threadID < ActiveThreads);
1973 assert(ActiveThreads > 1);
1975 Position pos(*sp->pos);
1977 SearchStack* ss = sp->sstack[threadID];
1978 Value value = -VALUE_INFINITE;
1981 bool isCheck = pos.is_check();
1982 bool useFutilityPruning = sp->depth < SelectiveDepth
1985 const int FutilityMoveCountMargin = 3 + (1 << (3 * int(sp->depth) / 8));
1987 while ( lock_grab_bool(&(sp->lock))
1988 && sp->bestValue < sp->beta
1989 && !thread_should_stop(threadID)
1990 && (move = sp->mp->get_next_move()) != MOVE_NONE)
1992 moveCount = ++sp->moves;
1993 lock_release(&(sp->lock));
1995 assert(move_is_ok(move));
1997 bool moveIsCheck = pos.move_is_check(move, ci);
1998 bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
2000 ss[sp->ply].currentMove = move;
2002 // Decide the new search depth
2004 Depth ext = extension(pos, move, false, captureOrPromotion, moveIsCheck, false, false, &dangerous);
2005 Depth newDepth = sp->depth - OnePly + ext;
2008 if ( useFutilityPruning
2010 && !captureOrPromotion)
2012 // Move count based pruning
2013 if ( moveCount >= FutilityMoveCountMargin
2014 && ok_to_prune(pos, move, ss[sp->ply].threatMove)
2015 && sp->bestValue > value_mated_in(PLY_MAX))
2018 // Value based pruning
2019 Value futilityValueScaled = sp->futilityValue - moveCount * IncrementalFutilityMargin;
2021 if (futilityValueScaled < sp->beta)
2023 if (futilityValueScaled > sp->bestValue) // Less then 1% of cases
2025 lock_grab(&(sp->lock));
2026 if (futilityValueScaled > sp->bestValue)
2027 sp->bestValue = futilityValueScaled;
2028 lock_release(&(sp->lock));
2034 // Make and search the move.
2036 pos.do_move(move, st, ci, moveIsCheck);
2038 // Try to reduce non-pv search depth by one ply if move seems not problematic,
2039 // if the move fails high will be re-searched at full depth.
2040 bool doFullDepthSearch = true;
2043 && !captureOrPromotion
2044 && !move_is_castle(move)
2045 && !move_is_killer(move, ss[sp->ply]))
2047 ss[sp->ply].reduction = calculate_reduction(0.5, moveCount, sp->depth, 3.0);
2048 if (ss[sp->ply].reduction)
2050 value = -search(pos, ss, -(sp->beta-1), newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
2051 doFullDepthSearch = (value >= sp->beta);
2055 if (doFullDepthSearch) // Go with full depth non-pv search
2057 ss[sp->ply].reduction = Depth(0);
2058 value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
2060 pos.undo_move(move);
2062 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
2064 if (thread_should_stop(threadID))
2066 lock_grab(&(sp->lock));
2071 if (value > sp->bestValue) // Less then 2% of cases
2073 lock_grab(&(sp->lock));
2074 if (value > sp->bestValue && !thread_should_stop(threadID))
2076 sp->bestValue = value;
2077 if (sp->bestValue >= sp->beta)
2079 sp_update_pv(sp->parentSstack, ss, sp->ply);
2080 for (int i = 0; i < ActiveThreads; i++)
2081 if (i != threadID && (i == sp->master || sp->slaves[i]))
2082 Threads[i].stop = true;
2084 sp->finished = true;
2087 lock_release(&(sp->lock));
2091 /* Here we have the lock still grabbed */
2093 // If this is the master thread and we have been asked to stop because of
2094 // a beta cutoff higher up in the tree, stop all slave threads.
2095 if (sp->master == threadID && thread_should_stop(threadID))
2096 for (int i = 0; i < ActiveThreads; i++)
2098 Threads[i].stop = true;
2101 sp->slaves[threadID] = 0;
2103 lock_release(&(sp->lock));
2107 // sp_search_pv() is used to search from a PV split point. This function
2108 // is called by each thread working at the split point. It is similar to
2109 // the normal search_pv() function, but simpler. Because we have already
2110 // probed the hash table and searched the first move before splitting, we
2111 // don't have to repeat all this work in sp_search_pv(). We also don't
2112 // need to store anything to the hash table here: This is taken care of
2113 // after we return from the split point.
