[petsc-users] Simple KSP with known solution gives infinite solution

[zakaryah]

I'm looking for some help with a terribly simple problem.  I am trying to
solve a linear system which is very small, as a test.  The vectors are
derived from a minimal 3D DMDA (3x3x3), with 3 dof, so that the RHS and
solution vectors have dimension 81 and the matrix is 81x81.  I have checked
that the matrix is symmetric, invertible (empty null space), and that the
desired solution is reasonable, i.e. has no large values.  The condition
number of the matrix is about 3600.  When I run KSPSolve with default
settings, I see convergence in a single iteration (gmres, pc_type lu,
jacobi, none, or svd).  However, the solution is infinite in all entries.
Any suggestions for debugging this?  Thanks!
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