X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=28049e87dcd8dd49a4f21242c88bf8ffa1d9a1bd;hp=9b56bd2b08325cf3d871a8a49ec57b352c0c67b6;hb=673841301b0cc6ed78c4db3e6ec2a0b9a010c8cb;hpb=ff3fa0c664a5799e5531b0908018c59633d761bf diff --git a/src/search.cpp b/src/search.cpp index 9b56bd2b..28049e87 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -69,9 +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) { @@ -80,7 +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 @@ -173,7 +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)); } @@ -591,13 +591,13 @@ namespace { bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularQuietLMR, noLMRExtension; Piece movedPiece; - int moveCount, captureCount, quietCount; + int moveCount, captureCount, quietCount, bestMoveCount; // Step 1. Initialize node 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; @@ -790,7 +790,6 @@ 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 @@ -954,6 +953,7 @@ 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; @@ -1041,7 +1041,7 @@ 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) @@ -1123,17 +1123,9 @@ moves_loop: // When in check, search starts 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 @@ -1145,7 +1137,14 @@ 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 @@ -1176,9 +1175,11 @@ 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) + // Decrease reduction if on the PV (~2 Elo) + if ( PvNode + && bestMoveCount <= 3) r--; // Decrease reduction if the ttHit running average is large (~0 Elo) @@ -1221,11 +1222,10 @@ 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 (note that - // this may lead to hidden double extensions if newDepth got it own extension - // before). + // 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 @@ -1236,6 +1236,10 @@ moves_loop: // When in check, search starts here 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; @@ -1302,9 +1306,11 @@ moves_loop: // When in check, search starts 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 @@ -1326,7 +1332,10 @@ moves_loop: // When in check, search starts 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 @@ -1485,7 +1494,6 @@ moves_loop: // When in check, search starts 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; @@ -1695,8 +1703,8 @@ moves_loop: // When in check, search starts 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)) {