More and more systems, particularly clusters, come with multiple compilers. In many cases, you can build mpich using just one of these compilers and then allow users to use their favorite compiler when building their code. In many cases, no extra steps are needed. Users can simply use the command-line argument -cc or the environment variable MPICH_CC to specify a different compiler.
Unfortunately, this won't always work.
For example, in some cases, different libraries may be needed by different
compilers when linking programs. Some compilers may need different options to
support ANSI/ISO C. In particular, support for the longer datatypes such as
long long and long double may rely on runtime library support
routines that are specific to each compiler.
To handle all of these cases,
For C and C++, you can create a file with the name
mpicc-<compilename>.conf,
e.g., mpicc-gcc.conf or mpicc-pgcc.conf, that contains any
specifications
that are needed by the mpicc command. mpicxx uses
mpicxx-<name>.conf. Currently, these files must be created by hand,
starting from the file mpichlib.conf that is created in the
mpich/util directory by the mpich configure. The simplest way
to create each file is to use configure:
setenv CC cc
configure --prefix=/usr/local/mpich-1.2.6
make
make install
cp util/mpichlib.conf /usr/local/mpich-1.2.6/etc/mpicc-cc.conf
setenv CC gcc
configure --prefix=/usr/local/mpich-1.2.6
make
cp util/mpichlib.conf /usr/local/mpich-1.2.6/etc/mpicc-gcc.conf
In this example, the default value of sysconfdir, $prefix/etc,
is used.
For example, if mpich was built with cc as the compiler but a user
wanted to use gcc instead, either the commands
MPICH_CC=gcc
mpicc ...
or
mpicc -config=gcc ...would case mpicc to load mpich-gcc.conf and use the appropriate definitions.