> > > > -fieldsplit_velocity_ksp_type preonly -fieldsplit_velocity_pc_type gamg > -fieldsplit_pressure_ksp_type minres -fieldsplit_pressure_pc_type none >
You should use cg for the ksp_type with gamg if you are symmetric and gmres if not (you can try cg even if it is mildly asymmetric). minres is for indefinite symmetric, but you probably are SPD and should use cg.
