On Mar 10 2014, Bill Long wrote:

I agree with Steve. In these sorts of calls the actual size of the array is available from somewhere else - either another argument or information in the communicator. This is the common situation when calling C.

I don't, but only in the slant of my comment. I would say that assumed size arrays should be used ONLY when calling facilities that use a C-like interface (which obviously includes MPI 2.2). While it would be nice to say that programs should always use the new MPI 3.0 interfaces, currently their availability is patchy and unreliable. So the book over-simplifies, but I agree with its recommendation for pure Fortran code. There are other reasons to use assumed size, but they are mostly pretty arcane. Regards, Nick.