2 Glaurung, a UCI chess playing engine.
3 Copyright (C) 2004-2008 Tord Romstad
5 Glaurung is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation, either version 3 of the License, or
8 (at your option) any later version.
10 Glaurung is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
39 #include "ucioption.h"
43 //// Local definitions
50 // The RootMove class is used for moves at the root at the tree. For each
51 // root move, we store a score, a node count, and a PV (really a refutation
52 // in the case of moves which fail low).
60 int64_t nodes, cumulativeNodes;
61 Move pv[PLY_MAX_PLUS_2];
65 // The RootMoveList class is essentially an array of RootMove objects, with
66 // a handful of methods for accessing the data in the individual moves.
71 RootMoveList(Position &pos, Move searchMoves[]);
72 Move get_move(int moveNum) const;
73 Value get_move_score(int moveNum) const;
74 void set_move_score(int moveNum, Value score);
75 void set_move_nodes(int moveNum, int64_t nodes);
76 void set_move_pv(int moveNum, const Move pv[]);
77 Move get_move_pv(int moveNum, int i) const;
78 int64_t get_move_cumulative_nodes(int moveNum);
79 int move_count() const;
80 Move scan_for_easy_move() const;
82 void sort_multipv(int n);
85 static bool compare_root_moves(const RootMove &rm1, const RootMove &rm2);
86 static const int MaxRootMoves = 500;
87 RootMove moves[MaxRootMoves];
92 /// Constants and variables
94 // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
97 int LMRNonPVMoves = 4;
99 // Depth limit for use of dynamic threat detection:
100 Depth ThreatDepth = 5*OnePly;
102 // Depth limit for selective search:
103 Depth SelectiveDepth = 7*OnePly;
105 // Use internal iterative deepening?
106 const bool UseIIDAtPVNodes = true;
107 const bool UseIIDAtNonPVNodes = false;
109 // Internal iterative deepening margin. At Non-PV moves, when
110 // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
111 // when the static evaluation is at most IIDMargin below beta.
112 const Value IIDMargin = Value(0x100);
115 const bool UseEasyMove = true;
117 // Easy move margin. An easy move candidate must be at least this much
118 // better than the second best move.
119 const Value EasyMoveMargin = Value(0x200);
121 // Problem margin. If the score of the first move at iteration N+1 has
122 // dropped by more than this since iteration N, the boolean variable
123 // "Problem" is set to true, which will make the program spend some extra
124 // time looking for a better move.
125 const Value ProblemMargin = Value(0x28);
127 // No problem margin. If the boolean "Problem" is true, and a new move
128 // is found at the root which is less than NoProblemMargin worse than the
129 // best move from the previous iteration, Problem is set back to false.
130 const Value NoProblemMargin = Value(0x14);
132 // Null move margin. A null move search will not be done if the approximate
133 // evaluation of the position is more than NullMoveMargin below beta.
134 const Value NullMoveMargin = Value(0x300);
136 // Pruning criterions. See the code and comments in ok_to_prune() to
137 // understand their precise meaning.
138 const bool PruneEscapeMoves = false;
139 const bool PruneDefendingMoves = false;
140 const bool PruneBlockingMoves = false;
142 // Use futility pruning?
143 bool UseQSearchFutilityPruning = true;
144 bool UseFutilityPruning = true;
146 // Margins for futility pruning in the quiescence search, at frontier
147 // nodes, and at pre-frontier nodes:
148 Value FutilityMargin0 = Value(0x80);
149 Value FutilityMargin1 = Value(0x100);
150 Value FutilityMargin2 = Value(0x300);
153 Depth RazorDepth = 4*OnePly;
154 Value RazorMargin = Value(0x300);
156 // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
157 Depth CheckExtension[2] = {OnePly, OnePly};
158 Depth SingleReplyExtension[2] = {OnePly / 2, OnePly / 2};
159 Depth PawnPushTo7thExtension[2] = {OnePly / 2, OnePly / 2};
160 Depth PassedPawnExtension[2] = {Depth(0), Depth(0)};
161 Depth PawnEndgameExtension[2] = {OnePly, OnePly};
162 Depth MateThreatExtension[2] = {Depth(0), Depth(0)};
164 // Search depth at iteration 1:
165 const Depth InitialDepth = OnePly /*+ OnePly/2*/;
169 int NodesBetweenPolls = 30000;
171 // Iteration counter:
174 // Scores and number of times the best move changed for each iteration:
175 Value ValueByIteration[PLY_MAX_PLUS_2];
176 int BestMoveChangesByIteration[PLY_MAX_PLUS_2];
181 // Time managment variables
183 int MaxNodes, MaxDepth;
184 int MaxSearchTime, AbsoluteMaxSearchTime, ExtraSearchTime;
185 Move BestRootMove, PonderMove, EasyMove;
189 bool StopOnPonderhit;
194 bool PonderingEnabled;
197 // Show current line?
198 bool ShowCurrentLine = false;
201 bool UseLogFile = false;
202 std::ofstream LogFile;
204 // MP related variables
205 Depth MinimumSplitDepth = 4*OnePly;
206 int MaxThreadsPerSplitPoint = 4;
207 Thread Threads[THREAD_MAX];
209 bool AllThreadsShouldExit = false;
210 const int MaxActiveSplitPoints = 8;
211 SplitPoint SplitPointStack[THREAD_MAX][MaxActiveSplitPoints];
214 #if !defined(_MSC_VER)
215 pthread_cond_t WaitCond;
216 pthread_mutex_t WaitLock;
218 HANDLE SitIdleEvent[THREAD_MAX];
224 void id_loop(const Position &pos, Move searchMoves[]);
225 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml);
226 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
227 Depth depth, int ply, int threadID);
228 Value search(Position &pos, SearchStack ss[], Value beta,
229 Depth depth, int ply, bool allowNullmove, int threadID);
230 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
231 Depth depth, int ply, int threadID);
232 void sp_search(SplitPoint *sp, int threadID);
233 void sp_search_pv(SplitPoint *sp, int threadID);
234 void init_search_stack(SearchStack ss[]);
235 void init_node(const Position &pos, SearchStack ss[], int ply, int threadID);
236 void update_pv(SearchStack ss[], int ply);
237 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply);
238 bool connected_moves(const Position &pos, Move m1, Move m2);
239 Depth extension(const Position &pos, Move m, bool pvNode, bool check,
240 bool singleReply, bool mateThreat);
241 bool ok_to_do_nullmove(const Position &pos);
242 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d);
244 bool fail_high_ply_1();
245 int current_search_time();
249 void print_current_line(SearchStack ss[], int ply, int threadID);
250 void wait_for_stop_or_ponderhit();
252 void idle_loop(int threadID, SplitPoint *waitSp);
253 void init_split_point_stack();
254 void destroy_split_point_stack();
255 bool thread_should_stop(int threadID);
256 bool thread_is_available(int slave, int master);
257 bool idle_thread_exists(int master);
258 bool split(const Position &pos, SearchStack *ss, int ply,
259 Value *alpha, Value *beta, Value *bestValue, Depth depth,
260 int *moves, MovePicker *mp, Bitboard dcCandidates, int master,
262 void wake_sleeping_threads();
264 #if !defined(_MSC_VER)
265 void *init_thread(void *threadID);
267 DWORD WINAPI init_thread(LPVOID threadID);
274 //// Global variables
277 // The main transposition table
278 TranspositionTable TT = TranspositionTable(TTDefaultSize);
281 // Number of active threads:
282 int ActiveThreads = 1;
284 // Locks. In principle, there is no need for IOLock to be a global variable,
285 // but it could turn out to be useful for debugging.
