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? -erik -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/
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