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Subject: Re: [OMPI users] "ssh: connect to host XXX.XXX.XXX.XX port 22: connection timed out" errors during mpirun
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-06-07 09:06:36


On Jun 6, 2013, at 10:33 PM, vacate <vacatehoping_at_[hidden]> wrote:

> Hello Castain,
>
> Thank you for your reply!
>
> Actually, the thing I'm doing now is that I want to see how many OpenMPI jobs can be handled in one computer at the same ...

That is a simple question to answer. If you don't care about performance, the number is limited solely by the OS limit on the number of open file descriptors you are allowed to have.

http://www.open-mpi.org/faq/?category=large-clusters#fd-limits

>
> So I'm trying to figure out the reason of the problem that I meet now.
>
> It seems that it's not the limit of OpenMPI, and the real reason is my computer can't handle a huge amount of connection in a short time.
>
> Is that right?

Running it the way you are, yes - you're simply overwhelming the ssh system.

>
> Thank you very much again!!
>
>
> Sincerely,
> Jen
>
>
> On Thu, Jun 6, 2013 at 5:24 AM, Ralph Castain <rhc_at_[hidden]> wrote:
> It has nothing to do with OMPI - this is an ssh issue. I suspect you are simply overwhelming the connection system.
>
> Maybe you could tell us what you are actually trying to accomplish - running thousands of mpiruns in parallel seems a tad extreme.
>
>
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