Application of Hierarchical Two-Level Spectral Preconditioning Method for Electromagnetic Scattering from the Rough Surface

Table 3

Construction time and solution time (in seconds) for the missile target above a rough surface.

Basis functions	Mesh sizes	Unknowns	Solution method	Construction time	Iteration step	Solution time	Total time
2-order	0.3𝜆	55,744	GMRES	—	601	1938	1938
			FGMRES	—	113	662	662
			Two-level	618	31	100	718
3-order	0.5𝜆	31,836	GMRES	—	3441	10,685	10,685
			FGMRES	—	191	1213	1213
			Two-level	372	51	167	539