[MITgcm-support] Problems running the MITgcm in parallel

[Ed Hill]

On Thu, 2004-09-30 at 17:55, Kevin Oliver wrote:
> Hello,
> 
> I'm running MITgcm on a beowulf cluster and Linux platform. 
> There are two problems, which may be related, which mean I 
> can't get it to work in parallel.

Hi Kevin,

We use MITgcm with numerous compilers (Gnu, Intel, PGI) and MPI
libraries on a routine basis.  So its somewhat unlikely that you've
found a bug in MITgcm.  Whats more likely is that you have a problem
with your MPI and/or compiler setup.

So my first question is: are you certain that your mpich-gm install and
your compiler (PGI) are working correctly together?  That is, can you
create simple "hello world"-type programs that compile, link, and run in
parallel?  This should be the first thing to test.


> 1. When I use the genmake2 command, the option -mpi is not 
> recognised. Using the -optfile option, I can link to a 
> libraries for mpi compilation, and it appears to compile 
> successfully using mpich-gm and pgi (portland group 
> compilers). However...

Could you please send us the *exact* syntax that you used to invoke
genmake2 and the *exact* (please cut-and-paste) error message(s) along
with the MITgcm version that you're using?


> 2. When I run the code in parallel, after (I think) 1 time step, the 
> execution is stopped due to extreme values (there are lots of nans, 
> although not only nans). I get the message "Possibly you have 
> different setenv PARALLEL and nThreads?" The equivalent run
> works fine sequentially. I've read about parallel threads, but 
> haven't managed to work out where to set these.

How are you running the code?  Are you certain that you've used the
correct "mpirun ..." or equivalent syntax?

Again, I think it would be best for you to first confirm that you have
the compiler and MPI libraries working by running a simple test
program.  When you're sure that those parts are functioning, then move
on to the MITgcm model.

Ed

-- 
Edward H. Hill III, PhD
office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
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