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/>.
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. The counters are per thread variables to avoid
76 // concurrent accessing under SMP case.
78 struct BetaCounterType {
82 void add(Color us, Depth d, int threadID);
83 void read(Color us, int64_t& our, int64_t& their);
87 // The RootMove class is used for moves at the root at the tree. For each
88 // root move, we store a score, a node count, and a PV (really a refutation
89 // in the case of moves which fail low).
94 bool operator<(const RootMove&); // used to sort
98 int64_t nodes, cumulativeNodes;
99 Move pv[PLY_MAX_PLUS_2];
100 int64_t ourBeta, theirBeta;
104 // The RootMoveList class is essentially an array of RootMove objects, with
105 // a handful of methods for accessing the data in the individual moves.
110 RootMoveList(Position &pos, Move searchMoves[]);
111 inline Move get_move(int moveNum) const;
112 inline Value get_move_score(int moveNum) const;
113 inline void set_move_score(int moveNum, Value score);
114 inline void set_move_nodes(int moveNum, int64_t nodes);
115 inline void set_beta_counters(int moveNum, int64_t our, int64_t their);
116 void set_move_pv(int moveNum, const Move pv[]);
117 inline Move get_move_pv(int moveNum, int i) const;
118 inline int64_t get_move_cumulative_nodes(int moveNum) const;
119 inline int move_count() const;
120 Move scan_for_easy_move() const;
122 void sort_multipv(int n);
125 static const int MaxRootMoves = 500;
126 RootMove moves[MaxRootMoves];
131 /// Constants and variables initialized from UCI options
133 // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
135 int LMRPVMoves, LMRNonPVMoves;
137 // Depth limit for use of dynamic threat detection
140 // Depth limit for selective search
141 const Depth SelectiveDepth = 7*OnePly;
143 // Use internal iterative deepening?
144 const bool UseIIDAtPVNodes = true;
145 const bool UseIIDAtNonPVNodes = false;
147 // Internal iterative deepening margin. At Non-PV moves, when
148 // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
149 // when the static evaluation is at most IIDMargin below beta.
150 const Value IIDMargin = Value(0x100);
152 // Easy move margin. An easy move candidate must be at least this much
153 // better than the second best move.
154 const Value EasyMoveMargin = Value(0x200);
156 // Problem margin. If the score of the first move at iteration N+1 has
157 // dropped by more than this since iteration N, the boolean variable
158 // "Problem" is set to true, which will make the program spend some extra
159 // time looking for a better move.
160 const Value ProblemMargin = Value(0x28);
162 // No problem margin. If the boolean "Problem" is true, and a new move
163 // is found at the root which is less than NoProblemMargin worse than the
164 // best move from the previous iteration, Problem is set back to false.
165 const Value NoProblemMargin = Value(0x14);
167 // Null move margin. A null move search will not be done if the approximate
168 // evaluation of the position is more than NullMoveMargin below beta.
169 const Value NullMoveMargin = Value(0x300);
171 // Pruning criterions. See the code and comments in ok_to_prune() to
172 // understand their precise meaning.
173 const bool PruneEscapeMoves = false;
174 const bool PruneDefendingMoves = false;
175 const bool PruneBlockingMoves = false;
177 // Use futility pruning?
178 bool UseQSearchFutilityPruning, UseFutilityPruning;
180 // Margins for futility pruning in the quiescence search, and at frontier
181 // and near frontier nodes
182 const Value FutilityMarginQS = Value(0x80);
184 // Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
185 const Value FutilityMargins[12] = { Value(0x100), Value(0x120), Value(0x200), Value(0x220), Value(0x250), Value(0x270),
186 // 4 ply 4.5 ply 5 ply 5.5 ply 6 ply 6.5 ply
187 Value(0x2A0), Value(0x2C0), Value(0x340), Value(0x360), Value(0x3A0), Value(0x3C0) };
189 const Depth RazorDepth = 4*OnePly;
191 // Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
192 const Value RazorMargins[6] = { Value(0x180), Value(0x300), Value(0x300), Value(0x3C0), Value(0x3C0), Value(0x3C0) };
194 // Remaining depth: 1 ply 1.5 ply 2 ply 2.5 ply 3 ply 3.5 ply
195 const Value RazorApprMargins[6] = { Value(0x520), Value(0x300), Value(0x300), Value(0x300), Value(0x300), Value(0x300) };
197 // Last seconds noise filtering (LSN)
198 bool UseLSNFiltering;
199 bool looseOnTime = false;
200 int LSNTime; // In milliseconds
203 // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
204 Depth CheckExtension[2], SingleReplyExtension[2], PawnPushTo7thExtension[2];
205 Depth PassedPawnExtension[2], PawnEndgameExtension[2], MateThreatExtension[2];
207 // Search depth at iteration 1
208 const Depth InitialDepth = OnePly /*+ OnePly/2*/;
215 int NodesBetweenPolls = 30000;
217 // Iteration counters
219 BetaCounterType BetaCounter;
221 // Scores and number of times the best move changed for each iteration:
222 IterationInfoType IterationInfo[PLY_MAX_PLUS_2];
223 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
228 // Time managment variables
230 int MaxNodes, MaxDepth;
231 int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
236 bool StopOnPonderhit;
242 bool PonderingEnabled;
245 // Show current line?
246 bool ShowCurrentLine;
250 std::ofstream LogFile;
252 // MP related variables
253 Depth MinimumSplitDepth;
254 int MaxThreadsPerSplitPoint;
255 Thread Threads[THREAD_MAX];
257 bool AllThreadsShouldExit = false;
258 const int MaxActiveSplitPoints = 8;
259 SplitPoint SplitPointStack[THREAD_MAX][MaxActiveSplitPoints];
262 #if !defined(_MSC_VER)
263 pthread_cond_t WaitCond;
264 pthread_mutex_t WaitLock;
266 HANDLE SitIdleEvent[THREAD_MAX];
272 Value id_loop(const Position &pos, Move searchMoves[]);
273 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta);
274 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
275 Value search(Position &pos, SearchStack ss[], Value beta, Depth depth, int ply, bool allowNullmove, int threadID);
276 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta, Depth depth, int ply, int threadID);
277 void sp_search(SplitPoint *sp, int threadID);
278 void sp_search_pv(SplitPoint *sp, int threadID);
279 void init_node(SearchStack ss[], int ply, int threadID);
280 void update_pv(SearchStack ss[], int ply);
281 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
282 bool connected_moves(const Position &pos, Move m1, Move m2);
283 bool value_is_mate(Value value);
284 bool move_is_killer(Move m, const SearchStack& ss);
285 Depth extension(const Position &pos, Move m, bool pvNode, bool capture, bool check, bool singleReply, bool mateThreat, bool* dangerous);
286 bool ok_to_do_nullmove(const Position &pos);
287 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
288 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply);
289 bool ok_to_history(const Position &pos, Move m);
290 void update_history(const Position& pos, Move m, Depth depth, Move movesSearched[], int moveCount);
291 void update_killers(Move m, SearchStack& ss);
293 bool fail_high_ply_1();
294 int current_search_time();
298 void print_current_line(SearchStack ss[], int ply, int threadID);
299 void wait_for_stop_or_ponderhit();
301 void idle_loop(int threadID, SplitPoint *waitSp);
302 void init_split_point_stack();
303 void destroy_split_point_stack();
304 bool thread_should_stop(int threadID);
305 bool thread_is_available(int slave, int master);
306 bool idle_thread_exists(int master);
307 bool split(const Position &pos, SearchStack *ss, int ply,
308 Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
309 MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode);
310 void wake_sleeping_threads();
312 #if !defined(_MSC_VER)
313 void *init_thread(void *threadID);
315 DWORD WINAPI init_thread(LPVOID threadID);
322 //// Global variables
325 // The main transposition table
326 TranspositionTable TT;
329 // Number of active threads:
330 int ActiveThreads = 1;
332 // Locks. In principle, there is no need for IOLock to be a global variable,
333 // but it could turn out to be useful for debugging.
337 // SearchStack::init() initializes a search stack. Used at the beginning of a
338 // new search from the root.
339 void SearchStack::init(int ply) {
341 pv[ply] = pv[ply + 1] = MOVE_NONE;
342 currentMove = threatMove = MOVE_NONE;
343 reduction = Depth(0);
346 void SearchStack::initKillers() {
348 mateKiller = MOVE_NONE;
349 for (int i = 0; i < KILLER_MAX; i++)
350 killers[i] = MOVE_NONE;
358 /// think() is the external interface to Stockfish's search, and is called when
359 /// the program receives the UCI 'go' command. It initializes various
360 /// search-related global variables, and calls root_search(). It returns false
361 /// when a quit command is received during the search.
