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 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/>.
40 #include "ucioption.h"
44 //// Local definitions
51 // IterationInfoType stores search results for each iteration
53 // Because we use relatively small (dynamic) aspiration window,
54 // there happens many fail highs and fail lows in root. And
55 // because we don't do researches in those cases, "value" stored
56 // here is not necessarily exact. Instead in case of fail high/low
57 // we guess what the right value might be and store our guess
58 // as a "speculated value" and then move on. Speculated values are
59 // used just to calculate aspiration window width, so also if are
60 // not exact is not big a problem.
62 struct IterationInfoType {
64 IterationInfoType(Value v = Value(0), Value sv = Value(0))
65 : value(v), speculatedValue(sv) {}
67 Value value, speculatedValue;
71 // The BetaCounterType class is used to order moves at ply one.
72 // Apart for the first one that has its score, following moves
73 // normally have score -VALUE_INFINITE, so are ordered according
74 // to the number of beta cutoffs occurred under their subtree during
75 // the last iteration.
77 struct BetaCounterType {
81 void add(Color us, Depth d, int threadID);
82 void read(Color us, int64_t& our, int64_t& their);
84 int64_t hits[THREAD_MAX][2];
88 // The RootMove class is used for moves at the root at the tree. For each
89 // root move, we store a score, a node count, and a PV (really a refutation
90 // in the case of moves which fail low).
95 bool operator<(const RootMove&); // used to sort
99 int64_t nodes, cumulativeNodes;
100 Move pv[PLY_MAX_PLUS_2];
101 int64_t ourBeta, theirBeta;
105 // The RootMoveList class is essentially an array of RootMove objects, with
106 // a handful of methods for accessing the data in the individual moves.
111 RootMoveList(Position &pos, Move searchMoves[]);
112 inline Move get_move(int moveNum) const;
113 inline Value get_move_score(int moveNum) const;
114 inline void set_move_score(int moveNum, Value score);
115 inline void set_move_nodes(int moveNum, int64_t nodes);
116 inline void set_beta_counters(int moveNum, int64_t our, int64_t their);
117 void set_move_pv(int moveNum, const Move pv[]);
118 inline Move get_move_pv(int moveNum, int i) const;
119 inline int64_t get_move_cumulative_nodes(int moveNum) const;
120 inline int move_count() const;
121 Move scan_for_easy_move() const;
123 void sort_multipv(int n);
126 static const int MaxRootMoves = 500;
127 RootMove moves[MaxRootMoves];
132 /// Constants and variables initialized from UCI options
134 // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
136 int LMRPVMoves, LMRNonPVMoves;
138 // Depth limit for use of dynamic threat detection
141 // Depth limit for selective search
142 Depth SelectiveDepth;
144 // Use internal iterative deepening?
145 const bool UseIIDAtPVNodes = true;
146 const bool UseIIDAtNonPVNodes = false;
148 // Internal iterative deepening margin. At Non-PV moves, when
149 // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
150 // when the static evaluation is at most IIDMargin below beta.
151 const Value IIDMargin = Value(0x100);
153 // Easy move margin. An easy move candidate must be at least this much
154 // better than the second best move.
155 const Value EasyMoveMargin = Value(0x200);
157 // Problem margin. If the score of the first move at iteration N+1 has
158 // dropped by more than this since iteration N, the boolean variable
159 // "Problem" is set to true, which will make the program spend some extra
160 // time looking for a better move.
161 const Value ProblemMargin = Value(0x28);
163 // No problem margin. If the boolean "Problem" is true, and a new move
164 // is found at the root which is less than NoProblemMargin worse than the
165 // best move from the previous iteration, Problem is set back to false.
166 const Value NoProblemMargin = Value(0x14);
168 // Null move margin. A null move search will not be done if the approximate
169 // evaluation of the position is more than NullMoveMargin below beta.
170 const Value NullMoveMargin = Value(0x300);
172 // Pruning criterions. See the code and comments in ok_to_prune() to
173 // understand their precise meaning.
174 const bool PruneEscapeMoves = false;
175 const bool PruneDefendingMoves = false;
176 const bool PruneBlockingMoves = false;
178 // Use futility pruning?
179 bool UseQSearchFutilityPruning, UseFutilityPruning;
181 // Margins for futility pruning in the quiescence search, and at frontier
182 // and near frontier nodes
183 const Value FutilityMarginQS = Value(0x80);
185 //remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
186 const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270),
187 // 4 ply 4.5 ply 5 ply 5.5 ply 6 ply 6.5 ply
188 Value(0x2A0), Value(0x2C0), Value(0x340), Value(0x360), Value(0x3A0), Value(0x3C0)};
191 const Depth RazorDepth = 4*OnePly;
193 //remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
194 const Value RazorMargins[6] = { Value(0x180), Value(0x300), Value(0x300), Value(0x3C0), Value(0x3C0), Value(0x3C0) };
196 //remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
197 const Value RazorApprMargins[6] = { Value(0x100000), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
199 // Last seconds noise filtering (LSN)
200 bool UseLSNFiltering;
201 bool looseOnTime = false;
202 int LSNTime; // In milliseconds
205 // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
206 Depth CheckExtension[2], SingleReplyExtension[2], PawnPushTo7thExtension[2];
207 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
209 // Search depth at iteration 1
210 const Depth InitialDepth = OnePly /*+ OnePly/2*/;
214 int NodesBetweenPolls = 30000;
216 // Iteration counters
218 BetaCounterType BetaCounter;
220 // Scores and number of times the best move changed for each iteration:
221 IterationInfoType IterationInfo[PLY_MAX_PLUS_2];
222 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
227 // Time managment variables
229 int MaxNodes, MaxDepth;
230 int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
235 bool StopOnPonderhit;
241 bool PonderingEnabled;
244 // Show current line?
245 bool ShowCurrentLine;
249 std::ofstream LogFile;
251 // MP related variables
252 Depth MinimumSplitDepth;
253 int MaxThreadsPerSplitPoint;
254 Thread Threads[THREAD_MAX];
256 bool AllThreadsShouldExit = false;
257 const int MaxActiveSplitPoints = 8;
258 SplitPoint SplitPointStack[THREAD_MAX][MaxActiveSplitPoints];
261 #if !defined(_MSC_VER)
262 pthread_cond_t WaitCond;
263 pthread_mutex_t WaitLock;
265 HANDLE SitIdleEvent[THREAD_MAX];
271 Value id_loop(const Position &pos, Move searchMoves[]);
272 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta);
273 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
274 Value search(Position &pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID);
275 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
276 void sp_search(SplitPoint *sp, int threadID);
277 void sp_search_pv(SplitPoint *sp, int threadID);
278 void init_node(SearchStack ss[], int ply, int threadID);
279 void update_pv(SearchStack ss[], int ply);
280 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
281 bool connected_moves(const Position &pos, Move m1, Move m2);
282 bool value_is_mate(Value value);
283 bool move_is_killer(Move m, const SearchStack& ss);
284 Depth extension(const Position &pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
285 bool ok_to_do_nullmove(const Position &pos);
286 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
287 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
288 bool ok_to_history(const Position &pos, Move m);
289 void update_history(const Position& pos, Move m, Depth depth, Move movesSearched[], int moveCount);
290 void update_killers(Move m, SearchStack& ss);
292 bool fail_high_ply_1();
293 int current_search_time();
297 void print_current_line(SearchStack ss[], int ply, int threadID);
298 void wait_for_stop_or_ponderhit();
300 void idle_loop(int threadID, SplitPoint *waitSp);
301 void init_split_point_stack();
302 void destroy_split_point_stack();
303 bool thread_should_stop(int threadID);
304 bool thread_is_available(int slave, int master);
305 bool idle_thread_exists(int master);
306 bool split(const Position &pos, SearchStack *ss, int ply,
307 Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
308 MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode);
309 void wake_sleeping_threads();
311 #if !defined(_MSC_VER)
312 void *init_thread(void *threadID);
314 DWORD WINAPI init_thread(LPVOID threadID);
321 //// Global variables
324 // The main transposition table
325 TranspositionTable TT = TranspositionTable(TTDefaultSize);
328 // Number of active threads:
329 int ActiveThreads = 1;
331 // Locks. In principle, there is no need for IOLock to be a global variable,
332 // but it could turn out to be useful for debugging.
335 History H; // Should be made local?
337 // The empty search stack
338 SearchStack EmptySearchStack;
341 // SearchStack::init() initializes a search stack. Used at the beginning of a
342 // new search from the root.
