Author: Anthony Cozzie
Date: 16:51:24 04/06/05
Go up one level in this thread
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
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