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From: Lisandro Dalcin (dalcinl_at_[hidden])
Date: 2006-09-26 16:02:21

I'am developing mpi4py, a MPI port for Python. I've wrote many
unittest scripts for my wrappers, which also pretend to test MPI

Below, I list some issues I've found when building my wrappers with
Open MPI 1.1.1. Please let me know your opinions.

 - MPI_Group_translate_ranks(group1, n, ranks1, group2, ranks2) fails
   (with MPI_ERR_GROUP) if n != size(group1). Regarding the standard,
   I understand this routine should whork for any value of n, if
   ranks1 contains values (even if some are duplicated) in a valid
   range according to size(group1).

 - MPI_Info_get_nthkey(INFO, 0, key) does not fail when INFO is
   empty, ie, when MPI_Info_get_nkeys(info, &nkeys) returns nkeys==0.

 - Usage of MPI_IN_PLACE is broken in some collectives, below the
   reasons I've found:

   + MPI_Gather: with sendbuf=MPI_IN_PLACE, sendcount is not ignored.
   + MPI_Scatter: with recvbuf=MPI_IN_PLACE, recvcount is not ignored.
   + MPI_Allgather: with sendbuf=MPI_IN_PLACE, sendcount is not ignored.

   The standard says that [send|recv]count and [send|recv]type are
   ignored. I've not tested vector variants, perhaps they suffer the
   same problem.

 - Some extended collective communications failed (not by raising
   errors, but instead aborting tracing to stdout) when using
   intercommunicators. Sometimes, the problems appeared when
   size(local_group) != size(remote_group). However, MPI_Barrier and
   MPI_Bcast worked well. I still could not get the reasons for those
   failures. I've found a similar problem in MPICH2 when configured
   with error-cheking enabled (they had a bug in some error-cheking
   macros, I reported this issue and next they told me I was right).

Lisandro Dalcín
Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
PTLC - Güemes 3450, (3000) Santa Fe, Argentina
Tel/Fax: +54-(0)342-451.1594