Author: J. Wesley Cleveland
Date: 13:45:26 06/18/00
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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.
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