Author: Robert Hyatt
Date: 18:43:30 06/18/00
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On June 18, 2000 at 16:45:26, J. Wesley Cleveland wrote: >On June 18, 2000 at 16:05:01, Robert Hyatt wrote: > >>On June 18, 2000 at 15:50:43, Gian-Carlo Pascutto wrote: >> >>> >>>Hi all >>> >>>In the discussion of the 'Scalable Search Test' thread with >>>Ed Schroeder I mentioned that MTD(n,f) has the nice property >>>of making a fail-high pretty constant over time. I.e. the >>>search does not blow up as it does in a normal PVS searcher. >>> >>>Unfortunately it seems that this does not help when moving >>>up a ply...it even seems that the results of the MTD'ers >>>are quite terrible. >>> >>>The following though occured to me, if MTD allows you to take >>>small steps in the score plane, what about using fractional >>>ply increments to take smaller steps in the depth plane? >>> >>>Many of the best programs have now switched to fractional extensions. >>>Thus, fractional search depth must make sense. >>> >>>Iterative deepening is one of the most important improvements to AB >>>search. Thus, it makes sense too. >>> >>>Still, the programs use whole ply's in their iterative deepening >>>search. Why? It would make perfect sense to step in smaller increments >>>too. I feel this can even give improvements in tactical situations, >>>where the fractional extensions are triggered. >>> >>>I'm interested if someone has ever done or tested this before. Did it >>>work? What were the results? >>> >>>If you happen to have a program which uses fractional extensions, please >>>try it, and let us know how it works out. >>> >>>-- >>>GCP >> >> >>I tried this a good while back, but never really liked what I was getting. It >>is certainly worth trying... if you use fractional extensions. If you don't, >>it won't do a thing. > >I had an idea about this. If you kept track of how many extensions you did in >the search, if you had an unusually high number of extensions the iteration >before, you could search the next iteration to a lesser depth, e.g. >next_depth = last_depth + k*(nodes/(nodes+extensions)) >where k is equal to or somewhat greater than 1. Now your task is to test that. Sounds at least worth some testing. :)
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