Add rook pair bonus

lynx-chess · Jan 5, 2025 · 006031c · 006031c
1 parent 4083bca
commit 006031c
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Showing 2 changed files with 16 additions and 0 deletions.
diff --git a/src/Lynx/Model/Position.cs b/src/Lynx/Model/Position.cs
@@ -482,6 +482,17 @@ public bool WasProduceByAValidMove()
             packedScore -= BishopPairBonus;
         }
 
+        // Rook pair bonus
+        if (PieceBitBoards[(int)Piece.R].CountBits() == 2)
+        {
+            packedScore += RookPairBonus;
+        }
+
+        if (PieceBitBoards[(int)Piece.r].CountBits() == 2)
+        {
+            packedScore -= RookPairBonus;
+        }
+
         // Pieces attacked by pawns bonus
         packedScore += PieceAttackedByPawnPenalty
             * ((blackPawnAttacks & OccupancyBitBoards[(int)Side.White] /* & (~whitePawns) */).CountBits()

diff --git a/src/Lynx/TunableEvalParameters.cs b/src/Lynx/TunableEvalParameters.cs
@@ -6048,6 +6048,11 @@ public static class EvaluationParams
 	/// </summary>
 	public const int BishopPairBonus = 4653086;
 
+	/// <summary>
+	/// <see cref="Utils.Pack(30, 71)"/>
+	/// </summary>
+	public const int RookPairBonus = 4653086;
+
 	/// <summary>
 	/// <see cref="Utils.Pack(-48, -33)"/>
 	/// </summary>