Oh, for the record, mvapich-1.2rc1 was built with ch_gen2, so I built mvapich2-1.6 with: ./configure --with-device=ch3 --enable-sharedlibs=gcc --with-arch=LINUX --without-mpe It seems to have decided on hydra automatically. (Note: I'm not sure why Hydra is, or if that is the correct whatever it is.) -- Jim Leek leek2 at llnl.gov