Author: Uri Blass
Date: 03:00:25 12/21/04
Go up one level in this thread
On December 21, 2004 at 05:27:36, Joachim Rang wrote: >On December 21, 2004 at 05:11:13, Uri Blass wrote: > >>On December 21, 2004 at 03:53:49, Joachim Rang wrote: >> >>>On December 20, 2004 at 16:32:24, Jouni Uski wrote: >>> >>>>Shredder 8 reaches quite stunning averaga search dept. E.g. with only 15 >>>>second/move average with Pentium 2400 and 128MB hash it averages 15,2 ply! For >>>>comparison Fritz Bilbao and Gandalf 6 reach both same 12,7 ply. No wonder >>>>Shredder beats them 13 - 7 and 14 - 6. Of course 2,5 ply is a lot difference! >>>>Is there any amateur or pro engine, which can equal Shredder in depth - Junior's >>>>half plys can be forgotten. >>>> >>>>Jouni >>> >>>Here is a 1-minute search on my Athlon XP@1540 MHz, with Shredder 7.04 default >>>and Fruit X with aggressive delta, futility and history pruning. Both engines >>>were analysing together under Arena. Compare the depth! >> >>I am surprised to read that fruit2 has history pruning. >>I understood that Fabien does not plan to implement history based pruning and >>here is the source of my misunderstanding: >> >> >>The reason is the following link: >>http://f11.parsimony.net/forum16635/messages/68164.htm >> >>Fabien claimed in that link: >> >>"Forward pruning in the main search is a separate topic that I don't intend to >>address now. If I ever do, I expect it will require years of work (same for a >>proper move ordering)." >> >>Note that I consider history based pruning as forward pruning in the main >>search. >> >>It did not take me years to implement it and I was surprised that Fabien claimed >>that it will require years of work and maybe there is a misunderstanding about >>the meaning of forward pruning. >> >>Uri > > >Well, most probably history pruning will not be included in Fruit 2.0 (which I >regret) since we could not test it thoroughly. Fabien introduced it in a >dev-version in November without any ambitions, but it seems promising, but in >fact it needs time to tune and test. Btw, how did you tune it or make sure it is >beneficial? One needs longer time controls so it is a lot of work. I am not sure if it is beneficial but I tend to believe that it is beneficial. I remember that at the time that it was beneficial in test suites at long time control in the time that I implemented it. The last time that I tested it in games history based pruning helped but I did not have enough games and result was something like 27-23 if I remember correctly. Things may be different today. There are 2 relevant parameters in movei that are about history based pruning. selectivity 7 limit_history_depth 101 By reducing selectivity movei does more pruning. limit_history_depth 101 means pruning when the remaining depth is lower than 101 and it means always prune. Maybe it is better to use history depth pruning only when the remaining depth is small enough (you can do it by reducing limit_history_depth) but I did not try it. I have logical reasons to believe that it may be better but I decided not to change something that I did not test. Uri
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