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

Table 2

Construction time and solution time (in seconds) for the paraboloid antenna.

Basis functions	Mesh sizes	Unknowns	Solution method	Construction time	Iteration step	Solution time	Total time
2-order	0.3𝜆	19,992	GMRES	—	470	1,334	1334
			FGMRES	—	52	179	179
			Two-level	134	17	45	179
3-order	0.5𝜆	17,652	GMRES	—	1593	2,106	2106
			FGMRES	—	111	355	355
			Two-level	101	26	49	150