Author: Robert Hyatt
Date: 07:40:58 10/31/98
Go up one level in this thread
On October 30, 1998 at 14:43:19, José de Jesús García Ruvalcaba wrote: >On October 29, 1998 at 21:58:24, Robert Hyatt wrote: > >>On October 29, 1998 at 18:27:10, Terry Presgrove wrote: >> >>>Bob,Ed programers everywhere....just awe struck by the lastest >>>super computer just unveiled by V.P. Gore. At 3.9 Trilion calculations >>>per second just how strong would Crafty , Rebel, any of the comercialy >>>available programs be? Unless I misunderstood its Over 15,000 times faster >>>the the fastest PC's currrently available. More than 5,800 >>>processors....wouldn't it be nice to play around with this baby for just a day? >> >> >>first warning is a large number of processors... ie it isn't a shared memory >>machine, which means that it is not easy or efficient to distribute the search >>on such machines. If you have seen crafty on a 4 processor machine, and expect >>that to scale so such a machine, you'll be disappointed... >> >>However Sequent makes a 32 processor xeon-based machine that features a >>shared memory. *that* would scream... IE a NPS of something around 10M >>would be easy... > >What would be the expected performance of craty on a 64-processor Sun Enterprise >10000? >As far as I understand, it has symmetric multiprocessing. Assuming no "bottlenecks" it should be roughly .7*64 times faster. However, I wouldn't be certain that the .7 holds... IE I have a single lock for each of the two hash tables. With 64 cpus, that is likely going to produce some blocking conditions. I carefully only lock while I read an entry then unlock, but it is possible that this will start to add up. Not having a 64 processor machine to work on, I can only speculate. In Cray Blitz, with 32 processors, I didn't see significant blocking... but there I did everything in assembly and the lock/load/unlock and lock/store/unlock for hashing was *very* quick. Also I don't know how sun has done their 64 processor architecture. A non- blocking crossbar is very expensive for 64 processors. Also, what about memory? Cray uses a bunch of memory banks (things that can do 2 reads and 1 write at the same time) to avoid processor stalls. What does Sun do? If the memory bandwidth isn't there, then the .7 is going to shrink...
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