From 70ff5e31635384504f6f5cce9c0f089d60103922 Mon Sep 17 00:00:00 2001
From: Daniel Monroe <github.com@danielmonroe.net>
Date: Mon, 26 May 2025 23:47:35 -0700
Subject: [PATCH] Simplify away cutoff term in prior countermove bonus

Passed simplification STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 61120 W: 16010 L: 15819 D: 29291
Ptnml(0-2): 150, 7105, 15869, 7276, 160
https://tests.stockfishchess.org/tests/view/683560226ec7634154f9ce0f

Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 225090 W: 57555 L: 57543 D: 109992
Ptnml(0-2): 104, 24367, 63603, 24355, 116
https://tests.stockfishchess.org/tests/view/6836420c6ec7634154f9cf5c

closes https://github.com/official-stockfish/Stockfish/pull/6111

Bench: 2472910
---
 src/search.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index 8b8c3d6d..f7390bc2 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1431,11 +1431,10 @@ moves_loop:  // When in check, search starts here
     // Bonus for prior quiet countermove that caused the fail low
     else if (!priorCapture && prevSq != SQ_NONE)
     {
-        int bonusScale = -302;
+        int bonusScale = -220;
         bonusScale += std::min(-(ss - 1)->statScore / 103, 323);
         bonusScale += std::min(73 * depth, 531);
         bonusScale += 174 * ((ss - 1)->moveCount > 8);
-        bonusScale += 90 * (ss->cutoffCnt <= 3);
         bonusScale += 144 * (!ss->inCheck && bestValue <= ss->staticEval - 104);
         bonusScale += 128 * (!(ss - 1)->inCheck && bestValue <= -(ss - 1)->staticEval - 82);