pyMPI and calling MPI functions using Boost.Python

[Natsu Mizutani]

Hello,

I'm trying to wrap a c++ library using MPI inside with boost.python
(or SWIG).
I managed to find that calling `MPI::Init()` embeded in a c++ funtion
would not work.  So, I decided to use `pyMPI`.
To avoid overhead of pickling and unpickling while calling `mpi.send`
in Python, I'd rather call c++ functions `MPI::Isend()` etc. embeded
in a c++ function.

What I'd like to know is the following:
After starting `pyMPI` session, it seems to work call c++ function
`MPI::Isend()` or `MPI::Irecv()`, etc. from the `pyMPI`,
at least for my small test code attached below.

Is it guaranteed to work for larger scale code?
I mean for larger memory allocation, heavily repeated message passing,
, many paralell processes.
Or, the example worked only with some luck?
As for now, `mpiCC` is built without shared library.

Any suggestions?

Thank you.

--Natsu

----- A small test code mpitest.so works like this -----
$ mpirun -np 2 /usr/bin/pyMPI
Python 2.2.1 (#1, Jan 22 2003, 19:07:20)
[GCC 2.95.3 20010315 (release)] on linux2
Copyright (c) 2001, 2002 Python Software Foundation.
All Rights Reserved.

Copyright (c) 2000 BeOpen.com.
All Rights Reserved.

Copyright (c) 1995-2001 Corporation for National Research Initiatives.
All Rights Reserved.

Copyright (c) 1991-1995 Stichting Mathematisch Centrum, Amsterdam.
All Rights Reserved.
 >>> import mpi
 >>> import mpitest
 >>> print "hello ", mpi.rank, mpi.size
hello  0 2
hello  1 2
 >>> bnd = mympi.bndry(6)
 >>> bnd.mpiTest(mpi.rank, mpi.size - 1 - mpi.rank)
100, 99, 98, 97, 96, 95,  was a rtmp for node:0
100, 101, 102, 103, 104, 105,  was a rtmp for node:1>>>


----- mpitest.so is made from the following using Boost.Python.
//ftest.cpp
#include "ftest.h"

//ftest.h
#include <iostream>
#include <mpi++.h>

class bndry{
     MPI::Request sreq_, rreq_;
     double* stmp_;
     double* rtmp_;
   public:
     int n_;
     bndry(int n) : n_(n) {
     stmp_ = new double[n];
     rtmp_ = new double[n];
     }
     ~bndry(){
       delete [] stmp_;
       delete [] rtmp_;
     };
     void mpiTest(int me, int other) {
       double c0 = 1.0;
       if (me == 1) c0 = -1.0;
       unsigned int ii = 0;
       // Create diffrent arrays in diffrent nodes
       for (int k = 0; k < n_; ++k) {
           stmp_[ii++] = 100.0 + c0 * k;
       }
       sreq_ = MPI::COMM_WORLD.Isend(stmp_, ii, MPI::DOUBLE, other, me);
       rreq_ = MPI::COMM_WORLD.Irecv(rtmp_, ii, MPI::DOUBLE,
           other, other);
       rreq_.Wait();
       for (int k = 0; k < n_; ++k) {
         cout << rtmp_[k] << ", ";
       }
       cout << " was a rtmp for node:" << me << endl;
       sreq_.Wait();
     }
};

//mpitest.cpp
#include <boost/python.hpp>
#include <boost/cstdint.hpp>
#include <fblock.h>
using namespace boost::python;
BOOST_PYTHON_MODULE(mpitest) {
     class_< bndry >("bndry", init< const bndry& >())
         .def(init< int >())
         .def_readwrite("n_", &bndry::n_)
         .def("mpiTest", &bndry::mpiTest)
     ;
}