From d9ec82e7438716671168d78eee26fae327249e8c Mon Sep 17 00:00:00 2001 From: Michael Chaly Date: Fri, 15 Dec 2023 01:51:52 +0300 Subject: [PATCH] Adjust stand pat in qsearch on pv nodes Instead of immediately returning a fail high do this only at non-pv nodes, for pv nodes adjust bestValue to value between alpha and beta and continue searching. Idea is to do it the same way as it's done in search where we don't return positive beta cutoffs after ttHits / zero window search at PvNodes and instead fully search lines. Passed STC: https://tests.stockfishchess.org/tests/view/65739b0af09ce1261f122f33 LLR: 2.94 (-2.94,2.94) <0.00,2.00> Total: 189216 W: 48142 L: 47598 D: 93476 Ptnml(0-2): 584, 22463, 48051, 22845, 665 Passed LTC: https://tests.stockfishchess.org/tests/view/657701214d789acf40aac194 LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 82506 W: 20689 L: 20269 D: 41548 Ptnml(0-2): 56, 9236, 22268, 9618, 75 Two issues had to be resolved: - in rare cases it set alpha to the same value as beta and thus broke some asserts; - messed up with returning tb win values. Fix passed non-regression LTC vs this patch: https://tests.stockfishchess.org/tests/view/6578113b4d789acf40aad544 LLR: 2.96 (-2.94,2.94) <-1.75,0.25> Total: 277308 W: 68839 L: 68880 D: 139589 Ptnml(0-2): 167, 31580, 75212, 31517, 178 closes https://github.com/official-stockfish/Stockfish/pull/4922 Bench: 1069503 Co-Authored-By: Muzhen Gaming <61100393+XInTheDark@users.noreply.github.com> Co-Authored-By: Shahin M. Shahin <41402573+peregrineshahin@users.noreply.github.com> Co-Authored-By: fffelix-huang <72808219+fffelix-huang@users.noreply.github.com> --- src/search.cpp | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/src/search.cpp b/src/search.cpp index 10a36cbf..27c2c84e 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1468,14 +1468,19 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { ss->staticEval = bestValue = (ss - 1)->currentMove != MOVE_NULL ? evaluate(pos) : -(ss - 1)->staticEval; - // Stand pat. Return immediately if static value is at least beta + // Stand pat. Return immediately if bestValue is at least beta at non-Pv nodes. + // At PvNodes set bestValue between alpha and beta instead if (bestValue >= beta) { - if (!ss->ttHit) - tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, DEPTH_NONE, - MOVE_NONE, ss->staticEval); + if (!PvNode || abs(bestValue) >= VALUE_TB_WIN_IN_MAX_PLY) + { + if (!ss->ttHit) + tte->save(posKey, value_to_tt(bestValue, ss->ply), false, BOUND_LOWER, + DEPTH_NONE, MOVE_NONE, ss->staticEval); - return bestValue; + return bestValue; + } + bestValue = std::min((alpha + beta) / 2, beta - 1); } if (bestValue > alpha) -- 2.39.2