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

Algorithmic aspects and computational efficiency of the global basis two-level method are investigated in the context of symmetric indefinite system of equations. The algorithm includes efficient construction of the global basis prolongator using Lanczos vectors, predictor-corrector smoothing procedures, and a heuristic two-level feedback loop aimed at ensuring convergence. Numerical experiments consisting of 3D Helmholtz equations and shear banding problems with strain softening demonstrate the excellent performance of the method.