X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=9a1fa821211c317bed64fb25e71a82d9604a23d9;hp=74ed69ff6495b7b4a04ee84804547342192b74dd;hb=91601d7f95a3e84d2d46ca9a36637508197dbdab;hpb=9c7d72739cffe523f0ea8c84875160c17ae6ab82 diff --git a/src/search.cpp b/src/search.cpp index 74ed69ff..9a1fa821 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -30,7 +30,6 @@ #include "evaluate.h" #include "history.h" #include "misc.h" -#include "move.h" #include "movegen.h" #include "movepick.h" #include "search.h" @@ -39,9 +38,18 @@ #include "tt.h" #include "ucioption.h" +namespace Search { + + volatile SignalsType Signals; + LimitsType Limits; + std::vector RootMoves; + Position RootPosition; +} + using std::cout; using std::endl; using std::string; +using namespace Search; namespace { @@ -74,7 +82,7 @@ namespace { // RootMoveList struct is mainly a std::vector of RootMove objects struct RootMoveList : public std::vector { - void init(Position& pos, Move searchMoves[]); + void init(Position& pos, Move rootMoves[]); RootMove* find(const Move& m, int startIndex = 0); int bestMoveChanges; @@ -87,8 +95,6 @@ namespace { const bool Slidings[18] = { 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1 }; inline bool piece_is_slider(Piece p) { return Slidings[p]; } - // Step 6. Razoring - // Maximum depth for razoring const Depth RazorDepth = 4 * ONE_PLY; @@ -98,8 +104,6 @@ namespace { // Maximum depth for use of dynamic threat detection when null move fails low const Depth ThreatDepth = 5 * ONE_PLY; - // Step 9. Internal iterative deepening - // Minimum depth for use of internal iterative deepening const Depth IIDDepth[] = { 8 * ONE_PLY, 5 * ONE_PLY }; @@ -107,19 +111,9 @@ namespace { // when the static evaluation is bigger then beta - IIDMargin. const Value IIDMargin = Value(0x100); - // Step 11. Decide the new search depth - - // Extensions. Array index 0 is used for non-PV nodes, index 1 for PV nodes - const Depth CheckExtension[] = { ONE_PLY / 2, ONE_PLY / 1 }; - const Depth PawnEndgameExtension[] = { ONE_PLY / 1, ONE_PLY / 1 }; - const Depth PawnPushTo7thExtension[] = { ONE_PLY / 2, ONE_PLY / 2 }; - const Depth PassedPawnExtension[] = { DEPTH_ZERO, ONE_PLY / 2 }; - // Minimum depth for use of singular extension const Depth SingularExtensionDepth[] = { 8 * ONE_PLY, 6 * ONE_PLY }; - // Step 12. Futility pruning - // Futility margin for quiescence search const Value FutilityMarginQS = Value(0x80); @@ -138,8 +132,6 @@ namespace { return d < 16 * ONE_PLY ? FutilityMoveCounts[d] : MAX_MOVES; } - // Step 14. Reduced search - // Reduction lookup tables (initialized at startup) and their access function int8_t Reductions[2][64][64]; // [pv][depth][moveNumber] @@ -155,34 +147,23 @@ namespace { /// Namespace variables - // Root move list RootMoveList Rml; - - // MultiPV mode - int MultiPV, UCIMultiPV, MultiPVIdx; - - // Time management variables - volatile bool StopOnPonderhit, FirstRootMove, StopRequest, QuitRequest, AspirationFailLow; + size_t MultiPV, UCIMultiPV, MultiPVIdx; TimeManager TimeMgr; - SearchLimits Limits; - - // Skill level adjustment int SkillLevel; bool SkillLevelEnabled; - - // History table History H; /// Local functions - Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove); + Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove); template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth); + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth); bool check_is_dangerous(Position &pos, Move move, Value futilityBase, Value beta, Value *bValue); bool connected_moves(const Position& pos, Move m1, Move m2); @@ -194,27 +175,26 @@ namespace { void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount); void do_skill_level(Move* best, Move* ponder); - int elapsed_search_time(int set = 0); + int elapsed_time(bool reset = false); string score_to_uci(Value v, Value alpha = -VALUE_INFINITE, Value beta = VALUE_INFINITE); string speed_to_uci(int64_t nodes); string pv_to_uci(const Move pv[], int pvNum, bool chess960); string pretty_pv(Position& pos, int depth, Value score, int time, Move pv[]); string depth_to_uci(Depth depth); - void wait_for_stop_or_ponderhit(); // MovePickerExt template class extends MovePicker and allows to choose at compile // time the proper moves source according to the type of node. In the default case // we simply create and use a standard MovePicker object. template struct MovePickerExt : public MovePicker { - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) + MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b) {} }; // In case of a SpNode we use split point's shared MovePicker object as moves source template<> struct MovePickerExt : public MovePicker { - MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, SearchStack* ss, Value