This is OCamlMPI, an OCaml binding to the Message Passing Interface (MPI).

What is MPI?

MPI is a popular library for distributed-memory parallel programming in SPMD (single program, multiple data) style.

MPI offers both point-to-point message passing and group communication operations (broadcast, scatter/gather, etc).

Several implementations of MPI are available, both for networks of Unix workstations and for supercomputers with specialized communication networks.

More info on MPI is available here.

Two popular, free implementations of MPI are MPICH and OpenMPI .

The OCamlMPI interface

OCamlMPI provides Caml bindings for a large subset of MPI functions. I omitted a number of MPI functions for which I had no use, though. The file mpi.mli in this directory lists the MPI functions provided, along with short documentation. See the MPI docs at the URLs above for more detailed info.

Most communication functions come in 10 flavors:

• one generic function operating on any data type (e.g. Mpi.send)
• nine specialized functions for the following types:

Type	"Send" function
int	Mpi.send_int
float	Mpi.send_float
int array	Mpi.send_int_array
float array	Mpi.send_float_array
Bigarray.Genarray.t	Mpi.send_bigarray
Bigarray.Array0.t	Mpi.send_bigarray0
Bigarray.Array1.t	Mpi.send_bigarray1
Bigarray.Array2.t	Mpi.send_bigarray2
Bigarray.Array3.t	Mpi.send_bigarray3

The generic function is simpler to use, and more general, but involves more overhead than the specialized functions.

The data types that can be transmitted using the generic communication functions are those that can be marshaled by the Marshal.to_channel function (q.v.) with the Marshal.Closures option. That is:

• all concrete data structures (base types, arrays, records, variant types),
• function closures,
• but not objects,
• nor certain abstract types (in_channel, out_channel, Graphics.image).

Building OCamlMPI

If MPI is installed in the standard locations, just do

   make all opt

If MPI headers and libraries cannot be found, you may need to edit the Makefile and set the following variables according to your MPI installation:

• MPIINCDIR directory containing the MPI include file <mpi.h>
• MPILIBDIR directory containing the MPI library -lmpi
• MPICC path to the mpicc executable
• MPIRUN path to the mpirun executable.

You may also need to adjust CFLAGS.

For final installation: become super-user and do make install.

Testing OCamlMPI

make test builds and runs a couple of test programs.

Using OCamlMPI

In native-code:

    ocamlfind ocamlopt -package mpi -linkpkg <your files>

In bytecode:

    ocamlfind ocamlc -package mpi -linkpkg <your files>

Licensing

The OCamlMPI library is copyright 1998 INRIA and distributed under the terms of the GNU Library General Public License version 2, with a special exception on clause 6 described in the file LICENSE.

Support

For issues specific to this OCaml-MPI binding, please use the Github bug tracker.

Questions about the following issues should be directed to MPI newsgroups, mailing-lists or implementation vendors, but not to the issue tracker above: semantics of MPI functions, how to program with MPI, finding and installing implementations of MPI, performance tuning of MPI applications, etc.