Re-implement double pawn penalty without iterating

lynx-chess · May 17, 2024 · 43641aa · 43641aa
1 parent 19b2ee9
commit 43641aa
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Showing 4 changed files with 65 additions and 38 deletions.
diff --git a/src/Lynx.Cli/appsettings.json b/src/Lynx.Cli/appsettings.json
@@ -62,6 +62,10 @@
       "MG": -21,
       "EG": -17
     },
+    "DoubledPawnPenalty": {
+      "MG": -5,
+      "EG": -5
+    },
     "OpenFileRookBonus": {
       "MG": 46,
       "EG": 9

diff --git a/src/Lynx/Configuration.cs b/src/Lynx/Configuration.cs
@@ -205,6 +205,8 @@ public sealed class EngineSettings
 
     public TaperedEvaluationTerm IsolatedPawnPenalty { get; set; } = new(-21, -17);
 
+    public TaperedEvaluationTerm DoubledPawnPenalty { get; set; } = new(-5, -5);
+
     public TaperedEvaluationTerm OpenFileRookBonus { get; set; } = new(46, 9);
 
     public TaperedEvaluationTerm SemiOpenFileRookBonus { get; set; } = new(15, 15);

diff --git a/src/Lynx/Model/Position.cs b/src/Lynx/Model/Position.cs
@@ -714,6 +714,9 @@ public bool WasProduceByAValidMove()
             }
         }
 
+        // Doubled pawns penalty
+        packedScore += DoublePawnPenalty();
+
         // Bishop pair bonus
         if (PieceBitBoards[(int)Piece.B].CountBits() >= 2)
         {
@@ -808,6 +811,15 @@ public bool WasProduceByAValidMove()
         return (sideEval, gamePhase);
     }
 
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private int DoublePawnsPenalty()
+    {
+        return ((PieceBitBoards[(int)Piece.P] & PieceBitBoards[(int)Piece.P].ShiftUp()).CountBits()
+            * Configuration.EngineSettings.DoubledPawnPenalty.PackedEvaluation)
+            - ((PieceBitBoards[(int)Piece.p] & PieceBitBoards[(int)Piece.p].ShiftUp()).CountBits()
+             * Configuration.EngineSettings.DoubledPawnPenalty.PackedEvaluation);
+    }
+
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     internal static int TaperedEvaluation(TaperedEvaluationTerm taperedEvaluationTerm, int phase)
     {
@@ -968,6 +980,16 @@ internal int KingAdditionalEvaluation(int squareIndex, Side kingSide)
         return packedBonus + (ownPiecesAroundCount * Configuration.EngineSettings.KingShieldBonus.PackedEvaluation);
     }
 
+    internal int DoublePawnPenalty()
+    {
+        var whitePawns = PieceBitBoards[(int)Piece.P];
+        var blackPawns = PieceBitBoards[(int)Piece.p];
+
+        return Configuration.EngineSettings.DoubledPawnPenalty.PackedEvaluation * (
+            (whitePawns & whitePawns.ShiftUp()).CountBits()
+            - (blackPawns & blackPawns.ShiftUp()).CountBits());
+    }
+
     #endregion
 
     #region Attacks

diff --git a/tests/Lynx.Test/Model/PositionTest.cs b/tests/Lynx.Test/Model/PositionTest.cs
@@ -230,25 +230,24 @@ public void StaticEvaluation_IsolatedPawnPenalty(string fen)
     ///     a b c d e f g h
     /// </summary>
     /// <param name="fen"></param>
-    //[TestCase("4k3/ppp5/8/8/8/P7/PP6/4K3 w - - 0 1")]
-    ///// <summary>
-    ///// Previous one mirrored
-    ///// </summary>
-    ///// <param name="fen"></param>
-    //[TestCase("3k4/6pp/7p/8/8/8/5PPP/3K4 b - - 0 1")]
-    //public void StaticEvaluation_DoublePawnPenalty(string fen)
-    //{
-    //    Position position = new Position(fen);
-    //    int evaluation = AdditionalPieceEvaluation(position, Piece.P)
-    //        - AdditionalPieceEvaluation(position, Piece.p);
-
-    //    if (position.Side == Side.Black)
-    //    {
-    //        evaluation = -evaluation;
-    //    }
-
-    //    Assert.AreEqual(4 * Configuration.EngineSettings.DoubledPawnPenalty.MG, evaluation);
-    //}
+    [TestCase("4k3/ppp5/8/8/8/P7/PP6/4K3 w - - 0 1")]
+    /// <summary>
+    /// Previous one mirrored
+    /// </summary>
+    /// <param name="fen"></param>
+    [TestCase("3k4/6pp/7p/8/8/8/5PPP/3K4 b - - 0 1")]
+    public void StaticEvaluation_DoublePawnPenalty(string fen)
+    {
+        Position position = new Position(fen);
+        int evaluation = position.DoublePawnPenalty();
+
+        if (position.Side == Side.Black)
+        {
+            evaluation = -evaluation;
+        }
+
+        Assert.AreEqual(1 * Configuration.EngineSettings.DoubledPawnPenalty.PackedEvaluation, evaluation);
+    }
 
     /// <summary>
     /// Illegal position, but avoids any positional bonuses
@@ -263,25 +262,25 @@ public void StaticEvaluation_IsolatedPawnPenalty(string fen)
     ///     a b c d e f g h
     /// </summary>
     /// <param name="fen"></param>
-    //[TestCase("7k/ppp2ppp/8/8/8/P7/PP4PP/P6K w - - 0 1")]
-    ///// <summary>
-    ///// Previous one mirrored
-    ///// </summary>
-    ///// <param name="fen"></param>
-    //[TestCase("k6p/pp4pp/7p/8/8/8/PPP2PPP/K7 b - - 0 1")]
-    //public void StaticEvaluation_TriplePawnPenalty(string fen)
-    //{
-    //    Position position = new Position(fen);
-    //    int evaluation = AdditionalPieceEvaluation(position, Piece.P)
-    //        - AdditionalPieceEvaluation(position, Piece.p);
-
-    //    if (position.Side == Side.Black)
-    //    {
-    //        evaluation = -evaluation;
-    //    }
-
-    //    Assert.AreEqual(9 * Configuration.EngineSettings.DoubledPawnPenalty.MG, evaluation);
-    //}
+    [TestCase("7k/ppp2ppp/8/8/8/P7/PP4PP/P6K w - - 0 1")]
+    /// <summary>
+    /// Previous one mirrored
+    /// </summary>
+    /// <param name="fen"></param>
+    [TestCase("k6p/pp4pp/7p/8/8/8/PPP2PPP/K7 b - - 0 1")]
+    public void StaticEvaluation_TriplePawnPenalty(string fen)
+    {
+        Position position = new Position(fen);
+        int evaluation = position.DoublePawnPenalty();
+
+
+        if (position.Side == Side.Black)
+        {
+            evaluation = -evaluation;
+        }
+
+        Assert.AreEqual(2 * Configuration.EngineSettings.DoubledPawnPenalty.PackedEvaluation, evaluation);
+    }
 
     /// <summary>
     /// 8   . . . . . . k .