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/>.
38 #include "ucioption.h"
42 //// Local definitions
49 // The RootMove class is used for moves at the root at the tree. For each
50 // root move, we store a score, a node count, and a PV (really a refutation
51 // in the case of moves which fail low).
56 bool operator<(const RootMove
&); // used to sort
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 inline Move
get_move(int moveNum
) const;
73 inline Value
get_move_score(int moveNum
) const;
74 inline void set_move_score(int moveNum
, Value score
);
75 inline void set_move_nodes(int moveNum
, int64_t nodes
);
76 void set_move_pv(int moveNum
, const Move pv
[]);
77 inline Move
get_move_pv(int moveNum
, int i
) const;
78 inline int64_t get_move_cumulative_nodes(int moveNum
) const;
79 inline int move_count() const;
80 Move
scan_for_easy_move() const;
82 void sort_multipv(int n
);
85 static const int MaxRootMoves
= 500;
86 RootMove moves
[MaxRootMoves
];
91 /// Constants and variables
93 // Minimum number of full depth (i.e. non-reduced) moves at PV and non-PV
96 int LMRNonPVMoves
= 4;
98 // Depth limit for use of dynamic threat detection:
99 Depth ThreatDepth
= 5*OnePly
;
101 // Depth limit for selective search:
102 Depth SelectiveDepth
= 7*OnePly
;
104 // Use internal iterative deepening?
105 const bool UseIIDAtPVNodes
= true;
106 const bool UseIIDAtNonPVNodes
= false;
108 // Internal iterative deepening margin. At Non-PV moves, when
109 // UseIIDAtNonPVNodes is true, we do an internal iterative deepening search
110 // when the static evaluation is at most IIDMargin below beta.
111 const Value IIDMargin
= Value(0x100);
114 const bool UseEasyMove
= true;
116 // Easy move margin. An easy move candidate must be at least this much
117 // better than the second best move.
118 const Value EasyMoveMargin
= Value(0x200);
120 // Problem margin. If the score of the first move at iteration N+1 has
121 // dropped by more than this since iteration N, the boolean variable
122 // "Problem" is set to true, which will make the program spend some extra
123 // time looking for a better move.
124 const Value ProblemMargin
= Value(0x28);
126 // No problem margin. If the boolean "Problem" is true, and a new move
127 // is found at the root which is less than NoProblemMargin worse than the
128 // best move from the previous iteration, Problem is set back to false.
129 const Value NoProblemMargin
= Value(0x14);
131 // Null move margin. A null move search will not be done if the approximate
132 // evaluation of the position is more than NullMoveMargin below beta.
133 const Value NullMoveMargin
= Value(0x300);
135 // Pruning criterions. See the code and comments in ok_to_prune() to
136 // understand their precise meaning.
137 const bool PruneEscapeMoves
= false;
138 const bool PruneDefendingMoves
= false;
139 const bool PruneBlockingMoves
= false;
141 // Use futility pruning?
142 bool UseQSearchFutilityPruning
= true;
143 bool UseFutilityPruning
= true;
145 // Margins for futility pruning in the quiescence search, at frontier
146 // nodes, and at pre-frontier nodes:
147 Value FutilityMargin0
= Value(0x80);
148 Value FutilityMargin1
= Value(0x100);
149 Value FutilityMargin2
= Value(0x300);
152 Depth RazorDepth
= 4*OnePly
;
153 Value RazorMargin
= Value(0x300);
155 // Extensions. Array index 0 is used at non-PV nodes, index 1 at PV nodes.
156 Depth CheckExtension
[2] = {OnePly
, OnePly
};
157 Depth SingleReplyExtension
[2] = {OnePly
/ 2, OnePly
/ 2};
158 Depth PawnPushTo7thExtension
[2] = {OnePly
/ 2, OnePly
/ 2};
159 Depth PassedPawnExtension
[2] = {Depth(0), Depth(0)};
160 Depth PawnEndgameExtension
[2] = {OnePly
, OnePly
};
161 Depth MateThreatExtension
[2] = {Depth(0), Depth(0)};
163 // Search depth at iteration 1:
164 const Depth InitialDepth
= OnePly
/*+ OnePly/2*/;
168 int NodesBetweenPolls
= 30000;
170 // Iteration counter:
173 // Scores and number of times the best move changed for each iteration:
174 Value ValueByIteration
[PLY_MAX_PLUS_2
];
175 int BestMoveChangesByIteration
[PLY_MAX_PLUS_2
];
180 // Time managment variables
182 int MaxNodes
, MaxDepth
;
183 int MaxSearchTime
, AbsoluteMaxSearchTime
, ExtraSearchTime
, TimeAdvantage
;
184 Move BestRootMove
, PonderMove
, EasyMove
;
188 bool StopOnPonderhit
;
193 bool PonderingEnabled
;
196 // Show current line?
197 bool ShowCurrentLine
= false;
200 bool UseLogFile
= false;
201 std::ofstream LogFile
;
203 // MP related variables
204 Depth MinimumSplitDepth
= 4*OnePly
;
205 int MaxThreadsPerSplitPoint
= 4;
206 Thread Threads
[THREAD_MAX
];
208 bool AllThreadsShouldExit
= false;
209 const int MaxActiveSplitPoints
= 8;
210 SplitPoint SplitPointStack
[THREAD_MAX
][MaxActiveSplitPoints
];
213 #if !defined(_MSC_VER)
214 pthread_cond_t WaitCond
;
215 pthread_mutex_t WaitLock
;
217 HANDLE SitIdleEvent
[THREAD_MAX
];
223 void id_loop(const Position
&pos
, Move searchMoves
[]);
224 Value
root_search(Position
&pos
, SearchStack ss
[], RootMoveList
&rml
);
225 Value
search_pv(Position
&pos
, SearchStack ss
[], Value alpha
, Value beta
,
226 Depth depth
, int ply
, int threadID
);
227 Value
search(Position
&pos
, SearchStack ss
[], Value beta
,
228 Depth depth
, int ply
, bool allowNullmove
, int threadID
);
229 Value
qsearch(Position
&pos
, SearchStack ss
[], Value alpha
, Value beta
,
230 Depth depth
, int ply
, int threadID
);
231 void sp_search(SplitPoint
*sp
, int threadID
);
232 void sp_search_pv(SplitPoint
*sp
, int threadID
);
233 void init_search_stack(SearchStack ss
[]);
234 void init_node(const Position
&pos
, SearchStack ss
[], int ply
, int threadID
);
235 void update_pv(SearchStack ss
[], int ply
);
236 void sp_update_pv(SearchStack
*pss
, SearchStack ss
[], int ply
);
237 bool connected_moves(const Position
&pos
, Move m1
, Move m2
);
238 Depth
extension(const Position
&pos
, Move m
, bool pvNode
, bool check
,
239 bool singleReply
, bool mateThreat
);
240 bool ok_to_do_nullmove(const Position
&pos
);
241 bool ok_to_prune(const Position
&pos
, Move m
, Move threat
, Depth d
);
242 bool ok_to_use_TT(const TTEntry
* tte
, Depth depth
, Value beta
, int ply
);
243 bool ok_to_history(const Position
&pos
, Move m
);
244 void update_history(const Position
& pos
, Move m
, Depth depth
,
245 Move movesSearched
[], int moveCount
);
247 bool fail_high_ply_1();
248 int current_search_time();
252 void print_current_line(SearchStack ss
[], int ply
, int threadID
);
253 void wait_for_stop_or_ponderhit();
255 void idle_loop(int threadID
, SplitPoint
*waitSp
);
256 void init_split_point_stack();
257 void destroy_split_point_stack();
258 bool thread_should_stop(int threadID
);
259 bool thread_is_available(int slave
, int master
);
260 bool idle_thread_exists(int master
);
261 bool split(const Position
&pos
, SearchStack
*ss
, int ply
,
262 Value
*alpha
, Value
*beta
, Value
*bestValue
, Depth depth
,
263 int *moves
, MovePicker
*mp
, Bitboard dcCandidates
, int master
,
265 void wake_sleeping_threads();
267 #if !defined(_MSC_VER)
268 void *init_thread(void *threadID
);
270 DWORD WINAPI
init_thread(LPVOID threadID
);
277 //// Global variables
280 // The main transposition table
281 TranspositionTable TT
= TranspositionTable(TTDefaultSize
);
284 // Number of active threads:
285 int ActiveThreads
= 1;
287 // Locks. In principle, there is no need for IOLock to be a global variable,
288 // but it could turn out to be useful for debugging.
291 History H
; // Should be made local?
