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

Table 4

3D Dirichlet problem (different 𝑘²).

	𝑘=10	𝑘=20	𝑘=30	𝑘=40	𝑘=50
ℎ=1/64	4∣7∣14	5∣10∣23	6∣13∣25	12∣div∣ >100	19∣div∣ >100
ℎ=1/128	3∣5∣14	3∣6∣15	4∣8∣17	4∣10∣69	5∣11∣ >100
ℎ=1/256	3∣4∣12	3∣5∣14	3∣6∣13	3∣6∣22	4∣7∣63
𝜓	2.02	2.00	1.98	2.00	2.02