Author: Uri Blass
Date: 23:52:12 10/12/02
Go up one level in this thread
On October 12, 2002 at 22:42:28, Robert Hyatt wrote: >On October 12, 2002 at 10:33:29, Omid David wrote: > >>On October 12, 2002 at 09:53:42, Robert Hyatt wrote: >> >>>On October 12, 2002 at 08:29:24, Omid David wrote: >>> >>>>On October 11, 2002 at 21:57:34, Robert Hyatt wrote: >>>> >>>>>On October 11, 2002 at 17:51:27, Omid David wrote: >>>>> >>>>>>On October 11, 2002 at 11:51:13, Robert Hyatt wrote: >>>>>> >>>>>>>On October 11, 2002 at 07:43:40, Uri Blass wrote: >>>>>>> >>>>>>>>On October 11, 2002 at 07:12:34, Vincent Diepeveen wrote: >>>>>>>> >>>>>>>>>On October 11, 2002 at 04:08:49, Uri Blass wrote: >>>>>>>>> >>>>>>>>>Isn't his article clear enough yet? >>>>>>>> >>>>>>>>Bob Hyatt still claims that it was 12 plies software and 6 plies hardware >>>>>>>>so I prefer to hear an answer directly from Hsu. >>>>>>> >>>>>>>I agree. But _I_ don't claiam _anything_ except that members of the DB team >>>>>>>specifically told me that 12(6) means 12 plies in hardware, 6 in software. I >>>>>>>even posted the excerpt from the email that specifically said this... >>>>>>> >>>>>>>That is _all_ I have said about it... >>>>>>> >>>>>> >>>>>>No matter what they say, even under extreme theoretical conditions it is >>>>>>*impossible* to search 18 plies of brute force in chess, without any type of >>>>>>forward pruning whatsoever, and no hash tables. >>>>> >>>>> >>>>>However, they have _never_ said they didn't use forward pruning. They have only >>>>>said "we don't use null-move for forward pruning" and nothing else. And they >>>>>have >>>>>slowly leaked details. But they pretty much had to since I had gone over their >>>>>log >>>>>files and discovered that theyt had a _very_ good branching factor, too good for >>>>>pure >>>>>alpha/beta alone... >>>>> >>>> >>>>Interesting... What was the average branching factor based on the logs you >>>>reviewed? >>>> >>>> >>> >>> >>>I don't remember the _exact_ number although I posted it here in CCC and several >>>were involved >>>in a long discussion about it.. but the number was something less than 4.0 I >>>believe, which is >>>_way_ below what a pure alpha/beta program can produce. >>> >>> >> >>I can't imagine a way for brute force alpha-beta to come up with a branching >>factor of anything even close to that number (esp. without hash tables). With >>regard to the branching factor, it seems that some kind of forward pruning was >>indeed in place... >> > >Remember, Deep Blue _did_ have hash tables. Only the last few plies (done in >hardware) >didn't have hashing. The first N plies hashed just like the rest of us... > >And you are right, of course. There are details they have not completely >revealed about >whatever forward pruning they did to reach that BF... I understood that they were afraid of pruning based on Hsu's paper. Hsu considered the depth of Deeper blue in the games against kasparov as 12 and said that they sacrificed 2 plies to implement their selective search algorithms. If they really did 18 plies in the match against kasparov(if 12(6) means 18) then I see no reason not to make it clear in a public article. Possible reasons not to say it can be: 1)if the last 6 plies are something like qsearch and not something similiar to what programs consider as plies. 2)The 6 plies are not additional plies to the 12 plies and they have another meaning. All their extensions(of singular and even in cases of 2 moves that are good should make it harder to search 18 plies). The logfiles also suggest that they clearly did not use hash tables in an effective way and the proof is the fact that the depth is not significantly bigger in endgames. Uri
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