Author: Robert Hyatt
Date: 10:53:18 09/04/02
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On September 04, 2002 at 13:27:13, Vincent Diepeveen wrote: >On September 04, 2002 at 12:43:37, Robert Hyatt wrote: > >In short your new statement here says you used a >cpu time instead of wallclock time? No it didn't. And I am about ready to give up. The speedups are computed from wallclock time _only_. The times used to produce them were wall-clock. The only instance of cpu time was a bad reference. As I said, very _clearly_ each cpu very carefully kept up with the amount of time it spent searching, and the amount of time it spent "spinning waiting on work or locks." That was _also_ wall-clock time as that is all we used. CPU time on the cray was a problem in that all the threads got their times added together which made it not so useful, other that to compute a cpu% number we used as a warning. When it dropped below (say) 1550% we knew someone else had snuck in and was using our machine. this happened several times during the career of Cray Blitz. But _no_ cpu time in any of those three tables. Can I be more specific than that? > >If you reserve N cpu's at a supercomputer, you get N cpu's >at a supercomputer; this was not the case in your research, >so if i inform at the organisation whether they gave you >not n cpu's to do n cpu's test i get the answer: "he just >had to run at it and had to be lucky when he got cpu time, >but his processes were not killed". What are you talking about? When I ran the 16 cpu game, I was using a 16 cpu C90 with no other users whatsoever. When I ran the 2,4 and 8 cpu tests, I used an 8 cpu C90 with no other users. When I ran the one cpu test, then I ran with others, but I had one cpu guaranteed to me because I ran at a real-time priority and no one else could. So I don't know what you are talking about above... Certainly not about anything I did... > >That is the answer i get from the sponsor? No idea. I can't read minds or predict the future. but it has nothing to do with the testing I did.. so it really doesn't matter to me at all. Why don't you just tell your sponsor you are getting a 17X speedup on 16 cpus and get it over with? That seems to be _the_ issue here. Not truth. Not accuracy... so just go for it and have fun.
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