2115 void sp_search_pv(SplitPoint* sp, int threadID) {
2117 assert(threadID >= 0 && threadID < ActiveThreads);
2118 assert(ActiveThreads > 1);
2120 Position pos(*sp->pos);
2122 SearchStack* ss = sp->sstack[threadID];
2123 Value value = -VALUE_INFINITE;
2127 while ( lock_grab_bool(&(sp->lock))
2128 && sp->alpha < sp->beta
2129 && !thread_should_stop(threadID)
2130 && (move = sp->mp->get_next_move()) != MOVE_NONE)
2132 moveCount = ++sp->moves;
2133 lock_release(&(sp->lock));
2135 assert(move_is_ok(move));
2137 bool moveIsCheck = pos.move_is_check(move, ci);
2138 bool captureOrPromotion = pos.move_is_capture_or_promotion(move);
2140 ss[sp->ply].currentMove = move;
2142 // Decide the new search depth
2144 Depth ext = extension(pos, move, true, captureOrPromotion, moveIsCheck, false, false, &dangerous);
2145 Depth newDepth = sp->depth - OnePly + ext;
2147 // Make and search the move.
2149 pos.do_move(move, st, ci, moveIsCheck);
2151 // Try to reduce non-pv search depth by one ply if move seems not problematic,
2152 // if the move fails high will be re-searched at full depth.
2153 bool doFullDepthSearch = true;
2156 && !captureOrPromotion
2157 && !move_is_castle(move)
2158 && !move_is_killer(move, ss[sp->ply]))
2160 ss[sp->ply].reduction = calculate_reduction(0.5, moveCount, sp->depth, 6.0);
2161 if (ss[sp->ply].reduction)
2163 Value localAlpha = sp->alpha;
2164 value = -search(pos, ss, -localAlpha, newDepth-ss[sp->ply].reduction, sp->ply+1, true, threadID);
2165 doFullDepthSearch = (value > localAlpha);
2169 if (doFullDepthSearch) // Go with full depth non-pv search
2171 Value localAlpha = sp->alpha;
2172 ss[sp->ply].reduction = Depth(0);
2173 value = -search(pos, ss, -localAlpha, newDepth, sp->ply+1, true, threadID);
2175 if (value > localAlpha && value < sp->beta)
2177 // When the search fails high at ply 1 while searching the first
2178 // move at the root, set the flag failHighPly1. This is used for
2179 // time managment: We don't want to stop the search early in
2180 // such cases, because resolving the fail high at ply 1 could
2181 // result in a big drop in score at the root.
2182 if (sp->ply == 1 && RootMoveNumber == 1)
2183 Threads[threadID].failHighPly1 = true;
2185 // If another thread has failed high then sp->alpha has been increased
2186 // to be higher or equal then beta, if so, avoid to start a PV search.
2187 localAlpha = sp->alpha;
2188 if (localAlpha < sp->beta)
2189 value = -search_pv(pos, ss, -sp->beta, -localAlpha, newDepth, sp->ply+1, threadID);
2191 assert(thread_should_stop(threadID));
2193 Threads[threadID].failHighPly1 = false;
2196 pos.undo_move(move);
2198 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
2200 if (thread_should_stop(threadID))
2202 lock_grab(&(sp->lock));
2207 if (value > sp->bestValue) // Less then 2% of cases
2209 lock_grab(&(sp->lock));
2210 if (value > sp->bestValue && !thread_should_stop(threadID))
2212 sp->bestValue = value;
2213 if (value > sp->alpha)
2215 // Ask threads to stop before to modify sp->alpha
2216 if (value >= sp->beta)
2218 for (int i = 0; i < ActiveThreads; i++)
2219 if (i != threadID && (i == sp->master || sp->slaves[i]))
2220 Threads[i].stop = true;
2222 sp->finished = true;
2227 sp_update_pv(sp->parentSstack, ss, sp->ply);
2228 if (value == value_mate_in(sp->ply + 1))
2229 ss[sp->ply].mateKiller = move;
2231 // If we are at ply 1, and we are searching the first root move at
2232 // ply 0, set the 'Problem' variable if the score has dropped a lot
2233 // (from the computer's point of view) since the previous iteration.
2236 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
2239 lock_release(&(sp->lock));
2243 /* Here we have the lock still grabbed */
2245 // If this is the master thread and we have been asked to stop because of
2246 // a beta cutoff higher up in the tree, stop all slave threads.
