Cool. See the other thread where I'm wondering if we shouldn't just pre-generate all the primes, hard-code them into a table, and be done with this issue.
On Feb 10, 2014, at 5:19 PM, Andreas Schäfer <gent...@gmx.de> wrote: > Jeff- > > I've seen that you've reverted the patch as it was faulty. Sorry about > that! I've attached a new patch, which applies against the current > trunk. The problem with the last patch was that it didn't catch a > special case: of all prime factors of n, there may be at most one > larger than sqrt(n). The old patch assumed that there was none. I've > included a comment in the source code so that this becomes clear for > later readers. > > The attached patch is more complicated than the original code, as we > now need to calculate the prime numbers and the number of their > occurrences in the integer factorization simultaneously. We can't > split both (as in the trunk) anymore, as the last prime might only be > discovered during the original getfactors(). > > I've tested this code back to back with the original code with > 1...10000 nodes and 1...6 dimensions, just to be on the sure side this > time. > > Best > -Andreas > > > On 19:32 Mon 03 Feb , Jeff Squyres (jsquyres) wrote: >> Andreas -- >> >> 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 <gent...@gmx.de> 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). >>> >>> Best >>> -Andreas >>> >>> 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 >>> PGP/GPG key via keyserver >>> http://www.libgeodecomp.org >>> ========================================================== >>> >>> (\___/) >>> (+'.'+) >>> (")_(") >>> This is Bunny. Copy and paste Bunny into your >>> signature to help him gain world domination! >>> <mpi_dims_create_speedup.patch>_______________________________________________ >>> devel mailing list >>> de...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/devel >> >> >> -- >> Jeff Squyres >> jsquy...@cisco.com >> For corporate legal information go to: >> http://www.cisco.com/web/about/doing_business/legal/cri/ >> >> _______________________________________________ >> devel mailing list >> de...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/devel > > -- > ========================================================== > Andreas Schäfer > HPC and Grid Computing > Chair of Computer Science 3 > Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany > +49 9131 85-27910 > PGP/GPG key via keyserver > http://www.libgeodecomp.org > ========================================================== > > (\___/) > (+'.'+) > (")_(") > This is Bunny. Copy and paste Bunny into your > signature to help him gain world domination! > <mpi_dims_create_speedup.patch>_______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
