mpif77(1)							     Open MPI								 mpif77(1)

NAME

       mpif77 -- Open MPI Fortran 77 wrapper compiler

SYNTAX

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

OPTIONS

       -showme
	      Do  not  invoke  the underlying compiler.  Instead, show the command line that would be executed to compile the program.	NOTE: If a
	      non-filename argument is passed on the command line, the -showme option will not display any additional flags.   For  example,  both
	      "mpif77  --showme"  and  "mpif77	--showme my_source.c" will show all the wrapper-supplied flags.  But "mpif77 -showme -v" will only
	      show the underlying compiler name and "-v".

       -showme:compile
	      Do not invoke the underlying Fortran 77 compiler.  Instead, show the compiler flags that would be supplied to the  Fortran  77  com-
	      piler.

       -showme:link
	      Do not invoke the underlying Fortran 77 compiler.  Instead, show the linker flags that would be supplied to the Fortran 77 compiler.

       See the man page for your underlying compiler for other options that can be passed through mpif77

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  them-
       selves; they only add in command line flags and invoke the back-end compiler.

   Background
       Open  MPI  is comprised of three software layers: OPAL (Open Portable Access Layer), ORTE (Open Run-Time Environment), and OMPI (Open MPI).
       There are wrapper compilers for each layer; each layer's wrapper only links in the libraries relevant for that layer.   Specifically,  each
       layer provides the following wrapper compilers:

       OPAL
	   opalcc and opalc++

       ORTE
	   ortecc and ortec++

       OMPI
	   mpicc,  mpic++,  mpicxx,  mpiCC  (only  on systems with case-senstive file systems), mpif77, and mpif90.  Note that mpic++, mpicxx, and
	   mpiCC all invoke the same underlying C++ compiler with the same options.  All are provided as compatibility with other MPI  implementa-
	   tions.

       The  Fortran  wrapper  compilers for MPI (mpif77 and mpif90) will be inoperative and will return an error on use if Fortran 77 / Fortran 90
       support was not built into the MPI layer.

   Overview
       mpif77 is a convenience wrappers for the underlying Fortran 77 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.

       mpif77 passes its arguments to the underlying Fortran 77 compiler along with the -I, -L and -l options required by Open MPI programs.

       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
       mpif77.	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 com-
       piler 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 at:

	 https://svn.open-mpi.org/trac/ompi/wiki/compilerwrapper3264

FILES

       The string that the wrapper compilers insert into the command line before invoking the underlying compiler are stored in a text	file  cre-
       ated  by  Open MPI and installed to $pkgdata/mpif77-wrapper-data.txt, where $pkgdata is typically $prefix/share/openmpi, and $prefix is the
       top installation directory of Open MPI.

       It is rarely necessary to edit this file, but it 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 automati-
       cally by Open MPI's "configure" script, or were selected by the user in the CC, CXX, F77, and/or FC environment variables  before  "config-
       ure" 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 sec-
       tion), or by setting selected environment variables of the form "OMPI_value".

       Valid value names are:

       CPPFLAGS
	      Flags added when invoking the preprocessor (C or C++)

       LDFLAGS
	      Flags added when invoking the linker (C, C++, or Fortran)

       LIBS   Libraries added when invoking the linker (C, C++, or Fortran)

       CC     C compiler

       CFLAGS C compiler flags

       CXX    C++ compiler

       CXXFLAGS
	      C++ compiler flags

       F77    Fortran 77 compiler

       FFLAGS Fortran 77 compiler flags

       FC     Fortran 90 compiler

       FCFLAGS
	      Fortran 90 compiler flags

OMPI
								     Open MPI								 mpif77(1)