[petsc-users] Question on some PETSc functions.

[Gaurish Telang]

I have 2 semi sparse matrices (see sparsity plots) attached and I wanted to
get to know some basic information about them.

1. How does one calculate the rank of a matrix in PETSc. Is the answer
returned approximate or exact for matrices of dimension say 2500X1200

2. How good are the sparse sovlers for Ax=b that PETSc employs when A is a
dense full rank square matrix of size 2000x2000.

3. In my case the matrices are mostly sparse but they tend to get dense
towards the bottom. What matrix format is most efficent for handling  such
matrices?
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