2247 if (sp->master == threadID && thread_should_stop(threadID))
2248 for (int i = 0; i < ActiveThreads; i++)
2250 Threads[i].stop = true;
2253 sp->slaves[threadID] = 0;
2255 lock_release(&(sp->lock));
2258 /// The BetaCounterType class
2260 BetaCounterType::BetaCounterType() { clear(); }
2262 void BetaCounterType::clear() {
2264 for (int i = 0; i < THREAD_MAX; i++)
2265 Threads[i].betaCutOffs[WHITE] = Threads[i].betaCutOffs[BLACK] = 0ULL;
2268 void BetaCounterType::add(Color us, Depth d, int threadID) {
2270 // Weighted count based on depth
2271 Threads[threadID].betaCutOffs[us] += unsigned(d);
2274 void BetaCounterType::read(Color us, int64_t& our, int64_t& their) {
2277 for (int i = 0; i < THREAD_MAX; i++)
2279 our += Threads[i].betaCutOffs[us];
2280 their += Threads[i].betaCutOffs[opposite_color(us)];
2285 /// The RootMoveList class
2287 // RootMoveList c'tor
2289 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
2291 MoveStack mlist[MaxRootMoves];
2292 bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
2294 // Generate all legal moves
2295 MoveStack* last = generate_moves(pos, mlist);
2297 // Add each move to the moves[] array
2298 for (MoveStack* cur = mlist; cur != last; cur++)
2300 bool includeMove = includeAllMoves;
2302 for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
2303 includeMove = (searchMoves[k] == cur->move);
2308 // Find a quick score for the move
2310 SearchStack ss[PLY_MAX_PLUS_2];
2313 moves[count].move = cur->move;
2314 pos.do_move(moves[count].move, st);
2315 moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
2316 pos.undo_move(moves[count].move);
2317 moves[count].pv[0] = moves[count].move;
2318 moves[count].pv[1] = MOVE_NONE;
2325 // RootMoveList simple methods definitions
2327 void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
2329 moves[moveNum].nodes = nodes;
2330 moves[moveNum].cumulativeNodes += nodes;
2333 void RootMoveList::set_beta_counters(int moveNum, int64_t our, int64_t their) {
2335 moves[moveNum].ourBeta = our;
2336 moves[moveNum].theirBeta = their;
2339 void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
2343 for (j = 0; pv[j] != MOVE_NONE; j++)
2344 moves[moveNum].pv[j] = pv[j];
2346 moves[moveNum].pv[j] = MOVE_NONE;
2350 // RootMoveList::sort() sorts the root move list at the beginning of a new
2353 void RootMoveList::sort() {
2355 sort_multipv(count - 1); // Sort all items
2359 // RootMoveList::sort_multipv() sorts the first few moves in the root move
2360 // list by their scores and depths. It is used to order the different PVs
2361 // correctly in MultiPV mode.
2363 void RootMoveList::sort_multipv(int n) {
2367 for (i = 1; i <= n; i++)
2369 RootMove rm = moves[i];
2370 for (j = i; j > 0 && moves[j - 1] < rm; j--)
2371 moves[j] = moves[j - 1];
2378 // init_node() is called at the beginning of all the search functions
2379 // (search(), search_pv(), qsearch(), and so on) and initializes the
2380 // search stack object corresponding to the current node. Once every
2381 // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
2382 // for user input and checks whether it is time to stop the search.
2384 void init_node(SearchStack ss[], int ply, int threadID) {
2386 assert(ply >= 0 && ply < PLY_MAX);
2387 assert(threadID >= 0 && threadID < ActiveThreads);
2389 Threads[threadID].nodes++;
2394 if (NodesSincePoll >= NodesBetweenPolls)
2401 ss[ply + 2].initKillers();
2403 if (Threads[threadID].printCurrentLine)
2404 print_current_line(ss, ply, threadID);
2408 // update_pv() is called whenever a search returns a value > alpha.
2409 // It updates the PV in the SearchStack object corresponding to the
2412 void update_pv(SearchStack ss[], int ply) {
2414 assert(ply >= 0 && ply < PLY_MAX);
2418 ss[ply].pv[ply] = ss[ply].currentMove;
2420 for (p = ply + 1; ss[ply + 1].pv[p] != MOVE_NONE; p++)
2421 ss[ply].pv[p] = ss[ply + 1].pv[p];
2423 ss[ply].pv[p] = MOVE_NONE;
2427 // sp_update_pv() is a variant of update_pv for use at split points. The
2428 // difference between the two functions is that sp_update_pv also updates
2429 // the PV at the parent node.
2431 void sp_update_pv(SearchStack* pss, SearchStack ss[], int ply) {
2433 assert(ply >= 0 && ply < PLY_MAX);
2437 ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
2439 for (p = ply + 1; ss[ply + 1].pv[p] != MOVE_NONE; p++)
2440 ss[ply].pv[p] = pss[ply].pv[p] = ss[ply + 1].pv[p];
2442 ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE;
2446 // connected_moves() tests whether two moves are 'connected' in the sense
2447 // that the first move somehow made the second move possible (for instance
2448 // if the moving piece is the same in both moves). The first move is assumed
2449 // to be the move that was made to reach the current position, while the
2450 // second move is assumed to be a move from the current position.
