[petsc-users] Debugging MatAssemblyEnd

[Jed Brown]

On Fri, Aug 26, 2011 at 08:12, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> Do you claim I should not use MPI_Barrier at all when only programming
> Petsc? Is really all required synchronization managed automatically?
>

Yes, apart from unconventional/discouraged things like communicating through
the file system, and even then, you should usually do without barriers.


>
> I do some raw MPI programming before and after, but not inside the
> Petsc core solver.
>

Common problems include having one or more of your processes hung up in this
earlier phase and possible tag collisions. If you are doing nontrivial
things in your pure MPI code, you should either create the communicator
yourself or MPI_Comm_dup() one that you get from PETSc.
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