From 8806a58ebf5ade73696fd1f89ac4ea12cd1eedd3 Mon Sep 17 00:00:00 2001
From: evqsx <149484438+evqsx@users.noreply.github.com>
Date: Sun, 16 Jun 2024 12:34:24 +0800
Subject: [PATCH] Simplify static exchange evaluation pruning formula

Passed STC: https://tests.stockfishchess.org/tests/view/666bda31602682471b064e1f
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 141696 W: 36932 L: 36826 D: 67938
Ptnml(0-2): 510, 16880, 35989, 16932, 537

Passed LTC: https://tests.stockfishchess.org/tests/view/666e6b67602682471b064f4b
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 159504 W: 40552 L: 40471 D: 78481
Ptnml(0-2): 130, 18160, 43103, 18217, 142

closes https://github.com/official-stockfish/Stockfish/pull/5400

bench: 1084115
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 75eea2fd..9b296e7f 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1586,7 +1586,7 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta,
 
                 // If static exchange evaluation is much worse than what is needed to not
                 // fall below alpha we can prune this move.
-                if (futilityBase > alpha && !pos.see_ge(move, (alpha - futilityBase) * 2 - 30))
+                if (futilityBase > alpha && !pos.see_ge(move, (alpha - futilityBase) * 4))
                 {
                     bestValue = alpha;
                     continue;