[Mpi-forum] MPI_Pack and large counts

Rob Latham robl at mcs.anl.gov
Thu Oct 17 08:58:21 CDT 2013

The definition for MPI_Pack looks like this:

int MPI_Pack(const void* inbuf, int incount, MPI_Datatype datatype,
           void *outbuf, int outsize, int *position, MPI_Comm comm)

What happens if incount and datatype describe something larger than an
int?   Looks to me like 'outsize' and 'posistion' will overflow, but
I'm hoping that I'm just missing something. 

Likewise, MPI_Unpack:

int MPI_Unpack(const void* inbuf, int insize, int *position, 
    void *outbuf, int outcount, MPI_Datatype datatype, MPI_Comm comm)


Rob Latham
Mathematics and Computer Science Division
Argonne National Lab, IL USA

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