288 History H; // Should be made local?
295 /// think() is the external interface to Glaurung's search, and is called when
296 /// the program receives the UCI 'go' command. It initializes various
297 /// search-related global variables, and calls root_search()
299 void think(const Position &pos, bool infinite, bool ponder, int time,
300 int increment, int movesToGo, int maxDepth, int maxNodes,
301 int maxTime, Move searchMoves[]) {
303 // Look for a book move:
304 if(!infinite && !ponder && get_option_value_bool("OwnBook")) {
306 if(get_option_value_string("Book File") != OpeningBook.file_name()) {
308 OpeningBook.open("book.bin");
310 bookMove = OpeningBook.get_move(pos);
311 if(bookMove != MOVE_NONE) {
312 std::cout << "bestmove " << bookMove << std::endl;
317 // Initialize global search variables:
319 SearchStartTime = get_system_time();
320 BestRootMove = MOVE_NONE;
321 PonderMove = MOVE_NONE;
322 EasyMove = MOVE_NONE;
323 for(int i = 0; i < THREAD_MAX; i++) {
324 Threads[i].nodes = 0ULL;
325 Threads[i].failHighPly1 = false;
328 InfiniteSearch = infinite;
329 PonderSearch = ponder;
330 StopOnPonderhit = false;
335 ExactMaxTime = maxTime;
337 // Read UCI option values:
338 TT.set_size(get_option_value_int("Hash"));
339 if(button_was_pressed("Clear Hash"))
341 PonderingEnabled = get_option_value_int("Ponder");
342 MultiPV = get_option_value_int("MultiPV");
344 CheckExtension[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
346 Depth(get_option_value_int("Check Extension (non-PV nodes)"));
347 SingleReplyExtension[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)"));
348 SingleReplyExtension[0] =
349 Depth(get_option_value_int("Single Reply Extension (non-PV nodes)"));
350 PawnPushTo7thExtension[1] =
351 Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
352 PawnPushTo7thExtension[0] =
353 Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
354 PassedPawnExtension[1] =
355 Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
356 PassedPawnExtension[0] =
357 Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
358 PawnEndgameExtension[1] =
359 Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
360 PawnEndgameExtension[0] =
361 Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
362 MateThreatExtension[1] =
363 Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
364 MateThreatExtension[0] =
365 Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
367 LMRPVMoves = get_option_value_int("Full Depth Moves (PV nodes)") + 1;
368 LMRNonPVMoves = get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
369 ThreatDepth = get_option_value_int("Threat Depth") * OnePly;
370 SelectiveDepth = get_option_value_int("Selective Plies") * OnePly;
372 Chess960 = get_option_value_bool("UCI_Chess960");
373 ShowCurrentLine = get_option_value_bool("UCI_ShowCurrLine");
374 UseLogFile = get_option_value_bool("Use Search Log");
376 LogFile.open(get_option_value_string("Search Log Filename").c_str(),
377 std::ios::out | std::ios::app);
379 UseQSearchFutilityPruning =
380 get_option_value_bool("Futility Pruning (Quiescence Search)");
382 get_option_value_bool("Futility Pruning (Main Search)");
385 value_from_centipawns(get_option_value_int("Futility Margin 0"));
387 value_from_centipawns(get_option_value_int("Futility Margin 1"));
389 value_from_centipawns(get_option_value_int("Futility Margin 2"));
391 RazorDepth = (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly;
392 RazorMargin = value_from_centipawns(get_option_value_int("Razoring Margin"));
394 MinimumSplitDepth = get_option_value_int("Minimum Split Depth") * OnePly;
395 MaxThreadsPerSplitPoint =
396 get_option_value_int("Maximum Number of Threads per Split Point");
398 read_weights(pos.side_to_move());
400 int newActiveThreads = get_option_value_int("Threads");
401 if(newActiveThreads != ActiveThreads) {
402 ActiveThreads = newActiveThreads;
403 init_eval(ActiveThreads);
406 // Write information to search log file:
408 LogFile << "Searching: " << pos.to_fen() << '\n';
409 LogFile << "infinite: " << infinite << " ponder: " << ponder
410 << " time: " << time << " increment: " << increment
411 << " moves to go: " << movesToGo << '\n';
414 // Wake up sleeping threads:
415 wake_sleeping_threads();
417 for(int i = 1; i < ActiveThreads; i++)
418 assert(thread_is_available(i, 0));
420 // Set thinking time:
421 if(!movesToGo) { // Sudden death time control
423 MaxSearchTime = time / 30 + increment;
424 AbsoluteMaxSearchTime = Max(time / 4, increment - 100);
426 else { // Blitz game without increment
427 MaxSearchTime = time / 40;
428 AbsoluteMaxSearchTime = time / 8;
431 else { // (x moves) / (y minutes)
433 MaxSearchTime = time / 2;
434 AbsoluteMaxSearchTime = Min(time / 2, time - 500);
437 MaxSearchTime = time / Min(movesToGo, 20);
438 AbsoluteMaxSearchTime = Min((4 * time) / movesToGo, time / 3);
441 if(PonderingEnabled) {
442 MaxSearchTime += MaxSearchTime / 4;
443 MaxSearchTime = Min(MaxSearchTime, AbsoluteMaxSearchTime);
446 // Fixed depth or fixed number of nodes?
449 InfiniteSearch = true; // HACK
453 NodesBetweenPolls = Min(MaxNodes, 30000);
454 InfiniteSearch = true; // HACK
457 NodesBetweenPolls = 30000;
459 // We're ready to start thinking. Call the iterative deepening loop
461 id_loop(pos, searchMoves);
477 /// init_threads() is called during startup. It launches all helper threads,
478 /// and initializes the split point stack and the global locks and condition
481 void init_threads() {
483 #if !defined(_MSC_VER)
484 pthread_t pthread[1];
487 for(i = 0; i < THREAD_MAX; i++)
488 Threads[i].activeSplitPoints = 0;
490 // Initialize global locks:
491 lock_init(&MPLock, NULL);
492 lock_init(&IOLock, NULL);
494 init_split_point_stack();
496 #if !defined(_MSC_VER)
497 pthread_mutex_init(&WaitLock, NULL);
498 pthread_cond_init(&WaitCond, NULL);
500 for(i = 0; i < THREAD_MAX; i++)
501 SitIdleEvent[i] = CreateEvent(0, FALSE, FALSE, 0);
504 // All threads except the main thread should be initialized to idle state:
505 for(i = 1; i < THREAD_MAX; i++) {
506 Threads[i].stop = false;
507 Threads[i].workIsWaiting = false;
508 Threads[i].idle = true;
509 Threads[i].running = false;
512 // Launch the helper threads:
513 for(i = 1; i < THREAD_MAX; i++) {
514 #if !defined(_MSC_VER)
515 pthread_create(pthread, NULL, init_thread, (void*)(&i));
519 CreateThread(NULL, 0, init_thread, (LPVOID)(&i), 0, iID);
523 // Wait until the thread has finished launching:
524 while(!Threads[i].running);
529 /// stop_threads() is called when the program exits. It makes all the
530 /// helper threads exit cleanly.
532 void stop_threads() {
533 ActiveThreads = THREAD_MAX; // HACK
534 Idle = false; // HACK
535 wake_sleeping_threads();
536 AllThreadsShouldExit = true;
537 for(int i = 1; i < THREAD_MAX; i++) {
538 Threads[i].stop = true;
539 while(Threads[i].running);
541 destroy_split_point_stack();
545 /// nodes_searched() returns the total number of nodes searched so far in
546 /// the current search.
548 int64_t nodes_searched() {
549 int64_t result = 0ULL;
550 for(int i = 0; i < ActiveThreads; i++)
551 result += Threads[i].nodes;
558 // id_loop() is the main iterative deepening loop. It calls root_search
559 // repeatedly with increasing depth until the allocated thinking time has
560 // been consumed, the user stops the search, or the maximum search depth is
563 void id_loop(const Position &pos, Move searchMoves[]) {
565 SearchStack ss[PLY_MAX_PLUS_2];
567 // searchMoves are verified, copied, scored and sorted
568 RootMoveList rml(p, searchMoves);
573 init_search_stack(ss);
575 ValueByIteration[0] = Value(0);
576 ValueByIteration[1] = rml.get_move_score(0);
579 EasyMove = rml.scan_for_easy_move();
581 // Iterative deepening loop
582 while(!AbortSearch && Iteration < PLY_MAX) {
584 // Initialize iteration
587 BestMoveChangesByIteration[Iteration] = 0;
591 std::cout << "info depth " << Iteration << std::endl;
593 // Search to the current depth
594 ValueByIteration[Iteration] = root_search(p, ss, rml);
596 // Erase the easy move if it differs from the new best move
597 if(ss[0].pv[0] != EasyMove)
598 EasyMove = MOVE_NONE;
602 if(!InfiniteSearch) {
604 bool stopSearch = false;
606 // Stop search early if there is only a single legal move:
607 if(Iteration >= 6 && rml.move_count() == 1)
610 // Stop search early when the last two iterations returned a mate
613 && abs(ValueByIteration[Iteration]) >= abs(VALUE_MATE) - 100
614 && abs(ValueByIteration[Iteration-1]) >= abs(VALUE_MATE) - 100)
617 // Stop search early if one move seems to be much better than the
619 int64_t nodes = nodes_searched();
620 if(Iteration >= 8 && EasyMove == ss[0].pv[0] &&
621 ((rml.get_move_cumulative_nodes(0) > (nodes * 85) / 100 &&
622 current_search_time() > MaxSearchTime / 16) ||
623 (rml.get_move_cumulative_nodes(0) > (nodes * 98) / 100 &&
624 current_search_time() > MaxSearchTime / 32)))
627 // Add some extra time if the best move has changed during the last
629 if(Iteration > 5 && Iteration <= 50)
631 BestMoveChangesByIteration[Iteration] * (MaxSearchTime / 2) +
632 BestMoveChangesByIteration[Iteration-1] * (MaxSearchTime / 3);
634 // Stop search if most of MaxSearchTime is consumed at the end of the
635 // iteration. We probably don't have enough time to search the first
636 // move at the next iteration anyway.
637 if(current_search_time() > ((MaxSearchTime + ExtraSearchTime)*80) / 128)
644 StopOnPonderhit = true;
648 // Write PV to transposition table, in case the relevant entries have
649 // been overwritten during the search:
650 TT.insert_pv(p, ss[0].pv);
652 if(MaxDepth && Iteration >= MaxDepth)
658 // If we are pondering, we shouldn't print the best move before we
661 wait_for_stop_or_ponderhit();
663 // Print final search statistics
664 std::cout << "info nodes " << nodes_searched() << " nps " << nps()
665 << " time " << current_search_time()
666 << " hashfull " << TT.full() << std::endl;
668 // Print the best move and the ponder move to the standard output:
669 std::cout << "bestmove " << ss[0].pv[0];
670 if(ss[0].pv[1] != MOVE_NONE)
671 std::cout << " ponder " << ss[0].pv[1];
672 std::cout << std::endl;
676 LogFile << "Nodes: " << nodes_searched() << '\n';
677 LogFile << "Nodes/second: " << nps() << '\n';
678 LogFile << "Best move: " << move_to_san(p, ss[0].pv[0]) << '\n';
679 p.do_move(ss[0].pv[0], u);
680 LogFile << "Ponder move: " << move_to_san(p, ss[0].pv[1]) << '\n';
681 LogFile << std::endl;
686 // root_search() is the function which searches the root node. It is
687 // similar to search_pv except that it uses a different move ordering
688 // scheme (perhaps we should try to use this at internal PV nodes, too?)
