From 81e21a69f02164fd988d5636a47c8790a1174b81 Mon Sep 17 00:00:00 2001
From: Stefan Geschwentner <stgeschwentner@gmail.com>
Date: Sun, 19 May 2024 10:12:05 +0200
Subject: [PATCH] Simplify the recently introduced ply-based cmh bonus factor.

Replace it with a constant which is an approximation of the limit of the factor.

STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 120064 W: 30967 L: 30836 D: 58261
Ptnml(0-2): 421, 14238, 30608, 14319, 446
https://tests.stockfishchess.org/tests/view/6649d146b8fa20e74c39f4ad

LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 53856 W: 13719 L: 13530 D: 26607
Ptnml(0-2): 31, 5879, 14922, 6062, 34
https://tests.stockfishchess.org/tests/view/664a027fae57c1758ac5b4ee

closes https://github.com/official-stockfish/Stockfish/pull/5270

Bench: 1355618
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 2618b984..7e95dd87 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1779,7 +1779,7 @@ void update_all_stats(const Position& pos,
 // by moves at ply -1, -2, -3, -4, and -6 with current move.
 void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) {
 
-    bonus = bonus * (112 * ss->ply + 136) / (159 * ss->ply + 124);
+    bonus = bonus * 45 / 64;
 
     for (int i : {1, 2, 3, 4, 6})
     {