Introduce common point to depend on MPI:

- detect and use already installed MPI package;
- use MPI_TYPE to determine which MPI package to use.
Support MPICH2 and OpenMPI.

mk/mpi.buildlink3.mk

@@ -0,0 +1,39 @@
+# $NetBSD: mpi.buildlink3.mk,v 1.1 2010/05/16 11:07:39 asau Exp $
+#
+# This Makefile fragment is meant to be included by packages
+# that use any MPI implementation instead of one particular one.
+# The available MPI implementations are "mpich" and "openmpi".
+#
+# === User-settable variables ===
+#
+# MPI_TYPE
+#	This value represents the type of MPI we wish to use on the system.
+#
+#	Possible: mpich, openmpi
+#	Default: mpich
+
+.if !defined(MPI_BUILDLINK3_MK)
+MPI_BUILDLINK3_MK=	# define it
+
+.include "../../mk/bsd.prefs.mk"
+
+# Try to find if we have anything installed already
+.if exists($(LOCALBASE)/bin/mpicc)
+_MPI_PACKAGE!=	$(PKG_INFO) -Q PKGPATH -F $(LOCALBASE)/bin/mpicc
+MPI_TYPE?=	$(_MPI_PACKAGE:T)
+.else
+
+MPI_TYPE?=	mpich	# default to MPICH due to backward compatibility
+.if $(MPI_TYPE) == "mpich"
+_MPI_PACKAGE=	parallel/mpi-ch
+.elif $(MPI_TYPE) == "openmpi"
+_MPI_PACKAGE=	parallel/openmpi
+.else # invalid or unimplemented type
+PKG_FAIL_REASON=	\
+	"${MPI_TYPE} is not an acceptable MPI type for ${PKGNAME}."
+.endif
+.endif
+
+.include "../../$(_MPI_PACKAGE)/buildlink3.mk"
+
+.endif	# MPI_BUILDLINK3_MK