From 64e8e1b247367018ebbce15f0d7cf5a56c7eaf56 Mon Sep 17 00:00:00 2001
From: aronpetkovski <aronpetko@gmail.com>
Date: Sun, 27 Jul 2025 13:07:47 +0200
Subject: [PATCH] Simplify LMR extension limit formula

This patch simplifies the maximum depth formula that reductions in LMR can allow.

Passed STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 35616 W: 9358 L: 9139 D: 17119
Ptnml(0-2): 101, 4051, 9278, 4284, 94
https://tests.stockfishchess.org/tests/view/688608cf966ed85face24882

Passed LTC
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 22284 W: 5833 L: 5613 D: 10838
Ptnml(0-2): 8, 2367, 6173, 2585, 9
https://tests.stockfishchess.org/tests/view/68860d7f966ed85face248d5

closes https://github.com/official-stockfish/Stockfish/pull/6191

Bench: 2902492
---
 src/search.cpp | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index 743f4bce7..6503cc14d 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1219,9 +1219,7 @@ moves_loop:  // When in check, search starts here
             // beyond the first move depth.
             // To prevent problems when the max value is less than the min value,
             // std::clamp has been replaced by a more robust implementation.
-            Depth d = std::max(1, std::min(newDepth - r / 1024,
-                                           newDepth + !allNode + (PvNode && !bestMove)))
-                    + PvNode;
+            Depth d = std::max(1, std::min(newDepth - r / 1024, newDepth + 1 + PvNode)) + PvNode;
 
             ss->reduction = newDepth - d;
             value         = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, d, true);