This paper describes the implementation of a recursive descent method for solving block Hessenberg systems. Although the algorithm is conceptually simple, its implementation in C (a natural choice of language given the recursive nature of the algorithm and its data) is nontrivial. Particularly important is the balance between ease of use, computational eeciency, and exibility. This report and t...

In this paper, we investigate the block Lanczos algorithm for solving large sparse symmetric linear systems with multiple right-hand sides, and show how to incorporate deeation to drop converged linear systems using a natural convergence criterion, and present an adaptive block Lanczos algorithm. We propose also a block version of Paige and Saun-ders' MINRES method for iterative solution of sym...