X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=c4ed73372df2040ffee3bc7093e61e9301011ecd;hp=008a60ede4a6138c47901d8c359fbcc64aa2707c;hb=282644f1413db0ccb58e2e1793d5007c58ff8ce2;hpb=09b6d28391cf582d99897360b225bcbbe38dd1c6 diff --git a/src/search.cpp b/src/search.cpp index 008a60ed..c4ed7337 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -61,9 +61,6 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV, Root }; - constexpr uint64_t TtHitAverageWindow = 4096; - constexpr uint64_t TtHitAverageResolution = 1024; - // Futility margin Value futility_margin(Depth d, bool improving) { return Value(214 * (d - improving)); @@ -72,9 +69,9 @@ namespace { // Reductions lookup table, initialized at startup int Reductions[MAX_MOVES]; // [depth or moveNumber] - Depth reduction(bool i, Depth d, int mn) { + Depth reduction(bool i, Depth d, int mn, bool rangeReduction) { int r = Reductions[d] * Reductions[mn]; - return (r + 534) / 1024 + (!i && r > 904); + return (r + 534) / 1024 + (!i && r > 904) + rangeReduction; } constexpr int futility_move_count(bool improving, Depth depth) { @@ -83,7 +80,7 @@ namespace { // History and stats update bonus, based on depth int stat_bonus(Depth d) { - return d > 14 ? 73 : 6 * d * d + 229 * d - 215; + return std::min((6 * d + 229) * d - 215 , 2000); } // Add a small random component to draw evaluations to avoid 3-fold blindness @@ -91,14 +88,46 @@ namespace { return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1); } - // Skill structure is used to implement strength limit + // Check if the current thread is in a search explosion + ExplosionState search_explosion(Thread* thisThread) { + + uint64_t nodesNow = thisThread->nodes; + bool explosive = thisThread->doubleExtensionAverage[WHITE].is_greater(2, 100) + || thisThread->doubleExtensionAverage[BLACK].is_greater(2, 100); + + if (explosive) + thisThread->nodesLastExplosive = nodesNow; + else + thisThread->nodesLastNormal = nodesNow; + + if ( explosive + && thisThread->state == EXPLOSION_NONE + && nodesNow - thisThread->nodesLastNormal > 6000000) + thisThread->state = MUST_CALM_DOWN; + + if ( thisThread->state == MUST_CALM_DOWN + && nodesNow - thisThread->nodesLastExplosive > 6000000) + thisThread->state = EXPLOSION_NONE; + + return thisThread->state; + } + + // Skill structure is used to implement strength limit. If we have an uci_elo then + // we convert it to a suitable fractional skill level using anchoring to CCRL Elo + // (goldfish 1.13 = 2000) and a fit through Ordo derived Elo for match (TC 60+0.6) + // results spanning a wide range of k values. struct Skill { - explicit Skill(int l) : level(l) {} - bool enabled() const { return level < 20; } - bool time_to_pick(Depth depth) const { return depth == 1 + level; } + Skill(int skill_level, int uci_elo) { + if (uci_elo) + level = std::clamp(std::pow((uci_elo - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0); + else + level = double(skill_level); + } + bool enabled() const { return level < 20.0; } + bool time_to_pick(Depth depth) const { return depth == 1 + int(level); } Move pick_best(size_t multiPV); - int level; + double level; Move best = MOVE_NONE; }; @@ -152,7 +181,7 @@ namespace { void Search::init() { for (int i = 1; i < MAX_MOVES; ++i) - Reductions[i] = int(21.9 * std::log(i)); + Reductions[i] = int((21.9 + std::log(Threads.size()) / 2) * std::log(i)); } @@ -222,10 +251,11 @@ void MainThread::search() { Time.availableNodes += Limits.inc[us] - Threads.nodes_searched(); Thread* bestThread = this; + Skill skill = Skill(Options["Skill Level"], Options["UCI_LimitStrength"] ? int(Options["UCI_Elo"]) : 0); if ( int(Options["MultiPV"]) == 1 && !Limits.depth - && !