298 /// think() is the external interface to Glaurung's search, and is called when
299 /// the program receives the UCI 'go' command. It initializes various
300 /// search-related global variables, and calls root_search()
302 void think(const Position
&pos
, bool infinite
, bool ponder
, int side_to_move
,
303 int time
[], int increment
[], int movesToGo
, int maxDepth
,
304 int maxNodes
, int maxTime
, Move searchMoves
[]) {
306 // Look for a book move:
307 if(!infinite
&& !ponder
&& get_option_value_bool("OwnBook")) {
309 if(get_option_value_string("Book File") != OpeningBook
.file_name()) {
311 OpeningBook
.open("book.bin");
313 bookMove
= OpeningBook
.get_move(pos
);
314 if(bookMove
!= MOVE_NONE
) {
315 std::cout
<< "bestmove " << bookMove
<< std::endl
;
320 // Initialize global search variables:
322 SearchStartTime
= get_system_time();
323 BestRootMove
= MOVE_NONE
;
324 PonderMove
= MOVE_NONE
;
325 EasyMove
= MOVE_NONE
;
326 for(int i
= 0; i
< THREAD_MAX
; i
++) {
327 Threads
[i
].nodes
= 0ULL;
328 Threads
[i
].failHighPly1
= false;
331 InfiniteSearch
= infinite
;
332 PonderSearch
= ponder
;
333 StopOnPonderhit
= false;
338 ExactMaxTime
= maxTime
;
340 // Read UCI option values:
341 TT
.set_size(get_option_value_int("Hash"));
342 if(button_was_pressed("Clear Hash"))
344 PonderingEnabled
= get_option_value_bool("Ponder");
345 MultiPV
= get_option_value_int("MultiPV");
347 CheckExtension
[1] = Depth(get_option_value_int("Check Extension (PV nodes)"));
349 Depth(get_option_value_int("Check Extension (non-PV nodes)"));
350 SingleReplyExtension
[1] = Depth(get_option_value_int("Single Reply Extension (PV nodes)"));
351 SingleReplyExtension
[0] =
352 Depth(get_option_value_int("Single Reply Extension (non-PV nodes)"));
353 PawnPushTo7thExtension
[1] =
354 Depth(get_option_value_int("Pawn Push to 7th Extension (PV nodes)"));
355 PawnPushTo7thExtension
[0] =
356 Depth(get_option_value_int("Pawn Push to 7th Extension (non-PV nodes)"));
357 PassedPawnExtension
[1] =
358 Depth(get_option_value_int("Passed Pawn Extension (PV nodes)"));
359 PassedPawnExtension
[0] =
360 Depth(get_option_value_int("Passed Pawn Extension (non-PV nodes)"));
361 PawnEndgameExtension
[1] =
362 Depth(get_option_value_int("Pawn Endgame Extension (PV nodes)"));
363 PawnEndgameExtension
[0] =
364 Depth(get_option_value_int("Pawn Endgame Extension (non-PV nodes)"));
365 MateThreatExtension
[1] =
366 Depth(get_option_value_int("Mate Threat Extension (PV nodes)"));
367 MateThreatExtension
[0] =
368 Depth(get_option_value_int("Mate Threat Extension (non-PV nodes)"));
370 LMRPVMoves
= get_option_value_int("Full Depth Moves (PV nodes)") + 1;
371 LMRNonPVMoves
= get_option_value_int("Full Depth Moves (non-PV nodes)") + 1;
372 ThreatDepth
= get_option_value_int("Threat Depth") * OnePly
;
373 SelectiveDepth
= get_option_value_int("Selective Plies") * OnePly
;
375 Chess960
= get_option_value_bool("UCI_Chess960");
376 ShowCurrentLine
= get_option_value_bool("UCI_ShowCurrLine");
377 UseLogFile
= get_option_value_bool("Use Search Log");
379 LogFile
.open(get_option_value_string("Search Log Filename").c_str(),
380 std::ios::out
| std::ios::app
);
382 UseQSearchFutilityPruning
=
383 get_option_value_bool("Futility Pruning (Quiescence Search)");
385 get_option_value_bool("Futility Pruning (Main Search)");
388 value_from_centipawns(get_option_value_int("Futility Margin 0"));
390 value_from_centipawns(get_option_value_int("Futility Margin 1"));
392 value_from_centipawns(get_option_value_int("Futility Margin 2"));
394 RazorDepth
= (get_option_value_int("Maximum Razoring Depth") + 1) * OnePly
;
395 RazorMargin
= value_from_centipawns(get_option_value_int("Razoring Margin"));
397 MinimumSplitDepth
= get_option_value_int("Minimum Split Depth") * OnePly
;
398 MaxThreadsPerSplitPoint
=
399 get_option_value_int("Maximum Number of Threads per Split Point");
401 read_weights(pos
.side_to_move());
403 int newActiveThreads
= get_option_value_int("Threads");
404 if(newActiveThreads
!= ActiveThreads
) {
405 ActiveThreads
= newActiveThreads
;
406 init_eval(ActiveThreads
);
409 // Wake up sleeping threads:
410 wake_sleeping_threads();
412 for(int i
= 1; i
< ActiveThreads
; i
++)
413 assert(thread_is_available(i
, 0));
415 // Set thinking time:
416 int myTime
= time
[side_to_move
];
417 int myIncrement
= increment
[side_to_move
];
418 int oppTime
= time
[1 - side_to_move
];
420 TimeAdvantage
= myTime
- oppTime
;
422 if(!movesToGo
) { // Sudden death time control
424 MaxSearchTime
= myTime
/ 30 + myIncrement
;
425 AbsoluteMaxSearchTime
= Max(myTime
/ 4, myIncrement
- 100);
427 else { // Blitz game without increment
428 MaxSearchTime
= myTime
/ 40;
429 AbsoluteMaxSearchTime
= myTime
/ 8;
432 else { // (x moves) / (y minutes)
434 MaxSearchTime
= myTime
/ 2;
435 AbsoluteMaxSearchTime
= Min(myTime
/ 2, myTime
- 500);
438 MaxSearchTime
= myTime
/ Min(movesToGo
, 20);
439 AbsoluteMaxSearchTime
= Min((4 * myTime
) / movesToGo
, myTime
/ 3);
442 if(PonderingEnabled
) {
443 MaxSearchTime
+= MaxSearchTime
/ 4;
444 MaxSearchTime
= Min(MaxSearchTime
, AbsoluteMaxSearchTime
);
447 // Fixed depth or fixed number of nodes?
450 InfiniteSearch
= true; // HACK
454 NodesBetweenPolls
= Min(MaxNodes
, 30000);
455 InfiniteSearch
= true; // HACK
458 NodesBetweenPolls
= 30000;
461 // Write information to search log file:
463 LogFile
<< "Searching: " << pos
.to_fen() << '\n';
464 LogFile
<< "infinite: " << infinite
<< " ponder: " << ponder
465 << " time: " << myTime
<< " increment: " << myIncrement
466 << " moves to go: " << movesToGo
<< '\n';
469 // We're ready to start thinking. Call the iterative deepening loop
471 id_loop(pos
, searchMoves
);
487 /// init_threads() is called during startup. It launches all helper threads,
488 /// and initializes the split point stack and the global locks and condition
491 void init_threads() {
493 #if !defined(_MSC_VER)
494 pthread_t pthread
[1];
497 for(i
= 0; i
< THREAD_MAX
; i
++)
498 Threads
[i
].activeSplitPoints
= 0;
500 // Initialize global locks:
501 lock_init(&MPLock
, NULL
);
502 lock_init(&IOLock
, NULL
);
504 init_split_point_stack();
506 #if !defined(_MSC_VER)
507 pthread_mutex_init(&WaitLock
, NULL
);
508 pthread_cond_init(&WaitCond
, NULL
);
510 for(i
= 0; i
< THREAD_MAX
; i
++)
511 SitIdleEvent
[i
] = CreateEvent(0, FALSE
, FALSE
, 0);
514 // All threads except the main thread should be initialized to idle state:
515 for(i
= 1; i
< THREAD_MAX
; i
++) {
516 Threads
[i
].stop
= false;
517 Threads
[i
].workIsWaiting
= false;
518 Threads
[i
].idle
= true;
519 Threads
[i
].running
= false;
522 // Launch the helper threads:
523 for(i
= 1; i
< THREAD_MAX
; i
++) {
524 #if !defined(_MSC_VER)
525 pthread_create(pthread
, NULL
, init_thread
, (void*)(&i
));
529 CreateThread(NULL
, 0, init_thread
, (LPVOID
)(&i
), 0, iID
);
533 // Wait until the thread has finished launching:
534 while(!Threads
[i
].running
);
539 /// stop_threads() is called when the program exits. It makes all the
540 /// helper threads exit cleanly.
542 void stop_threads() {
543 ActiveThreads
= THREAD_MAX
; // HACK
544 Idle
= false; // HACK
545 wake_sleeping_threads();
546 AllThreadsShouldExit
= true;
547 for(int i
= 1; i
< THREAD_MAX
; i
++) {
548 Threads
[i
].stop
= true;
549 while(Threads
[i
].running
);
551 destroy_split_point_stack();
555 /// nodes_searched() returns the total number of nodes searched so far in
556 /// the current search.
558 int64_t nodes_searched() {
559 int64_t result
= 0ULL;
560 for(int i
= 0; i
< ActiveThreads
; i
++)
561 result
+= Threads
[i
].nodes
;
568 // id_loop() is the main iterative deepening loop. It calls root_search
569 // repeatedly with increasing depth until the allocated thinking time has
570 // been consumed, the user stops the search, or the maximum search depth is
573 void id_loop(const Position
&pos
, Move searchMoves
[]) {
575 SearchStack ss
[PLY_MAX_PLUS_2
];
577 // searchMoves are verified, copied, scored and sorted
578 RootMoveList
rml(p
, searchMoves
);
583 init_search_stack(ss
);
585 ValueByIteration
[0] = Value(0);
586 ValueByIteration
[1] = rml
.get_move_score(0);
589 EasyMove
= rml
.scan_for_easy_move();
591 // Iterative deepening loop
592 while(!AbortSearch
&& Iteration
< PLY_MAX
) {
594 // Initialize iteration
597 BestMoveChangesByIteration
[Iteration
] = 0;
601 std::cout
<< "info depth " << Iteration
<< std::endl
;
603 // Search to the current depth
604 ValueByIteration
[Iteration
] = root_search(p
, ss
, rml
);
606 // Erase the easy move if it differs from the new best move
607 if(ss
[0].pv
[0] != EasyMove
)
608 EasyMove
= MOVE_NONE
;
612 if(!InfiniteSearch
) {
614 bool stopSearch
= false;
616 // Stop search early if there is only a single legal move:
617 if(Iteration
>= 6 && rml
.move_count() == 1)
620 // Stop search early when the last two iterations returned a mate
623 && abs(ValueByIteration
[Iteration
]) >= abs(VALUE_MATE
) - 100
624 && abs(ValueByIteration
[Iteration
-1]) >= abs(VALUE_MATE
) - 100)
627 // Stop search early if one move seems to be much better than the
629 int64_t nodes
= nodes_searched();
630 if(Iteration
>= 8 && EasyMove
== ss
[0].pv
[0] &&
631 ((rml
.get_move_cumulative_nodes(0) > (nodes
* 85) / 100 &&
632 current_search_time() > MaxSearchTime
/ 16) ||
633 (rml
.get_move_cumulative_nodes(0) > (nodes
* 98) / 100 &&
634 current_search_time() > MaxSearchTime
/ 32)))
637 // Add some extra time if the best move has changed during the last
639 if(Iteration
> 5 && Iteration
<= 50)
641 BestMoveChangesByIteration
[Iteration
] * (MaxSearchTime
/ 2) +
642 BestMoveChangesByIteration
[Iteration
-1] * (MaxSearchTime
/ 3);
644 // If we need some more and we are in time advantage take it.
645 if (ExtraSearchTime
> 0 && TimeAdvantage
> 2 * MaxSearchTime
)
646 ExtraSearchTime
+= MaxSearchTime
/ 2;
648 // Stop search if most of MaxSearchTime is consumed at the end of the
649 // iteration. We probably don't have enough time to search the first
650 // move at the next iteration anyway.
651 if(current_search_time() > ((MaxSearchTime
+ ExtraSearchTime
)*80) / 128)
658 StopOnPonderhit
= true;
662 // Write PV to transposition table, in case the relevant entries have
663 // been overwritten during the search:
664 TT
.insert_pv(p
, ss
[0].pv
);
666 if(MaxDepth
&& Iteration
>= MaxDepth
)
672 // If we are pondering, we shouldn't print the best move before we
675 wait_for_stop_or_ponderhit();
677 // Print final search statistics
678 std::cout
<< "info nodes " << nodes_searched() << " nps " << nps()
679 << " time " << current_search_time()
680 << " hashfull " << TT
.full() << std::endl
;
682 // Print the best move and the ponder move to the standard output:
683 std::cout
<< "bestmove " << ss
[0].pv
[0];
684 if(ss
[0].pv
[1] != MOVE_NONE
)
685 std::cout
<< " ponder " << ss
[0].pv
[1];
686 std::cout
<< std::endl
;
690 LogFile
<< "Nodes: " << nodes_searched() << '\n';
691 LogFile
<< "Nodes/second: " << nps() << '\n';
692 LogFile
<< "Best move: " << move_to_san(p
, ss
[0].pv
[0]) << '\n';
693 p
.do_move(ss
[0].pv
[0], u
);
694 LogFile
<< "Ponder move: " << move_to_san(p
, ss
[0].pv
[1]) << '\n';
695 LogFile
<< std::endl
;
700 // root_search() is the function which searches the root node. It is
701 // similar to search_pv except that it uses a different move ordering
702 // scheme (perhaps we should try to use this at internal PV nodes, too?)