343 void SearchStack::init(int ply) {
345 pv[ply] = pv[ply + 1] = MOVE_NONE;
346 currentMove = threatMove = MOVE_NONE;
347 reduction = Depth(0);
350 void SearchStack::initKillers() {
352 mateKiller = MOVE_NONE;
353 for (int i = 0; i < KILLER_MAX; i++)
354 killers[i] = MOVE_NONE;
362 /// think() is the external interface to Stockfish's search, and is called when
363 /// the program receives the UCI 'go' command. It initializes various
364 /// search-related global variables, and calls root_search()
366 void 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 // Look for a book move
371 if (!infinite && !ponder && get_option_value_bool("OwnBook"))
374 if (get_option_value_string("Book File") != OpeningBook.file_name())
377 OpeningBook.open("book.bin");
379 bookMove = OpeningBook.get_move(pos);
380 if (bookMove != MOVE_NONE)
382 std::cout << "bestmove " << bookMove << std::endl;
387 // Initialize global search variables
389 SearchStartTime = get_system_time();
390 EasyMove = MOVE_NONE;
391 for (int i = 0; i < THREAD_MAX; i++)
393 Threads[i].nodes = 0ULL;
394 Threads[i].failHighPly1 = false;
397 InfiniteSearch = infinite;
398 PonderSearch = ponder;
399 StopOnPonderhit = false;
405 ExactMaxTime = maxTime;
407 // Read UCI option values
408 TT.set_size(get_option_value_int("Hash"));
409 if (button_was_pressed("Clear Hash"))
412 PonderingEnabled = get_option_value_bool("Ponder");
413 MultiPV = get_option_value_int("MultiPV");
415 CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
416 CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)"));
418 SingleReplyExtension[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)"));
419 SingleReplyExtension[0] = Depth(get_option_value_int("Single Reply Extension (non-PV nodes)"));
421 PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
422 PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
424 PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
425 PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
427 PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
428 PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
430 MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
431 MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
433 LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
434 LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
435 ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
436 SelectiveDepth = get_option_value_int("Selective Plies") * OnePly;
438 Chess960 = get_option_value_bool("UCI_Chess960");
439 ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
440 UseLogFile = get_option_value_bool("Use Search Log");
442 LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
444 UseQSearchFutilityPruning = get_option_value_bool("Futility Pruning (Quiescence Search)");
445 UseFutilityPruning = get_option_value_bool("Futility Pruning (Main Search)");
447 //FutilityMarginQS = value_from_centipawns(get_option_value_int("Futility Margin (Quiescence Search)"));
448 //int fmScale = get_option_value_int("Futility Margin Scale Factor (Main Search)");
449 //for (int i = 0; i < 6; i++)
450 // FutilityMargins[i] = (FutilityMargins[i] * fmScale) / 100;
452 //RazorDepth = (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly;
453 //RazorMargin = value_from_centipawns(get_option_value_int("Razoring Margin"));
455 UseLSNFiltering = get_option_value_bool("LSN filtering");
456 LSNTime = get_option_value_int("LSN Time Margin (sec)") * 1000;
457 LSNValue = value_from_centipawns(get_option_value_int("LSN Value Margin"));
459 MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
460 MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point");
462 read_weights(pos.side_to_move());
464 int newActiveThreads = get_option_value_int("Threads");
465 if (newActiveThreads != ActiveThreads)
467 ActiveThreads = newActiveThreads;
468 init_eval(ActiveThreads);
471 // Wake up sleeping threads:
472 wake_sleeping_threads();
474 for (int i = 1; i < ActiveThreads; i++)
475 assert(thread_is_available(i, 0));
477 // Set thinking time:
478 int myTime = time[side_to_move];
479 int myIncrement = increment[side_to_move];
481 if (!movesToGo) // Sudden death time control
485 MaxSearchTime = myTime / 30 + myIncrement;
486 AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
487 } else { // Blitz game without increment
488 MaxSearchTime = myTime / 30;
489 AbsoluteMaxSearchTime = myTime / 8;
492 else // (x moves) / (y minutes)
496 MaxSearchTime = myTime / 2;
497 AbsoluteMaxSearchTime = Min(myTime / 2, myTime - 500);
499 MaxSearchTime = myTime / Min(movesToGo, 20);
500 AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3);
504 if (PonderingEnabled)
506 MaxSearchTime += MaxSearchTime / 4;
507 MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
510 // Fixed depth or fixed number of nodes?
513 InfiniteSearch = true; // HACK
518 NodesBetweenPolls = Min(MaxNodes, 30000);
519 InfiniteSearch = true; // HACK
522 NodesBetweenPolls = 30000;
525 // Write information to search log file:
527 LogFile << "Searching: " << pos.to_fen() << std::endl
528 << "infinite: " << infinite
529 << " ponder: " << ponder
530 << " time: " << myTime
531 << " increment: " << myIncrement
532 << " moves to go: " << movesToGo << std::endl;
535 // We're ready to start thinking. Call the iterative deepening loop
539 Value v = id_loop(pos, searchMoves);
540 looseOnTime = ( UseLSNFiltering
547 looseOnTime = false; // reset for next match
548 while (SearchStartTime + myTime + 1000 > get_system_time())
550 id_loop(pos, searchMoves); // to fail gracefully
567 /// init_threads() is called during startup. It launches all helper threads,
568 /// and initializes the split point stack and the global locks and condition
571 void init_threads() {
575 #if !defined(_MSC_VER)
576 pthread_t pthread[1];
579 for (i = 0; i < THREAD_MAX; i++)
580 Threads[i].activeSplitPoints = 0;
582 // Initialize global locks:
583 lock_init(&MPLock, NULL);
584 lock_init(&IOLock, NULL);
586 init_split_point_stack();
588 #if !defined(_MSC_VER)
589 pthread_mutex_init(&WaitLock, NULL);
590 pthread_cond_init(&WaitCond, NULL);
592 for (i = 0; i < THREAD_MAX; i++)
593 SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
596 // All threads except the main thread should be initialized to idle state
597 for (i = 1; i < THREAD_MAX; i++)
599 Threads[i].stop = false;
600 Threads[i].workIsWaiting = false;
601 Threads[i].idle = true;
602 Threads[i].running = false;
605 // Launch the helper threads
606 for(i = 1; i < THREAD_MAX; i++)
608 #if !defined(_MSC_VER)
609 pthread_create(pthread, NULL, init_thread, (void*)(&i));
612 CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
615 // Wait until the thread has finished launching:
616 while (!Threads[i].running);
619 // Init also the empty search stack
620 EmptySearchStack.init(0);
621 EmptySearchStack.initKillers();
625 /// stop_threads() is called when the program exits. It makes all the
626 /// helper threads exit cleanly.
628 void stop_threads() {
630 ActiveThreads = THREAD_MAX; // HACK
631 Idle = false; // HACK
632 wake_sleeping_threads();
633 AllThreadsShouldExit = true;
634 for (int i = 1; i < THREAD_MAX; i++)
636 Threads[i].stop = true;
637 while(Threads[i].running);
639 destroy_split_point_stack();
643 /// nodes_searched() returns the total number of nodes searched so far in
644 /// the current search.
646 int64_t nodes_searched() {
648 int64_t result = 0ULL;
649 for (int i = 0; i < ActiveThreads; i++)
650 result += Threads[i].nodes;
657 // id_loop() is the main iterative deepening loop. It calls root_search
658 // repeatedly with increasing depth until the allocated thinking time has
659 // been consumed, the user stops the search, or the maximum search depth is
662 Value id_loop(const Position &pos, Move searchMoves[]) {
665 SearchStack ss[PLY_MAX_PLUS_2];
667 // searchMoves are verified, copied, scored and sorted
668 RootMoveList rml(p, searchMoves);
673 for (int i = 0; i < 3; i++)
678 IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0));
681 EasyMove = rml.scan_for_easy_move();
683 // Iterative deepening loop
684 while (Iteration < PLY_MAX)
686 // Initialize iteration
689 BestMoveChangesByIteration[Iteration] = 0;
693 std::cout << "info depth " << Iteration << std::endl;
695 // Calculate dynamic search window based on previous iterations
698 if (MultiPV == 1 && Iteration >= 6)
700 int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
701 int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
703 int delta = Max(2 * abs(prevDelta1) + abs(prevDelta2), ProblemMargin);
705 alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE);
706 beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE);
710 alpha = - VALUE_INFINITE;
711 beta = VALUE_INFINITE;
714 // Search to the current depth
715 Value value = root_search(p, ss, rml, alpha, beta);
717 // Write PV to transposition table, in case the relevant entries have
718 // been overwritten during the search.
719 TT.insert_pv(p, ss[0].pv);
722 break; // Value cannot be trusted. Break out immediately!
724 //Save info about search result
725 Value speculatedValue;
728 Value delta = value - IterationInfo[Iteration - 1].value;
735 speculatedValue = value + delta;
736 BestMoveChangesByIteration[Iteration] += 2; // Allocate more time
738 else if (value <= alpha)
740 assert(value == alpha);
744 speculatedValue = value + delta;
745 BestMoveChangesByIteration[Iteration] += 3; // Allocate more time
747 speculatedValue = value;
749 speculatedValue = Min(Max(speculatedValue, -VALUE_INFINITE), VALUE_INFINITE);
750 IterationInfo[Iteration] = IterationInfoType(value, speculatedValue);
752 // Erase the easy move if it differs from the new best move
753 if (ss[0].pv[0] != EasyMove)
754 EasyMove = MOVE_NONE;
761 bool stopSearch = false;
763 // Stop search early if there is only a single legal move:
764 if (Iteration >= 6 && rml.move_count() == 1)
767 // Stop search early when the last two iterations returned a mate score
769 && abs(IterationInfo[Iteration].value) >= abs(VALUE_MATE) - 100
770 && abs(IterationInfo[Iteration-1].value) >= abs(VALUE_MATE) - 100)
773 // Stop search early if one move seems to be much better than the rest
774 int64_t nodes = nodes_searched();
778 && EasyMove == ss[0].pv[0]
779 && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100
780 && current_search_time() > MaxSearchTime / 16)
781 ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100
782 && current_search_time() > MaxSearchTime / 32)))
785 // Add some extra time if the best move has changed during the last two iterations
786 if (Iteration > 5 && Iteration <= 50)
787 ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2)
788 + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
790 // Stop search if most of MaxSearchTime is consumed at the end of the
791 // iteration. We probably don't have enough time to search the first
792 // move at the next iteration anyway.
