[Mpi-22] mpi-22 Digest, Vol 2, Issue 7

[Richard Treumann]

Dick Treumann  -  MPI Team/TCEM
IBM Systems & Technology Group
Dept 0lva / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
Tele (845) 433-7846         Fax (845) 433-8363

mpi-22-bounces_at_[hidden] wrote on 04/24/2008 11:33:42 AM:

> Hi,
>
> Note that this is an argument for making the assertions optional: those
> who don't care don't have to use them. Those who care should use them
> correctly or else. As usual.
>
> Best regards.
>
> Alexander
>

Hi Alexander

The assertions are optional in this proposal.  If this is added to the MPI
standard the minimal impacts (day one impacts) are:

==
To application writers (none) - MPI_INIT and MPI_INIT_THREAD still work.
MPI_INIT_THREAD_xxx can be
passed 0 (zero) as the assertions bit vector.

To MPI Implementors (small) - subroutine MPI_INIT_THREAD_xxx can be a clone
of MPI_INIT_THREAD under the covers. If the Forum decides the query
function is for asking what assertions are being honored, the
implementation can just return "none" to every query. If there is also a
query for what assertions have been made then there are a few more lines of
code the implementor must write to preserve the value so it can be
returned(maybe 10 lines)

Writers of opaque libraries (small) - call the query function at library
init time and if any assertions are found, issue an error message and kill
the job. This is awkward for a library that wants to support every MPI
whether it has implemented the new query function or not.
==

As MPI implementations begin to take advantage of assertions there is more
work for the MPI implementor and the library author must begin to think
about whether his customer will be upset if the library simply outlaws all
assertions.

The library author will never be wrong if he simply forbids assertions
forever. If they become valuable he will feel the pressure to work it out.

The MPI implementor will never be wrong if he adds the API but simply
ignores assertions forever. If they become valuable he will feel the
pressure to honor some at least.





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