Parallel mesh construction

Question

I'm having trouble creating a mesh in parallel. I am creating a mesh using

// make the mesh
mesh = make_shared<dfn::UnitSquareMesh>(MPI_COMM_WORLD, 20, 20);

Running the code with 2 processors, I get the error message

*** -------------------------------------------------------------------------
*** Error:   Unable to create mesh entity.
*** Reason:  Mesh entity index 0 out of range [0, 0] for entity of dimension 1.
*** Where:   This error was encountered inside MeshEntity.cpp.
*** Process: 0
*** 
*** DOLFIN version: 2017.1.0.dev0
*** Git changeset:  4b0cda02df108e11a3384f6ae3affa73bd29944d
*** -------------------------------------------------------------------------

It is perhaps worth mentioning that a similar error message does not appear for process 1. If I run the code it serial (or replacing MPI_COMM_WORLD with MPI_COMM_SELF) it works fine.

Does anyone know what I could be doing wrong? or what could be causing this?

Comments

Seems to work fine for me. Did you also try without MPI_COMM_WORLD/MPI_COMM_SELF? That is

auto mesh = std::make_shared<dfn::UnitSquareMesh>(20, 20);

Maybe you can post a complete minimal example that reproduce the problem? Can you reproduce it yourself with the latest DOLFIN master in the quay.io/fenicsproject/dev Docker container? The Git changeset id in your error message is from January 31. You can see if upgrading to the latest development version fixes the problem.

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Unfortunately no --- in fact, I got the code to work perfectly on a different machine, which makes me thing it is something about how I am compiling/linking everything that is the problem. Do you know what the error means? Perhaps that would be provide some insight as to which library is wrong ...

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No, I don't know. It could be a problem with some libraries like MPI, ParMETIS or SCOTCH (depending on what you use). See also related problems here and here.

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Yup! turns out fenics and petsc were linking to different ParMETIS libraries ...