[IPython-dev] ipython1 and mpi
ellisonbg.net at gmail.com
Wed May 30 15:37:51 EDT 2007
Here is a broad picture of how mpi integration works:
1) When the engines start, the look for a configuration variable
called mpiImportStatement. If it is set, that strings gets exec'd the
first thing when the engine starts. This statement should be a python
statement that causes mpi_init to be called. A typically example is:
mpiImportStatement = "from mpi4py import MPI as mpi"
The docstrings for mpiImportStatement are here:
To set this variable, use the file mpirc.py as a template and drop it
into your ~/.ipython directory.
> does that mean that it is my option to call mpi_init by hand or does
> it somehow happen behind the scenes? i understand that i have to use
> mpirun to launch the engines.
2) Then you must start the engines using
To use mpi from within swig wrapped code there are a few things you
will have to figure out:
1) Does that wrapped code call mpi_init, or does it expect that
mpi_init has already been called?
2) Which mpi implementation are you using? With a modern mpi
implementation like openmpi, things are fairly easy. If you are using
an older version like mpich1, like becomes much more complicated
because of how mpich starts processes. I can show you how to get that
going if you need to.
Here is how I would go about things:
* Use openmpi and install the mpi4py python bindings to mpi
* Set the mpiImportStatement to import mpi4py. This will cause
mpi_init to be called.
* Make sure that your wrapped code doesn't call mpi_init again.
With that, things should just work. Let me know how this goes - I
realize all of this is still somewhat complicated.
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