Try setting X10_NTHREADS=1
MPI implementations have been known to play games with thread affinity
On Mon, Dec 20, 2010 at 3:42 PM, Benjamin W Herta <bhe...@us.ibm.com> wrote:
> It's normal for idle places to use CPU - it's constantly checking the
> network for incoming messages. This helps reduce latency when data comes
> in from a remote place, but this background checking may be the cause of
> the slowdown you see. You may want to see if you get better performance
> with the default "sockets" backend.
>
> - Ben
>
>
> |------------>
> | From: |
> |------------>
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |Kirak Hong <hok...@gatech.edu>
> |
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |------------>
> | To: |
> |------------>
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |Mailing list for users of the X10 programming language <
> x10-users@lists.sourceforge.net>
> |
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |------------>
> | Date: |
> |------------>
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |12/20/2010 03:19 PM
> |
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |------------>
> | Subject: |
> |------------>
>
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> >--------------------------------------------------------------------------------------------------------------------------------------------------|
> |[X10-users] mpi slowdown
> |
>
>
> >--------------------------------------------------------------------------------------------------------------------------------------------------|
>
>
>
>
>
> Hi,
>
> I found that I get a huge slowdown when I use multiple nodes for mpirun
> with
> x10 application. Here are my simple code :
>
> var count:int = 0;
> while(true)
> {
> var t:Long = Timer.milliTime();
>
> for(var i:int = 0; i < 10000000; i++);
>
> Console.OUT.println("count : " + count + ",
> elapsed time = " + (Timer.milliTime() - t));
> count++;
> }
>
> And here are the results :
>
> hok...@hokira-desktop:~/ext/Dropbox/Projects/x10/x10hello$ mpirun -n 1
> Main
> count : 0, elapsed time = 31
> count : 1, elapsed time = 21
> count : 2, elapsed time = 22
> count : 3, elapsed time = 22
> count : 4, elapsed time = 22
>
> hok...@hokira-desktop:~/ext/Dropbox/Projects/x10/x10hello$ mpirun -n 8
> Main
> count : 0, elapsed time = 51
> count : 1, elapsed time = 55
> count : 2, elapsed time = 45
> count : 3, elapsed time = 55
> count : 4, elapsed time = 45
>
> I can see the X10 runtime code but I want to make sure if I did some
> mistake
> while building or running the application.
> Also, I saw CPU utilizations are 100% even when only one place is actually
> running some work. Is this normal behavior of X10 application?
>
> Thanks,
> Kirak
>
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