703 // and prints some information to the standard output.
705 Value
root_search(Position
&pos
, SearchStack ss
[], RootMoveList
&rml
) {
706 Value alpha
= -VALUE_INFINITE
, beta
= VALUE_INFINITE
, value
;
707 Bitboard dcCandidates
= pos
.discovered_check_candidates(pos
.side_to_move());
709 // Loop through all the moves in the root move list:
710 for(int i
= 0; i
< rml
.move_count() && !AbortSearch
; i
++) {
716 RootMoveNumber
= i
+ 1;
719 // Remember the node count before the move is searched. The node counts
720 // are used to sort the root moves at the next iteration.
721 nodes
= nodes_searched();
723 // Pick the next root move, and print the move and the move number to
724 // the standard output:
725 move
= ss
[0].currentMove
= rml
.get_move(i
);
726 if(current_search_time() >= 1000)
727 std::cout
<< "info currmove " << move
728 << " currmovenumber " << i
+ 1 << std::endl
;
730 // Decide search depth for this move:
731 ext
= extension(pos
, move
, true, pos
.move_is_check(move
), false, false);
732 newDepth
= (Iteration
-2)*OnePly
+ ext
+ InitialDepth
;
734 // Make the move, and search it.
735 pos
.do_move(move
, u
, dcCandidates
);
738 value
= -search_pv(pos
, ss
, -beta
, VALUE_INFINITE
, newDepth
, 1, 0);
739 // If the value has dropped a lot compared to the last iteration,
740 // set the boolean variable Problem to true. This variable is used
741 // for time managment: When Problem is true, we try to complete the
742 // current iteration before playing a move.
743 Problem
= (Iteration
>= 2 &&
744 value
<= ValueByIteration
[Iteration
-1] - ProblemMargin
);
745 if(Problem
&& StopOnPonderhit
)
746 StopOnPonderhit
= false;
749 value
= -search(pos
, ss
, -alpha
, newDepth
, 1, true, 0);
751 // Fail high! Set the boolean variable FailHigh to true, and
752 // re-search the move with a big window. The variable FailHigh is
753 // used for time managment: We try to avoid aborting the search
754 // prematurely during a fail high research.
756 value
= -search_pv(pos
, ss
, -beta
, -alpha
, newDepth
, 1, 0);
760 pos
.undo_move(move
, u
);
762 // Finished searching the move. If AbortSearch is true, the search
763 // was aborted because the user interrupted the search or because we
764 // ran out of time. In this case, the return value of the search cannot
765 // be trusted, and we break out of the loop without updating the best
770 // Remember the node count for this move. The node counts are used to
771 // sort the root moves at the next iteration.
772 rml
.set_move_nodes(i
, nodes_searched() - nodes
);
774 assert(value
>= -VALUE_INFINITE
&& value
<= VALUE_INFINITE
);
776 if(value
<= alpha
&& i
>= MultiPV
)
777 rml
.set_move_score(i
, -VALUE_INFINITE
);
782 rml
.set_move_score(i
, value
);
784 rml
.set_move_pv(i
, ss
[0].pv
);
787 // We record how often the best move has been changed in each
788 // iteration. This information is used for time managment: When
789 // the best move changes frequently, we allocate some more time.
791 BestMoveChangesByIteration
[Iteration
]++;
793 // Print search information to the standard output:
794 std::cout
<< "info depth " << Iteration
795 << " score " << value_to_string(value
)
796 << " time " << current_search_time()
797 << " nodes " << nodes_searched()
800 for(int j
= 0; ss
[0].pv
[j
] != MOVE_NONE
&& j
< PLY_MAX
; j
++)
801 std::cout
<< ss
[0].pv
[j
] << " ";
802 std::cout
<< std::endl
;
805 LogFile
<< pretty_pv(pos
, current_search_time(), Iteration
,
806 nodes_searched(), value
, ss
[0].pv
)
811 // Reset the global variable Problem to false if the value isn't too
812 // far below the final value from the last iteration.
813 if(value
> ValueByIteration
[Iteration
- 1] - NoProblemMargin
)
816 else { // MultiPV > 1
818 for(int j
= 0; j
< Min(MultiPV
, rml
.move_count()); j
++) {
820 std::cout
<< "info multipv " << j
+ 1
821 << " score " << value_to_string(rml
.get_move_score(j
))
822 << " depth " << ((j
<= i
)? Iteration
: Iteration
- 1)
823 << " time " << current_search_time()
824 << " nodes " << nodes_searched()
827 for(k
= 0; rml
.get_move_pv(j
, k
) != MOVE_NONE
&& k
< PLY_MAX
; k
++)
828 std::cout
<< rml
.get_move_pv(j
, k
) << " ";
829 std::cout
<< std::endl
;
831 alpha
= rml
.get_move_score(Min(i
, MultiPV
-1));
839 // search_pv() is the main search function for PV nodes.
841 Value
search_pv(Position
&pos
, SearchStack ss
[], Value alpha
, Value beta
,
842 Depth depth
, int ply
, int threadID
) {
844 assert(alpha
>= -VALUE_INFINITE
&& alpha
<= VALUE_INFINITE
);
845 assert(beta
> alpha
&& beta
<= VALUE_INFINITE
);
846 assert(ply
>= 0 && ply
< PLY_MAX
);
847 assert(threadID
>= 0 && threadID
< ActiveThreads
);
851 // Initialize, and make an early exit in case of an aborted search,
852 // an instant draw, maximum ply reached, etc.
853 Value oldAlpha
= alpha
;
855 if (AbortSearch
|| thread_should_stop(threadID
))
859 return qsearch(pos
, ss
, alpha
, beta
, Depth(0), ply
, threadID
);
861 init_node(pos
, ss
, ply
, threadID
);
866 if (ply
>= PLY_MAX
- 1)
867 return evaluate(pos
, ei
, threadID
);
869 // Mate distance pruning
870 alpha
= Max(value_mated_in(ply
), alpha
);
871 beta
= Min(value_mate_in(ply
+1), beta
);
875 // Transposition table lookup. At PV nodes, we don't use the TT for
876 // pruning, but only for move ordering.
877 const TTEntry
* tte
= TT
.retrieve(pos
);
879 Move ttMove
= (tte
? tte
->move() : MOVE_NONE
);
881 // Go with internal iterative deepening if we don't have a TT move
882 if (UseIIDAtPVNodes
&& ttMove
== MOVE_NONE
&& depth
>= 5*OnePly
)
884 search_pv(pos
, ss
, alpha
, beta
, depth
-2*OnePly
, ply
, threadID
);
885 ttMove
= ss
[ply
].pv
[ply
];
888 // Initialize a MovePicker object for the current position, and prepare
889 // to search all moves:
890 MovePicker mp
= MovePicker(pos
, true, ttMove
, ss
[ply
].mateKiller
,
891 ss
[ply
].killer1
, ss
[ply
].killer2
, depth
);
893 Move move
, movesSearched
[256];
895 Value value
, bestValue
= -VALUE_INFINITE
;
896 Bitboard dcCandidates
= mp
.discovered_check_candidates();
897 bool mateThreat
= MateThreatExtension
[1] > Depth(0)
898 && pos
.has_mate_threat(opposite_color(pos
.side_to_move()));
900 // Loop through all legal moves until no moves remain or a beta cutoff
903 && (move
= mp
.get_next_move()) != MOVE_NONE
904 && !thread_should_stop(threadID
))
906 assert(move_is_ok(move
));
908 bool singleReply
= (pos
.is_check() && mp
.number_of_moves() == 1);
909 bool moveIsCheck
= pos
.move_is_check(move
, dcCandidates
);
910 bool moveIsCapture
= pos
.move_is_capture(move
);
911 bool moveIsPassedPawnPush
= pos
.move_is_passed_pawn_push(move
);
913 movesSearched
[moveCount
++] = ss
[ply
].currentMove
= move
;
915 ss
[ply
].currentMoveCaptureValue
= move_is_ep(move
) ?
916 PawnValueMidgame
: pos
.midgame_value_of_piece_on(move_to(move
));
918 // Decide the new search depth
919 Depth ext
= extension(pos
, move
, true, moveIsCheck
, singleReply
, mateThreat
);
920 Depth newDepth
= depth
- OnePly
+ ext
;
922 // Make and search the move
924 pos
.do_move(move
, u
, dcCandidates
);
926 if (moveCount
== 1) // The first move in list is the PV
927 value
= -search_pv(pos
, ss
, -beta
, -alpha
, newDepth
, ply
+1, threadID
);
930 // Try to reduce non-pv search depth by one ply if move seems not problematic,
931 // if the move fails high will be re-searched at full depth.
932 if ( depth
>= 2*OnePly
934 && moveCount
>= LMRPVMoves
936 && !move_promotion(move
)
937 && !moveIsPassedPawnPush
938 && !move_is_castle(move
)
939 && move
!= ss
[ply
].killer1
940 && move
!= ss
[ply
].killer2
)
942 ss
[ply
].reduction
= OnePly
;
943 value
= -search(pos
, ss
, -alpha
, newDepth
-OnePly
, ply
+1, true, threadID
);
946 value
= alpha
+ 1; // Just to trigger next condition
948 if (value
> alpha
) // Go with full depth pv search
950 ss
[ply
].reduction
= Depth(0);
951 value
= -search(pos
, ss
, -alpha
, newDepth
, ply
+1, true, threadID
);
952 if (value
> alpha
&& value
< beta
)
954 // When the search fails high at ply 1 while searching the first
955 // move at the root, set the flag failHighPly1. This is used for
956 // time managment: We don't want to stop the search early in
957 // such cases, because resolving the fail high at ply 1 could
958 // result in a big drop in score at the root.
959 if (ply
== 1 && RootMoveNumber
== 1)
960 Threads
[threadID
].failHighPly1
= true;
962 // A fail high occurred. Re-search at full window (pv search)
963 value
= -search_pv(pos
, ss
, -beta
, -alpha
, newDepth
, ply
+1, threadID
);
964 Threads
[threadID
].failHighPly1
= false;
968 pos
.undo_move(move
, u
);
970 assert(value
> -VALUE_INFINITE
&& value
< VALUE_INFINITE
);
973 if (value
> bestValue
)
980 if (value
== value_mate_in(ply
+ 1))
981 ss
[ply
].mateKiller
= move
;
983 // If we are at ply 1, and we are searching the first root move at
984 // ply 0, set the 'Problem' variable if the score has dropped a lot
985 // (from the computer's point of view) since the previous iteration:
986 if (Iteration
>= 2 && -value
<= ValueByIteration
[Iteration
-1] - ProblemMargin
)
991 if ( ActiveThreads
> 1
993 && depth
>= MinimumSplitDepth
995 && idle_thread_exists(threadID
)
997 && !thread_should_stop(threadID
)
998 && split(pos
, ss
, ply
, &alpha
, &beta
, &bestValue
, depth
,
999 &moveCount
, &mp
, dcCandidates
, threadID
, true))
1003 // All legal moves have been searched. A special case: If there were
1004 // no legal moves, it must be mate or stalemate:
1006 return (pos
.is_check() ? value_mated_in(ply
) : VALUE_DRAW
);
1008 // If the search is not aborted, update the transposition table,
1009 // history counters, and killer moves.
