Eric : > I just want to know if there is a known difficulty or unfeasible task if > someone would like to implement MatMatSolve_MUMPS? MatMatSolve_MUMPS is supported in petsc-dev. It calls MatMatSolve_Basic() with then calls MatSolve_MUMPS in a loop. MUMPS own matmatsolve requires entire rhs matrix store in the host which is non-scalable. Hong