Bug#944631: python3-mpi4py: import sends messages to stderr

[Drew Parsons]

On Tue, 12 Nov 2019 16:20:25 -0800 Jameson Graef Rollins 
<jrollins at finestructure.net> wrote:
> Package: python3-mpi4py
> 
> A simple import of the MPI subpackage causes a warning message to be
> sent to stderr:
> 
> servo:~ 0$ python3 -c 'from mpi4py import MPI'
> -------------------------------------------------------------------
-------
> [[11193,1],0]: A high-performance Open MPI point-to-point messaging
module
> was unable to find any relevant network interfaces:
> 
> Module: OpenFabrics (openib)
>   Host: servo
> 
> Another transport will be used instead, although this may result in
> lower performance.
> 
> NOTE: You can disable this warning by setting the MCA parameter
> btl_base_warn_component_unused to 0.
> -------------------------------------------------------------------
-------
> servo:~ 0$
> 
> This is bad form and is causing problems to applications build
against
> packages using this library (such as h5py).


Hi Jamie, this warning comes from OpenMPI and depends on system 
configuration (i.e. whether or not an openib transport is available).

If the warning is causing a problem then you can ignore it by setting
export OMPI_MCA_btl_base_warn_component_unused=0
in the environment.

This is similar to other OpenMPI features which can be controlled the 
same way, e.g. allowing oversubscribing of CPUs with `export 
OMPI_MCA_rmaps_base_oversubscribe=1`

Drew