[mpi3-coll] array parameters in nonblocking collectives

[Torsten Hoefler]

On Sat, Aug 01, 2009 at 10:54:20AM -0500, Rajeev Thakur wrote:
> Torsten,
>         What does libNBC do in this case?
hah, I forgot to say that :). LibNBC generates a collective schedule
that encodes all steps in the init (MPI_I*) call. Thus, it simply
copies the arguments in the schedule.

This technique allows for tree-like (or butterfly) methods to be used in
vector variants reducing the needed space per process to O(log(P)).
However, they can become arbitrarily slow (log(P) large messages can be
serialized at one process) with an adversarial vector distribution.
Thus, I implemented the less scalable method that needs O(P) space per
process (it'll eliminate all zeros) which can not loose parallelism or
degenerate.

Best,
  Torsten

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Torsten Hoefler       | Postdoctoral Fellow
Open Systems Lab      | Indiana University    
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