689 // and prints some information to the standard output.
691 Value root_search(Position &pos, SearchStack ss[], RootMoveList &rml) {
692 Value alpha = -VALUE_INFINITE, beta = VALUE_INFINITE, value;
693 Bitboard dcCandidates = pos.discovered_check_candidates(pos.side_to_move());
695 // Loop through all the moves in the root move list:
696 for(int i = 0; i < rml.move_count() && !AbortSearch; i++) {
702 RootMoveNumber = i + 1;
705 // Remember the node count before the move is searched. The node counts
706 // are used to sort the root moves at the next iteration.
707 nodes = nodes_searched();
709 // Pick the next root move, and print the move and the move number to
710 // the standard output:
711 move = ss[0].currentMove = rml.get_move(i);
712 if(current_search_time() >= 1000)
713 std::cout << "info currmove " << move
714 << " currmovenumber " << i + 1 << std::endl;
716 // Decide search depth for this move:
717 ext = extension(pos, move, true, pos.move_is_check(move), false, false);
718 newDepth = (Iteration-2)*OnePly + ext + InitialDepth;
720 // Make the move, and search it.
721 pos.do_move(move, u, dcCandidates);
724 value = -search_pv(pos, ss, -beta, VALUE_INFINITE, newDepth, 1, 0);
725 // If the value has dropped a lot compared to the last iteration,
726 // set the boolean variable Problem to true. This variable is used
727 // for time managment: When Problem is true, we try to complete the
728 // current iteration before playing a move.
729 Problem = (Iteration >= 2 &&
730 value <= ValueByIteration[Iteration-1] - ProblemMargin);
731 if(Problem && StopOnPonderhit)
732 StopOnPonderhit = false;
735 value = -search(pos, ss, -alpha, newDepth, 1, true, 0);
737 // Fail high! Set the boolean variable FailHigh to true, and
738 // re-search the move with a big window. The variable FailHigh is
739 // used for time managment: We try to avoid aborting the search
740 // prematurely during a fail high research.
742 value = -search_pv(pos, ss, -beta, -alpha, newDepth, 1, 0);
746 pos.undo_move(move, u);
748 // Finished searching the move. If AbortSearch is true, the search
749 // was aborted because the user interrupted the search or because we
750 // ran out of time. In this case, the return value of the search cannot
751 // be trusted, and we break out of the loop without updating the best
756 // Remember the node count for this move. The node counts are used to
757 // sort the root moves at the next iteration.
758 rml.set_move_nodes(i, nodes_searched() - nodes);
760 assert(value >= -VALUE_INFINITE && value <= VALUE_INFINITE);
762 if(value <= alpha && i >= MultiPV)
763 rml.set_move_score(i, -VALUE_INFINITE);
768 rml.set_move_score(i, value);
770 rml.set_move_pv(i, ss[0].pv);
773 // We record how often the best move has been changed in each
774 // iteration. This information is used for time managment: When
775 // the best move changes frequently, we allocate some more time.
777 BestMoveChangesByIteration[Iteration]++;
779 // Print search information to the standard output:
780 std::cout << "info depth " << Iteration
781 << " score " << value_to_string(value)
782 << " time " << current_search_time()
783 << " nodes " << nodes_searched()
786 for(int j = 0; ss[0].pv[j] != MOVE_NONE && j < PLY_MAX; j++)
787 std::cout << ss[0].pv[j] << " ";
788 std::cout << std::endl;
791 LogFile << pretty_pv(pos, current_search_time(), Iteration,
792 nodes_searched(), value, ss[0].pv)
797 // Reset the global variable Problem to false if the value isn't too
798 // far below the final value from the last iteration.
799 if(value > ValueByIteration[Iteration - 1] - NoProblemMargin)
802 else { // MultiPV > 1
804 for(int j = 0; j < Min(MultiPV, rml.move_count()); j++) {
806 std::cout << "info multipv " << j + 1
807 << " score " << value_to_string(rml.get_move_score(j))
808 << " depth " << ((j <= i)? Iteration : Iteration - 1)
809 << " time " << current_search_time()
810 << " nodes " << nodes_searched()
813 for(k = 0; rml.get_move_pv(j, k) != MOVE_NONE && k < PLY_MAX; k++)
814 std::cout << rml.get_move_pv(j, k) << " ";
815 std::cout << std::endl;
817 alpha = rml.get_move_score(Min(i, MultiPV-1));
825 // search_pv() is the main search function for PV nodes.
827 Value search_pv(Position &pos, SearchStack ss[], Value alpha, Value beta,
828 Depth depth, int ply, int threadID) {
829 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
830 assert(beta > alpha && beta <= VALUE_INFINITE);
831 assert(ply >= 0 && ply < PLY_MAX);
832 assert(threadID >= 0 && threadID < ActiveThreads);
836 // Initialize, and make an early exit in case of an aborted search,
837 // an instant draw, maximum ply reached, etc.
838 Value oldAlpha = alpha;
840 if(AbortSearch || thread_should_stop(threadID))
844 return qsearch(pos, ss, alpha, beta, Depth(0), ply, threadID);
846 init_node(pos, ss, ply, threadID);
851 if(ply >= PLY_MAX - 1)
852 return evaluate(pos, ei, threadID);
854 // Mate distance pruning
855 alpha = Max(value_mated_in(ply), alpha);
856 beta = Min(value_mate_in(ply+1), beta);
860 // Transposition table lookup. At PV nodes, we don't use the TT for
861 // pruning, but only for move ordering.
864 Move ttMove = MOVE_NONE;
865 ValueType ttValueType;
867 TT.retrieve(pos, &ttValue, &ttDepth, &ttMove, &ttValueType);
869 // Internal iterative deepening.
870 if(UseIIDAtPVNodes && ttMove == MOVE_NONE && depth >= 5*OnePly) {
871 search_pv(pos, ss, alpha, beta, depth-2*OnePly, ply, threadID);
872 ttMove = ss[ply].pv[ply];
875 // Initialize a MovePicker object for the current position, and prepare
876 // to search all moves:
877 MovePicker mp = MovePicker(pos, true, ttMove, ss[ply].mateKiller,
878 ss[ply].killer1, ss[ply].killer2, depth);
879 Move move, movesSearched[256];
881 Value value, bestValue = -VALUE_INFINITE;
882 Bitboard dcCandidates = mp.discovered_check_candidates();
884 MateThreatExtension[1] > Depth(0)
885 && pos.has_mate_threat(opposite_color(pos.side_to_move()));
887 // Loop through all legal moves until no moves remain or a beta cutoff
889 while(alpha < beta && !thread_should_stop(threadID)
890 && (move = mp.get_next_move()) != MOVE_NONE) {
893 bool singleReply = (pos.is_check() && mp.number_of_moves() == 1);
894 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
895 bool moveIsCapture = pos.move_is_capture(move);
896 bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
898 assert(move_is_ok(move));
899 movesSearched[moveCount++] = ss[ply].currentMove = move;
901 ss[ply].currentMoveCaptureValue = move_is_ep(move)?
902 PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
904 // Decide the new search depth.
905 ext = extension(pos, move, true, moveIsCheck, singleReply, mateThreat);
906 newDepth = depth - OnePly + ext;
908 // Make and search the move.
909 pos.do_move(move, u, dcCandidates);
912 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1, threadID);
914 if(depth >= 2*OnePly && ext == Depth(0) && moveCount >= LMRPVMoves
915 && !moveIsCapture && !move_promotion(move)
916 && !moveIsPassedPawnPush && !move_is_castle(move)
917 && move != ss[ply].killer1 && move != ss[ply].killer2) {
918 ss[ply].reduction = OnePly;
919 value = -search(pos, ss, -alpha, newDepth-OnePly, ply+1, true,
922 else value = alpha + 1;
924 ss[ply].reduction = Depth(0);
925 value = -search(pos, ss, -alpha, newDepth, ply+1, true, threadID);
926 if(value > alpha && value < beta) {
927 if(ply == 1 && RootMoveNumber == 1)
928 // When the search fails high at ply 1 while searching the first
929 // move at the root, set the flag failHighPly1. This is used for
930 // time managment: We don't want to stop the search early in
931 // such cases, because resolving the fail high at ply 1 could
932 // result in a big drop in score at the root.
933 Threads[threadID].failHighPly1 = true;
934 value = -search_pv(pos, ss, -beta, -alpha, newDepth, ply+1,
936 Threads[threadID].failHighPly1 = false;
940 pos.undo_move(move, u);
942 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
945 if(value > bestValue) {
950 if(value == value_mate_in(ply + 1))
951 ss[ply].mateKiller = move;
953 // If we are at ply 1, and we are searching the first root move at
954 // ply 0, set the 'Problem' variable if the score has dropped a lot
955 // (from the computer's point of view) since the previous iteration:
957 -value <= ValueByIteration[Iteration-1] - ProblemMargin)
962 if(ActiveThreads > 1 && bestValue < beta && depth >= MinimumSplitDepth
963 && Iteration <= 99 && idle_thread_exists(threadID)
964 && !AbortSearch && !thread_should_stop(threadID)
965 && split(pos, ss, ply, &alpha, &beta, &bestValue, depth,
966 &moveCount, &mp, dcCandidates, threadID, true))
970 // All legal moves have been searched. A special case: If there were
971 // no legal moves, it must be mate or stalemate:
974 return value_mated_in(ply);
979 // If the search is not aborted, update the transposition table,
980 // history counters, and killer moves. This code is somewhat messy,
981 // and definitely needs to be cleaned up. FIXME
982 if(!AbortSearch && !thread_should_stop(threadID)) {
983 if(bestValue <= oldAlpha)
984 TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE,
986 else if(bestValue >= beta) {
987 Move m = ss[ply].pv[ply];
988 if(pos.square_is_empty(move_to(m)) && !move_promotion(m) &&
990 for(int i = 0; i < moveCount - 1; i++)
991 if(pos.square_is_empty(move_to(movesSearched[i]))
992 && !move_promotion(movesSearched[i])
993 && !move_is_ep(movesSearched[i]))
994 H.failure(pos.piece_on(move_from(movesSearched[i])),
997 H.success(pos.piece_on(move_from(m)), m, depth);
999 if(m != ss[ply].killer1) {
1000 ss[ply].killer2 = ss[ply].killer1;
1001 ss[ply].killer1 = m;
1004 TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
1007 TT.store(pos, value_to_tt(bestValue, ply), depth, ss[ply].pv[ply],
1015 // search() is the search function for zero-width nodes.