2452 bool connected_moves(const Position& pos, Move m1, Move m2) {
2454 Square f1, t1, f2, t2;
2457 assert(move_is_ok(m1));
2458 assert(move_is_ok(m2));
2460 if (m2 == MOVE_NONE)
2463 // Case 1: The moving piece is the same in both moves
2469 // Case 2: The destination square for m2 was vacated by m1
2475 // Case 3: Moving through the vacated square
2476 if ( piece_is_slider(pos.piece_on(f2))
2477 && bit_is_set(squares_between(f2, t2), f1))
2480 // Case 4: The destination square for m2 is defended by the moving piece in m1
2481 p = pos.piece_on(t1);
2482 if (bit_is_set(pos.attacks_from(p, t1), t2))
2485 // Case 5: Discovered check, checking piece is the piece moved in m1
2486 if ( piece_is_slider(p)
2487 && bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), f2)
2488 && !bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())), t2))
2490 // discovered_check_candidates() works also if the Position's side to
2491 // move is the opposite of the checking piece.
2492 Color them = opposite_color(pos.side_to_move());
2493 Bitboard dcCandidates = pos.discovered_check_candidates(them);
2495 if (bit_is_set(dcCandidates, f2))
2502 // value_is_mate() checks if the given value is a mate one
2503 // eventually compensated for the ply.
2505 bool value_is_mate(Value value) {
2507 assert(abs(value) <= VALUE_INFINITE);
2509 return value <= value_mated_in(PLY_MAX)
2510 || value >= value_mate_in(PLY_MAX);
2514 // move_is_killer() checks if the given move is among the
2515 // killer moves of that ply.
2517 bool move_is_killer(Move m, const SearchStack& ss) {
2519 const Move* k = ss.killers;
2520 for (int i = 0; i < KILLER_MAX; i++, k++)
2528 // extension() decides whether a move should be searched with normal depth,
2529 // or with extended depth. Certain classes of moves (checking moves, in
2530 // particular) are searched with bigger depth than ordinary moves and in
2531 // any case are marked as 'dangerous'. Note that also if a move is not
2532 // extended, as example because the corresponding UCI option is set to zero,
2533 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
2535 Depth extension(const Position& pos, Move m, bool pvNode, bool captureOrPromotion,
2536 bool moveIsCheck, bool singleEvasion, bool mateThreat, bool* dangerous) {
2538 assert(m != MOVE_NONE);
2540 Depth result = Depth(0);
2541 *dangerous = moveIsCheck | singleEvasion | mateThreat;
2546 result += CheckExtension[pvNode];
2549 result += SingleEvasionExtension[pvNode];
2552 result += MateThreatExtension[pvNode];
2555 if (pos.type_of_piece_on(move_from(m)) == PAWN)
2557 Color c = pos.side_to_move();
2558 if (relative_rank(c, move_to(m)) == RANK_7)
2560 result += PawnPushTo7thExtension[pvNode];
2563 if (pos.pawn_is_passed(c, move_to(m)))
2565 result += PassedPawnExtension[pvNode];
2570 if ( captureOrPromotion
2571 && pos.type_of_piece_on(move_to(m)) != PAWN
2572 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
2573 - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
2574 && !move_is_promotion(m)
2577 result += PawnEndgameExtension[pvNode];
2582 && captureOrPromotion
2583 && pos.type_of_piece_on(move_to(m)) != PAWN
2584 && pos.see_sign(m) >= 0)
2590 return Min(result, OnePly);
2594 // ok_to_do_nullmove() looks at the current position and decides whether
2595 // doing a 'null move' should be allowed. In order to avoid zugzwang
2596 // problems, null moves are not allowed when the side to move has very
2597 // little material left. Currently, the test is a bit too simple: Null
2598 // moves are avoided only when the side to move has only pawns left.
2599 // It's probably a good idea to avoid null moves in at least some more
2600 // complicated endgames, e.g. KQ vs KR. FIXME
2602 bool ok_to_do_nullmove(const Position& pos) {
2604 return pos.non_pawn_material(pos.side_to_move()) != Value(0);
2608 // ok_to_prune() tests whether it is safe to forward prune a move. Only
2609 // non-tactical moves late in the move list close to the leaves are
2610 // candidates for pruning.
