Author: Gerd Isenberg
Date: 12:23:09 01/28/02
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BITBOARD RookAttacksForward(BOARD &occupied, char square)
{
BITBOARD a,x,y;
x=occupied>>square; // shift board so square ends in lower left corner
y=x&RANK1; // mask out ewerything but the first rank
a=y^(y-2); // get the attacked bits on this rank
y=x&FILE1; // now mask so we get a clean first file
y=y^(y-2); // get the attacked squares
a=a|(y&FILE1); // add the attacked bits after masking with the file again
a=a<<square; // shift the attacked bits back (for ease of readability)
return a;
}
Thanks, very interesting. I can imagine, that this is faster than a table lookup
with the risc of cache miss, specially when you do it with assembler with mmx
registers (or waiting for hammer and 64bit compiler). Impressed about the
y^(y-2) operation, to get the attacked squares. I have to study it a while.
Gerd
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