793 if (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128)
798 //FIXME: Implement fail-low emergency measures
802 StopOnPonderhit = true;
806 if (MaxDepth && Iteration >= MaxDepth)
812 // If we are pondering, we shouldn't print the best move before we
815 wait_for_stop_or_ponderhit();
817 // Print final search statistics
818 std::cout << "info nodes " << nodes_searched()
820 << " time " << current_search_time()
821 << " hashfull " << TT.full() << std::endl;
823 // Print the best move and the ponder move to the standard output
824 if (ss[0].pv[0] == MOVE_NONE)
826 ss[0].pv[0] = rml.get_move(0);
827 ss[0].pv[1] = MOVE_NONE;
829 std::cout << "bestmove " << ss[0].pv[0];
830 if (ss[0].pv[1] != MOVE_NONE)
831 std::cout << " ponder " << ss[0].pv[1];
833 std::cout << std::endl;
838 dbg_print_mean(LogFile);
840 if (dbg_show_hit_rate)
841 dbg_print_hit_rate(LogFile);
844 LogFile << "Nodes: " << nodes_searched() << std::endl
845 << "Nodes/second: " << nps() << std::endl
846 << "Best move: " << move_to_san(p, ss[0].pv[0]) << std::endl;
848 p.do_move(ss[0].pv[0], st);
849 LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1])
850 << std::endl << std::endl;
852 return rml.get_move_score(0);
856 // root_search() is the function which searches the root node. It is
857 // similar to search_pv except that it uses a different move ordering
858 // scheme (perhaps we should try to use this at internal PV nodes, too?)
859 // and prints some information to the standard output.
861 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
863 Value oldAlpha = alpha;
865 Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
867 // Loop through all the moves in the root move list
868 for (int i = 0; i < rml.move_count() && !AbortSearch; i++)
872 // We failed high, invalidate and skip next moves, leave node-counters
873 // and beta-counters as they are and quickly return, we will try to do
874 // a research at the next iteration with a bigger aspiration window.
875 rml.set_move_score(i, -VALUE_INFINITE);
883 RootMoveNumber = i + 1;
886 // Remember the node count before the move is searched. The node counts
887 // are used to sort the root moves at the next iteration.
888 nodes = nodes_searched();
890 // Reset beta cut-off counters
893 // Pick the next root move, and print the move and the move number to
894 // the standard output.
895 move = ss[0].currentMove = rml.get_move(i);
896 if (current_search_time() >= 1000)
897 std::cout << "info currmove " << move
898 << " currmovenumber " << i + 1 << std::endl;
900 // Decide search depth for this move
902 ext = extension(pos, move, true, pos.move_is_capture(move), pos.move_is_check(move), false, false, &dangerous);
903 newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
905 // Make the move, and search it
906 pos.do_move(move, st, dcCandidates);
910 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
911 // If the value has dropped a lot compared to the last iteration,
912 // set the boolean variable Problem to true. This variable is used
913 // for time managment: When Problem is true, we try to complete the
914 // current iteration before playing a move.
915 Problem = (Iteration >= 2 && value <= IterationInfo[Iteration-1].value - ProblemMargin);
917 if (Problem && StopOnPonderhit)
918 StopOnPonderhit = false;
922 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
925 // Fail high! Set the boolean variable FailHigh to true, and
926 // re-search the move with a big window. The variable FailHigh is
927 // used for time managment: We try to avoid aborting the search
928 // prematurely during a fail high research.
930 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
936 // Finished searching the move. If AbortSearch is true, the search
937 // was aborted because the user interrupted the search or because we
938 // ran out of time. In this case, the return value of the search cannot
939 // be trusted, and we break out of the loop without updating the best
944 // Remember the node count for this move. The node counts are used to
945 // sort the root moves at the next iteration.
946 rml.set_move_nodes(i, nodes_searched() - nodes);
948 // Remember the beta-cutoff statistics
950 BetaCounter.read(pos.side_to_move(), our, their);
951 rml.set_beta_counters(i, our, their);
953 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
955 if (value <= alpha && i >= MultiPV)
956 rml.set_move_score(i, -VALUE_INFINITE);
959 // PV move or new best move!
962 rml.set_move_score(i, value);
964 rml.set_move_pv(i, ss[0].pv);
968 // We record how often the best move has been changed in each
969 // iteration. This information is used for time managment: When
970 // the best move changes frequently, we allocate some more time.
972 BestMoveChangesByIteration[Iteration]++;
974 // Print search information to the standard output:
975 std::cout << "info depth " << Iteration
976 << " score " << value_to_string(value)
977 << " time " << current_search_time()
978 << " nodes " << nodes_searched()
982 for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
983 std::cout << ss[0].pv[j] << " ";
985 std::cout << std::endl;
988 LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ss[0].pv)
994 // Reset the global variable Problem to false if the value isn't too
995 // far below the final value from the last iteration.
996 if (value > IterationInfo[Iteration - 1].value - NoProblemMargin)
1001 rml.sort_multipv(i);
1002 for (int j = 0; j < Min(MultiPV, rml.move_count()); j++)
1005 std::cout << "info multipv " << j + 1
1006 << " score " << value_to_string(rml.get_move_score(j))
1007 << " depth " << ((j <= i)? Iteration : Iteration - 1)
1008 << " time " << current_search_time()
1009 << " nodes " << nodes_searched()
1013 for (k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
1014 std::cout << rml.get_move_pv(j, k) << " ";
1016 std::cout << std::endl;
1018 alpha = rml.get_move_score(Min(i, MultiPV-1));
1020 } // New best move case
1022 assert(alpha >= oldAlpha);
1024 FailLow = (alpha == oldAlpha);
1030 // search_pv() is the main search function for PV nodes.
1032 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
1033 Depth depth, int ply, int threadID) {
1035 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1036 assert(beta > alpha && beta <= VALUE_INFINITE);
1037 assert(ply >= 0 && ply < PLY_MAX);
1038 assert(threadID >= 0 && threadID < ActiveThreads);
1041 return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
1043 // Initialize, and make an early exit in case of an aborted search,
1044 // an instant draw, maximum ply reached, etc.
1045 init_node(ss, ply, threadID);
1047 // After init_node() that calls poll()
1048 if (AbortSearch || thread_should_stop(threadID))
1056 if (ply >= PLY_MAX - 1)
1057 return evaluate(pos, ei, threadID);
1059 // Mate distance pruning
1060 Value oldAlpha = alpha;
1061 alpha = Max(value_mated_in(ply), alpha);
1062 beta = Min(value_mate_in(ply+1), beta);
1066 // Transposition table lookup. At PV nodes, we don't use the TT for
1067 // pruning, but only for move ordering.
1068 const TTEntry* tte = TT.retrieve(pos);
1069 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1071 // Go with internal iterative deepening if we don't have a TT move
1072 if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly)
1074 search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
1075 ttMove = ss[ply].pv[ply];
1078 // Initialize a MovePicker object for the current position, and prepare
1079 // to search all moves
1080 MovePicker mp = MovePicker(pos, true, ttMove, ss[ply], depth);
1082 Move move, movesSearched[256];
1084 Value value, bestValue = -VALUE_INFINITE;
1085 Bitboard dcCandidates = mp.discovered_check_candidates();
1086 Color us = pos.side_to_move();
1087 bool isCheck = pos.is_check();
1088 bool mateThreat = pos.has_mate_threat(opposite_color(us));
1090 // Loop through all legal moves until no moves remain or a beta cutoff
1092 while ( alpha < beta
1093 && (move = mp.get_next_move()) != MOVE_NONE
1094 && !thread_should_stop(threadID))
1096 assert(move_is_ok(move));
1098 bool singleReply = (isCheck && mp.number_of_moves() == 1);
1099 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1100 bool moveIsCapture = pos.move_is_capture(move);
1102 movesSearched[moveCount++] = ss[ply].currentMove = move;
1104 // Decide the new search depth
1106 Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous);
1107 Depth newDepth = depth - OnePly + ext;
1109 // Make and search the move
1111 pos.do_move(move, st, dcCandidates);
1113 if (moveCount == 1) // The first move in list is the PV
1114 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1117 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1118 // if the move fails high will be re-searched at full depth.
1119 if ( depth >= 2*OnePly
1120 && moveCount >= LMRPVMoves
1123 && !move_promotion(move)
1124 && !move_is_castle(move)
1125 && !move_is_killer(move, ss[ply]))
1127 ss[ply].reduction = OnePly;
1128 value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true, threadID);
1131 value = alpha + 1; // Just to trigger next condition
1133 if (value > alpha) // Go with full depth non-pv search
1135 ss[ply].reduction = Depth(0);
1136 value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
1137 if (value > alpha && value < beta)
1139 // When the search fails high at ply 1 while searching the first
1140 // move at the root, set the flag failHighPly1. This is used for
1141 // time managment: We don't want to stop the search early in
1142 // such cases, because resolving the fail high at ply 1 could
1143 // result in a big drop in score at the root.
