Thanks Jeff, i could not find anything in the standard that says this is an invalid usage ... so i can only agree this is a bug.
fwiw, example 4.23 is working fine with OpenMPI but that is a different case : with MPI_Gather and friends, recv stuff is irrelevant on non root task. in the case of MPI_Alltoallw and friends, no parameter is ignored. fortunatly, the fix is pretty trivial, so i will make a PR from now Cheers, Gilles On Wed, Jan 13, 2016 at 9:37 AM, Jeff Hammond <jeff.scie...@gmail.com> wrote: > Example 4.23 of MPI 3.1 (it is hardly a new example, but may have a > different number in older versions) demonstrates the use of > (buffer=NULL,count=0,type=MPI_DATATYPE_NULL). While examples in the MPI > standard are not normative text, this is certainly a valid use of MPI. I > can't find a citation where it says explicitly that this is correct, but it > follows logically from other text. > > The MPICH macro MPIR_ERRTEST_USERBUFFER that is used through the code to > test for valid user buffers begins with "if (count > 0..." and thus does > concern itself with the type or buffer pointer when count=0. Furthermore, > this macro is redundantly protected with a count>0 check when used in > MPI_Alltoallw (and other collectives). > > Best, > > Jeff > > > On Tue, Jan 12, 2016 at 4:18 PM, Gilles Gouaillardet <gil...@rist.or.jp> > wrote: >> >> Hi Jim, >> >> can you please confirm my understanding is correct : >> >> - OpenMPI does *not* accept MPI_DATATYPE_NULL as an input of MPI_Alltoallw >> - mpich does accept MPI_DATATYPE_NULL as an input of MPI_Alltoallw *if* >> the corresponding count *is* zero >> - mpich does *not* accept MPI_DATATYPE_NULL as an input of MPI_Alltoallw >> *if* the corresponding count is *not* zero >> >> So you are considering as a bug the fact OpenMPI does not accept >> MPI_DATATYPE_NULL *with* a zero count. >> >> am i correct ? >> >> Cheers, >> >> Gilles >> >> >> On 1/13/2016 8:27 AM, Jim Edwards wrote: >> >> Hi, >> >> I am using OpenMPI-1.8.3 built with gcc 4.8.3 >> and I am using an MPI_Alltoallw call to perform >> an all to some (or some to all) communication. >> >> In the case in which my task is not sending (or receiving) any data I set >> the >> datatype for that send or recv buffer to MPI_DATATYPE_NULL - this >> works fine with other mpi libraries but fails in openmpi. If I set >> the datatype to something else say MPI_CHAR - it works fine. I think >> that this is a bug in open-mpi - would you agree? >> >> >> >> >> -- >> Jim Edwards >> >> CESM Software Engineer >> National Center for Atmospheric Research >> Boulder, CO >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2016/01/28249.php >> >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2016/01/28250.php > > > > > -- > Jeff Hammond > jeff.scie...@gmail.com > http://jeffhammond.github.io/ > > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/01/28251.php
