X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=b2c2344ac0aaff10a249bfb7f64a22fa0e648d6f;hb=e1dd005583bd6c2aaf58468efc5de86a3936380a;hp=5205fb5729b5799e96310b70682607fdac73ce03;hpb=7b9b793fd544aa7a599b113a40533cde16de640b;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index 5205fb57..b2c2344a 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -64,7 +64,7 @@ namespace { // Futility margin Value futility_margin(Depth d, bool improving) { - return Value(154 * (d - improving)); + return Value(140 * (d - improving)); } // Reductions lookup table, initialized at startup @@ -72,7 +72,7 @@ namespace { Depth reduction(bool i, Depth d, int mn, Value delta, Value rootDelta) { int r = Reductions[d] * Reductions[mn]; - return (r + 1449 - int(delta) * 937 / int(rootDelta)) / 1024 + (!i && r > 941); + return (r + 1372 - int(delta) * 1073 / int(rootDelta)) / 1024 + (!i && r > 936); } constexpr int futility_move_count(bool improving, Depth depth) { @@ -82,7 +82,7 @@ namespace { // History and stats update bonus, based on depth int stat_bonus(Depth d) { - return std::min(341 * d - 470, 1710); + return std::min(336 * d - 547, 1561); } // Add a small random component to draw evaluations to avoid 3-fold blindness @@ -162,7 +162,7 @@ namespace { void Search::init() { for (int i = 1; i < MAX_MOVES; ++i) - Reductions[i] = int((19.47 + std::log(Threads.size()) / 2) * std::log(i)); + Reductions[i] = int((20.57 + std::log(Threads.size()) / 2) * std::log(i)); } @@ -288,9 +288,7 @@ void Thread::search() { ss->pv = pv; - bestValue = delta = alpha = -VALUE_INFINITE; - beta = VALUE_INFINITE; - optimism[WHITE] = optimism[BLACK] = VALUE_ZERO; + bestValue = -VALUE_INFINITE; if (mainThread) { @@ -349,18 +347,15 @@ void Thread::search() { selDepth = 0; // Reset aspiration window starting size - if (rootDepth >= 4) - { - Value prev = rootMoves[pvIdx].averageScore; - delta = Value(10) + int(prev) * prev / 16502; - alpha = std::max(prev - delta,-VALUE_INFINITE); - beta = std::min(prev + delta, VALUE_INFINITE); - - // Adjust optimism based on root move's previousScore - int opt = 120 * prev / (std::abs(prev) + 161); - optimism[ us] = Value(opt); - optimism[~us] = -optimism[us]; - } + Value prev = rootMoves[pvIdx].averageScore; + delta = Value(10) + int(prev) * prev / 15799; + alpha = std::max(prev - delta,-VALUE_INFINITE); + beta = std::min(prev + delta, VALUE_INFINITE); + + // Adjust optimism based on root move's previousScore + int opt = 109 * prev / (std::abs(prev) + 141); + optimism[ us] = Value(opt); + optimism[~us] = -optimism[us]; // Start with a small aspiration window and, in the case of a fail // high/low, re-search with a bigger window until we don't fail @@ -414,7 +409,7 @@ void Thread::search() { else break; - delta += delta / 4 + 2; + delta += delta / 3; assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE); } @@ -620,10 +615,9 @@ namespace { // At non-PV nodes we check for an early TT cutoff if ( !PvNode - && ss->ttHit && !excludedMove && tte->depth() > depth - (tte->bound() == BOUND_EXACT) - && ttValue != VALUE_NONE // Possible in case of TT access race + && ttValue != VALUE_NONE // Possible in case of TT access race or if !ttHit && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER))) { // If ttMove is quiet, update move sorting heuristics on TT hit (~2 Elo) @@ -729,11 +723,8 @@ namespace { ss->staticEval = eval = tte->eval(); if (eval == VALUE_NONE) ss->staticEval = eval = evaluate(pos); - else - { - if (PvNode) - Eval::NNUE::hint_common_parent_position(pos); - } + else if (PvNode) + Eval::NNUE::hint_common_parent_position(pos); // ttValue can be used as a better position evaluation (~7 Elo) if ( ttValue != VALUE_NONE @@ -750,7 +741,7 @@ namespace { // Use static evaluation difference to improve quiet move ordering (~4 Elo) if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture) { - int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1920, 1920); + int bonus = std::clamp(-18 * int((ss-1)->staticEval + ss->staticEval), -1817, 1817); thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus; } @@ -760,13 +751,13 @@ namespace { // margin and the improving flag are used in various pruning heuristics. improvement = (ss-2)->staticEval != VALUE_NONE ? ss->staticEval - (ss-2)->staticEval : (ss-4)->staticEval != VALUE_NONE ? ss->staticEval - (ss-4)->staticEval - : 156; + : 173; improving = improvement > 0; // Step 7. Razoring (~1 Elo). // If eval is really low check with qsearch if it can exceed