I added the sqrt() change, which is the most important change, and then did a 2nd commit with the whitespace cleanup. The sqrt change will likely be in 1.7.5. I credited you in the commit log; you'll likely also get credited in NEWS.
Thank you for the patch!
On Dec 19, 2013, at 9:37 AM, Andreas Schäfer <gentryx_at_[hidden]> wrote:
> Dear all,
> please find attached a (trivial) patch to MPI_Dims_create(). When
> computing the prime factors of nnodes, it is sufficient to check for
> primes less or equal to sqrt(nnodes).
> This was not so much of a problem in the past, but now that Tier 0
> systems are capable of running O(10^6) MPI processes, the difference
> in execution time is on the order of seconds (e.g. 8.86s vs. 0.04s on
> my notebook, with nnproc = 10^6).
> PS: oh, and the patch removes some trailing whitespace. Yuck. :-)
> Andreas Schäfer
> HPC and Grid Computing
> Chair of Computer Science 3
> Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
> +49 9131 85-27910
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