The files in this directory are sample MPI applications provided both as a trivial primer to MPI as well as simple tests to ensure that your Open MPI installation is working properly.

If you are looking for a comprehensive MPI tutorial, these samples are not enough. Excellent MPI tutorials are available here.

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There are two MPI examples in this directory, each using one of six different MPI interfaces:

Hello world

The MPI version of the canonical "hello world" program:

• C: hello_c.c
• C++: hello_cxx.cc
• Fortran mpif.h: hello_mpifh.f
• Fortran use mpi: hello_usempi.f90
• Fortran use mpi_f08: hello_usempif08.f90
• Java: Hello.java
• C shmem.h: hello_oshmem_c.c
• Fortran shmem.fh: hello_oshmemfh.f90

Ring

Send a trivial message around in a ring:

• C: ring_c.c
• C++: ring_cxx.cc
• Fortran mpif.h: ring_mpifh.f
• Fortran use mpi: ring_usempi.f90
• Fortran use mpi_f08: ring_usempif08.f90
• Java: Ring.java
• C shmem.h: ring_oshmem_c.c
• Fortran shmem.fh: ring_oshmemfh.f90

Connectivity Test

Additionally, there's one further example application, but this one only uses the MPI C bindings to test the connectivity between all processes:

• C: connectivity_c.c

Makefile

The Makefile in this directory will build as many of the examples as you have language support (e.g., if you do not have the Fortran use mpi bindings compiled as part of Open MPI, those examples will be skipped).

The Makefile assumes that the wrapper compilers mpicc, mpic++, and mpifort are in your path.

Although the Makefile is tailored for Open MPI (e.g., it checks the ompi_info command to see if you have support for mpif.h, the mpi module, and the use mpi_f08 module), all of the example programs are pure MPI, and therefore not specific to Open MPI. Hence, you can use a different MPI implementation to compile and run these programs if you wish.

Make today an Open MPI day!