I think the question is about passing NULL as a buffer pointer. E.g.,
MPI_Send(NULL, 0, mytype,dst, tag,comm);
vs
MPI_Send(&dummy,0,mytype,dst,tag,comm);
George Bosilca wrote:
The only restriction the MPI standard impose on the sendcounts and
recvcounts arrays is that the values be non-negative, so zero is a
legal value.
I don't really understand your second question. Where do you want to
use NULL ? In general NULL is not accepted in MPI as an argument for
any function ...
On Feb 23, 2009, at 02:55 , jody wrote:
I have an application in which various processes create different
amounts of data (including no data at all).
I have found that MPI_Scatterv and MPI_Gatherv do work with arrays
sendcounts or receivecounts containing zeros.
Since i didn't find the case of 0 sizes in the descriptions
of these functions in the MPI reference, i wondered whether
the use of zeroes is legal or if i was simply lucky that it worked.
An other point: currently i use 1-sized buffers in the
case of a 0-sized data transfer.
Now if 0-sized data transfer is legal, would it be ok to
pass NULL for the buffer?