1010 if (AbortSearch
|| thread_should_stop(threadID
))
1013 if (bestValue
<= oldAlpha
)
1014 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, MOVE_NONE
, VALUE_TYPE_UPPER
);
1016 else if (bestValue
>= beta
)
1018 Move m
= ss
[ply
].pv
[ply
];
1019 if (ok_to_history(pos
, m
)) // Only non capture moves are considered
1021 update_history(pos
, m
, depth
, movesSearched
, moveCount
);
1022 if (m
!= ss
[ply
].killer1
)
1024 ss
[ply
].killer2
= ss
[ply
].killer1
;
1025 ss
[ply
].killer1
= m
;
1028 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, m
, VALUE_TYPE_LOWER
);
1031 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, ss
[ply
].pv
[ply
], VALUE_TYPE_EXACT
);
1037 // search() is the search function for zero-width nodes.
1039 Value
search(Position
&pos
, SearchStack ss
[], Value beta
, Depth depth
,
1040 int ply
, bool allowNullmove
, int threadID
) {
1042 assert(beta
>= -VALUE_INFINITE
&& beta
<= VALUE_INFINITE
);
1043 assert(ply
>= 0 && ply
< PLY_MAX
);
1044 assert(threadID
>= 0 && threadID
< ActiveThreads
);
1048 // Initialize, and make an early exit in case of an aborted search,
1049 // an instant draw, maximum ply reached, etc.
1050 if (AbortSearch
|| thread_should_stop(threadID
))
1054 return qsearch(pos
, ss
, beta
-1, beta
, Depth(0), ply
, threadID
);
1056 init_node(pos
, ss
, ply
, threadID
);
1061 if (ply
>= PLY_MAX
- 1)
1062 return evaluate(pos
, ei
, threadID
);
1064 // Mate distance pruning
1065 if (value_mated_in(ply
) >= beta
)
1068 if (value_mate_in(ply
+ 1) < beta
)
1071 // Transposition table lookup
1072 const TTEntry
* tte
= TT
.retrieve(pos
);
1074 Move ttMove
= (tte
? tte
->move() : MOVE_NONE
);
1076 if (tte
&& ok_to_use_TT(tte
, depth
, beta
, ply
))
1078 ss
[ply
].currentMove
= ttMove
; // can be MOVE_NONE ?
1079 return value_from_tt(tte
->value(), ply
);
1082 Value approximateEval
= quick_evaluate(pos
);
1083 bool mateThreat
= false;
1088 && ok_to_do_nullmove(pos
)
1089 && approximateEval
>= beta
- NullMoveMargin
)
1091 ss
[ply
].currentMove
= MOVE_NULL
;
1094 pos
.do_null_move(u
);
1095 Value nullValue
= -search(pos
, ss
, -(beta
-1), depth
-4*OnePly
, ply
+1, false, threadID
);
1096 pos
.undo_null_move(u
);
1098 if (nullValue
>= beta
)
1100 if (depth
< 6 * OnePly
)
1103 // Do zugzwang verification search
1104 Value v
= search(pos
, ss
, beta
, depth
-5*OnePly
, ply
, false, threadID
);
1108 // The null move failed low, which means that we may be faced with
1109 // some kind of threat. If the previous move was reduced, check if
1110 // the move that refuted the null move was somehow connected to the
1111 // move which was reduced. If a connection is found, return a fail
1112 // low score (which will cause the reduced move to fail high in the
1113 // parent node, which will trigger a re-search with full depth).
1114 if (nullValue
== value_mated_in(ply
+ 2))
1117 ss
[ply
].threatMove
= ss
[ply
+ 1].currentMove
;
1118 if ( depth
< ThreatDepth
1119 && ss
[ply
- 1].reduction
1120 && connected_moves(pos
, ss
[ply
- 1].currentMove
, ss
[ply
].threatMove
))
1124 // Null move search not allowed, try razoring
1125 else if (depth
< RazorDepth
&& approximateEval
< beta
- RazorMargin
)
1127 Value v
= qsearch(pos
, ss
, beta
-1, beta
, Depth(0), ply
, threadID
);
1132 // Go with internal iterative deepening if we don't have a TT move
1133 if (UseIIDAtNonPVNodes
&& ttMove
== MOVE_NONE
&& depth
>= 8*OnePly
&&
1134 evaluate(pos
, ei
, threadID
) >= beta
- IIDMargin
)
1136 search(pos
, ss
, beta
, Min(depth
/2, depth
-2*OnePly
), ply
, false, threadID
);
1137 ttMove
= ss
[ply
].pv
[ply
];
1140 // Initialize a MovePicker object for the current position, and prepare
1141 // to search all moves:
1142 MovePicker mp
= MovePicker(pos
, false, ttMove
, ss
[ply
].mateKiller
,
1143 ss
[ply
].killer1
, ss
[ply
].killer2
, depth
);
1145 Move move
, movesSearched
[256];
1147 Value value
, bestValue
= -VALUE_INFINITE
;
1148 Bitboard dcCandidates
= mp
.discovered_check_candidates();
1149 Value futilityValue
= VALUE_NONE
;
1150 bool isCheck
= pos
.is_check();
1151 bool useFutilityPruning
= UseFutilityPruning
1152 && depth
< SelectiveDepth
1155 // Loop through all legal moves until no moves remain or a beta cutoff
1157 while ( bestValue
< beta
1158 && (move
= mp
.get_next_move()) != MOVE_NONE
1159 && !thread_should_stop(threadID
))
1161 assert(move_is_ok(move
));
1163 bool singleReply
= (isCheck
&& mp
.number_of_moves() == 1);
1164 bool moveIsCheck
= pos
.move_is_check(move
, dcCandidates
);
1165 bool moveIsCapture
= pos
.move_is_capture(move
);
1166 bool moveIsPassedPawnPush
= pos
.move_is_passed_pawn_push(move
);
1168 movesSearched
[moveCount
++] = ss
[ply
].currentMove
= move
;
1170 // Decide the new search depth
1171 Depth ext
= extension(pos
, move
, false, moveIsCheck
, singleReply
, mateThreat
);
1172 Depth newDepth
= depth
- OnePly
+ ext
;
1175 if ( useFutilityPruning
1178 && !moveIsPassedPawnPush
1179 && !move_promotion(move
))
1181 if ( moveCount
>= 2 + int(depth
)
1182 && ok_to_prune(pos
, move
, ss
[ply
].threatMove
, depth
))
1185 if (depth
< 3 * OnePly
&& approximateEval
< beta
)
1187 if (futilityValue
== VALUE_NONE
)
1188 futilityValue
= evaluate(pos
, ei
, threadID
)
1189 + (depth
< 2 * OnePly
? FutilityMargin1
: FutilityMargin2
);
1191 if (futilityValue
< beta
)
1193 if (futilityValue
> bestValue
)
1194 bestValue
= futilityValue
;
1200 // Make and search the move
1202 pos
.do_move(move
, u
, dcCandidates
);
1204 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1205 // if the move fails high will be re-searched at full depth.
1206 if ( depth
>= 2*OnePly
1208 && moveCount
>= LMRNonPVMoves
1210 && !move_promotion(move
)
1211 && !moveIsPassedPawnPush
1212 && !move_is_castle(move
)
1213 && move
!= ss
[ply
].killer1
1214 && move
!= ss
[ply
].killer2
)
1216 ss
[ply
].reduction
= OnePly
;
1217 value
= -search(pos
, ss
, -(beta
-1), newDepth
-OnePly
, ply
+1, true, threadID
);
1220 value
= beta
; // Just to trigger next condition
1222 if (value
>= beta
) // Go with full depth non-pv search
1224 ss
[ply
].reduction
= Depth(0);
1225 value
= -search(pos
, ss
, -(beta
-1), newDepth
, ply
+1, true, threadID
);
1227 pos
.undo_move(move
, u
);
1229 assert(value
> -VALUE_INFINITE
&& value
< VALUE_INFINITE
);
1232 if (value
> bestValue
)
1238 if (value
== value_mate_in(ply
+ 1))
1239 ss
[ply
].mateKiller
= move
;
1243 if ( ActiveThreads
> 1
1245 && depth
>= MinimumSplitDepth
1247 && idle_thread_exists(threadID
)
1249 && !thread_should_stop(threadID
)
1250 && split(pos
, ss
, ply
, &beta
, &beta
, &bestValue
, depth
, &moveCount
,
1251 &mp
, dcCandidates
, threadID
, false))
1255 // All legal moves have been searched. A special case: If there were
1256 // no legal moves, it must be mate or stalemate:
1258 return (pos
.is_check() ? value_mated_in(ply
) : VALUE_DRAW
);
1260 // If the search is not aborted, update the transposition table,
1261 // history counters, and killer moves.
1262 if (AbortSearch
|| thread_should_stop(threadID
))
1265 if (bestValue
< beta
)
1266 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, MOVE_NONE
, VALUE_TYPE_UPPER
);
1269 Move m
= ss
[ply
].pv
[ply
];
1270 if (ok_to_history(pos
, m
)) // Only non capture moves are considered
1272 update_history(pos
, m
, depth
, movesSearched
, moveCount
);
1273 if (m
!= ss
[ply
].killer1
)
1275 ss
[ply
].killer2
= ss
[ply
].killer1
;
1276 ss
[ply
].killer1
= m
;
1279 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, m
, VALUE_TYPE_LOWER
);
1285 // qsearch() is the quiescence search function, which is called by the main
1286 // search function when the remaining depth is zero (or, to be more precise,
1287 // less than OnePly).
1289 Value
qsearch(Position
&pos
, SearchStack ss
[], Value alpha
, Value beta
,
1290 Depth depth
, int ply
, int threadID
) {
1292 assert(alpha
>= -VALUE_INFINITE
&& alpha
<= VALUE_INFINITE
);
1293 assert(beta
>= -VALUE_INFINITE
&& beta
<= VALUE_INFINITE
);
1295 assert(ply
>= 0 && ply
< PLY_MAX
);
1296 assert(threadID
>= 0 && threadID
< ActiveThreads
);
1300 // Initialize, and make an early exit in case of an aborted search,
1301 // an instant draw, maximum ply reached, etc.
1302 if (AbortSearch
|| thread_should_stop(threadID
))
1305 init_node(pos
, ss
, ply
, threadID
);
1310 // Transposition table lookup
1311 const TTEntry
* tte
= TT
.retrieve(pos
);
1312 if (tte
&& ok_to_use_TT(tte
, depth
, beta
, ply
))
1313 return value_from_tt(tte
->value(), ply
);
1315 // Evaluate the position statically:
1316 Value staticValue
= evaluate(pos
, ei
, threadID
);
1318 if (ply
== PLY_MAX
- 1)
1321 // Initialize "stand pat score", and return it immediately if it is
1323 Value bestValue
= (pos
.is_check() ? -VALUE_INFINITE
: staticValue
);
1325 if (bestValue
>= beta
)
1328 if (bestValue
> alpha
)
1331 // Initialize a MovePicker object for the current position, and prepare
1332 // to search the moves. Because the depth is <= 0 here, only captures,
1333 // queen promotions and checks (only if depth == 0) will be generated.
