Turbulence in closed space

[Adrian]

OpenMP taking three times longer should not happen in any case, probably the thread configuration is faulty there. I am interested in any update on this.

As for the compilation error: There shouldn’t be angle brackets there. You can try to replace them with quotation marks.

Better support for using OpenLB in separate applications outside of its folder are on our todo list. What is your setup there? Do you use OpenLB’s precompiled mode for the shared library?

[jdm]

Hi Adrian,

I’ll keep you updated as soon as I can try running OpenLB examples with OMP on the cluster!

Changing the angle brackets for quotation marks solved the issue. My simulation using OpenLB as a shared library (so outside of OpenLB folder) is working good now.
In this simulation, I encapsulate the OpenLB simulation inside an other simulation framework (the BioDynaMo framework).

In brief, I run the main (BioDynaMo) simulation that will call OpenLB every x time steps. Information from the BioDynaMo simulation are used to construct, initialise and run the OpenLB simulation. Results from The OpenLB simulation are then transmitted to BioDynaMo in order to update it, run it a number of time steps before calling OpenLB again. This loop is repeated several times to complete the main BioDynaMo simulation.
We run the whole process inside a docker container for better control of the environment and for repeatability.

I use the precompiled mode of OpenLB for the shared library, yes.

[jdm]

Hi again,

I have been able to run a quick benchmark using the nozzle3d example on OpenLB 1.4.

As you can see, the maximum speedup using OMP is about x7.7. Surprisingly, this maximum speedup with OMP is achieved using only 17 threads out of 144. adding more than 17 threads increases the runtime.
On the contrary, the maximum speedup using MPI if about x26 and is achieved using 72 processes (for 72 cores).

I hope this can useful for you!
jdm

[Adrian]

Seems to be an interesting application! Thank you for expanding on it. Feel free to contact me if you want to talk about possibilities for collaboration in the integration between your application and OpenLB.

The scaling plot doesn’t look good for OpenMP at all. I’ll take a closer look on my own system.

Did you change anything wrt. the OpenMP configuration you posted previously?

[jdm]

Thanks!
I have set OMP_PROC_BIND=close and OMP_PLACES=cores as you suggested, otherwise I used the same configuration as previously.

[Author]

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