From c787509663dface7637dc3985bab516070736678 Mon Sep 17 00:00:00 2001
From: FauziAkram <fauzi.dabat@hotmail.com>
Date: Sun, 26 Apr 2026 09:35:12 +0200
Subject: [PATCH] Simplify time management reduction logic

Simplify the time management reduction logic by replacing the previous sigmoid
function with the linear interpolate function introduced in #6729 , resulting
in a cleaner and more efficient calculation of move stability that avoids
unnecessary exponential operations.

Passed STC non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 161856 W: 41933 L: 41852 D: 78071
Ptnml(0-2): 418, 18137, 43792, 18108, 473
https://tests.stockfishchess.org/tests/view/69e117a46f344a1917600148

Passed LTC non-reg:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 108726 W: 27819 L: 27692 D: 53215
Ptnml(0-2): 59, 11084, 31942, 11227, 51
https://tests.stockfishchess.org/tests/view/69e563c00e9667dd5a7652ac

This is a follow-up for #6091  #6729

closes https://github.com/official-stockfish/Stockfish/pull/6765

No functional change
---
 src/search.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index abb229eaf..282b379b6 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -524,10 +524,9 @@ bool Search::Worker::iterative_deepening() {
             fallingEval = std::clamp(fallingEval, 0.581, 1.655);
 
             // If the bestMove is stable over several iterations, reduce time accordingly
-            double k      = 0.476;
-            double center = lastBestMoveDepth + 11.565;
-
-            timeReduction = 0.64 + 0.93 / (0.953 + std::exp(-k * (completedDepth - center)));
+            timeReduction = std::clamp(
+              interpolate(double(completedDepth - lastBestMoveDepth), 5.0, 18.0, 0.65, 1.55), 0.65,
+              1.55);
 
             double reduction = (1.5 + mainThread->previousTimeReduction) / (2.255 * timeReduction);