Author: Uri Blass
Date: 11:06:15 01/20/03
I find in crafty 2 functions for firstone
The first function is something has some function cntlzw that I am unable to
understand.
int FirstOne(register BITBOARD a) {
register unsigned long i;
if (i = a >> 32)
return(__cntlzw(i));
if (i = (unsigned int) a)
return(__cntlzw(i) + 32);
return(64);
}
I can understand only the second one.
int FirstOne(BITBOARD arg1) {
if (arg1>>48)
return (first_ones[arg1>>48]);
if ((arg1>>32)&65535)
return (first_ones[(arg1>>32)&65535]+16);
if ((arg1>>16)&65535)
return (first_ones[(arg1>>16)&65535]+32);
return (first_ones[arg1&65535]+48);
}
I also want to know if there is a faster algorithm to find all 1's if I do not
care about the order when in most cases there is a small number of 1's.
1 should be only for isolated pawn.
I want to use firstone to evaluate weak pawns not based on their number and I
need to find the weak pawns in order to evaluate them.
Uri
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