Hi Dries, I'm jumping late on this thread, but to summarize so far (and correct me if I made a mistake understanding), we have two cases: 1) two non-blocking collective shared FP operations: MPI_File_iread_ordered MPI_File_iread_ordered This will be ordered in the sense that the user will see that the first operations will occur before the second one. 2) mixed collective and independent MPI_File_iread_ordered MPI_File_read_shared Where the choices that you mentioned apply, right? * make that case illegal * make it undefined As you mentioned that since the split collectives leave it as undefined, makes me lean more towards keeping it that way. Thanks, Mohamad On 02/02/2012 04:22 PM, Dries Kimpe wrote:

There might be some use in 'undefined ordering' as opposed to 'illegal' for those application that don't care about the ordering.

Applications that do rely on the ordering can easily use the existing MPI functions to enforce ordering.

So, the way I see it: 2 choices: 1) Say order is undefined in the standard (basically there's a precedent with the split collective versions). 2) Say it is illegal. The user can duplicate the file handle and easily implement their own version of what they need.

(2) is easier for the implementor.