Different Versions of ILU and IUL Factorizations Obtained from Forward and Backward Factored Approximate Inverse Processes - Part I

We present an incomplete UL IUL decomposition of matrixAwhich is extracted as a by-product of BFAPINV backward factored approximate inverse process. We term this IUL factorization as IULBF. We have used ILUFF 3 and IULBF as left preconditioner for linear systems. Different versions of ILUFF and IULBF preconditioners are computed by using different dropping techniques. In this paper, we compare quality of different versions of ILUFF and IULBF preconditioners.