NAME

       mpif77 -- Open MPI Fortran 77 wrapper compiler

SYNTAX

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

OPTIONS

       --showme
              This  option  comes  in  several different variants (see below).  None of the variants invokes the
              underlying compiler; they all provide information on how the underlying compiler would  have  been
              invoked had --showme not been used.  The basic --showme option outputs 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
              Output the compiler flags that would have been supplied to the Fortran 77 compiler.

       --showme:link
              Output the linker flags that would have been supplied to the Fortran 77 compiler.

       --showme:command
              Outputs the underlying Fortran 77 compiler command (which may be one or more tokens).

       --showme:incdirs
              Outputs  a  space-delimited  (but  otherwise  undecorated)  list  of  directories that the wrapper
              compiler would have provided to the underlying Fortran 77  compiler  to  indicate  where  relevant
              header files are located.

       --showme:libdirs
              Outputs  a  space-delimited  (but  otherwise  undecorated)  list  of  directories that the wrapper
              compiler would have provided to the underlying linker to indicate  where  relevant  libraries  are
              located.

       --showme:libs
              Outputs  a  space-delimited  (but  otherwise  undecorated)  list of library names that the wrapper
              compiler would have used to link an application.  For example: "mpi open-rte open-pal util".

       --showme:version
              Outputs the version number of Open MPI.

       See the man page for your underlying Fortran 77 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 themselves; 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 implementations.

       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 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 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 created 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 automatically by Open MPI's "configure" script, or were selected by the user
       in the CC, CXX, F77, 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:

       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