Author: Robert Hyatt
Date: 14:17:49 01/10/03
Go up one level in this thread
On January 10, 2003 at 15:30:20, Bruce Moreland wrote:
>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
>
>What percentage of its time does Crafty spend in the popcount() function if the
>C version is used?
>
>bruce
I haven't tested in a while. Last time I did it was something like a couple of
percent...
Not very significant, overall...
However I did some optimizations that eliminate some of the PopCnt usage by pre-
computing popcounts for the mobility stuff, for example...
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