Author: Bas Hamstra
Date: 19:08:50 01/12/01
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I don't know if it useful to compare nodes this way. My first PV at depth=10 comes in the order of nodes of GT, but then it switches 4 times, to end at a4 at 22M nodes. I might be that GT was lucky to not have those expensive PV switches. Bas. 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 > >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. > >[D]2r1k2r/5pp1/4p3/ppqpP3/4bQPP/1B6/PPP2R1R/2K5 b k - 0 1
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