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.