1334 MovePicker mp
= MovePicker(pos
, false, MOVE_NONE
, MOVE_NONE
, MOVE_NONE
,
1338 Bitboard dcCandidates
= mp
.discovered_check_candidates();
1339 bool isCheck
= pos
.is_check();
1341 // Loop through the moves until no moves remain or a beta cutoff
1343 while ( alpha
< beta
1344 && (move
= mp
.get_next_move()) != MOVE_NONE
)
1346 assert(move_is_ok(move
));
1348 bool moveIsCheck
= pos
.move_is_check(move
, dcCandidates
);
1349 bool moveIsPassedPawnPush
= pos
.move_is_passed_pawn_push(move
);
1352 ss
[ply
].currentMove
= move
;
1355 if ( UseQSearchFutilityPruning
1358 && !move_promotion(move
)
1359 && !moveIsPassedPawnPush
1360 && beta
- alpha
== 1
1361 && pos
.non_pawn_material(pos
.side_to_move()) > RookValueMidgame
)
1363 Value futilityValue
= staticValue
1364 + Max(pos
.midgame_value_of_piece_on(move_to(move
)),
1365 pos
.endgame_value_of_piece_on(move_to(move
)))
1367 + ei
.futilityMargin
;
1369 if (futilityValue
< alpha
)
1371 if (futilityValue
> bestValue
)
1372 bestValue
= futilityValue
;
1377 // Don't search captures and checks with negative SEE values.
1379 && !move_promotion(move
)
1380 && (pos
.midgame_value_of_piece_on(move_from(move
)) >
1381 pos
.midgame_value_of_piece_on(move_to(move
)))
1382 && pos
.see(move
) < 0)
1385 // Make and search the move.
1387 pos
.do_move(move
, u
, dcCandidates
);
1388 Value value
= -qsearch(pos
, ss
, -beta
, -alpha
, depth
-OnePly
, ply
+1, threadID
);
1389 pos
.undo_move(move
, u
);
1391 assert(value
> -VALUE_INFINITE
&& value
< VALUE_INFINITE
);
1394 if (value
> bestValue
)
1405 // All legal moves have been searched. A special case: If we're in check
1406 // and no legal moves were found, it is checkmate:
1407 if (pos
.is_check() && moveCount
== 0) // Mate!
1408 return value_mated_in(ply
);
1410 assert(bestValue
> -VALUE_INFINITE
&& bestValue
< VALUE_INFINITE
);
1412 // Update transposition table
1413 TT
.store(pos
, value_to_tt(bestValue
, ply
), depth
, MOVE_NONE
, VALUE_TYPE_EXACT
);
1419 // sp_search() is used to search from a split point. This function is called
1420 // by each thread working at the split point. It is similar to the normal
1421 // search() function, but simpler. Because we have already probed the hash
1422 // table, done a null move search, and searched the first move before
1423 // splitting, we don't have to repeat all this work in sp_search(). We
1424 // also don't need to store anything to the hash table here: This is taken
1425 // care of after we return from the split point.
1427 void sp_search(SplitPoint
*sp
, int threadID
) {
1429 assert(threadID
>= 0 && threadID
< ActiveThreads
);
1430 assert(ActiveThreads
> 1);
1432 Position pos
= Position(sp
->pos
);
1433 SearchStack
*ss
= sp
->sstack
[threadID
];
1436 bool isCheck
= pos
.is_check();
1437 bool useFutilityPruning
= UseFutilityPruning
1438 && sp
->depth
< SelectiveDepth
1441 while ( sp
->bestValue
< sp
->beta
1442 && !thread_should_stop(threadID
)
1443 && (move
= sp
->mp
->get_next_move(sp
->lock
)) != MOVE_NONE
)
1445 assert(move_is_ok(move
));
1447 bool moveIsCheck
= pos
.move_is_check(move
, sp
->dcCandidates
);
1448 bool moveIsCapture
= pos
.move_is_capture(move
);
1449 bool moveIsPassedPawnPush
= pos
.move_is_passed_pawn_push(move
);
1451 lock_grab(&(sp
->lock
));
1452 int moveCount
= ++sp
->moves
;
1453 lock_release(&(sp
->lock
));
1455 ss
[sp
->ply
].currentMove
= move
;
1457 // Decide the new search depth.
1458 Depth ext
= extension(pos
, move
, false, moveIsCheck
, false, false);
1459 Depth newDepth
= sp
->depth
- OnePly
+ ext
;
1462 if ( useFutilityPruning
1465 && !moveIsPassedPawnPush
1466 && !move_promotion(move
)
1467 && moveCount
>= 2 + int(sp
->depth
)
1468 && ok_to_prune(pos
, move
, ss
[sp
->ply
].threatMove
, sp
->depth
))
1471 // Make and search the move.
1473 pos
.do_move(move
, u
, sp
->dcCandidates
);
1475 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1476 // if the move fails high will be re-searched at full depth.
1477 if ( ext
== Depth(0)
1478 && moveCount
>= LMRNonPVMoves
1480 && !moveIsPassedPawnPush
1481 && !move_promotion(move
)
1482 && !move_is_castle(move
)
1483 && move
!= ss
[sp
->ply
].killer1
1484 && move
!= ss
[sp
->ply
].killer2
)
1486 ss
[sp
->ply
].reduction
= OnePly
;
1487 value
= -search(pos
, ss
, -(sp
->beta
-1), newDepth
- OnePly
, sp
->ply
+1, true, threadID
);
1490 value
= sp
->beta
; // Just to trigger next condition
1492 if (value
>= sp
->beta
) // Go with full depth non-pv search
1494 ss
[sp
->ply
].reduction
= Depth(0);
1495 value
= -search(pos
, ss
, -(sp
->beta
- 1), newDepth
, sp
->ply
+1, true, threadID
);
1497 pos
.undo_move(move
, u
);
1499 assert(value
> -VALUE_INFINITE
&& value
< VALUE_INFINITE
);
1501 if (thread_should_stop(threadID
))
1505 lock_grab(&(sp
->lock
));
1506 if (value
> sp
->bestValue
&& !thread_should_stop(threadID
))
1508 sp
->bestValue
= value
;
1509 if (sp
->bestValue
>= sp
->beta
)
1511 sp_update_pv(sp
->parentSstack
, ss
, sp
->ply
);
1512 for (int i
= 0; i
< ActiveThreads
; i
++)
1513 if (i
!= threadID
&& (i
== sp
->master
|| sp
->slaves
[i
]))
1514 Threads
[i
].stop
= true;
1516 sp
->finished
= true;
1519 lock_release(&(sp
->lock
));
1522 lock_grab(&(sp
->lock
));
1524 // If this is the master thread and we have been asked to stop because of
1525 // a beta cutoff higher up in the tree, stop all slave threads:
1526 if (sp
->master
== threadID
&& thread_should_stop(threadID
))
1527 for (int i
= 0; i
< ActiveThreads
; i
++)
1529 Threads
[i
].stop
= true;
1532 sp
->slaves
[threadID
] = 0;
1534 lock_release(&(sp
->lock
));
1538 // sp_search_pv() is used to search from a PV split point. This function
1539 // is called by each thread working at the split point. It is similar to
1540 // the normal search_pv() function, but simpler. Because we have already
1541 // probed the hash table and searched the first move before splitting, we
1542 // don't have to repeat all this work in sp_search_pv(). We also don't
1543 // need to store anything to the hash table here: This is taken care of
1544 // after we return from the split point.
1546 void sp_search_pv(SplitPoint
*sp
, int threadID
) {
1548 assert(threadID
>= 0 && threadID
< ActiveThreads
);
1549 assert(ActiveThreads
> 1);
1551 Position pos
= Position(sp
->pos
);
1552 SearchStack
*ss
= sp
->sstack
[threadID
];
1556 while ( sp
->alpha
< sp
->beta
1557 && !thread_should_stop(threadID
)
1558 && (move
= sp
->mp
->get_next_move(sp
->lock
)) != MOVE_NONE
)
1560 bool moveIsCheck
= pos
.move_is_check(move
, sp
->dcCandidates
);
1561 bool moveIsCapture
= pos
.move_is_capture(move
);
1562 bool moveIsPassedPawnPush
= pos
.move_is_passed_pawn_push(move
);
1564 assert(move_is_ok(move
));
1566 ss
[sp
->ply
].currentMoveCaptureValue
= move_is_ep(move
)?
1567 PawnValueMidgame
: pos
.midgame_value_of_piece_on(move_to(move
));
1569 lock_grab(&(sp
->lock
));
1570 int moveCount
= ++sp
->moves
;
1571 lock_release(&(sp
->lock
));
1573 ss
[sp
->ply
].currentMove
= move
;
1575 // Decide the new search depth.
1576 Depth ext
= extension(pos
, move
, true, moveIsCheck
, false, false);
1577 Depth newDepth
= sp
->depth
- OnePly
+ ext
;
1579 // Make and search the move.
1581 pos
.do_move(move
, u
, sp
->dcCandidates
);
1583 // Try to reduce non-pv search depth by one ply if move seems not problematic,
1584 // if the move fails high will be re-searched at full depth.
1585 if ( ext
== Depth(0)
1586 && moveCount
>= LMRPVMoves
1588 && !moveIsPassedPawnPush
1589 && !move_promotion(move
)
1590 && !move_is_castle(move
)
1591 && move
!= ss
[sp
->ply
].killer1
1592 && move
!= ss
[sp
->ply
].killer2
)
1594 ss
[sp
->ply
].reduction
= OnePly
;
1595 value
= -search(pos
, ss
, -sp
->alpha
, newDepth
- OnePly
, sp
->ply
+1, true, threadID
);
1598 value
= sp
->alpha
+ 1; // Just to trigger next condition
1600 if (value
> sp
->alpha
) // Go with full depth non-pv search
1602 ss
[sp
->ply
].reduction
= Depth(0);
1603 value
= -search(pos
, ss
, -sp
->alpha
, newDepth
, sp
->ply
+1, true, threadID
);
1605 if (value
> sp
->alpha
&& value
< sp
->beta
)
1607 // When the search fails high at ply 1 while searching the first
1608 // move at the root, set the flag failHighPly1. This is used for
1609 // time managment: We don't want to stop the search early in
1610 // such cases, because resolving the fail high at ply 1 could
1611 // result in a big drop in score at the root.
