X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fsearch.cpp;h=3eb8e9e1ee867e0595b6b2a247fe13db633575c5;hb=135caee606c86ade9e9c199ef469661c374eb9ba;hp=b400b8f8b0c4c409d4c004e6047f12468e8d2959;hpb=e8788d1b32c9356fa0a127952d48c3748d8ec826;p=stockfish diff --git a/src/search.cpp b/src/search.cpp index b400b8f8..3eb8e9e1 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) { @@ -91,6 +88,30 @@ namespace { return VALUE_DRAW + Value(2 * (thisThread->nodes & 1) - 1); } + // 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 struct Skill { explicit Skill(int l) : level(l) {} @@ -152,7 +173,7 @@ 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)); } @@ -310,8 +331,14 @@ void Thread::search() { multiPV = std::max(multiPV, (size_t)4); multiPV = std::min(multiPV, rootMoves.size()); - ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2; + ttHitAverage.set(50, 100); // initialize the running average at 50% + 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; int searchAgainCounter = 0; @@ -518,6 +545,14 @@ 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; @@ -554,12 +589,11 @@ namespace { Value bestValue, value, ttValue, eval, maxValue, probCutBeta; bool givesCheck, improving, didLMR, priorCapture; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, - ttCapture, singularQuietLMR; + ttCapture, singularQuietLMR, noLMRExtension; Piece movedPiece; int moveCount, captureCount, quietCount; // Step 1. Initialize node - Thread* thisThread = pos.this_thread(); ss->inCheck = pos.checkers(); priorCapture = pos.captured_piece(); Color us = pos.side_to_move(); @@ -602,8 +636,12 @@ 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 @@ -632,9 +670,8 @@ 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; + // running average of ttHit + thisThread->ttHitAverage.update(ss->ttHit); // At non-PV nodes we check for an early TT cutoff if ( !PvNode @@ -917,6 +954,7 @@ namespace { 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; @@ -948,8 +986,7 @@ moves_loop: // When in check, search starts here ss->ply); value = bestValue; - singularQuietLMR = moveCountPruning = false; - bool doubleExtension = false; + singularQuietLMR = moveCountPruning = noLMRExtension = 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. @@ -1005,7 +1042,7 @@ 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 - reduction(improving, depth, moveCount), 0); + int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0); if ( captureOrPromotion || givesCheck) @@ -1069,13 +1106,13 @@ moves_loop: // When in check, search starts 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; + noLMRExtension = true; } } @@ -1088,7 +1125,8 @@ moves_loop: // When in check, search starts here 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. + // move that pushes it over beta, if so the position also has probably multiple + // moves giving fail highs. We will then reduce the ttMove (negative extension). else if (ttValue >= beta) { ss->excludedMove = move; @@ -1096,7 +1134,7 @@ moves_loop: // When in check, search starts here ss->excludedMove = MOVE_NONE; if (value >= beta) - return beta; + extension = -2; } } @@ -1109,7 +1147,14 @@ moves_loop: // When in check, search starts here // 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 @@ -1140,13 +1185,13 @@ moves_loop: // When in check, search starts here || !ss->ttPv) && (!PvNode || ss->ply > 1 || thisThread->id() % 4 != 3)) { - Depth r = reduction(improving, depth, moveCount); + Depth r = reduction(improving, depth, moveCount, rangeReduction > 2); if (PvNode) r--; // Decrease reduction if the ttHit running average is large (~0 Elo) - if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024) + if (thisThread->ttHitAverage.is_greater(537, 1024)) r--; // Decrease reduction if position is or has been on the PV @@ -1185,13 +1230,24 @@ moves_loop: // When in check, search starts here // 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 in specific cases. - Depth d = std::clamp(newDepth - r, 1, newDepth + (r < -1 && (moveCount <= 5 || (depth > 6 && PvNode)) && !doubleExtension)); + // 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 if + // newDepth got its own extension before). + int deeper = r >= -1 ? 0 + : noLMRExtension ? 0 + : moveCount <= 5 ? 1 + : (depth > 6 && PvNode) ? 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;