The convergence of diagonal elements of an irreducible symmetric tridiagonal matrix under QL algorithm with some kinds of shift is discussed. It is proved that if α₁—σ→0 and βj→0, j = 1, 2, ···, m, ...

The solution of a general block tridiagonal linear system by a cyclic odd-even reduction algorithm is considered. Under conditions of diagonal dominance, norms describing the off-diagonal blocks ...