Author: leonid
Date: 11:02:24 01/13/01
Go up one level in this thread
On January 12, 2001 at 03:20:26, David Rasmussen wrote:
>My program Chezzz, and most of the programs I've been learning from and looking
>at, has only little or moderate selectivity. Maybe I will keep it that way in
>Chezzz, but what are the possibilities?
>
>As far as I know, there are two general kinds of selectivity as currently used
>in "normal" alpha-beta based chess programs.
>
>1. Extensions
>2. Forward pruning
>
>I would like to know what hints and tricks you guys have about extensions,
>unusual extensions, how to limit extensions, when not to extend etc.
>
>But most of all, I would like to know about successful (I know this is somewhat
>subjective) forward pruning techniques, that are actually used in programs.
>
>I compared my programs performance on the position below, with what Christophe
>Theron posted from GT. At depth 10 the nodes searched by each programs are appx.
>
>GT : 1.290.000
>Crafty : 13.500.000
>Chezzz : 12.500.000
But what is the number of positions (nodes) seen without selective search? This
could give some idea how far good program can be selective before putting itself
into danger to miss too many things.
Indicated selection sound to me as very prudent. I tried your position by
searching it with my program by brute force 10 plys deep. No extensions were
used. If my numbers can be some indication, they are:
White goes. Nodes used. Nodes generated. Times all plys was accessed.
146.035.163 282.908.248 57.263.729
Black goes. 295.060.113 585.543.079 115.741.094
Thanks,
Leonid.
>
>So Crafty and Chezzz is the same, and they are both very conservative in regard
>to selectivity IMO. I know that this is a choice and that one way is not better
>than the other, but I would still like to know how programs such as GT can get
>such a low node count.
>
>Now I know that GT is highly optimized, and that it has probably taken a long
>time get as "efficent" as GT. But I would still like to know as much as possible
>or at least the basics about how to forward prune succesfully like this.
>
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