363 bool think(const Position &pos, bool infinite, bool ponder, int side_to_move,
364 int time[], int increment[], int movesToGo, int maxDepth,
365 int maxNodes, int maxTime, Move searchMoves[]) {
367 // Look for a book move
368 if (!infinite && !ponder && get_option_value_bool("OwnBook"))
371 if (get_option_value_string("Book File") != OpeningBook.file_name())
372 OpeningBook.open("book.bin");
374 bookMove = OpeningBook.get_move(pos);
375 if (bookMove != MOVE_NONE)
377 std::cout << "bestmove " << bookMove << std::endl;
382 // Initialize global search variables
384 SearchStartTime = get_system_time();
385 EasyMove = MOVE_NONE;
386 for (int i = 0; i < THREAD_MAX; i++)
388 Threads[i].nodes = 0ULL;
389 Threads[i].failHighPly1 = false;
392 InfiniteSearch = infinite;
393 PonderSearch = ponder;
394 StopOnPonderhit = false;
400 ExactMaxTime = maxTime;
402 // Read UCI option values
403 TT.set_size(get_option_value_int("Hash"));
404 if (button_was_pressed("Clear Hash"))
407 PonderingEnabled = get_option_value_bool("Ponder");
408 MultiPV = get_option_value_int("MultiPV");
410 CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
411 CheckExtension[0] = Depth(get_option_value_int("Check Extension (non-PV nodes)"));
413 SingleReplyExtension[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)"));
414 SingleReplyExtension[0] = Depth(get_option_value_int("Single Reply Extension (non-PV nodes)"));
416 PawnPushTo7thExtension[1] = Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
417 PawnPushTo7thExtension[0] = Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
419 PassedPawnExtension[1] = Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
420 PassedPawnExtension[0] = Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
422 PawnEndgameExtension[1] = Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
423 PawnEndgameExtension[0] = Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
425 MateThreatExtension[1] = Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
426 MateThreatExtension[0] = Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
428 LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
429 LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
430 ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
432 Chess960 = get_option_value_bool("UCI_Chess960");
433 ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
434 UseLogFile = get_option_value_bool("Use Search Log");
436 LogFile.open(get_option_value_string("Search Log Filename").c_str(), std::ios::out | std::ios::app);
438 UseQSearchFutilityPruning = get_option_value_bool("Futility Pruning (Quiescence Search)");
439 UseFutilityPruning = get_option_value_bool("Futility Pruning (Main Search)");
441 UseLSNFiltering = get_option_value_bool("LSN filtering");
442 LSNTime = get_option_value_int("LSN Time Margin (sec)") * 1000;
443 LSNValue = value_from_centipawns(get_option_value_int("LSN Value Margin"));
445 MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
446 MaxThreadsPerSplitPoint = get_option_value_int("Maximum Number of Threads per Split Point");
448 read_weights(pos.side_to_move());
450 int newActiveThreads = get_option_value_int("Threads");
451 if (newActiveThreads != ActiveThreads)
453 ActiveThreads = newActiveThreads;
454 init_eval(ActiveThreads);
457 // Wake up sleeping threads:
458 wake_sleeping_threads();
460 for (int i = 1; i < ActiveThreads; i++)
461 assert(thread_is_available(i, 0));
463 // Set thinking time:
464 int myTime = time[side_to_move];
465 int myIncrement = increment[side_to_move];
467 if (!movesToGo) // Sudden death time control
471 MaxSearchTime = myTime / 30 + myIncrement;
472 AbsoluteMaxSearchTime = Max(myTime / 4, myIncrement - 100);
473 } else { // Blitz game without increment
474 MaxSearchTime = myTime / 30;
475 AbsoluteMaxSearchTime = myTime / 8;
478 else // (x moves) / (y minutes)
482 MaxSearchTime = myTime / 2;
483 AbsoluteMaxSearchTime = Min(myTime / 2, myTime - 500);
485 MaxSearchTime = myTime / Min(movesToGo, 20);
486 AbsoluteMaxSearchTime = Min((4 * myTime) / movesToGo, myTime / 3);
490 if (PonderingEnabled)
492 MaxSearchTime += MaxSearchTime / 4;
493 MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
496 // Fixed depth or fixed number of nodes?
499 InfiniteSearch = true; // HACK
504 NodesBetweenPolls = Min(MaxNodes, 30000);
505 InfiniteSearch = true; // HACK
508 NodesBetweenPolls = 30000;
511 // Write information to search log file:
513 LogFile << "Searching: " << pos.to_fen() << std::endl
514 << "infinite: " << infinite
515 << " ponder: " << ponder
516 << " time: " << myTime
517 << " increment: " << myIncrement
518 << " moves to go: " << movesToGo << std::endl;
521 // We're ready to start thinking. Call the iterative deepening loop
525 Value v = id_loop(pos, searchMoves);
526 looseOnTime = ( UseLSNFiltering
533 looseOnTime = false; // reset for next match
534 while (SearchStartTime + myTime + 1000 > get_system_time())
536 id_loop(pos, searchMoves); // to fail gracefully
547 /// init_threads() is called during startup. It launches all helper threads,
548 /// and initializes the split point stack and the global locks and condition
551 void init_threads() {
555 #if !defined(_MSC_VER)
556 pthread_t pthread[1];
559 for (i = 0; i < THREAD_MAX; i++)
560 Threads[i].activeSplitPoints = 0;
562 // Initialize global locks:
563 lock_init(&MPLock, NULL);
564 lock_init(&IOLock, NULL);
566 init_split_point_stack();
568 #if !defined(_MSC_VER)
569 pthread_mutex_init(&WaitLock, NULL);
570 pthread_cond_init(&WaitCond, NULL);
572 for (i = 0; i < THREAD_MAX; i++)
573 SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
576 // All threads except the main thread should be initialized to idle state
577 for (i = 1; i < THREAD_MAX; i++)
579 Threads[i].stop = false;
580 Threads[i].workIsWaiting = false;
581 Threads[i].idle = true;
582 Threads[i].running = false;
585 // Launch the helper threads
586 for(i = 1; i < THREAD_MAX; i++)
588 #if !defined(_MSC_VER)
589 pthread_create(pthread, NULL, init_thread, (void*)(&i));
592 CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
595 // Wait until the thread has finished launching:
596 while (!Threads[i].running);
601 /// stop_threads() is called when the program exits. It makes all the
602 /// helper threads exit cleanly.
604 void stop_threads() {
606 ActiveThreads = THREAD_MAX; // HACK
607 Idle = false; // HACK
608 wake_sleeping_threads();
609 AllThreadsShouldExit = true;
610 for (int i = 1; i < THREAD_MAX; i++)
612 Threads[i].stop = true;
613 while(Threads[i].running);
615 destroy_split_point_stack();
619 /// nodes_searched() returns the total number of nodes searched so far in
620 /// the current search.
622 int64_t nodes_searched() {
624 int64_t result = 0ULL;
625 for (int i = 0; i < ActiveThreads; i++)
626 result += Threads[i].nodes;
633 // id_loop() is the main iterative deepening loop. It calls root_search
634 // repeatedly with increasing depth until the allocated thinking time has
635 // been consumed, the user stops the search, or the maximum search depth is
638 Value id_loop(const Position &pos, Move searchMoves[]) {
641 SearchStack ss[PLY_MAX_PLUS_2];
643 // searchMoves are verified, copied, scored and sorted
644 RootMoveList rml(p, searchMoves);
649 for (int i = 0; i < 3; i++)
654 IterationInfo[1] = IterationInfoType(rml.get_move_score(0), rml.get_move_score(0));
657 EasyMove = rml.scan_for_easy_move();
659 // Iterative deepening loop
660 while (Iteration < PLY_MAX)
662 // Initialize iteration
665 BestMoveChangesByIteration[Iteration] = 0;
669 std::cout << "info depth " << Iteration << std::endl;
671 // Calculate dynamic search window based on previous iterations
674 if (MultiPV == 1 && Iteration >= 6)
676 int prevDelta1 = IterationInfo[Iteration - 1].speculatedValue - IterationInfo[Iteration - 2].speculatedValue;
677 int prevDelta2 = IterationInfo[Iteration - 2].speculatedValue - IterationInfo[Iteration - 3].speculatedValue;
679 int delta = Max(2 * abs(prevDelta1) + abs(prevDelta2), ProblemMargin);
681 alpha = Max(IterationInfo[Iteration - 1].value - delta, -VALUE_INFINITE);
682 beta = Min(IterationInfo[Iteration - 1].value + delta, VALUE_INFINITE);
686 alpha = - VALUE_INFINITE;
687 beta = VALUE_INFINITE;
690 // Search to the current depth
691 Value value = root_search(p, ss, rml, alpha, beta);
693 // Write PV to transposition table, in case the relevant entries have
694 // been overwritten during the search.
695 TT.insert_pv(p, ss[0].pv);
698 break; // Value cannot be trusted. Break out immediately!
700 //Save info about search result
701 Value speculatedValue;
704 Value delta = value - IterationInfo[Iteration - 1].value;
711 speculatedValue = value + delta;
712 BestMoveChangesByIteration[Iteration] += 2; // Allocate more time
714 else if (value <= alpha)
716 assert(value == alpha);
720 speculatedValue = value + delta;
721 BestMoveChangesByIteration[Iteration] += 3; // Allocate more time
723 speculatedValue = value;
725 speculatedValue = Min(Max(speculatedValue, -VALUE_INFINITE), VALUE_INFINITE);
726 IterationInfo[Iteration] = IterationInfoType(value, speculatedValue);
728 // Erase the easy move if it differs from the new best move
729 if (ss[0].pv[0] != EasyMove)
730 EasyMove = MOVE_NONE;
737 bool stopSearch = false;
739 // Stop search early if there is only a single legal move:
740 if (Iteration >= 6 && rml.move_count() == 1)
743 // Stop search early when the last two iterations returned a mate score
745 && abs(IterationInfo[Iteration].value) >= abs(VALUE_MATE) - 100
746 && abs(IterationInfo[Iteration-1].value) >= abs(VALUE_MATE) - 100)
749 // Stop search early if one move seems to be much better than the rest
750 int64_t nodes = nodes_searched();
754 && EasyMove == ss[0].pv[0]
755 && ( ( rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100
756 && current_search_time() > MaxSearchTime / 16)
757 ||( rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100
758 && current_search_time() > MaxSearchTime / 32)))
761 // Add some extra time if the best move has changed during the last two iterations
762 if (Iteration > 5 && Iteration <= 50)
763 ExtraSearchTime = BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2)
764 + BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
766 // Stop search if most of MaxSearchTime is consumed at the end of the
767 // iteration. We probably don't have enough time to search the first
768 // move at the next iteration anyway.