1612 if (sp
->ply
== 1 && RootMoveNumber
== 1)
1613 Threads
[threadID
].failHighPly1
= true;
1615 value
= -search_pv(pos
, ss
, -sp
->beta
, -sp
->alpha
, newDepth
, sp
->ply
+1, threadID
);
1616 Threads
[threadID
].failHighPly1
= false;
1619 pos
.undo_move(move
, u
);
1621 assert(value
> -VALUE_INFINITE
&& value
< VALUE_INFINITE
);
1623 if (thread_should_stop(threadID
))
1627 lock_grab(&(sp
->lock
));
1628 if (value
> sp
->bestValue
&& !thread_should_stop(threadID
))
1630 sp
->bestValue
= value
;
1631 if (value
> sp
->alpha
)
1634 sp_update_pv(sp
->parentSstack
, ss
, sp
->ply
);
1635 if (value
== value_mate_in(sp
->ply
+ 1))
1636 ss
[sp
->ply
].mateKiller
= move
;
1638 if(value
>= sp
->beta
)
1640 for(int i
= 0; i
< ActiveThreads
; i
++)
1641 if(i
!= threadID
&& (i
== sp
->master
|| sp
->slaves
[i
]))
1642 Threads
[i
].stop
= true;
1644 sp
->finished
= true;
1647 // If we are at ply 1, and we are searching the first root move at
1648 // ply 0, set the 'Problem' variable if the score has dropped a lot
1649 // (from the computer's point of view) since the previous iteration:
1650 if (Iteration
>= 2 && -value
<= ValueByIteration
[Iteration
-1] - ProblemMargin
)
1653 lock_release(&(sp
->lock
));
1656 lock_grab(&(sp
->lock
));
1658 // If this is the master thread and we have been asked to stop because of
1659 // a beta cutoff higher up in the tree, stop all slave threads:
1660 if (sp
->master
== threadID
&& thread_should_stop(threadID
))
1661 for (int i
= 0; i
< ActiveThreads
; i
++)
1663 Threads
[i
].stop
= true;
1666 sp
->slaves
[threadID
] = 0;
1668 lock_release(&(sp
->lock
));
1672 /// The RootMove class
1676 RootMove::RootMove() {
1677 nodes
= cumulativeNodes
= 0ULL;
1680 // RootMove::operator<() is the comparison function used when
1681 // sorting the moves. A move m1 is considered to be better
1682 // than a move m2 if it has a higher score, or if the moves
1683 // have equal score but m1 has the higher node count.
1685 bool RootMove::operator<(const RootMove
& m
) {
1687 if (score
!= m
.score
)
1688 return (score
< m
.score
);
1690 return nodes
<= m
.nodes
;
1693 /// The RootMoveList class
1697 RootMoveList::RootMoveList(Position
& pos
, Move searchMoves
[]) : count(0) {
1699 MoveStack mlist
[MaxRootMoves
];
1700 bool includeAllMoves
= (searchMoves
[0] == MOVE_NONE
);
1702 // Generate all legal moves
1703 int lm_count
= generate_legal_moves(pos
, mlist
);
1705 // Add each move to the moves[] array
1706 for (int i
= 0; i
< lm_count
; i
++)
1708 bool includeMove
= includeAllMoves
;
1710 for (int k
= 0; !includeMove
&& searchMoves
[k
] != MOVE_NONE
; k
++)
1711 includeMove
= (searchMoves
[k
] == mlist
[i
].move
);
1715 // Find a quick score for the move
1717 SearchStack ss
[PLY_MAX_PLUS_2
];
1719 moves
[count
].move
= mlist
[i
].move
;
1720 moves
[count
].nodes
= 0ULL;
1721 pos
.do_move(moves
[count
].move
, u
);
1722 moves
[count
].score
= -qsearch(pos
, ss
, -VALUE_INFINITE
, VALUE_INFINITE
,
1724 pos
.undo_move(moves
[count
].move
, u
);
1725 moves
[count
].pv
[0] = moves
[i
].move
;
1726 moves
[count
].pv
[1] = MOVE_NONE
; // FIXME
1734 // Simple accessor methods for the RootMoveList class
1736 inline Move
RootMoveList::get_move(int moveNum
) const {
1737 return moves
[moveNum
].move
;
1740 inline Value
RootMoveList::get_move_score(int moveNum
) const {
1741 return moves
[moveNum
].score
;
1744 inline void RootMoveList::set_move_score(int moveNum
, Value score
) {
1745 moves
[moveNum
].score
= score
;
1748 inline void RootMoveList::set_move_nodes(int moveNum
, int64_t nodes
) {
1749 moves
[moveNum
].nodes
= nodes
;
1750 moves
[moveNum
].cumulativeNodes
+= nodes
;
1753 void RootMoveList::set_move_pv(int moveNum
, const Move pv
[]) {
1755 for(j
= 0; pv
[j
] != MOVE_NONE
; j
++)
1756 moves
[moveNum
].pv
[j
] = pv
[j
];
1757 moves
[moveNum
].pv
[j
] = MOVE_NONE
;
1760 inline Move
RootMoveList::get_move_pv(int moveNum
, int i
) const {
1761 return moves
[moveNum
].pv
[i
];
1764 inline int64_t RootMoveList::get_move_cumulative_nodes(int moveNum
) const {
1765 return moves
[moveNum
].cumulativeNodes
;
1768 inline int RootMoveList::move_count() const {
1773 // RootMoveList::scan_for_easy_move() is called at the end of the first
1774 // iteration, and is used to detect an "easy move", i.e. a move which appears
1775 // to be much bester than all the rest. If an easy move is found, the move
1776 // is returned, otherwise the function returns MOVE_NONE. It is very
1777 // important that this function is called at the right moment: The code
1778 // assumes that the first iteration has been completed and the moves have
1779 // been sorted. This is done in RootMoveList c'tor.
1781 Move
RootMoveList::scan_for_easy_move() const {
1788 // moves are sorted so just consider the best and the second one
1789 if (get_move_score(0) > get_move_score(1) + EasyMoveMargin
)
1795 // RootMoveList::sort() sorts the root move list at the beginning of a new
1798 inline void RootMoveList::sort() {
1800 sort_multipv(count
- 1); // all items
1804 // RootMoveList::sort_multipv() sorts the first few moves in the root move
1805 // list by their scores and depths. It is used to order the different PVs
1806 // correctly in MultiPV mode.
1808 void RootMoveList::sort_multipv(int n
) {
1810 for (int i
= 1; i
<= n
; i
++)
1812 RootMove rm
= moves
[i
];
1814 for (j
= i
; j
> 0 && moves
[j
-1] < rm
; j
--)
1815 moves
[j
] = moves
[j
-1];
1821 // init_search_stack() initializes a search stack at the beginning of a
1822 // new search from the root.
1824 void init_search_stack(SearchStack ss
[]) {
1825 for(int i
= 0; i
< 3; i
++) {
1826 ss
[i
].pv
[i
] = MOVE_NONE
;
1827 ss
[i
].pv
[i
+1] = MOVE_NONE
;
1828 ss
[i
].currentMove
= MOVE_NONE
;
1829 ss
[i
].mateKiller
= MOVE_NONE
;
1830 ss
[i
].killer1
= MOVE_NONE
;
1831 ss
[i
].killer2
= MOVE_NONE
;
1832 ss
[i
].threatMove
= MOVE_NONE
;
1833 ss
[i
].reduction
= Depth(0);
1838 // init_node() is called at the beginning of all the search functions
1839 // (search(), search_pv(), qsearch(), and so on) and initializes the search
1840 // stack object corresponding to the current node. Once every
1841 // NodesBetweenPolls nodes, init_node() also calls poll(), which polls
1842 // for user input and checks whether it is time to stop the search.
1844 void init_node(const Position
&pos
, SearchStack ss
[], int ply
, int threadID
) {
1845 assert(ply
>= 0 && ply
< PLY_MAX
);
1846 assert(threadID
>= 0 && threadID
< ActiveThreads
);
1848 Threads
[threadID
].nodes
++;
1852 if(NodesSincePoll
>= NodesBetweenPolls
) {
1858 ss
[ply
].pv
[ply
] = ss
[ply
].pv
[ply
+1] = ss
[ply
].currentMove
= MOVE_NONE
;
1859 ss
[ply
+2].mateKiller
= MOVE_NONE
;
1860 ss
[ply
+2].killer1
= ss
[ply
+2].killer2
= MOVE_NONE
;
1861 ss
[ply
].threatMove
= MOVE_NONE
;
1862 ss
[ply
].reduction
= Depth(0);
1863 ss
[ply
].currentMoveCaptureValue
= Value(0);
1865 if(Threads
[threadID
].printCurrentLine
)
1866 print_current_line(ss
, ply
, threadID
);
1870 // update_pv() is called whenever a search returns a value > alpha. It
1871 // updates the PV in the SearchStack object corresponding to the current
1874 void update_pv(SearchStack ss
[], int ply
) {
1875 assert(ply
>= 0 && ply
< PLY_MAX
);
1877 ss
[ply
].pv
[ply
] = ss
[ply
].currentMove
;
1879 for(p
= ply
+ 1; ss
[ply
+1].pv
[p
] != MOVE_NONE
; p
++)
1880 ss
[ply
].pv
[p
] = ss
[ply
+1].pv
[p
];
1881 ss
[ply
].pv
[p
] = MOVE_NONE
;
1885 // sp_update_pv() is a variant of update_pv for use at split points. The
1886 // difference between the two functions is that sp_update_pv also updates
1887 // the PV at the parent node.
1889 void sp_update_pv(SearchStack
*pss
, SearchStack ss
[], int ply
) {
1890 assert(ply
>= 0 && ply
< PLY_MAX
);
1892 ss
[ply
].pv
[ply
] = pss
[ply
].pv
[ply
] = ss
[ply
].currentMove
;
1894 for(p
= ply
+ 1; ss
[ply
+1].pv
[p
] != MOVE_NONE
; p
++)
1895 ss
[ply
].pv
[p
] = pss
[ply
].pv
[p
] = ss
[ply
+1].pv
[p
];
1896 ss
[ply
].pv
[p
] = pss
[ply
].pv
[p
] = MOVE_NONE
;
1900 // connected_moves() tests whether two moves are 'connected' in the sense
1901 // that the first move somehow made the second move possible (for instance
1902 // if the moving piece is the same in both moves). The first move is
1903 // assumed to be the move that was made to reach the current position, while
1904 // the second move is assumed to be a move from the current position.
1906 bool connected_moves(const Position
&pos
, Move m1
, Move m2
) {
1907 Square f1
, t1
, f2
, t2
;
1909 assert(move_is_ok(m1
));
1910 assert(move_is_ok(m2
));
1915 // Case 1: The moving piece is the same in both moves.
1921 // Case 2: The destination square for m2 was vacated by m1.
