Author: Ricardo Gibert
Date: 14:44:03 05/30/05
Go up one level in this thread
On May 30, 2005 at 16:06:38, Robert Hyatt wrote: >On May 30, 2005 at 07:23:24, Ricardo Gibert wrote: > >>On May 30, 2005 at 06:21:14, Pallav Nawani wrote: >> >>>On May 30, 2005 at 02:02:49, Amir wrote: >>> >>>>Deep Blue could calculate 200 million moves per second. According to what I have >>>>read, Hydra calculates 40 million moves per second. How then is Hydra sees >>>>deeper or is faster than Deep Blue, as is claimed by the authors?? >>> >>>According to the logs that I saw, deep blue was searching 12 plies deep in the >>>K-DB match. My program can match that depth on a 1.1Ghz PC. This is because of >>>search techniques that were not used in deep blue. Eg: Null move, Rebel style >>>reductions, aggressive pruning. Hydra is obviously using such search techniques, >>>and given its higher processing power, it will easily outsearch Deep Blue. In >>>fact, in Shredder-Hydra match, shredder was searching to 16 ply (I think, but I >>>could be wrong) which was almost the same as Hydra (Again, not sure). >>> >>>Also, Deep Blue was using Singular Extensions, which increases the number of >>>nodes required in search. >> >>But which also reduces EBF. You should have left out this paragraph. > >No. In fact it increases it significantly. In Cray Blitz, it reduced our >average search depth about 2 plies. Which is a significant _increase_ in >effective branching factor. Most extentions result in a reporting of lower depth and an increase in nodes, but this usually still means a reduction in ebf, because the depth reported does not take into account the additional depth from the extentions. In short, the depth reported underrepresents effective depth. As for SE I don't much about it, but it must be a pretty crappy extention if it really increases EBF. > >> >>> >>>Also note that 9 plies of program 1 are not the same as 9 plies of program 2. >>>These programs may be using different search techniques/extensions etc, and >>>therefore on basis of plies searched you cannot guess the relative strength of >>>programs. For instance, singular extensions are reputed to increase tactical >>>strength quite a bit, but they may decrease the depth of search. >>> >>>Pallav >> >>I better though still imperfect comparison uses: >> >>effective_depth = log(nodes)/log(EBF) >> >>If given 2 programs where one reports a lower depth, because it does a lot of >>extentions and another that reports a higher depth, because it does a lot of >>pruning, but they otherwise generate the same search tree, then the above will >>return the same effective_depth. > > >log(EBF) is diluting the calculation. "nodes" is already included in EBF. ebf**depth = nodes log(ebf**depth) = log(nodes) depth*log(ebf) = log(nodes) depth = log(nodes)/log(ebf) where ** denotes exponentiation It's an approximation for comparison purposes only.
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