Run an MPI program


    mpiexec args executable pgmargs [ : args executable pgmargs ... ]
where args are command line arguments for mpiexec (see below), executable is the name of an executable MPI program, and pgmargs are command line arguments for the executable. Multiple executables can be specified by using the colon notation (for MPMD - Multiple Program Multiple Data applications). For example, the following command will run the MPI program a.out on 4 processes:
    mpiexec -n 4 a.out

The MPI standard specifies the following arguments and their meanings:

-n <np>
Specify the number of processes to use
-host <hostname>
Name of host on which to run processes
-arch <architecture name>
Pick hosts with this architecture type
-wdir <working directory>
cd to this one before running executable
-path <pathlist>
use this to find the executable
-soft <triplets>
comma separated triplets that specify requested numbers of processes (see the MPI-2 specification for more details)
-file <name>
implementation-defined specification file
-configfile <name>
file containing specifications of host/program, one per line, with # as a comment indicator, e.g., the usual mpiexec input, but with ":" replaced with a newline. That is, the configfile contains lines with -soft, -n etc.

Additional arguments that are specific to the MPICH implementation are discussed below.

Note that not all of these parameters are meaningful for all systems. For example, the gforker version of mpiexec creates all processes on the same system on which it is running; in that case, the \-arch and \-host options are ignored.

The colon character (:) may be used to separate different executables for MPMD (multiple program multiple data) programming. For example, to run the program ocean on 4 processes and air on 8 processes, use:

    mpiexec -n 4 ocean : -n 8 air

MPICH-Specific Arguments

Many of the implementations of process managers in MPICH support the following arguments to mpiexec:

-np <num>
A synonym for the standard \-n argument
-env <name> <value>
Set the environment variable <name> to <value> for the processes being run by mpiexec
Pass no environment variables (other than ones specified with other \-env or \-genv arguments) to the processes being run by mpiexec. By default, all environment variables are provided to each MPI process (rationale: principle of least surprise for the user)
-envlist <list>
Pass the listed environment variables (names separated by commas), with their current values, to the processes being run by mpiexec.
-genv <name> <value>
The \-genv options have the same meaning as their corresponding \-env version, except they apply to all executables, not just the current executable (in the case that the colon syntax is used to specify multiple execuables).
Like \-envnone, but for all executables
-genvlist <list>
Like \-envlist, but for all executables
-usize <n>
Specify the value returned for the value of the attribute MPI_UNIVERSE_SIZE.
Label standard out and standard error (stdout and stderr) with the rank of the process
-maxtime <n>
Set a timelimit of <n> seconds.
Provide more information on the reason each process exited if there is an abnormal exit

Environment variables for mpiexec

The following environment variables are understood by some versions of mpiexec. The command line arguments have priority over these; that is, if both the environment variable and command line argument are used, the value specified by the command line argument is used.

Maximum running time in seconds. mpiexec will terminate MPI programs that take longer than the value specified by MPIEXEC_TIMEOUT.
Set the universe size
Set the range of ports that mpiexec will use in communicating with the processes that it starts. The format of this is <low>:<high>. For example, to specify any port between 10000 and 10100, use 10000:10100.
Has the same meaning as MPIEXEC_PORT_RANGE and is used if MPIEXEC_PORT_RANGE is not set.
If this environment variable is set, output to standard output is prefixed by the rank in MPI_COMM_WORLD of the process and output to standard error is prefixed by the rank and the text (err); both are followed by an angle bracket (>). If this variable is not set, there is no prefix.
Set the prefix used for lines sent to standard output. A %d is replaced with the rank in MPI_COMM_WORLD; a %w is replaced with an indication of which MPI_COMM_WORLD in MPI jobs that involve multiple MPI_COMM_WORLDs (e.g., ones that use MPI_Comm_spawn or MPI_Comm_connect).
Like MPIEXEC_PREFIX_STDOUT, but for standard error.

Return Status

mpiexec returns the maximum of the exit status values of all of the processes created by mpiexec.