> Which solvers are more appropriate for symmetric matrices? Iterative solvers: ksp_type cg, pc_type icc Direct solvers: ksp_type preonly, pc_type cc Non-symmetric solvers also work, but the above solvers are more efficient in general. You can run petsc code with various ksp/pc combinations, and use the option '-log_summary' to evaluate the performance. Using '-help' to see all solver options. Hong