2612 bool ok_to_prune(const Position& pos, Move m, Move threat) {
2614 assert(move_is_ok(m));
2615 assert(threat == MOVE_NONE || move_is_ok(threat));
2616 assert(!pos.move_is_check(m));
2617 assert(!pos.move_is_capture_or_promotion(m));
2618 assert(!pos.move_is_passed_pawn_push(m));
2620 Square mfrom, mto, tfrom, tto;
2622 // Prune if there isn't any threat move
2623 if (threat == MOVE_NONE)
2626 mfrom = move_from(m);
2628 tfrom = move_from(threat);
2629 tto = move_to(threat);
2631 // Case 1: Don't prune moves which move the threatened piece
2635 // Case 2: If the threatened piece has value less than or equal to the
2636 // value of the threatening piece, don't prune move which defend it.
2637 if ( pos.move_is_capture(threat)
2638 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
2639 || pos.type_of_piece_on(tfrom) == KING)
2640 && pos.move_attacks_square(m, tto))
2643 // Case 3: If the moving piece in the threatened move is a slider, don't
2644 // prune safe moves which block its ray.
2645 if ( piece_is_slider(pos.piece_on(tfrom))
2646 && bit_is_set(squares_between(tfrom, tto), mto)
2647 && pos.see_sign(m) >= 0)
2654 // ok_to_use_TT() returns true if a transposition table score
2655 // can be used at a given point in search.
2657 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
2659 Value v = value_from_tt(tte->value(), ply);
2661 return ( tte->depth() >= depth
2662 || v >= Max(value_mate_in(PLY_MAX), beta)
2663 || v < Min(value_mated_in(PLY_MAX), beta))
2665 && ( (is_lower_bound(tte->type()) && v >= beta)
2666 || (is_upper_bound(tte->type()) && v < beta));
2670 // refine_eval() returns the transposition table score if
2671 // possible otherwise falls back on static position evaluation.
2673 Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) {
2678 Value v = value_from_tt(tte->value(), ply);
2680 if ( (is_lower_bound(tte->type()) && v >= defaultEval)
2681 || (is_upper_bound(tte->type()) && v < defaultEval))
2687 // calculate_reduction() returns reduction in plies based on
2688 // moveCount and depth. Reduction is always at least one ply.
2690 Depth calculate_reduction(double baseReduction, int moveCount, Depth depth, double reductionInhibitor) {
2692 double red = baseReduction + ln(moveCount) * ln(depth / 2) / reductionInhibitor;
2695 return Depth(int(floor(red * int(OnePly))));
2701 // update_history() registers a good move that produced a beta-cutoff
2702 // in history and marks as failures all the other moves of that ply.
2704 void update_history(const Position& pos, Move move, Depth depth,
2705 Move movesSearched[], int moveCount) {
2709 H.success(pos.piece_on(move_from(move)), move_to(move), depth);
2711 for (int i = 0; i < moveCount - 1; i++)
2713 m = movesSearched[i];
2717 if (!pos.move_is_capture_or_promotion(m))
2718 H.failure(pos.piece_on(move_from(m)), move_to(m), depth);
2723 // update_killers() add a good move that produced a beta-cutoff
2724 // among the killer moves of that ply.
2726 void update_killers(Move m, SearchStack& ss) {
2728 if (m == ss.killers[0])
2731 for (int i = KILLER_MAX - 1; i > 0; i--)
2732 ss.killers[i] = ss.killers[i - 1];
2738 // update_gains() updates the gains table of a non-capture move given
2739 // the static position evaluation before and after the move.
2741 void update_gains(const Position& pos, Move m, Value before, Value after) {
2744 && before != VALUE_NONE
2745 && after != VALUE_NONE
2746 && pos.captured_piece() == NO_PIECE_TYPE
2747 && !move_is_castle(m)
2748 && !move_is_promotion(m))
2749 H.set_gain(pos.piece_on(move_to(m)), move_from(m), move_to(m), -(before + after));
2753 // fail_high_ply_1() checks if some thread is currently resolving a fail
2754 // high at ply 1 at the node below the first root node. This information
2755 // is used for time management.
2757 bool fail_high_ply_1() {
2759 for (int i = 0; i < ActiveThreads; i++)
2760 if (Threads[i].failHighPly1)
2767 // current_search_time() returns the number of milliseconds which have passed
2768 // since the beginning of the current search.
2770 int current_search_time() {
2772 return get_system_time() - SearchStartTime;
2776 // nps() computes the current nodes/second count.
2780 int t = current_search_time();
2781 return (t > 0 ? int((nodes_searched() * 1000) / t) : 0);
2785 // poll() performs two different functions: It polls for user input, and it
2786 // looks at the time consumed so far and decides if it's time to abort the
2791 static int lastInfoTime;
2792 int t = current_search_time();
2797 // We are line oriented, don't read single chars
2798 std::string command;
2800 if (!std::getline(std::cin, command))
2803 if (command == "quit")
2806 PonderSearch = false;
2810 else if (command == "stop")
2813 PonderSearch = false;
2815 else if (command == "ponderhit")
2819 // Print search information
2823 else if (lastInfoTime > t)
2824 // HACK: Must be a new search where we searched less than
2825 // NodesBetweenPolls nodes during the first second of search.
