FindMPI

Find a Message Passing Interface (MPI) implementation

The Message Passing Interface (MPI) is a library used to write high-performance distributed-memory parallel applications, and is typically deployed on a cluster. MPI is a standard interface (defined by the MPI forum) for which many implementations are available.

Variables

This module will set the following variables per language in your project, where <lang> is one of C, CXX, or Fortran:

MPI_<lang>_FOUND

Variable indicating the MPI settings for <lang> were found.

MPI_<lang>_COMPILER

MPI Compiler wrapper for <lang>.

MPI_<lang>_COMPILE_FLAGS

Compilation flags for MPI programs, separated by spaces. This is not a ;-list.

MPI_<lang>_INCLUDE_PATH

Include path(s) for MPI header.

MPI_<lang>_LINK_FLAGS

Linker flags for MPI programs.

MPI_<lang>_LIBRARIES

All libraries to link MPI programs against.

Additionally, the following IMPORTED targets are defined:

MPI::MPI_<lang>

Target for using MPI from <lang>.

Additionally, FindMPI sets the following variables for running MPI programs from the command line:

MPIEXEC

Executable for running MPI programs, if provided.

MPIEXEC_NUMPROC_FLAG

Flag to pass to MPIEXEC before giving it the number of processors to run on.

MPIEXEC_MAX_NUMPROCS

Number of MPI processors to utilize. Defaults to the number of processors detected on the host system.

MPIEXEC_PREFLAGS

Flags to pass to MPIEXEC directly before the executable to run.

MPIEXEC_POSTFLAGS

Flags to pass to MPIEXEC after other flags.

Usage

To use this module, call find_package(MPI). If you are happy with the auto-detected configuration for your language, then you’re done. If not, you have two options:

1. Set MPI_<lang>_COMPILER to the MPI wrapper (e.g. mpicc) of your choice and reconfigure. FindMPI will attempt to determine all the necessary variables using that compiler’s compile and link flags.
2. If this fails, or if your MPI implementation does not come with a compiler wrapper, then set both MPI_<lang>_LIBRARIES and MPI_<lang>_INCLUDE_PATH. You may also set any other variables listed above, but these two are required. This will circumvent autodetection entirely.

When configuration is successful, MPI_<lang>_COMPILER will be set to the compiler wrapper for <lang>, if it was found. MPI_<lang>_FOUND and other variables above will be set if any MPI implementation was found for <lang>, regardless of whether a compiler was found.

When using MPIEXEC to execute MPI applications, you should typically use all of the MPIEXEC flags as follows:

${MPIEXEC} ${MPIEXEC_NUMPROC_FLAG} ${MPIEXEC_MAX_NUMPROCS}
  ${MPIEXEC_PREFLAGS} EXECUTABLE ${MPIEXEC_POSTFLAGS} ARGS

where EXECUTABLE is the MPI program, and ARGS are the arguments to pass to the MPI program.

Backward Compatibility

For backward compatibility with older versions of FindMPI, these variables are set, but deprecated:

MPI_FOUND           MPI_COMPILER        MPI_LIBRARY
MPI_COMPILE_FLAGS   MPI_INCLUDE_PATH    MPI_EXTRA_LIBRARY
MPI_LINK_FLAGS      MPI_LIBRARIES

In new projects, please use the MPI_<lang>_XXX equivalents.