b) + MovePickerExt(const Position& p, Move ttm, Depth d, const History& h, Stack* ss, Value b) : MovePicker(p, ttm, d, h, ss, b), mp(ss->sp->mp) {} Move get_next_move() { return mp->get_next_move(); } @@ -243,49 +223,28 @@ namespace { return os; } - // extension() decides whether a move should be searched with normal depth, - // or with extended depth. Certain classes of moves (checking moves, in - // particular) are searched with bigger depth than ordinary moves and in - // any case are marked as 'dangerous'. Note that also if a move is not - // extended, as example because the corresponding UCI option is set to zero, - // the move is marked as 'dangerous' so, at least, we avoid to prune it. - template - FORCE_INLINE Depth extension(const Position& pos, Move m, bool captureOrPromotion, - bool moveIsCheck, bool* dangerous) { - assert(m != MOVE_NONE); - - Depth result = DEPTH_ZERO; - *dangerous = moveIsCheck; - - if (moveIsCheck && pos.see_sign(m) >= 0) - result += CheckExtension[PvNode]; + // is_dangerous() checks whether a move belongs to some classes of known + // 'dangerous' moves so that we avoid to prune it. + FORCE_INLINE bool is_dangerous(const Position& pos, Move m, bool captureOrPromotion) { + // Test for a pawn pushed to 7th or a passed pawn move if (type_of(pos.piece_on(move_from(m))) == PAWN) { Color c = pos.side_to_move(); - if (relative_rank(c, move_to(m)) == RANK_7) - { - result += PawnPushTo7thExtension[PvNode]; - *dangerous = true; - } - if (pos.pawn_is_passed(c, move_to(m))) - { - result += PassedPawnExtension[PvNode]; - *dangerous = true; - } + if ( relative_rank(c, move_to(m)) == RANK_7 + || pos.pawn_is_passed(c, move_to(m))) + return true; } + // Test for a capture that triggers a pawn endgame if ( captureOrPromotion && type_of(pos.piece_on(move_to(m))) != PAWN && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK) - PieceValueMidgame[pos.piece_on(move_to(m))] == VALUE_ZERO) && !is_special(m)) - { - result += PawnEndgameExtension[PvNode]; - *dangerous = true; - } + return true; - return std::min(result, ONE_PLY); + return false; } } // namespace @@ -293,7 +252,7 @@ namespace { /// init_search() is called during startup to initialize various lookup tables -void init_search() { +void Search::init() { int d; // depth (ONE_PLY == 2) int hd; // half depth (ONE_PLY == 1) @@ -321,20 +280,17 @@ void init_search() { /// perft() is our utility to verify move generation. All the leaf nodes up to /// the given depth are generated and counted and the sum returned. -int64_t perft(Position& pos, Depth depth) { +int64_t Search::perft(Position& pos, Depth depth) { StateInfo st; int64_t sum = 0; - // Generate all legal moves MoveList ml(pos); - // If we are at the last ply we don't need to do and undo - // the moves, just to count them. + // At the last ply just return the number of moves (leaf nodes) if (depth <= ONE_PLY) return ml.size(); - // Loop through all legal moves CheckInfo ci(pos); for ( ; !ml.end(); ++ml) { @@ -346,26 +302,21 @@ int64_t perft(Position& pos, Depth depth) { } -/// think() is the external interface to Stockfish's search, and is called when -/// the program receives the UCI 'go' command. It initializes various global -/// variables, and calls id_loop(). It returns false when a "quit" command is -/// received during the search. +/// think() is the external interface to Stockfish's search, and is called by the +/// main thread when the program receives the UCI 'go' command. It searches from +/// RootPosition and at the end prints the "bestmove" to output. -bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { +void Search::think() { static Book book; // Defined static to initialize the PRNG only once - // Save "search start" time and reset elapsed time to zero - elapsed_search_time(get_system_time()); - - // Initialize global search-related variables - StopOnPonderhit = StopRequest = QuitRequest = AspirationFailLow = false; - Limits = limits; + Position& pos = RootPosition; + elapsed_time(true); + TimeMgr.init(Limits, pos.startpos_ply_counter()); // Set output stream mode: normal or chess960. Castling notation is different cout << set960(pos.is_chess960()); - // Look for a book move if (Options["OwnBook"].value()) { if (Options["Book File"].value() != book.name()) @@ -374,11 +325,11 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { Move bookMove = book.probe(pos, Options["Best Book Move"].value()); if (bookMove != MOVE_NONE) { - if (Limits.ponder) - wait_for_stop_or_ponderhit(); + if (!Signals.stop && (Limits.ponder || Limits.infinite)) + Threads.wait_for_stop_or_ponderhit(); cout << "bestmove " << bookMove << endl; - return !QuitRequest; + return; } } @@ -386,24 +337,21 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { read_evaluation_uci_options(pos.side_to_move()); Threads.read_uci_options(); - // Set a new TT size if changed TT.set_size(Options["Hash"].value()); - if (Options["Clear Hash"].value()) { Options["Clear Hash"].set_value("false"); TT.clear(); } - UCIMultiPV = Options["MultiPV"].value(); - SkillLevel = Options["Skill Level"].value(); + UCIMultiPV = Options["MultiPV"].value(); + SkillLevel = Options["Skill Level"].value(); // Do we have to play with skill handicap? In this case enable MultiPV that // we will use behind the scenes to retrieve a set of possible moves. SkillLevelEnabled = (SkillLevel < 20); - MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, 4) : UCIMultiPV); + MultiPV = (SkillLevelEnabled ? std::max(UCIMultiPV, (size_t)4) : UCIMultiPV); - // Write current search header to log file if (Options["Use Search Log"].value()) { Log log(Options["Search Log Filename"].value()); @@ -425,34 +373,22 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { // Set best timer interval to avoid lagging under time pressure. Timer is // used to check for remaining available thinking time. - TimeMgr.init(Limits, pos.startpos_ply_counter()); - if (TimeMgr.available_time()) Threads.set_timer(std::min(100, std::max(TimeMgr.available_time() / 8, 20))); else Threads.set_timer(100); - // Start async mode to catch UCI commands sent to us while searching, - // like "quit", "stop", etc. - Threads.start_listener(); - // We're ready to start thinking. Call the iterative deepening loop function Move ponderMove = MOVE_NONE; - Move bestMove = id_loop(pos, searchMoves, &ponderMove); - - // From now on any UCI command will be read in-sync with Threads.getline() - Threads.stop_listener(); + Move bestMove = id_loop(pos, &RootMoves[0], &ponderMove); - // Stop timer, no need to check for available time any more + // Stop timer and send all the slaves to sleep, if not already sleeping Threads.set_timer(0); - - // This makes all the slave threads to go to sleep, if not already sleeping Threads.set_size(1); - // Write current search final statistics to log file if (Options["Use Search Log"].value()) { - int e = elapsed_search_time(); + int e = elapsed_time(); Log log(Options["Search Log Filename"].value()); log << "Nodes: " << pos.nodes_searched() @@ -468,8 +404,8 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { // When we reach max depth we arrive here even without a StopRequest, but if // we are pondering or in infinite search, we shouldn't print the best move // before we are told to do so. - if (!StopRequest && (Limits.ponder || Limits.infinite)) - wait_for_stop_or_ponderhit(); + if (!Signals.stop && (Limits.ponder || Limits.infinite)) + Threads.wait_for_stop_or_ponderhit(); // Could be MOVE_NONE when searching on a stalemate position cout << "bestmove " << bestMove; @@ -480,8 +416,6 @@ bool think(Position& pos, const SearchLimits& limits, Move searchMoves[]) { cout << " ponder " << ponderMove; cout << endl; - - return !QuitRequest; } @@ -491,9 +425,9 @@ namespace { // with increasing depth until the allocated thinking time has been consumed, // user stops the search, or the maximum search depth is reached. - Move id_loop(Position& pos, Move searchMoves[], Move* ponderMove) { + Move id_loop(Position& pos, Move rootMoves[], Move* ponderMove) { - SearchStack ss[PLY_MAX_PLUS_2]; + Stack ss[PLY_MAX_PLUS_2]; Value bestValues[PLY_MAX_PLUS_2]; int bestMoveChanges[PLY_MAX_PLUS_2]; int depth, aspirationDelta; @@ -501,20 +435,17 @@ namespace { Move bestMove, skillBest, skillPonder; bool bestMoveNeverChanged = true; - // Initialize stuff before a new search - memset(ss, 0, 4 * sizeof(SearchStack)); + memset(ss, 0, 4 * sizeof(Stack)); TT.new_search(); H.clear(); *ponderMove = bestMove = skillBest = skillPonder = MOVE_NONE; depth = aspirationDelta = 0; bestValue = alpha = -VALUE_INFINITE, beta = VALUE_INFINITE; ss->currentMove = MOVE_NULL; // Hack to skip update gains - - // Moves to search are verified and copied - Rml.init(pos, searchMoves); + Rml.init(pos, rootMoves); // Handle special case of searching on a mate/stalemate position - if (!Rml.size()) + if (Rml.empty()) { cout << "info" << depth_to_uci(DEPTH_ZERO) << score_to_uci(pos.in_check() ? -VALUE_MATE : VALUE_DRAW, alpha, beta) << endl; @@ -523,7 +454,7 @@ namespace { } // Iterative deepening loop until requested to stop or target depth reached - while (!StopRequest && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth)) + while (!Signals.stop && ++depth <= PLY_MAX && (!Limits.maxDepth || depth <= Limits.maxDepth)) { // Save now last iteration's scores, before Rml moves are reordered for (size_t i = 0; i < Rml.size(); i++) @@ -532,7 +463,7 @@ namespace { Rml.bestMoveChanges = 0; // MultiPV loop. We perform a full root search for each PV line - for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, (int)Rml.size()); MultiPVIdx++) + for (MultiPVIdx = 0; MultiPVIdx < std::min(MultiPV, Rml.size()); MultiPVIdx++) { // Calculate dynamic aspiration window based on previous iterations if (depth >= 5 && abs(Rml[MultiPVIdx].prevScore) < VALUE_KNOWN_WIN) @@ -576,21 +507,21 @@ namespace { // Write PV back to transposition table in case the relevant entries // have been overwritten during the search. - for (int i = 0; i <= MultiPVIdx; i++) + for (size_t i = 0; i <= MultiPVIdx; i++) Rml[i].insert_pv_in_tt(pos); // If search has been stopped exit the aspiration window loop, // note that sorting and writing PV back to TT is safe becuase // Rml is still valid, although refers to the previous iteration. - if (StopRequest) + if (Signals.stop) break; // Send full PV info to GUI if we are going to leave the loop or // if we have a fail high/low and we are deep in the search. UCI // protocol requires to send all the PV lines also if are still // to be searched and so refer to the previous search's score. - if ((bestValue > alpha && bestValue < beta) || elapsed_search_time() > 2000) - for (int i = 0; i < std::min(UCIMultiPV, (int)Rml.size()); i++) + if ((bestValue > alpha && bestValue < beta) || elapsed_time() > 2000) + for (size_t i = 0; i < std::min(UCIMultiPV, Rml.size()); i++) { bool updated = (i <= MultiPVIdx); @@ -617,8 +548,8 @@ namespace { } else if (bestValue <= alpha) { - AspirationFailLow = true; - StopOnPonderhit = false; + Signals.failedLowAtRoot = true; + Signals.stopOnPonderhit = false; alpha = std::max(alpha - aspirationDelta, -VALUE_INFINITE); aspirationDelta += aspirationDelta / 2; @@ -629,7 +560,6 @@ namespace { } while (abs(bestValue) < VALUE_KNOWN_WIN); } - // Collect info about search result bestMove = Rml[0].pv[0]; *ponderMove = Rml[0].pv[1]; bestValues[depth] = bestValue; @@ -642,7 +572,7 @@ namespace { if (Options["Use Search Log"].value()) { Log log(Options["Search Log Filename"].value()); - log << pretty_pv(pos, depth, bestValue, elapsed_search_time(), &Rml[0].pv[0]) << endl; + log << pretty_pv(pos, depth, bestValue, elapsed_time(), &Rml[0].pv[0]) << endl; } // Filter out startup noise when monitoring best move stability @@ -650,22 +580,24 @@ namespace { bestMoveNeverChanged = false; // Do we have time for the next iteration? Can we stop searching now? - if (!StopRequest && !StopOnPonderhit && Limits.useTimeManagement()) + if (!Signals.stop && !Signals.stopOnPonderhit && Limits.useTimeManagement()) { + bool stop = false; // Local variable instead of the volatile Signals.stop + // Take in account some extra time if the best move has changed if (depth > 4 && depth < 50) TimeMgr.pv_instability(bestMoveChanges[depth], bestMoveChanges[depth - 1]); // Stop search if most of available time is already consumed. We probably don't // have enough time to search the first move at the next iteration anyway. - if (elapsed_search_time() > (TimeMgr.available_time() * 62) / 100) - StopRequest = true; + if (elapsed_time() > (TimeMgr.available_time() * 62) / 100) + stop = true; // Stop search early if one move seems to be much better than others if ( depth >= 10 - && !StopRequest + && !stop && ( bestMoveNeverChanged - || elapsed_search_time() > (TimeMgr.available_time() * 40) / 100)) + || elapsed_time() > (TimeMgr.available_time() * 40) / 100)) { Value rBeta = bestValue - EasyMoveMargin; (ss+1)->excludedMove = bestMove; @@ -675,14 +607,17 @@ namespace { (ss+1)->excludedMove = MOVE_NONE; if (v < rBeta) - StopRequest = true; + stop = true; } - // If we are allowed to ponder do not stop the search now but keep pondering - if (StopRequest && Limits.ponder) // FIXME Limits.ponder is racy + if (stop) { - StopRequest = false; - StopOnPonderhit = true; + // If we are allowed to ponder do not stop the search now but + // keep pondering until GUI sends "ponderhit" or "stop". + if (Limits.ponder) + Signals.stopOnPonderhit = true; + else + Signals.stop = true; } } } @@ -709,7 +644,7 @@ namespace { // here: This is taken care of after we return from the split point. template - Value search(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { + Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { const bool PvNode = (NT == PV || NT == Root || NT == SplitPointPV || NT == SplitPointRoot); const bool SpNode = (NT == SplitPointPV || NT == SplitPointNonPV || NT == SplitPointRoot); @@ -730,7 +665,8 @@ namespace { ValueType vt; Value bestValue, value, oldAlpha; Value refinedValue, nullValue, futilityBase, futilityValue; - bool isPvMove, inCheck, singularExtensionNode, givesCheck, captureOrPromotion, dangerous; + bool isPvMove, inCheck, singularExtensionNode, givesCheck; + bool captureOrPromotion, dangerous, doFullDepthSearch; int moveCount = 0, playedMoveCount = 0; Thread& thread = Threads[pos.thread()]; SplitPoint* sp = NULL; @@ -761,7 +697,7 @@ namespace { } // Step 2. Check for aborted search and immediate draw - if (( StopRequest + if (( Signals.stop || pos.is_draw() || ss->ply > PLY_MAX) && !RootNode) return VALUE_DRAW; @@ -970,7 +906,6 @@ namespace { split_point_start: // At split points actual search starts from here - // Initialize a MovePicker object for the current position MovePickerExt mp(pos, ttMove, depth, H, ss, PvNode ? -VALUE_INFINITE : beta); CheckInfo ci(pos); ss->bestMove = MOVE_NONE; @@ -979,13 +914,16 @@ split_point_start: // At split points actual search starts from here && !SpNode && depth >= SingularExtensionDepth[PvNode] && ttMove != MOVE_NONE - && !excludedMove // Do not allow recursive singular extension search + && !excludedMove // Recursive singular search is not allowed && (tte->type() & VALUE_TYPE_LOWER) && tte->depth() >= depth - 3 * ONE_PLY; if (SpNode) { lock_grab(&(sp->lock)); bestValue = sp->bestValue; + moveCount = sp->moveCount; + + assert(bestValue > -VALUE_INFINITE && moveCount > 0); } // Step 11. Loop through moves @@ -1020,24 +958,28 @@ split_point_start: // At split points actual search starts from here if (RootNode) { // This is used by time management - FirstRootMove = (moveCount == 1); + Signals.firstRootMove = (moveCount == 1); - // Save the current node count before the move is searched nodes = pos.nodes_searched(); - // For long searches send current move info to GUI - if (pos.thread() == 0 && elapsed_search_time() > 2000) + if (pos.thread() == 0 && elapsed_time() > 2000) cout << "info" << depth_to_uci(depth) << " currmove " << move << " currmovenumber " << moveCount + MultiPVIdx << endl; } isPvMove = (PvNode && moveCount <= 1); - givesCheck = pos.move_gives_check(move, ci); captureOrPromotion = pos.is_capture_or_promotion(move); + givesCheck = pos.move_gives_check(move, ci); + dangerous = givesCheck || is_dangerous(pos, move, captureOrPromotion); + ext = DEPTH_ZERO; + + // Step 12. Extend checks and, in PV nodes, also dangerous moves + if (PvNode && dangerous) + ext = ONE_PLY; - // Step 12. Decide the new search depth - ext = extension(pos, move, captureOrPromotion, givesCheck, &dangerous); + else if (givesCheck && pos.see_sign(move) >= 0) + ext = PvNode ? ONE_PLY : ONE_PLY / 2; // Singular extension search. If all moves but one fail low on a search of // (alpha-s, beta-s), and just one fails high on (alpha, beta), then that move @@ -1045,9 +987,9 @@ split_point_start: // At split points actual search starts from here // on all the other moves but the ttMove, if result is lower than ttValue minus // a margin then we extend ttMove. if ( singularExtensionNode + && !ext && move == ttMove - && pos.pl_move_is_legal(move, ci.pinned) - && ext < ONE_PLY) + && pos.pl_move_is_legal(move, ci.pinned)) { Value ttValue = value_from_tt(tte->value(), ss->ply); @@ -1056,11 +998,11 @@ split_point_start: // At split points actual search starts from here Value rBeta = ttValue - int(depth); ss->excludedMove = move; ss->skipNullMove = true; - Value v = search(pos, ss, rBeta - 1, rBeta, depth / 2); + value = search(pos, ss, rBeta - 1, rBeta, depth / 2); ss->skipNullMove = false; ss->excludedMove = MOVE_NONE; ss->bestMove = MOVE_NONE; - if (v < rBeta) + if (value < rBeta) ext = ONE_PLY; } } @@ -1074,12 +1016,12 @@ split_point_start: // At split points actual search starts from here && !inCheck && !dangerous && move != ttMove - && !is_castle(move)) + && !is_castle(move) + && (bestValue > VALUE_MATED_IN_PLY_MAX || bestValue == -VALUE_INFINITE)) { // Move count based pruning if ( moveCount >= futility_move_count(depth) - && (!threatMove || !connected_threat(pos, move, threatMove)) - && bestValue > VALUE_MATED_IN_PLY_MAX) // FIXME bestValue is racy + && (!threatMove || !connected_threat(pos, move, threatMove))) { if (SpNode) lock_grab(&(sp->lock)); @@ -1097,20 +1039,13 @@ split_point_start: // At split points actual search starts from here if (futilityValue < beta) { if (SpNode) - { lock_grab(&(sp->lock)); - if (futilityValue > sp->bestValue) - sp->bestValue = bestValue = futilityValue; - } - else if (futilityValue > bestValue) - bestValue = futilityValue; continue; } // Prune moves with negative SEE at low depths if ( predictedDepth < 2 * ONE_PLY - && bestValue > VALUE_MATED_IN_PLY_MAX && pos.see_sign(move) < 0) { if (SpNode) @@ -1134,51 +1069,44 @@ split_point_start: // At split points actual search starts from here // Step 14. Make the move pos.do_move(move, st, ci, givesCheck); - // Step extra. pv search (only in PV nodes) - // The first move in list is the expected PV - if (isPvMove) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth); - else + // Step 15. Reduced depth