769 if (current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128)
774 //FIXME: Implement fail-low emergency measures
778 StopOnPonderhit = true;
782 if (MaxDepth && Iteration >= MaxDepth)
788 // If we are pondering, we shouldn't print the best move before we
791 wait_for_stop_or_ponderhit();
793 // Print final search statistics
794 std::cout << "info nodes " << nodes_searched()
796 << " time " << current_search_time()
797 << " hashfull " << TT.full() << std::endl;
799 // Print the best move and the ponder move to the standard output
800 if (ss[0].pv[0] == MOVE_NONE)
802 ss[0].pv[0] = rml.get_move(0);
803 ss[0].pv[1] = MOVE_NONE;
805 std::cout << "bestmove " << ss[0].pv[0];
806 if (ss[0].pv[1] != MOVE_NONE)
807 std::cout << " ponder " << ss[0].pv[1];
809 std::cout << std::endl;
814 dbg_print_mean(LogFile);
816 if (dbg_show_hit_rate)
817 dbg_print_hit_rate(LogFile);
820 LogFile << "Nodes: " << nodes_searched() << std::endl
821 << "Nodes/second: " << nps() << std::endl
822 << "Best move: " << move_to_san(p, ss[0].pv[0]) << std::endl;
824 p.do_move(ss[0].pv[0], st);
825 LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1])
826 << std::endl << std::endl;
828 return rml.get_move_score(0);
832 // root_search() is the function which searches the root node. It is
833 // similar to search_pv except that it uses a different move ordering
834 // scheme (perhaps we should try to use this at internal PV nodes, too?)
835 // and prints some information to the standard output.
837 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml, Value alpha, Value beta) {
839 Value oldAlpha = alpha;
841 Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
843 // Loop through all the moves in the root move list
844 for (int i = 0; i < rml.move_count() && !AbortSearch; i++)
848 // We failed high, invalidate and skip next moves, leave node-counters
849 // and beta-counters as they are and quickly return, we will try to do
850 // a research at the next iteration with a bigger aspiration window.
851 rml.set_move_score(i, -VALUE_INFINITE);
859 RootMoveNumber = i + 1;
862 // Remember the node count before the move is searched. The node counts
863 // are used to sort the root moves at the next iteration.
864 nodes = nodes_searched();
866 // Reset beta cut-off counters
869 // Pick the next root move, and print the move and the move number to
870 // the standard output.
871 move = ss[0].currentMove = rml.get_move(i);
872 if (current_search_time() >= 1000)
873 std::cout << "info currmove " << move
874 << " currmovenumber " << i + 1 << std::endl;
876 // Decide search depth for this move
878 ext = extension(pos, move, true, pos.move_is_capture(move), pos.move_is_check(move), false, false, &dangerous);
879 newDepth = (Iteration - 2) * OnePly + ext + InitialDepth;
881 // Make the move, and search it
882 pos.do_move(move, st, dcCandidates);
886 // Aspiration window is disabled in multi-pv case
888 alpha = -VALUE_INFINITE;
890 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
891 // If the value has dropped a lot compared to the last iteration,
892 // set the boolean variable Problem to true. This variable is used
893 // for time managment: When Problem is true, we try to complete the
894 // current iteration before playing a move.
895 Problem = (Iteration >= 2 && value <= IterationInfo[Iteration-1].value - ProblemMargin);
897 if (Problem && StopOnPonderhit)
898 StopOnPonderhit = false;
902 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
905 // Fail high! Set the boolean variable FailHigh to true, and
906 // re-search the move with a big window. The variable FailHigh is
907 // used for time managment: We try to avoid aborting the search
908 // prematurely during a fail high research.
910 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
916 // Finished searching the move. If AbortSearch is true, the search
917 // was aborted because the user interrupted the search or because we
918 // ran out of time. In this case, the return value of the search cannot
919 // be trusted, and we break out of the loop without updating the best
924 // Remember the node count for this move. The node counts are used to
925 // sort the root moves at the next iteration.
926 rml.set_move_nodes(i, nodes_searched() - nodes);
928 // Remember the beta-cutoff statistics
930 BetaCounter.read(pos.side_to_move(), our, their);
931 rml.set_beta_counters(i, our, their);
933 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
935 if (value <= alpha && i >= MultiPV)
936 rml.set_move_score(i, -VALUE_INFINITE);
939 // PV move or new best move!
942 rml.set_move_score(i, value);
944 rml.set_move_pv(i, ss[0].pv);
948 // We record how often the best move has been changed in each
949 // iteration. This information is used for time managment: When
950 // the best move changes frequently, we allocate some more time.
952 BestMoveChangesByIteration[Iteration]++;
954 // Print search information to the standard output:
955 std::cout << "info depth " << Iteration
956 << " score " << value_to_string(value)
957 << " time " << current_search_time()
958 << " nodes " << nodes_searched()
962 for (int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
963 std::cout << ss[0].pv[j] << " ";
965 std::cout << std::endl;
968 LogFile << pretty_pv(pos, current_search_time(), Iteration, nodes_searched(), value, ss[0].pv)
974 // Reset the global variable Problem to false if the value isn't too
975 // far below the final value from the last iteration.
976 if (value > IterationInfo[Iteration - 1].value - NoProblemMargin)
982 for (int j = 0; j < Min(MultiPV, rml.move_count()); j++)
985 std::cout << "info multipv " << j + 1
986 << " score " << value_to_string(rml.get_move_score(j))
987 << " depth " << ((j <= i)? Iteration : Iteration - 1)
988 << " time " << current_search_time()
989 << " nodes " << nodes_searched()
993 for (k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
994 std::cout << rml.get_move_pv(j, k) << " ";
996 std::cout << std::endl;
998 alpha = rml.get_move_score(Min(i, MultiPV-1));
1000 } // New best move case
1002 assert(alpha >= oldAlpha);
1004 FailLow = (alpha == oldAlpha);
1010 // search_pv() is the main search function for PV nodes.
1012 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
1013 Depth depth, int ply, int threadID) {
1015 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1016 assert(beta > alpha && beta <= VALUE_INFINITE);
1017 assert(ply >= 0 && ply < PLY_MAX);
1018 assert(threadID >= 0 && threadID < ActiveThreads);
1021 return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
1023 // Initialize, and make an early exit in case of an aborted search,
1024 // an instant draw, maximum ply reached, etc.
1025 init_node(ss, ply, threadID);
1027 // After init_node() that calls poll()
1028 if (AbortSearch || thread_should_stop(threadID))
1036 if (ply >= PLY_MAX - 1)
1037 return evaluate(pos, ei, threadID);
1039 // Mate distance pruning
1040 Value oldAlpha = alpha;
1041 alpha = Max(value_mated_in(ply), alpha);
1042 beta = Min(value_mate_in(ply+1), beta);
1046 // Transposition table lookup. At PV nodes, we don't use the TT for
1047 // pruning, but only for move ordering.
1048 const TTEntry* tte = TT.retrieve(pos.get_key());
1049 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1051 // Go with internal iterative deepening if we don't have a TT move
1052 if (UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly)
1054 search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
1055 ttMove = ss[ply].pv[ply];
1058 // Initialize a MovePicker object for the current position, and prepare
1059 // to search all moves
1060 MovePicker mp = MovePicker(pos, true, ttMove, depth, H, &ss[ply]);
1062 Move move, movesSearched[256];
1064 Value value, bestValue = -VALUE_INFINITE;
1065 Bitboard dcCandidates = mp.discovered_check_candidates();
1066 Color us = pos.side_to_move();
1067 bool isCheck = pos.is_check();
1068 bool mateThreat = pos.has_mate_threat(opposite_color(us));
1070 // Loop through all legal moves until no moves remain or a beta cutoff
1072 while ( alpha < beta
1073 && (move = mp.get_next_move()) != MOVE_NONE
1074 && !thread_should_stop(threadID))
1076 assert(move_is_ok(move));
1078 bool singleReply = (isCheck && mp.number_of_moves() == 1);
1079 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1080 bool moveIsCapture = pos.move_is_capture(move);
1082 movesSearched[moveCount++] = ss[ply].currentMove = move;
1084 // Decide the new search depth
1086 Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous);
1087 Depth newDepth = depth - OnePly + ext;
1089 // Make and search the move
1091 pos.do_move(move, st, dcCandidates);
1093 if (moveCount == 1) // The first move in list is the PV
1094 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1097 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1098 // if the move fails high will be re-searched at full depth.
1099 if ( depth >= 2*OnePly
1100 && moveCount >= LMRPVMoves
1103 && !move_promotion(move)
1104 && !move_is_castle(move)
1105 && !move_is_killer(move, ss[ply]))
1107 ss[ply].reduction = OnePly;
1108 value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true, threadID);
1111 value = alpha + 1; // Just to trigger next condition
1113 if (value > alpha) // Go with full depth non-pv search
1115 ss[ply].reduction = Depth(0);
1116 value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
1117 if (value > alpha && value < beta)
1119 // When the search fails high at ply 1 while searching the first
1120 // move at the root, set the flag failHighPly1. This is used for
1121 // time managment: We don't want to stop the search early in
1122 // such cases, because resolving the fail high at ply 1 could
1123 // result in a big drop in score at the root.
