[mvapich-discuss] mvapich2 and openmp

[Ranjit Noronha]

Hi Dominique,

> 
> I am trying to use mvapich2-0.9.8p2, built with 
> --enable-threads=multiple, with a program where the various threads
> are created by OpenMP. When running the program, the threads
> are correctly created and executed, but always SEQUENTIALLY
> (each node is a two dual-core processors, and could thus accomodate
> 4 threads). When threads are created manually (not with OpenMP),
> everything works fine. Any idea of what could be wrong?
> Each node runs a Fedora Core 5 distribution with a SMP 2.6.21.3
> linux kernel (similar behaviour observed for various kernels).
> I tried with gcc, version 4.2, and the Intel C compiler, version 9.1,
> with similar results.
>

Can you let us know the application you are using? If possible can we get 
a copy of this application. 

To allow us to better diagnose the problem can you also give us some details
about the OpenMP parallel directives you are using to create the threads 
in your program?  Did you set the environment variable OMP_NUM_THREADS to
4?


Also, what kind of operations are you using in the parallel
sections? Do you have any critical sections or locks in the parallel section
that might be serializing things?

A code snippet of the OpenMP parallel sections as well the version where 
threads are created manually will be helpful.

thanks,
--ranjit