(Skill(Options["Skill Level"]).enabled() || int(Options["UCI_LimitStrength"])) + && !skill.enabled() && rootMoves[0].pv[0] != MOVE_NONE) bestThread = Threads.get_best_thread(); @@ -256,7 +286,7 @@ void Thread::search() { // The latter is needed for statScore and killer initialization. Stack stack[MAX_PLY+10], *ss = stack+7; Move pv[MAX_PLY+1]; - Value bestValue, alpha, beta, delta; + Value alpha, beta, delta; Move lastBestMove = MOVE_NONE; Depth lastBestMoveDepth = 0; MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); @@ -290,19 +320,7 @@ void Thread::search() { std::fill(&lowPlyHistory[MAX_LPH - 2][0], &lowPlyHistory.back().back() + 1, 0); size_t multiPV = size_t(Options["MultiPV"]); - - // Pick integer skill levels, but non-deterministically round up or down - // such that the average integer skill corresponds to the input floating point one. - // UCI_Elo is converted to a suitable fractional skill level, using anchoring - // to CCRL Elo (goldfish 1.13 = 2000) and a fit through Ordo derived Elo - // for match (TC 60+0.6) results spanning a wide range of k values. - PRNG rng(now()); - double floatLevel = Options["UCI_LimitStrength"] ? - std::clamp(std::pow((Options["UCI_Elo"] - 1346.6) / 143.4, 1 / 0.806), 0.0, 20.0) : - double(Options["Skill Level"]); - int intLevel = int(floatLevel) + - ((floatLevel - int(floatLevel)) * 1024 > rng.rand() % 1024 ? 1 : 0); - Skill skill(intLevel); + Skill skill(Options["Skill Level"], Options["UCI_LimitStrength"] ? int(Options["UCI_Elo"]) : 0); // When playing with strength handicap enable MultiPV search that we will // use behind the scenes to retrieve a set of possible moves. @@ -310,9 +328,16 @@ void Thread::search() { multiPV = std::max(multiPV, (size_t)4); multiPV = std::min(multiPV, rootMoves.size()); - ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2; - trend = SCORE_ZERO; + doubleExtensionAverage[WHITE].set(0, 100); // initialize the running average at 0% + doubleExtensionAverage[BLACK].set(0, 100); // initialize the running average at 0% + + nodesLastExplosive = nodes; + nodesLastNormal = nodes; + state = EXPLOSION_NONE; + trend = SCORE_ZERO; + optimism[ us] = Value(25); + optimism[~us] = -optimism[us]; int searchAgainCounter = 0; @@ -353,16 +378,19 @@ void Thread::search() { // Reset aspiration window starting size if (rootDepth >= 4) { - Value prev = rootMoves[pvIdx].previousScore; - delta = Value(17); + Value prev = rootMoves[pvIdx].averageScore; + delta = Value(17) + int(prev) * prev / 16384; alpha = std::max(prev - delta,-VALUE_INFINITE); beta = std::min(prev + delta, VALUE_INFINITE); - // Adjust trend based on root move's previousScore (dynamic contempt) - int tr = 113 * prev / (abs(prev) + 147); - + // Adjust trend and optimism based on root move's previousScore + int tr = sigmoid(prev, 0, 0, 147, 113, 1); trend = (us == WHITE ? make_score(tr, tr / 2) : -make_score(tr, tr / 2)); + + int opt = sigmoid(prev, 0, 25, 147, 14464, 256); + optimism[ us] = Value(opt); + optimism[~us] = -optimism[us]; } // Start with a small aspiration window and, in the case of a fail @@ -518,6 +546,14 @@ namespace { template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { + Thread* thisThread = pos.this_thread(); + + // Step 0. Limit search explosion + if ( ss->ply > 10 + && search_explosion(thisThread) == MUST_CALM_DOWN + && depth > (ss-1)->depth) + depth = (ss-1)->depth; + constexpr bool PvNode = nodeType != NonPV; constexpr bool rootNode = nodeType == Root; const Depth maxNextDepth = rootNode ? depth : depth + 1; @@ -556,14 +592,13 @@ namespace { bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularQuietLMR; Piece movedPiece; - int moveCount, captureCount, quietCount; + int moveCount, captureCount, quietCount, bestMoveCount, improvement; // Step 1. Initialize node - Thread* thisThread = pos.this_thread(); ss->inCheck = pos.checkers(); priorCapture = pos.captured_piece(); Color us = pos.side_to_move(); - moveCount = captureCount = quietCount = ss->moveCount = 0; + moveCount = bestMoveCount = captureCount = quietCount = ss->moveCount = 0; bestValue = -VALUE_INFINITE; maxValue = VALUE_INFINITE; @@ -595,6 +630,8 @@ namespace { if (alpha >= beta) return alpha; } + else + thisThread->rootDelta = beta - alpha; assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -602,8 +639,12 @@ namespace { (ss+1)->excludedMove = bestMove = MOVE_NONE; (ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE; ss->doubleExtensions = (ss-1)->doubleExtensions; + ss->depth = depth; Square prevSq = to_sq((ss-1)->currentMove); + // Update the running average statistics for double extensions + thisThread->doubleExtensionAverage[us].update(ss->depth > (ss-1)->depth); + // Initialize statScore to zero for the grandchildren of the current position. // So statScore is shared between all grandchildren and only the first grandchild // starts with statScore = 0. Later grandchildren start with the last calculated @@ -621,6 +662,7 @@ namespace { ttValue = ss->ttHit ? value_from_tt(tte->value(), ss->ply, pos.rule50_count()) : VALUE_NONE; ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ss->ttHit ? tte->move() : MOVE_NONE; + ttCapture = ttMove && pos.capture_or_promotion(ttMove); if (!excludedMove) ss->ttPv = PvNode || (ss->ttHit && tte->is_pv()); @@ -632,14 +674,10 @@ namespace { && is_ok((ss-1)->currentMove)) thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5); - // thisThread->ttHitAverage can be used to approximate the running average of ttHit - thisThread->ttHitAverage = (TtHitAverageWindow - 1) * thisThread->ttHitAverage / TtHitAverageWindow - + TtHitAverageResolution * ss->ttHit; - // At non-PV nodes we check for an early TT cutoff if ( !PvNode && ss->ttHit - && tte->depth() >= depth + && tte->depth() > depth - (thisThread->id() % 2 == 1) && ttValue != VALUE_NONE // Possible in case of TT access race && (ttValue >= beta ? (tte->bound() & BOUND_LOWER) : (tte->bound() & BOUND_UPPER))) @@ -650,7 +688,7 @@ namespace { if (ttValue >= beta) { // Bonus for a quiet ttMove that fails high - if (!pos.capture_or_promotion(ttMove)) + if (!ttCapture) update_quiet_stats(pos, ss, ttMove, stat_bonus(depth), depth); // Extra penalty for early quiet moves of the previous ply @@ -658,7 +696,7 @@ namespace { update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1)); } // Penalty for a quiet ttMove that fails low - else if (!pos.capture_or_promotion(ttMove)) + else if (!ttCapture) { int penalty = -stat_bonus(depth); thisThread->mainHistory[us][from_to(ttMove)] << penalty; @@ -732,6 +770,7 @@ namespace { // Skip early pruning when in check ss->staticEval = eval = VALUE_NONE; improving = false; + improvement = 0; goto moves_loop; } else if (ss->ttHit) @@ -752,36 +791,36 @@ namespace { } else { - // In case of null move search use previous static eval with a different sign - // and addition of two tempos - if ((ss-1)->currentMove != MOVE_NULL) - ss->staticEval = eval = evaluate(pos); - else - ss->staticEval = eval = -(ss-1)->staticEval; + ss->staticEval = eval = evaluate(pos); // Save static evaluation into transposition table - tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); + if (!excludedMove) + tte->save(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval); } // Use static evaluation difference to improve quiet move ordering if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture) { - int bonus = std::clamp(-depth * 4 * int((ss-1)->staticEval + ss->staticEval), -1000, 1000); + int bonus = std::clamp(-16 * int((ss-1)->staticEval + ss->staticEval), -2000, 2000); thisThread->mainHistory[~us][from_to((ss-1)->currentMove)] << bonus; } - // Set up improving flag that is used in various pruning heuristics - // We define position as improving if static evaluation of position is better - // Than the previous static evaluation at our turn - // In case of us being in check at our previous move we look at move prior to it - improving = (ss-2)->staticEval == VALUE_NONE - ? ss->staticEval > (ss-4)->staticEval || (ss-4)->staticEval == VALUE_NONE - : ss->staticEval > (ss-2)->staticEval; + // Set up the improvement variable, which is the difference between the current + // static evaluation and the previous static evaluation at our turn (if we were + // in check at our previous move we look at the move prior to it). The improvement + // 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 + : 200; - // Step 7. Futility pruning: child node (~50 Elo) - if ( !PvNode + improving = improvement > 0; + + // Step 7. Futility pruning: child node (~50 Elo). + // The depth condition is important for mate finding. + if ( !ss->ttPv + && depth < 9 && eval - futility_margin(depth, improving) >= beta - && eval < VALUE_KNOWN_WIN) // Do not return unproven wins + && eval < 15000) // 50% larger than VALUE_KNOWN_WIN, but smaller than TB wins. return eval; // Step 8. Null move search with verification search (~40 Elo) @@ -790,7 +829,7 @@ namespace { && (ss-1)->statScore < 23767 && eval >= beta && eval >= ss->staticEval - && ss->staticEval >= beta - 20 * depth - 22 * improving + 168 * ss->ttPv + 159 + && ss->staticEval >= beta - 20 * depth - improvement / 15 + 204 && !excludedMove && pos.non_pawn_material(us) && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) @@ -798,7 +837,7 @@ namespace { assert(eval - beta >= 0); // Null move dynamic reduction based on depth and value - Depth R = (1090 + 81 * depth) / 256 + std::min(int(eval - beta) / 205, 3); + Depth R = std::min(int(eval - beta) / 205, 3) + depth / 3 + 4; ss->currentMove = MOVE_NULL; ss->continuationHistory = &thisThread->continuationHistory[0][0][NO_PIECE][0]; @@ -854,19 +893,16 @@ namespace { assert(probCutBeta < VALUE_INFINITE); MovePicker mp(pos, ttMove, probCutBeta - ss->staticEval, &captureHistory); - int probCutCount = 0; bool ttPv = ss->ttPv; ss->ttPv = false; - while ( (move = mp.next_move()) != MOVE_NONE - && probCutCount < 2 + 2 * cutNode) + while ((move = mp.next_move()) != MOVE_NONE) if (move != excludedMove && pos.legal(move)) { assert(pos.capture_or_promotion(move)); assert(depth >= 5); captureOrPromotion = true; - probCutCount++; ss->currentMove = move; ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] @@ -900,15 +936,20 @@ namespace { ss->ttPv = ttPv; } - // Step 10. If the position is not in TT, decrease depth by 2 + // Step 10. If the position is not in TT, decrease depth by 2 or 1 depending on node type if ( PvNode && depth >= 6 && !ttMove) depth -= 2; -moves_loop: // When in check, search starts from here + if ( cutNode + && depth >= 9 + && !ttMove) + depth--; + +moves_loop: // When in check, search starts here - ttCapture = ttMove && pos.capture_or_promotion(ttMove); + int rangeReduction = 0; // Step 11. A small Probcut idea, when we are in check probCutBeta = beta + 409; @@ -941,7 +982,6 @@ moves_loop: // When in check, search starts from here value = bestValue; singularQuietLMR = moveCountPruning = false; - bool doubleExtension = false; // Indicate PvNodes that will probably fail low if the node was searched // at a depth equal or greater than the current depth, and the result of this search was a fail low. @@ -988,7 +1028,7 @@ moves_loop: // When in check, search starts from here // Calculate new depth for this move newDepth = depth - 1; - // Step 13. Pruning at shallow depth (~200 Elo) + // Step 13. Pruning at shallow depth (~200 Elo). Depth conditions are important for mate finding. if ( !rootNode && pos.non_pawn_material(us) && bestValue > VALUE_TB_LOSS_IN_MAX_PLY) @@ -997,7 +1037,7 @@ moves_loop: // When in check, search starts from here moveCountPruning = moveCount >= futility_move_count(improving, depth); // Reduced depth of the next LMR search - int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0); + int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0); if ( captureOrPromotion || givesCheck) @@ -1014,24 +1054,25 @@ moves_loop: // When in check, search starts from here } else { + int history = (*contHist[0])[movedPiece][to_sq(move)] + + (*contHist[1])[movedPiece][to_sq(move)] + + (*contHist[3])[movedPiece][to_sq(move)]; + // Continuation history based pruning (~20 Elo) if ( lmrDepth < 5 - && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold - && (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold) + && history < -3000 * depth + 3000) continue; + history += thisThread->mainHistory[us][from_to(move)]; + // Futility pruning: parent node (~5 Elo) - if ( lmrDepth < 7 - && !ss->inCheck - && ss->staticEval + 174 + 157 * lmrDepth <= alpha - && (*contHist[0])[movedPiece][to_sq(move)] - + (*contHist[1])[movedPiece][to_sq(move)] - + (*contHist[3])[movedPiece][to_sq(move)] - + (*contHist[5])[movedPiece][to_sq(move)] / 3 < 28255) + if ( !ss->inCheck + && lmrDepth < 8 + && ss->staticEval + 142 + 139 * lmrDepth + history / 64 <= alpha) continue; // Prune moves with negative SEE (~20 Elo) - if (!pos.see_ge(move, Value(-(30 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) + if (!pos.see_ge(move, Value(-21 * lmrDepth * lmrDepth - 21 * lmrDepth))) continue; } } @@ -1052,7 +1093,7 @@ moves_loop: // When in check, search starts from here && (tte->bound() & BOUND_LOWER) && tte->depth() >= depth - 3) { - Value singularBeta = ttValue - 2 * depth; + Value singularBeta = ttValue - 3 * depth; Depth singularDepth = (depth - 1) / 2; ss->excludedMove = move; @@ -1064,14 +1105,11 @@ moves_loop: // When in check, search starts from here extension = 1; singularQuietLMR = !ttCapture; - // Avoid search explosion by limiting the number of double extensions to at most 3 + // Avoid search explosion by limiting the number of double extensions if ( !PvNode - && value < singularBeta - 93 - && ss->doubleExtensions < 3) - { + && value < singularBeta - 75 + && ss->doubleExtensions <= 6) extension = 2; - doubleExtension = true; - } } // Multi-cut pruning @@ -1082,21 +1120,28 @@ moves_loop: // When in check, search starts from here else if (singularBeta >= beta) return singularBeta; - // If the eval of ttMove is greater than beta we try also if there is another - // move that pushes it over beta, if so also produce a cutoff. + // If the eval of ttMove is greater than beta, we reduce it (negative extension) else if (ttValue >= beta) - { - ss->excludedMove = move; - value = search(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode); - ss->excludedMove = MOVE_NONE; - - if (value >= beta) - return beta; - } + extension = -2; } + + // Capture extensions for PvNodes and cutNodes + else if ( (PvNode || cutNode) + && captureOrPromotion + && moveCount != 1) + extension = 1; + + // Check extensions else if ( givesCheck && depth > 6 - && abs(ss->staticEval) > Value(100)) + && abs(ss->staticEval) > 100) + extension = 1; + + // Quiet ttMove extensions + else if ( PvNode + && move == ttMove + && move == ss->killers[0] + && (*contHist[0])[movedPiece][to_sq(move)] >= 10000) extension = 1; // Add extension to new depth @@ -1122,18 +1167,16 @@ moves_loop: // When in check, search starts from here // cases where we extend a son if it has good chances to be "interesting". if ( depth >= 3 && moveCount > 1 + 2 * rootNode - && ( !captureOrPromotion - || (cutNode && (ss-1)->moveCount > 1) - || !ss->ttPv) - && (!PvNode || ss->ply > 1 || thisThread->id() % 4 != 3)) + && ( !ss->ttPv + || !captureOrPromotion + || (cutNode && (ss-1)->moveCount > 1))) { - Depth r = reduction(improving, depth, moveCount); - - if (PvNode) - r--; + Depth