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Old   May 13, 2020, 17:58
Default DecomposePar
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Sricharan S Veeturi
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Hello Foamers,

I have recently started using openFOAM and I use an HPC cluster to run my simulations. Since I am running the job on parallel cores, I am using the decomposePar file in which I specify the method of distribution (Simple, Hierarchical or scotch). Currently I am using scotch however, I see that the reconstruction of the distributed domain takes a lot of time.

In my specific case, I have a mesh of 5 million elements and I run this on 6 nodes with 40 cores each (a total of 240 cores). The simulation itself (running a pimpleFoam model) takes about 10 hours which is good however, the reconstructPar takes 5 hours! which is 30% of the total time. Am I missing something? Will it make a difference if I use Simple or the hierarchical method? I'm not exactly sure why the reconstruction takes so long.
Experts, please correct any misconception I may have on my part.

Thank you.

Last edited by veeturi; May 14, 2020 at 19:05.
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Old   May 14, 2020, 01:58
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- reconstructPar is a serial execution utility.
- please try to use 'mpirun -np X redistributePar -reconstruct -parallel -latestTime', to see if it helps.
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Old   May 14, 2020, 19:07
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Sricharan S Veeturi
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Yes. That helped. Actually I'm running a field average as well on the simulation hence, all the results I need are in the last time step.

Thank you!
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openfoam v6 + centos 7, parallel calculation, pimplefoam, reconstructpar

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