Indefinite block triangular preconditioner for symmetric saddle point problems (Q1946604)

Symmetric saddle point problems are studied. In particular, block triangular preconditioners are considered, which in addition can be indefinite. For the actual calculation a Krylov space method is used and then it is important to know something about the eigenvalue distribution of the preconditioned coefficient matrix. In this paper, some earlier results about this problem are improved leading to better iterative methods. Some numerical experiments of a model Stokes problem are reported which confirm these results numerically.