1124 if (ply == 1 && RootMoveNumber == 1)
1125 Threads[threadID].failHighPly1 = true;
1127 // A fail high occurred. Re-search at full window (pv search)
1128 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
1129 Threads[threadID].failHighPly1 = false;
1133 pos.undo_move(move);
1135 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1138 if (value > bestValue)
1145 if (value == value_mate_in(ply + 1))
1146 ss[ply].mateKiller = move;
1148 // If we are at ply 1, and we are searching the first root move at
1149 // ply 0, set the 'Problem' variable if the score has dropped a lot
1150 // (from the computer's point of view) since the previous iteration:
1153 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
1158 if ( ActiveThreads > 1
1160 && depth >= MinimumSplitDepth
1162 && idle_thread_exists(threadID)
1164 && !thread_should_stop(threadID)
1165 && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
1166 &moveCount, &mp, dcCandidates, threadID, true))
1170 // All legal moves have been searched. A special case: If there were
1171 // no legal moves, it must be mate or stalemate:
1173 return (isCheck ? value_mated_in(ply) : VALUE_DRAW);
1175 // If the search is not aborted, update the transposition table,
1176 // history counters, and killer moves.
1177 if (AbortSearch || thread_should_stop(threadID))
1180 if (bestValue <= oldAlpha)
1181 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
1183 else if (bestValue >= beta)
1185 BetaCounter.add(pos.side_to_move(), depth, threadID);
1186 Move m = ss[ply].pv[ply];
1187 if (ok_to_history(pos, m)) // Only non capture moves are considered
1189 update_history(pos, m, depth, movesSearched, moveCount);
1190 update_killers(m, ss[ply]);
1192 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m);
1195 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EXACT, depth, ss[ply].pv[ply]);
1201 // search() is the search function for zero-width nodes.
1203 Value search(Position &pos, SearchStack ss[], Value beta, Depth depth,
1204 int ply, bool allowNullmove, int threadID) {
1206 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1207 assert(ply >= 0 && ply < PLY_MAX);
1208 assert(threadID >= 0 && threadID < ActiveThreads);
1211 return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1213 // Initialize, and make an early exit in case of an aborted search,
1214 // an instant draw, maximum ply reached, etc.
1215 init_node(ss, ply, threadID);
1217 // After init_node() that calls poll()
1218 if (AbortSearch || thread_should_stop(threadID))
1226 if (ply >= PLY_MAX - 1)
1227 return evaluate(pos, ei, threadID);
1229 // Mate distance pruning
1230 if (value_mated_in(ply) >= beta)
1233 if (value_mate_in(ply + 1) < beta)
1236 // Transposition table lookup
1237 const TTEntry* tte = TT.retrieve(pos.get_key());
1238 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1240 if (tte && ok_to_use_TT(tte, depth, beta, ply))
1242 ss[ply].currentMove = ttMove; // can be MOVE_NONE
1243 return value_from_tt(tte->value(), ply);
1246 Value approximateEval = quick_evaluate(pos);
1247 bool mateThreat = false;
1248 bool isCheck = pos.is_check();
1254 && !value_is_mate(beta)
1255 && ok_to_do_nullmove(pos)
1256 && approximateEval >= beta - NullMoveMargin)
1258 ss[ply].currentMove = MOVE_NULL;
1261 pos.do_null_move(st);
1262 int R = (depth >= 5 * OnePly ? 4 : 3); // Null move dynamic reduction
1264 Value nullValue = -search(pos, ss, -(beta-1), depth-R*OnePly, ply+1, false, threadID);
1266 pos.undo_null_move();
1268 if (value_is_mate(nullValue))
1270 /* Do not return unproven mates */
1272 else if (nullValue >= beta)
1274 if (depth < 6 * OnePly)
1277 // Do zugzwang verification search
1278 Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
1282 // The null move failed low, which means that we may be faced with
1283 // some kind of threat. If the previous move was reduced, check if
1284 // the move that refuted the null move was somehow connected to the
1285 // move which was reduced. If a connection is found, return a fail
1286 // low score (which will cause the reduced move to fail high in the
1287 // parent node, which will trigger a re-search with full depth).
1288 if (nullValue == value_mated_in(ply + 2))
1291 ss[ply].threatMove = ss[ply + 1].currentMove;
1292 if ( depth < ThreatDepth
1293 && ss[ply - 1].reduction
1294 && connected_moves(pos, ss[ply - 1].currentMove, ss[ply].threatMove))
1298 // Null move search not allowed, try razoring
1299 else if ( !value_is_mate(beta)
1300 && depth < RazorDepth
1301 && approximateEval < beta - RazorApprMargins[int(depth) - 2]
1302 && ss[ply - 1].currentMove != MOVE_NULL
1303 && ttMove == MOVE_NONE
1304 && !pos.has_pawn_on_7th(pos.side_to_move()))
1306 Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1307 if (v < beta - RazorMargins[int(depth) - 2])
1311 // Go with internal iterative deepening if we don't have a TT move
1312 if (UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
1313 evaluate(pos, ei, threadID) >= beta - IIDMargin)
1315 search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
1316 ttMove = ss[ply].pv[ply];
1319 // Initialize a MovePicker object for the current position, and prepare
1320 // to search all moves:
1321 MovePicker mp = MovePicker(pos, false, ttMove, depth, H, &ss[ply]);
1323 Move move, movesSearched[256];
1325 Value value, bestValue = -VALUE_INFINITE;
1326 Bitboard dcCandidates = mp.discovered_check_candidates();
1327 Value futilityValue = VALUE_NONE;
1328 bool useFutilityPruning = UseFutilityPruning
1329 && depth < SelectiveDepth
1332 // Loop through all legal moves until no moves remain or a beta cutoff
1334 while ( bestValue < beta
1335 && (move = mp.get_next_move()) != MOVE_NONE
1336 && !thread_should_stop(threadID))
1338 assert(move_is_ok(move));
1340 bool singleReply = (isCheck && mp.number_of_moves() == 1);
1341 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1342 bool moveIsCapture = pos.move_is_capture(move);
1344 movesSearched[moveCount++] = ss[ply].currentMove = move;
1346 // Decide the new search depth
1348 Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, singleReply, mateThreat, &dangerous);
1349 Depth newDepth = depth - OnePly + ext;
1352 if ( useFutilityPruning
1355 && !move_promotion(move))
1357 // History pruning. See ok_to_prune() definition
1358 if ( moveCount >= 2 + int(depth)
1359 && ok_to_prune(pos, move, ss[ply].threatMove, depth))
1362 // Value based pruning
1363 if (approximateEval < beta)
1365 if (futilityValue == VALUE_NONE)
1366 futilityValue = evaluate(pos, ei, threadID)
1367 + FutilityMargins[int(depth) - 2];
1369 if (futilityValue < beta)
1371 if (futilityValue > bestValue)
1372 bestValue = futilityValue;
1378 // Make and search the move
1380 pos.do_move(move, st, dcCandidates);
1382 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1383 // if the move fails high will be re-searched at full depth.
1384 if ( depth >= 2*OnePly
1385 && moveCount >= LMRNonPVMoves
1388 && !move_promotion(move)
1389 && !move_is_castle(move)
1390 && !move_is_killer(move, ss[ply]))
1392 ss[ply].reduction = OnePly;
1393 value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true, threadID);
1396 value = beta; // Just to trigger next condition
1398 if (value >= beta) // Go with full depth non-pv search
1400 ss[ply].reduction = Depth(0);
1401 value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
1403 pos.undo_move(move);
1405 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1408 if (value > bestValue)
1414 if (value == value_mate_in(ply + 1))
1415 ss[ply].mateKiller = move;
1419 if ( ActiveThreads > 1
1421 && depth >= MinimumSplitDepth
1423 && idle_thread_exists(threadID)
1425 && !thread_should_stop(threadID)
1426 && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
1427 &mp, dcCandidates, threadID, false))
1431 // All legal moves have been searched. A special case: If there were
1432 // no legal moves, it must be mate or stalemate.
1434 return (pos.is_check() ? value_mated_in(ply) : VALUE_DRAW);
1436 // If the search is not aborted, update the transposition table,
1437 // history counters, and killer moves.
1438 if (AbortSearch || thread_should_stop(threadID))
1441 if (bestValue < beta)
1442 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, depth, MOVE_NONE);
1445 BetaCounter.add(pos.side_to_move(), depth, threadID);
1446 Move m = ss[ply].pv[ply];
1447 if (ok_to_history(pos, m)) // Only non capture moves are considered
1449 update_history(pos, m, depth, movesSearched, moveCount);
1450 update_killers(m, ss[ply]);
1452 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, depth, m);
1455 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1461 // qsearch() is the quiescence search function, which is called by the main
1462 // search function when the remaining depth is zero (or, to be more precise,
1463 // less than OnePly).
1465 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
1466 Depth depth, int ply, int threadID) {
1468 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1469 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1471 assert(ply >= 0 && ply < PLY_MAX);
1472 assert(threadID >= 0 && threadID < ActiveThreads);
1474 // Initialize, and make an early exit in case of an aborted search,
1475 // an instant draw, maximum ply reached, etc.
1476 init_node(ss, ply, threadID);
1478 // After init_node() that calls poll()
1479 if (AbortSearch || thread_should_stop(threadID))
1485 // Transposition table lookup, only when not in PV
1486 TTEntry* tte = NULL;
1487 bool pvNode = (beta - alpha != 1);
1490 tte = TT.retrieve(pos.get_key());
1491 if (tte && ok_to_use_TT(tte, depth, beta, ply))
1493 assert(tte->type() != VALUE_TYPE_EVAL);
1495 return value_from_tt(tte->value(), ply);
1498 Move ttMove = (tte ? tte->move() : MOVE_NONE);
1500 // Evaluate the position statically
1503 bool isCheck = pos.is_check();
1504 ei.futilityMargin = Value(0); // Manually initialize futilityMargin
1507 staticValue = -VALUE_INFINITE;
1509 else if (tte && tte->type() == VALUE_TYPE_EVAL)
1511 // Use the cached evaluation score if possible
1512 assert(tte->value() == evaluate(pos, ei, threadID));
1513 assert(ei.futilityMargin == Value(0));
1515 staticValue = tte->value();
1518 staticValue = evaluate(pos, ei, threadID);
1520 if (ply == PLY_MAX - 1)
1521 return evaluate(pos, ei, threadID);
1523 // Initialize "stand pat score", and return it immediately if it is
1525 Value bestValue = staticValue;
1527 if (bestValue >= beta)
1529 // Store the score to avoid a future costly evaluation() call
1530 if (!isCheck && !tte && ei.futilityMargin == 0)
1531 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_EVAL, Depth(-127*OnePly), MOVE_NONE);
1536 if (bestValue > alpha)
1539 // Initialize a MovePicker object for the current position, and prepare
1540 // to search the moves. Because the depth is <= 0 here, only captures,
1541 // queen promotions and checks (only if depth == 0) will be generated.
