[Mpi-forum] MPI_Type_size question
ftillier at microsoft.com
Fri Jun 18 11:55:08 CDT 2010
Looking at putting together the MPI_Count ticket, I ran across the following issue and was hoping to get some guidance. Take the following code, using the current int counts, and assume sizeof(int) == 4, sizeof(MPI_DOUBLE) == 8:
MPI_Type_contiguous( 1048576, MPI_DOUBLE, &myType );
MPI_Type_size( myType, &size );
Should MPI_Type_size return an error, due to overflow? Does size get set to MPI_UNDEFINED and the call succeeds?
Similar issues exist for MPI_Pack with the outsize and position parameters, MPI_Unpack with the insize and position parameters, and MPI_Pack_size with the size parameter.
Lastly, it is my belief that these parameters should really be of type MPI_Aint, but changing this would break backward compatibility. They cannot be of type MPI_Count, since overflow can occur if MPI_Count is defined as a C int. How should the standard handle this?
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