X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=651bd95b6feff4ceecc70840ef82fb37bafbb86d;hp=756b2d5769fb6f44b854cad829f9e1b1242746ef;hb=9050eac59564fe96b3f24d2889bbef7336b28100;hpb=0f2df4e4afa37946e02a2b647ff21146e0588af7 diff --git a/src/search.cpp b/src/search.cpp index 756b2d57..651bd95b 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(); @@ -227,10 +227,9 @@ void MainThread::search() { // Threads.stop. However, if we are pondering or in an infinite search, // the UCI protocol states that we shouldn't print the best move before the // GUI sends a "stop" or "ponderhit" command. We therefore simply wait here - // until the GUI sends one of those commands (which also raises Threads.stop). - Threads.stopOnPonderhit = true; + // until the GUI sends one of those commands. - while (!Threads.stop && (Threads.ponder || Limits.infinite)) + while (!Threads.stop && (ponder || Limits.infinite)) {} // Busy wait for a stop or a ponder reset // Stop the threads if not already stopped (also raise the stop if @@ -303,7 +302,11 @@ 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 +316,8 @@ 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; @@ -444,7 +447,7 @@ void Thread::search() { { failedHighCnt = 0; failedLow = true; - Threads.stopOnPonderhit = false; + mainThread->stopOnPonderhit = false; } } else if (bestValue >= beta) @@ -493,33 +496,30 @@ void Thread::search() { // Do we have time for the next iteration? Can we stop searching now? if ( Limits.use_time_management() && !Threads.stop - && !Threads.stopOnPonderhit) + && !mainThread->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 = lastBestMoveDepth + 10 * ONE_PLY < completedDepth ? 1.95 : 1.0; + + // 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 (mainThread->ponder) + mainThread->stopOnPonderhit = true; + else + Threads.stop = true; } + } } if (!mainThread) @@ -573,8 +573,8 @@ namespace { Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; Value bestValue, value, ttValue, eval, maxValue, pureStaticEval; - bool ttHit, inCheck, givesCheck, improving; - bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture, pvExact; + bool ttHit, pvHit, inCheck, givesCheck, improving; + bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture; Piece movedPiece; int moveCount, captureCount, quietCount; @@ -639,6 +639,7 @@ namespace { ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; + pvHit = (ttHit && tte->pv_hit()) || (PvNode && depth > 4 * ONE_PLY); // At non-PV nodes we check for an early TT cutoff if ( !PvNode @@ -657,9 +658,8 @@ namespace { update_quiet_stats(pos, ss, ttMove, nullptr, 0, stat_bonus(depth)); // 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)); } // Penalty for a quiet ttMove that fails low @@ -706,7 +706,7 @@ namespace { if ( b == BOUND_EXACT || (b == BOUND_LOWER ? value >= beta : value <= alpha)) { - tte->save(posKey, value_to_tt(value, ss->ply), b, + tte->save(posKey, value_to_tt(value, ss->ply), pvHit, b, std::min(DEPTH_MAX - ONE_PLY, depth + 6 * ONE_PLY), MOVE_NONE, VALUE_NONE); @@ -747,9 +747,7 @@ namespace { { if ((ss-1)->currentMove != MOVE_NULL) { - int p = (ss-1)->statScore; - int bonus = p > 0 ? (-p - 2500) / 512 : - p < 0 ? (-p + 2500) / 512 : 0; + int bonus = -(ss-1)->statScore / 512; pureStaticEval = evaluate(pos); ss->staticEval = eval = pureStaticEval + bonus; @@ -757,7 +755,7 @@ namespace { else ss->staticEval = eval = pureStaticEval = -(ss-1)->staticEval + 2 * Eval::Tempo; - tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval); + tte->save(posKey, VALUE_NONE, pvHit, BOUND_NONE, DEPTH_NONE, MOVE_NONE, pureStaticEval); } // Step 7. Razoring (~2 Elo) @@ -888,7 +886,6 @@ moves_loop: // When in check, search starts from here skipQuiets = false; ttCapture = ttMove && pos.capture_or_promotion(ttMove); - pvExact = PvNode && ttHit && tte->bound() == BOUND_EXACT; // Step 12. Loop through all pseudo-legal moves until no moves remain // or a beta cutoff occurs. @@ -940,19 +937,29 @@ 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)) + + // Check extension (~2 Elo) + else if ( givesCheck + && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move))) extension = ONE_PLY; - // Extension if castling + // Castling extension else if (type_of(move) == CASTLING) extension = ONE_PLY; @@ -1024,16 +1031,16 @@ moves_loop: // When in check, search starts from here { Depth r = reduction(improving, depth, moveCount); + // Decrease reduction if position is or has been on the PV + if (pvHit) + r -= ONE_PLY; + // Decrease reduction if opponent's move count is high (~10 Elo) if ((ss-1)->moveCount > 15) r -= ONE_PLY; if (!captureOrPromotion) { - // Decrease reduction for exact PV nodes (~0 Elo) - if (pvExact) - r -= ONE_PLY; - // Increase reduction if ttMove is a capture (~0 Elo) if (ttCapture) r += ONE_PLY; @@ -1192,23 +1199,21 @@ 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) bestValue = std::min(bestValue, maxValue); if (!excludedMove) - tte->save(posKey, value_to_tt(bestValue, ss->ply), + tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, bestValue >= beta ? BOUND_LOWER : PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER, depth, bestMove, pureStaticEval); @@ -1238,7 +1243,7 @@ moves_loop: // When in check, search starts from here Move ttMove, move, bestMove; Depth ttDepth; Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; - bool ttHit, inCheck, givesCheck, evasionPrunable; + bool ttHit, pvHit, inCheck, givesCheck, evasionPrunable; int moveCount; if (PvNode) @@ -1272,6 +1277,7 @@ moves_loop: // When in check, search starts from here tte = TT.probe(posKey, ttHit); ttValue = ttHit ? value_from_tt(tte->value(), ss->ply) : VALUE_NONE; ttMove = ttHit ? tte->move() : MOVE_NONE; + pvHit = ttHit && tte->pv_hit(); if ( !PvNode && ttHit @@ -1309,7 +1315,7 @@ moves_loop: // When in check, search starts from here if (bestValue >= beta) { if (!ttHit) - tte->save(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, + tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, BOUND_LOWER, DEPTH_NONE, MOVE_NONE, ss->staticEval); return bestValue; @@ -1420,7 +1426,7 @@ moves_loop: // When in check, search starts from here if (inCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root - tte->save(posKey, value_to_tt(bestValue, ss->ply), + tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, bestValue >= beta ? BOUND_LOWER : PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, ttDepth, bestMove, ss->staticEval); @@ -1480,7 +1486,7 @@ 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); @@ -1490,7 +1496,7 @@ 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]))); @@ -1502,7 +1508,7 @@ 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) { @@ -1522,7 +1528,7 @@ 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); @@ -1587,10 +1593,10 @@ void MainThread::check_time() { } // We should not stop pondering until told so by the GUI - if (Threads.ponder) + if (ponder) return; - if ( (Limits.use_time_management() && elapsed > Time.maximum() - 10) + if ( (Limits.use_time_management() && (elapsed > Time.maximum() - 10 || stopOnPonderhit)) || (Limits.movetime && elapsed >= Limits.movetime) || (Limits.nodes && Threads.nodes_searched() >= (uint64_t)Limits.nodes)) Threads.stop = true; @@ -1665,7 +1671,7 @@ 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);