Hello, virtual/mpi-2.0-r1 contains a typo in dependencies, due to which mvapich2 is ignored: mvampich2 insted of mvapich2. Patch is attached.
Created attachment 325114 [details, diff] mpi-2.0-r1.ebuild.patch
+ 27 Sep 2012; Kacper Kowalik <xarthisius@gentoo.org> mpi-2.0-r1.ebuild: + Fix typo in RDEPEND wrt #436394 by Andrew Savchenko <bircoph@gmail.com>