alpha, if it can't, // return a fail low. - if (eval < alpha - 426 - 256 * depth * depth) + if (eval < alpha - 456 - 252 * depth * depth) { value = qsearch(pos, ss, alpha - 1, alpha); if (value < alpha) @@ -777,18 +768,18 @@ namespace { // The depth condition is important for mate finding. if ( !ss->ttPv && depth < 9 - && eval - futility_margin(depth, improving) - (ss-1)->statScore / 280 >= beta + && eval - futility_margin(depth, improving) - (ss-1)->statScore / 306 >= beta && eval >= beta - && eval < 25128) // larger than VALUE_KNOWN_WIN, but smaller than TB wins + && eval < 24923) // larger than VALUE_KNOWN_WIN, but smaller than TB wins return eval; // Step 9. Null move search with verification search (~35 Elo) if ( !PvNode && (ss-1)->currentMove != MOVE_NULL - && (ss-1)->statScore < 18755 + && (ss-1)->statScore < 17329 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 20 * depth - improvement / 13 + 253 + && ss->staticEval >= beta - 21 * depth - improvement / 13 + 258 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly)) @@ -796,7 +787,7 @@ namespace { assert(eval - beta >= 0); // Null move dynamic reduction based on depth and eval - Depth R = std::min(int(eval - beta) / 172, 6) + depth / 3 + 4; + Depth R = std::min(int(eval - beta) / 173, 6) + depth / 3 + 4; ss->currentMove = MOVE_NULL; ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0]; @@ -831,20 +822,34 @@ namespace { } } - probCutBeta = beta + 186 - 54 * improving; + // Step 10. If the position doesn't a have ttMove, decrease depth by 2 + // (or by 4 if the TT entry for the current position was hit and the stored depth is greater than or equal to the current depth). + // Use qsearch if depth is equal or below zero (~9 Elo) + if ( PvNode + && !ttMove) + depth -= 2 + 2 * (ss->ttHit && tte->depth() >= depth); + + if (depth <= 0) + return qsearch(pos, ss, alpha, beta); + + if ( cutNode + && depth >= 8 + && !ttMove) + depth -= 2; + + probCutBeta = beta + 168 - 61 * improving; - // Step 10. ProbCut (~10 Elo) + // Step 11. ProbCut (~10 Elo) // If we have a good enough capture (or queen promotion) and a reduced search returns a value // much above beta, we can (almost) safely prune the previous move. if ( !PvNode - && depth > 4 + && depth > 3 && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY // if value from transposition table is lower than probCutBeta, don't attempt probCut // there and in further interactions with transposition table cutoff depth is set to depth - 3 // because probCut search has depth set to depth - 4 but we also do a move before it // so effective depth is equal to depth - 3 - && !( ss->ttHit - && tte->depth() >= depth - 3 + && !( tte->depth() >= depth - 3 && ttValue != VALUE_NONE && ttValue < probCutBeta)) { @@ -885,30 +890,15 @@ namespace { Eval::NNUE::hint_common_parent_position(pos); } - // Step 11. If the position is not in TT, decrease depth by 2 (or by 4 if the TT entry for the current position was hit and the stored depth is greater than or equal to the current depth). - // Use qsearch if depth is equal or below zero (~9 Elo) - if ( PvNode - && !ttMove) - depth -= 2 + 2 * (ss->ttHit && tte->depth() >= depth); - - if (depth <= 0) - return qsearch(pos, ss, alpha, beta); - - if ( cutNode - && depth >= 7 - && !ttMove) - depth -= 2; - moves_loop: // When in check, search starts here // Step 12. A small Probcut idea, when we are in check (~4 Elo) - probCutBeta = beta + 391; + probCutBeta = beta + 413; if ( ss->inCheck && !PvNode - && depth >= 2 && ttCapture && (tte->bound() & BOUND_LOWER) - && tte->depth() >= depth - 3 + && tte->depth() >= depth - 4 && ttValue >= probCutBeta && abs(ttValue) <= VALUE_KNOWN_WIN && abs(beta) <= VALUE_KNOWN_WIN) @@ -987,39 +977,40 @@ moves_loop: // When in check, search starts here moveCountPruning = moveCount >= futility_move_count(improving, depth); // Reduced depth of the next LMR search - int lmrDepth = std::max(newDepth - r, 0); + int lmrDepth = newDepth - r; if ( capture || givesCheck) { // Futility pruning for captures (~2 Elo) if ( !givesCheck - && lmrDepth < 6 + && lmrDepth < 7 && !ss->inCheck - && ss->staticEval + 182 + 230 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))] + && ss->staticEval + 197 + 248 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))] + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 7 < alpha) continue; Bitboard occupied; // SEE based pruning (~11 Elo) - if (!pos.see_ge(move, occupied, Value(-206) * depth)) + if (!pos.see_ge(move, occupied, Value(-205) * depth)) { - if (depth < 2 - capture) - continue; - // Don't prune the move if opp. King/Queen/Rook gets a discovered attack during or after the exchanges - Bitboard leftEnemies = pos.pieces(~us, KING, QUEEN, ROOK); - Bitboard attacks = 0; - occupied |= to_sq(move); - while (leftEnemies && !attacks) - { + if (depth < 2 - capture) + continue; + // Don't prune the move if opponent Queen/Rook is under discovered attack after the exchanges + // Don't prune the move if opponent King is under discovered attack after or during the exchanges + Bitboard leftEnemies = (pos.pieces(~us, KING, QUEEN, ROOK)) & occupied; + Bitboard attacks = 0; + occupied |= to_sq(move); + while (leftEnemies && !attacks) + { Square sq = pop_lsb(leftEnemies); - attacks = pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied; - // Exclude Queen/Rook(s) which were already threatened before SEE (opp King can't be in check when it's our turn) - if (attacks && sq != pos.square(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us))) - attacks = 0; - } - if (!attacks) - continue; + attacks |= pos.attackers_to(sq, occupied) & pos.pieces(us) & occupied; + // don't consider pieces which were already threatened/hanging before SEE exchanges + if (attacks && (sq != pos.square(~us) && (pos.attackers_to(sq, pos.pieces()) & pos.pieces(us)))) + attacks = 0; + } + if (!attacks) + continue; } } else @@ -1029,25 +1020,25 @@ moves_loop: // When in check, search starts here + (*contHist[3])[movedPiece][to_sq(move)]; // Continuation history based pruning (~2 Elo) - if ( lmrDepth < 5 - && history < -4405 * (depth - 1)) + if ( lmrDepth < 6 + && history < -3832 * depth) continue; history += 2 * thisThread->mainHistory[us][from_to(move)]; - lmrDepth += history / 7278; + lmrDepth += history / 7011; lmrDepth = std::max(lmrDepth, -2); // Futility pruning: parent node (~13 Elo) if ( !ss->inCheck - && lmrDepth < 13 - && ss->staticEval + 103 + 138 * lmrDepth <= alpha) + && lmrDepth < 12 + && ss->staticEval + 112 + 138 * lmrDepth <= alpha) continue; lmrDepth = std::max(lmrDepth, 0); // Prune moves with negative SEE (~4 Elo) - if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 16 * lmrDepth))) + if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth))) continue; } } @@ -1062,7 +1053,7 @@ moves_loop: // When in check, search starts here // a reduced search on all the other moves but the ttMove and if the // result is lower than ttValue minus a margin, then we will extend the ttMove. if ( !rootNode - && depth >= 4 - (thisThread->completedDepth > 21) + 2 * (PvNode && tte->is_pv()) + && depth >= 4 - (thisThread->completedDepth > 22) + 2 * (PvNode && tte->is_pv()) && move == ttMove && !excludedMove // Avoid recursive singular search /* && ttValue != VALUE_NONE Already implicit in the next condition */ @@ -1070,7 +1061,7 @@ moves_loop: // When in check, search starts here && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3) { - Value singularBeta = ttValue - (3 + 2 * (ss->ttPv && !PvNode)) * depth / 2; + Value singularBeta = ttValue - (82 + 65 * (ss->ttPv && !PvNode)) * depth / 64; Depth singularDepth = (depth - 1) / 2; ss->excludedMove = move; @@ -1084,8 +1075,8 @@ moves_loop: // When in check, search starts here // Avoid search explosion by limiting the number of double extensions if ( !PvNode - && value < singularBeta - 25 - && ss->doubleExtensions <= 10) + && value < singularBeta - 21 + && ss->doubleExtensions <= 11) { extension = 2; depth += depth < 13; @@ -1115,15 +1106,14 @@ moves_loop: // When in check, search starts here // Check extensions (~1 Elo) else if ( givesCheck - && depth > 10 - && abs(ss->staticEval) > 88) + && depth > 9) extension = 1; // Quiet ttMove extensions (~1 Elo) else if ( PvNode && move == ttMove && move == ss->killers[0] - && (*contHist[0])[movedPiece][to_sq(move)] >= 5705) + && (*contHist[0])[movedPiece][to_sq(move)] >= 5168) extension = 1; } @@ -1146,12 +1136,13 @@ moves_loop: // When in check, search starts here // Decrease reduction if position is or has been on the PV // and node is not likely to fail low. (~3 Elo) + // Decrease further on cutNodes. (~1 Elo) if ( ss->ttPv && !likelyFailLow) - r -= 2; + r -= cutNode && tte->depth() >= depth + 3 ? 