1144 if (ply == 1 && RootMoveNumber == 1)
1145 Threads[threadID].failHighPly1 = true;
1147 // A fail high occurred. Re-search at full window (pv search)
1148 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1149 Threads[threadID].failHighPly1 = false;
1153 pos.undo_move(move);
1155 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1158 if (value > bestValue)
1165 if (value == value_mate_in(ply + 1))
1166 ss[ply].mateKiller = move;
1168 // If we are at ply 1, and we are searching the first root move at
1169 // ply 0, set the 'Problem' variable if the score has dropped a lot
1170 // (from the computer's point of view) since the previous iteration:
1173 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
1178 if ( ActiveThreads > 1
1180 && depth >= MinimumSplitDepth
1182 && idle_thread_exists(threadID)
1184 && !thread_should_stop(threadID)
1185 && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
1186 &moveCount, &mp, dcCandidates, threadID, true))
1190 // All legal moves have been searched. A special case: If there were
1191 // no legal moves, it must be mate or stalemate:
1193 return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
1195 // If the search is not aborted, update the transposition table,
1196 // history counters, and killer moves.
1197 if (AbortSearch || thread_should_stop(threadID))
1200 if (bestValue <= oldAlpha)
1201 TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER);
1203 else if (bestValue >= beta)
1205 BetaCounter.add(pos.side_to_move(), depth, threadID);
1206 Move m = ss[ply].pv[ply];
1207 if (ok_to_history(pos, m)) // Only non capture moves are considered
1209 update_history(pos, m, depth, movesSearched, moveCount);
1210 update_killers(m, ss[ply]);
1212 TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
1215 TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply], VALUE_TYPE_EXACT);
1221 // search() is the search function for zero-width nodes.
1223 Value search(Position &pos, SearchStack ss[], Value beta, Depth depth,
1224 int ply, bool allowNullmove, int threadID) {
1226 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1227 assert(ply >= 0 && ply < PLY_MAX);
1228 assert(threadID >= 0 && threadID < ActiveThreads);
1231 return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1233 // Initialize, and make an early exit in case of an aborted search,
1234 // an instant draw, maximum ply reached, etc.
1235 init_node(ss, ply, threadID);
1237 // After init_node() that calls poll()
1238 if (AbortSearch || thread_should_stop(threadID))
1246 if (ply >= PLY_MAX - 1)
1247 return evaluate(pos, ei, threadID);
1249 // Mate distance pruning
1250 if (value_mated_in(ply) >= beta)
1253 if (value_mate_in(ply + 1) < beta)
1256 // Transposition table lookup
1257 const TTEntry* tte = TT.retrieve(pos);
1258 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1260 if (tte && ok_to_use_TT(tte, depth, beta, ply))
1262 ss[ply].currentMove = ttMove; // can be MOVE_NONE
1263 return value_from_tt(tte->value(), ply);
1266 Value approximateEval = quick_evaluate(pos);
1267 bool mateThreat = false;
1268 bool isCheck = pos.is_check();
1274 && !value_is_mate(beta)
1275 && ok_to_do_nullmove(pos)
1276 && approximateEval >= beta - NullMoveMargin)
1278 ss[ply].currentMove = MOVE_NULL;
1281 pos.do_null_move(st);
1282 int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
1284 Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
1286 pos.undo_null_move();
1288 if (value_is_mate(nullValue))
1290 /* Do not return unproven mates */
1292 else if (nullValue >= beta)
1294 if (depth < 6 * OnePly)
1297 // Do zugzwang verification search
1298 Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
1302 // The null move failed low, which means that we may be faced with
1303 // some kind of threat. If the previous move was reduced, check if
1304 // the move that refuted the null move was somehow connected to the
1305 // move which was reduced. If a connection is found, return a fail
1306 // low score (which will cause the reduced move to fail high in the
1307 // parent node, which will trigger a re-search with full depth).
1308 if (nullValue == value_mated_in(ply + 2))
1311 ss[ply].threatMove = ss[ply + 1].currentMove;
1312 if ( depth < ThreatDepth
1313 && ss[ply - 1].reduction
1314 && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
1318 // Null move search not allowed, try razoring
1319 else if ( !value_is_mate(beta)
1320 && depth < RazorDepth
1321 && approximateEval < beta - RazorApprMargins[int(depth) - 2]
1322 && ttMove == MOVE_NONE
1323 && !pos.has_pawn_on_7th(pos.side_to_move()))
1325 Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1326 if (v < beta - RazorMargins[int(depth) - 2])
1330 // Go with internal iterative deepening if we don't have a TT move
1331 if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
1332 evaluate(pos, ei, threadID) >= beta - IIDMargin)
1334 search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
1335 ttMove = ss[ply].pv[ply];
1338 // Initialize a MovePicker object for the current position, and prepare
1339 // to search all moves:
1340 MovePicker mp = MovePicker(pos, false, ttMove, ss[ply], depth);
1342 Move move, movesSearched[256];
1344 Value value, bestValue = -VALUE_INFINITE;
1345 Bitboard dcCandidates = mp.discovered_check_candidates();
1346 Value futilityValue = VALUE_NONE;
1347 bool useFutilityPruning = UseFutilityPruning
1348 && depth < SelectiveDepth
1351 // Loop through all legal moves until no moves remain or a beta cutoff
1353 while ( bestValue < beta
1354 && (move = mp.get_next_move()) != MOVE_NONE
1355 && !thread_should_stop(threadID))
1357 assert(move_is_ok(move));
1359 bool singleReply = (isCheck && mp.number_of_moves() == 1);
1360 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1361 bool moveIsCapture = pos.move_is_capture(move);
1363 movesSearched[moveCount++] = ss[ply].currentMove = move;
1365 // Decide the new search depth
1367 Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous);
1368 Depth newDepth = depth - OnePly + ext;
1371 if ( useFutilityPruning
1374 && !move_promotion(move))
1376 // History pruning. See ok_to_prune() definition
1377 if ( moveCount >= 2 + int(depth)
1378 && ok_to_prune(pos, move, ss[ply].threatMove, depth))
1381 // Value based pruning
1382 if (depth < 7 * OnePly && approximateEval < beta)
1384 if (futilityValue == VALUE_NONE)
1385 futilityValue = evaluate(pos, ei, threadID)
1386 + FutilityMargins[int(depth) - 2];
1388 if (futilityValue < beta)
1390 if (futilityValue > bestValue)
1391 bestValue = futilityValue;
1397 // Make and search the move
1399 pos.do_move(move, st, dcCandidates);
1401 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1402 // if the move fails high will be re-searched at full depth.
1403 if ( depth >= 2*OnePly
1404 && moveCount >= LMRNonPVMoves
1407 && !move_promotion(move)
1408 && !move_is_castle(move)
1409 && !move_is_killer(move, ss[ply]))
1411 ss[ply].reduction = OnePly;
1412 value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true, threadID);
1415 value = beta; // Just to trigger next condition
1417 if (value >= beta) // Go with full depth non-pv search
1419 ss[ply].reduction = Depth(0);
1420 value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
1422 pos.undo_move(move);
1424 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1427 if (value > bestValue)
1433 if (value == value_mate_in(ply + 1))
1434 ss[ply].mateKiller = move;
1438 if ( ActiveThreads > 1
1440 && depth >= MinimumSplitDepth
1442 && idle_thread_exists(threadID)
1444 && !thread_should_stop(threadID)
1445 && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
1446 &mp, dcCandidates, threadID, false))
1450 // All legal moves have been searched. A special case: If there were
1451 // no legal moves, it must be mate or stalemate.
1453 return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW);
1455 // If the search is not aborted, update the transposition table,
1456 // history counters, and killer moves.
1457 if (AbortSearch || thread_should_stop(threadID))
1460 if (bestValue < beta)
1461 TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE, VALUE_TYPE_UPPER);
1464 BetaCounter.add(pos.side_to_move(), depth, threadID);
1465 Move m = ss[ply].pv[ply];
1466 if (ok_to_history(pos, m)) // Only non capture moves are considered
1468 update_history(pos, m, depth, movesSearched, moveCount);
1469 update_killers(m, ss[ply]);
1471 TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
1474 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1480 // qsearch() is the quiescence search function, which is called by the main
1481 // search function when the remaining depth is zero (or, to be more precise,
1482 // less than OnePly).
1484 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
1485 Depth depth, int ply, int threadID) {
1487 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1488 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1490 assert(ply >= 0 && ply < PLY_MAX);
1491 assert(threadID >= 0 && threadID < ActiveThreads);
1493 // Initialize, and make an early exit in case of an aborted search,
1494 // an instant draw, maximum ply reached, etc.
1495 init_node(ss, ply, threadID);
1497 // After init_node() that calls poll()
1498 if (AbortSearch || thread_should_stop(threadID))
1504 // Transposition table lookup, only when not in PV
1505 TTEntry* tte = NULL;
1506 bool pvNode = (beta - alpha != 1);
1509 tte = TT.retrieve(pos);
1510 if (tte && ok_to_use_TT(tte, depth, beta, ply))
1512 assert(tte->type() != VALUE_TYPE_EVAL);
1514 return value_from_tt(tte->value(), ply);
1517 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1519 // Evaluate the position statically
1522 bool isCheck = pos.is_check();
1523 ei.futilityMargin = Value(0); // Manually initialize futilityMargin
1526 staticValue = -VALUE_INFINITE;
1528 else if (tte && tte->type() == VALUE_TYPE_EVAL)
1530 // Use the cached evaluation score if possible
1531 assert(tte->value() == evaluate(pos, ei, threadID));
1532 assert(ei.futilityMargin == Value(0));
1534 staticValue = tte->value();
1537 staticValue = evaluate(pos, ei, threadID);
1539 if (ply == PLY_MAX - 1)
1540 return evaluate(pos, ei, threadID);
1542 // Initialize "stand pat score", and return it immediately if it is
1544 Value bestValue = staticValue;
1546 if (bestValue >= beta)
1548 // Store the score to avoid a future costly evaluation() call
1549 if (!isCheck && !tte && ei.futilityMargin == 0)
1550 TT.store(pos, value_to_tt(bestValue, ply), Depth(-127*OnePly), MOVE_NONE, VALUE_TYPE_EVAL);
1555 if (bestValue > alpha)
1558 // Initialize a MovePicker object for the current position, and prepare
1559 // to search the moves. Because the depth is <= 0 here, only captures,
1560 // queen promotions and checks (only if depth == 0) will be generated.
