Author: Frank Phillips
Date: 13:42:55 01/10/03
Go up one level in this thread
On January 10, 2003 at 15:16:52, Uri Blass wrote:
>1)How do I use assembler code under C to count the number of 1's in a bitboard?
>I do not know how to copy assembler code from crafty.
>
>I understood from previous post that the relevant code is in crafty but I do not
>know how to copy it correctly with all the #defines in crafty.
>
>I understood that there are some relevant codes(x86.s, vcline.h that I could not
>find and boolean.h
>
>2)I tried a code of dieter and got warning from the compiler(see the bottom of
>this post for that code)
>
>warning C4244: '=' : conversion from 'unsigned __int64 ' to 'unsigned long ',
>possible loss of data
>
>Note that I changed
>int PopCount(unsigned long long a)
>to
>int PopCount(BitBoard a)
>
>I also have in my code
>typedef unsigned __int64 BitBoard;
>
>I also never use the word long in my program except the code that I copied from
>Dieter and I use int for 32 bit numbers.
>
>The warning was about w=
>
>int PopCount(BitBoard a)
>{
> unsigned long w;
> int n = 0;
> w = a&0xffffffffUL;
> if (w)
> do
> {
> n++;
> }
> while ((w &= w-1) != 0);
> w = (a>>32)&0xffffffffUL;
> if (w)
> do
> {
> n++;
> }
> while ((w &= w-1) != 0);
> return n;
>}
>
>Uri
If you are using an Athlon, then you might wish to compare the speed of your
program using the non assembler and assembler versions of FirstBit, LastBit and
PopCount, just to check which is faster.
As Bruce already hinted, you might also do a profile to check how significant
PopCount is to overall speed.
Frank
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.