Add parameter for multiplier

lynx-chess · Nov 21, 2023 · ed894ef · ed894ef
1 parent befc6dd
commit ed894ef
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Showing 3 changed files with 18 additions and 17 deletions.
diff --git a/src/Lynx.Cli/appsettings.json b/src/Lynx.Cli/appsettings.json
@@ -39,7 +39,8 @@
     "IIR_MinDepth": 4,
 
     "LMP_MaxDepth": 3,
-    "LMP_BaseMovesToTry": 3,
+    "LMP_BaseMovesToTry": 0,
+    "LMP_MovesDepthMultiplier": 5,
 
     "History_MaxMoveValue": 8192,
 

diff --git a/src/Lynx/Configuration.cs b/src/Lynx/Configuration.cs
@@ -151,7 +151,9 @@ public sealed class EngineSettings
 
     public int LMP_MaxDepth { get; set; } = 3;
 
-    public int LMP_BaseMovesToTry { get; set; } = 3;
+    public int LMP_BaseMovesToTry { get; set; } = 0;
+
+    public int LMP_MovesDepthMultiplier { get; set; } = 5;
 
     public int History_MaxMoveValue { get; set; } = 8_192;
 

diff --git a/src/Lynx/Search/NegaMax.cs b/src/Lynx/Search/NegaMax.cs
@@ -153,8 +153,7 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
         }
 
         var nodeType = NodeType.Alpha;
-        int movesSearched = 0;
-        int quietMovesSearched = 0;
+        int quietMovesSearchedCount = 0;
         Move? bestMove = null;
         bool isAnyMoveValid = false;
 
@@ -183,20 +182,20 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
             }
         }
 
-        for (int i = 0; i < pseudoLegalMoves.Length; ++i)
+        for (int moveIndex = 0; moveIndex < pseudoLegalMoves.Length; ++moveIndex)
         {
             // Incremental move sorting, inspired by https://github.com/jw1912/Chess-Challenge and suggested by toanth
             // There's no need to sort all the moves since most of them don't get checked anyway
             // So just find the first unsearched one with the best score and try it
-            for (int j = i + 1; j < pseudoLegalMoves.Length; j++)
+            for (int j = moveIndex + 1; j < pseudoLegalMoves.Length; j++)
             {
-                if (scores[j] > scores[i])
+                if (scores[j] > scores[moveIndex])
                 {
-                    (scores[i], scores[j], pseudoLegalMoves[i], pseudoLegalMoves[j]) = (scores[j], scores[i], pseudoLegalMoves[j], pseudoLegalMoves[i]);
+                    (scores[moveIndex], scores[j], pseudoLegalMoves[moveIndex], pseudoLegalMoves[j]) = (scores[j], scores[moveIndex], pseudoLegalMoves[j], pseudoLegalMoves[moveIndex]);
                 }
             }
 
-            var move = pseudoLegalMoves[i];
+            var move = pseudoLegalMoves[moveIndex];
 
             var gameState = position.MakeMove(move);
 
@@ -226,7 +225,7 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
                 // don't belong to this line and if this move were to beat alpha, they'd incorrectly copied to pv line.
                 Array.Clear(_pVTable, nextPvIndex, _pVTable.Length - nextPvIndex);
             }
-            else if (pvNode && movesSearched == 0)
+            else if (pvNode && moveIndex == 0)
             {
                 evaluation = -NegaMax(depth - 1, ply + 1, -beta, -alpha);
             }
@@ -237,8 +236,8 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
                 if (!pvNode
                     && !isInCheck
                     && depth <= Configuration.EngineSettings.LMP_MaxDepth
-                    && scores[i] < EvaluationConstants.PromotionMoveScoreValue  // Quiet moves
-                    && quietMovesSearched >= 10 * depth) // Based on SP and Altair
+                    && scores[moveIndex] < EvaluationConstants.PromotionMoveScoreValue  // Quiet moves
+                    && quietMovesSearchedCount >= Configuration.EngineSettings.LMP_BaseMovesToTry + (Configuration.EngineSettings.LMP_MovesDepthMultiplier * depth)) // Based on SP and Altair
                 {
                     // After making a move
                     Game.HalfMovesWithoutCaptureOrPawnMove = oldValue;
@@ -255,12 +254,12 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
 
                 // 🔍 Late Move Reduction (LMR) - search with reduced depth
                 // Impl. based on Ciekce advice (Stormphrax) and Stormphrax & Akimbo implementations
-                if (movesSearched >= (pvNode ? Configuration.EngineSettings.LMR_MinFullDepthSearchedMoves : Configuration.EngineSettings.LMR_MinFullDepthSearchedMoves - 1)
+                if (moveIndex >= (pvNode ? Configuration.EngineSettings.LMR_MinFullDepthSearchedMoves : Configuration.EngineSettings.LMR_MinFullDepthSearchedMoves - 1)
                     && depth >= Configuration.EngineSettings.LMR_MinDepth
                     && !isInCheck
                     && !move.IsCapture())
                 {
-                    reduction = EvaluationConstants.LMRReductions[depth, movesSearched];
+                    reduction = EvaluationConstants.LMRReductions[depth, moveIndex];
 
                     if (pvNode)
                     {
@@ -344,10 +343,9 @@ private int NegaMax(int depth, int ply, int alpha, int beta, bool parentWasNullM
                 nodeType = NodeType.Exact;
             }
 
-            ++movesSearched;
-            if (scores[i] < EvaluationConstants.PromotionMoveScoreValue)
+            if (scores[moveIndex] < EvaluationConstants.PromotionMoveScoreValue)
             {
-                ++quietMovesSearched;
+                ++quietMovesSearchedCount;
             }
         }