Which MPI implementation for MPI-2? ...

Greg Lindahl lindahl at keyresearch.com
Thu Apr 3 04:04:01 EST 2003


On Wed, Apr 02, 2003 at 02:11:20PM -0600, Richard Walsh wrote:

> Somewhat tangentially, but while we are on the subject of one-sided
> communications in MPI-2, am I correct in assuming that this capability 
> is implemented as it is in SHMEM ...

No. It's much more complicated and general. You have to register
windows within which one-sided ops can be used, and there are some
extra calls that you make to make sure operations have completed.

UPC is a much more compact method of expressing one-sided calls, and
unlike shmem, it can benefit from pipelined transfers.

> It would seem to be a requirement for speed and would 
> also seem to require the use of identical binaries on each processor
> (and COMMON or static to place data in a symmetric location).

shmem doesn't require that; you can use a common address (I'm very
punny at 1am) to exchange addresses of malloc-ed data. But with shmem,
you get a free registration of all static & common variables, and the
stack too, as long as you use it in a consistant fashion.

greg

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