The option --with-trillium is required to get xmpi to work with lam-mpi. This should be quite easy to implement in all present versions of the ebuilds by simply adding a "xmpi" USE flag and correcting the ebuilds.
I agree that this could be useful.
Given that LAM-MPI is deprecated in favor of OpenMPI and that xmpi has never been officially "stable" (I tried the last iteration of xmpi with LAM-MPi 7.1.1, last that I know of). Don't know if anyone will actually bother to add/maintain this...
OK.
As per the comment in bug #141152: Okay, so I still want the Trillium thing, can't hurt to have the option :)
Fixed in CVS, thanks.