[Nek5000-users] Parallel speedup on supercomputer Tianhe-2

[nek5000-users at lists.mcs.anl.gov]

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: <nek5000-users-bounces at lists.mcs.anl.gov> on behalf of <nek5000-users at lists.mcs.anl.gov>
Reply-To: <nek5000-users at lists.mcs.anl.gov>
Date: Monday, December 5, 2016 at 6:12 AM
To: <nek5000-users at lists.mcs.anl.gov>
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

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