SYNTAX¶

mpicc [--showme | --showme:compile | --showme:link] ...

mpic++ [--showme | --showme:compile | --showme:link] ...

mpicxx [--showme | --showme:compile | --showme:link] ...

mpifort [--showme | --showme:compile | --showme:link] ...

mpijavac [--showme | --showme:compile | --showme:link] ...

The following deprecated commands are also available — but mpifort should be used instead:

mpif77 [--showme | --showme:compile | --showme:link] ...

mpif90 [--showme | --showme:compile | --showme:link] ...

On case-sensitive filesystems, the following command will also be available:

mpiCC [--showme | --showme:compile | --showme:link] ...

OPTIONS¶

The options below apply to all of the wrapper compilers:

See the man page for your underlying compiler for other options that can be passed through mpicc.

DESCRIPTION¶

Conceptually, the role of these commands is quite simple: transparently add relevant compiler and linker flags to the user’s command line that are necessary to compile / link Open MPI programs, and then invoke the underlying compiler to actually perform the command.

As such, these commands are frequently referred to as “wrapper” compilers because they do not actually compile or link applications themselves; they only add in command line flags and invoke the back-end compiler.

BACKGROUND¶

Open MPI provides wrapper compilers for several languages:

The wrapper compilers for each of the languages are identical; they can be use interchangeably. The different names are provided solely for backwards compatibility.

FORTRAN NOTES¶

The Fortran wrapper compiler for MPI (mpifort, and its legacy/deprecated names mpif77 and mpif90) can compile and link MPI applications that use any/all of the MPI Fortran bindings: mpif.h, the mpi module, and the mpi_f08 module (assuming Open MPI was installed with support for each of these Fortran bindings). Specifically: it is no longer necessary to use different wrapper compilers for applications that use mpif.h vs. applications that use the mpi module — just use mpifort for all Fortran MPI applications.

Note, however, that the Fortran compiler may require additional command-line options to enforce a specific Fortran dialect. For example, in some versions of the IBM XLF compiler, if xlf90 is the underlying Fortran compiler, -qfixed may be necessary to compile fixed-format Fortran source files.

Finally, note that mpifort will be inoperative and will return an error on use if Fortran support was not built into the MPI layer.

OVERVIEW¶

mpicc is a convenience wrappers for the underlying C compiler. Translation of an Open MPI program requires the linkage of the Open MPI-specific libraries which may not reside in one of the standard search directories of ld(1). It also often requires the inclusion of header files what may also not be found in a standard location.

mpicc passes its arguments to the underlying C compiler along with the -I, -L and -l options required by Open MPI programs.

The same is true for all the other language wrapper compilers.

The Open MPI Team strongly encourages using the wrapper compilers instead of attempting to link to the Open MPI libraries manually. This allows the specific implementation of Open MPI to change without forcing changes to linker directives in users’ Makefiles. Indeed, the specific set of flags and libraries used by the wrapper compilers depends on how Open MPI was configured and built; the values can change between different installations of the same version of Open MPI.

Indeed, since the wrappers are simply thin shells on top of an underlying compiler, there are very, very few compelling reasons not to use Open MPI’s wrapper compilers. When it is not possible to use the wrappers directly, the --showme:compile and --showme:link options should be used to determine what flags the wrappers would have used. For example:

shell$ cc -c file1.c `mpicc --showme:compile`
shell$ cc -c file2.c `mpicc --showme:compile`
shell$ cc file1.o file2.o `mpicc --showme:link` -o my_mpi_program

NOTES¶

It is possible to make the wrapper compilers multi-lib aware. That is, the libraries and includes specified may differ based on the compiler flags specified (for example, with the GNU compilers on Linux, a different library path may be used if -m32 is seen versus -m64 being seen). This is not the default behavior in a standard build, but can be activated (for example, in a binary package providing both 32 and 64 bit support). More information can be found here.

FILES¶

The strings that the wrapper compilers insert into the command line before invoking the underlying compiler are stored in a text file created by Open MPI and installed to $pkgdata/NAME-wrapper-data.txt, where:

It is rarely necessary to edit these files, but they can be examined to gain insight into what flags the wrappers are placing on the command line.

ENVIRONMENT VARIABLES¶

By default, the wrappers use the compilers that were selected when Open MPI was configured. These compilers were either found automatically by Open MPI’s “configure” script, or were selected by the user in the CC, CXX, and/or FC environment variables before configure was invoked. Additionally, other arguments specific to the compiler may have been selected by configure.

These values can be selectively overridden by either editing the text files containing this configuration information (see the FILES section), or by setting selected environment variables of the form ompi_value.

Valid value names are:

COPYRIGHT¶

2003-2024, The Open MPI Community