Author: John Merlino
Date: 17:15:52 04/06/05
Go up one level in this thread
On April 06, 2005 at 19:51:24, Anthony Cozzie wrote: >On April 06, 2005 at 19:31:27, Walter Faxon wrote: > >>In a recent thread (http://www.talkchess.com/forums/1/message.html?419679), the >>problem of on-line lookup of 6-man endgame tablebases was discussed. The >>consensus was that for computer play, you could (maybe) load blocks of related >>positions from near the root, not make individual requests for the value of >>specific positions, since even fast net access is a snail compared to a good >>hard disk. >> >>Either way, it takes a good block of time. To a much lesser degree, even >>looking up the hash value for the current position can lose if its cache line >>isn't already loaded. Main memory lookup can require hundreds of processor >>cycles on modern hardware. (Probably a reason why Hyper-Threading(R) technology >>works so well for computer chess. When one thread stalls the other might be >>able to continue.) >> >>In between is the standard situation where a particular position in the tree has >>multi-depth subsearches returning with widely varying scores and suggested >>moves. You've reached a "hard" position. Or maybe before you've done any >>searching on a position, you've somehow statically determined that it is "hard" >>(like it will require a disk lookup). Either way, what should you do? >> >>My question is: Is it ever reasonable to just say "I'm going to leave the >>evaluation of this position until later, if necessary." And continue the >>search. It is possible and in many cases likely that the remaining search will >>cut off at least some of the hard positions, and you will discover that you >>never really needed to evaluate these in the first place. Maybe the search tree >>could be marked so that when the "easy" search has been completed you can then >>return to try to understand the remaining hard positions, in an order of how >>they affect the remaining tree. >> >>Has anybody written code that addresses this? >> >>-- Walter > >Move ordering is very interesting, because you don't really want to search the >best move first, you want to search the move that will provide a cutoff with the >least amount of work. Unfortunately, this seems like a really hard problem . . >. > >anthony The King always searches the best move from the previous depth first. Why would you NOT want to do that? Wouldn't your biggest priority when reaching a new depth be verifying what you have accomplished on the previous depth -- especially if time is a consideration (and it usually is)? jm
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