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Subject: Re: Move Generator

Author: Sune Fischer

Date: 07:17:01 12/20/02

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On December 19, 2002 at 23:18:55, Miguel A. Ballicora wrote:

>When I started, my first idea was to make a pgn cruncher. So, I figured that
>a legal move generator could be more useful (as Peter Fendrich points out
>in another message). As an engine, first unreleased versions of Gaviota had a
>legal generator. It was cool, detected all sort of pins statically using
>bitboards, but later I realized that the program was faster when I turned into a
>pseudo-legal generator.
>A legal move generator gives the advantage of knowing _exactly_ how many moves
>you can make, if you use that information (Uri does, I don't) it could be
>useful, otherwise, I think a pseudo legal should be simpler, tighter, faster and
>less prone to bugs. IMHO.

I hold the same opinion.

>I use a legal move generator only when I am in check. I think it is useful there
>and the slow down is negligible.

Actually it shouldn't slow you down, if it does I bet you are one of those that
adds illegal nodes to their node count :)
I think that is a bad idea, because illegal moves is a search overhead and
higher nodes per sec is a good thing, counting illegal nodes is simply wrong as
it gives you the impression a large search overhead is a good thing.

Doing check evasions is relative slow, but it is should still be faster than
making and unmaking illegal moves.
I do see a small speedup in kNps when doing check evasions.

-S.

>Regards,
>Miguel
>
>
>>
>>pseudo legal move generator is the easy way but I do not think that it is better
>>and the fact that chest is the best mate solver suggest that legal move
>>generator may be better.
>>
>>Uri



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