On 11/19/2015 10:38 AM, Jen B wrote:
Thank you for your quick response, Jeff!
I was wondering the values for "short" and "large" message sizes, they've been used throughout the paper but not mentioned explicitly. Do you happen to know if these values are explicitly mentioned somewhere?
Also, if I get the last algorithm name used for the MPI collective routine, is there a way I can for sure tell which algorithm is being used? For example, is there any name formatting convention that is used.
Sorry for so many questions. Any help with any of these questions will be greatly appreciated!
'short' and 'large' refers to those messages smaller than /greater than the EAGER_THRESHOLD. https://www.alcf.anl.gov/user-guides/tuning-mpi-bgq has some resources and documentation. The "application red book" is probably what you want. Here's a relevant quote: By default, the MPI send operations use the rendezvous protocol, instead of the eager protocol, for messages larger than 2048 bytes. (there are also immediate and short messages) ==rob
Thank you! Jen
On Wed, Nov 18, 2015 at 6:06 PM, Jeff Hammond <[email protected] <mailto:[email protected]>> wrote:
A binary tree is the implementation of last resort.
See these papers for details of the MPI collective implementations on Blue Gene: - http://dx.doi.org/10.1177/1094342014552086 - http://dx.doi.org/10.1109/HOTI.2009.12 (this is not an inclusive list)
http://lists.mpich.org/pipermail/discuss/2015-March/003754.html has some related info.
Jeff
On Wed, Nov 18, 2015 at 12:53 PM, Jen B <[email protected] <mailto:[email protected]>> wrote:
Hello,
I have a couple of questions about BG/Q collectives and would appreciate any help. I was wondering if Do IBM BG/Q MPI collectives use binomial tree? Once I find the name of the algorithm used by the MPI collective routine using MPIX_Get_last_algorithm_name, is there a quick reference or guide to check how it is implemented?
Thanks! Jen
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-- Jeff Hammond [email protected] <mailto:[email protected]> http://jeffhammond.github.io/
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-- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss