Check out the BigMPI project for details on this topic. Some (many?) MPI implementations still have internal limitations that prevent one from sending more than 2 gigabytes using MPI datatypes. You can use the BigMPI tests to identify these.
https://github.com/jeffhammond/BigMPI https://github.com/jeffhammond/BigMPI-paper Jeff On Sunday, June 5, 2016, Alexander Droste < alexander.ra.dro...@googlemail.com> wrote: > Hi Gus, > > thanks a lot for the intro, that helps. > > Best regards, > Alex > > On 05.06.16 18:30, Gustavo Correa wrote: > >> >> On Jun 5, 2016, at 12:03 PM, Alexander Droste wrote: >> >> Hi everyone, >>> >>> I'd like to know what the maximum buffer size >>> for sends/receives is. Besides the count being limited >>> to INT_MAX, how is the max buffer size limited? >>> >>> Best regards, >>> Alex >>> >>> >> >> Hi Alexander >> >> As far as I know, the usual solution to circumvent >> this type of large count problem is to declare an MPI user type to hold >> a large number of MPI native types (say, >> an MPI_Type_Contiguous or MPI_Type_Vector to hold a bunch of floating >> point numbers). >> >> https://www.open-mpi.org/doc/v1.8/man3/MPI_Type_contiguous.3.php >> >> Also, an OMPI pro may correct me for saying foolish things on the list, >> but AFAIK, not all sends/receives are buffered, and the buffer size is >> set by the default eager/rendevous message threshold (or the value that you >> set it to be at runtime with OMPI mca parameters). That buffer size may >> also vary according to the btl (sm,vader, tcp, openib, etc). >> >> Search for "eager" and "rendevous" on the FAQ: >> >> https://www.open-mpi.org/faq/?category=all >> >> >> I hope this helps, >> Gus Correa >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: https://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: >> http://www.open-mpi.org/community/lists/users/2016/06/29371.php >> >> _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: https://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/06/29372.php > -- Jeff Hammond jeff.scie...@gmail.com http://jeffhammond.github.io/
