From 9cc15b30490675713466b6746d4afdce5c715bd6 Mon Sep 17 00:00:00 2001
From: Michael Chaly <Vizvezdenec@gmail.com>
Date: Wed, 12 Feb 2025 01:53:41 +0300
Subject: [PATCH] Do more reductions for cut nodes without a tt move

Logic is somewhat similar to IIR but in LMR.
Usually things like reducing more in IIR scale badly but this patch does
this in LMR where reducing more for cutNodes is in general good, so I
believe there is no non-linear scaling.

Passed STC:
https://tests.stockfishchess.org/tests/view/67abc9aaa04df5eb8dbeb452
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 42304 W: 11223 L: 10892 D: 20189
Ptnml(0-2): 184, 4904, 10669, 5187, 208

Passed LTC:
https://tests.stockfishchess.org/tests/view/67abcd7ba04df5eb8dbeb96c
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 32334 W: 8386 L: 8074 D: 15874
Ptnml(0-2): 26, 3446, 8916, 3748, 31

closes https://github.com/official-stockfish/Stockfish/pull/5875

Bench: 2612849
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 4dfdbaaf..4bc6109e 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1169,7 +1169,7 @@ moves_loop:  // When in check, search starts here
 
         // Increase reduction for cut nodes
         if (cutNode)
-            r += 2608;
+            r += 2608 + 1024 * !ttData.move;
 
         // Increase reduction if ttMove is a capture but the current move is not a capture
         if (ttCapture && !capture)