1017 Value search(Position &pos, SearchStack ss[], Value beta, Depth depth,
1018 int ply, bool allowNullmove, int threadID) {
1019 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1020 assert(ply >= 0 && ply < PLY_MAX);
1021 assert(threadID >= 0 && threadID < ActiveThreads);
1025 // Initialize, and make an early exit in case of an aborted search,
1026 // an instant draw, maximum ply reached, etc.
1027 if(AbortSearch || thread_should_stop(threadID))
1031 return qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1033 init_node(pos, ss, ply, threadID);
1038 if(ply >= PLY_MAX - 1)
1039 return evaluate(pos, ei, threadID);
1041 // Mate distance pruning
1042 if(value_mated_in(ply) >= beta)
1044 if(value_mate_in(ply+1) < beta)
1047 // Transposition table lookup
1051 Move ttMove = MOVE_NONE;
1052 ValueType ttValueType;
1054 ttFound = TT.retrieve(pos, &ttValue, &ttDepth, &ttMove, &ttValueType);
1056 ttValue = value_from_tt(ttValue, ply);
1058 || ttValue >= Max(value_mate_in(100), beta)
1059 || ttValue < Min(value_mated_in(100), beta)) {
1060 if((is_lower_bound(ttValueType) && ttValue >= beta) ||
1061 (is_upper_bound(ttValueType) && ttValue < beta)) {
1062 ss[ply].currentMove = ttMove;
1068 Value approximateEval = quick_evaluate(pos);
1069 bool mateThreat = false;
1072 if(!pos.is_check() && allowNullmove && ok_to_do_nullmove(pos)
1073 && approximateEval >= beta - NullMoveMargin) {
1077 ss[ply].currentMove = MOVE_NULL;
1078 pos.do_null_move(u);
1079 nullValue = -search(pos, ss, -(beta-1), depth-4*OnePly, ply+1, false,
1081 pos.undo_null_move(u);
1083 if(nullValue >= beta) {
1084 if(depth >= 6 * OnePly) { // Do zugzwang verification search
1085 Value v = search(pos, ss, beta, depth-5*OnePly, ply, false, threadID);
1093 // The null move failed low, which means that we may be faced with
1094 // some kind of threat. If the previous move was reduced, check if
1095 // the move that refuted the null move was somehow connected to the
1096 // move which was reduced. If a connection is found, return a fail
1097 // low score (which will cause the reduced move to fail high in the
1098 // parent node, which will trigger a re-search with full depth).
1099 if(nullValue == value_mated_in(ply+2))
1101 ss[ply].threatMove = ss[ply+1].currentMove;
1102 if(depth < ThreatDepth && ss[ply-1].reduction &&
1103 connected_moves(pos, ss[ply-1].currentMove, ss[ply].threatMove))
1108 else if(depth < RazorDepth && approximateEval < beta - RazorMargin &&
1109 evaluate(pos, ei, threadID) < beta - RazorMargin) {
1110 Value v = qsearch(pos, ss, beta-1, beta, Depth(0), ply, threadID);
1115 // Internal iterative deepening
1116 if(UseIIDAtNonPVNodes && ttMove == MOVE_NONE && depth >= 8*OnePly &&
1117 evaluate(pos, ei, threadID) >= beta - IIDMargin) {
1118 search(pos, ss, beta, Min(depth/2, depth-2*OnePly), ply, false, threadID);
1119 ttMove = ss[ply].pv[ply];
1122 // Initialize a MovePicker object for the current position, and prepare
1123 // to search all moves:
1124 MovePicker mp = MovePicker(pos, false, ttMove, ss[ply].mateKiller,
1125 ss[ply].killer1, ss[ply].killer2, depth);
1126 Move move, movesSearched[256];
1128 Value value, bestValue = -VALUE_INFINITE, futilityValue = VALUE_NONE;
1129 Bitboard dcCandidates = mp.discovered_check_candidates();
1130 bool isCheck = pos.is_check();
1131 bool useFutilityPruning =
1132 UseFutilityPruning && depth < SelectiveDepth && !isCheck;
1134 // Loop through all legal moves until no moves remain or a beta cutoff
1136 while(bestValue < beta && !thread_should_stop(threadID)
1137 && (move = mp.get_next_move()) != MOVE_NONE) {
1139 Depth ext, newDepth;
1140 bool singleReply = (isCheck && mp.number_of_moves() == 1);
1141 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1142 bool moveIsCapture = pos.move_is_capture(move);
1143 bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
1145 assert(move_is_ok(move));
1146 movesSearched[moveCount++] = ss[ply].currentMove = move;
1148 // Decide the new search depth.
1149 ext = extension(pos, move, false, moveIsCheck, singleReply, mateThreat);
1150 newDepth = depth - OnePly + ext;
1153 if(useFutilityPruning && ext == Depth(0) && !moveIsCapture &&
1154 !moveIsPassedPawnPush && !move_promotion(move)) {
1156 if(moveCount >= 2 + int(depth)
1157 && ok_to_prune(pos, move, ss[ply].threatMove, depth))
1160 if(depth < 3 * OnePly && approximateEval < beta) {
1161 if(futilityValue == VALUE_NONE)
1162 futilityValue = evaluate(pos, ei, threadID)
1163 + ((depth < 2 * OnePly)? FutilityMargin1 : FutilityMargin2);
1164 if(futilityValue < beta) {
1165 if(futilityValue > bestValue)
1166 bestValue = futilityValue;
1172 // Make and search the move.
1173 pos.do_move(move, u, dcCandidates);
1175 if(depth >= 2*OnePly && ext == Depth(0) && moveCount >= LMRNonPVMoves
1176 && !moveIsCapture && !move_promotion(move) && !moveIsPassedPawnPush
1177 && !move_is_castle(move)
1178 && move != ss[ply].killer1 && move != ss[ply].killer2) {
1179 ss[ply].reduction = OnePly;
1180 value = -search(pos, ss, -(beta-1), newDepth-OnePly, ply+1, true,
1186 ss[ply].reduction = Depth(0);
1187 value = -search(pos, ss, -(beta-1), newDepth, ply+1, true, threadID);
1189 pos.undo_move(move, u);
1191 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1194 if(value > bestValue) {
1198 if(value == value_mate_in(ply + 1))
1199 ss[ply].mateKiller = move;
1203 if(ActiveThreads > 1 && bestValue < beta && depth >= MinimumSplitDepth
1204 && Iteration <= 99 && idle_thread_exists(threadID)
1205 && !AbortSearch && !thread_should_stop(threadID)
1206 && split(pos, ss, ply, &beta, &beta, &bestValue, depth, &moveCount,
1207 &mp, dcCandidates, threadID, false))
1211 // All legal moves have been searched. A special case: If there were
1212 // no legal moves, it must be mate or stalemate:
1213 if(moveCount == 0) {
1215 return value_mated_in(ply);
1220 // If the search is not aborted, update the transposition table,
1221 // history counters, and killer moves. This code is somewhat messy,
1222 // and definitely needs to be cleaned up. FIXME
1223 if(!AbortSearch && !thread_should_stop(threadID)) {
1224 if(bestValue < beta)
1225 TT.store(pos, value_to_tt(bestValue, ply), depth, MOVE_NONE,
1228 Move m = ss[ply].pv[ply];
1230 if(pos.square_is_empty(move_to(m)) && !move_promotion(m) &&
1232 for(int i = 0; i < moveCount - 1; i++)
1233 if(pos.square_is_empty(move_to(movesSearched[i]))
1234 && !move_promotion(movesSearched[i])
1235 && !move_is_ep(movesSearched[i]))
1236 H.failure(pos.piece_on(move_from(movesSearched[i])),
1238 H.success(pos.piece_on(move_from(m)), m, depth);
1240 if(m != ss[ply].killer1) {
1241 ss[ply].killer2 = ss[ply].killer1;
1242 ss[ply].killer1 = m;
1245 TT.store(pos, value_to_tt(bestValue, ply), depth, m, VALUE_TYPE_LOWER);
1253 // qsearch() is the quiescence search function, which is called by the main
1254 // search function when the remaining depth is zero (or, to be more precise,
1255 // less than OnePly).
1257 Value qsearch(Position &pos, SearchStack ss[], Value alpha, Value beta,
1258 Depth depth, int ply, int threadID) {
1259 Value staticValue, bestValue, value;
1262 assert(alpha >= -VALUE_INFINITE && alpha <= VALUE_INFINITE);
1263 assert(beta >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
1265 assert(ply >= 0 && ply < PLY_MAX);
1266 assert(threadID >= 0 && threadID < ActiveThreads);
1268 // Initialize, and make an early exit in case of an aborted search,
1269 // an instant draw, maximum ply reached, etc.