1542 MovePicker mp = MovePicker(pos, pvNode, ttMove, depth, H);
1545 Bitboard dcCandidates = mp.discovered_check_candidates();
1546 Color us = pos.side_to_move();
1547 bool enoughMaterial = pos.non_pawn_material(us) > RookValueMidgame;
1549 // Loop through the moves until no moves remain or a beta cutoff
1551 while ( alpha < beta
1552 && (move = mp.get_next_move()) != MOVE_NONE)
1554 assert(move_is_ok(move));
1557 ss[ply].currentMove = move;
1560 if ( UseQSearchFutilityPruning
1564 && !move_promotion(move)
1565 && !pos.move_is_check(move, dcCandidates)
1566 && !pos.move_is_passed_pawn_push(move))
1568 Value futilityValue = staticValue
1569 + Max(pos.midgame_value_of_piece_on(move_to(move)),
1570 pos.endgame_value_of_piece_on(move_to(move)))
1571 + (move_is_ep(move) ? PawnValueEndgame : Value(0))
1573 + ei.futilityMargin;
1575 if (futilityValue < alpha)
1577 if (futilityValue > bestValue)
1578 bestValue = futilityValue;
1583 // Don't search captures and checks with negative SEE values
1585 && !move_promotion(move)
1586 && (pos.midgame_value_of_piece_on(move_from(move)) >
1587 pos.midgame_value_of_piece_on(move_to(move)))
1588 && pos.see(move) < 0)
1591 // Make and search the move.
1593 pos.do_move(move, st, dcCandidates);
1594 Value value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
1595 pos.undo_move(move);
1597 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1600 if (value > bestValue)
1611 // All legal moves have been searched. A special case: If we're in check
1612 // and no legal moves were found, it is checkmate:
1613 if (pos.is_check() && moveCount == 0) // Mate!
1614 return value_mated_in(ply);
1616 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1618 // Update transposition table
1619 Move m = ss[ply].pv[ply];
1622 Depth d = (depth == Depth(0) ? Depth(0) : Depth(-1));
1623 if (bestValue < beta)
1624 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_UPPER, d, MOVE_NONE);
1626 TT.store(pos.get_key(), value_to_tt(bestValue, ply), VALUE_TYPE_LOWER, d, m);
1629 // Update killers only for good check moves
1630 if (alpha >= beta && ok_to_history(pos, m)) // Only non capture moves are considered
1631 update_killers(m, ss[ply]);
1637 // sp_search() is used to search from a split point. This function is called
1638 // by each thread working at the split point. It is similar to the normal
1639 // search() function, but simpler. Because we have already probed the hash
1640 // table, done a null move search, and searched the first move before
1641 // splitting, we don't have to repeat all this work in sp_search(). We
1642 // also don't need to store anything to the hash table here: This is taken
1643 // care of after we return from the split point.
1645 void sp_search(SplitPoint *sp, int threadID) {
1647 assert(threadID >= 0 && threadID < ActiveThreads);
1648 assert(ActiveThreads > 1);
1650 Position pos = Position(sp->pos);
1651 SearchStack *ss = sp->sstack[threadID];
1654 bool isCheck = pos.is_check();
1655 bool useFutilityPruning = UseFutilityPruning
1656 && sp->depth < SelectiveDepth
1659 while ( sp->bestValue < sp->beta
1660 && !thread_should_stop(threadID)
1661 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
1663 assert(move_is_ok(move));
1665 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1666 bool moveIsCapture = pos.move_is_capture(move);
1668 lock_grab(&(sp->lock));
1669 int moveCount = ++sp->moves;
1670 lock_release(&(sp->lock));
1672 ss[sp->ply].currentMove = move;
1674 // Decide the new search depth.
1676 Depth ext = extension(pos, move, false, moveIsCapture, moveIsCheck, false, false, &dangerous);
1677 Depth newDepth = sp->depth - OnePly + ext;
1680 if ( useFutilityPruning
1683 && !move_promotion(move)
1684 && moveCount >= 2 + int(sp->depth)
1685 && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
1688 // Make and search the move.
1690 pos.do_move(move, st, sp->dcCandidates);
1692 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1693 // if the move fails high will be re-searched at full depth.
1695 && moveCount >= LMRNonPVMoves
1697 && !move_promotion(move)
1698 && !move_is_castle(move)
1699 && !move_is_killer(move, ss[sp->ply]))
1701 ss[sp->ply].reduction = OnePly;
1702 value = -search(pos, ss, -(sp->beta-1), newDepth - OnePly, sp->ply+1, true, threadID);
1705 value = sp->beta; // Just to trigger next condition
1707 if (value >= sp->beta) // Go with full depth non-pv search
1709 ss[sp->ply].reduction = Depth(0);
1710 value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true, threadID);
1712 pos.undo_move(move);
1714 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1716 if (thread_should_stop(threadID))
1720 lock_grab(&(sp->lock));
1721 if (value > sp->bestValue && !thread_should_stop(threadID))
1723 sp->bestValue = value;
1724 if (sp->bestValue >= sp->beta)
1726 sp_update_pv(sp->parentSstack, ss, sp->ply);
1727 for (int i = 0; i < ActiveThreads; i++)
1728 if (i != threadID && (i == sp->master || sp->slaves[i]))
1729 Threads[i].stop = true;
1731 sp->finished = true;
1734 lock_release(&(sp->lock));
1737 lock_grab(&(sp->lock));
1739 // If this is the master thread and we have been asked to stop because of
1740 // a beta cutoff higher up in the tree, stop all slave threads:
1741 if (sp->master == threadID && thread_should_stop(threadID))
1742 for (int i = 0; i < ActiveThreads; i++)
1744 Threads[i].stop = true;
1747 sp->slaves[threadID] = 0;
1749 lock_release(&(sp->lock));
1753 // sp_search_pv() is used to search from a PV split point. This function
1754 // is called by each thread working at the split point. It is similar to
1755 // the normal search_pv() function, but simpler. Because we have already
1756 // probed the hash table and searched the first move before splitting, we
1757 // don't have to repeat all this work in sp_search_pv(). We also don't
1758 // need to store anything to the hash table here: This is taken care of
1759 // after we return from the split point.
1761 void sp_search_pv(SplitPoint *sp, int threadID) {
1763 assert(threadID >= 0 && threadID < ActiveThreads);
1764 assert(ActiveThreads > 1);
1766 Position pos = Position(sp->pos);
1767 SearchStack *ss = sp->sstack[threadID];
1771 while ( sp->alpha < sp->beta
1772 && !thread_should_stop(threadID)
1773 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE)
1775 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1776 bool moveIsCapture = pos.move_is_capture(move);
1778 assert(move_is_ok(move));
1780 lock_grab(&(sp->lock));
1781 int moveCount = ++sp->moves;
1782 lock_release(&(sp->lock));
1784 ss[sp->ply].currentMove = move;
1786 // Decide the new search depth.
1788 Depth ext = extension(pos, move, true, moveIsCapture, moveIsCheck, false, false, &dangerous);
1789 Depth newDepth = sp->depth - OnePly + ext;
1791 // Make and search the move.
1793 pos.do_move(move, st, sp->dcCandidates);
1795 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1796 // if the move fails high will be re-searched at full depth.
1798 && moveCount >= LMRPVMoves
1800 && !move_promotion(move)
1801 && !move_is_castle(move)
1802 && !move_is_killer(move, ss[sp->ply]))
1804 ss[sp->ply].reduction = OnePly;
1805 value = -search(pos, ss, -sp->alpha, newDepth - OnePly, sp->ply+1, true, threadID);
1808 value = sp->alpha + 1; // Just to trigger next condition
1810 if (value > sp->alpha) // Go with full depth non-pv search
1812 ss[sp->ply].reduction = Depth(0);
1813 value = -search(pos, ss, -sp->alpha, newDepth, sp->ply+1, true, threadID);
1815 if (value > sp->alpha && value < sp->beta)
1817 // When the search fails high at ply 1 while searching the first
1818 // move at the root, set the flag failHighPly1. This is used for
1819 // time managment: We don't want to stop the search early in
1820 // such cases, because resolving the fail high at ply 1 could
1821 // result in a big drop in score at the root.
1822 if (sp->ply == 1 && RootMoveNumber == 1)
1823 Threads[threadID].failHighPly1 = true;
1825 value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth, sp->ply+1, threadID);
1826 Threads[threadID].failHighPly1 = false;
1829 pos.undo_move(move);
1831 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1833 if (thread_should_stop(threadID))
1837 lock_grab(&(sp->lock));
1838 if (value > sp->bestValue && !thread_should_stop(threadID))
1840 sp->bestValue = value;
1841 if (value > sp->alpha)
1844 sp_update_pv(sp->parentSstack, ss, sp->ply);
1845 if (value == value_mate_in(sp->ply + 1))
1846 ss[sp->ply].mateKiller = move;
1848 if(value >= sp->beta)
1850 for(int i = 0; i < ActiveThreads; i++)
1851 if(i != threadID && (i == sp->master || sp->slaves[i]))
1852 Threads[i].stop = true;
1854 sp->finished = true;
1857 // If we are at ply 1, and we are searching the first root move at
1858 // ply 0, set the 'Problem' variable if the score has dropped a lot
1859 // (from the computer's point of view) since the previous iteration.
