From c2135c3190ca1684b1f64dbe2dd5a41900a775d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Eduardo=20C=C3=A1ceres?=
 <eduardo.caceresdelacalle@gmail.com>
Date: Wed, 8 Jan 2025 15:10:22 +0100
Subject: [PATCH] `LMP_BaseMovesToTry + (LMP_MovesDepthMultiplier * depth *
 (improving ? 2 : 1))` -> `LMP_BaseMovesToTry + (depth * depth / (improving ?
 1 : 2))`

---
 src/Lynx/Configuration.cs  | 5 +----
 src/Lynx/Search/NegaMax.cs | 2 +-
 src/Lynx/UCIHandler.cs     | 8 --------
 3 files changed, 2 insertions(+), 13 deletions(-)

diff --git a/src/Lynx/Configuration.cs b/src/Lynx/Configuration.cs
index a4df158a8..8b033e9c0 100644
--- a/src/Lynx/Configuration.cs
+++ b/src/Lynx/Configuration.cs
@@ -202,10 +202,7 @@ public int Threads
     public int LMP_MaxDepth { get; set; } = 8;
 
     [SPSA<int>(0, 10, 0.5)]
-    public int LMP_BaseMovesToTry { get; set; } = 1;
-
-    [SPSA<int>(0, 10, 0.5)]
-    public int LMP_MovesDepthMultiplier { get; set; } = 3;
+    public int LMP_BaseMovesToTry { get; set; } = 3;
 
     public int History_MaxMoveValue { get; set; } = 8_192;
 
diff --git a/src/Lynx/Search/NegaMax.cs b/src/Lynx/Search/NegaMax.cs
index 028abb81d..76cc3eb5b 100644
--- a/src/Lynx/Search/NegaMax.cs
+++ b/src/Lynx/Search/NegaMax.cs
@@ -320,7 +320,7 @@ void RevertMove()
                     // 🔍 Late Move Pruning (LMP) - all quiet moves can be pruned
                     // after searching the first few given by the move ordering algorithm
                     if (depth <= Configuration.EngineSettings.LMP_MaxDepth
-                        && moveIndex >= Configuration.EngineSettings.LMP_BaseMovesToTry + (Configuration.EngineSettings.LMP_MovesDepthMultiplier * depth * (improving ? 2 : 1))) // Based on formula suggested by Antares
+                        && moveIndex >= Configuration.EngineSettings.LMP_BaseMovesToTry + (depth * depth / (improving ? 1 : 2))) // Based on formula suggested by Antares
                     {
                         RevertMove();
                         break;
diff --git a/src/Lynx/UCIHandler.cs b/src/Lynx/UCIHandler.cs
index 7d1128b54..fa47d1b72 100644
--- a/src/Lynx/UCIHandler.cs
+++ b/src/Lynx/UCIHandler.cs
@@ -478,14 +478,6 @@ private void HandleSetOption(ReadOnlySpan<char> command)
                     }
                     break;
                 }
-            case "lmp_movesdepthmultiplier":
-                {
-                    if (length > 4 && int.TryParse(command[commandItems[4]], out var value))
-                    {
-                        Configuration.EngineSettings.LMP_MovesDepthMultiplier = value;
-                    }
-                    break;
-                }
             case "history_maxmovevalue":
                 {
                     if (length > 4 && int.TryParse(command[commandItems[4]], out var value))