1927 // Case 3: Moving through the vacated square:
1928 if(piece_is_slider(pos
.piece_on(f2
)) &&
1929 bit_is_set(squares_between(f2
, t2
), f1
))
1932 // Case 4: The destination square for m2 is attacked by the moving piece
1934 if(pos
.piece_attacks_square(t1
, t2
))
1937 // Case 5: Discovered check, checking piece is the piece moved in m1:
1938 if(piece_is_slider(pos
.piece_on(t1
)) &&
1939 bit_is_set(squares_between(t1
, pos
.king_square(pos
.side_to_move())),
1941 !bit_is_set(squares_between(t2
, pos
.king_square(pos
.side_to_move())),
1943 Bitboard occ
= pos
.occupied_squares();
1944 Color us
= pos
.side_to_move();
1945 Square ksq
= pos
.king_square(us
);
1946 clear_bit(&occ
, f2
);
1947 if(pos
.type_of_piece_on(t1
) == BISHOP
) {
1948 if(bit_is_set(bishop_attacks_bb(ksq
, occ
), t1
))
1951 else if(pos
.type_of_piece_on(t1
) == ROOK
) {
1952 if(bit_is_set(rook_attacks_bb(ksq
, occ
), t1
))
1956 assert(pos
.type_of_piece_on(t1
) == QUEEN
);
1957 if(bit_is_set(queen_attacks_bb(ksq
, occ
), t1
))
1966 // extension() decides whether a move should be searched with normal depth,
1967 // or with extended depth. Certain classes of moves (checking moves, in
1968 // particular) are searched with bigger depth than ordinary moves.
1970 Depth
extension(const Position
&pos
, Move m
, bool pvNode
,
1971 bool check
, bool singleReply
, bool mateThreat
) {
1972 Depth result
= Depth(0);
1975 result
+= CheckExtension
[pvNode
];
1977 result
+= SingleReplyExtension
[pvNode
];
1978 if(pos
.move_is_pawn_push_to_7th(m
))
1979 result
+= PawnPushTo7thExtension
[pvNode
];
1980 if(pos
.move_is_passed_pawn_push(m
))
1981 result
+= PassedPawnExtension
[pvNode
];
1983 result
+= MateThreatExtension
[pvNode
];
1984 if(pos
.midgame_value_of_piece_on(move_to(m
)) >= RookValueMidgame
1985 && (pos
.non_pawn_material(WHITE
) + pos
.non_pawn_material(BLACK
)
1986 - pos
.midgame_value_of_piece_on(move_to(m
)) == Value(0))
1987 && !move_promotion(m
))
1988 result
+= PawnEndgameExtension
[pvNode
];
1989 if(pvNode
&& pos
.move_is_capture(m
)
1990 && pos
.type_of_piece_on(move_to(m
)) != PAWN
&& pos
.see(m
) >= 0)
1993 return Min(result
, OnePly
);
1997 // ok_to_do_nullmove() looks at the current position and decides whether
1998 // doing a 'null move' should be allowed. In order to avoid zugzwang
1999 // problems, null moves are not allowed when the side to move has very
2000 // little material left. Currently, the test is a bit too simple: Null
2001 // moves are avoided only when the side to move has only pawns left. It's
2002 // probably a good idea to avoid null moves in at least some more
2003 // complicated endgames, e.g. KQ vs KR. FIXME
2005 bool ok_to_do_nullmove(const Position
&pos
) {
2006 if(pos
.non_pawn_material(pos
.side_to_move()) == Value(0))
2012 // ok_to_prune() tests whether it is safe to forward prune a move. Only
2013 // non-tactical moves late in the move list close to the leaves are
2014 // candidates for pruning.
2016 bool ok_to_prune(const Position
&pos
, Move m
, Move threat
, Depth d
) {
2017 Square mfrom
, mto
, tfrom
, tto
;
2019 assert(move_is_ok(m
));
2020 assert(threat
== MOVE_NONE
|| move_is_ok(threat
));
2021 assert(!move_promotion(m
));
2022 assert(!pos
.move_is_check(m
));
2023 assert(!pos
.move_is_capture(m
));
2024 assert(!pos
.move_is_passed_pawn_push(m
));
2025 assert(d
>= OnePly
);
2027 mfrom
= move_from(m
);
2029 tfrom
= move_from(threat
);
2030 tto
= move_to(threat
);
2032 // Case 1: Castling moves are never pruned.
2033 if(move_is_castle(m
))
2036 // Case 2: Don't prune moves which move the threatened piece
2037 if(!PruneEscapeMoves
&& threat
!= MOVE_NONE
&& mfrom
== tto
)
2040 // Case 3: If the threatened piece has value less than or equal to the
2041 // value of the threatening piece, don't prune move which defend it.
2042 if(!PruneDefendingMoves
&& threat
!= MOVE_NONE
2043 && (piece_value_midgame(pos
.piece_on(tfrom
))
2044 >= piece_value_midgame(pos
.piece_on(tto
)))
2045 && pos
.move_attacks_square(m
, tto
))
2048 // Case 4: Don't prune moves with good history.
2049 if(!H
.ok_to_prune(pos
.piece_on(move_from(m
)), m
, d
))
2052 // Case 5: If the moving piece in the threatened move is a slider, don't
2053 // prune safe moves which block its ray.
2054 if(!PruneBlockingMoves
&& threat
!= MOVE_NONE
2055 && piece_is_slider(pos
.piece_on(tfrom
))
2056 && bit_is_set(squares_between(tfrom
, tto
), mto
) && pos
.see(m
) >= 0)
2063 // ok_to_use_TT() returns true if a transposition table score
2064 // can be used at a given point in search.
2066 bool ok_to_use_TT(const TTEntry
* tte
, Depth depth
, Value beta
, int ply
) {
2068 Value v
= value_from_tt(tte
->value(), ply
);
2070 return ( tte
->depth() >= depth
2071 || v
>= Max(value_mate_in(100), beta
)
2072 || v
< Min(value_mated_in(100), beta
))
2074 && ( (is_lower_bound(tte
->type()) && v
>= beta
)
2075 || (is_upper_bound(tte
->type()) && v
< beta
));
2079 // ok_to_history() returns true if a move m can be stored
2080 // in history. Should be a non capturing move.
2082 bool ok_to_history(const Position
& pos
, Move m
) {
2084 return pos
.square_is_empty(move_to(m
))
2085 && !move_promotion(m
)
2090 // update_history() registers a good move that produced a beta-cutoff
2091 // in history and marks as failures all the other moves of that ply.
2093 void update_history(const Position
& pos
, Move m
, Depth depth
,
2094 Move movesSearched
[], int moveCount
) {
2096 H
.success(pos
.piece_on(move_from(m
)), m
, depth
);
2098 for (int i
= 0; i
< moveCount
- 1; i
++)
2099 if (ok_to_history(pos
, movesSearched
[i
]) && m
!= movesSearched
[i
])
2100 H
.failure(pos
.piece_on(move_from(movesSearched
[i
])), movesSearched
[i
]);
2103 // fail_high_ply_1() checks if some thread is currently resolving a fail
2104 // high at ply 1 at the node below the first root node. This information
2105 // is used for time managment.
2107 bool fail_high_ply_1() {
2108 for(int i
= 0; i
< ActiveThreads
; i
++)
2109 if(Threads
[i
].failHighPly1
)
2115 // current_search_time() returns the number of milliseconds which have passed
2116 // since the beginning of the current search.
2118 int current_search_time() {
2119 return get_system_time() - SearchStartTime
;
2123 // nps() computes the current nodes/second count.
2126 int t
= current_search_time();
2127 return (t
> 0)? int((nodes_searched() * 1000) / t
) : 0;
2131 // poll() performs two different functions: It polls for user input, and it
2132 // looks at the time consumed so far and decides if it's time to abort the
2137 static int lastInfoTime
;
2138 int t
= current_search_time();
2143 // We are line oriented, don't read single chars
2144 std::string command
;
2145 if (!std::getline(std::cin
, command
))
2148 if (command
== "quit")
2151 PonderSearch
= false;
2154 else if(command
== "stop")
2157 PonderSearch
= false;
2159 else if(command
== "ponderhit")
2162 // Print search information
2166 else if (lastInfoTime
> t
)
2167 // HACK: Must be a new search where we searched less than
2168 // NodesBetweenPolls nodes during the first second of search.
2171 else if (t
- lastInfoTime
>= 1000)
2175 std::cout
<< "info nodes " << nodes_searched() << " nps " << nps()
2176 << " time " << t
<< " hashfull " << TT
.full() << std::endl
;
2177 lock_release(&IOLock
);
2178 if (ShowCurrentLine
)
2179 Threads
[0].printCurrentLine
= true;
2181 // Should we stop the search?
2185 bool overTime
= t
> AbsoluteMaxSearchTime
2186 || (RootMoveNumber
== 1 && t
> MaxSearchTime
+ ExtraSearchTime
)
2187 || ( !FailHigh
&& !fail_high_ply_1() && !Problem
2188 && t
> 6*(MaxSearchTime
+ ExtraSearchTime
));
2190 if ( (Iteration
>= 2 && (!InfiniteSearch
&& overTime
))
2191 || (ExactMaxTime
&& t
>= ExactMaxTime
)
2192 || (Iteration
>= 3 && MaxNodes
&& nodes_searched() >= MaxNodes
))
2197 // ponderhit() is called when the program is pondering (i.e. thinking while
2198 // it's the opponent's turn to move) in order to let the engine know that
2199 // it correctly predicted the opponent's move.
2202 int t
= current_search_time();
2203 PonderSearch
= false;
2204 if(Iteration
>= 2 &&
2205 (!InfiniteSearch
&& (StopOnPonderhit
||
2206 t
> AbsoluteMaxSearchTime
||
2207 (RootMoveNumber
== 1 &&
2208 t
> MaxSearchTime
+ ExtraSearchTime
) ||
2209 (!FailHigh
&& !fail_high_ply_1() && !Problem
&&
2210 t
> 6*(MaxSearchTime
+ ExtraSearchTime
)))))
2215 // print_current_line() prints the current line of search for a given
2216 // thread. Called when the UCI option UCI_ShowCurrLine is 'true'.
2218 void print_current_line(SearchStack ss
[], int ply
, int threadID
) {
2219 assert(ply
>= 0 && ply
< PLY_MAX
);
2220 assert(threadID
>= 0 && threadID
< ActiveThreads
);
2222 if(!Threads
[threadID
].idle
) {
2224 std::cout
<< "info currline " << (threadID
+ 1);
2225 for(int p
= 0; p
< ply
; p
++)
2226 std::cout
<< " " << ss
[p
].currentMove
;
2227 std::cout
<< std::endl
;
2228 lock_release(&IOLock
);
2230 Threads
[threadID
].printCurrentLine
= false;
2231 if(threadID
+ 1 < ActiveThreads
)
2232 Threads
[threadID
+ 1].printCurrentLine
= true;
2236 // wait_for_stop_or_ponderhit() is called when the maximum depth is reached
2237 // while the program is pondering. The point is to work around a wrinkle in
2238 // the UCI protocol: When pondering, the engine is not allowed to give a
2239 // "bestmove" before the GUI sends it a "stop" or "ponderhit" command.
2240 // We simply wait here until one of these commands is sent, and return,
2241 // after which the bestmove and pondermove will be printed (in id_loop()).
2243 void wait_for_stop_or_ponderhit() {
2244 std::string command
;
2247 if(!std::getline(std::cin
, command
))
2250 if(command
== "quit") {
2251 OpeningBook
.close();
2256 else if(command
== "ponderhit" || command
== "stop")
2262 // idle_loop() is where the threads are parked when they have no work to do.
