Add -mpi_linear_solver_server
Added -mpi_linear_solver_server that allows using MPI parallel KSP solvers from sequential or OpenMPI code
Uses -ksp_type preonly -pc_type mpi
@jedbrown @knepley @stefanozampini @caidao22 @hongzhangsun @fdkong This MR is ready for review.
Edited by Barry Smith