search (LMR). If the move fails high will be + // re-searched at full depth. + if ( depth > 3 * ONE_PLY + && !isPvMove + && !captureOrPromotion + && !dangerous + && !is_castle(move) + && ss->killers[0] != move + && ss->killers[1] != move) { - // Step 15. Reduced depth search - // If the move fails high will be re-searched at full depth. - bool doFullDepthSearch = true; - - if ( depth > 3 * ONE_PLY - && !captureOrPromotion - && !dangerous - && !is_castle(move) - && ss->killers[0] != move - && ss->killers[1] != move - && (ss->reduction = reduction(depth, moveCount)) != DEPTH_ZERO) - { - Depth d = newDepth - ss->reduction; - alpha = SpNode ? sp->alpha : alpha; + ss->reduction = reduction(depth, moveCount); + Depth d = newDepth - ss->reduction; + alpha = SpNode ? sp->alpha : alpha; - value = d < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, d); + value = d < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, d); - ss->reduction = DEPTH_ZERO; - doFullDepthSearch = (value > alpha); - } + doFullDepthSearch = (value > alpha && ss->reduction != DEPTH_ZERO); + ss->reduction = DEPTH_ZERO; + } + else + doFullDepthSearch = !isPvMove; - // Step 16. Full depth search - if (doFullDepthSearch) - { - alpha = SpNode ? sp->alpha : alpha; - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); - - // Step extra. pv search (only in PV nodes) - // Search only for possible new PV nodes, if instead value >= beta then - // parent node fails low with value <= alpha and tries another move. - if (PvNode && value > alpha && (RootNode || value < beta)) - value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) - : - search(pos, ss+1, -beta, -alpha, newDepth); - } + // Step 16. Full depth search, when LMR is skipped or fails high + if (doFullDepthSearch) + { + alpha = SpNode ? sp->alpha : alpha; + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -(alpha+1), -alpha, newDepth); } + // Only for PV nodes do a full PV search on the first move or after a fail + // high, in the latter case search only if value < beta, otherwise let the + // parent node to fail low with value <= alpha and to try another move. + if (PvNode && (isPvMove || (value > alpha && (RootNode || value < beta)))) + value = newDepth < ONE_PLY ? -qsearch(pos, ss+1, -beta, -alpha, DEPTH_ZERO) + : - search(pos, ss+1, -beta, -alpha, newDepth); + // Step 17. Undo move pos.undo_move(move); @@ -1196,16 +1124,14 @@ split_point_start: // At split points actual search starts from here // was aborted because the user interrupted the search or because we // ran out of time. In this case, the return value of the search cannot // be trusted, and we don't update the best move and/or PV. - if (RootNode && !StopRequest) + if (RootNode && !Signals.stop) { - // Remember searched nodes counts for this move RootMove* rm = Rml.find(move); rm->nodes += pos.nodes_searched() - nodes; // PV move or new best move ? if (isPvMove || value > alpha) { - // Update PV rm->score = value; rm->extract_pv_from_tt(pos); @@ -1221,7 +1147,7 @@ split_point_start: // At split points actual search starts from here // position in the list is preserved, just the PV is pushed up. rm->score = -VALUE_INFINITE; - } // RootNode + } if (value > bestValue) { @@ -1247,7 +1173,7 @@ split_point_start: // At split points actual search starts from here && depth >= Threads.min_split_depth() && bestValue < beta && Threads.available_slave_exists(pos.thread()) - && !StopRequest + && !Signals.stop && !thread.cutoff_occurred()) bestValue = Threads.split(pos, ss, alpha, beta, bestValue, depth, threatMove, moveCount, &mp, NT); @@ -1259,13 +1185,20 @@ split_point_start: // At split points actual search starts from here // case of StopRequest or thread.cutoff_occurred() are set, but this is // harmless because return value is discarded anyhow in the parent nodes. // If we are in a singular extension search then return a fail low score. - if (!SpNode && !moveCount) + if (!moveCount) return excludedMove ? oldAlpha : inCheck ? value_mated_in(ss->ply) : VALUE_DRAW; + // If we have pruned all the moves without searching return a fail-low score + if (bestValue == -VALUE_INFINITE) + { + assert(!playedMoveCount); + + bestValue = alpha; + } + // Step 21. Update tables - // If the search is not aborted, update the transposition table, - // history counters, and killer moves. - if (!SpNode && !StopRequest && !thread.cutoff_occurred()) + // Update transposition table entry, history and killers + if (!SpNode && !Signals.stop && !thread.cutoff_occurred()) { move = bestValue <= oldAlpha ? MOVE_NONE : ss->bestMove; vt = bestValue <= oldAlpha ? VALUE_TYPE_UPPER @@ -1299,12 +1232,13 @@ split_point_start: // At split points actual search starts from here return bestValue; } + // qsearch() is the quiescence