Re: [Nektar-users] Optimisation Issues

9 Aug 2023

      Thank you Jacques

Here is the .opt file generated:

<NEKTAR>
...
<COLLECTIONS>
        <OPERATOR TYPE="BwdTrans">
            <ELEMENT TYPE="H" ORDER="*" IMPTYPE="SumFac" />
        </OPERATOR>
        <OPERATOR TYPE="Helmholtz">
            <ELEMENT TYPE="H" ORDER="*" IMPTYPE="NoCollection" />
        </OPERATOR>
        <OPERATOR TYPE="IProductWRTBase">
            <ELEMENT TYPE="H" ORDER="*" IMPTYPE="SumFac" />
        </OPERATOR>
        <OPERATOR TYPE="IProductWRTDerivBase">
            <ELEMENT TYPE="H" ORDER="*" IMPTYPE="SumFac" />
        </OPERATOR>
        <OPERATOR TYPE="PhysDeriv">
            <ELEMENT TYPE="H" ORDER="*" IMPTYPE="MatrixFree" />
        </OPERATOR>
    </COLLECTIONS>
</NEKTAR>
I had manually added  <COLLECTIONS DEFAULT="auto" /> to my session file.
Are the above results of the latter?

Kind regards
syavash

On Wed, Aug 9, 2023 at 6:13 PM Jacques Xing <jacques.xing@kcl.ac.uk> wrote:
...
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:
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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... 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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