From b0ac8a4e3bad2ed1b066850b6f151ddbe48d1dc6 Mon Sep 17 00:00:00 2001
From: Gahtan Nahdi <155860115+gahtan-syarif@users.noreply.github.com>
Date: Thu, 22 Feb 2024 04:37:26 +0700
Subject: [PATCH] Simplify extension when ttMove is assumed to fail high over
 current beta

Simplify extension value to -3 when ttMove is assumed to fail high over current beta.

Passed non-reg STC:
https://tests.stockfishchess.org/tests/view/65d66ed81d8e83c78bfddcba
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 235136 W: 60711 L: 60708 D: 113717
Ptnml(0-2): 969, 27904, 59874, 27797, 1024

Passed non-reg LTC:
https://tests.stockfishchess.org/tests/view/65da2994944f2a78d4733107
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 662850 W: 166161 L: 166602 D: 330087
Ptnml(0-2): 394, 74895, 181274, 74482, 380

closes https://github.com/official-stockfish/Stockfish/pull/5088

Bench: 1553115
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 951e206c..70baffe3 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1056,7 +1056,7 @@ moves_loop:  // When in check, search starts here
 
                 // If the ttMove is assumed to fail high over current beta (~7 Elo)
                 else if (ttValue >= beta)
-                    extension = -2 - !PvNode;
+                    extension = -3;
 
                 // If we are on a cutNode but the ttMove is not assumed to fail high over current beta (~1 Elo)
                 else if (cutNode)