Author: Omid David
Date: 20:17:16 10/08/02
Go up one level in this thread
On October 08, 2002 at 20:09:52, Robert Hyatt wrote: >On October 08, 2002 at 19:22:44, Omid David wrote: > >>On October 08, 2002 at 14:37:39, Robert Hyatt wrote: >> >>>On October 08, 2002 at 14:29:02, Rex wrote: >>> >>>>I agree that dual or more processors are faster. My question is the effeciency >>>>of search may be decrease. The weight of a given move may be decreased when its >>>>way down the tree. The differences of move weight gets less efficiant when the >>>>tree search gets deeper and deeper. Calculating what would be the best move >>>>based on score may not be the best move at all. Figuring this calculation deep >>>>in the search tree is probably imposible until that particular move arrives 1 to >>>>2 moves deep. Then it may be too late. >>> >>> >>>By faster, I don't mean "faster NPS only". >>> >>>I mean that if it takes one 1ghz processor 3 minutes to search to depth X, then >>>the two >>>1ghz machine should take significantly less than 3 minutes to reach that same >>>depth X. >>> >>>For Crafty, the rough number is about 1.7. IE if it takes 3 minutes for one >>>cpu, then it will >>>take around 1.7 minutes to do the same search using two cpus. For Crafty, the >>>NPS will >>>be closer to 2x faster using two cpus, but the "search efficiency" you mentioned >>>drops >>>the overall performance gain down to 1.7X or so... (again, this is an _average_ >>>number, >>>for those that like to question it. Some positions speed up more than 2.0 times >>>faster, >>>other speed up significanly less than 2.0 times faster. The overall _average_ >>>seems to >>>hover around 1.7 for Crafty. YMMV on other programs or on different hardware.) >> >> >>And how will Crafty perform on say 8 processors? Is there any limit for number >>of processors, or the more the processors the better the performance of Crafty? > > >I have run it on 16, but I have been unable to test it enough to see what >happens to the >speedup= 1 + (N-1)*.7 formula. I'm pretty sure it won't hold true up at that >end of the >number of processors. It works fine for 1-4, and it seemed to work ok for an >8-cpu test >I ran, but non-intel-based hardware. I will answer this question one day. But >one thing >is for sure, I don't ever expect to see more = worse performance, although it is >possible >that more != better performance... Of course, I didn't mean "more processors = worse performance", but was interested in knowing how diminished can the benefits be (and if the benefit from an n+1 processor after certain n threshold, can be practically 0). Thank you for your reply.
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