On Jul 21, 2014, at 11:25 AM, Jed Brown <[email protected]> wrote: > Barry Smith <[email protected]> writes: > >>> but it would be nice to have a common way to >>> address other viewer implementations. >> >> What do you mean by this? > > That we should be able to tell the VTK viewer to use MPI-IO in the same > way we tell the Binary viewer or any other viewer capable of using MPI-IO.
Yes the correct PetscViewerFormat is limited in that there is only one supported at a time. We could go the horrible bit oring of options or we could collect multiple options instead of just one. > >>>>> PETSc devs, do you suppose MPI-IO support is stable enough that we could >>>>> make this a default? >>>> >>>> It is not so much a question of stability, it is more a question >>>> of (I believe) MPI IO is just loads slower for what might normal >>>> PETSc users use, it only pays off for large numbers of nodes. >>> >>> Do we have current data demonstrating that this is still the case? It's >>> really a failure of the implementations if they can't fall back to the >>> dumbest mechanism when it's faster. >> >> Oh, actually I just remembered what always drove me crazy with MPI >> IO is that it saves it in native format meaning it is not portable >> to all systems (which have different endian). Portability before >> performance :-) > > Uh, MPI_Pack_external and MPI_Unpack_external? Ok, so maybe the finally implemented them. We don’t use this BTW because Rajev told me (a long time ago) that MPICH doesn’t support it. Barry
