A Double-Parameter GPMHSS Method for a Class of Complex Symmetric Linear Systems from Helmholtz Equation

Table 2

The experimentally optimal parameters and the corresponding spectral radii for the iteration matrices of GPMHSS and DGPMHSS with 𝑉=𝑊−𝑇 and 𝑚=16.

	𝜎2
	10	50	80	100
GPMHSS
𝛼^∗𝐺	1.1	1.5	2.2	1.8
𝜌(𝑀𝛼^∗𝐺)	0.5010	0.5230	0.5697	0.6337
DGPMHSS
𝛼^∗𝐷	1.1	1.5	2.2	1.8
𝛽^∗𝐷	1	1	0.9	0.9
𝜌(𝑀𝛼^∗𝐷,𝛽^∗𝐷)	0.5004	0.5063	0.5235	0.5097