diff --git a/AUTHORS b/AUTHORS index 5b5bbf22b67..fe22d57727e 100644 --- a/AUTHORS +++ b/AUTHORS @@ -193,6 +193,7 @@ Unai Corzo (unaiic) Uri Blass (uriblass) Vince Negri (cuddlestmonkey) zz4032 +Ofek Shochat (ghostway) # Additionally, we acknowledge the authors and maintainers of fishtest, diff --git a/src/search.cpp b/src/search.cpp index 9b56bd2b083..5dc9060db38 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) { @@ -955,6 +955,7 @@ namespace { ttCapture = ttMove && pos.capture_or_promotion(ttMove); + int rangeReduction = 0; // Step 11. A small Probcut idea, when we are in check probCutBeta = beta + 409; if ( ss->inCheck @@ -1041,7 +1042,7 @@ namespace { 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) @@ -1176,7 +1177,7 @@ namespace { || !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--; @@ -1236,6 +1237,11 @@ namespace { value = -search(pos, ss+1, -(alpha+1), -alpha, d, true); + // Range reductions (~3 Elo) + if (ss->staticEval - value < 30 && depth > 7) { + rangeReduction += 1; + } + // If the son is reduced and fails high it will be re-searched at full depth doFullDepthSearch = value > alpha && d < newDepth; didLMR = true;