3 : 2; // Decrease reduction if opponent's move count is high (~1 Elo) - if ((ss-1)->moveCount > 7) + if ((ss-1)->moveCount > 8) r--; // Increase reduction for cut nodes (~3 Elo) @@ -1174,14 +1165,17 @@ moves_loop: // When in check, search starts here if ((ss+1)->cutoffCnt > 3) r++; + else if (move == ttMove) + r--; + ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)] + (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)] - - 4082; + - 4006; // Decrease/increase reduction for moves with a good/bad history (~25 Elo) - r -= ss->statScore / (11079 + 4626 * (depth > 6 && depth < 19)); + r -= ss->statScore / (11124 + 4740 * (depth > 5 && depth < 22)); // Step 17. Late moves reduction / extension (LMR, ~117 Elo) // We use various heuristics for the sons of a node after the first son has @@ -1205,8 +1199,8 @@ moves_loop: // When in check, search starts here { // Adjust full depth search based on LMR results - if result // was good enough search deeper, if it was bad enough search shallower - const bool doDeeperSearch = value > (alpha + 58 + 12 * (newDepth - d)); - const bool doEvenDeeperSearch = value > alpha + 588 && ss->doubleExtensions <= 5; + const bool doDeeperSearch = value > (bestValue + 64 + 11 * (newDepth - d)); + const bool doEvenDeeperSearch = value > alpha + 711 && ss->doubleExtensions <= 6; const bool doShallowerSearch = value < bestValue + newDepth; ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch; @@ -1231,7 +1225,7 @@ moves_loop: // When in check, search starts here if (!ttMove && cutNode) r += 2; - value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode); + value = -search(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 3), !cutNode); } // For PV nodes only, do a full PV search on the first move or after a fail @@ -1314,22 +1308,23 @@ moves_loop: // When in check, search starts here if (PvNode && !rootNode) // Update pv even in fail-high case update_pv(ss->pv, move, (ss+1)->pv); - if (PvNode && value < beta) // Update alpha! Always alpha < beta + if (value >= beta) + { + ss->cutoffCnt += 1 + !ttMove; + assert(value >= beta); // Fail high + break; + } + else { // Reduce other moves if we have found at least one score improvement (~1 Elo) + // Reduce more for depth > 3 and depth < 12 (~1 Elo) if ( depth > 1 - && beta < 12535 - && value > -12535) - depth -= 1; + && beta < 14362 + && value > -12393) + depth -= depth > 3 && depth < 12 ? 2 : 1; assert(depth > 0); - alpha = value; - } - else - { - ss->cutoffCnt++; - assert(value >= beta); // Fail high - break; + alpha = value; // Update alpha! Always alpha < beta } } } @@ -1374,7 +1369,7 @@ moves_loop: // When in check, search starts here // Bonus for prior countermove that caused the fail low else if (!priorCapture && prevSq != SQ_NONE) { - int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 97 * depth) + ((ss-1)->moveCount > 10); + int bonus = (depth > 5) + (PvNode || cutNode) + (bestValue < alpha - 113 * depth) + ((ss-1)->moveCount > 12); update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * bonus); } @@ -1458,9 +1453,8 @@ moves_loop: // When in check, search starts here // At non-PV nodes we check for an early TT cutoff if ( !PvNode - && ss->ttHit && tte->depth() >= ttDepth - && ttValue != VALUE_NONE // Only in case of TT access race + && ttValue != VALUE_NONE // Only in case of TT access race or if !ttHit && (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER))) return ttValue; @@ -1503,7 +1497,7 @@ moves_loop: // When in check, search starts here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = bestValue + 168; + futilityBase = bestValue + 200; } const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, @@ -1514,7 +1508,7 @@ moves_loop: // When in check, search starts here // to search the moves. Because the depth is <= 0 here, only captures, // queen promotions, and other checks (only if depth >= DEPTH_QS_CHECKS) // will be generated. - Square prevSq = (ss-1)->currentMove != MOVE_NULL ? to_sq((ss-1)->currentMove) : SQ_NONE; + Square prevSq = is_ok((ss-1)->currentMove) ? to_sq((ss-1)->currentMove) : SQ_NONE; MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->captureHistory, contHist, @@ -1576,7 +1570,7 @@ moves_loop: // When in check, search starts here continue; // Do not search moves with bad enough SEE values (~5 Elo) - if (!pos.see_ge(move, Value(-110))) + if (!pos.see_ge(move, Value(-95))) continue; } @@ -1709,7 +1703,7 @@ moves_loop: // When in check, search starts here if (!pos.capture_stage(bestMove)) { - int bonus2 = bestValue > beta + 153 ? bonus1 // larger bonus + int bonus2 = bestValue > beta + 145 ? bonus1 // larger bonus : stat_bonus(depth); // smaller bonus // Increase stats for the best move in case it was a quiet move