A new scheme of computing the approximate inverse preconditioner for the reduced linear systems

In this paper, we propose a new implementation of the Newton scheme of an approximate preconditioner for the reduced linear system. In the original Newton scheme, the trouble is that the computation cost of the matrix-matrix product is always so expensive. On the other hand, the proposed implementation computes the preconditioner implicitly and reduces the cost of constructing the preconditioner by using the matrix-vector product form. We also show that the proposed implementation is less expensive than computing the preconditioner in explicit form.