What's your problem size (number of elements and polynomial order)? Let's assume t_MPI << t (this holds if your problem size is reasonably large). Even in this limit you don't get a linear intra-node speedup simply because Nek5000 is not purely compute bound and the cumulative memory bandwidth is saturated with N cores (N < total number of cores). Cheers, Stefan From: <[email protected]> on behalf of <[email protected]> Reply-To: <[email protected]> Date: Monday, December 5, 2016 at 6:12 AM To: <[email protected]> Subject: [Nek5000-users] Parallel speedup on supercomputer Tianhe-2 Dear Neks, I'm using Nek5000 to simulate turbulent Rayleigh-Benard convection, which is governed by the coupled Navier-Stokes equations and convective heat equation. I'm running the code on a supercomputer, Tianhe-2, located in Guangzhou, China. Each computer node in Tianhe-2 has 24 cores (2 Xeon E5 12-core CPUs) and 64GB memory. I find the speedup curve is not linear on a single node. For example, a 24-task job is only 8 times faster than the serial one. However, the performance with an increasing number of nodes is quite good. I don't know whether there is any parameter in nek500 that I can change in order to improve the speedup performance of the individual nodes. Thanks in advance! Best regards, Wei XU ---------- Wei XU Ph.D. Candidate Nano Science and Technology Program The Hong Kong University of Science and Technology _______________________________________________ Nek5000-users mailing list [email protected] https://lists.mcs.anl.gov/mailman/listinfo/nek5000-users