Author: Oliver Roese
Date: 23:17:48 06/18/00
Go up one level in this thread
On June 18, 2000 at 21:43:30, Robert Hyatt wrote: >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. > >:) Could you shortly give an idea, why this approach could be beneficial?! Lots of extensions indicate lots of stuff happening. Searching is designed to overcome tactical barriers. Why then _reduce_ the search depth? Thank you Oliver Roese
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