1270 if(AbortSearch || thread_should_stop(threadID))
1273 init_node(pos, ss, ply, threadID);
1278 // Evaluate the position statically:
1279 staticValue = evaluate(pos, ei, threadID);
1281 if(ply == PLY_MAX - 1) return staticValue;
1283 // Initialize "stand pat score", and return it immediately if it is
1286 bestValue = -VALUE_INFINITE;
1288 bestValue = staticValue;
1289 if(bestValue >= beta)
1291 if(bestValue > alpha)
1295 // Initialize a MovePicker object for the current position, and prepare
1296 // to search the moves. Because the depth is <= 0 here, only captures,
1297 // queen promotions and checks (only if depth == 0) will be generated.
1298 MovePicker mp = MovePicker(pos, false, MOVE_NONE, MOVE_NONE, MOVE_NONE,
1302 Bitboard dcCandidates = mp.discovered_check_candidates();
1303 bool isCheck = pos.is_check();
1305 // Loop through the moves until no moves remain or a beta cutoff
1307 while(alpha < beta && ((move = mp.get_next_move()) != MOVE_NONE)) {
1309 bool moveIsCheck = pos.move_is_check(move, dcCandidates);
1310 bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
1312 assert(move_is_ok(move));
1315 ss[ply].currentMove = move;
1318 if(UseQSearchFutilityPruning && !isCheck && !moveIsCheck &&
1319 !move_promotion(move) && !moveIsPassedPawnPush &&
1320 beta - alpha == 1 &&
1321 pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame) {
1322 Value futilityValue =
1324 + Max(pos.midgame_value_of_piece_on(move_to(move)),
1325 pos.endgame_value_of_piece_on(move_to(move)))
1327 + ei.futilityMargin;
1328 if(futilityValue < alpha) {
1329 if(futilityValue > bestValue)
1330 bestValue = futilityValue;
1335 // Don't search captures and checks with negative SEE values.
1336 if(!isCheck && !move_promotion(move) &&
1337 pos.midgame_value_of_piece_on(move_from(move)) >
1338 pos.midgame_value_of_piece_on(move_to(move)) &&
1342 // Make and search the move.
1343 pos.do_move(move, u, dcCandidates);
1344 value = -qsearch(pos, ss, -beta, -alpha, depth-OnePly, ply+1, threadID);
1345 pos.undo_move(move, u);
1347 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1350 if(value > bestValue) {
1359 // All legal moves have been searched. A special case: If we're in check
1360 // and no legal moves were found, it is checkmate:
1361 if(pos.is_check() && moveCount == 0) // Mate!
1362 return value_mated_in(ply);
1364 assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
1370 // sp_search() is used to search from a split point. This function is called
1371 // by each thread working at the split point. It is similar to the normal
1372 // search() function, but simpler. Because we have already probed the hash
1373 // table, done a null move search, and searched the first move before
1374 // splitting, we don't have to repeat all this work in sp_search(). We
1375 // also don't need to store anything to the hash table here: This is taken
1376 // care of after we return from the split point.
1378 void sp_search(SplitPoint *sp, int threadID) {
1379 assert(threadID >= 0 && threadID < ActiveThreads);
1380 assert(ActiveThreads > 1);
1382 Position pos = Position(sp->pos);
1383 SearchStack *ss = sp->sstack[threadID];
1386 int moveCount = sp->moves;
1387 bool isCheck = pos.is_check();
1388 bool useFutilityPruning =
1389 UseFutilityPruning && sp->depth < SelectiveDepth && !isCheck;
1391 while(sp->bestValue < sp->beta && !thread_should_stop(threadID)
1392 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE) {
1394 Depth ext, newDepth;
1395 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1396 bool moveIsCapture = pos.move_is_capture(move);
1397 bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
1399 assert(move_is_ok(move));
1401 lock_grab(&(sp->lock));
1403 moveCount = sp->moves;
1404 lock_release(&(sp->lock));
1406 ss[sp->ply].currentMove = move;
1408 // Decide the new search depth.
1409 ext = extension(pos, move, false, moveIsCheck, false, false);
1410 newDepth = sp->depth - OnePly + ext;
1413 if(useFutilityPruning && ext == Depth(0) && !moveIsCapture
1414 && !moveIsPassedPawnPush && !move_promotion(move)
1415 && moveCount >= 2 + int(sp->depth)
1416 && ok_to_prune(pos, move, ss[sp->ply].threatMove, sp->depth))
1419 // Make and search the move.
1420 pos.do_move(move, u, sp->dcCandidates);
1421 if(ext == Depth(0) && moveCount >= LMRNonPVMoves
1422 && !moveIsCapture && !move_promotion(move) && !moveIsPassedPawnPush
1423 && !move_is_castle(move)
1424 && move != ss[sp->ply].killer1 && move != ss[sp->ply].killer2) {
1425 ss[sp->ply].reduction = OnePly;
1426 value = -search(pos, ss, -(sp->beta-1), newDepth - OnePly, sp->ply+1,
1431 if(value >= sp->beta) {
1432 ss[sp->ply].reduction = Depth(0);
1433 value = -search(pos, ss, -(sp->beta - 1), newDepth, sp->ply+1, true,
1436 pos.undo_move(move, u);
1438 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1440 if(thread_should_stop(threadID))
1444 lock_grab(&(sp->lock));
1445 if(value > sp->bestValue && !thread_should_stop(threadID)) {
1446 sp->bestValue = value;
1447 if(sp->bestValue >= sp->beta) {
1448 sp_update_pv(sp->parentSstack, ss, sp->ply);
1449 for(int i = 0; i < ActiveThreads; i++)
1450 if(i != threadID && (i == sp->master || sp->slaves[i]))
1451 Threads[i].stop = true;
1452 sp->finished = true;
1455 lock_release(&(sp->lock));
1458 lock_grab(&(sp->lock));
1460 // If this is the master thread and we have been asked to stop because of
1461 // a beta cutoff higher up in the tree, stop all slave threads:
1462 if(sp->master == threadID && thread_should_stop(threadID))
1463 for(int i = 0; i < ActiveThreads; i++)
1465 Threads[i].stop = true;
1468 sp->slaves[threadID] = 0;
1470 lock_release(&(sp->lock));
1474 // sp_search_pv() is used to search from a PV split point. This function
1475 // is called by each thread working at the split point. It is similar to
1476 // the normal search_pv() function, but simpler. Because we have already
1477 // probed the hash table and searched the first move before splitting, we
1478 // don't have to repeat all this work in sp_search_pv(). We also don't
1479 // need to store anything to the hash table here: This is taken care of
1480 // after we return from the split point.
1482 void sp_search_pv(SplitPoint *sp, int threadID) {
1483 assert(threadID >= 0 && threadID < ActiveThreads);
1484 assert(ActiveThreads > 1);
1486 Position pos = Position(sp->pos);
1487 SearchStack *ss = sp->sstack[threadID];
1490 int moveCount = sp->moves;
1492 while(sp->alpha < sp->beta && !thread_should_stop(threadID)
1493 && (move = sp->mp->get_next_move(sp->lock)) != MOVE_NONE) {
1495 Depth ext, newDepth;
1496 bool moveIsCheck = pos.move_is_check(move, sp->dcCandidates);
1497 bool moveIsCapture = pos.move_is_capture(move);
1498 bool moveIsPassedPawnPush = pos.move_is_passed_pawn_push(move);
1500 assert(move_is_ok(move));
1502 ss[sp->ply].currentMoveCaptureValue = move_is_ep(move)?
1503 PawnValueMidgame : pos.midgame_value_of_piece_on(move_to(move));
1505 lock_grab(&(sp->lock));
1507 moveCount = sp->moves;
1508 lock_release(&(sp->lock));
1510 ss[sp->ply].currentMove = move;
1512 // Decide the new search depth.
1513 ext = extension(pos, move, true, moveIsCheck, false, false);
1514 newDepth = sp->depth - OnePly + ext;
1516 // Make and search the move.
1517 pos.do_move(move, u, sp->dcCandidates);
1518 if(ext == Depth(0) && moveCount >= LMRPVMoves && !moveIsCapture
1519 && !move_promotion(move) && !moveIsPassedPawnPush
1520 && !move_is_castle(move)
1521 && move != ss[sp->ply].killer1 && move != ss[sp->ply].killer2) {
1522 ss[sp->ply].reduction = OnePly;
1523 value = -search(pos, ss, -sp->alpha, newDepth - OnePly, sp->ply+1,
1527 value = sp->alpha + 1;
1528 if(value > sp->alpha) {
1529 ss[sp->ply].reduction = Depth(0);
1530 value = -search(pos, ss, -sp->alpha, newDepth, sp->ply+1, true,
1532 if(value > sp->alpha && value < sp->beta) {
1533 if(sp->ply == 1 && RootMoveNumber == 1)
1534 // When the search fails high at ply 1 while searching the first
1535 // move at the root, set the flag failHighPly1. This is used for
1536 // time managment: We don't want to stop the search early in
1537 // such cases, because resolving the fail high at ply 1 could
1538 // result in a big drop in score at the root.
