From c9c002450a52f0b2315af65ebfb767024b33e136 Mon Sep 17 00:00:00 2001 From: Daniel Monroe Date: Sat, 9 Aug 2025 11:21:41 -0400 Subject: [PATCH] Simplify depth term in reductions Passed simplification STC LLR: 2.93 (-2.94,2.94) <-1.75,0.25> Total: 317344 W: 82352 L: 82442 D: 152550 Ptnml(0-2): 999, 37395, 81907, 37439, 932 https://tests.stockfishchess.org/tests/live_elo/68976798f8a258623dda6c46 Passed simplification LTC LLR: 2.97 (-2.94,2.94) <-1.75,0.25> Total: 291708 W: 74733 L: 74787 D: 142188 Ptnml(0-2): 159, 31813, 81956, 31775, 151 https://tests.stockfishchess.org/tests/live_elo/689791a5f8a258623dda6d03 closes https://github.com/official-stockfish/Stockfish/pull/6225 Bench: 2436991 --- src/search.cpp | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/src/search.cpp b/src/search.cpp index b4569d9a5..6687ecb22 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1251,13 +1251,12 @@ moves_loop: // When in check, search starts here if (!ttData.move) r += 1199 + 35 * msb(depth); - const int threshold1 = depth <= 4 ? 2000 : 3200; - const int threshold2 = depth <= 4 ? 3500 : 4600; + if (depth <= 4) + r += 1150; // Note that if expected reduction is high, we reduce search depth here value = -search(pos, ss + 1, -(alpha + 1), -alpha, - newDepth - (r > threshold1) - (r > threshold2 && newDepth > 2), - !cutNode); + newDepth - (r > 3200) - (r > 4600 && newDepth > 2), !cutNode); } // For PV nodes only, do a full PV search on the first move or after a fail high,