Author: Uri Blass
Date: 00:59:26 09/16/00
Go up one level in this thread
On September 15, 2000 at 21:04:53, Dann Corbit wrote: >On September 15, 2000 at 17:57:47, Gian-Carlo Pascutto wrote: > >>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. > >So! I've been bamboozled. I think that pruning that leads to the same >solutions is valid. Every sort of pruning will throw away some correct >solutions. But NULL move is only very rarely going to lead to problems. I believe that recursive null move may often lead to problems. My guess is that if you compare Crafty's result after 10 plies without null move pruning and with null move pruning you will find at least 10% different moves(I think it will be interesting to do this experiment) Take some games of Crafty tell it to search all position to 10 plies without null move pruning and with null move pruning and see the number of different moves in 1 ply,2 plies....10 plies. Another interesting experiment will be to play fixed depth matches(x plies of the regular Crafty against x-1 plies without pruning) I am not sure which side is going to win and my guess is that when x is big enough x-1 is going to win. I do not say that recursive null move is counter productive but there is a significant price that you pay for searching deeper. The price is smaller than the advantage and this is the reason that programmers use null move. Uri
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