X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=c8e6c8b653662256e6fcc9521c62a13350815b60;hp=02f40199938810008ac2618bdd94e0ed15353861;hb=f69106f7bb82f97ba07fb06a31395039d08af9f4;hpb=67ae53b020cbc604a817d249933973fbc9de866b diff --git a/src/search.cpp b/src/search.cpp index 02f40199..c8e6c8b6 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -113,8 +113,8 @@ namespace { Value value_from_tt(Value v, int ply); void update_pv(Move* pv, Move move, Move* childPv); void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus); - void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietsCnt, int bonus); - void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCnt, int bonus); + void update_quiet_stats(const Position& pos, Stack* ss, Move move, Move* quiets, int quietCount, int bonus); + void update_capture_stats(const Position& pos, Move move, Move* captures, int captureCount, int bonus); inline bool gives_check(const Position& pos, Move move) { Color us = pos.side_to_move(); @@ -303,7 +303,11 @@ void MainThread::search() { void Thread::search() { - Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2) + // To allow access to (ss-5) up to (ss+2), the stack must be oversized. + // The former is needed to allow update_continuation_histories(ss-1, ...), + // which accesses its argument at ss-4, also near the root. + // The latter is needed for statScores and killer initialization. + Stack stack[MAX_PLY+8], *ss = stack+5; Move pv[MAX_PLY+1]; Value bestValue, alpha, beta, delta; Move lastBestMove = MOVE_NONE; @@ -313,8 +317,8 @@ void Thread::search() { Color us = rootPos.side_to_move(); bool failedLow; - std::memset(ss-4, 0, 7 * sizeof(Stack)); - for (int i = 4; i > 0; i--) + std::memset(ss-5, 0, 8 * sizeof(Stack)); + for (int i = 5; i > 0; i--) (ss-i)->continuationHistory = &this->continuationHistory[NO_PIECE][0]; // Use as sentinel ss->pv = pv; @@ -494,32 +498,32 @@ void Thread::search() { if ( Limits.use_time_management() && !Threads.stop && !Threads.stopOnPonderhit) + { + double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0; + fallingEval = std::max(0.5, std::min(1.5, fallingEval)); + + // If the bestMove is stable over several iterations, reduce time accordingly + timeReduction = 1.0; + for (int i : {3, 4, 5}) + if (lastBestMoveDepth * i < completedDepth) + timeReduction *= 1.25; + + // Use part of the gained time from a previous stable move for the current move + double bestMoveInstability = 1.0 + mainThread->bestMoveChanges; + bestMoveInstability *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction; + + // Stop the search if we have only one legal move, or if available time elapsed + if ( rootMoves.size() == 1 + || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval) { - double fallingEval = (306 + 119 * failedLow + 6 * (mainThread->previousScore - bestValue)) / 581.0; - fallingEval = std::max(0.5, std::min(1.5, fallingEval)); - - // If the bestMove is stable over several iterations, reduce time accordingly - timeReduction = 1.0; - for (int i : {3, 4, 5}) - if (lastBestMoveDepth * i < completedDepth) - timeReduction *= 1.25; - - // Use part of the gained time from a previous stable move for the current move - double bestMoveInstability = 1.0 + mainThread->bestMoveChanges; - bestMoveInstability *= std::pow(mainThread->previousTimeReduction, 0.528) / timeReduction; - - // Stop the search if we have only one legal move, or if available time elapsed - if ( rootMoves.size() == 1 - || Time.elapsed() > Time.optimum() * bestMoveInstability * fallingEval) - { - // If we are allowed to ponder do not stop the search now but - // keep pondering until the GUI sends "ponderhit" or "stop". - if (Threads.ponder) - Threads.stopOnPonderhit = true; - else - Threads.stop = true; - } + // If we are allowed to ponder do not stop the search now but + // keep pondering until the GUI sends "ponderhit" or "stop". + if (Threads.ponder) + Threads.stopOnPonderhit = true; + else + Threads.stop = true; } + } } if (!mainThread) @@ -656,9 +660,10 @@ namespace { if (!pos.capture_or_promotion(ttMove)) update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); - // Extra penalty for a quiet TT move in previous ply when it gets refuted - if ((ss-1)->moveCount == 1 && !pos.captured_piece()) - update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); + // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted + if ( ((ss-1)->moveCount == 1 || (ss-1)->currentMove == (ss-1)->killers[0]) + && !pos.captured_piece()) + update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); } // Penalty for a quiet ttMove that fails low else if (!pos.capture_or_promotion(ttMove)) @@ -938,13 +943,21 @@ moves_loop: // When in check, search starts from here && tte->depth() >= depth - 3 * ONE_PLY && pos.legal(move)) { - Value reducedBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); + Value singularBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE); ss->excludedMove = move; - value = search(pos, ss, reducedBeta - 1, reducedBeta, depth / 2, cutNode); + value = search(pos, ss, singularBeta - 1, singularBeta, depth / 2, cutNode); ss->excludedMove = MOVE_NONE; - if (value < reducedBeta) + if (value < singularBeta) extension = ONE_PLY; + + // Multi-cut pruning + // Our ttMove is assumed to fail high, and now we failed high also on a reduced + // search without the ttMove. So we assume this expected Cut-node is not singular, + // that is multiple moves fail high, and we can prune the whole subtree by returning + // the hard beta bound. + else if (cutNode && singularBeta > beta) + return beta; } else if ( givesCheck // Check extension (~2 Elo) && pos.see_ge(move)) @@ -1190,16 +1203,14 @@ moves_loop: // When in check, search starts from here update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY)); // Extra penalty for a quiet TT or main killer move in previous ply when it gets refuted - if ( (ss-1)->moveCount == 1 - || ((ss-1)->currentMove == (ss-1)->killers[0] && (ss-1)->killers[0])) - if (!pos.captured_piece()) + if ( ((ss-1)->moveCount == 1 || ((ss-1)->currentMove == (ss-1)->killers[0])) + && !pos.captured_piece()) update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + ONE_PLY)); } // Bonus for prior countermove that caused the fail low else if ( (depth >= 3 * ONE_PLY || PvNode) - && !pos.captured_piece() - && is_ok((ss-1)->currentMove)) + && !pos.captured_piece()) update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); if (PvNode) @@ -1478,7 +1489,7 @@ moves_loop: // When in check, search starts from here // update_capture_stats() updates move sorting heuristics when a new capture best move is found void update_capture_stats(const Position& pos, Move move, - Move* captures, int captureCnt, int bonus) { + Move* captures, int captureCount, int bonus) { CapturePieceToHistory& captureHistory = pos.this_thread()->captureHistory; Piece moved_piece = pos.moved_piece(move); @@ -1488,7 +1499,7 @@ moves_loop: // When in check, search starts from here captureHistory[moved_piece][to_sq(move)][captured] << bonus; // Decrease all the other played capture moves - for (int i = 0; i < captureCnt; ++i) + for (int i = 0; i < captureCount; ++i) { moved_piece = pos.moved_piece(captures[i]); captured = type_of(pos.piece_on(to_sq(captures[i]))); @@ -1500,7 +1511,7 @@ moves_loop: // When in check, search starts from here // update_quiet_stats() updates move sorting heuristics when a new quiet best move is found void update_quiet_stats(const Position& pos, Stack* ss, Move move, - Move* quiets, int quietsCnt, int bonus) { + Move* quiets, int quietCount, int bonus) { if (ss->killers[0] != move) { @@ -1520,7 +1531,7 @@ moves_loop: // When in check, search starts from here } // Decrease all the other played quiet moves - for (int i = 0; i < quietsCnt; ++i) + for (int i = 0; i < quietCount; ++i) { thisThread->mainHistory[us][from_to(quiets[i])] << -bonus; update_continuation_histories(ss, pos.moved_piece(quiets[i]), to_sq(quiets[i]), -bonus); @@ -1663,7 +1674,7 @@ bool RootMove::extract_ponder_from_tt(Position& pos) { assert(pv.size() == 1); - if (!pv[0]) + if (pv[0] == MOVE_NONE) return false; pos.do_move(pv[0], st);