But the advice to users that follows it specifically describes what happens when an array, rather than a scalar, is passed, and this advice appears at the time of the original definition, in MPI 2.0. From that, it is clear that the *intent* of the Forum was to permit arrays to be passed to MPI_SIZEOF; otherwise, this text would never have been written. So I'll agree that the interface hasn't changed - it has *always* permitted an array as an argument. Bill William Gropp Director, Parallel Computing Institute Thomas M. Siebel Chair in Computer Science University of Illinois Urbana-Champaign On Jun 13, 2014, at 10:32 AM, Rolf Rabenseifner wrote:

Back to MPI_SIZEOF in mpif.h:

A few clarifications:

1) The interface of Argument x was not changed between MPI-2.0, 2.1, 2.2 and MPI-3.0: It is always "<type> x" for mpif.h, i.e., without a dimension.