Factorized sparse approximate inverse preconditioning strategies for MLFMA

We consider the solution of large electromagnetic scattering problems involving three-dimensional arbitrarily shaped targets using the multilevel fast multipole algorithm (MLFMA). One kind of parallel sparse approximation inverse preconditioner is employed to reduce the iteration counts for the solutions of the electric-field integral equation (EFIE) and the combined-field integral equation (CFIE). Even though CFIE produces better conditioned systems compared to EFIE, we still need EFIE for problems involving open geometries since CFIE is limited to the solution of closed geometries.