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.

New in version 3.10: Major overhaul of the module: many new variables, per-language components, support for a wider variety of runtimes.

Variables for using MPI

The module exposes the components C, CXX, MPICXX and Fortran. Each of these controls the various MPI languages to search for. The difference between CXX and MPICXX is that CXX refers to the MPI C API being usable from C++, whereas MPICXX refers to the MPI-2 C++ API that was removed again in MPI-3.

Depending on the enabled components the following variables will be set:


Variable indicating that MPI settings for all requested languages have been found. If no components are specified, this is true if MPI settings for all enabled languages were detected. Note that the MPICXX component does not affect this variable.


Minimal version of MPI detected among the requested languages, or all enabled languages if no components were specified.

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


Variable indicating the MPI settings for <lang> were found and that simple MPI test programs compile with the provided settings.


MPI compiler for <lang> if such a program exists.


Compilation options for MPI programs in <lang>, given as a ;-list.


Compilation definitions for MPI programs in <lang>, given as a ;-list.


Include path(s) for MPI header.


Linker flags for MPI programs.


All libraries to link MPI programs against.

New in version 3.9: Additionally, the following IMPORTED targets are defined:


Target for using MPI from <lang>.

The following variables indicating which bindings are present will be defined:


Variable indicating whether the MPI-2 C++ bindings are present (introduced in MPI-2, removed with MPI-3).


True if the Fortran 77 header mpif.h is available.


True if the Fortran 90 module mpi can be used for accessing MPI (MPI-2 and higher only).


True if the Fortran 2008 mpi_f08 is available to MPI programs (MPI-3 and higher only).

If possible, the MPI version will be determined by this module. The facilities to detect the MPI version were introduced with MPI-1.2, and therefore cannot be found for older MPI versions.


Major version of MPI implemented for <lang> by the MPI distribution.


Minor version of MPI implemented for <lang> by the MPI distribution.


MPI version implemented for <lang> by the MPI distribution.

Note that there's no variable for the C bindings being accessible through mpi.h, since the MPI standards always have required this binding to work in both C and C++ code.

For running MPI programs, the module sets the following variables


Executable for running MPI programs, if such exists.


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


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


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


Flags to pass to mpiexec after other flags.

Variables for locating MPI

This module performs a four step search for an MPI implementation:

  1. Search for MPIEXEC_EXECUTABLE and, if found, use its base directory.

  2. Check if the compiler has MPI support built-in. This is the case if the user passed a compiler wrapper as CMAKE_<LANG>_COMPILER or if they use Cray system compiler wrappers.

  3. Attempt to find an MPI compiler wrapper and determine the compiler information from it.

  4. Try to find an MPI implementation that does not ship such a wrapper by guessing settings. Currently, only Microsoft MPI and MPICH2 on Windows are supported.

For controlling the MPIEXEC_EXECUTABLE step, the following variables may be set:


Manually specify the location of mpiexec.


Specify the base directory of the MPI installation.


Environment variable to specify the base directory of the MPI installation.


Environment variable to specify the base directory of the MPI installation.

For controlling the compiler wrapper step, the following variables may be set:


Search for the specified compiler wrapper and use it.


Flags to pass to the MPI compiler wrapper during interrogation. Some compiler wrappers support linking debug or tracing libraries if a specific flag is passed and this variable may be used to obtain them.


Used to initialize MPI_<lang>_COMPILER_FLAGS if no language specific flag has been given. Empty by default.


A suffix which is appended to all names that are being looked for. For instance you may set this to .mpich or .openmpi to prefer the one or the other on Debian and its derivatives.

In order to control the guessing step, the following variable may be set:


Valid values are MSMPI and MPICH2. If set, only the given library will be searched for. By default, MSMPI will be preferred over MPICH2 if both are available. This also sets MPI_SKIP_COMPILER_WRAPPER to true, which may be overridden.

Each of the search steps may be skipped with the following control variables:


If true, the module assumes that the compiler itself does not provide an MPI implementation and skips to step 2.


If true, no compiler wrapper will be searched for.


If true, the guessing step will be skipped.

Additionally, the following control variable is available to change search behavior:


Add some definitions that will disable the MPI-2 C++ bindings. Currently supported are MPICH, Open MPI, Platform MPI and derivatives thereof, for example MVAPICH or Intel MPI.

If the find procedure fails for a variable MPI_<lang>_WORKS, then the settings detected by or passed to the module did not work and even a simple MPI test program failed to compile.

If all of these parameters were not sufficient to find the right MPI implementation, a user may disable the entire autodetection process by specifying both a list of libraries in MPI_<lang>_LIBRARIES and a list of include directories in MPI_<lang>_ADDITIONAL_INCLUDE_DIRS. Any other variable may be set in addition to these two. The module will then validate the MPI settings and store the settings in the cache.

Cache variables for MPI

The variable MPI_<lang>_INCLUDE_DIRS will be assembled from the following variables. For C and CXX:


Location of the mpi.h header on disk.

For Fortran:


Location of the Fortran 77 header mpif.h, if it exists.


Location of the mpi or mpi_f08 modules, if available.

For all languages the following variables are additionally considered:


A ;-list of paths needed in addition to the normal include directories.


Path variables for include folders referred to by <include_name>.


A ;-list of <include_name> that will be added to the include locations of <lang>.

The variable MPI_<lang>_LIBRARIES will be assembled from the following variables:


The location of a library called <lib_name> for use with MPI.


A ;-list of <lib_name> that will be added to the include locations of <lang>.

Usage of mpiexec

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


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

Advanced variables for using MPI

The module can perform some advanced feature detections upon explicit request.

Important notice: The following checks cannot be performed without executing an MPI test program. Consider the special considerations for the behavior of try_run() during cross compilation. Moreover, running an MPI program can cause additional issues, like a firewall notification on some systems. You should only enable these detections if you absolutely need the information.

If the following variables are set to true, the respective search will be performed:


Determine for all available Fortran bindings what the values of MPI_SUBARRAYS_SUPPORTED and MPI_ASYNC_PROTECTS_NONBLOCKING are and make their values available as MPI_Fortran_<binding>_SUBARRAYS and MPI_Fortran_<binding>_ASYNCPROT, where <binding> is one of F77_HEADER, F90_MODULE and F08_MODULE.


For each language, find the output of MPI_Get_library_version and make it available as MPI_<lang>_LIBRARY_VERSION_STRING. This information is usually tied to the runtime component of an MPI implementation and might differ depending on <lang>. Note that the return value is entirely implementation defined. This information might be used to identify the MPI vendor and for example pick the correct one of multiple third party binaries that matches the MPI vendor.

Backward Compatibility

Deprecated since version 3.10.

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


In new projects, please use the MPI_<lang>_XXX equivalents. Additionally, the following variables are deprecated:




For consumption use MPI_<lang>_INCLUDE_DIRS and for specifying folders use MPI_<lang>_ADDITIONAL_INCLUDE_DIRS instead.