mpi: add self.spec.[mpicc|mpicxx|mpifc|mpif77] to avoid hardcoding MPI wrappers names

lib/spack/docs/packaging_guide.rst

@@ -1831,6 +1831,23 @@ successfully find ``libdwarf.h`` and ``libdwarf.so``, without the
 packager having to provide ``--with-libdwarf=/path/to/libdwarf`` on
 the command line.
 
+Message Parsing Interface (MPI)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It is common for high performance computing software/packages to use ``MPI``.
+As a result of conretization, a given package can be built using different
+implementations of MPI such as ``Openmpi``, ``MPICH`` or ``IntelMPI``.
+In some scenarios to configure a package one have to provide it with appropriate MPI
+compiler wrappers such as ``mpicc``, ``mpic++``.
+However different implementations of ``MPI`` may have different names for those
+wrappers.  In order to make package's ``install()`` method indifferent to the
+choice ``MPI`` implementation, each package which implements ``MPI`` sets up
+``self.spec.mpicc``, ``self.spec.mpicxx``, ``self.spec.mpifc`` and ``self.spec.mpif77``
+to point to ``C``, ``C++``, ``Fortran 90`` and ``Fortran 77`` ``MPI`` wrappers.
+Package developers are advised to use these variables, for example ``self.spec['mpi'].mpicc``
+instead of hard-coding ``join_path(self.spec['mpi'].prefix.bin, 'mpicc')`` for
+the reasons outlined above.
+
+
 Forking ``install()``
 ~~~~~~~~~~~~~~~~~~~~~
 

var/spack/repos/builtin/packages/mpich/package.py

@@ -54,6 +54,11 @@ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.set('MPICH_F90', spack_fc)
         spack_env.set('MPICH_FC', spack_fc)
 
+        self.spec.mpicc  = join_path(self.prefix.bin, 'mpicc')
+        self.spec.mpicxx = join_path(self.prefix.bin, 'mpic++')
+        self.spec.mpifc  = join_path(self.prefix.bin, 'mpif90')
+        self.spec.mpif77 = join_path(self.prefix.bin, 'mpif77')
+
     def setup_dependent_package(self, module, dep_spec):
         """For dependencies, make mpicc's use spack wrapper."""
         # FIXME : is this necessary ? Shouldn't this be part of a contract with MPI providers?

var/spack/repos/builtin/packages/openmpi/package.py

@@ -45,6 +45,11 @@ def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
         spack_env.set('OMPI_FC', spack_fc)
         spack_env.set('OMPI_F77', spack_f77)
 
+        self.spec.mpicc  = join_path(self.prefix.bin, 'mpicc')
+        self.spec.mpicxx = join_path(self.prefix.bin, 'mpic++')
+        self.spec.mpifc  = join_path(self.prefix.bin, 'mpif90')
+        self.spec.mpif77 = join_path(self.prefix.bin, 'mpif77')
+
 
     def install(self, spec, prefix):
         config_args = ["--prefix=%s" % prefix,