From b1053e60b7e0fe3187006c4d7f38dbd22eaff763 Mon Sep 17 00:00:00 2001
From: FauziAkram <fauzi.dabat@hotmail.com>
Date: Fri, 29 May 2026 19:06:38 +0200
Subject: [PATCH] Simplify Internal Iterative Reductions (IIR) Condition

Passed STC non-reg:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 75840 W: 19367 L: 19192 D: 37281
Ptnml(0-2): 186, 8837, 19710, 8990, 197
https://tests.stockfishchess.org/tests/view/6a0b02ba6524d21ee79b8685

Passed LTC non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 166920 W: 42039 L: 41967 D: 82914
Ptnml(0-2): 78, 18155, 46919, 18233, 75
https://tests.stockfishchess.org/tests/view/6a0c98fb6524d21ee79b8875

Passed VTC non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 46390 W: 11914 L: 11729 D: 22747
Ptnml(0-2): 8, 4543, 13911, 4722, 11
https://tests.stockfishchess.org/tests/view/6a143877818cacc1db0ac7c5

closes https://github.com/official-stockfish/Stockfish/pull/6861

Bench: 2814421
---
 src/search.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/search.cpp b/src/search.cpp
index 9bc3fcc1d..12169dede 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -989,7 +989,7 @@ Value Search::Worker::search(
     // Step 10. Internal iterative reductions
     // At sufficient depth, reduce depth for PV/Cut nodes without a TTMove.
     // (*Scaler) Making IIR more aggressive scales poorly.
-    if (!ss->followPV && !allNode && depth >= 6 && !ttData.move && priorReduction <= 3)
+    if (!ss->followPV && !allNode && depth >= 6 && !ttData.move)
         depth--;
 
     // Step 11. ProbCut