version(s) 1.54.0-r1, 1.52.0-r{6,7}, 1.53.0-r1 use sys-cluster/mpich2. Please migrate to sys-cluster/mpich as upstream changed the package name. Thanks,
Newer ebuilds utilize virtual/mpi, let's do this with older ones + 03 Jun 2015; Sergey Popov <pinkbyte@gentoo.org> boost-1.52.0-r7.ebuild, + boost-1.53.0-r1.ebuild, boost-1.54.0-r1.ebuild: + Transfer older Boost ebuilds to virtual/mpi to resolve bug #547212