2828 else if (t - lastInfoTime >= 1000)
2836 if (dbg_show_hit_rate)
2837 dbg_print_hit_rate();
2839 cout << "info nodes " << nodes_searched() << " nps " << nps()
2840 << " time " << t << " hashfull " << TT.full() << endl;
2842 lock_release(&IOLock);
2844 if (ShowCurrentLine)
2845 Threads[0].printCurrentLine = true;
2848 // Should we stop the search?
2852 bool stillAtFirstMove = RootMoveNumber == 1
2854 && t > MaxSearchTime + ExtraSearchTime;
2856 bool noProblemFound = !FailHigh
2858 && !fail_high_ply_1()
2860 && t > 6 * (MaxSearchTime + ExtraSearchTime);
2862 bool noMoreTime = t > AbsoluteMaxSearchTime
2863 || stillAtFirstMove //FIXME: We are not checking any problem flags, BUG?
2866 if ( (Iteration >= 3 && UseTimeManagement && noMoreTime)
2867 || (ExactMaxTime && t >= ExactMaxTime)
2868 || (Iteration >= 3 && MaxNodes && nodes_searched() >= MaxNodes))
2873 // ponderhit() is called when the program is pondering (i.e. thinking while
2874 // it's the opponent's turn to move) in order to let the engine know that
2875 // it correctly predicted the opponent's move.
2879 int t = current_search_time();
2880 PonderSearch = false;
2882 bool stillAtFirstMove = RootMoveNumber == 1
2884 && t > MaxSearchTime + ExtraSearchTime;
2886 bool noProblemFound = !FailHigh
2888 && !fail_high_ply_1()
2890 && t > 6 * (MaxSearchTime + ExtraSearchTime);
2892 bool noMoreTime = t > AbsoluteMaxSearchTime
2896 if (Iteration >= 3 && UseTimeManagement && (noMoreTime || StopOnPonderhit))
2901 // print_current_line() prints the current line of search for a given
2902 // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
2904 void print_current_line(SearchStack ss[], int ply, int threadID) {
2906 assert(ply >= 0 && ply < PLY_MAX);
2907 assert(threadID >= 0 && threadID < ActiveThreads);
2909 if (!Threads[threadID].idle)
2912 cout << "info currline " << (threadID + 1);
2913 for (int p = 0; p < ply; p++)
2914 cout << " " << ss[p].currentMove;
2917 lock_release(&IOLock);
2919 Threads[threadID].printCurrentLine = false;
2920 if (threadID + 1 < ActiveThreads)
2921 Threads[threadID + 1].printCurrentLine = true;
2925 // init_ss_array() does a fast reset of the first entries of a SearchStack array
2927 void init_ss_array(SearchStack ss[]) {
2929 for (int i = 0; i < 3; i++)
2932 ss[i].initKillers();
2937 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2938 // while the program is pondering. The point is to work around a wrinkle in
2939 // the UCI protocol: When pondering, the engine is not allowed to give a
2940 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2941 // We simply wait here until one of these commands is sent, and return,
2942 // after which the bestmove and pondermove will be printed (in id_loop()).
2944 void wait_for_stop_or_ponderhit() {
2946 std::string command;
2950 if (!std::getline(std::cin, command))
2953 if (command == "quit")
2958 else if (command == "ponderhit" || command == "stop")
2964 // idle_loop() is where the threads are parked when they have no work to do.
2965 // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
2966 // object for which the current thread is the master.
2968 void idle_loop(int threadID, SplitPoint* waitSp) {
2970 assert(threadID >= 0 && threadID < THREAD_MAX);
2972 Threads[threadID].running = true;
2976 if (AllThreadsShouldExit && threadID != 0)
2979 // If we are not thinking, wait for a condition to be signaled
2980 // instead of wasting CPU time polling for work.
2981 while (threadID != 0 && (Idle || threadID >= ActiveThreads))
2984 #if !defined(_MSC_VER)
2985 pthread_mutex_lock(&WaitLock);
2986 if (Idle || threadID >= ActiveThreads)
2987 pthread_cond_wait(&WaitCond, &WaitLock);
2989 pthread_mutex_unlock(&WaitLock);
2991 WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
2995 // If this thread has been assigned work, launch a search
2996 if (Threads[threadID].workIsWaiting)
2998 assert(!Threads[threadID].idle);
3000 Threads[threadID].workIsWaiting = false;
3001 if (Threads[threadID].splitPoint->pvNode)
3002 sp_search_pv(Threads[threadID].splitPoint, threadID);
3004 sp_search(Threads[threadID].splitPoint, threadID);
3006 Threads[threadID].idle = true;
3009 // If this thread is the master of a split point and all threads have
3010 // finished their work at this split point, return from the idle loop.