1862 && -value <= IterationInfo[Iteration-1].value - ProblemMargin)
1865 lock_release(&(sp->lock));
1868 lock_grab(&(sp->lock));
1870 // If this is the master thread and we have been asked to stop because of
1871 // a beta cutoff higher up in the tree, stop all slave threads.
1872 if (sp->master == threadID && thread_should_stop(threadID))
1873 for (int i = 0; i < ActiveThreads; i++)
1875 Threads[i].stop = true;
1878 sp->slaves[threadID] = 0;
1880 lock_release(&(sp->lock));
1883 /// The BetaCounterType class
1885 BetaCounterType::BetaCounterType() { clear(); }
1887 void BetaCounterType::clear() {
1889 for (int i = 0; i < THREAD_MAX; i++)
1890 Threads[i].betaCutOffs[WHITE] = Threads[i].betaCutOffs[BLACK] = 0ULL;
1893 void BetaCounterType::add(Color us, Depth d, int threadID) {
1895 // Weighted count based on depth
1896 Threads[threadID].betaCutOffs[us] += unsigned(d);
1899 void BetaCounterType::read(Color us, int64_t& our, int64_t& their) {
1902 for (int i = 0; i < THREAD_MAX; i++)
1904 our += Threads[i].betaCutOffs[us];
1905 their += Threads[i].betaCutOffs[opposite_color(us)];
1910 /// The RootMove class
1914 RootMove::RootMove() {
1915 nodes = cumulativeNodes = ourBeta = theirBeta = 0ULL;
1918 // RootMove::operator<() is the comparison function used when
1919 // sorting the moves. A move m1 is considered to be better
1920 // than a move m2 if it has a higher score, or if the moves
1921 // have equal score but m1 has the higher node count.
1923 bool RootMove::operator<(const RootMove& m) {
1925 if (score != m.score)
1926 return (score < m.score);
1928 return theirBeta <= m.theirBeta;
1931 /// The RootMoveList class
1935 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
1937 MoveStack mlist[MaxRootMoves];
1938 bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
1940 // Generate all legal moves
1941 int lm_count = generate_legal_moves(pos, mlist);
1943 // Add each move to the moves[] array
1944 for (int i = 0; i < lm_count; i++)
1946 bool includeMove = includeAllMoves;
1948 for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
1949 includeMove = (searchMoves[k] == mlist[i].move);
1954 // Find a quick score for the move
1956 SearchStack ss[PLY_MAX_PLUS_2];
1958 moves[count].move = mlist[i].move;
1959 pos.do_move(moves[count].move, st);
1960 moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE, Depth(0), 1, 0);
1961 pos.undo_move(moves[count].move);
1962 moves[count].pv[0] = moves[count].move;
1963 moves[count].pv[1] = MOVE_NONE; // FIXME
1970 // Simple accessor methods for the RootMoveList class
1972 inline Move RootMoveList::get_move(int moveNum) const {
1973 return moves[moveNum].move;
1976 inline Value RootMoveList::get_move_score(int moveNum) const {
1977 return moves[moveNum].score;
1980 inline void RootMoveList::set_move_score(int moveNum, Value score) {
1981 moves[moveNum].score = score;
1984 inline void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
1985 moves[moveNum].nodes = nodes;
1986 moves[moveNum].cumulativeNodes += nodes;
1989 inline void RootMoveList::set_beta_counters(int moveNum, int64_t our, int64_t their) {
1990 moves[moveNum].ourBeta = our;
1991 moves[moveNum].theirBeta = their;
1994 void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
1996 for(j = 0; pv[j] != MOVE_NONE; j++)
1997 moves[moveNum].pv[j] = pv[j];
1998 moves[moveNum].pv[j] = MOVE_NONE;
2001 inline Move RootMoveList::get_move_pv(int moveNum, int i) const {
2002 return moves[moveNum].pv[i];
2005 inline int64_t RootMoveList::get_move_cumulative_nodes(int moveNum) const {
2006 return moves[moveNum].cumulativeNodes;
2009 inline int RootMoveList::move_count() const {
2014 // RootMoveList::scan_for_easy_move() is called at the end of the first
2015 // iteration, and is used to detect an "easy move", i.e. a move which appears
2016 // to be much bester than all the rest. If an easy move is found, the move
2017 // is returned, otherwise the function returns MOVE_NONE. It is very
2018 // important that this function is called at the right moment: The code
2019 // assumes that the first iteration has been completed and the moves have
2020 // been sorted. This is done in RootMoveList c'tor.
2022 Move RootMoveList::scan_for_easy_move() const {
2029 // moves are sorted so just consider the best and the second one
2030 if (get_move_score(0) > get_move_score(1) + EasyMoveMargin)
2036 // RootMoveList::sort() sorts the root move list at the beginning of a new
2039 inline void RootMoveList::sort() {
2041 sort_multipv(count - 1); // all items
2045 // RootMoveList::sort_multipv() sorts the first few moves in the root move
2046 // list by their scores and depths. It is used to order the different PVs
2047 // correctly in MultiPV mode.
2049 void RootMoveList::sort_multipv(int n) {
2051 for (int i = 1; i <= n; i++)
2053 RootMove rm = moves[i];
2055 for (j = i; j > 0 && moves[j-1] < rm; j--)
2056 moves[j] = moves[j-1];
2062 // init_node() is called at the beginning of all the search functions
2063 // (search(), search_pv(), qsearch(), and so on) and initializes the search
2064 // stack object corresponding to the current node. Once every
2065 // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
2066 // for user input and checks whether it is time to stop the search.
2068 void init_node(SearchStack ss[], int ply, int threadID) {
2069 assert(ply >= 0 && ply < PLY_MAX);
2070 assert(threadID >= 0 && threadID < ActiveThreads);
2072 Threads[threadID].nodes++;
2076 if(NodesSincePoll >= NodesBetweenPolls) {
2083 ss[ply+2].initKillers();
2085 if(Threads[threadID].printCurrentLine)
2086 print_current_line(ss, ply, threadID);
2090 // update_pv() is called whenever a search returns a value > alpha. It
2091 // updates the PV in the SearchStack object corresponding to the current
2094 void update_pv(SearchStack ss[], int ply) {
2095 assert(ply >= 0 && ply < PLY_MAX);
2097 ss[ply].pv[ply] = ss[ply].currentMove;
2099 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
2100 ss[ply].pv[p] = ss[ply+1].pv[p];
2101 ss[ply].pv[p] = MOVE_NONE;
2105 // sp_update_pv() is a variant of update_pv for use at split points. The
2106 // difference between the two functions is that sp_update_pv also updates
2107 // the PV at the parent node.
2109 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply) {
2110 assert(ply >= 0 && ply < PLY_MAX);
2112 ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
2114 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
2115 ss[ply].pv[p] = pss[ply].pv[p] = ss[ply+1].pv[p];
2116 ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE;
2120 // connected_moves() tests whether two moves are 'connected' in the sense
2121 // that the first move somehow made the second move possible (for instance
2122 // if the moving piece is the same in both moves). The first move is
2123 // assumed to be the move that was made to reach the current position, while
2124 // the second move is assumed to be a move from the current position.
2126 bool connected_moves(const Position &pos, Move m1, Move m2) {
2127 Square f1, t1, f2, t2;
2129 assert(move_is_ok(m1));
2130 assert(move_is_ok(m2));
2135 // Case 1: The moving piece is the same in both moves.
2141 // Case 2: The destination square for m2 was vacated by m1.
2147 // Case 3: Moving through the vacated square:
2148 if(piece_is_slider(pos.piece_on(f2)) &&
2149 bit_is_set(squares_between(f2, t2), f1))
2152 // Case 4: The destination square for m2 is attacked by the moving piece
2154 if(pos.piece_attacks_square(pos.piece_on(t1), t1, t2))
2157 // Case 5: Discovered check, checking piece is the piece moved in m1:
2158 if(piece_is_slider(pos.piece_on(t1)) &&
2159 bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())),
2161 !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())),
2163 Bitboard occ = pos.occupied_squares();
2164 Color us = pos.side_to_move();
2165 Square ksq = pos.king_square(us);
2166 clear_bit(&occ, f2);
2167 if(pos.type_of_piece_on(t1) == BISHOP) {
2168 if(bit_is_set(bishop_attacks_bb(ksq, occ), t1))
2171 else if(pos.type_of_piece_on(t1) == ROOK) {
2172 if(bit_is_set(rook_attacks_bb(ksq, occ), t1))
2176 assert(pos.type_of_piece_on(t1) == QUEEN);
2177 if(bit_is_set(queen_attacks_bb(ksq, occ), t1))
2186 // value_is_mate() checks if the given value is a mate one
2187 // eventually compensated for the ply.
2189 bool value_is_mate(Value value) {
2191 assert(abs(value) <= VALUE_INFINITE);
2193 return value <= value_mated_in(PLY_MAX)
2194 || value >= value_mate_in(PLY_MAX);
2198 // move_is_killer() checks if the given move is among the
2199 // killer moves of that ply.
2201 bool move_is_killer(Move m, const SearchStack& ss) {
2203 const Move* k = ss.killers;
2204 for (int i = 0; i < KILLER_MAX; i++, k++)
2212 // extension() decides whether a move should be searched with normal depth,
2213 // or with extended depth. Certain classes of moves (checking moves, in
2214 // particular) are searched with bigger depth than ordinary moves and in
2215 // any case are marked as 'dangerous'. Note that also if a move is not
2216 // extended, as example because the corresponding UCI option is set to zero,
2217 // the move is marked as 'dangerous' so, at least, we avoid to prune it.