1561 MovePicker mp = MovePicker(pos, pvNode, ttMove, EmptySearchStack, depth);
1564 Bitboard dcCandidates = mp.discovered_check_candidates();
1565 Color us = pos.side_to_move();
1566 bool enoughMaterial = pos.non_pawn_material(us) > RookValueMidgame;
1568 // Loop through the moves until no moves remain or a beta cutoff
1570 while ( alpha < beta
1571 && (move = mp.get_next_move()) != MOVE_NONE)
1573 assert(move_is_ok(move));
1576 ss[ply].currentMove = move;
1579 if ( UseQSearchFutilityPruning
1583 && !move_promotion(move)
1584 && !pos.move_is_check(move, dcCandidates)
1585 && !pos.move_is_passed_pawn_push(move))
1587 Value futilityValue = staticValue
1588 + Max(pos.midgame_value_of_piece_on(move_to(move)),
1589 pos.endgame_value_of_piece_on(move_to(move)))
1590 + (move_is_ep(move) ? PawnValueEndgame : Value(0))
1592 + ei.futilityMargin;
1594 if (futilityValue < alpha)
1596 if (futilityValue > bestValue)
1597 bestValue = futilityValue;
1602 // Don't search captures and checks with negative SEE values
1604 && !move_promotion(move)
1605 && (pos.midgame_value_of_piece_on(move_from(move)) >
1606 pos.midgame_value_of_piece_on(move_to(move)))
1607 && pos.see(move) < 0)
1610 // Make and search the move.
1612 pos.do_move(move, st, dcCandidates);
1613 Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
1614 pos.undo_move(move);
1616 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1619 if (value > bestValue)
1630 // All legal moves have been searched. A special case: If we're in check
1631 // and no legal moves were found, it is checkmate:
1632 if (pos.is_check() && moveCount == 0) // Mate!
1633 return value_mated_in(ply);
1635 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1637 // Update transposition table
1638 Move m = ss[ply].pv[ply];
1641 Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
1642 if (bestValue < beta)
1643 TT.store(pos, value_to_tt(bestValue, ply), d, MOVE_NONE, VALUE_TYPE_UPPER);
1645 TT.store(pos, value_to_tt(bestValue, ply), d, m, VALUE_TYPE_LOWER);
1648 // Update killers only for good check moves
1649 if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
1650 update_killers(m, ss[ply]);
1656 // sp_search() is used to search from a split point. This function is called
1657 // by each thread working at the split point. It is similar to the normal
1658 // search() function, but simpler. Because we have already probed the hash
1659 // table, done a null move search, and searched the first move before
1660 // splitting, we don't have to repeat all this work in sp_search(). We
1661 // also don't need to store anything to the hash table here: This is taken
1662 // care of after we return from the split point.
1664 void sp_search(SplitPoint *sp, int threadID) {
1666 assert(threadID >= 0 && threadID < ActiveThreads);
1667 assert(ActiveThreads > 1);
1669 Position pos = Position(sp->pos);
1670 SearchStack *ss = sp->sstack[threadID];
1673 bool isCheck = pos.is_check();
1674 bool useFutilityPruning = UseFutilityPruning
1675 && sp->depth < SelectiveDepth
1678 while ( sp->bestValue < sp->beta
1679 && !thread_should_stop(threadID)
1680 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
1682 assert(move_is_ok(move));
1684 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1685 bool moveIsCapture = pos.move_is_capture(move);
1687 lock_grab(&(sp->lock));
1688 int moveCount = ++sp->moves;
1689 lock_release(&(sp->lock));
1691 ss[sp->ply].currentMove = move;
1693 // Decide the new search depth.
1695 Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, false, false, &dangerous);
1696 Depth newDepth = sp->depth - OnePly + ext;
1699 if ( useFutilityPruning
1702 && !move_promotion(move)
1703 && moveCount >= 2 + int(sp->depth)
1704 && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
1707 // Make and search the move.
1709 pos.do_move(move, st, sp->dcCandidates);
1711 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1712 // if the move fails high will be re-searched at full depth.
1714 && moveCount >= LMRNonPVMoves
1716 && !move_promotion(move)
1717 && !move_is_castle(move)
1718 && !move_is_killer(move, ss[sp->ply]))
1720 ss[sp->ply].reduction = OnePly;
1721 value = -search(pos, ss, -(sp->beta-1), newDepth - OnePly, sp->ply+1, true, threadID);
1724 value = sp->beta; // Just to trigger next condition
1726 if (value >= sp->beta) // Go with full depth non-pv search
1728 ss[sp->ply].reduction = Depth(0);
1729 value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
1731 pos.undo_move(move);
1733 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1735 if (thread_should_stop(threadID))
1739 lock_grab(&(sp->lock));
1740 if (value > sp->bestValue && !thread_should_stop(threadID))
1742 sp->bestValue = value;
1743 if (sp->bestValue >= sp->beta)
1745 sp_update_pv(sp->parentSstack, ss, sp->ply);
1746 for (int i = 0; i < ActiveThreads; i++)
1747 if (i != threadID && (i == sp->master || sp->slaves[i]))
1748 Threads[i].stop = true;
1750 sp->finished = true;
1753 lock_release(&(sp->lock));
1756 lock_grab(&(sp->lock));
1758 // If this is the master thread and we have been asked to stop because of
1759 // a beta cutoff higher up in the tree, stop all slave threads:
1760 if (sp->master == threadID && thread_should_stop(threadID))
1761 for (int i = 0; i < ActiveThreads; i++)
1763 Threads[i].stop = true;
1766 sp->slaves[threadID] = 0;
1768 lock_release(&(sp->lock));
1772 // sp_search_pv() is used to search from a PV split point. This function
1773 // is called by each thread working at the split point. It is similar to
1774 // the normal search_pv() function, but simpler. Because we have already
1775 // probed the hash table and searched the first move before splitting, we
1776 // don't have to repeat all this work in sp_search_pv(). We also don't
1777 // need to store anything to the hash table here: This is taken care of
1778 // after we return from the split point.
1780 void sp_search_pv(SplitPoint *sp, int threadID) {
1782 assert(threadID >= 0 && threadID < ActiveThreads);
1783 assert(ActiveThreads > 1);
1785 Position pos = Position(sp->pos);
1786 SearchStack *ss = sp->sstack[threadID];
1790 while ( sp->alpha < sp->beta
1791 && !thread_should_stop(threadID)
1792 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
1794 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1795 bool moveIsCapture = pos.move_is_capture(move);
1797 assert(move_is_ok(move));
1799 lock_grab(&(sp->lock));
1800 int moveCount = ++sp->moves;
1801 lock_release(&(sp->lock));
1803 ss[sp->ply].currentMove = move;
1805 // Decide the new search depth.
1807 Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, false, false, &dangerous);
1808 Depth newDepth = sp->depth - OnePly + ext;
1810 // Make and search the move.
1812 pos.do_move(move, st, sp->dcCandidates);
1814 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1815 // if the move fails high will be re-searched at full depth.
1817 && moveCount >= LMRPVMoves
1819 && !move_promotion(move)
1820 && !move_is_castle(move)
1821 && !move_is_killer(move, ss[sp->ply]))
1823 ss[sp->ply].reduction = OnePly;
1824 value = -search(pos, ss, -sp->alpha, newDepth - OnePly, sp->ply+1, true, threadID);
1827 value = sp->alpha + 1; // Just to trigger next condition
1829 if (value > sp->alpha) // Go with full depth non-pv search
1831 ss[sp->ply].reduction = Depth(0);
1832 value = -search(pos, ss, -sp->alpha, newDepth, sp->ply+1, true, threadID);
1834 if (value > sp->alpha && value < sp->beta)
1836 // When the search fails high at ply 1 while searching the first
1837 // move at the root, set the flag failHighPly1. This is used for
1838 // time managment: We don't want to stop the search early in
1839 // such cases, because resolving the fail high at ply 1 could
1840 // result in a big drop in score at the root.
1841 if (sp->ply == 1 && RootMoveNumber == 1)
1842 Threads[threadID].failHighPly1 = true;
1844 value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, threadID);
1845 Threads[threadID].failHighPly1 = false;
1848 pos.undo_move(move);
1850 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1852 if (thread_should_stop(threadID))
1856 lock_grab(&(sp->lock));
1857 if (value > sp->bestValue && !thread_should_stop(threadID))
1859 sp->bestValue = value;
1860 if (value > sp->alpha)
1863 sp_update_pv(sp->parentSstack, ss, sp->ply);
1864 if (value == value_mate_in(sp->ply + 1))
1865 ss[sp->ply].mateKiller = move;
1867 if(value >= sp->beta)
1869 for(int i = 0; i < ActiveThreads; i++)
1870 if(i != threadID && (i == sp->master || sp->slaves[i]))
1871 Threads[i].stop = true;
1873 sp->finished = true;
1876 // If we are at ply 1, and we are searching the first root move at
1877 // ply 0, set the 'Problem' variable if the score has dropped a lot
1878 // (from the computer's point of view) since the previous iteration.
