Author: Robert Hyatt
Date: 19:42:28 10/12/02
Go up one level in this thread
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... > > > >> >> >>> >>>> >>>> >>>>> >>>>> >>>>> >>>>>> >>>>>> >>>>>> >>>>>>> >>>>>>>> >>>>>>>>reporting a 12.2 average search depth fullwidth. >>>>>>>>I guess you never searched with a decent program fullwidth >>>>>>>>with extensions. If you did, you would understand that >>>>>>>>getting 12.2 ply fullwidth with loads of extensions is already nearly >>>>>>>>impossible. Every extended line is searched to the full depth, >>>>>>>>no pruning happens! >>>>>>> >>>>>>>I agree that 12.2 plies with a lot of extensions and no pruning is impossible >>>>>>>for normal programs and also is impossible for deep blue in case that >>>>>>>there were real 6 more plies in the hardware. >>>>>>> >>>>>>>The only case when it may be possible is if the 6 more plies in the hardware are >>>>>>>real selective search and it means more pruning than null move with R=3 and in >>>>>>>this case the 6 plies in the hardware may be eqvivalent to only 2 plies in >>>>>>>software because of big probability to miss things. >>>>>>> >>>>>>>> >>>>>>>>The interesting 2 questions are >>>>>>>> a) did DB use 'no-progress pruning' in SOFTWARE (we know >>>>>>>> already it used it in hardware). >>>>>>> >>>>>>>They explained in the article that they did not want to take risks of missing >>>>>>>something in the first plies so it is clear that they did no pruning in the >>>>>>>first 12 plies. >>>>>>> >>>>>>>If they did some pruning in the software it is clearly after it. >>>>>>> >>>>>>>I do not know what is exactly no progress pruning. >>>>>>>Is there a difference between it and null move pruning? >>>>>>> >>>>>>>Is no progress pruning more aggresive than null move pruning? >>>>>>> >>>>>>>Uri
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