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Subject: Re: Way of compressing attacks bitboards

Author: Sune Fischer

Date: 13:59:57 05/06/04

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On May 06, 2004 at 16:07:16, Robert Hyatt wrote:

>On May 06, 2004 at 13:00:06, Mathieu Pagé wrote:
>
>>Hi,
>>
>> Actualy my engine use pre-calculated bitboards to generate the moves. and I was
>>asking myself if compressing them, in order to keep them in cache would make my
>>move generator faster. I tought about two techniques to compress them.
>>
>>1. Use a 7 bits mask as a representation of the occupancy of the line as we
>>always know that the position where the piece that we want to move is occupied.
>>I already use this and it cut the space used by the index by a factor of two.
>>I'm sure you were all aware of this trick.
>
>What about using a 5-bit mask then.  You don't need the two endpoint bits anyway
>as you attack those squares whether they are occupied or not.

What if the square is on the edge and thus already removed?
Seems you end up with some being 5 bit and some being 6 bit lines.

>I use 6 bit myself as squeezing out the square the piece is on is not
>convenient...

-S.



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