1539 Threads[threadID].failHighPly1 = true;
1540 value = -search_pv(pos, ss, -sp->beta, -sp->alpha, newDepth,
1541 sp->ply+1, threadID);
1542 Threads[threadID].failHighPly1 = false;
1545 pos.undo_move(move, u);
1547 assert(value > -VALUE_INFINITE && value < VALUE_INFINITE);
1549 if(thread_should_stop(threadID))
1553 lock_grab(&(sp->lock));
1554 if(value > sp->bestValue && !thread_should_stop(threadID)) {
1555 sp->bestValue = value;
1556 if(value > sp->alpha) {
1558 sp_update_pv(sp->parentSstack, ss, sp->ply);
1559 if(value == value_mate_in(sp->ply + 1))
1560 ss[sp->ply].mateKiller = move;
1561 if(value >= sp->beta) {
1562 for(int i = 0; i < ActiveThreads; i++)
1563 if(i != threadID && (i == sp->master || sp->slaves[i]))
1564 Threads[i].stop = true;
1565 sp->finished = true;
1568 // If we are at ply 1, and we are searching the first root move at
1569 // ply 0, set the 'Problem' variable if the score has dropped a lot
1570 // (from the computer's point of view) since the previous iteration:
1571 if(Iteration >= 2 &&
1572 -value <= ValueByIteration[Iteration-1] - ProblemMargin)
1575 lock_release(&(sp->lock));
1578 lock_grab(&(sp->lock));
1580 // If this is the master thread and we have been asked to stop because of
1581 // a beta cutoff higher up in the tree, stop all slave threads:
1582 if(sp->master == threadID && thread_should_stop(threadID))
1583 for(int i = 0; i < ActiveThreads; i++)
1585 Threads[i].stop = true;
1588 sp->slaves[threadID] = 0;
1590 lock_release(&(sp->lock));
1594 /// The RootMove class
1598 RootMove::RootMove() {
1599 nodes = cumulativeNodes = 0ULL;
1603 /// The RootMoveList class
1607 RootMoveList::RootMoveList(Position& pos, Move searchMoves[]) : count(0) {
1609 MoveStack mlist[MaxRootMoves];
1610 bool includeAllMoves = (searchMoves[0] == MOVE_NONE);
1612 // Generate all legal moves
1613 int lm_count = generate_legal_moves(pos, mlist);
1615 // Add each move to the moves[] array
1616 for (int i = 0; i < lm_count; i++)
1618 bool includeMove = includeAllMoves;
1620 for (int k = 0; !includeMove && searchMoves[k] != MOVE_NONE; k++)
1621 includeMove = (searchMoves[k] == mlist[i].move);
1625 // Find a quick score for the move
1627 SearchStack ss[PLY_MAX_PLUS_2];
1629 moves[count].move = mlist[i].move;
1630 moves[count].nodes = 0ULL;
1631 pos.do_move(moves[count].move, u);
1632 moves[count].score = -qsearch(pos, ss, -VALUE_INFINITE, VALUE_INFINITE,
1634 pos.undo_move(moves[count].move, u);
1635 moves[count].pv[0] = moves[i].move;
1636 moves[count].pv[1] = MOVE_NONE; // FIXME
1644 // Simple accessor methods for the RootMoveList class
1646 Move RootMoveList::get_move(int moveNum) const {
1647 return moves[moveNum].move;
1650 Value RootMoveList::get_move_score(int moveNum) const {
1651 return moves[moveNum].score;
1654 void RootMoveList::set_move_score(int moveNum, Value score) {
1655 moves[moveNum].score = score;
1658 void RootMoveList::set_move_nodes(int moveNum, int64_t nodes) {
1659 moves[moveNum].nodes = nodes;
1660 moves[moveNum].cumulativeNodes += nodes;
1663 void RootMoveList::set_move_pv(int moveNum, const Move pv[]) {
1665 for(j = 0; pv[j] != MOVE_NONE; j++)
1666 moves[moveNum].pv[j] = pv[j];
1667 moves[moveNum].pv[j] = MOVE_NONE;
1670 Move RootMoveList::get_move_pv(int moveNum, int i) const {
1671 return moves[moveNum].pv[i];
1674 int64_t RootMoveList::get_move_cumulative_nodes(int moveNum) {
1675 return moves[moveNum].cumulativeNodes;
1678 int RootMoveList::move_count() const {
1683 // RootMoveList::scan_for_easy_move() is called at the end of the first
1684 // iteration, and is used to detect an "easy move", i.e. a move which appears
1685 // to be much bester than all the rest. If an easy move is found, the move
1686 // is returned, otherwise the function returns MOVE_NONE. It is very
1687 // important that this function is called at the right moment: The code
1688 // assumes that the first iteration has been completed and the moves have
1689 // been sorted. This is done in RootMoveList c'tor.
1691 Move RootMoveList::scan_for_easy_move() const {
1693 Value bestMoveValue = this->get_move_score(0);
1694 for(int i = 1; i < this->move_count(); i++)
1695 if(this->get_move_score(i) >= bestMoveValue - EasyMoveMargin)
1697 return this->get_move(0);
1701 // RootMoveList::sort() sorts the root move list at the beginning of a new
1704 void RootMoveList::sort() {
1705 for(int i = 1; i < count; i++) {
1706 RootMove rm = moves[i];
1708 for(j = i; j > 0 && compare_root_moves(moves[j-1], rm); j--)
1709 moves[j] = moves[j-1];
1715 // RootMoveList::sort_multipv() sorts the first few moves in the root move
1716 // list by their scores and depths. It is used to order the different PVs
1717 // correctly in MultiPV mode.
1719 void RootMoveList::sort_multipv(int n) {
1720 for(int i = 1; i <= n; i++) {
1721 RootMove rm = moves[i];
1723 for(j = i; j > 0 && moves[j-1].score < rm.score; j--)
1724 moves[j] = moves[j-1];
1730 // RootMoveList::compare_root_moves() is the comparison function used by
1731 // RootMoveList::sort when sorting the moves. A move m1 is considered to
1732 // be better than a move m2 if it has a higher score, or if the moves have
1733 // equal score but m1 has the higher node count.
1735 bool RootMoveList::compare_root_moves(const RootMove &rm1,
1736 const RootMove &rm2) {
1738 if (rm1.score != rm2.score)
1739 return (rm1.score < rm2.score);
1741 return rm1.nodes <= rm2.nodes;
1745 // init_search_stack() initializes a search stack at the beginning of a
1746 // new search from the root.
1748 void init_search_stack(SearchStack ss[]) {
1749 for(int i = 0; i < 3; i++) {
1750 ss[i].pv[i] = MOVE_NONE;
1751 ss[i].pv[i+1] = MOVE_NONE;
1752 ss[i].currentMove = MOVE_NONE;
1753 ss[i].mateKiller = MOVE_NONE;
1754 ss[i].killer1 = MOVE_NONE;
1755 ss[i].killer2 = MOVE_NONE;
1756 ss[i].threatMove = MOVE_NONE;
1757 ss[i].reduction = Depth(0);
1762 // init_node() is called at the beginning of all the search functions
1763 // (search(), search_pv(), qsearch(), and so on) and initializes the search
1764 // stack object corresponding to the current node. Once every
1765 // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
1766 // for user input and checks whether it is time to stop the search.
1768 void init_node(const Position &pos, SearchStack ss[], int ply, int threadID) {
1769 assert(ply >= 0 && ply < PLY_MAX);
1770 assert(threadID >= 0 && threadID < ActiveThreads);
1772 Threads[threadID].nodes++;
1776 if(NodesSincePoll >= NodesBetweenPolls) {
1782 ss[ply].pv[ply] = ss[ply].pv[ply+1] = ss[ply].currentMove = MOVE_NONE;
1783 ss[ply+2].mateKiller = MOVE_NONE;
1784 ss[ply+2].killer1 = ss[ply+2].killer2 = MOVE_NONE;
1785 ss[ply].threatMove = MOVE_NONE;
1786 ss[ply].reduction = Depth(0);
1787 ss[ply].currentMoveCaptureValue = Value(0);
1789 if(Threads[threadID].printCurrentLine)
1790 print_current_line(ss, ply, threadID);
1794 // update_pv() is called whenever a search returns a value > alpha. It
1795 // updates the PV in the SearchStack object corresponding to the current
1798 void update_pv(SearchStack ss[], int ply) {
1799 assert(ply >= 0 && ply < PLY_MAX);
1801 ss[ply].pv[ply] = ss[ply].currentMove;
1803 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
1804 ss[ply].pv[p] = ss[ply+1].pv[p];
1805 ss[ply].pv[p] = MOVE_NONE;
1809 // sp_update_pv() is a variant of update_pv for use at split points. The
1810 // difference between the two functions is that sp_update_pv also updates
1811 // the PV at the parent node.
1813 void sp_update_pv(SearchStack *pss, SearchStack ss[], int ply) {
1814 assert(ply >= 0 && ply < PLY_MAX);
1816 ss[ply].pv[ply] = pss[ply].pv[ply] = ss[ply].currentMove;
1818 for(p = ply + 1; ss[ply+1].pv[p] != MOVE_NONE; p++)
1819 ss[ply].pv[p] = pss[ply].pv[p] = ss[ply+1].pv[p];
1820 ss[ply].pv[p] = pss[ply].pv[p] = MOVE_NONE;
1824 // connected_moves() tests whether two moves are 'connected' in the sense
1825 // that the first move somehow made the second move possible (for instance
1826 // if the moving piece is the same in both moves). The first move is
1827 // assumed to be the move that was made to reach the current position, while
1828 // the second move is assumed to be a move from the current position.
1830 bool connected_moves(const Position &pos, Move m1, Move m2) {
1831 Square f1, t1, f2, t2;
1833 assert(move_is_ok(m1));
1834 assert(move_is_ok(m2));
1839 // Case 1: The moving piece is the same in both moves.
1845 // Case 2: The destination square for m2 was vacated by m1.