1881 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
1884 lock_release(&(sp->lock));
1887 lock_grab(&(sp->lock));
1889 // If this is the master thread and we have been asked to stop because of
1890 // a beta cutoff higher up in the tree, stop all slave threads.
1891 if (sp->master == threadID && thread_should_stop(threadID))
1892 for (int i = 0; i < ActiveThreads; i++)
1894 Threads[i].stop = true;
1897 sp->slaves[threadID] = 0;
1899 lock_release(&(sp->lock));
1902 /// The BetaCounterType class
1904 BetaCounterType::BetaCounterType() { clear(); }
1906 void BetaCounterType::clear() {
1908 for (int i = 0; i < THREAD_MAX; i++)
1909 hits[i][WHITE] = hits[i][BLACK] = 0ULL;
1912 void BetaCounterType::add(Color us, Depth d, int threadID) {
1914 // Weighted count based on depth
1915 hits[threadID][us] += int(d);
1918 void BetaCounterType::read(Color us, int64_t& our, int64_t& their) {
1921 for (int i = 0; i < THREAD_MAX; i++)
1924 their += hits[i][opposite_color(us)];
1929 /// The RootMove class
1933 RootMove::RootMove() {
1934 nodes = cumulativeNodes = 0ULL;
1937 // RootMove::operator<() is the comparison function used when
1938 // sorting the moves. A move m1 is considered to be better
1939 // than a move m2 if it has a higher score, or if the moves
1940 // have equal score but m1 has the higher node count.
1942 bool RootMove::operator<(const RootMove& m) {
1944 if (score != m.score)
1945 return (score < m.score);
1947 return theirBeta <= m.theirBeta;
1950 /// The RootMoveList class
1954 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
1956 MoveStack mlist[MaxRootMoves];
1957 bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
1959 // Generate all legal moves
1960 int lm_count = generate_legal_moves(pos, mlist);
1962 // Add each move to the moves[] array
1963 for (int i = 0; i < lm_count; i++)
1965 bool includeMove = includeAllMoves;
1967 for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
1968 includeMove = (searchMoves[k] == mlist[i].move);
1972 // Find a quick score for the move
1974 SearchStack ss[PLY_MAX_PLUS_2];
1976 moves[count].move = mlist[i].move;
1977 moves[count].nodes = 0ULL;
1978 pos.do_move(moves[count].move, st);
1979 moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE,
1981 pos.undo_move(moves[count].move);
1982 moves[count].pv[0] = moves[i].move;
1983 moves[count].pv[1] = MOVE_NONE; // FIXME
1991 // Simple accessor methods for the RootMoveList class
1993 inline Move RootMoveList::get_move(int moveNum) const {
1994 return moves[moveNum].move;
1997 inline Value RootMoveList::get_move_score(int moveNum) const {
1998 return moves[moveNum].score;
2001 inline void RootMoveList::set_move_score(int moveNum, Value score) {
2002 moves[moveNum].score = score;
2005 inline void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
2006 moves[moveNum].nodes = nodes;
2007 moves[moveNum].cumulativeNodes += nodes;
2010 inline void RootMoveList::set_beta_counters(int moveNum, int64_t our, int64_t their) {
2011 moves[moveNum].ourBeta = our;
2012 moves[moveNum].theirBeta = their;
2015 void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
2017 for(j = 0; pv[j] != MOVE_NONE; j++)
2018 moves[moveNum].pv[j] = pv[j];
2019 moves[moveNum].pv[j] = MOVE_NONE;
2022 inline Move RootMoveList::get_move_pv(int moveNum, int i) const {
2023 return moves[moveNum].pv[i];
2026 inline int64_t RootMoveList::get_move_cumulative_nodes(int moveNum) const {
2027 return moves[moveNum].cumulativeNodes;
2030 inline int RootMoveList::move_count() const {
2035 // RootMoveList::scan_for_easy_move() is called at the end of the first
2036 // iteration, and is used to detect an "easy move", i.e. a move which appears
2037 // to be much bester than all the rest. If an easy move is found, the move
2038 // is returned, otherwise the function returns MOVE_NONE. It is very
2039 // important that this function is called at the right moment: The code
2040 // assumes that the first iteration has been completed and the moves have
2041 // been sorted. This is done in RootMoveList c'tor.
2043 Move RootMoveList::scan_for_easy_move() const {
2050 // moves are sorted so just consider the best and the second one
2051 if (get_move_score(0) > get_move_score(1) + EasyMoveMargin)
2057 // RootMoveList::sort() sorts the root move list at the beginning of a new
2060 inline void RootMoveList::sort() {
2062 sort_multipv(count - 1); // all items
2066 // RootMoveList::sort_multipv() sorts the first few moves in the root move
2067 // list by their scores and depths. It is used to order the different PVs
2068 // correctly in MultiPV mode.
2070 void RootMoveList::sort_multipv(int n) {
2072 for (int i = 1; i <= n; i++)
2074 RootMove rm = moves[i];
2076 for (j = i; j > 0 && moves[j-1] < rm; j--)
2077 moves[j] = moves[j-1];
2083 // init_node() is called at the beginning of all the search functions
2084 // (search(), search_pv(), qsearch(), and so on) and initializes the search
2085 // stack object corresponding to the current node. Once every
2086 // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
2087 // for user input and checks whether it is time to stop the search.
2089 void init_node(SearchStack ss[], int ply, int threadID) {
2090 assert(ply >= 0 && ply < PLY_MAX);
2091 assert(threadID >= 0 && threadID < ActiveThreads);
2093 Threads[threadID].nodes++;
2097 if(NodesSincePoll >= NodesBetweenPolls) {
2104 ss[ply+2].initKillers();
2106 if(Threads[threadID].printCurrentLine)
2107 print_current_line(ss, ply, threadID);
2111 // update_pv() is called whenever a search returns a value > alpha. It
2112 // updates the PV in the SearchStack object corresponding to the current
2115 void update_pv(SearchStack ss[], int ply) {
2116 assert(ply >= 0 && ply < PLY_MAX);
2118 ss[ply].pv[ply] = ss[ply].currentMove;
2120 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
2121 ss[ply].pv[p] = ss[ply+1].pv[p];
2122 ss[ply].pv[p] = MOVE_NONE;
2126 // sp_update_pv() is a variant of update_pv for use at split points. The
2127 // difference between the two functions is that sp_update_pv also updates
2128 // the PV at the parent node.
2130 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply) {
2131 assert(ply >= 0 && ply < PLY_MAX);
2133 ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
2135 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
2136 ss[ply].pv[p] = pss[ply].pv[p] = ss[ply+1].pv[p];
2137 ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE;
2141 // connected_moves() tests whether two moves are 'connected' in the sense
2142 // that the first move somehow made the second move possible (for instance
2143 // if the moving piece is the same in both moves). The first move is
2144 // assumed to be the move that was made to reach the current position, while
2145 // the second move is assumed to be a move from the current position.
2147 bool connected_moves(const Position &pos, Move m1, Move m2) {
2148 Square f1, t1, f2, t2;
2150 assert(move_is_ok(m1));
2151 assert(move_is_ok(m2));
2156 // Case 1: The moving piece is the same in both moves.
2162 // Case 2: The destination square for m2 was vacated by m1.
2168 // Case 3: Moving through the vacated square:
2169 if(piece_is_slider(pos.piece_on(f2)) &&
2170 bit_is_set(squares_between(f2, t2), f1))
2173 // Case 4: The destination square for m2 is attacked by the moving piece
2175 if(pos.piece_attacks_square(pos.piece_on(t1), t1, t2))
2178 // Case 5: Discovered check, checking piece is the piece moved in m1:
2179 if(piece_is_slider(pos.piece_on(t1)) &&
2180 bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())),
2182 !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())),
2184 Bitboard occ = pos.occupied_squares();
2185 Color us = pos.side_to_move();
2186 Square ksq = pos.king_square(us);
2187 clear_bit(&occ, f2);
2188 if(pos.type_of_piece_on(t1) == BISHOP) {
2189 if(bit_is_set(bishop_attacks_bb(ksq, occ), t1))
2192 else if(pos.type_of_piece_on(t1) == ROOK) {
2193 if(bit_is_set(rook_attacks_bb(ksq, occ), t1))
2197 assert(pos.type_of_piece_on(t1) == QUEEN);
2198 if(bit_is_set(queen_attacks_bb(ksq, occ), t1))
2207 // value_is_mate() checks if the given value is a mate one
2208 // eventually compensated for the ply.
2210 bool value_is_mate(Value value) {
2212 assert(abs(value) <= VALUE_INFINITE);
2214 return value <= value_mated_in(PLY_MAX)
2215 || value >= value_mate_in(PLY_MAX);
2219 // move_is_killer() checks if the given move is among the
2220 // killer moves of that ply.
