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Subject: Re: [OMPI users] Bad performance when scattering big size of data?
From: Storm Zhang (stormzhg_at_[hidden])
Date: 2010-10-05 10:23:04

Sorry, I should say one more thing about the 500 procs test. I tried to run
two 500 procs at the same time using SGE and it runs fast and finishes at
the same time as the single run. So I think OpenMPI can handle them
separately very well.

For the bind-to-core, I tried to run mpirun --help but not find the
bind-to-core info. I only see bynode or byslot options. Is it same as
bind-to-core? My mpirun shows version 1.3.3 but ompi_info shows 1.4.2.

Thanks a lot.


On Mon, Oct 4, 2010 at 9:18 PM, Eugene Loh <eugene.loh_at_[hidden]> wrote:

> Storm Zhang wrote:
>> Here is what I meant: the results of 500 procs in fact shows it with
>> 272-304(<500) real cores, the program's running time is good, which is
>> almost five times 100 procs' time. So it can be handled very well. Therefore
>> I guess OpenMPI or Rocks OS does make use of hyperthreading to do the job.
>> But with 600 procs, the running time is more than double of that of 500
>> procs. I don't know why. This is my problem.
>> BTW, how to use -bind-to-core? I added it as mpirun's options. It always
>> gives me error " the executable 'bind-to-core' can't be found. Isn't it
>> like:
>> mpirun --mca btl_tcp_if_include eth0 -np 600 -bind-to-core scatttest
> Thanks for sending the mpirun run and error message. That helps.
> It's not recognizing the --bind-to-core option. (Single hyphen, as you
> had, should also be okay.) Skimming through the e-mail, it looks like you
> are using OMPI 1.3.2 and 1.4.2. Did you try --bind-to-core with both? If I
> remember my version numbers, --bind-to-core will not be recognized with
> 1.3.2, but should be with 1.4.2. Could it be that you only tried 1.3.2?
> Another option is to try "mpirun --help". Make sure that it reports
> --bind-to-core.
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