[Mpi-22] MPI_INIT assertions

[Dries Kimpe]

* Terry Jones <trj_at_[hidden]> [2008-05-13 15:19:07]:

> You can also imagine other possibilities to provide helpful context. For 
> instance, perhaps the user could provide Assertions that would help MPI IO 
> with read-ahead prefetching or write-behind, or even meta-data operations 
> (e.g., later I will be creating one file per MPI task).

Things like read-ahead or write-behind clearly shouldn't be assertions but
hints. (And, probably 'one file per MPI task' too -- if this is still going to
be needed in 2 years)

MPI already has hints that can capture some of the things mentioned
above. 

access_style: (read_once, write_once, read_mostly, write_mostly, sequential,
reverse_sequential, and random) 
    sequential -> this can easily be used to turn on read-ahead 
                  IF THE MPI LIBRARY decides this is useful

Assertions are bad -- they break compatibility -- and should only be
tolerated if they provide real benefits and if the same cannot be obtained
through existing mechanisms (hints, ...). 

In the examples mentioned, this is not the case.

   Dries




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