Hi Ehsan,

 

The optimization is likely to be problem and architecture dependent. Normally, Nektar++ automatically produce an optimization file *.opt. You should be able to see it. If you want to examine the influence of optimization on computational time, I guess you can manually set IMPTYPE to “NoCollection”.

 

Best,

Jacques

 

From: nektar-users-bounces@imperial.ac.uk <nektar-users-bounces@imperial.ac.uk> On Behalf Of Ehsan Asgari
Sent: Wednesday, August 9, 2023 3:23 PM
To: Isaac Rosin <isaac.rosin1@ucalgary.ca>
Cc: Maziyar Hassanpour <maziyar.hassanpour@ucalgary.ca>; nektar-users@imperial.ac.uk
Subject: Re: [Nektar-users] Optimisation Issues

 

Hi Isaac

 

I am doing a simulation on a similar configuration, a wall-mounted cylinder with Re=750. It's actually the first time I read about the optimization technique to speed up the run.

Could you let me know if it had a significant influence?

 

Kind regards

syavash

 

 

On Wed, Aug 9, 2023 at 4:38 AM Isaac Rosin <isaac.rosin1@ucalgary.ca> wrote:

This email from isaac.rosin1@ucalgary.ca originates from outside Imperial. Do not click on links and attachments unless you recognise the sender. If you trust the sender, add them to your safe senders list to disable email stamping for this address.

 

Hello Nektar Community,

 

I am running a full 3D DNS simulation at Re=400 of a flow past a rectangular prism using the incompressible solver. This flow is laminar but 3D effects are present. I am using a structured mesh generated using gmsh with a p order of 4 which comes to roughly 2.6 million degrees of freedom. A colleague is able to run a similar but slightly more complex DNS simulation at Re=3900 on 1/8 the number of processors and he still obtains results much faster. All signs indicate I should be able to use far fewer resources than I currently am, but neither of us can figure out how to optimise further than I already have. I followed the optimisation section of the Nektar user guide, tweaked my mesh several times, changed the time step size, etc., but all of these adjustments showed marginal improvements at best. I would be very grateful if anyone has any suggestions. I am providing my case files here: https://drive.google.com/drive/folders/1iT0GvZgE0MyfmjNe1GYMlAKJp-8fh57X?usp=sharing the slurm file called P4.sh has the script I normally use on clusters.

 

I look forward to hearing from you!

 

All the best,

Isaac

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