2219 Depth extension(const Position& pos, Move m, bool pvNode, bool capture, bool check,
2220 bool singleReply, bool mateThreat, bool* dangerous) {
2222 assert(m != MOVE_NONE);
2224 Depth result = Depth(0);
2225 *dangerous = check || singleReply || mateThreat;
2228 result += CheckExtension[pvNode];
2231 result += SingleReplyExtension[pvNode];
2234 result += MateThreatExtension[pvNode];
2236 if (pos.type_of_piece_on(move_from(m)) == PAWN)
2238 if (pos.move_is_pawn_push_to_7th(m))
2240 result += PawnPushTo7thExtension[pvNode];
2243 if (pos.move_is_passed_pawn_push(m))
2245 result += PassedPawnExtension[pvNode];
2251 && pos.type_of_piece_on(move_to(m)) != PAWN
2252 && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
2253 - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
2254 && !move_promotion(m)
2257 result += PawnEndgameExtension[pvNode];
2263 && pos.type_of_piece_on(move_to(m)) != PAWN
2270 return Min(result, OnePly);
2274 // ok_to_do_nullmove() looks at the current position and decides whether
2275 // doing a 'null move' should be allowed. In order to avoid zugzwang
2276 // problems, null moves are not allowed when the side to move has very
2277 // little material left. Currently, the test is a bit too simple: Null
2278 // moves are avoided only when the side to move has only pawns left. It's
2279 // probably a good idea to avoid null moves in at least some more
2280 // complicated endgames, e.g. KQ vs KR. FIXME
2282 bool ok_to_do_nullmove(const Position &pos) {
2283 if(pos.non_pawn_material(pos.side_to_move()) == Value(0))
2289 // ok_to_prune() tests whether it is safe to forward prune a move. Only
2290 // non-tactical moves late in the move list close to the leaves are
2291 // candidates for pruning.
2293 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d) {
2294 Square mfrom, mto, tfrom, tto;
2296 assert(move_is_ok(m));
2297 assert(threat == MOVE_NONE || move_is_ok(threat));
2298 assert(!move_promotion(m));
2299 assert(!pos.move_is_check(m));
2300 assert(!pos.move_is_capture(m));
2301 assert(!pos.move_is_passed_pawn_push(m));
2302 assert(d >= OnePly);
2304 mfrom = move_from(m);
2306 tfrom = move_from(threat);
2307 tto = move_to(threat);
2309 // Case 1: Castling moves are never pruned.
2310 if (move_is_castle(m))
2313 // Case 2: Don't prune moves which move the threatened piece
2314 if (!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto)
2317 // Case 3: If the threatened piece has value less than or equal to the
2318 // value of the threatening piece, don't prune move which defend it.
2319 if ( !PruneDefendingMoves
2320 && threat != MOVE_NONE
2321 && pos.move_is_capture(threat)
2322 && ( pos.midgame_value_of_piece_on(tfrom) >= pos.midgame_value_of_piece_on(tto)
2323 || pos.type_of_piece_on(tfrom) == KING)
2324 && pos.move_attacks_square(m, tto))
2327 // Case 4: Don't prune moves with good history.
2328 if (!H.ok_to_prune(pos.piece_on(mfrom), mto, d))
2331 // Case 5: If the moving piece in the threatened move is a slider, don't
2332 // prune safe moves which block its ray.
2333 if ( !PruneBlockingMoves
2334 && threat != MOVE_NONE
2335 && piece_is_slider(pos.piece_on(tfrom))
2336 && bit_is_set(squares_between(tfrom, tto), mto)
2344 // ok_to_use_TT() returns true if a transposition table score
2345 // can be used at a given point in search.
2347 bool ok_to_use_TT(const TTEntry* tte, Depth depth, Value beta, int ply) {
2349 Value v = value_from_tt(tte->value(), ply);
2351 return ( tte->depth() >= depth
2352 || v >= Max(value_mate_in(100), beta)
2353 || v < Min(value_mated_in(100), beta))
2355 && ( (is_lower_bound(tte->type()) && v >= beta)
2356 || (is_upper_bound(tte->type()) && v < beta));
2360 // ok_to_history() returns true if a move m can be stored
2361 // in history. Should be a non capturing move nor a promotion.
2363 bool ok_to_history(const Position& pos, Move m) {
2365 return !pos.move_is_capture(m) && !move_promotion(m);
2369 // update_history() registers a good move that produced a beta-cutoff
2370 // in history and marks as failures all the other moves of that ply.
2372 void update_history(const Position& pos, Move m, Depth depth,
2373 Move movesSearched[], int moveCount) {
2375 H.success(pos.piece_on(move_from(m)), move_to(m), depth);
2377 for (int i = 0; i < moveCount - 1; i++)
2379 assert(m != movesSearched[i]);
2380 if (ok_to_history(pos, movesSearched[i]))
2381 H.failure(pos.piece_on(move_from(movesSearched[i])), move_to(movesSearched[i]));
2386 // update_killers() add a good move that produced a beta-cutoff
2387 // among the killer moves of that ply.
2389 void update_killers(Move m, SearchStack& ss) {
2391 if (m == ss.killers[0])
2394 for (int i = KILLER_MAX - 1; i > 0; i--)
2395 ss.killers[i] = ss.killers[i - 1];
2400 // fail_high_ply_1() checks if some thread is currently resolving a fail
2401 // high at ply 1 at the node below the first root node. This information
2402 // is used for time managment.
2404 bool fail_high_ply_1() {
2405 for(int i = 0; i < ActiveThreads; i++)
2406 if(Threads[i].failHighPly1)
2412 // current_search_time() returns the number of milliseconds which have passed
2413 // since the beginning of the current search.
2415 int current_search_time() {
2416 return get_system_time() - SearchStartTime;
2420 // nps() computes the current nodes/second count.
2423 int t = current_search_time();
2424 return (t > 0)? int((nodes_searched() * 1000) / t) : 0;
2428 // poll() performs two different functions: It polls for user input, and it
2429 // looks at the time consumed so far and decides if it's time to abort the
2434 static int lastInfoTime;
2435 int t = current_search_time();
2440 // We are line oriented, don't read single chars
2441 std::string command;
2442 if (!std::getline(std::cin, command))
2445 if (command == "quit")
2448 PonderSearch = false;
2452 else if(command == "stop")
2455 PonderSearch = false;
2457 else if(command == "ponderhit")
2460 // Print search information
2464 else if (lastInfoTime > t)
2465 // HACK: Must be a new search where we searched less than
2466 // NodesBetweenPolls nodes during the first second of search.
2469 else if (t - lastInfoTime >= 1000)
2476 if (dbg_show_hit_rate)
2477 dbg_print_hit_rate();
2479 std::cout << "info nodes " << nodes_searched() << " nps " << nps()
2480 << " time " << t << " hashfull " << TT.full() << std::endl;
2481 lock_release(&IOLock);
2482 if (ShowCurrentLine)
2483 Threads[0].printCurrentLine = true;
2485 // Should we stop the search?
2489 bool overTime = t > AbsoluteMaxSearchTime
2490 || (RootMoveNumber == 1 && t > MaxSearchTime + ExtraSearchTime && !FailLow) //FIXME: We are not checking any problem flags, BUG?
2491 || ( !FailHigh && !FailLow && !fail_high_ply_1() && !Problem
2492 && t > 6*(MaxSearchTime + ExtraSearchTime));
2494 if ( (Iteration >= 3 && (!InfiniteSearch && overTime))
2495 || (ExactMaxTime && t >= ExactMaxTime)
2496 || (Iteration >= 3 && MaxNodes && nodes_searched() >= MaxNodes))
2501 // ponderhit() is called when the program is pondering (i.e. thinking while
2502 // it's the opponent's turn to move) in order to let the engine know that
2503 // it correctly predicted the opponent's move.
2506 int t = current_search_time();
2507 PonderSearch = false;
2508 if(Iteration >= 3 &&
2509 (!InfiniteSearch && (StopOnPonderhit ||
2510 t > AbsoluteMaxSearchTime ||
2511 (RootMoveNumber == 1 &&
2512 t > MaxSearchTime + ExtraSearchTime && !FailLow) ||
2513 (!FailHigh && !FailLow && !fail_high_ply_1() && !Problem &&
2514 t > 6*(MaxSearchTime + ExtraSearchTime)))))
2519 // print_current_line() prints the current line of search for a given
2520 // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
2522 void print_current_line(SearchStack ss[], int ply, int threadID) {
2523 assert(ply >= 0 && ply < PLY_MAX);
2524 assert(threadID >= 0 && threadID < ActiveThreads);
2526 if(!Threads[threadID].idle) {
2528 std::cout << "info currline " << (threadID + 1);
2529 for(int p = 0; p < ply; p++)
2530 std::cout << " " << ss[p].currentMove;
2531 std::cout << std::endl;
2532 lock_release(&IOLock);
2534 Threads[threadID].printCurrentLine = false;
2535 if(threadID + 1 < ActiveThreads)
2536 Threads[threadID + 1].printCurrentLine = true;
2540 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2541 // while the program is pondering. The point is to work around a wrinkle in
2542 // the UCI protocol: When pondering, the engine is not allowed to give a
2543 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2544 // We simply wait here until one of these commands is sent, and return,
2545 // after which the bestmove and pondermove will be printed (in id_loop()).
2547 void wait_for_stop_or_ponderhit() {
2549 std::string command;
2553 if (!std::getline(std::cin, command))
2556 if (command == "quit")
2561 else if(command == "ponderhit" || command == "stop")
2567 // idle_loop() is where the threads are parked when they have no work to do.
2568 // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
2569 // object for which the current thread is the master.
2571 void idle_loop(int threadID, SplitPoint *waitSp) {
2572 assert(threadID >= 0 && threadID < THREAD_MAX);
2574 Threads[threadID].running = true;
2577 if(AllThreadsShouldExit && threadID != 0)
2580 // If we are not thinking, wait for a condition to be signaled instead
2581 // of wasting CPU time polling for work:
2582 while(threadID != 0 && (Idle || threadID >= ActiveThreads)) {
2583 #if !defined(_MSC_VER)
2584 pthread_mutex_lock(&WaitLock);
2585 if(Idle || threadID >= ActiveThreads)
2586 pthread_cond_wait(&WaitCond, &WaitLock);
2587 pthread_mutex_unlock(&WaitLock);
2589 WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
2593 // If this thread has been assigned work, launch a search:
2594 if(Threads[threadID].workIsWaiting) {
2595 Threads[threadID].workIsWaiting = false;
2596 if(Threads[threadID].splitPoint->pvNode)
2597 sp_search_pv(Threads[threadID].splitPoint, threadID);
2599 sp_search(Threads[threadID].splitPoint, threadID);
2600 Threads[threadID].idle = true;
2603 // If this thread is the master of a split point and all threads have
2604 // finished their work at this split point, return from the idle loop:
2605 if(waitSp != NULL && waitSp->cpus == 0)
2609 Threads[threadID].running = false;
2613 // init_split_point_stack() is called during program initialization, and
2614 // initializes all split point objects.
2616 void init_split_point_stack() {
2617 for(int i = 0; i < THREAD_MAX; i++)
2618 for(int j = 0; j < MaxActiveSplitPoints; j++) {
2619 SplitPointStack[i][j].parent = NULL;
2620 lock_init(&(SplitPointStack[i][j].lock), NULL);
2625 // destroy_split_point_stack() is called when the program exits, and
2626 // destroys all locks in the precomputed split point objects.
2628 void destroy_split_point_stack() {
2629 for(int i = 0; i < THREAD_MAX; i++)
2630 for(int j = 0; j < MaxActiveSplitPoints; j++)
2631 lock_destroy(&(SplitPointStack[i][j].lock));
2635 // thread_should_stop() checks whether the thread with a given threadID has
2636 // been asked to stop, directly or indirectly. This can happen if a beta
2637 // cutoff has occured in thre thread's currently active split point, or in
2638 // some ancestor of the current split point.
2640 bool thread_should_stop(int threadID) {
2641 assert(threadID >= 0 && threadID < ActiveThreads);
2645 if(Threads[threadID].stop)
2647 if(ActiveThreads <= 2)
2649 for(sp = Threads[threadID].splitPoint; sp != NULL; sp = sp->parent)
2651 Threads[threadID].stop = true;
2658 // thread_is_available() checks whether the thread with threadID "slave" is
2659 // available to help the thread with threadID "master" at a split point. An
2660 // obvious requirement is that "slave" must be idle. With more than two
2661 // threads, this is not by itself sufficient: If "slave" is the master of
2662 // some active split point, it is only available as a slave to the other
2663 // threads which are busy searching the split point at the top of "slave"'s
2664 // split point stack (the "helpful master concept" in YBWC terminology).
2666 bool thread_is_available(int slave, int master) {
2667 assert(slave >= 0 && slave < ActiveThreads);
2668 assert(master >= 0 && master < ActiveThreads);
2669 assert(ActiveThreads > 1);
2671 if(!Threads[slave].idle || slave == master)
2674 if(Threads[slave].activeSplitPoints == 0)
2675 // No active split points means that the thread is available as a slave
2676 // for any other thread.
2679 if(ActiveThreads == 2)
2682 // Apply the "helpful master" concept if possible.
2683 if(SplitPointStack[slave][Threads[slave].activeSplitPoints-1].slaves[master])
2690 // idle_thread_exists() tries to find an idle thread which is available as
2691 // a slave for the thread with threadID "master".
2693 bool idle_thread_exists(int master) {
2694 assert(master >= 0 && master < ActiveThreads);
2695 assert(ActiveThreads > 1);
2697 for(int i = 0; i < ActiveThreads; i++)
2698 if(thread_is_available(i, master))
2704 // split() does the actual work of distributing the work at a node between
2705 // several threads at PV nodes. If it does not succeed in splitting the
2706 // node (because no idle threads are available, or because we have no unused
2707 // split point objects), the function immediately returns false. If
2708 // splitting is possible, a SplitPoint object is initialized with all the
2709 // data that must be copied to the helper threads (the current position and
2710 // search stack, alpha, beta, the search depth, etc.), and we tell our
2711 // helper threads that they have been assigned work. This will cause them
2712 // to instantly leave their idle loops and call sp_search_pv(). When all
2713 // threads have returned from sp_search_pv (or, equivalently, when
2714 // splitPoint->cpus becomes 0), split() returns true.
2716 bool split(const Position &p, SearchStack *sstck, int ply,
2717 Value *alpha, Value *beta, Value *bestValue, Depth depth, int *moves,
2718 MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) {
2721 assert(sstck != NULL);
2722 assert(ply >= 0 && ply < PLY_MAX);
2723 assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha);
2724 assert(!pvNode || *alpha < *beta);
2725 assert(*beta <= VALUE_INFINITE);
2726 assert(depth > Depth(0));
2727 assert(master >= 0 && master < ActiveThreads);
2728 assert(ActiveThreads > 1);
2730 SplitPoint *splitPoint;
2735 // If no other thread is available to help us, or if we have too many
2736 // active split points, don't split:
2737 if(!idle_thread_exists(master) ||
2738 Threads[master].activeSplitPoints >= MaxActiveSplitPoints) {
2739 lock_release(&MPLock);
2743 // Pick the next available split point object from the split point stack:
2744 splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
2745 Threads[master].activeSplitPoints++;
2747 // Initialize the split point object:
2748 splitPoint->parent = Threads[master].splitPoint;
2749 splitPoint->finished = false;
2750 splitPoint->ply = ply;
2751 splitPoint->depth = depth;
2752 splitPoint->alpha = pvNode? *alpha : (*beta - 1);
2753 splitPoint->beta = *beta;
2754 splitPoint->pvNode = pvNode;
2755 splitPoint->dcCandidates = dcCandidates;
2756 splitPoint->bestValue = *bestValue;
2757 splitPoint->master = master;
2758 splitPoint->mp = mp;
2759 splitPoint->moves = *moves;
2760 splitPoint->cpus = 1;
2761 splitPoint->pos.copy(p);
2762 splitPoint->parentSstack = sstck;
2763 for(i = 0; i < ActiveThreads; i++)
2764 splitPoint->slaves[i] = 0;
2766 // Copy the current position and the search stack to the master thread:
2767 memcpy(splitPoint->sstack[master], sstck, (ply+1)*sizeof(SearchStack));
2768 Threads[master].splitPoint = splitPoint;
2770 // Make copies of the current position and search stack for each thread:
2771 for(i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint;
2773 if(thread_is_available(i, master)) {
2774 memcpy(splitPoint->sstack[i], sstck, (ply+1)*sizeof(SearchStack));
2775 Threads[i].splitPoint = splitPoint;
2776 splitPoint->slaves[i] = 1;
2780 // Tell the threads that they have work to do. This will make them leave
2782 for(i = 0; i < ActiveThreads; i++)
2783 if(i == master || splitPoint->slaves[i]) {
2784 Threads[i].workIsWaiting = true;
2785 Threads[i].idle = false;
2786 Threads[i].stop = false;
2789 lock_release(&MPLock);
2791 // Everything is set up. The master thread enters the idle loop, from
2792 // which it will instantly launch a search, because its workIsWaiting
2793 // slot is 'true'. We send the split point as a second parameter to the
2794 // idle loop, which means that the main thread will return from the idle
2795 // loop when all threads have finished their work at this split point
2796 // (i.e. when // splitPoint->cpus == 0).
2797 idle_loop(master, splitPoint);
2799 // We have returned from the idle loop, which means that all threads are
2800 // finished. Update alpha, beta and bestvalue, and return:
2802 if(pvNode) *alpha = splitPoint->alpha;
2803 *beta = splitPoint->beta;
2804 *bestValue = splitPoint->bestValue;
2805 Threads[master].stop = false;
2806 Threads[master].idle = false;
2807 Threads[master].activeSplitPoints--;
2808 Threads[master].splitPoint = splitPoint->parent;
2809 lock_release(&MPLock);
2815 // wake_sleeping_threads() wakes up all sleeping threads when it is time
2816 // to start a new search from the root.
2818 void wake_sleeping_threads() {
2819 if(ActiveThreads > 1) {
2820 for(int i = 1; i < ActiveThreads; i++) {
2821 Threads[i].idle = true;
2822 Threads[i].workIsWaiting = false;
2824 #if !defined(_MSC_VER)
2825 pthread_mutex_lock(&WaitLock);
2826 pthread_cond_broadcast(&WaitCond);
2827 pthread_mutex_unlock(&WaitLock);
2829 for(int i = 1; i < THREAD_MAX; i++)
2830 SetEvent(SitIdleEvent[i]);
2836 // init_thread() is the function which is called when a new thread is
2837 // launched. It simply calls the idle_loop() function with the supplied
2838 // threadID. There are two versions of this function; one for POSIX threads
2839 // and one for Windows threads.
2841 #if !defined(_MSC_VER)
2843 void *init_thread(void *threadID) {
2844 idle_loop(*(int *)threadID, NULL);
2850 DWORD WINAPI init_thread(LPVOID threadID) {
2851 idle_loop(*(int *)threadID, NULL);