Author: Peter McKenzie
Date: 23:42:00 03/08/03
Go up one level in this thread
On March 09, 2003 at 01:14:12, Robert Hyatt wrote: >On March 09, 2003 at 00:35:49, Uri Blass wrote: > >>On March 08, 2003 at 23:34:35, Robert Hyatt wrote: >> >>>On March 08, 2003 at 12:05:59, Russell Reagan wrote: >>> >>>>On March 08, 2003 at 09:41:18, Robert Hyatt wrote: >>>> >>>>>Sure you can. You can evaluate all the pawn-only stuff, and then you can >>>>>pre-cmpute whatever you need such as passed pawn locations, weak pawn locations, >>>>>weak square locations, open file locations, half-open-file locations, and so >>>>>forth. You stuff that in the pawn hash table, and then use it when you evaluate >>>>>pieces to get the "coordination". >>>> >>>>I wonder if it would be faster (or reasonable) to keep track of this stuff >>>>incrementally. For example, from the starting position, you know that if a pawn >>>>makes a capture, or is captured, then that file is half open. So you can keep >>>>track of how many captures have been made to or from a file, and keep track of >>>>isolated pawns that way. I guess using a pawn hash would still be faster or more >>>>generally useful, and as with all things incrementally updated, you do some >>>>wasted updating computations where you may not use it. >>> >>> >>>This is a tough thing to figure out. IE incremental updates cost something. >>>You hope it costs less than computing from scratch, which it generally does if >>>done well. But if you start to search pretty deeply, then the payoff drops >>>off quickly, as you keep re-updating the incremental stuff multiple times >>>before you use it once when you reach the tips. >> >>1)It is the case only if you do not evaluate every node and there are programs >>that do it >>Rebel does it and movei also does it. >> >>Rebel does not do incremental evaluation but the reason is not that it is >>impossible to do it but the fact that Ed found it difficult to do it without >>bugs. >> >>2)The original question was about comparing incremental updating to pawn hash >>tables. >>I assume that for pawn structure, hash tables are faster because you may get >>almost 100% hits. >> >>Uri > >Yep. Even with a hash size of _one_, you can get decent results, because Thats something I'd never considered before but its a pretty cool observation! On the general question of pawn hash tables, I'm with you Bob. Very useful, very cheap, very fast, a rare combination in computer chess! >the same pawn structure happens in successive positions many times.
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