Author: Jeremiah Penery
Date: 15:22:25 09/02/03
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On September 02, 2003 at 11:06:18, Robert Hyatt wrote: >On September 02, 2003 at 00:02:34, Jeremiah Penery wrote: > >>On September 01, 2003 at 23:39:13, Robert Hyatt wrote: >> >>>On August 29, 2003 at 18:32:46, Jeremiah Penery wrote: >>> >>>>Of course you can do a lot better - all I'm saying is that there's no way you're >>>>going to be doing worse. >>> >>>I don't remember saying I would be doing worse. I remember saying I would >>>be doing _bad_. Because potentially all memory references would be non-local. >> >>If you'd be doing "_bad_" in that case, how would you say you're doing now with >>SMP, where _every_ access is *slower than worst case* on that Opteron machine? > > >Somehow we are experiencing "a failure to communicate" (cool hand luke quote). > >My first port to the Cray resulted in a program that ran at 1K nodes per >second in 1981. The previous machine was doing about 100 nodes per second, >so that was a gain. On that same machine, 5-6 years later we were doing >20K nodes per second. > >I'd call 1K _BAD_. > >Even though it was faster than we had gone previously. That's a much different situation, because you moved to a completely different architecture with much more possibility. You're not going to see a 20x speedup on Opteron for Crafty just by optimizing some memory accesses. You'd be lucky to get 20%, IMO. If I somehow knew that a 4x Opteron 2GHz machine could get 20M NPS in Crafty, and you were getting only 3M, I'd agree that it was bad. But that is very far from the actual case.
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