2222 bool move_is_killer(Move m, const SearchStack& ss) {
2224 const Move* k = ss.killers;
2225 for (int i = 0; i < KILLER_MAX; i++, k++)
2233 // extension() decides whether a move should be searched with normal depth,
2234 // or with extended depth. Certain classes of moves (checking moves, in
2235 // particular) are searched with bigger depth than ordinary moves and in
2236 // any case are marked as 'dangerous'. Note that also if a move is not
2237 // extended, as example because the corresponding UCI option is set to zero,
2238 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
2240 Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check,
2241 bool singleReply, bool mateThreat, bool* dangerous) {
2243 assert(m != MOVE_NONE);
2245 Depth result = Depth(0);
2246 *dangerous = check || singleReply || mateThreat;
2249 result += CheckExtension[pvNode];
2252 result += SingleReplyExtension[pvNode];
2255 result += MateThreatExtension[pvNode];
2257 if (pos.type_of_piece_on(move_from(m)) == PAWN)
2259 if (pos.move_is_pawn_push_to_7th(m))
2261 result += PawnPushTo7thExtension[pvNode];
2264 if (pos.move_is_passed_pawn_push(m))
2266 result += PassedPawnExtension[pvNode];
2272 && pos.type_of_piece_on(move_to(m)) != PAWN
2273 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
2274 - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
2275 && !move_promotion(m)
2278 result += PawnEndgameExtension[pvNode];
2284 && pos.type_of_piece_on(move_to(m)) != PAWN
2291 return Min(result, OnePly);
2295 // ok_to_do_nullmove() looks at the current position and decides whether
2296 // doing a 'null move' should be allowed. In order to avoid zugzwang
2297 // problems, null moves are not allowed when the side to move has very
2298 // little material left. Currently, the test is a bit too simple: Null
2299 // moves are avoided only when the side to move has only pawns left. It's
2300 // probably a good idea to avoid null moves in at least some more
2301 // complicated endgames, e.g. KQ vs KR. FIXME
2303 bool ok_to_do_nullmove(const Position &pos) {
2304 if(pos.non_pawn_material(pos.side_to_move()) == Value(0))
2310 // ok_to_prune() tests whether it is safe to forward prune a move. Only
2311 // non-tactical moves late in the move list close to the leaves are
2312 // candidates for pruning.
2314 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d) {
2315 Square mfrom, mto, tfrom, tto;
2317 assert(move_is_ok(m));
2318 assert(threat == MOVE_NONE || move_is_ok(threat));
2319 assert(!move_promotion(m));
2320 assert(!pos.move_is_check(m));
2321 assert(!pos.move_is_capture(m));
2322 assert(!pos.move_is_passed_pawn_push(m));
2323 assert(d >= OnePly);
2325 mfrom = move_from(m);
2327 tfrom = move_from(threat);
2328 tto = move_to(threat);
2330 // Case 1: Castling moves are never pruned.
2331 if (move_is_castle(m))
2334 // Case 2: Don't prune moves which move the threatened piece
2335 if (!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto)
2338 // Case 3: If the threatened piece has value less than or equal to the
2339 // value of the threatening piece, don't prune move which defend it.
2340 if ( !PruneDefendingMoves
2341 && threat != MOVE_NONE
2342 && pos.move_is_capture(threat)
2343 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
2344 || pos.type_of_piece_on(tfrom) == KING)
2345 && pos.move_attacks_square(m, tto))
2348 // Case 4: Don't prune moves with good history.
2349 if (!H.ok_to_prune(pos.piece_on(move_from(m)), m, d))
2352 // Case 5: If the moving piece in the threatened move is a slider, don't
2353 // prune safe moves which block its ray.
2354 if ( !PruneBlockingMoves
2355 && threat != MOVE_NONE
2356 && piece_is_slider(pos.piece_on(tfrom))
2357 && bit_is_set(squares_between(tfrom, tto), mto)
2365 // ok_to_use_TT() returns true if a transposition table score
2366 // can be used at a given point in search.
2368 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
2370 Value v = value_from_tt(tte->value(), ply);
2372 return ( tte->depth() >= depth
2373 || v >= Max(value_mate_in(100), beta)
2374 || v < Min(value_mated_in(100), beta))
2376 && ( (is_lower_bound(tte->type()) && v >= beta)
2377 || (is_upper_bound(tte->type()) && v < beta));
2381 // ok_to_history() returns true if a move m can be stored
2382 // in history. Should be a non capturing move nor a promotion.
2384 bool ok_to_history(const Position& pos, Move m) {
2386 return !pos.move_is_capture(m) && !move_promotion(m);
2390 // update_history() registers a good move that produced a beta-cutoff
2391 // in history and marks as failures all the other moves of that ply.
2393 void update_history(const Position& pos, Move m, Depth depth,
2394 Move movesSearched[], int moveCount) {
2396 H.success(pos.piece_on(move_from(m)), m, depth);
2398 for (int i = 0; i < moveCount - 1; i++)
2400 assert(m != movesSearched[i]);
2401 if (ok_to_history(pos, movesSearched[i]))
2402 H.failure(pos.piece_on(move_from(movesSearched[i])), movesSearched[i]);
2407 // update_killers() add a good move that produced a beta-cutoff
2408 // among the killer moves of that ply.
2410 void update_killers(Move m, SearchStack& ss) {
2412 if (m == ss.killers[0])
2415 for (int i = KILLER_MAX - 1; i > 0; i--)
2416 ss.killers[i] = ss.killers[i - 1];
2421 // fail_high_ply_1() checks if some thread is currently resolving a fail
2422 // high at ply 1 at the node below the first root node. This information
2423 // is used for time managment.
2425 bool fail_high_ply_1() {
2426 for(int i = 0; i < ActiveThreads; i++)
2427 if(Threads[i].failHighPly1)
2433 // current_search_time() returns the number of milliseconds which have passed
2434 // since the beginning of the current search.
2436 int current_search_time() {
2437 return get_system_time() - SearchStartTime;
2441 // nps() computes the current nodes/second count.
2444 int t = current_search_time();
2445 return (t > 0)? int((nodes_searched() * 1000) / t) : 0;
2449 // poll() performs two different functions: It polls for user input, and it
2450 // looks at the time consumed so far and decides if it's time to abort the
2455 static int lastInfoTime;
2456 int t = current_search_time();
2461 // We are line oriented, don't read single chars
2462 std::string command;
2463 if (!std::getline(std::cin, command))
2466 if (command == "quit")
2469 PonderSearch = false;
2472 else if(command == "stop")
2475 PonderSearch = false;
2477 else if(command == "ponderhit")
2480 // Print search information
2484 else if (lastInfoTime > t)
2485 // HACK: Must be a new search where we searched less than
2486 // NodesBetweenPolls nodes during the first second of search.
2489 else if (t - lastInfoTime >= 1000)
2496 if (dbg_show_hit_rate)
2497 dbg_print_hit_rate();
2499 std::cout << "info nodes " << nodes_searched() << " nps " << nps()
2500 << " time " << t << " hashfull " << TT.full() << std::endl;
2501 lock_release(&IOLock);
2502 if (ShowCurrentLine)
2503 Threads[0].printCurrentLine = true;
2505 // Should we stop the search?
2509 bool overTime = t > AbsoluteMaxSearchTime
2510 || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow) //FIXME: We are not checking any problem flags, BUG?
2511 || ( !FailHigh && !FailLow && !fail_high_ply_1() && !Problem
2512 && t > 6*(MaxSearchTime + ExtraSearchTime));
2514 if ( (Iteration >= 3 && (!InfiniteSearch && overTime))
2515 || (ExactMaxTime && t >= ExactMaxTime)
2516 || (Iteration >= 3 && MaxNodes && nodes_searched() >= MaxNodes))
2521 // ponderhit() is called when the program is pondering (i.e. thinking while
2522 // it's the opponent's turn to move) in order to let the engine know that
2523 // it correctly predicted the opponent's move.
2526 int t = current_search_time();
2527 PonderSearch = false;
2528 if(Iteration >= 3 &&
2529 (!InfiniteSearch && (StopOnPonderhit ||
2530 t > AbsoluteMaxSearchTime ||
2531 (RootMoveNumber == 1 &&
2532 t > MaxSearchTime + ExtraSearchTime && !FailLow) ||
2533 (!FailHigh && !FailLow && !fail_high_ply_1() && !Problem &&
2534 t > 6*(MaxSearchTime + ExtraSearchTime)))))
2539 // print_current_line() prints the current line of search for a given
2540 // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
2542 void print_current_line(SearchStack ss[], int ply, int threadID) {
2543 assert(ply >= 0 && ply < PLY_MAX);
2544 assert(threadID >= 0 && threadID < ActiveThreads);
2546 if(!Threads[threadID].idle) {
2548 std::cout << "info currline " << (threadID + 1);
2549 for(int p = 0; p < ply; p++)
2550 std::cout << " " << ss[p].currentMove;
2551 std::cout << std::endl;
2552 lock_release(&IOLock);
2554 Threads[threadID].printCurrentLine = false;
2555 if(threadID + 1 < ActiveThreads)
2556 Threads[threadID + 1].printCurrentLine = true;
2560 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2561 // while the program is pondering. The point is to work around a wrinkle in
2562 // the UCI protocol: When pondering, the engine is not allowed to give a
2563 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2564 // We simply wait here until one of these commands is sent, and return,
2565 // after which the bestmove and pondermove will be printed (in id_loop()).
2567 void wait_for_stop_or_ponderhit() {
2568 std::string command;
2571 if(!std::getline(std::cin, command))
2574 if(command == "quit") {
2575 OpeningBook.close();
2580 else if(command == "ponderhit" || command == "stop")
2586 // idle_loop() is where the threads are parked when they have no work to do.
2587 // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
2588 // object for which the current thread is the master.
