[petsc-users] Parallel DMPlex Local to Global Mapping

[Ferrand, Jesus A.]

Dear PETSc Team:

Hi! I'm working on a parallel version of a PETSc script that I wrote in serial using DMPlex. After calling DMPlexDistribute() each rank is assigned its own DAG where the points are numbered locally. For example, If I split a 100-cell mesh over 4 processors, each process numbers their cells 0-24 as oppossed to something like 0-24, 25-49, 50-74, and 74-99 on ranks 0,1,2, and 3 respectively. The same happens for Face, Edge, and Vertex points in that the local DAG's renumber the ID's starting with 0 instead of using global numbering.

How can I distribute a mesh such that the global numbering is reflected in the local DAG's? If not, what would be the right way to retrieve the global numbering? I've seen the term "StarForest" in some [petsc-users] discussion threads discussing a similar issue but have little clue as how to use them.

I've looked at the following functions:

  *   DMPlexCreatePointNumbering() - Sounds like what I need, but I don't think it will work because I am relying on DMPlexGetDepthStratum() which returns bounds in local numbering.
  *   DMPlexGetCellNumbering() - Only converts Cells
  *   DMPlexGetVertexNumbering() - Only converts Vertices

Basically, what I want to do is to have a global matrix and have my MPI ranks call MatSetValues() on it (with ADD_VALUES as the mode). In my serial code I was relying on the global point numbering to build the matrix. Without it, I can't do it my way : (. I'm manually assembling a global stiffness matrix out of element stiffness matrices to run FEA.

Any help is much appreciated.

Sincerely:

J.A. Ferrand

Embry-Riddle Aeronautical University - Daytona Beach FL

M.Sc. Aerospace Engineering | May 2022

B.Sc. Aerospace Engineering

B.Sc. Computational Mathematics



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Phone: (386)-843-1829

Email(s): ferranj2 at my.erau.edu

    jesus.ferrand at gmail.com
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