[mvapich-discuss] Questions on running mvapich on a cluster

[wei huang]

Hi Marcos,

Thanks for using mvapich2. Please see inline for more detailed answers to
your questions.

> 1) Supposing that mvapich were adequately installed by our sysadmin, what
> exactly is the command to start the mpi daemon on the machines? Currently
> my script uses the following command:
>
> /usr/bin/rsh -n $machine "/home/pcpm/mverissi/my_mvapich_0.9.8/bin/mpdboot
> -n 8 -f /home/pcpm/mverissi/mfile.$idm --ncpus=2
> --mpd=/home/pcpm/mverissi/my_mvapich_0.9.8/bin/mpd --rsh=rsh"
>
> where mfile.$idm is a file containing the machines onto which the mpd will
> be started. Thinking about it now, I guess it would be enough to issue the
> mpdboot command without the /usr/bin/rsh -n $machine  part. Is that
> correct?

You should be able to simply run mpdboot on one of your computing nodes
(any one). More details can be find through our online user guide:

http://mvapich.cse.ohio-state.edu/support/user_guide_mvapich2.html

Is there any specific reason that you are using your own scripts to start
mpd ring?

> 2) If the mpi daemon is started by the sysadmin on the nodes, probably
> he'll start it as root. If he does so, will we "mortal" users be able to
> run their processes? In other words, can one run a calculation using
> mvapich even if the owner of the mpi process is root?

That is feasible. Users can use root's mpd ring by settting environment
variable MPD_USE_ROOT_MPD=1. For more details you can read the
installation guide from the MPICH2 website:

http://www.mcs.anl.gov/research/projects/mpich2/

> 3) The last question concerns the .mpd.conf and .mpdpasswd files. To make
> the calculation run, the only way I could think of was to copy those files
> to the temporary directory that I mentioned in question 2. However, it
> would be nice to have mvapich finding those files in the users' home dirs
> (even if the calculation is being run in a scratch disk) instead of the
> users having to copy them to temporary directories. Is there a way of
> doing this?

Currently mpd daemon is looking into user's home directory for those
files. Are you facing any problem by just have those files in your home
directly? Of course, if you use root's mpd, those files are in
/etc/mpd.conf.

Thanks.

-- Wei