Author: Gian-Carlo Pascutto
Date: 14:57:47 09/15/00
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On September 15, 2000 at 17:13:57, Dann Corbit wrote: >Sorry. Only 24 coming. This is only solved to 15 ply. Checkmate or not, you >must complete the ply to claim the "prize". >;-) Quote: Here are a set of tough positions to search deeply. Just finding a mate is not good enough, uless you can *prove* it is the shortest mate. >1.f6+ Kh8 2.Qh6 axb2+ 3.Kb1 Ne6 4.dxe6 Qxa2+ 5.Nxa2 Rg8 6.hxg6 > +- (#9) depth: 15/21 00:00:18 436kN If you want a _proof_ I guess CHEST is the only option. Now, before you start writing those poems realize that this analysis is done by a Solution-Tree-Cost search and *not* by an alpha-beta searcher. The ply depths listed are totally uncomparable to alpha-beta ply depths. If you think this is cheating, consider that that measuring ply depth, via any algorithm at all, is a bogus measure. The only thing that might qualify is a fixed-depth, not pruned except by alpha-beta, search. Those won't reach 16 ply within the next few years I guess ;) Every more or less standard chessprogram uses some kind of extensions or pruning, which make the ply depth figure _meaningless_. As meaningless as NPS is as an indicator of program strength. Even worse, there exist very good algorithms that don't have any notion of ply depth at all. Besides, the basic task you gave us was very badly worded too: SOLVE these positions. A real solution would only consist of one thing: 1, 0, or -1. Now, ironically, the one solution you didn't accept was the only one I was able to solve... (to a 1) Instead you ask for a value (centipawn evaluation) that is also meaningless. Centipawn = 1/100 of a pawn ? But the value of a pawn is NO constant! The only thing that matters is whether the position is WON or LOST (or drawn). I hope you now realize that this challenge was flawed, and that there is no use to holding ply-depth DSW's. PS. My own program Sjeng reached over 12 ply in 30mins on 5 of those positions on my Cyrix120, so it's likely that a fast PentiumII can solve them. Also, the matefinder was on to something in at least one other position (not the mate above though!). I will try to get a full 16 ply search tomorrow. But again I ask you to realize that '16 ply' is meaningless. The only reason why Sjeng is able to get to those depths faster than e.g. Crafty (on the positions I tested this was the case) is that Sjeng is very light on extensions, but heavy on pruning. A 16 ply Crafty search is totally uncomparable to a 16 ply Sjeng search. You can replace Crafty and Sjeng by any random chessprogram in that last sentence. -- GCP
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