public void Init()
{
var rooks = new MagicBitboardGenerationEntry[64];
var bishops = new MagicBitboardGenerationEntry[64];
//var positions = Enumerable.Range(0, 64);
//Parallel.ForEach(positions, pos =>
//foreach (var pos in positions)
for (var pos = 0; pos < 64; pos++)
{
var rank = pos >> 3;
var file = pos & 7;
var diagonal = file + rank;
var antidiagonal = rank - file + 7;
Bitboard rookMask = BitboardConstants.Ranks[rank];
rookMask |= BitboardConstants.Files[file];
if (rank != 0)
{
rookMask &= ~BitboardConstants.Ranks[0];
}
if (rank != 7)
{
rookMask &= ~BitboardConstants.Ranks[7];
}
if (file != 0)
{
rookMask &= ~BitboardConstants.Files[0];
}
if (file != 7)
{
rookMask &= ~BitboardConstants.Files[7];
}
rookMask &= ~(1UL << pos);
var rookEntry = InitEntry(rookMask, false, pos);
rooks[pos] = rookEntry;
Bitboard bishopMask = BitboardConstants.Diagonals[diagonal];
bishopMask |= BitboardConstants.Antidiagonals[antidiagonal];
bishopMask &= ~BitboardConstants.Ranks[0];
bishopMask &= ~BitboardConstants.Ranks[7];
bishopMask &= ~BitboardConstants.Files[0];
bishopMask &= ~BitboardConstants.Files[7];
bishopMask &= ~(1UL << pos);
var bishopEntry = InitEntry(bishopMask, true, pos);
bishops[pos] = bishopEntry;
}//);
MagicBitboards.Rooks = rooks.Select(x => new MagicBitboardEntry(x.BlockerMask, x.MagicNumber, (byte)(64 - x.BitCount), x.Moveboards)).ToArray();
MagicBitboards.Bishops = bishops.Select(x => new MagicBitboardEntry(x.BlockerMask, x.MagicNumber, (byte)(64 - x.BitCount), x.Moveboards)).ToArray();
//PrintBitboardArray(rooks.Select(x => x.MagicNumber).ToList());
//PrintBitboardArray(bishops.Select(x => x.MagicNumber).ToList());
}
private MagicBitboardGenerationEntry InitEntry(Bitboard blockerMask, bool bishop, int pos)
{
var entry = new MagicBitboardGenerationEntry();
entry.Position = pos;
entry.BlockerMask = blockerMask;
entry.Bishop = bishop;
var maskCopy = blockerMask;
var bits = new List <int>();
while (maskCopy != 0)
{
var blockerPosition = maskCopy.BitScanForward();
bits.Add(blockerPosition);
maskCopy &= maskCopy - 1;
}
var permutations = 1 << bits.Count;
entry.BitCount = (byte)bits.Count;
entry.Occupancies = new Bitboard[permutations];
entry.Moveboards = new Bitboard[permutations];
for (var i = 0; i < permutations; i++)
{
Bitboard occMask = 0;
for (var j = 0; j < bits.Count; j++)
{
var shouldSet = (i & (1 << j)) > 0;
if (shouldSet)
{
var bit = bits[j];
occMask |= 1UL << bit;
}
}
entry.Occupancies[i] = occMask;
var moveboard = bishop ? _otherSlideGenerator.DiagonalAntidiagonalSlide(occMask, pos) : _otherSlideGenerator.HorizontalVerticalSlide(occMask, pos);
entry.Moveboards[i] = moveboard;
}
entry.MagicNumber = FindMagicNumber(entry);
return(entry);
}
private Bitboard FindMagicNumber(MagicBitboardGenerationEntry generationEntry)
{
const Bitboard invalid = ~0UL;
Bitboard magicNumber = 0UL;
var success = false;
ulong iterations = 0;
while (true)
{
var table = Enumerable.Repeat(invalid, 1 << generationEntry.BitCount).ToArray();
iterations++;
magicNumber = _candidateProvider.GetMagicNumberCandidate(generationEntry.Position, generationEntry.Bishop);
success = true;
for (var i = 0; i < generationEntry.Occupancies.Length; i++)
{
var occupancy = generationEntry.Occupancies[i];
var moveboard = generationEntry.Moveboards[i];
var multiplied = occupancy * magicNumber;
var magicIndex = multiplied >> (64 - generationEntry.BitCount);
var magicIndexInt = (int)magicIndex;
if (table[magicIndexInt] == invalid || table[magicIndexInt] == moveboard)
{
table[magicIndexInt] = moveboard;
}
else
{
success = false;
break;
}
}
if (success)
{
generationEntry.MagicNumber = magicNumber;
generationEntry.Moveboards = table;
break;
}
}
Console.WriteLine($"{(generationEntry.Bishop ? "Bishop" : "Rook")} at position {generationEntry.Position}: {iterations} iterations");
return(magicNumber);
}
