Author: rasjid chan
Date: 22:22:53 04/06/04
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On April 06, 2004 at 17:01:12, Peter Fendrich wrote: >On April 06, 2004 at 16:34:27, Bo Persson wrote: > >>On April 06, 2004 at 11:12:50, Peter Fendrich wrote: >> >>> >>>Agree, but most interesting is how often. It must be much more often in MTD. >>>I just have presentiment of that the increased entry size wont pay off in PVS >>>with that much more cut offs. >>> >> >>But there is an additional value, besides the potential cutoffs. In the PV >>search, the bounds might also help you reduce your window by moving alpha, or >>beta, or both. Even if you don't get an immediate cutoff, you might get a pruned >>tree. >> >>I once tried this by mistake, while moving from PVS to MTD(f). I started by >>implementing the two bounds in my hash table, but forgot to add the modified >>root search. It still reduced the search tree significantly, maybe 20%. >> >> >>Bo Persson > >Fooling around with alpha/beta values is nasty business and would require >thorough testing, at least in my program! >Reduced tree size mustn't necessary be a good sign here... >/Peter feedback for your info - I have now completed implementing ETC and I think it is "well done" because it is not relatively tough. I don't test but use my eyes + log printout and it seems beneficial and no hint that it is a drag on performance, but seems to search slightly deeper... [sum of many slightlies] == better. Now I'm introduced to hashing[LB, UB]. ETC make use of bounds info and MAYBE 2 bounds better than one. There are 2 passes of looping thru the moves and we may have a cutoff in the 1st pass or, as alpha improves in the 2nd pass,more moves may be pruned. Added to the above, a raw guess is ETC + 2 bounds may be more beneficial to MTDf. The average probability that a node fails high is much higher in MTDf than in other algorithms... but PVS is also most of the time null window. Rasjid
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