Preconditioned Krylov Subspace Methods for Sixth Order Compact Approximations of the Helmholtz Equation

Table 6

3D Dirichlet-Neumann problem (different 𝑘²).

	𝑘=10	𝑘=20	𝑘=30	𝑘=40	𝑘=50
ℎ=1/64	6∣10	8∣11	18∣div	36∣div	>600 ∣div
ℎ=1/128	4∣9	5∣8	8∣9	14∣div	28∣div
ℎ=1/256	3∣8	4∣7	5∣div	9∣div	7∣div
ℎ=1/512	2∣6	3∣6	3∣6	5∣6	4∣6
𝜓	2.57	2.18	2.39	1.65	1.94