New Preconditioners for Nonsymmetric Saddle Point Systems with Singular (1,1) Block

Table 2

Iteration time and iteration numbers of GMRES of preconditioned matrices 𝒯⁻¹𝒜 and 𝓐⁻¹𝒜 for different 𝑘=2 with nullity =3𝑚/4.

	𝑚+𝑛	300	675	1200	2028	2700
𝒯^−1𝒜	Time	0.3066	14.3040	3449.2035	>3000	>5000
	Iter	10	100	>1000	>1000	>1000
𝓐^−1𝒜	Time	0.0667	0.4282	2.0694	255.0312	1519.8529
	Iter	2	3	3	7	17