Ref https://github.com/JuliaLang/julia/issues/12611#issuecomment-130902406
Further discussion should probably continue there.
On Thu, Jul 30, 2015 at 9:38 PM, Deniz Yuret wrote:
> Here is a parallel program:
>
> M = [rand(1000,1000) for i=1:16]
> @time pmap(svd, M)
>
> Here are timing results for local workers on a 16 core machine1:
>
> julia -p 2: 14.98 secs
> julia -p 4: 16.02 secs
> julia -p 8: 17.64 secs
>
> Here are timing results for machine1 connecting to remote workers on same
> type of machine2:
>
> julia --machinefile <2 copies of machine2>: 11.75 secs
> julia --machinefile <4 copies of machine2>: 7.54 secs
> julia --machinefile <8 copies of machine2>: 6.46 secs
>
> At first I thought things got messed up if the master and the slaves were on
> the same machine.
> But it turns out the difference is between -p vs. --machinefile. If I
> rerun the same test on
> a single machine, but use --machinefile instead of -p n:
>
> julia --machinefile <2 copies of machine1>: 8.41 secs
> julia --machinefile <4 copies of machine1>: 4.70 secs
> julia --machinefile <8 copies of machine1>: 3.31 secs
>
> I am using Julia Version 0.3.9 (2015-05-30 11:24 UTC).
>
> Why is -p n messed up?
>
> thanks,
> deniz
>
