On Friday, March 13, 2015 at 10:20:10 AM UTC-5, Pieter Barendrecht wrote: > > Overall, I'm a bit surprised that using more than 3 or 4 workers does not > decrease the running time. Any ideas? I'm using Julia 0.3.6 on a 64bit Arch > Linux system, Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz. >
At four workers, you now have a process occupying every physical core (assuming the scheduler is doing what we want), plus your main coordinating process which is also occuping one of those four cores but presumably not doing any simultaneous computation. Many workloads do not see significant acceleration from hyperthreading; if this is such a workload, adding more workers won't give you any more speedup, and as René mentions overhead can start to dominate. Patrick
