Author: Robert Hyatt
Date: 22:14:12 03/08/03
Go up one level in this thread
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 the same pawn structure happens in successive positions many times.
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