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Subject: Re: questions about dynamically updating attackboards

Author: Andrew Williams

Date: 14:32:06 08/23/03

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On August 23, 2003 at 17:19:20, Sune Fischer wrote:

>On August 23, 2003 at 16:24:28, Andrew Williams wrote:
>
>I know this scheme very well, perhaps we should compare nps ;)
>

PM does about 170knps.

>Do you also xor out the changes?
>
>One problem I see with this, is that 32 bits is too big to make use of SEE by
>table lookups.
>

Yes. It's nowhere near as nice Ed's scheme.

>Another problem is the number of squares that needs updating in the endgame with
>sliding pieces, it's just enourmous.
>

Yes.

>>2. Go over all 64 squares, masking out the attacks identified in (1) above.
>
>You don't need all 64 squares, just the changes.
>

Yes. This is one of those things I keep "in hand" for when I run out of new
things to try.

>>3. Go through all the pieces that were affected (not the captured piece of
>>course) and generate their attacks and mask them into the 64-uint array.
>
>Hmm, you have to cleanup this piece also I think.
>

Yes. This could be done better too.

I definitely wouldn't claim that PM's approach is optimal. It just works. If I
ever get really concerned about it, I can eliminate some of the unecessary work.
I don't think it's critical to do it at the moment.

Andrew




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