Difference between direct and iterative solvers in HFSS

The direct solver provides a multi-frontal approach when a matrix is not well-conditioned for an iterative solution. The iterative solver significantly reduces memory usage and can also provide savings in solution time for large simulations. If the iterative solver fails to solve, the solver automatically falls back to the direct method.

Another option in HFSS is the Auto Select Direct/Iterative, which is designed to optimize the solution process by automatically choosing between the direct and iterative solvers for each pass. Enabling this option could therefore potentially improve the speed of the simulation while maintaining accuracy.