adaptive mesh refinement load balancing alternative / zoltanRenumber removed from openFoam-14

[mphaines]

The current user guide for AdditveFOAM discusses the use of zoltan for load balancing during adaptive mesh refinement, however zoltanRenumber appears to be deprecated for OpenFoam-14, so zoltan is no longer available for selection as a distributor. Using zoltan as the distributor under decomposeParDict will result in an error in additiveFoam if used. Are there any good alternatives here for load balancing with adaptive mesh refinement?

You can find the associated commit for removal of zoltanRenumber in OpenFOAM here: OpenFOAM/OpenFOAM-14@4b6b492

[colemanjs]

@mphaines, thank you for finding this issue with the documentation. You are correct that zoltanRenumber is depreciated in OpenFOAM-14, but you can still use Zoltan for mesh distribution. I will update the documentation and add an example to the tutorial to demonstrate this.

This brings up an open question that I have want to explore: which mesh distribution method available in OpenFOAM-14 is most performant for general AdditiveFOAM cases (fvMeshDistributor, Zoltan, ptScotch [what OpenFOAM-14 recommends]). I will test this as part of the documentation and tutorial update.

A larger development effort should focus on writing our own distributor wrapper, or possibly, configure AdditiveFOAM with cpuLoad to that the Zoltan load balancing will work properly.

[colemanjs]

@mphaines, I have two PRs in #106 and #107 to correct this issue. The AMB2018-02-B tutorial has been updated to demonstrate the mesh redistribution. Performance studies showed ptscotch to be the recommended distributor (also recommended by OpenFOAM-14). This redistribution operates on cell-counts, not the calculated wall-clock time of each core. We will need to configure and test AdditiveFOAM with cpuLoad to enable this functionality.

[mphaines]

@colemanjs Thank you for the quick response time and resolution!