Matrix Reorder

Matrix reorder = {none | rcm}

Description / Usage

This optional card determines whether RCM (Reverse Cuthill-McKee) reordering of the linear system is to be performed. Valid options are:

none

the equations are not reordered.

rcm

the equations are reordered using an RCM scheme.

If the Matrix reorder card is omitted, then the default selection is none.

Examples

Following is a sample card:

Matrix reorder = rcm

Technical Discussion

Note that reordering frequently is helpful in achieving convergence for iterative solution of linear systems. In a few instances, however, Goma users have noted that RCM reordering hinders convergence for selected problems. The default for Goma is to not use the RCM reordering so that quantitatively comparable results are obtained using either Aztec 1 (which did not have RCM reordering as an option) or Aztec 2.x. In summary, users are encouraged to try RCM reordering when using iterative solvers, foregoing the option only as a further resort in the face of repeated convergence failures.