[Mpi-22] MPI_INIT assertions

[Ashley Pittman]

On Thu, 2008-05-15 at 17:44 -0400, Richard Treumann wrote:
> 
> The MPI_NO_SEND_CANCEL is only useful for cases where libmpi must
> devote extra memory, longer code paths or extra space in message
> headers across an entire run just to have the information it needs to
> do MPI_CANCEL correctly is somebody happens to call it. If a
> particular MPI implementation does not incur extra costs to be ready
> for a potential MPI_CANCEL then the implementation will ignore this
> assertion.

To me I see little benefit in offering MPI_NO_SEND_CANCEL as a hint, all
that does is say to the library that a cancel is unlikely to happen and
we all know that anyway.  As a cancel is still possible I see no
opportunity for optimisation of any kind making itself possible, all the
extra space in headers and longer code paths would still be needed
anyway.

As an assertion it would offer some scope for library writers to make
simplifications leading to better performance, as a hint I can't see how
it would change anything.

Ashley,