X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=740ad71efee01461cc40b5992c757f2caa4db81e;hb=48f7c74f15f4cae4b77596cd468802054314d701;hp=3632a46988419b62831981adec598210d919983b;hpb=b64c97825eb473d9b5cbdb67afe65a8ac0d5ec9f;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index 3632a469..740ad71e 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(148 * (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 + 1356 - int(delta) * 983 / int(rootDelta)) / 1024 + (!i && r > 901); + 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(337 * d - 497, 1632); + 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((20.89 + std::log(Threads.size()) / 2) * std::log(i)); + Reductions[i] = int((20.57 + std::log(Threads.size()) / 2) * std::log(i)); } @@ -348,12 +348,12 @@ void Thread::search() { // Reset aspiration window starting size Value prev = rootMoves[pvIdx].averageScore; - delta = Value(11) + int(prev) * prev / 15368; + 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 = 116 * prev / (std::abs(prev) + 143); + int opt = 109 * prev / (std::abs(prev) + 141); optimism[ us] = Value(opt); optimism[~us] = -optimism[us]; @@ -615,10 +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) @@ -742,7 +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), -1717, 1717); + int bonus = std::clamp(-18 * int((ss-1)->staticEval + ss->staticEval), -1817, 1817); thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus; } @@ -752,13 +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 - : 163; + : 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 - 467 - 266 * depth * depth) + if (eval < alpha - 456 - 252 * depth * depth) { value = qsearch(pos, ss, alpha - 1, alpha); if (value < alpha) @@ -771,16 +770,16 @@ namespace { && depth < 9 && eval - futility_margin(depth, improving) - (ss-1)->statScore / 306 >= beta && eval >= beta - && eval < 22761) // 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 < 18404 + && (ss-1)->statScore < 17329 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 19 * depth - improvement / 13 + 257 + && ss->staticEval >= beta - 21 * depth - improvement / 13 + 258 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly)) @@ -788,7 +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]; @@ -802,10 +801,9 @@ namespace { if (nullValue >= beta) { // Do not return unproven mate or TB scores - if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY) - nullValue = beta; + nullValue = std::min(nullValue, VALUE_TB_WIN_IN_MAX_PLY-1); - if (thisThread->nmpMinPly || (abs(beta) < VALUE_KNOWN_WIN && depth < 14)) + if (thisThread->nmpMinPly || depth < 14) return nullValue; assert(!thisThread->nmpMinPly); // Recursive verification is not allowed @@ -823,9 +821,24 @@ namespace { } } - probCutBeta = beta + 174 - 60 * improving; + // Step 10. If the position doesn't have a 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 @@ -835,8 +848,7 @@ namespace { // 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)) { @@ -877,27 +889,12 @@ 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 >= 8 - && !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 + 430; + probCutBeta = beta + 413; if ( ss->inCheck && !PvNode - && depth >= 2 && ttCapture && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 4 @@ -988,28 +985,31 @@ moves_loop: // When in check, search starts here if ( !givesCheck && lmrDepth < 7 && !ss->inCheck - && ss->staticEval + 207 + 223 * lmrDepth + PieceValue[EG][pos.piece_on(to_sq(move))] - + captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] * 1078 / 7000 < alpha) + && 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(-205) * depth)) { - // Don't prune the move if opponent 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 (opponent 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 @@ -1020,24 +1020,24 @@ moves_loop: // When in check, search starts here // Continuation history based pruning (~2 Elo) if ( lmrDepth < 6 - && history < -3792 * depth) + && history < -3832 * depth) continue; history += 2 * thisThread->mainHistory[us][from_to(move)]; - lmrDepth += history / 7019; + lmrDepth += history / 7011; lmrDepth = std::max(lmrDepth, -2); // Futility pruning: parent node (~13 Elo) if ( !ss->inCheck && lmrDepth < 12 - && ss->staticEval + 111 + 136 * lmrDepth <= alpha) + && 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(-27 * lmrDepth * lmrDepth - 33 * lmrDepth / 2))) + if (!pos.see_ge(move, Value(-27 * lmrDepth * lmrDepth - 16 * lmrDepth))) continue; } } @@ -1051,6 +1051,9 @@ moves_loop: // When in check, search starts here // then that move is singular and should be extended. To verify this we do // 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. + // Depth margin and singularBeta margin are known for having non-linear scaling. + // Their values are optimized to time controls of 180+1.8 and longer + // so changing them requires tests at this type of time controls. if ( !rootNode && depth >= 4 - (thisThread->completedDepth > 22) + 2 * (PvNode && tte->is_pv()) && move == ttMove @@ -1060,7 +1063,7 @@ moves_loop: // When in check, search starts here && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3) { - Value singularBeta = ttValue - (99 + 65 * (ss->ttPv && !PvNode)) * depth / 64; + Value singularBeta = ttValue - (82 + 65 * (ss->ttPv && !PvNode)) * depth / 64; Depth singularDepth = (depth - 1) / 2; ss->excludedMove = move; @@ -1074,7 +1077,7 @@ moves_loop: // When in check, search starts here // Avoid search explosion by limiting the number of double extensions if ( !PvNode - && value < singularBeta - 22 + && value < singularBeta - 21 && ss->doubleExtensions <= 11) { extension = 2; @@ -1105,15 +1108,14 @@ moves_loop: // When in check, search starts here // Check extensions (~1 Elo) else if ( givesCheck - && depth > 9 - && abs(ss->staticEval) > 87) + && depth > 9) extension = 1; // Quiet ttMove extensions (~1 Elo) else if ( PvNode && move == ttMove && move == ss->killers[0] - && (*contHist[0])[movedPiece][to_sq(move)] >= 5480) + && (*contHist[0])[movedPiece][to_sq(move)] >= 5168) extension = 1; } @@ -1155,7 +1157,7 @@ moves_loop: // When in check, search starts here // Decrease reduction for PvNodes based on depth (~2 Elo) if (PvNode) - r -= 1 + 11 / (3 + depth); + r -= 1 + 12 / (3 + depth); // Decrease reduction if ttMove has been singularly extended (~1 Elo) if (singularQuietLMR) @@ -1172,10 +1174,10 @@ moves_loop: // When in check, search starts here + (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)] - - 3755; + - 4006; // Decrease/increase reduction for moves with a good/bad history (~25 Elo) - r -= ss->statScore / (10445 + 4762 * (depth > 6 && depth < 21)); + 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 @@ -1199,8 +1201,8 @@ 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 > (bestValue + 63 + 11 * (newDepth - d)); - const bool doEvenDeeperSearch = value > alpha + 662 && ss->doubleExtensions <= 6; + 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; @@ -1319,8 +1321,8 @@ moves_loop: // When in check, search starts here // 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 < 14001 - && value > -12754) + && beta < 14362 + && value > -12393) depth -= depth > 3 && depth < 12 ? 2 : 1; assert(depth > 0); @@ -1369,7 +1371,7 @@ 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 - 100 * depth) + ((ss-1)->moveCount > 11); + 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); } @@ -1453,18 +1455,14 @@ 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; // Step 4. Static evaluation of the position if (ss->inCheck) - { - ss->staticEval = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; - } else { if (ss->ttHit) @@ -1480,9 +1478,8 @@ moves_loop: // When in check, search starts here } else // In case of null move search use previous static eval with a different sign - ss->staticEval = bestValue = - (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) - : -(ss-1)->staticEval; + ss->staticEval = bestValue = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) + : -(ss-1)->staticEval; // Stand pat. Return immediately if static value is at least beta if (bestValue >= beta) @@ -1498,7 +1495,7 @@ moves_loop: // When in check, search starts here if (PvNode && bestValue > alpha) alpha = bestValue; - futilityBase = bestValue + 190; + futilityBase = bestValue + 200; } const PieceToHistory* contHist[] = { (ss-1)->continuationHistory, (ss-2)->continuationHistory, @@ -1509,7 +1506,7 @@ 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, @@ -1521,97 +1518,98 @@ moves_loop: // When in check, search starts here // or a beta cutoff occurs. while ((move = mp.next_move()) != MOVE_NONE) { - assert(is_ok(move)); + assert(is_ok(move)); - // Check for legality - if (!pos.legal(move)) - continue; + // Check for legality + if (!pos.legal(move)) + continue; - givesCheck = pos.gives_check(move); - capture = pos.capture_stage(move); - - moveCount++; - - // Step 6. Pruning. - if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY) - { - // Futility pruning and moveCount pruning (~10 Elo) - if ( !givesCheck - && to_sq(move) != prevSq - && futilityBase > -VALUE_KNOWN_WIN - && type_of(move) != PROMOTION) - { - if (moveCount > 2) - continue; + givesCheck = pos.gives_check(move); + capture = pos.capture_stage(move); - futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))]; + moveCount++; - if (futilityValue <= alpha) - { - bestValue = std::max(bestValue, futilityValue); - continue; - } + // Step 6. Pruning. + if (bestValue > VALUE_TB_LOSS_IN_MAX_PLY) + { + // Futility pruning and moveCount pruning (~10 Elo) + if ( !givesCheck + && to_sq(move) != prevSq + && futilityBase > -VALUE_KNOWN_WIN + && type_of(move) != PROMOTION) + { + if (moveCount > 2) + continue; - if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1)) - { - bestValue = std::max(bestValue, futilityBase); - continue; - } - } + futilityValue = futilityBase + PieceValue[EG][pos.piece_on(to_sq(move))]; - // We prune after 2nd quiet check evasion where being 'in check' is implicitly checked through the counter - // and being a 'quiet' apart from being a tt move is assumed after an increment because captures are pushed ahead. - if (quietCheckEvasions > 1) - break; + if (futilityValue <= alpha) + { + bestValue = std::max(bestValue, futilityValue); + continue; + } - // Continuation history based pruning (~3 Elo) - if ( !capture - && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < 0 - && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < 0) - continue; + if (futilityBase <= alpha && !pos.see_ge(move, VALUE_ZERO + 1)) + { + bestValue = std::max(bestValue, futilityBase); + continue; + } + } - // Do not search moves with bad enough SEE values (~5 Elo) - if (!pos.see_ge(move, Value(-94))) - continue; - } + // We prune after the second quiet check evasion move, where being 'in check' is + // implicitly checked through the counter, and being a 'quiet move' apart from + // being a tt move is assumed after an increment because captures are pushed ahead. + if (quietCheckEvasions > 1) + break; + + // Continuation history based pruning (~3 Elo) + if ( !capture + && (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < 0 + && (*contHist[1])[pos.moved_piece(move)][to_sq(move)] < 0) + continue; + + // Do not search moves with bad enough SEE values (~5 Elo) + if (!pos.see_ge(move, Value(-95))) + continue; + } - // Speculative prefetch as early as possible - prefetch(TT.first_entry(pos.key_after(move))); + // Speculative prefetch as early as possible + prefetch(TT.first_entry(pos.key_after(move))); - // Update the current move - ss->currentMove = move; - ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] - [capture] - [pos.moved_piece(move)] - [to_sq(move)]; + // Update the current move + ss->currentMove = move; + ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] + [capture] + [pos.moved_piece(move)] + [to_sq(move)]; - quietCheckEvasions += !capture && ss->inCheck; + quietCheckEvasions += !capture && ss->inCheck; - // Step 7. Make and search the move - pos.do_move(move, st, givesCheck); - value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1); - pos.undo_move(move); + // Step 7. Make and search the move + pos.do_move(move, st, givesCheck); + value = -qsearch(pos, ss+1, -beta, -alpha, depth - 1); + pos.undo_move(move); - assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); + assert(value > -VALUE_INFINITE && value < VALUE_INFINITE); - // Step 8. Check for a new best move - if (value > bestValue) - { - bestValue = value; + // Step 8. Check for a new best move + if (value > bestValue) + { + bestValue = value; - if (value > alpha) - { - bestMove = move; + if (value > alpha) + { + bestMove = move; - if (PvNode) // Update pv even in fail-high case - update_pv(ss->pv, move, (ss+1)->pv); + if (PvNode) // Update pv even in fail-high case + update_pv(ss->pv, move, (ss+1)->pv); - if (PvNode && value < beta) // Update alpha here! - alpha = value; - else - break; // Fail high - } - } + if (PvNode && value < beta) // Update alpha here! + alpha = value; + else + break; // Fail high + } + } } // Step 9. Check for mate @@ -1704,7 +1702,7 @@ moves_loop: // When in check, search starts here if (!pos.capture_stage(bestMove)) { - int bonus2 = bestValue > beta + 143 ? 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