1851 // Case 3: Moving through the vacated square:
1852 if(piece_is_slider(pos.piece_on(f2)) &&
1853 bit_is_set(squares_between(f2, t2), f1))
1856 // Case 4: The destination square for m2 is attacked by the moving piece
1858 if(pos.piece_attacks_square(t1, t2))
1861 // Case 5: Discovered check, checking piece is the piece moved in m1:
1862 if(piece_is_slider(pos.piece_on(t1)) &&
1863 bit_is_set(squares_between(t1, pos.king_square(pos.side_to_move())),
1865 !bit_is_set(squares_between(t2, pos.king_square(pos.side_to_move())),
1867 Bitboard occ = pos.occupied_squares();
1868 Color us = pos.side_to_move();
1869 Square ksq = pos.king_square(us);
1870 clear_bit(&occ, f2);
1871 if(pos.type_of_piece_on(t1) == BISHOP) {
1872 if(bit_is_set(bishop_attacks_bb(ksq, occ), t1))
1875 else if(pos.type_of_piece_on(t1) == ROOK) {
1876 if(bit_is_set(rook_attacks_bb(ksq, occ), t1))
1880 assert(pos.type_of_piece_on(t1) == QUEEN);
1881 if(bit_is_set(queen_attacks_bb(ksq, occ), t1))
1890 // extension() decides whether a move should be searched with normal depth,
1891 // or with extended depth. Certain classes of moves (checking moves, in
1892 // particular) are searched with bigger depth than ordinary moves.
1894 Depth extension(const Position &pos, Move m, bool pvNode,
1895 bool check, bool singleReply, bool mateThreat) {
1896 Depth result = Depth(0);
1899 result += CheckExtension[pvNode];
1901 result += SingleReplyExtension[pvNode];
1902 if(pos.move_is_pawn_push_to_7th(m))
1903 result += PawnPushTo7thExtension[pvNode];
1904 if(pos.move_is_passed_pawn_push(m))
1905 result += PassedPawnExtension[pvNode];
1907 result += MateThreatExtension[pvNode];
1908 if(pos.midgame_value_of_piece_on(move_to(m)) >= RookValueMidgame
1909 && (pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
1910 - pos.midgame_value_of_piece_on(move_to(m)) == Value(0))
1911 && !move_promotion(m))
1912 result += PawnEndgameExtension[pvNode];
1913 if(pvNode && pos.move_is_capture(m)
1914 && pos.type_of_piece_on(move_to(m)) != PAWN && pos.see(m) >= 0)
1917 return Min(result, OnePly);
1921 // ok_to_do_nullmove() looks at the current position and decides whether
1922 // doing a 'null move' should be allowed. In order to avoid zugzwang
1923 // problems, null moves are not allowed when the side to move has very
1924 // little material left. Currently, the test is a bit too simple: Null
1925 // moves are avoided only when the side to move has only pawns left. It's
1926 // probably a good idea to avoid null moves in at least some more
1927 // complicated endgames, e.g. KQ vs KR. FIXME
1929 bool ok_to_do_nullmove(const Position &pos) {
1930 if(pos.non_pawn_material(pos.side_to_move()) == Value(0))
1936 // ok_to_prune() tests whether it is safe to forward prune a move. Only
1937 // non-tactical moves late in the move list close to the leaves are
1938 // candidates for pruning.
1940 bool ok_to_prune(const Position &pos, Move m, Move threat, Depth d) {
1941 Square mfrom, mto, tfrom, tto;
1943 assert(move_is_ok(m));
1944 assert(threat == MOVE_NONE || move_is_ok(threat));
1945 assert(!move_promotion(m));
1946 assert(!pos.move_is_check(m));
1947 assert(!pos.move_is_capture(m));
1948 assert(!pos.move_is_passed_pawn_push(m));
1949 assert(d >= OnePly);
1951 mfrom = move_from(m);
1953 tfrom = move_from(threat);
1954 tto = move_to(threat);
1956 // Case 1: Castling moves are never pruned.
1957 if(move_is_castle(m))
1960 // Case 2: Don't prune moves which move the threatened piece
1961 if(!PruneEscapeMoves && threat != MOVE_NONE && mfrom == tto)
1964 // Case 3: If the threatened piece has value less than or equal to the
1965 // value of the threatening piece, don't prune move which defend it.
1966 if(!PruneDefendingMoves && threat != MOVE_NONE
1967 && (piece_value_midgame(pos.piece_on(tfrom))
1968 >= piece_value_midgame(pos.piece_on(tto)))
1969 && pos.move_attacks_square(m, tto))
1972 // Case 4: Don't prune moves with good history.
1973 if(!H.ok_to_prune(pos.piece_on(move_from(m)), m, d))
1976 // Case 5: If the moving piece in the threatened move is a slider, don't
1977 // prune safe moves which block its ray.
1978 if(!PruneBlockingMoves && threat != MOVE_NONE
1979 && piece_is_slider(pos.piece_on(tfrom))
1980 && bit_is_set(squares_between(tfrom, tto), mto) && pos.see(m) >= 0)
1987 // fail_high_ply_1() checks if some thread is currently resolving a fail
1988 // high at ply 1 at the node below the first root node. This information
1989 // is used for time managment.
1991 bool fail_high_ply_1() {
1992 for(int i = 0; i < ActiveThreads; i++)
1993 if(Threads[i].failHighPly1)
1999 // current_search_time() returns the number of milliseconds which have passed
2000 // since the beginning of the current search.
2002 int current_search_time() {
2003 return get_system_time() - SearchStartTime;
2007 // nps() computes the current nodes/second count.
2010 int t = current_search_time();
2011 return (t > 0)? int((nodes_searched() * 1000) / t) : 0;
2015 // poll() performs two different functions: It polls for user input, and it
2016 // looks at the time consumed so far and decides if it's time to abort the
2021 static int lastInfoTime;
2023 t = current_search_time();
2029 if(fgets(input, 255, stdin) == NULL)
2030 strcpy(input, "quit\n");
2031 if(strncmp(input, "quit", 4) == 0) {
2033 PonderSearch = false;
2036 else if(strncmp(input, "stop", 4) == 0) {
2038 PonderSearch = false;
2040 else if(strncmp(input, "ponderhit", 9) == 0)
2044 // Print search information
2047 else if(lastInfoTime > t)
2048 // HACK: Must be a new search where we searched less than
2049 // NodesBetweenPolls nodes during the first second of search.
2051 else if(t - lastInfoTime >= 1000) {
2054 std::cout << "info nodes " << nodes_searched() << " nps " << nps()
2055 << " time " << t << " hashfull " << TT.full() << std::endl;
2056 lock_release(&IOLock);
2058 Threads[0].printCurrentLine = true;
2061 // Should we stop the search?
2062 if(!PonderSearch && Iteration >= 2 &&
2063 (!InfiniteSearch && (t > AbsoluteMaxSearchTime ||
2064 (RootMoveNumber == 1 &&
2065 t > MaxSearchTime + ExtraSearchTime) ||
2066 (!FailHigh && !fail_high_ply_1() && !Problem &&
2067 t > 6*(MaxSearchTime + ExtraSearchTime)))))
2070 if(!PonderSearch && ExactMaxTime && t >= ExactMaxTime)
2073 if(!PonderSearch && Iteration >= 3 && MaxNodes
2074 && nodes_searched() >= MaxNodes)
2079 // ponderhit() is called when the program is pondering (i.e. thinking while
2080 // it's the opponent's turn to move) in order to let the engine know that
2081 // it correctly predicted the opponent's move.
2084 int t = current_search_time();
2085 PonderSearch = false;
2086 if(Iteration >= 2 &&
2087 (!InfiniteSearch && (StopOnPonderhit ||
2088 t > AbsoluteMaxSearchTime ||
2089 (RootMoveNumber == 1 &&
2090 t > MaxSearchTime + ExtraSearchTime) ||
2091 (!FailHigh && !fail_high_ply_1() && !Problem &&
2092 t > 6*(MaxSearchTime + ExtraSearchTime)))))
2097 // print_current_line() prints the current line of search for a given
2098 // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
2100 void print_current_line(SearchStack ss[], int ply, int threadID) {
2101 assert(ply >= 0 && ply < PLY_MAX);
2102 assert(threadID >= 0 && threadID < ActiveThreads);
2104 if(!Threads[threadID].idle) {
2106 std::cout << "info currline " << (threadID + 1);
2107 for(int p = 0; p < ply; p++)
2108 std::cout << " " << ss[p].currentMove;
2109 std::cout << std::endl;
2110 lock_release(&IOLock);
2112 Threads[threadID].printCurrentLine = false;
2113 if(threadID + 1 < ActiveThreads)
2114 Threads[threadID + 1].printCurrentLine = true;
2118 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2119 // while the program is pondering. The point is to work around a wrinkle in
2120 // the UCI protocol: When pondering, the engine is not allowed to give a
2121 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2122 // We simply wait here until one of these commands is sent, and return,
2123 // after which the bestmove and pondermove will be printed (in id_loop()).
2125 void wait_for_stop_or_ponderhit() {
2126 std::string command;
2129 if(!std::getline(std::cin, command))
2132 if(command == "quit") {
2133 OpeningBook.close();
2138 else if(command == "ponderhit" || command == "stop")
2144 // idle_loop() is where the threads are parked when they have no work to do.
2145 // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
2146 // object for which the current thread is the master.
