/*D
    mpif90 - Compiles and links MPI programs written in Fortran 90

    Description:
    This command can be used to compile and link MPI programs written in
    Fortran.  It provides the options and any special libraries that are
    needed to compile and link MPI programs.  

    It is important to use this command, particularly when linking programs, 
    as it provides the necessary libraries.  

    Command line arguments:
+  -show      - Show the commands that would be used without
             runnning them
.  -help      - Give short help
.  -f90=name   - Use compiler 'name' instead of the default choice.  Use
                this only if the compiler is compatible with the MPICH
                library (see below)
.  -config=name - Load a configuration file for a particular compiler.
                This allows a single 'mpif90' command to be used with 
                multiple compilers.
.  -compile_info - Show the steps for compiling a program.  This option
                can be used to see what options and include paths are
		used by mpif90.
.  -link_info - Show the steps for linking a program.  This optoin 
                can be used to see what options and libraries are used by
                mpif90.
.  -profile=name - Use the MPI profiling given by name.  See below for
                details
.  -mpe=name  - Use an MPE profiling library.  The behavior is similar
                to using '-profile=mpe_name.conf'.
.  -echo      - Show exactly what this program is doing.
                This option should normally not be used.
-  others     - are passed to the compiler or linker.  For example, '-c'
                causes files to be compiled, '-g' selects compilation with
                debugging on most systems, and '-o name' causes linking 
                with the output executable given the name 'name'.

    Environment Variables:
    The environment variables 'MPICH_F90' may be used
    to select different Fortran compiler and linker.  Note that since
    MPICH is built with a particular C and Fortran compiler, change the
    compilers used can cause problems.  Use this only if you could intermix
    code compiled with the different compilers.

    Compatible Compilers:
    The MPI library may be used with any compiler that uses the same 
    lengths for basic data objects (such as 'long double') and that 
    uses compatible run-time libraries.  On many systems, the various
    compilers are compatible and may be used interchangably.  There are 
    exceptions; if you use the 'MPICH_F90' environment variable or the 
    '-f90=name' command-line argument to override the choice of compiler 
    and encounter problems, try reconfiguring MPICH2 with the new compiler 
    and installing MPICH2 in a separate location.  See the installation manual 
    for more details.

    Examples:
To compile a single file 'foo.f', use
.vb
   mpif90 -c foo.f 
.ve

To link the output and make an executable, use
.vb
   mpif90 -o foo foo.o
.ve
Combining compilation and linking in a single command
.vb
   mpif90 -o foo foo.f
.ve
is a convenient way to build simple programs.

 Selecting a Profiling Library:
 The '-profile=name' argument allows you to specify an MPI profiling
 library to be used.  'name' can have two forms\:

.n A library in the same directory as the MPI library 
.n The name of a profile configuration file
.n
 If 'name' is a library, then this library is included before the MPI 
 library.  This allows the simple use of libraries that make use of the
 MPI profiling interface and that are installed in the same directory as 
 the MPI library.

 If 'name.conf' is the name of a file in the sysconfdir directory, then this
 is read and may define the following variables\:
+ PROFILE_PRELIB - Libraries (and paths) to include before the MPI library
. PROFILE_POSTLIB - Libraries to include after the MPI library
- PROFILE_INCPATHS - C preprocessor arguments for any include files
 For example, to add '/usr/local/myprof/include' to the include path and
 the library 'libmyprof.a' in '/usr/local/myprof/lib' to the link step, 
 you could create the file 'myprof.conf' with the lines

.vb
    PROFILE_PRELIB="-L/usr/local/myprof/lib -lmyprof"
    PROFILE_INCPATHS="-I/usr/local/myprof/include"
.ve
 and place it in the sysconfdir directory (this directory is set at
 configure time when MPICH is built).  Then using the command-line 
 argument '-profile=myprof' will cause these 
 definitions to be added to the relevant compile commands.

.seealso: mpicc, mpicxx, mpif90, mpiexec
D*/
