On Dec 7, 2012, at 5:25 PM, Lee Spector wrote: > > Another strange observation is that we can run multiple instances of the test > on the same machine and (up to some limit, presumably) they don't seem to > slow each other down, even though just one instance of the test appears to be > maxing out all of the CPU according to "top". I suppose that means that "top" > isn't telling me what I thought -- my colleague says it can mean that > something is blocked in some way with a full instruction queue. But I'm not > interested in running multiple instances. I have single computations that > involve multiple expensive but independent subcomputations, and I want to > farm those subcomputations out to multiple cores -- and get speedups as a > result. My subcomputations are so completely independent that I think I > should be able to get speedups approaching a factor of n for n cores, but > what I see is a factor of only about 2 on intel machines, and a bizarre > factor of about 1/2 on AMD machines.
Lee: When you say "we can run multiple instances of the test on the same machine", do you mean that, for example, on an 8 core machine you run 8 different JVMs in parallel, each doing a single-threaded 'map' in your Clojure code and not a 'pmap'? And what kinds of speedups does that achieve? The results could help indicate whether the problem you are seeing is due to the hardware/OS, or something about multiple threads within a single JVM. Andy -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
