[Users] MPI error in tutorial for new users

[Roland Haas]

Hello Praveer,

glad to see that you could make it work in the end.

Yours,
Roland

> Dear Dr. Roland,
> 
> Thank you for your detailed response. I really appreciate the time and
> thought you must've put into it.
> 
> I have followed your suggestion of removing the current Cactus build and
> compiling it again but received yet another error. The problem seems to be
> a mixup of multiple MPI implementations, just as you had suggested. I
> couldn't finesse my way out of it, so I re-installed Ubuntu
> instead(deleting everything in the process) and began from scratch. I
> installed only those packages mentioned on the Jupyter tutorial and the
> code compiled successfully this time.
> 
> Thank you once again for your helpful advice.
> 
> Regards,
> Praveer Krishna
> 
> On Fri, Mar 27, 2020 at 8:42 PM Roland Haas <rhaas at illinois.edu> wrote:
> 
> > Hello Praveer Krishna,
> >
> > since mpirun was not found initially it would seem that you had not MPI
> > stack installed when compiling Cactus.
> >
> > Cactus is best used with an MPI stack installed beforehand. The new
> > user tutorial
> >
> >
> > https://nbviewer.jupyter.org/github/nds-org/jupyter-et/blob/master/CactusTutorial.ipynb
> >
> > contains instructions on how to install a set up packages that simplify
> > building Cactus, including MPI. Did you follow those instructions or
> > started from a vanilla, freshly installed OS? Also, what OS are you
> > using (OSX, Linux, Linux-Subsystem-on-Windows)?
> >
> > The easiest way to get a working copy of Cactus, if you did not install
> > an MPI stack before compiling Cactus, is:
> >
> > * install an MPI stack (OpenMPI is fine)
> > * remove the current Cactus build using "rm -rf configs/sim"
> > * build once more
> >
> > The solution above is the suggested solution.
> >
> > If you would like to avoid recompiling (and risk triggering other
> > issues instead), here's an alternative:  When it detected that no MPI
> > stack was installed then Cactus built its own copy of OpenMPI. It will
> > have copied "mpirun" to "exe/sim/mpirun" and you can use that by making
> > sure that the full path to the directory "exe/sim" appears in your PATH
> > before you start the simulation. Using an mpirun from a different MPI
> > stack than the one used to compile Cactus is what gives the error that
> > Erik descibes in the email you found.
> >
> > Yours,
> > Roland
> >  
> > > Dear ET Users,
> > >
> > > I'm a beginner attempting to follow the Jupyter tutorial for new users. I
> > > have been able to  successfully run the helloworld.par and tov_ET.par  
> > files  
> > > with procs set to 1 but I'm having issues when I try to use multiple
> > > processors on my laptop.
> > > I initially got this error <https://imgur.com/a/cuLLp79> saying "mpirun:
> > > not found", following which I installed Open MPI on my system. The error
> > > persisted, so I removed Open MPI and installed mpich instead. This
> > > seemingly fixed the issue, but I received another error
> > > <https://imgur.com/gdXSqCj> saying "CACTUS_NUM_PROCS is set to 4 but  
> > there  
> > > are 1 MPI processes"
> > >
> > > I found one
> > > <  
> > https://www.mail-archive.com/search?l=users@einsteintoolkit.org&q=subject:%22%5C%5BUsers%5C%5D+problem+on+running+bbh+expample%22&o=newest&f=1  
> > >
> > > or two
> > > <https://www.mail-archive.com/users@einsteintoolkit.org/msg01591.html>
> > > previous queries regarding this exact error, but the suggestions have not
> > > worked for me so far. Having never worked with MPI before, I am not sure
> > > what else I should try.
> > >
> > > I'd be grateful for a few words of advice on this issue from anyone in  
> > the  
> > > community.
> > > Thank you in advance for your time.
> > >
> > > Regards,
> > > Praveer Krishna  
> >
> >
> > --
> > My email is as private as my paper mail. I therefore support encrypting
> > and signing email messages. Get my PGP key from http://pgp.mit.edu .
> >  


-- 
My email is as private as my paper mail. I therefore support encrypting
and signing email messages. Get my PGP key from http://pgp.mit.edu .
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