Some numerical experiences on convergence criteria for iterative finite element solvers

Several popular convergence criteria which are frequently used in practical finite element computations are investigated for two kinds of systems: the symmetric positive definite linear system and the symmetric indefinite system involving two distinct variables (displacement and pore fluid pressure). For the first system, the relative residual norm and the relative improvement norm are satisfactory as long as boundary fixities are handled appropriately. For the second system, the relative improvement norm must be adopted with greater care. It was further shown numerically that decoupled relative residual norms can be attractive alternates to the current global stopping criterion.