6. Validating your installation

6.1. Checking your Open MPI configuration

The ompi_info command can be used to check the status of your Open MPI installation (located in PREFIX/bin/ompi_info). Running it with no arguments provides a summary of information about your Open MPI installation.

Note that the ompi_info command is extremely helpful in determining which components are installed as well as listing all the run-time settable parameters that are available in each component (as well as their default values).

The following ompi_info options may be helpful:

  • --all: Show a lot of information about your Open MPI installation.

  • --parsable: Display all the information in a machine-parsable format.

  • --param FRAMEWORK COMPONENT: A FRAMEWORK value of all and a COMPONENT value of all will show all parameters to all components. Otherwise, the parameters of all the components in a specific framework, or just the parameters of a specific component can be displayed by using an appropriate FRAMEWORK and/or COMPONENT name.

  • --level LEVEL: By default, ompi_info only shows “Level 1” MCA parameters – parameters that can affect whether MPI processes can run successfully or not (e.g., determining which network interfaces to use). The --level option will display all MCA parameters from level 1 to LEVEL (the max LEVEL value is 9). Use ompi_info --param FRAMEWORK COMPONENT --level 9 to see all MCA parameters for a given component. See “The Modular Component Architecture (MCA)” section, below, for a fuller explanation.

Error

TODO move the ref below to a better / more-prominent place to explain how to set MCA params.

Changing the values of these parameters is explained in the Internal frameworks section.

6.2. Testing your Open MPI installation

When verifying a new Open MPI installation, we recommend running the following tests in order (the tests build upon each other):

  1. Use mpirun to launch a non-MPI program (e.g., hostname or uptime) across multiple nodes.

  2. Use mpirun to launch a trivial MPI program that does no MPI communication (e.g., the hello_c program in the examples/ directory in the Open MPI distribution).

  3. Use mpirun to launch a trivial MPI program that sends and receives a few MPI messages (e.g., the ring_c program in the examples/ directory in the Open MPI distribution).

  4. Use oshrun to launch a non-OpenSHMEM program across multiple nodes.

  5. Use oshrun to launch a trivial MPI program that does no OpenSHMEM communication (e.g., hello_shmem.c program in the examples/ directory in the Open MPI distribution.)

  6. Use oshrun to launch a trivial OpenSHMEM program that puts and gets a few messages (e.g., the ring_shmem.c in the examples/ directory in the Open MPI distribution.)

If you can run all of these tests successfully, that is a good indication that Open MPI built and installed properly.