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Subject: Re: Differences between 0x88 ,10x12 and Bitboards!?

Author: Gerd Isenberg

Date: 11:01:19 11/19/02

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On November 19, 2002 at 13:30:57, Christophe Theron wrote:

>On November 19, 2002 at 13:15:09, Gerd Isenberg wrote:
>
>>On November 19, 2002 at 12:25:11, Gian-Carlo Pascutto wrote:
>>
>>>On November 19, 2002 at 11:35:24, Robert Hyatt wrote:
>>>
>>>>Bitboards have a bit of a performance advantage on 64 bit processors,
>>>
>>>Proof?
>>>
>>>--
>>>GCP
>>
>>Hi Gian-Carlo,
>>
>>I think that's evident. If the none bitboarders have to use implicite native
>>data-width of 64 bit integers, they have to transfer 32 additional zero bits
>>without any additional information for each integer access. Of course you will
>>pack some data, but all the local ints...
>>
>>So the information density for bitboarders grows with 64bit-architectures
>>relative to none bitboarders. That also effects register usage, and that's IMHO
>>more important. On x86-32bit architectures you can only hold three bitboards in
>>registers, and thats even most a hard task. Actually, if you have a local
>>routine with three bitboards and a few ints on the stack, there are a lot
>>register/memory moves. Simply the data-width doubles the number of bitboard
>>registers, not considered the increase in general purpose registers, or with
>>hammer the number of mmx- and 128-bit xmm registers.
>>
>>Whether a bitboard based program is stronger than a none bitboard program
>>depends obviuosly also on other things, but in principle :)
>>
>>Cheers,
>>Gerd
>
>
>
>You have just explained why the bitboarders are less handicapped on 64 bits
>machines.

Hi Christophe, Yes.

>
>You have not explained why they are supposed to have "a bit of performance
>advantage on 64 bits processors".
>

Ok, because they are less handicapped on 64 bit machines :-)

Since Steffan Westcott teached me Flood-Fill- and Kogge-Stone algorithms here in
CCC, and i tried my first mmx-implemetation without rotated bitboards, i believe
that this attack/move generation routines are absolutely great for 64-bit
processors with a lot of registers.

I found bitboards the most natural data structure to define chess related
patterns - and i like it. May be a individual matter of taste.

Cheers,
Gerd


>
>
>    Christophe



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