NEW PRECONDITIONERS FOR NONSYMMETRIC AND INDEFINITE SADDLE POINT LINEAR SYSTEMS.

In this paper, we extend the preconditioners of Sturler and Liesen [SIAM J. Sci. Comput., 26(2005): 1598-1619]. The spectral characteristics of the preconditioners are investigated and the results show that all eigenvalues of the preconditioned matrices are strongly clustered. Finally, numerical experiments are also reported for illustrating the efficiency of the presented preconditioners. [ABSTRACT FROM AUTHOR]