2263 // The parameter "waitSp", if non-NULL, is a pointer to an active SplitPoint
2264 // object for which the current thread is the master.
2266 void idle_loop(int threadID
, SplitPoint
*waitSp
) {
2267 assert(threadID
>= 0 && threadID
< THREAD_MAX
);
2269 Threads
[threadID
].running
= true;
2272 if(AllThreadsShouldExit
&& threadID
!= 0)
2275 // If we are not thinking, wait for a condition to be signaled instead
2276 // of wasting CPU time polling for work:
2277 while(threadID
!= 0 && (Idle
|| threadID
>= ActiveThreads
)) {
2278 #if !defined(_MSC_VER)
2279 pthread_mutex_lock(&WaitLock
);
2280 if(Idle
|| threadID
>= ActiveThreads
)
2281 pthread_cond_wait(&WaitCond
, &WaitLock
);
2282 pthread_mutex_unlock(&WaitLock
);
2284 WaitForSingleObject(SitIdleEvent
[threadID
], INFINITE
);
2288 // If this thread has been assigned work, launch a search:
2289 if(Threads
[threadID
].workIsWaiting
) {
2290 Threads
[threadID
].workIsWaiting
= false;
2291 if(Threads
[threadID
].splitPoint
->pvNode
)
2292 sp_search_pv(Threads
[threadID
].splitPoint
, threadID
);
2294 sp_search(Threads
[threadID
].splitPoint
, threadID
);
2295 Threads
[threadID
].idle
= true;
2298 // If this thread is the master of a split point and all threads have
2299 // finished their work at this split point, return from the idle loop:
2300 if(waitSp
!= NULL
&& waitSp
->cpus
== 0)
2304 Threads
[threadID
].running
= false;
2308 // init_split_point_stack() is called during program initialization, and
2309 // initializes all split point objects.
2311 void init_split_point_stack() {
2312 for(int i
= 0; i
< THREAD_MAX
; i
++)
2313 for(int j
= 0; j
< MaxActiveSplitPoints
; j
++) {
2314 SplitPointStack
[i
][j
].parent
= NULL
;
2315 lock_init(&(SplitPointStack
[i
][j
].lock
), NULL
);
2320 // destroy_split_point_stack() is called when the program exits, and
2321 // destroys all locks in the precomputed split point objects.
2323 void destroy_split_point_stack() {
2324 for(int i
= 0; i
< THREAD_MAX
; i
++)
2325 for(int j
= 0; j
< MaxActiveSplitPoints
; j
++)
2326 lock_destroy(&(SplitPointStack
[i
][j
].lock
));
2330 // thread_should_stop() checks whether the thread with a given threadID has
2331 // been asked to stop, directly or indirectly. This can happen if a beta
2332 // cutoff has occured in thre thread's currently active split point, or in
2333 // some ancestor of the current split point.
2335 bool thread_should_stop(int threadID
) {
2336 assert(threadID
>= 0 && threadID
< ActiveThreads
);
2340 if(Threads
[threadID
].stop
)
2342 if(ActiveThreads
<= 2)
2344 for(sp
= Threads
[threadID
].splitPoint
; sp
!= NULL
; sp
= sp
->parent
)
2346 Threads
[threadID
].stop
= true;
2353 // thread_is_available() checks whether the thread with threadID "slave" is
2354 // available to help the thread with threadID "master" at a split point. An
2355 // obvious requirement is that "slave" must be idle. With more than two
2356 // threads, this is not by itself sufficient: If "slave" is the master of
2357 // some active split point, it is only available as a slave to the other
2358 // threads which are busy searching the split point at the top of "slave"'s
2359 // split point stack (the "helpful master concept" in YBWC terminology).
2361 bool thread_is_available(int slave
, int master
) {
2362 assert(slave
>= 0 && slave
< ActiveThreads
);
2363 assert(master
>= 0 && master
< ActiveThreads
);
2364 assert(ActiveThreads
> 1);
2366 if(!Threads
[slave
].idle
|| slave
== master
)
2369 if(Threads
[slave
].activeSplitPoints
== 0)
2370 // No active split points means that the thread is available as a slave
2371 // for any other thread.
2374 if(ActiveThreads
== 2)
2377 // Apply the "helpful master" concept if possible.
2378 if(SplitPointStack
[slave
][Threads
[slave
].activeSplitPoints
-1].slaves
[master
])
2385 // idle_thread_exists() tries to find an idle thread which is available as
2386 // a slave for the thread with threadID "master".
2388 bool idle_thread_exists(int master
) {
2389 assert(master
>= 0 && master
< ActiveThreads
);
2390 assert(ActiveThreads
> 1);
2392 for(int i
= 0; i
< ActiveThreads
; i
++)
2393 if(thread_is_available(i
, master
))
2399 // split() does the actual work of distributing the work at a node between
2400 // several threads at PV nodes. If it does not succeed in splitting the
2401 // node (because no idle threads are available, or because we have no unused
2402 // split point objects), the function immediately returns false. If
2403 // splitting is possible, a SplitPoint object is initialized with all the
2404 // data that must be copied to the helper threads (the current position and
2405 // search stack, alpha, beta, the search depth, etc.), and we tell our
2406 // helper threads that they have been assigned work. This will cause them
2407 // to instantly leave their idle loops and call sp_search_pv(). When all
2408 // threads have returned from sp_search_pv (or, equivalently, when
2409 // splitPoint->cpus becomes 0), split() returns true.
2411 bool split(const Position
&p
, SearchStack
*sstck
, int ply
,
2412 Value
*alpha
, Value
*beta
, Value
*bestValue
,
2413 Depth depth
, int *moves
,
2414 MovePicker
*mp
, Bitboard dcCandidates
, int master
, bool pvNode
) {
2416 assert(sstck
!= NULL
);
2417 assert(ply
>= 0 && ply
< PLY_MAX
);
2418 assert(*bestValue
>= -VALUE_INFINITE
&& *bestValue
<= *alpha
);
2419 assert(!pvNode
|| *alpha
< *beta
);
2420 assert(*beta
<= VALUE_INFINITE
);
2421 assert(depth
> Depth(0));
2422 assert(master
>= 0 && master
< ActiveThreads
);
2423 assert(ActiveThreads
> 1);
2425 SplitPoint
*splitPoint
;
2430 // If no other thread is available to help us, or if we have too many
2431 // active split points, don't split:
2432 if(!idle_thread_exists(master
) ||
2433 Threads
[master
].activeSplitPoints
>= MaxActiveSplitPoints
) {
2434 lock_release(&MPLock
);
2438 // Pick the next available split point object from the split point stack:
2439 splitPoint
= SplitPointStack
[master
] + Threads
[master
].activeSplitPoints
;
2440 Threads
[master
].activeSplitPoints
++;
2442 // Initialize the split point object:
2443 splitPoint
->parent
= Threads
[master
].splitPoint
;
2444 splitPoint
->finished
= false;
2445 splitPoint
->ply
= ply
;
2446 splitPoint
->depth
= depth
;
2447 splitPoint
->alpha
= pvNode
? *alpha
: (*beta
- 1);
2448 splitPoint
->beta
= *beta
;
2449 splitPoint
->pvNode
= pvNode
;
2450 splitPoint
->dcCandidates
= dcCandidates
;
2451 splitPoint
->bestValue
= *bestValue
;
2452 splitPoint
->master
= master
;
2453 splitPoint
->mp
= mp
;
2454 splitPoint
->moves
= *moves
;
2455 splitPoint
->cpus
= 1;
2456 splitPoint
->pos
.copy(p
);
2457 splitPoint
->parentSstack
= sstck
;
2458 for(i
= 0; i
< ActiveThreads
; i
++)
2459 splitPoint
->slaves
[i
] = 0;
2461 // Copy the current position and the search stack to the master thread:
2462 memcpy(splitPoint
->sstack
[master
], sstck
, (ply
+1)*sizeof(SearchStack
));
2463 Threads
[master
].splitPoint
= splitPoint
;
2465 // Make copies of the current position and search stack for each thread:
2466 for(i
= 0; i
< ActiveThreads
&& splitPoint
->cpus
< MaxThreadsPerSplitPoint
;
2468 if(thread_is_available(i
, master
)) {
2469 memcpy(splitPoint
->sstack
[i
], sstck
, (ply
+1)*sizeof(SearchStack
));
2470 Threads
[i
].splitPoint
= splitPoint
;
2471 splitPoint
->slaves
[i
] = 1;
2475 // Tell the threads that they have work to do. This will make them leave
2477 for(i
= 0; i
< ActiveThreads
; i
++)
2478 if(i
== master
|| splitPoint
->slaves
[i
]) {
2479 Threads
[i
].workIsWaiting
= true;
2480 Threads
[i
].idle
= false;
2481 Threads
[i
].stop
= false;
2484 lock_release(&MPLock
);
2486 // Everything is set up. The master thread enters the idle loop, from
2487 // which it will instantly launch a search, because its workIsWaiting
2488 // slot is 'true'. We send the split point as a second parameter to the
2489 // idle loop, which means that the main thread will return from the idle
2490 // loop when all threads have finished their work at this split point
2491 // (i.e. when // splitPoint->cpus == 0).
2492 idle_loop(master
, splitPoint
);
2494 // We have returned from the idle loop, which means that all threads are
2495 // finished. Update alpha, beta and bestvalue, and return:
2497 if(pvNode
) *alpha
= splitPoint
->alpha
;
2498 *beta
= splitPoint
->beta
;
2499 *bestValue
= splitPoint
->bestValue
;
2500 Threads
[master
].stop
= false;
2501 Threads
[master
].idle
= false;
2502 Threads
[master
].activeSplitPoints
--;
2503 Threads
[master
].splitPoint
= splitPoint
->parent
;
2504 lock_release(&MPLock
);
2510 // wake_sleeping_threads() wakes up all sleeping threads when it is time
2511 // to start a new search from the root.
2513 void wake_sleeping_threads() {
2514 if(ActiveThreads
> 1) {
2515 for(int i
= 1; i
< ActiveThreads
; i
++) {
2516 Threads
[i
].idle
= true;
2517 Threads
[i
].workIsWaiting
= false;
2519 #if !defined(_MSC_VER)
2520 pthread_mutex_lock(&WaitLock
);
2521 pthread_cond_broadcast(&WaitCond
);
2522 pthread_mutex_unlock(&WaitLock
);
2524 for(int i
= 1; i
< THREAD_MAX
; i
++)
2525 SetEvent(SitIdleEvent
[i
]);
2531 // init_thread() is the function which is called when a new thread is
2532 // launched. It simply calls the idle_loop() function with the supplied
2533 // threadID. There are two versions of this function; one for POSIX threads
2534 // and one for Windows threads.
2536 #if !defined(_MSC_VER)
2538 void *init_thread(void *threadID
) {
2539 idle_loop(*(int *)threadID
, NULL
);
2545 DWORD WINAPI
init_thread(LPVOID threadID
) {
2546 idle_loop(*(int *)threadID
, NULL
);