3011 if (waitSp != NULL && waitSp->cpus == 0)
3015 Threads[threadID].running = false;
3019 // init_split_point_stack() is called during program initialization, and
3020 // initializes all split point objects.
3022 void init_split_point_stack() {
3024 for (int i = 0; i < THREAD_MAX; i++)
3025 for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++)
3027 SplitPointStack[i][j].parent = NULL;
3028 lock_init(&(SplitPointStack[i][j].lock), NULL);
3033 // destroy_split_point_stack() is called when the program exits, and
3034 // destroys all locks in the precomputed split point objects.
3036 void destroy_split_point_stack() {
3038 for (int i = 0; i < THREAD_MAX; i++)
3039 for (int j = 0; j < ACTIVE_SPLIT_POINTS_MAX; j++)
3040 lock_destroy(&(SplitPointStack[i][j].lock));
3044 // thread_should_stop() checks whether the thread with a given threadID has
3045 // been asked to stop, directly or indirectly. This can happen if a beta
3046 // cutoff has occurred in the thread's currently active split point, or in
3047 // some ancestor of the current split point.
3049 bool thread_should_stop(int threadID) {
3051 assert(threadID >= 0 && threadID < ActiveThreads);
3055 if (Threads[threadID].stop)
3057 if (ActiveThreads <= 2)
3059 for (sp = Threads[threadID].splitPoint; sp != NULL; sp = sp->parent)
3062 Threads[threadID].stop = true;
3069 // thread_is_available() checks whether the thread with threadID "slave" is
3070 // available to help the thread with threadID "master" at a split point. An
3071 // obvious requirement is that "slave" must be idle. With more than two
3072 // threads, this is not by itself sufficient: If "slave" is the master of
3073 // some active split point, it is only available as a slave to the other
3074 // threads which are busy searching the split point at the top of "slave"'s
3075 // split point stack (the "helpful master concept" in YBWC terminology).
3077 bool thread_is_available(int slave, int master) {
3079 assert(slave >= 0 && slave < ActiveThreads);
3080 assert(master >= 0 && master < ActiveThreads);
3081 assert(ActiveThreads > 1);
3083 if (!Threads[slave].idle || slave == master)
3086 // Make a local copy to be sure doesn't change under our feet
3087 int localActiveSplitPoints = Threads[slave].activeSplitPoints;
3089 if (localActiveSplitPoints == 0)
3090 // No active split points means that the thread is available as
3091 // a slave for any other thread.
3094 if (ActiveThreads == 2)
3097 // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
3098 // that is known to be > 0, instead of Threads[slave].activeSplitPoints that
3099 // could have been set to 0 by another thread leading to an out of bound access.
3100 if (SplitPointStack[slave][localActiveSplitPoints - 1].slaves[master])
3107 // idle_thread_exists() tries to find an idle thread which is available as
3108 // a slave for the thread with threadID "master".
3110 bool idle_thread_exists(int master) {
3112 assert(master >= 0 && master < ActiveThreads);
3113 assert(ActiveThreads > 1);
3115 for (int i = 0; i < ActiveThreads; i++)
3116 if (thread_is_available(i, master))
3123 // split() does the actual work of distributing the work at a node between
3124 // several threads at PV nodes. If it does not succeed in splitting the
3125 // node (because no idle threads are available, or because we have no unused
3126 // split point objects), the function immediately returns false. If
3127 // splitting is possible, a SplitPoint object is initialized with all the
3128 // data that must be copied to the helper threads (the current position and
3129 // search stack, alpha, beta, the search depth, etc.), and we tell our
3130 // helper threads that they have been assigned work. This will cause them
3131 // to instantly leave their idle loops and call sp_search_pv(). When all
3132 // threads have returned from sp_search_pv (or, equivalently, when
3133 // splitPoint->cpus becomes 0), split() returns true.
3135 bool split(const Position& p, SearchStack* sstck, int ply,
3136 Value* alpha, Value* beta, Value* bestValue, const Value futilityValue,
3137 Depth depth, int* moves, MovePicker* mp, int master, bool pvNode) {
3140 assert(sstck != NULL);
3141 assert(ply >= 0 && ply < PLY_MAX);
3142 assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha);
3143 assert(!pvNode || *alpha < *beta);
3144 assert(*beta <= VALUE_INFINITE);
3145 assert(depth > Depth(0));
3146 assert(master >= 0 && master < ActiveThreads);
3147 assert(ActiveThreads > 1);
3149 SplitPoint* splitPoint;
3153 // If no other thread is available to help us, or if we have too many
3154 // active split points, don't split.
