Author: Gerd Isenberg
Date: 10:34:56 03/03/06
Go up one level in this thread
>I can confirm your findings. There are a few points however.
>
>I couldn't get your values to work, in a few cases the magic number seemed to
>map different bitboards to the same index.
Back home i double checked it and found no error so far, i also report the
number of possible states (1,2,4,8,16,32,64) - all unique indices.
Do we have the same square mapping?
>
>I then run the deBruijn generator myself, to get stuck on 40 values or so, for
>wich it couldn't get a magic number.
Ok, i told something from modified De Bruijns, but i didn't post the exact way i
modify them. You are right - the pure De Bruijns are not sufficent for all rays.
Here some more code snippets i use,
32-bit release run takes 13 minutes on my box:
void DBG::deBruijnFound(BitBoard deBruijn) const
{
BitBoard ray;
for (int x = 0; x < 11; x++) {
for (int sq=0; sq < 64; sq++) {
for (int dir=0; dir < 4; dir++) {
if (notAllreadyFound(sq, dir) {
int count = checkMagicNumber(deBruijn, sq, dir, ray);
if ( count >= 0 ) {
// store and report found magic
}
}
}
} // sq
dB -= 0x0005012000030104; // some "random" const
} // x
}
// return: number of found states
// or -1 if failed
int checkMagicNumber(BitBoard deBruijn, int sq, int dir, BitBoard &d)
{
static BitBoard notBoarder[4] = {
0x007e7e7e7e7e7e00, // noEast-soWest
0x007e7e7e7e7e7e00, // soEast-noWest
0x00ffffffffffff00, // _north-_south
0x7e7e7e7e7e7e7e7e // _east_-_west_
};
static BitBoard one = 1;
int count = 0;
BitBoard t = 0;
d = attackGetter[dir](one<<sq) & notBoarder[dir];
clearLocks();
do {
unsigned int idx = (unsigned int)((t * dB) >> (64 - 6));
if ( locked(idx) ) return -1;
lock (idx);
count++;
t = (t-d) & d;
} while (t);
assert ( count == (1 << popCount(d)) );
return count;
}
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