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Subject: Re: [OMPI users] Problems in OpenMPI
From: Yin Feng (yfeng1_at_[hidden])
Date: 2009-07-12 20:49:14


Can you give me a further explanation about why results are different
when it ran it on mutiprocessors against single processor?

Thank you!

On Fri, Jul 10, 2009 at 4:20 AM, Ashley Pittman<ashley_at_[hidden]> wrote:
> On Thu, 2009-07-09 at 23:40 -0500, Yin Feng wrote:
>> I am a beginner in MPI.
>>
>> I ran an example code using OpenMPI and it seems work.
>> And then I tried a parallel example in PETSc tutorials folder (ex5).
>>
>> mpirun -np 4 ex5
>> It can do but the results are not as accurate as just running ex5.
>> Is that thing normal?
>
> Not as accurate or just different?  Different is normal and in light of
> that accurate is itself a vague concept.
>
>> After that, send this job to supercomputer which allocates me 4 nodes
>> and each node has 8 processors. When I check load on each node, I
>> found:
>
>> Does anyone have any idea about this?
>
> I'd say it's obvious all 32 processes have been located on the same
> node, what was the mpirun command you issued and the contents of the
> machinefile you used?
>
> Running "orte-ps" on the machine where the mpirun command is running
> will tell you the hostname where every rank is running or if you want
> more information (load, cpu usage etc) you can use padb, the link for
> which is in my signature.
>
> Ashley,
>
> --
>
> Ashley Pittman, Bath, UK.
>
> Padb - A parallel job inspection tool for cluster computing
> http://padb.pittman.org.uk
>
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