On Thu, Mar 30, 2017 at 8:39 AM, Lawrence Mitchell <lawrence.mitchell@imperial.ac.uk> wrote:

On 30/03/17 14:28, Matthew Knepley wrote:
> What is going on here? It looks like you are using subprocess. Why
> would you do that on a cluster rather than MPI?

It's all pretty icky.  One of the JIT steps involves forking
something.  Plausibly, Henrik, your MPI doesn't like fork.  I went
round at one point to try and set up a single subprocess that was able
to fork before MPI_Init.

For example, when using craypich, I need to say:

export MPICH_GNI_FORK_MODE=FULLCOPY

Old OpenMPI versions, especially those using some infiniband stuff,
don't like fork either, for example
https://www.open-mpi.org/faq/?category=openfabrics#ofa-fork

Matt, here is David's response (you're not subscribed I think, so
didn't get it):

Is there a simple thing we can do to shut this off for testing? He is on a cluster I believe.

Hendrik, do you know what MPI you are using?

  Thanks,

    Matt

 

> Hi Matt,
>
> Are you sure? To me it looks like pulp is using subprocess to fork the linear program solver. Nothing to do with parallel.
>
> David

Lawrence

--

What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

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