> On Oct 26, 2014, at 9:56 PM, Brock Palen <bro...@umich.edu> wrote:
> 
> We are starting to look at supporting MPI on our Hadoop/Spark YARN based 
> cluster.

You poor soul…

>  I found a bunch of referneces to Hamster, but what I don't find is if it was 
> ever merged into regular OpenMPI, and if so is it just another RM 
> integration?  Or does it need more setup?

When I left Pivotal, it was based on a copy of the OMPI trunk that sat 
somewhere in the 1.7 series, I believe. Last contact I had indicated they were 
trying to update, but I’m not sure they were successful.

> 
> I found this:
> http://pivotalhd.docs.pivotal.io/doc/2100/Hamster.html 
> <http://pivotalhd.docs.pivotal.io/doc/2100/Hamster.html>

Didn’t know they had actually (finally) released it, so good to know. Just so 
you are aware, there are major problems running MPI under Yarn as it just isn’t 
designed for MPI support. What we did back then was add a JNI layer so that 
ORTE could run underneath it, and then added a PMI-like service to provide the 
wireup support (since Yarn couldn’t be used to exchange the info itself). You 
also have the issue that Yarn doesn’t understand the need for all the procs to 
be launched together, and so you have to modify Yarn so it will ensure that the 
MPI procs are all running or else you’ll hang in MPI_Init.

> 
> Which appears to imply extra setup required.  Is this documented anywhere for 
> OpenMPI?

I’m afraid you’ll just have to stick with the Pivotal-provided version as the 
integration is rather complicated. Don’t expect much in the way of performance! 
This was purely intended as a way for “casual” MPI users to make use of “free” 
time on their Hadoop cluster, not for any serious technical programming.

> 
> Brock Palen
> www.umich.edu/~brockp
> CAEN Advanced Computing
> XSEDE Campus Champion
> bro...@umich.edu
> (734)936-1985
> 
> 
> 
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