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Subject: Re: How important is a root search function ?

Author: scott farrell

Date: 01:19:25 09/02/03

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On September 01, 2003 at 18:53:48, Geoff wrote:

>Hi
>
>I have been improving my chess program so far by concentrating on speeding up
>the search. I have got this reasonably fast now in terms of nodes per second,
>but the program is still searching far too many nodes to get down to a
>particular depth.
>
>I noticed that quite a few other programs have a separate search root function,
>with a specific root move ordering function, I haven't bothered doing this so
>far as I couldn't really see how it would give that good an improvement ?  Is it
>really worth doing?
>

it makes only a small difference, it only helps really when you do aspiration
window, and get a fail low.

You need to work on move ordering in your search in general. Get some stats
working on finding fail-high. You need to implement killer-moves - it helps move
ordering heaps. Just one note on move ordering, as it gets better, your NPS
should drop dramatically, because you are searching less nodes when you get a
fail high on the first move, but you should get better time-to-depth, and
smaller trees.

>For info, my program currently uses fairly standard PVS search routine, alpha
>beta with aspiration window, history array ordering, null move R=2, TT table.
>
>Any other techniques I should be looking at next to get the nodes search down
>another notch ? Thanks
>
>                    Geoff



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