r = reduction(improving, depth, moveCount, rangeReduction > 2); - // Decrease reduction if the ttHit running average is large (~0 Elo) - if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024) + // Decrease reduction at some PvNodes (~2 Elo) + if ( PvNode + && bestMoveCount <= 3 + && beta - alpha >= thisThread->rootDelta / 4) r--; // Decrease reduction if position is or has been on the PV @@ -1159,30 +1202,36 @@ moves_loop: // When in check, search starts from here if (cutNode && move != ss->killers[0]) r += 2; - if (!captureOrPromotion) - { - // Increase reduction if ttMove is a capture (~3 Elo) - if (ttCapture) - r++; - - ss->statScore = thisThread->mainHistory[us][from_to(move)] - + (*contHist[0])[movedPiece][to_sq(move)] - + (*contHist[1])[movedPiece][to_sq(move)] - + (*contHist[3])[movedPiece][to_sq(move)] - - 4923; - - // Decrease/increase reduction for moves with a good/bad history (~30 Elo) - if (!ss->inCheck) - r -= ss->statScore / 14721; - } + // Increase reduction if ttMove is a capture (~3 Elo) + if (ttCapture) + r++; + + ss->statScore = thisThread->mainHistory[us][from_to(move)] + + (*contHist[0])[movedPiece][to_sq(move)] + + (*contHist[1])[movedPiece][to_sq(move)] + + (*contHist[3])[movedPiece][to_sq(move)] + - 4923; - // In general we want to cap the LMR depth search at newDepth. But if - // reductions are really negative and movecount is low, we allow this move - // to be searched deeper than the first move, unless ttMove was extended by 2. - Depth d = std::clamp(newDepth - r, 1, newDepth + (r < -1 && moveCount <= 5 && !doubleExtension)); + // Decrease/increase reduction for moves with a good/bad history (~30 Elo) + r -= ss->statScore / 14721; + + // In general we want to cap the LMR depth search at newDepth. But if reductions + // are really negative and movecount is low, we allow this move to be searched + // deeper than the first move (this may lead to hidden double extensions). + int deeper = r >= -1 ? 0 + : moveCount <= 5 ? 2 + : PvNode && depth > 6 ? 1 + : cutNode && moveCount <= 7 ? 1 + : 0; + + Depth d = std::clamp(newDepth - r, 1, newDepth + deeper); value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + // Range reductions (~3 Elo) + if (ss->staticEval - value < 30 && depth > 7) + rangeReduction++; + // If the son is reduced and fails high it will be re-searched at full depth doFullDepthSearch = value > alpha && d < newDepth; didLMR = true; @@ -1237,6 +1286,8 @@ moves_loop: // When in check, search starts from here RootMove& rm = *std::find(thisThread->rootMoves.begin(), thisThread->rootMoves.end(), move); + rm.averageScore = rm.averageScore != -VALUE_INFINITE ? (2 * value + rm.averageScore) / 3 : value; + // PV move or new best move? if (moveCount == 1 || value > alpha) { @@ -1249,9 +1300,11 @@ moves_loop: // When in check, search starts from here for (Move* m = (ss+1)->pv; *m != MOVE_NONE; ++m) rm.pv.push_back(*m); - // We record how often the best move has been changed in each - // iteration. This information is used for time management and LMR - if (moveCount > 1) + // We record how often the best move has been changed in each iteration. + // This information is used for time management and LMR. In MultiPV mode, + // we must take care to only do this for the first PV line. + if ( moveCount > 1 + && !thisThread->pvIdx) ++thisThread->bestMoveChanges; } else @@ -1273,7 +1326,10 @@ moves_loop: // When in check, search starts from here update_pv(ss->pv, move, (ss+1)->pv); if (PvNode && value < beta) // Update alpha! Always alpha < beta + { alpha = value; + bestMoveCount++; + } else { assert(value >= beta); // Fail high @@ -1321,7 +1377,7 @@ moves_loop: // When in check, search starts from here // Bonus for prior countermove that caused the fail low else if ( (depth >= 3 || PvNode) && !priorCapture) - update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth)); + update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + (PvNode || cutNode))); if (PvNode) bestValue = std::min(bestValue, maxValue); @@ -1368,13 +1424,12 @@ moves_loop: // When in check, search starts from here Key posKey; Move ttMove, move, bestMove; Depth ttDepth; - Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; + Value bestValue, value, ttValue, futilityValue, futilityBase; bool pvHit, givesCheck, captureOrPromotion; int moveCount; if (PvNode) { - oldAlpha = alpha; // To flag BOUND_EXACT when eval above alpha and no available moves (ss+1)->pv = pv; ss->pv[0] = MOVE_NONE; } @@ -1432,7 +1487,6 @@ moves_loop: // When in check, search starts from here } else // In case of null move search use previous static eval with a different sign - // and addition of two tempos ss->staticEval = bestValue = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss-1)->staticEval; @@ -1472,6 +1526,10 @@ moves_loop: // When in check, search starts from here { assert(is_ok(move)); + // Check for legality + if (!pos.legal(move)) + continue; + givesCheck = pos.gives_check(move); captureOrPromotion = pos.capture_or_promotion(move); @@ -1510,13 +1568,6 @@ moves_loop: // When in check, search starts from here // Speculative prefetch as early as possible prefetch(TT.first_entry(pos.key_after(move))); - // Check for legality just before making the move - if (!pos.legal(move)) - { - moveCount--; - continue; - } - ss->currentMove = move; ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] [captureOrPromotion] @@ -1568,8 +1619,7 @@ moves_loop: // When in check, search starts from here // Save gathered info in transposition table tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, - bestValue >= beta ? BOUND_LOWER : - PvNode && bestValue > oldAlpha ? BOUND_EXACT : BOUND_UPPER, + bestValue >= beta ? BOUND_LOWER : BOUND_UPPER, ttDepth, bestMove, ss->staticEval); assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE); @@ -1645,8 +1695,8 @@ moves_loop: // When in check, search starts from here PieceType captured = type_of(pos.piece_on(to_sq(bestMove))); bonus1 = stat_bonus(depth + 1); - bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus - : std::min(bonus1, stat_bonus(depth)); // smaller bonus + bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus + : stat_bonus(depth); // smaller bonus if (!pos.capture_or_promotion(bestMove)) { @@ -1712,10 +1762,6 @@ moves_loop: // When in check, search starts from here thisThread->mainHistory[us][from_to(move)] << bonus; update_continuation_histories(ss, pos.moved_piece(move), to_sq(move), bonus); - // Penalty for reversed move in case of moved piece not being a pawn - if (type_of(pos.moved_piece(move)) != PAWN) - thisThread->mainHistory[us][from_to(reverse_move(move))] << -bonus; - // Update countermove history if (is_ok((ss-1)->currentMove)) { @@ -1739,8 +1785,8 @@ moves_loop: // When in check, search starts from here // RootMoves are already sorted by score in descending order Value topScore = rootMoves[0].score; int delta = std::min(topScore - rootMoves[multiPV - 1].score, PawnValueMg); - int weakness = 120 - 2 * level; int maxScore = -VALUE_INFINITE; + double weakness = 120 - 2 * level; // Choose best move. For each move score we add two terms, both dependent on // weakness. One is deterministic and bigger for weaker levels, and one is @@ -1748,8 +1794,8 @@ moves_loop: // When in check, search starts from here for (size_t i = 0; i < multiPV; ++i) { // This is our magic formula - int push = ( weakness * int(topScore - rootMoves[i].score) - + delta * (rng.rand() % weakness)) / 128; + int push = int(( weakness * int(topScore - rootMoves[i].score) + + delta * (rng.rand() % int(weakness))) / 128); if (rootMoves[i].score + push >= maxScore) {