Global-basis two-level method for indefinite systems. Part 2: computational issues

Algorithmic aspects and computational efficiency of the global-basis two-le vel method are investigated in the context of symmetric indefinite system o f equations. The algorithm includes efficient construction of the global-ba sis prolongator using Lanczos vectors, predictor-corrector smoothing proced ures, and a heuristic two-level feedback loop aimed at ensuring convergence . Numerical experiments consisting of 3D Helmholtz equations and shear band ing problems with strain softening demonstrate the excellent performance of the method. Copyright (C) 2000 John Wiley & Sons, Ltd.