Why do I get error Error: 'Unable to evaluate function at point. Reason: The point is not inside the domain.' when trying to run my legacy FeNics scripts in parallel?

[dokken]

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Not getting a better performance in parallel

The problem is that you are running a too small problem to get any effect of using multiple processes. Since parallel computing requires communication, it is a balancing act to find how many dofs should be on each process. For instance, if you increase the number of dofs in your problem by using a 500x500 unit square mesh (1 million dofs in your mixed space), the average time for using the krylov solver 10 times is 9.96 seconds in serial. Using 2 procs it reduces to 9.086900045000002 However,…

Problem solving in parallel slower than in serial

This is due to garbage management in PETSc, see: Add explicit destruction of PETSc Python objects by garth-wells · Pull Request #2560 · FEniCS/dolfinx · GitHub which resolved this. Please note that the problem you are solving isn’t very large, i.e. num dofs= 27 783. In general I would suggest having between 50 000 - 100 000 dofs per process. Finally, I cannot reproduce your results with the docker image dolfinx/dolfinx:nightly: from ufl import TestFunction, TrialFunction, dx, inner, grad, …

Parallel slower runtime

I cannot reproduce your problem: root@82df035a5e65:~/shared# python3 mwe.py MESH CREATED 0 , time : 0.08017910199987455 root@82df035a5e65:~/shared# mpirun -n 2 python3 mwe.py MESH CREATED 0 , time : 0.0637212950000503 MESH CREATED 1 , time : 0.06375895700011824 root@82df035a5e65:~/shared# mpirun -n 4 python3 mwe.py MESH CREATED 0 , time : 0.06122965600025054 MESH CREATED 1 , time : 0.06122667699992235 MESH CREATED 2 , time : 0.061187144000086846 MESH CREATED 3 , time : 0.0612255729997…