private void AddBishopAttack(SortedDictionary <int, SquareFlag> dictionary, int squareIndex, SquareFlag currentOccupancy)
{
var magicIndex = MagicIndexHelpers.GetBishopMagicIndex(squareIndex, currentOccupancy);
var attack = AttackGenerator.GeneratePotentialBishopAttacks(squareIndex, currentOccupancy);
var indexTaken = dictionary.ContainsKey(magicIndex) && dictionary[magicIndex] != attack;
if (indexTaken)
{
throw new Exception($"Magic Index {magicIndex} already in use by a different attack");
}
dictionary[magicIndex] = attack;
}
private SquareFlag GetAttackableSquares(Square fromSquare, PieceType rayType, SquareFlag occupiedSquares)
{
var occupancyMask = rayType == PieceType.Rook
? MagicNumbers.RookOccupancyMasks[fromSquare.Index]
: MagicNumbers.BishopOccupancyMasks[fromSquare.Index];
var occupancyMasked = occupiedSquares & occupancyMask;
var magicIndex = MagicIndexHelpers.GetMagicIndex(rayType, fromSquare.Index, occupancyMasked);
var attackableSquaresIncludingSelfCaptures = rayType == PieceType.Rook
? AttackBitmaps.RookAttacks[fromSquare.Index][magicIndex]
: AttackBitmaps.BishopAttacks[fromSquare.Index][magicIndex];
return(attackableSquaresIncludingSelfCaptures);
}
private void AddIndividualPawnCaptures(MoveGenerationWorkspace workspace, Square fromSquare, SquareFlag pushMask, SquareFlag captureMask)
{
var relativeBitBoard = workspace.RelativeBitBoard;
var captureSquares = relativeBitBoard.Colour == Colour.White
? AttackBitmaps.PawnCapturesWhite[fromSquare.Index].ToList()
: AttackBitmaps.PawnCapturesBlack[fromSquare.Index].ToList();
foreach (var toSquare in captureSquares)
{
var moveType = relativeBitBoard.EnPassant.HasFlag(toSquare) ? MoveType.EnPassant : MoveType.Ordinary;
if (relativeBitBoard.OpponentSquares.HasFlag(toSquare) || moveType == MoveType.EnPassant)
{
var capturePieceType = relativeBitBoard.GetPieceType(toSquare);
var discoveredCheck = false;
if (moveType != MoveType.EnPassant)
{
if (!captureMask.HasFlag(toSquare))
{
continue;
}
}
else
{
// Abuse the push system - push an imaginary pawn from the en passant square as opponent to find piece
var enPassantCaptureSquare = relativeBitBoard.EnPassant.PawnForward(relativeBitBoard.OpponentColour, 1);
var blockWithPush = pushMask.HasFlag(relativeBitBoard.EnPassant);
var evadeWithCapture = captureMask.HasFlag(enPassantCaptureSquare);
if (!blockWithPush && !evadeWithCapture)
{
continue;
}
capturePieceType = PieceType.Pawn;
// Looking for DISCOVERED CHECK (not spotted by pinned pieces as there are 2 pawns in the way)
// Slight duplication here but probably cleaner than passing in
var kingSquare = relativeBitBoard.MyKing.ToSquare();
var enPassantDiscoveredCheckRank = relativeBitBoard.EnPassantDiscoveredCheckRank;
// This should be super rare. Performing an en passant capture with our King on same rank.
if (enPassantDiscoveredCheckRank.HasFlag(kingSquare.Flag))
{
if ((enPassantDiscoveredCheckRank & relativeBitBoard.OpponentRooks) > 0 ||
(enPassantDiscoveredCheckRank & relativeBitBoard.OpponentQueens) > 0)
{
var occupancyMask = MagicNumbers.RookOccupancyMasks[kingSquare.Index];
var occupancyBeforeCapture = relativeBitBoard.OccupiedSquares & occupancyMask;
var occupancyAfterCapture = occupancyBeforeCapture
& ~enPassantCaptureSquare
& ~fromSquare.Flag;
// Search for magic moves using just the occupancy of rank (the rest is not relevant)
var magicIndex = MagicIndexHelpers.GetMagicIndex(PieceType.Rook, kingSquare.Index, occupancyAfterCapture);
var kingRayAttacks = AttackBitmaps.RookAttacks[kingSquare.Index][magicIndex];
var kingRayAttacksOnRank = kingRayAttacks & enPassantDiscoveredCheckRank;
discoveredCheck = (kingRayAttacksOnRank & relativeBitBoard.OpponentRooks) > 0 ||
(kingRayAttacksOnRank & relativeBitBoard.OpponentQueens) > 0;
}
}
}
if (relativeBitBoard.PromotionRank.HasFlag(toSquare))
{
AddPromotions(workspace, fromSquare, toSquare.ToSquare(), capturePieceType);
}
else if (!discoveredCheck)
{
if (capturePieceType != PieceType.None)
{
workspace.CaptureMoveBuffer.Add(MoveBuilder.Create(workspace.Colour, PieceType.Pawn, fromSquare, toSquare.ToSquare(), capturePieceType, moveType, workspace.NumCheckers));
}
else
{
workspace.NonCaptureMoveBuffer.Add(MoveBuilder.Create(workspace.Colour, PieceType.Pawn, fromSquare, toSquare.ToSquare(), capturePieceType, moveType, workspace.NumCheckers));
}
}
}
}
}