3155 if ( !idle_thread_exists(master)
3156 || Threads[master].activeSplitPoints >= ACTIVE_SPLIT_POINTS_MAX)
3158 lock_release(&MPLock);
3162 // Pick the next available split point object from the split point stack
3163 splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
3164 Threads[master].activeSplitPoints++;
3166 // Initialize the split point object
3167 splitPoint->parent = Threads[master].splitPoint;
3168 splitPoint->finished = false;
3169 splitPoint->ply = ply;
3170 splitPoint->depth = depth;
3171 splitPoint->alpha = pvNode ? *alpha : (*beta - 1);
3172 splitPoint->beta = *beta;
3173 splitPoint->pvNode = pvNode;
3174 splitPoint->bestValue = *bestValue;
3175 splitPoint->futilityValue = futilityValue;
3176 splitPoint->master = master;
3177 splitPoint->mp = mp;
3178 splitPoint->moves = *moves;
3179 splitPoint->cpus = 1;
3180 splitPoint->pos = &p;
3181 splitPoint->parentSstack = sstck;
3182 for (int i = 0; i < ActiveThreads; i++)
3183 splitPoint->slaves[i] = 0;
3185 Threads[master].idle = false;
3186 Threads[master].stop = false;
3187 Threads[master].splitPoint = splitPoint;
3189 // Allocate available threads setting idle flag to false
3190 for (int i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint; i++)
3191 if (thread_is_available(i, master))
3193 Threads[i].idle = false;
3194 Threads[i].stop = false;
3195 Threads[i].splitPoint = splitPoint;
3196 splitPoint->slaves[i] = 1;
3200 assert(splitPoint->cpus > 1);
3202 // We can release the lock because master and slave threads are already booked
3203 lock_release(&MPLock);
3205 // Tell the threads that they have work to do. This will make them leave
3206 // their idle loop. But before copy search stack tail for each thread.
3207 for (int i = 0; i < ActiveThreads; i++)
3208 if (i == master || splitPoint->slaves[i])
3210 memcpy(splitPoint->sstack[i] + ply - 1, sstck + ply - 1, 3 * sizeof(SearchStack));
3211 Threads[i].workIsWaiting = true; // This makes the slave to exit from idle_loop()
3214 // Everything is set up. The master thread enters the idle loop, from
3215 // which it will instantly launch a search, because its workIsWaiting
3216 // slot is 'true'. We send the split point as a second parameter to the
3217 // idle loop, which means that the main thread will return from the idle
3218 // loop when all threads have finished their work at this split point
3219 // (i.e. when splitPoint->cpus == 0).
3220 idle_loop(master, splitPoint);
3222 // We have returned from the idle loop, which means that all threads are
3223 // finished. Update alpha, beta and bestValue, and return.
3227 *alpha = splitPoint->alpha;
3229 *beta = splitPoint->beta;
3230 *bestValue = splitPoint->bestValue;
3231 Threads[master].stop = false;
3232 Threads[master].idle = false;
3233 Threads[master].activeSplitPoints--;
3234 Threads[master].splitPoint = splitPoint->parent;
3236 lock_release(&MPLock);
3241 // wake_sleeping_threads() wakes up all sleeping threads when it is time
3242 // to start a new search from the root.
3244 void wake_sleeping_threads() {
3246 if (ActiveThreads > 1)
3248 for (int i = 1; i < ActiveThreads; i++)
3250 Threads[i].idle = true;
3251 Threads[i].workIsWaiting = false;
3254 #if !defined(_MSC_VER)
3255 pthread_mutex_lock(&WaitLock);
3256 pthread_cond_broadcast(&WaitCond);
3257 pthread_mutex_unlock(&WaitLock);
3259 for (int i = 1; i < THREAD_MAX; i++)
3260 SetEvent(SitIdleEvent[i]);
3266 // init_thread() is the function which is called when a new thread is
3267 // launched. It simply calls the idle_loop() function with the supplied
3268 // threadID. There are two versions of this function; one for POSIX
3269 // threads and one for Windows threads.
3271 #if !defined(_MSC_VER)
3273 void* init_thread(void *threadID) {
3275 idle_loop(*(int*)threadID, NULL);
3281 DWORD WINAPI init_thread(LPVOID threadID) {
3283 idle_loop(*(int*)threadID, NULL);