From 89b4f457e0ea492dfc17042392b9bc91e350ef76 Mon Sep 17 00:00:00 2001
From: Daniel Monroe <github.com@danielmonroe.net>
Date: Mon, 2 Feb 2026 17:14:29 -0500
Subject: [PATCH] Simplify malus decay formula

Passed non-regression STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 93600 W: 24165 L: 24007 D: 45428
Ptnml(0-2): 325, 11021, 23958, 11163, 333
https://tests.stockfishchess.org/tests/view/698121d46362aee5c8a55414

Passed non-regression LTC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 83232 W: 21236 L: 21077 D: 40919
Ptnml(0-2): 46, 9147, 23083, 9282, 58
https://tests.stockfishchess.org/tests/view/698336dc473df9d1d24a90e8

closes https://github.com/official-stockfish/Stockfish/pull/6600

Bench: 2666284
---
 src/search.cpp | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index fe795f5ee..ef3f9cbad 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1837,14 +1837,11 @@ void update_all_stats(const Position& pos,
     {
         update_quiet_histories(pos, ss, workerThread, bestMove, bonus * 910 / 1024);
 
-        int i = 0;
+        int actualMalus = malus * 1100 / 1024;
         // Decrease stats for all non-best quiet moves
         for (Move move : quietsSearched)
         {
-            i++;
-            int actualMalus = malus * 1085 / 1024;
-            if (i > 5)
-                actualMalus -= actualMalus * (i - 5) / i;
+            actualMalus = actualMalus * 950 / 1024;
             update_quiet_histories(pos, ss, workerThread, move, -actualMalus);
         }
     }