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Subject: Re: 0x88 compared to rot BB

Author: Rémi Coulom

Date: 02:47:51 01/14/03

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On January 13, 2003 at 13:16:33, Bruce Moreland wrote:

...
>
>Checking specifically for pawns is probably right.  Looking at two squares on
>the board is probably faster than spinning through 8 pawns.

I agree with you. I first suggested that testing for pawns first might not be a
good idea, but I had not noticed that the piece list was sorted. The question is
now: is it a good idea to keep the piece list sorted? I suppose it adds
complexity to the make/unmake functions. Bas says it helps MVV/MVA move
ordering, but I tend to believe that ordering moves based on MVV/LVA only is not
very good.

>
>I think that the problem here is that he has a loop in the first place, which is
>just an aspect of 0x88.

>
>I don't know how the bitboard "attacked" function works, but if it does less
>work, it's going to be faster.

I agree too. 0x88 might slower on attack detection, but the speed of
makemove/unmakemove compensates so that perft should be faster on a 0x88
implementation than with crafty.

>
>bruce

Also, my general advice to anobody starting to write a chess programs is that
spending huge amounts of time optimizing the low-level functions is probably not
an efficient way to obtain a good level of play. I suppose most top-level
programs could have their basic functions (make/unmake, genmoves, attacks) twice
slower without very significant losses in strength.

Rémi



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