Is there a way to inspect the graph of a sparse matrix with PETSc?

Question

I am currently trying to code the CA-CG method within the PETSc framework. A mandatory step in this process is the implementation of the "matrix powers kernel" algorithm for a generic sparse matrix.

This requires the computation of the index set obtained exploring the graph associated with the sparse matrix for s-steps, starting from the index set of the local rows "owned" by each process.

Is there a clean way to retrieve this kind of information using the PETSc API?

Answer 1

Use MatIncreaseOverlap() just like PCASM (additive Schwarz preconditioner) to get the overlapping region, then MatGetSubMatrices() (also like PCASM) to pull out the overlapping part of the matrix.

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