From 9be0360aa414556f231873ce2348f9c1f00d1713 Mon Sep 17 00:00:00 2001 From: Michael Chaly Date: Mon, 18 Dec 2023 20:34:35 +0300 Subject: [PATCH] Adjust return value in qsearch after fail high Instead of returning strict fail soft fail high return value between value from search and beta (somewhat by analogy to futility pruning and probcut). This seems to be somewhat depth sensitive heuristic which performed much worse at LTC while performing much better at STC if it is more aggressive, passed version is the least aggressive one. Passed STC: https://tests.stockfishchess.org/tests/view/657b06414d789acf40ab1475 LLR: 2.95 (-2.94,2.94) <0.00,2.00> Total: 212352 W: 53900 L: 53315 D: 105137 Ptnml(0-2): 809, 25236, 53520, 25783, 828 Passed LTC: https://tests.stockfishchess.org/tests/view/657ce36f393ac02e79120a7c LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 319362 W: 79541 L: 78630 D: 161191 Ptnml(0-2): 202, 35839, 86709, 36708, 223 closes https://github.com/official-stockfish/Stockfish/pull/4928 Bench: 974739 --- src/search.cpp | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/search.cpp b/src/search.cpp index bd3da5a2..fad43b62 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1618,6 +1618,9 @@ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) { return mated_in(ss->ply); // Plies to mate from the root } + if (abs(bestValue) < VALUE_TB_WIN_IN_MAX_PLY) + bestValue = bestValue >= beta ? (3 * bestValue + beta) / 4 : bestValue; + // Save gathered info in transposition table tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, bestValue >= beta ? BOUND_LOWER : BOUND_UPPER, ttDepth, bestMove, ss->staticEval); -- 2.39.2