On Mon, 31 Oct 2005 20:33:06 -0700, Jeff Squyres <jsquy...@open-mpi.org> wrote:

On Oct 28, 2005, at 3:08 PM, Jeff Squyres wrote:

1. I'm concerned about the MPI_Reduce error -- that one shouldn't be
happening at all.  We have table lookups for the MPI_Op/MPI_Datatype
combinations that are supposed to work; the fact that you're getting
this error means that HPCC is using a combination that falls outside
the pairs that are defined in the MPI standard.  Sigh.  But it's HPCC,
so we should support it ;-).

I'll eat crow on this one -- double checking the HPCC code, it looks
like they are doing reductions on MPI_LONG_LONG_INT, which is perfectly
legal (MPI_LONG_LONG_INT is not specifically mentioned in the
collectives section in MPI-1, but it's one of the "optional" C
datatypes, and falls within the spirit of the definition of "C integer"
in the collectives section).  Despite having implementations for all
the relevant reductions in Open MPI, I forgot to add MPI_LONG_LONG_INT
into some MPI_Op cross-reference datatype tables, so MPI_Reduce didn't
think that those combinations were valid.  Doh!

I just committed the fix for this on the trunk; everyone's asleep right
now, but I'll get a review of this code and get it committed on the 1.0
branch tomorrow.  :-)

My coworkers and I joke that we were hired for our knack at breaking software; OpenMPI will likely suffer a fair amount of our attention. You have to do a lot of hammerin' to turn iron into steel, but the result is worth it. If only I knew enough about implementing an MPI to be helpful in solving the problems, rather than just finding them...

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