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⚖ Add bonus for QRB knight forks if they include the king and the knight isn't attacked by pawns #1197

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⚖ Add bonus for QRB knight forks if they include the king and the knight isn't attacked by pawns #1197

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735f4ba
Add bonus for KQR forks
eduherminio Nov 22, 2024
3269090
Include bishops
eduherminio Nov 22, 2024
2220b61
Only when double implies check
eduherminio Nov 22, 2024
57497ae
Only if knight not attacked
eduherminio Nov 22, 2024
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5 changes: 5 additions & 0 deletions ...Lynx/Generated/Lynx.Generator/Lynx.Generator.GeneratedPackGenerator/EvaluationParams.g.cs
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Expand Up @@ -47,4 +47,9 @@ static partial class EvaluationParams
/// </summary>
public const int PieceAttackedByPawnPenalty = -2162735;

/// <summary>
/// <see cref="Utils.Pack(45, 31)"/>
/// </summary>
public const int KnightForkBounus = 2031661;

}
13 changes: 13 additions & 0 deletions src/Lynx/Model/Position.cs
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@@ -1,5 +1,6 @@
using System.Buffers;
using System.Diagnostics;
using System.Drawing;
using System.Runtime.CompilerServices;
using System.Text;

Expand Down Expand Up @@ -732,6 +733,18 @@ private int KnightAdditionalEvaluation(int squareIndex, int pieceSide, int oppos

packedBonus += CheckBonus[(int)Piece.N] * checks;

// Forks
if (attacks.GetBit(oppositeSideKingSquare) && !enemyPawnAttacks.GetBit(squareIndex))
{
var offset = Utils.PieceOffset(pieceSide);
var attackedOponentPieces = PieceBitBoards[(int)Piece.q - offset]
| PieceBitBoards[(int)Piece.r - offset]
| PieceBitBoards[(int)Piece.b - offset];

var enemyPiecesAttackedCount = (attacks & attackedOponentPieces).CountBits();
packedBonus += KnightForkBounus * enemyPiecesAttackedCount;
}

return packedBonus;
}

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