public static int[] GenerateOffsets(Bitboard bitboard)
{
int[] result = new int[Bitboards.CountBits(bitboard)];
int cnt = 0;
while (bitboard != 0)
{
result[cnt++] = Bitboards.BitScanForward(bitboard);
Bitboards.PopLsb(ref bitboard);
}
return(result);
}
public static Bitboard[] GeneratePermutations(Bitboard occupancyBitboard)
{
int numBits = Bitboards.CountBits(occupancyBitboard);
int numPossibilities = (int)Math.Pow(2, numBits);
int[] offsets = GenerateOffsets(occupancyBitboard);
Bitboard[] result = new Bitboard[numPossibilities];
for (int i = 0; i < numPossibilities; i++)
{
for (int bit = 0; bit < numBits; bit++)
{
bool bitIsSet = (i & (1 << bit)) != 0;
if (bitIsSet)
{
result[i] |= Bitboards.SquareBitboards[offsets[bit]];
}
}
}
return(result);
}