A novel multilevel inverse-based ILU (MIB-ILU) preconditioning approach is applied to the hybrid finite-element/boundary-integral/multilevel fast multipole algorithm (FE/BI/MLFMA) for 3D scattering problems.Unlike the traditional ILU preconditioning technique

this MIB-ILU approach borrows the concept of the algebraic multi-grid method (AMG) to construct an algebraic multilevel recursive ILU preconditioning framework.Moreover

a new version of ILU factorization and an inverse-based dropping strategy are employed to improve the robust of the preconditioning approach.The numerical performance of the proposed MIB-ILU approach is studied.It is demonstrated that this approach exhibits high efficiency in memory and CPU time.Then

the proposed MIB-ILU approach is applied to the hybrid FE/BI/MLFMA method.A variety of numerical experiments are carried out

demonstrating that the proposed approach offers a good compromise between robustness and efficiency

and greatly improves the computing capability of the hybrid FE/BI/MLFMA.