search function, which is called by the main // search function when the remaining depth is zero (or, to be more precise, // less than ONE_PLY). template - Value qsearch(Position& pos, SearchStack* ss, Value alpha, Value beta, Depth depth) { + Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { const bool PvNode = (NT == PV); @@ -1379,7 +1313,6 @@ split_point_start: // At split points actual search starts from here if (PvNode && bestValue > alpha) alpha = bestValue; - // Futility pruning parameters, not needed when in check futilityBase = ss->eval + evalMargin + FutilityMarginQS; enoughMaterial = pos.non_pawn_material(pos.side_to_move()) > RookValueMidgame; } @@ -1461,7 +1394,6 @@ split_point_start: // At split points actual search starts from here if (!pos.pl_move_is_legal(move, ci.pinned)) continue; - // Update current move ss->currentMove = move; // Make and search the move @@ -1682,8 +1614,8 @@ split_point_start: // At split points actual search starts from here } - // can_return_tt() returns true if a transposition table score - // can be used to cut-off at a given point in search. + // can_return_tt() returns true if a transposition table score can be used to + // cut-off at a given point in search. bool can_return_tt(const TTEntry* tte, Depth depth, Value beta, int ply) { @@ -1698,8 +1630,8 @@ split_point_start: // At split points actual search starts from here } - // refine_eval() returns the transposition table score if - // possible otherwise falls back on static position evaluation. + // refine_eval() returns the transposition table score if possible, otherwise + // falls back on static position evaluation. Value refine_eval(const TTEntry* tte, Value defaultEval, int ply) { @@ -1715,8 +1647,8 @@ split_point_start: // At split points actual search starts from here } - // update_history() registers a good move that produced a beta-cutoff - // in history and marks as failures all the other moves of that ply. + // update_history() registers a good move that produced a beta-cutoff in + // history and marks as failures all the other moves of that ply. void update_history(const Position& pos, Move move, Depth depth, Move movesSearched[], int moveCount) { @@ -1739,12 +1671,12 @@ split_point_start: // At split points actual search starts from here // current_search_time() returns the number of milliseconds which have passed // since the beginning of the current search. - int elapsed_search_time(int set) { + int elapsed_time(bool reset) { static int searchStartTime; - if (set) - searchStartTime = set; + if (reset) + searchStartTime = get_system_time(); return get_system_time() - searchStartTime; } @@ -1778,7 +1710,7 @@ split_point_start: // At split points actual search starts from here string speed_to_uci(int64_t nodes) { std::stringstream s; - int t = elapsed_search_time(); + int t = elapsed_time(); s << " nodes " << nodes << " nps " << (t > 0 ? int(nodes * 1000 / t) : 0) @@ -1822,6 +1754,12 @@ split_point_start: // At split points actual search starts from here return s.str(); } + + // pretty_pv() creates a human-readable string from a position and a PV. + // It is used to write search information to the log file (which is created + // when the UCI parameter "Use Search Log" is "true"). It uses the two helpers + // time_to_string() and score_to_string() to format time and score respectively. + string time_to_string(int millisecs) { const int MSecMinute = 1000 * 60; @@ -1854,11 +1792,6 @@ split_point_start: // At split points actual search starts from here return s.str(); } - - // pretty_pv() creates a human-readable string from a position and a PV. - // It is used to write search information to the log file (which is created - // when the UCI parameter "Use Search Log" is "true"). - string pretty_pv(Position& pos, int depth, Value value, int time, Move pv[]) { const int64_t K = 1000; @@ -1908,26 +1841,6 @@ split_point_start: // At split points actual search starts from here } - // wait_for_stop_or_ponderhit() is called when the maximum depth is reached - // while the program is pondering. The point is to work around a wrinkle in - // the UCI protocol: When pondering, the engine is not allowed to give a - // "bestmove" before the GUI sends it a "stop" or "ponderhit" command. - // We simply wait here until one of these commands (that raise StopRequest) is - // sent, and return, after which the bestmove and pondermove will be printed. - - void wait_for_stop_or_ponderhit() { - - string cmd; - StopOnPonderhit = true; - - while (!StopRequest) - { - Threads.getline(cmd); - do_uci_async_cmd(cmd); - } - } - - // When playing with strength handicap choose best move among the MultiPV set // using a statistical rule dependent on SkillLevel. Idea by Heinz van Saanen. @@ -1939,8 +1852,8 @@ split_point_start: // At split points actual search starts from here // Rml list is already sorted by score in descending order int s; + size_t size = std::min(MultiPV, Rml.size()); int max_s = -VALUE_INFINITE; - int size = std::min(MultiPV, (int)Rml.size()); int max = Rml[0].score; int var = std::min(max - Rml[size - 1].score, int(PawnValueMidgame)); int wk = 120 - 2 * SkillLevel; @@ -1952,7 +1865,7 @@ split_point_start: // At split points actual search starts from here // Choose best move. For each move's score we add two terms both dependent // on wk, one deterministic and bigger for weaker moves, and one random, // then we choose the move with the resulting highest score. - for (int i = 0; i < size; i++) + for (size_t i = 0; i < size; i++) { s = Rml[i].score; @@ -1973,9 +1886,9 @@ split_point_start: // At split points actual search starts from here } - /// RootMove and RootMoveList method's definitions + // RootMove and RootMoveList method's definitions - void RootMoveList::init(Position& pos, Move searchMoves[]) { + void RootMoveList::init(Position& pos, Move rootMoves[]) { Move* sm; bestMoveChanges = 0; @@ -1984,11 +1897,11 @@ split_point_start: // At split points actual search starts from here // Generate all legal moves and add them to RootMoveList for (MoveList ml(pos); !ml.end(); ++ml) { - // If we have a searchMoves[] list then verify the move + // If we have a rootMoves[] list then verify the move // is in the list before to add it. - for (sm = searchMoves; *sm && *sm != ml.move(); sm++) {} + for (sm = rootMoves; *sm && *sm != ml.move(); sm++) {} - if (sm != searchMoves && *sm != ml.move()) + if (sm != rootMoves && *sm != ml.move()) continue; RootMove rm; @@ -2079,9 +1992,9 @@ split_point_start: // At split points actual search starts from here } // namespace -// Thread::idle_loop() is where the thread is parked when it has no work to do. -// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object -// for which the thread is the master. +/// Thread::idle_loop() is where the thread is parked when it has no work to do. +/// The parameter 'sp', if non-NULL, is a pointer to an active SplitPoint object +/// for which the thread is the master. void Thread::idle_loop(SplitPoint* sp) { @@ -2095,7 +2008,6 @@ void Thread::idle_loop(SplitPoint* sp) { { assert((!sp && threadID) || Threads.use_sleeping_threads()); - // Slave thread should exit as soon as do_terminate flag raises if (do_terminate) { assert(!sp); @@ -2128,11 +2040,11 @@ void Thread::idle_loop(SplitPoint* sp) { assert(!do_terminate); // Copy split point position and search stack and call search() - SearchStack ss[PLY_MAX_PLUS_2]; + Stack ss[PLY_MAX_PLUS_2]; SplitPoint* tsp = splitPoint; Position pos(*tsp->pos, threadID); - memcpy(ss, tsp->ss - 1, 4 * sizeof(SearchStack)); + memcpy(ss, tsp->ss - 1, 4 * sizeof(Stack)); (ss+1)->sp = tsp; if (tsp->nodeType == Root) @@ -2170,39 +2082,16 @@ void Thread::idle_loop(SplitPoint* sp) { } -// do_uci_async_cmd() is called by listener thread when in async mode and 'cmd' -// input line is received from the GUI. - -void do_uci_async_cmd(const std::string& cmd) { - - if (cmd == "quit") - QuitRequest = StopRequest = true; - - else if (cmd == "stop") - StopRequest = true; - - else if (cmd == "ponderhit") - { - // The opponent has played the expected move. GUI sends "ponderhit" if - // we were told to ponder on the same move the opponent has played. We - // should continue searching but switching from pondering to normal search. - Limits.ponder = false; - - if (StopOnPonderhit) - StopRequest = true; - } -} - - -// do_timer_event() is called by the timer thread when the timer triggers +/// do_timer_event() is called by the timer thread when the timer triggers. It +/// is used to print debug info and, more important, to detect when we are out of +/// available time and so stop the search. void do_timer_event() { static int lastInfoTime; - int e = elapsed_search_time(); + int e = elapsed_time(); - // Print debug information every one second - if (!lastInfoTime || get_system_time() - lastInfoTime >= 1000) + if (get_system_time() - lastInfoTime >= 1000 || !lastInfoTime) { lastInfoTime = get_system_time(); @@ -2210,12 +2099,11 @@ void do_timer_event() { dbg_print_hit_rate(); } - // Should we stop the search? if (Limits.ponder) return; - bool stillAtFirstMove = FirstRootMove - && !AspirationFailLow + bool stillAtFirstMove = Signals.firstRootMove + && !Signals.failedLowAtRoot && e > TimeMgr.available_time(); bool noMoreTime = e > TimeMgr.maximum_time() @@ -2224,5 +2112,5 @@ void do_timer_event() { if ( (Limits.useTimeManagement() && noMoreTime) || (Limits.maxTime && e >= Limits.maxTime) /* missing nodes limit */ ) // FIXME - StopRequest = true; + Signals.stop = true; }