Changes from ITPACKV 2C

This version of ITPACKV is an update of an earlier version, ITPACKV 2C. In this version, the SOR(), SSORCG(), and SSORSI() modules have been modified so they are vectorizable in the case of natural ordering. These modules permute the system Au=b according to a ``wave front" ordering prior to iterating and unpermute the system after iterating. The wave front ordering is determined for these routines by finding the sets of unknowns that can be updated simultaneously (e.g., the unknowns along the diagonals of the mesh for a 5-point star operator on a rectangular grid). The vector lengths of these wave fronts are dependent upon the sparsity pattern of the matrix as well as the size of the matrix, but are typically much smaller than N. This technique of vectorization will be effective on vector computers which do not have large start-up costs for vector operations.

Also, for the SOR(), SSORCG(), and SSORSI() modules, the matrix is scaled by $\omega$ to reduce the operation count during the forward and backward SOR passes. The scaling process is done every time $\omega$ is changed. Finally, the routine DETERM() was rewritten to use the Cray library routine SOLRN(), if it is available. See [9] for details on the vectorization techniques used in ITPACKV 2D.