The Parallel QR Factorization Algorithm for Tridiagonal Linear Systems

We describe a new parallel solver in the class of partition methods for general, nonsingular tridiagonal linear systems. Starting from an already known partitioning of the coefficient matrix among the parallel processors, we define a factorization, based on the QR factorization, which depends on the conditioning of the sub-blocks in each processor. Moreover, also the reduced system, whose solution is the only scalar section of the algorithm, has a dimension which depends both on the conditioning of these sub-blocks, and on the number of processors. We analyze the stability properties of the obtained parallel factorization, and report some numerical tests carried out on a net of transputers.