2148 void idle_loop(int threadID, SplitPoint *waitSp) {
2149 assert(threadID >= 0 && threadID < THREAD_MAX);
2151 Threads[threadID].running = true;
2154 if(AllThreadsShouldExit && threadID != 0)
2157 // If we are not thinking, wait for a condition to be signaled instead
2158 // of wasting CPU time polling for work:
2159 while(threadID != 0 && (Idle || threadID >= ActiveThreads)) {
2160 #if !defined(_MSC_VER)
2161 pthread_mutex_lock(&WaitLock);
2162 if(Idle || threadID >= ActiveThreads)
2163 pthread_cond_wait(&WaitCond, &WaitLock);
2164 pthread_mutex_unlock(&WaitLock);
2166 WaitForSingleObject(SitIdleEvent[threadID], INFINITE);
2170 // If this thread has been assigned work, launch a search:
2171 if(Threads[threadID].workIsWaiting) {
2172 Threads[threadID].workIsWaiting = false;
2173 if(Threads[threadID].splitPoint->pvNode)
2174 sp_search_pv(Threads[threadID].splitPoint, threadID);
2176 sp_search(Threads[threadID].splitPoint, threadID);
2177 Threads[threadID].idle = true;
2180 // If this thread is the master of a split point and all threads have
2181 // finished their work at this split point, return from the idle loop:
2182 if(waitSp != NULL && waitSp->cpus == 0)
2186 Threads[threadID].running = false;
2190 // init_split_point_stack() is called during program initialization, and
2191 // initializes all split point objects.
2193 void init_split_point_stack() {
2194 for(int i = 0; i < THREAD_MAX; i++)
2195 for(int j = 0; j < MaxActiveSplitPoints; j++) {
2196 SplitPointStack[i][j].parent = NULL;
2197 lock_init(&(SplitPointStack[i][j].lock), NULL);
2202 // destroy_split_point_stack() is called when the program exits, and
2203 // destroys all locks in the precomputed split point objects.
2205 void destroy_split_point_stack() {
2206 for(int i = 0; i < THREAD_MAX; i++)
2207 for(int j = 0; j < MaxActiveSplitPoints; j++)
2208 lock_destroy(&(SplitPointStack[i][j].lock));
2212 // thread_should_stop() checks whether the thread with a given threadID has
2213 // been asked to stop, directly or indirectly. This can happen if a beta
2214 // cutoff has occured in thre thread's currently active split point, or in
2215 // some ancestor of the current split point.
2217 bool thread_should_stop(int threadID) {
2218 assert(threadID >= 0 && threadID < ActiveThreads);
2222 if(Threads[threadID].stop)
2224 if(ActiveThreads <= 2)
2226 for(sp = Threads[threadID].splitPoint; sp != NULL; sp = sp->parent)
2228 Threads[threadID].stop = true;
2235 // thread_is_available() checks whether the thread with threadID "slave" is
2236 // available to help the thread with threadID "master" at a split point. An
2237 // obvious requirement is that "slave" must be idle. With more than two
2238 // threads, this is not by itself sufficient: If "slave" is the master of
2239 // some active split point, it is only available as a slave to the other
2240 // threads which are busy searching the split point at the top of "slave"'s
2241 // split point stack (the "helpful master concept" in YBWC terminology).
2243 bool thread_is_available(int slave, int master) {
2244 assert(slave >= 0 && slave < ActiveThreads);
2245 assert(master >= 0 && master < ActiveThreads);
2246 assert(ActiveThreads > 1);
2248 if(!Threads[slave].idle || slave == master)
2251 if(Threads[slave].activeSplitPoints == 0)
2252 // No active split points means that the thread is available as a slave
2253 // for any other thread.
2256 if(ActiveThreads == 2)
2259 // Apply the "helpful master" concept if possible.
2260 if(SplitPointStack[slave][Threads[slave].activeSplitPoints-1].slaves[master])
2267 // idle_thread_exists() tries to find an idle thread which is available as
2268 // a slave for the thread with threadID "master".
2270 bool idle_thread_exists(int master) {
2271 assert(master >= 0 && master < ActiveThreads);
2272 assert(ActiveThreads > 1);
2274 for(int i = 0; i < ActiveThreads; i++)
2275 if(thread_is_available(i, master))
2281 // split() does the actual work of distributing the work at a node between
2282 // several threads at PV nodes. If it does not succeed in splitting the
2283 // node (because no idle threads are available, or because we have no unused
2284 // split point objects), the function immediately returns false. If
2285 // splitting is possible, a SplitPoint object is initialized with all the
2286 // data that must be copied to the helper threads (the current position and
2287 // search stack, alpha, beta, the search depth, etc.), and we tell our
2288 // helper threads that they have been assigned work. This will cause them
2289 // to instantly leave their idle loops and call sp_search_pv(). When all
2290 // threads have returned from sp_search_pv (or, equivalently, when
2291 // splitPoint->cpus becomes 0), split() returns true.
2293 bool split(const Position &p, SearchStack *sstck, int ply,
2294 Value *alpha, Value *beta, Value *bestValue,
2295 Depth depth, int *moves,
2296 MovePicker *mp, Bitboard dcCandidates, int master, bool pvNode) {
2298 assert(sstck != NULL);
2299 assert(ply >= 0 && ply < PLY_MAX);
2300 assert(*bestValue >= -VALUE_INFINITE && *bestValue <= *alpha);
2301 assert(!pvNode || *alpha < *beta);
2302 assert(*beta <= VALUE_INFINITE);
2303 assert(depth > Depth(0));
2304 assert(master >= 0 && master < ActiveThreads);
2305 assert(ActiveThreads > 1);
2307 SplitPoint *splitPoint;
2312 // If no other thread is available to help us, or if we have too many
2313 // active split points, don't split:
2314 if(!idle_thread_exists(master) ||
2315 Threads[master].activeSplitPoints >= MaxActiveSplitPoints) {
2316 lock_release(&MPLock);
2320 // Pick the next available split point object from the split point stack:
2321 splitPoint = SplitPointStack[master] + Threads[master].activeSplitPoints;
2322 Threads[master].activeSplitPoints++;
2324 // Initialize the split point object:
2325 splitPoint->parent = Threads[master].splitPoint;
2326 splitPoint->finished = false;
2327 splitPoint->ply = ply;
2328 splitPoint->depth = depth;
2329 splitPoint->alpha = pvNode? *alpha : (*beta - 1);
2330 splitPoint->beta = *beta;
2331 splitPoint->pvNode = pvNode;
2332 splitPoint->dcCandidates = dcCandidates;
2333 splitPoint->bestValue = *bestValue;
2334 splitPoint->master = master;
2335 splitPoint->mp = mp;
2336 splitPoint->moves = *moves;
2337 splitPoint->cpus = 1;
2338 splitPoint->pos.copy(p);
2339 splitPoint->parentSstack = sstck;
2340 for(i = 0; i < ActiveThreads; i++)
2341 splitPoint->slaves[i] = 0;
2343 // Copy the current position and the search stack to the master thread:
2344 memcpy(splitPoint->sstack[master], sstck, (ply+1)*sizeof(SearchStack));
2345 Threads[master].splitPoint = splitPoint;
2347 // Make copies of the current position and search stack for each thread:
2348 for(i = 0; i < ActiveThreads && splitPoint->cpus < MaxThreadsPerSplitPoint;
2350 if(thread_is_available(i, master)) {
2351 memcpy(splitPoint->sstack[i], sstck, (ply+1)*sizeof(SearchStack));
2352 Threads[i].splitPoint = splitPoint;
2353 splitPoint->slaves[i] = 1;
2357 // Tell the threads that they have work to do. This will make them leave
2359 for(i = 0; i < ActiveThreads; i++)
2360 if(i == master || splitPoint->slaves[i]) {
2361 Threads[i].workIsWaiting = true;
2362 Threads[i].idle = false;
2363 Threads[i].stop = false;
2366 lock_release(&MPLock);
2368 // Everything is set up. The master thread enters the idle loop, from
2369 // which it will instantly launch a search, because its workIsWaiting
2370 // slot is 'true'. We send the split point as a second parameter to the
2371 // idle loop, which means that the main thread will return from the idle
2372 // loop when all threads have finished their work at this split point
2373 // (i.e. when // splitPoint->cpus == 0).
2374 idle_loop(master, splitPoint);
2376 // We have returned from the idle loop, which means that all threads are
2377 // finished. Update alpha, beta and bestvalue, and return:
2379 if(pvNode) *alpha = splitPoint->alpha;
2380 *beta = splitPoint->beta;
2381 *bestValue = splitPoint->bestValue;
2382 Threads[master].stop = false;
2383 Threads[master].idle = false;
2384 Threads[master].activeSplitPoints--;
2385 Threads[master].splitPoint = splitPoint->parent;
2386 lock_release(&MPLock);
2392 // wake_sleeping_threads() wakes up all sleeping threads when it is time
2393 // to start a new search from the root.
2395 void wake_sleeping_threads() {
2396 if(ActiveThreads > 1) {
2397 for(int i = 1; i < ActiveThreads; i++) {
2398 Threads[i].idle = true;
2399 Threads[i].workIsWaiting = false;
2401 #if !defined(_MSC_VER)
2402 pthread_mutex_lock(&WaitLock);
2403 pthread_cond_broadcast(&WaitCond);
2404 pthread_mutex_unlock(&WaitLock);
2406 for(int i = 1; i < THREAD_MAX; i++)
2407 SetEvent(SitIdleEvent[i]);
2413 // init_thread() is the function which is called when a new thread is
2414 // launched. It simply calls the idle_loop() function with the supplied
2415 // threadID. There are two versions of this function; one for POSIX threads
2416 // and one for Windows threads.
2418 #if !defined(_MSC_VER)
2420 void *init_thread(void *threadID) {
2421 idle_loop(*(int *)threadID, NULL);
2427 DWORD WINAPI init_thread(LPVOID threadID) {
2428 idle_loop(*(int *)threadID, NULL);