2590 void idle_loop(int threadID, SplitPoint *waitSp) {
2591 assert(threadID >= 0 && threadID < THREAD_MAX);
2593 Threads[threadID].running = true;
2596 if(AllThreadsShouldExit && threadID != 0)
2599 // If we are not thinking, wait for a condition to be signaled instead
2600 // of wasting CPU time polling for work:
2601 while(threadID != 0 && (Idle || threadID >= ActiveThreads)) {
2602 #if !defined(_MSC_VER)
2603 pthread_mutex_lock(&WaitLock);
2604 if(Idle || threadID >= ActiveThreads)
2605 pthread_cond_wait(&WaitCond, &WaitLock);
2606 pthread_mutex_unlock(&WaitLock);
2608 WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
2612 // If this thread has been assigned work, launch a search:
2613 if(Threads[threadID].workIsWaiting) {
2614 Threads[threadID].workIsWaiting = false;
2615 if(Threads[threadID].splitPoint->pvNode)
2616 sp_search_pv(Threads[threadID].splitPoint, threadID);
2618 sp_search(Threads[threadID].splitPoint, threadID);
2619 Threads[threadID].idle = true;
2622 // If this thread is the master of a split point and all threads have
2623 // finished their work at this split point, return from the idle loop:
2624 if(waitSp != NULL && waitSp->cpus == 0)
2628 Threads[threadID].running = false;
2632 // init_split_point_stack() is called during program initialization, and
2633 // initializes all split point objects.
2635 void init_split_point_stack() {
2636 for(int i = 0; i < THREAD_MAX; i++)
2637 for(int j = 0; j < MaxActiveSplitPoints; j++) {
2638 SplitPointStack[i][j].parent = NULL;
2639 lock_init(&(SplitPointStack[i][j].lock), NULL);
2644 // destroy_split_point_stack() is called when the program exits, and
2645 // destroys all locks in the precomputed split point objects.
2647 void destroy_split_point_stack() {
2648 for(int i = 0; i < THREAD_MAX; i++)
2649 for(int j = 0; j < MaxActiveSplitPoints; j++)
2650 lock_destroy(&(SplitPointStack[i][j].lock));
2654 // thread_should_stop() checks whether the thread with a given threadID has
2655 // been asked to stop, directly or indirectly. This can happen if a beta
2656 // cutoff has occured in thre thread's currently active split point, or in
2657 // some ancestor of the current split point.
2659 bool thread_should_stop(int threadID) {
2660 assert(threadID >= 0 && threadID < ActiveThreads);
2664 if(Threads[threadID].stop)
2666 if(ActiveThreads <= 2)
2668 for(sp = Threads[threadID].splitPoint; sp != NULL; sp = sp->parent)
2670 Threads[threadID].stop = true;
2677 // thread_is_available() checks whether the thread with threadID "slave" is
2678 // available to help the thread with threadID "master" at a split point. An
2679 // obvious requirement is that "slave" must be idle. With more than two
2680 // threads, this is not by itself sufficient: If "slave" is the master of
2681 // some active split point, it is only available as a slave to the other
2682 // threads which are busy searching the split point at the top of "slave"'s
2683 // split point stack (the "helpful master concept" in YBWC terminology).
2685 bool thread_is_available(int slave, int master) {
2686 assert(slave >= 0 && slave < ActiveThreads);
2687 assert(master >= 0 && master < ActiveThreads);
2688 assert(ActiveThreads > 1);
2690 if(!Threads[slave].idle || slave == master)
2693 if(Threads[slave].activeSplitPoints == 0)
2694 // No active split points means that the thread is available as a slave
2695 // for any other thread.
2698 if(ActiveThreads == 2)
2701 // Apply the "helpful master" concept if possible.
2702 if(SplitPointStack[slave][Threads[slave].activeSplitPoints-1].slaves[master])
2709 // idle_thread_exists() tries to find an idle thread which is available as
2710 // a slave for the thread with threadID "master".
2712 bool idle_thread_exists(int master) {
2713 assert(master >= 0 && master < ActiveThreads);
2714 assert(ActiveThreads > 1);
2716 for(int i = 0; i < ActiveThreads; i++)
2717 if(thread_is_available(i, master))
2723 // split() does the actual work of distributing the work at a node between
2724 // several threads at PV nodes. If it does not succeed in splitting the
2725 // node (because no idle threads are available, or because we have no unused
2726 // split point objects), the function immediately returns false. If
2727 // splitting is possible, a SplitPoint object is initialized with all the
2728 // data that must be copied to the helper threads (the current position and
2729 // search stack, alpha, beta, the search depth, etc.), and we tell our
2730 // helper threads that they have been assigned work. This will cause them
2731 // to instantly leave their idle loops and call sp_search_pv(). When all
2732 // threads have returned from sp_search_pv (or, equivalently, when
2733 // splitPoint->cpus becomes 0), split() returns true.
2735 bool split(const Position &p, SearchStack *sstck, int ply,
2736 Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
2737 MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) {
2740 assert(sstck != NULL);
2741 assert(ply >= 0 && ply < PLY_MAX);
2742 assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha);
2743 assert(!pvNode || *alpha < *beta);
2744 assert(*beta <= VALUE_INFINITE);
2745 assert(depth > Depth(0));
2746 assert(master >= 0 && master < ActiveThreads);
2747 assert(ActiveThreads > 1);
2749 SplitPoint *splitPoint;
2754 // If no other thread is available to help us, or if we have too many
2755 // active split points, don't split:
2756 if(!idle_thread_exists(master) ||
2757 Threads[master].activeSplitPoints >= MaxActiveSplitPoints) {
2758 lock_release(&MPLock);
2762 // Pick the next available split point object from the split point stack:
2763 splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
2764 Threads[master].activeSplitPoints++;
2766 // Initialize the split point object:
2767 splitPoint->parent = Threads[master].splitPoint;
2768 splitPoint->finished = false;
2769 splitPoint->ply = ply;
2770 splitPoint->depth = depth;
2771 splitPoint->alpha = pvNode? *alpha : (*beta - 1);
2772 splitPoint->beta = *beta;
2773 splitPoint->pvNode = pvNode;
2774 splitPoint->dcCandidates = dcCandidates;
2775 splitPoint->bestValue = *bestValue;
2776 splitPoint->master = master;
2777 splitPoint->mp = mp;
2778 splitPoint->moves = *moves;
2779 splitPoint->cpus = 1;
2780 splitPoint->pos.copy(p);
2781 splitPoint->parentSstack = sstck;
2782 for(i = 0; i < ActiveThreads; i++)
2783 splitPoint->slaves[i] = 0;
2785 // Copy the current position and the search stack to the master thread:
2786 memcpy(splitPoint->sstack[master], sstck, (ply+1)*sizeof(SearchStack));
2787 Threads[master].splitPoint = splitPoint;
2789 // Make copies of the current position and search stack for each thread:
2790 for(i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint;
2792 if(thread_is_available(i, master)) {
2793 memcpy(splitPoint->sstack[i], sstck, (ply+1)*sizeof(SearchStack));
2794 Threads[i].splitPoint = splitPoint;
2795 splitPoint->slaves[i] = 1;
2799 // Tell the threads that they have work to do. This will make them leave
2801 for(i = 0; i < ActiveThreads; i++)
2802 if(i == master || splitPoint->slaves[i]) {
2803 Threads[i].workIsWaiting = true;
2804 Threads[i].idle = false;
2805 Threads[i].stop = false;
2808 lock_release(&MPLock);
2810 // Everything is set up. The master thread enters the idle loop, from
2811 // which it will instantly launch a search, because its workIsWaiting
2812 // slot is 'true'. We send the split point as a second parameter to the
2813 // idle loop, which means that the main thread will return from the idle
2814 // loop when all threads have finished their work at this split point
2815 // (i.e. when // splitPoint->cpus == 0).
2816 idle_loop(master, splitPoint);
2818 // We have returned from the idle loop, which means that all threads are
2819 // finished. Update alpha, beta and bestvalue, and return:
2821 if(pvNode) *alpha = splitPoint->alpha;
2822 *beta = splitPoint->beta;
2823 *bestValue = splitPoint->bestValue;
2824 Threads[master].stop = false;
2825 Threads[master].idle = false;
2826 Threads[master].activeSplitPoints--;
2827 Threads[master].splitPoint = splitPoint->parent;
2828 lock_release(&MPLock);
2834 // wake_sleeping_threads() wakes up all sleeping threads when it is time
2835 // to start a new search from the root.
2837 void wake_sleeping_threads() {
2838 if(ActiveThreads > 1) {
2839 for(int i = 1; i < ActiveThreads; i++) {
2840 Threads[i].idle = true;
2841 Threads[i].workIsWaiting = false;
2843 #if !defined(_MSC_VER)
2844 pthread_mutex_lock(&WaitLock);
2845 pthread_cond_broadcast(&WaitCond);
2846 pthread_mutex_unlock(&WaitLock);
2848 for(int i = 1; i < THREAD_MAX; i++)
2849 SetEvent(SitIdleEvent[i]);
2855 // init_thread() is the function which is called when a new thread is
2856 // launched. It simply calls the idle_loop() function with the supplied
2857 // threadID. There are two versions of this function; one for POSIX threads
2858 // and one for Windows threads.
2860 #if !defined(_MSC_VER)
2862 void *init_thread(void *threadID) {
2863 idle_loop(*(int *)threadID, NULL);
2869 DWORD WINAPI init_thread(LPVOID threadID) {
2870 idle_loop(*(int *)threadID, NULL);