Author: Omid David Tabibi
Date: 07:01:48 04/13/03
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On April 13, 2003 at 07:41:00, Vincent Diepeveen wrote: >On April 13, 2003 at 00:14:52, Omid David Tabibi wrote: > >may i remind you that many programs use R=3 basically with exception sometimes >of the nullmove of depthleft == 4. > >I'm doing more in qsearch than you do. > >Further your verification search is using R=3 too with a bug in the hashtables >management. Because of that bug which is that you do not store in hashtables >whether a search result is based upon a verification or not, the worst case >performance of verification search is R=3. One of the reviewers of the article asked several questions regarding the use of hash tables in conjunction with verified null-move pruning. I told him exactly what I told you, i.e., the depth stored in the hash table is the depth after reduction (e.g., if we were in depth 6, have a fail-high report and reduce the depth to 5, then the final stored depth in the hash table is 5). That might be too conservative a method, but it guarantees that no hash table bugs (of the form you mention) are encountered. However, I did not explicitly mention it in the article, as I preferred that it remain as an exercise to the reader (and the reviewer also agreed that it might be best to leave it to the reader to experiment). The method I used might be too conservative, and so other programmers might achieve even better results by using a more aggressive use of hash tables. > >Best regards, >Vincent > >>On April 12, 2003 at 22:45:19, Vincent Diepeveen wrote: >> >>>On April 12, 2003 at 13:20:51, Omid David Tabibi wrote: >>> >>>>On April 12, 2003 at 10:02:43, Uri Blass wrote: >>>> >>>>>On April 12, 2003 at 09:17:31, Omid David Tabibi wrote: >>>>> >>>>>>Quite an interesting read Vincent. >>>>>> >>>>>>I'm afraid you are investing too much in the parallel speedup though. Any >>>>>>hardware speedup will be linear (at best) while algorithmic enhancements are >>>>>>exponential. If you manage to search one ply deeper by an algorithmic >>>>>>improvement, the gain will be more than any parallel speedup can yield. >>>>> >>>>>I agree that the hardware speedup from parallel search will be linear at best >>>>>but linear improvement is not always less than one ply. >>>> >>>>Diep is already parallel. I assume that he will get far less than a 4x speedup >>>>for his latest work on massive parallelism. Assuming an effective branching >>>>factor of 4, that speedup will equal one ply. >>> >>>b.f. = 2.9 >> >>Because you are using standard R=3; but is the search reliable? That bf will not >>be of much use if it causes Diep to find the correct move two plies later in >>comparison to its competitors. When was the last time you compared Diep's >>performance to other engines using test suites? >> >>BTW, I can get even a smaller branching factor than yours in no time. I will >>just use standard R=6 :) >> >> >> >>> >>>> >>>> >>>>> >>>>>If the number of processors is big then it can be more than one ply. >>>>> >>>>>I believe that it is possible to get a lot more than one ply by pruning and >>>>>extensions but I decided that I prefer first to improve movei's evaluation and >>>>>only later to improve movei by better pruning and extensions because evaluation >>>>>is one of the things that is used in decisions about pruning and extensions. >>>>> >>>>>I believe that Movei's main problem in games with programs at similiar strength >>>>>is in the endgame so I will probably do some improvement in that stage before >>>>>going back to search. >>>>> >>>>>Uri
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