On 24 Jul 2015, at 19:42, Erik Schnetter <[email protected]> wrote:
> On Fri, Jul 24, 2015 at 1:39 PM, Ian Hinder <[email protected]> wrote: > > On 24 Jul 2015, at 19:15, Erik Schnetter <[email protected]> wrote: > >> On Fri, Jul 24, 2015 at 11:57 AM, Ian Hinder <[email protected]> wrote: >> >> On 8 Jul 2015, at 16:53, Ian Hinder <[email protected]> wrote: >> >>> >>> On 8 Jul 2015, at 15:14, Erik Schnetter <[email protected]> wrote: >>> >>>> I added a second benchmark, using a Thornburg04 patch system, 8th order >>>> finite differencing, and 4th order patch interpolation. The results are >>>> >>>> original: 8.53935e-06 sec >>>> rewrite: 8.55188e-06 sec >>>> >>>> this time with 1 thread per MPI process, since that was most efficient in >>>> both cases. Most of the time is spent in inter-patch interpolation, which >>>> is much more expensive than in a "regular" case since this benchmark is >>>> run on a single node and hence with very small grids. >>>> >>>> With these numbers under our belt, can we merge the rewrite branch? >>> >>> The "jacobian" benchmark that I gave you was still a pure kernel benchmark, >>> involving no interpatch interpolation. It just measured the speed of the >>> RHSs when Jacobians were included. I would also not use a single-threaded >>> benchmark with very small grid sizes; this might have been fastest in this >>> artificial case, but in practice I don't think we would use that >>> configuration. The benchmark you have now run seems to be more of a >>> "complete system" benchmark, which is useful, but different. >>> >>> I think it is important that the kernel itself has not gotten slower, even >>> if the kernel is not currently a major contributor to runtime. We >>> specifically split out the advection derivatives because they made the code >>> with 8th order and Jacobians a fair bit slower. I would just like to see >>> that this is not still the case with the new version, which has changed the >>> way this is handled. >> >> I have now run my benchmarks on both the original and the rewritten >> McLachlan. I seem to find that the ML_BSSN_* functions in >> Evolve/CallEvol/CCTK_EVOL/CallFunction/thorns, excluding the constraint >> calculations, are between 11% and 15% slower with the rewrite branch, >> depending on the details of the evolution. See attached plot. This is on >> Datura with quite old CPUs (Intel Xeon CPU X5650 2.67GHz). >> >> What exactly do you measure -- which bins or routines? Does this involve >> communication? Are you using thorn Dissipation? > > > I take all the timers in Evolve/CallEvol/CCTK_EVOL/CallFunction/thorns that > start with ML_BSSN_ and eliminate the ones containing "constraints" (case > insensitive). This is running on two processes, one node, 6 threads per > node. Threads are correctly bound to cores. There is ghostzone exchange > between the processes, so yes, there is communication in the > ML_BSSN_SelectBCs SYNC calls, but it is node-local. > > Can you include thorn Dissipation in the "before" case, and use McLachlan's > dissipation in the "after" case? There is no dissipation in either case. The output data is in http://git.barrywardell.net/?p=McLachlanBenchmarks.git;h=refs/runs/orig/20150724-174334 http://git.barrywardell.net/?p=McLachlanBenchmarks.git;h=refs/runs/rewrite/20150724-170542 including the parameter files. Actually, what I said before was wrong; the timers I am using are under "thorns", not "syncs", so even the node-local communication should not be counted. -- Ian Hinder http://members.aei.mpg.de/ianhin
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