Matrix Scaling#
Matrix scaling = {char_string}
Description / Usage#
This optional card selects a scaling for the linear matrix system solution step.Valid options for {char_string} are listed below.
- none
No scaling is performed. This is the default if no Matrix Scaling card is present.
- Jacobi
Point Jacobi scaling is performed.
- BJacobi
Block Jacobi scaling is performed if the underlying matrix format is VBR. If the MSR matrix format is used, the scaling reverts to point Jacobi.
- row_sum
Scale each row so the sum of the magnitudes of the nonzero elements is 1.
- sym_diag
Symmetric scaling so that diagonal elements are 1.
- sym_row_sum
Symmetric scaling using the matrix row sums.
If the Matrix Scaling card is omitted, the default selection is none.
Examples#
Following is a sample card:
Matrix scaling = sym_diag
Technical Discussion#
All of these scalings are supplied via the Aztec library and thus will not affect the linear systems that are solved by other means (using front, for example). In an odd twist of fate, the linear system always undergoes a row sum scaling (equivalent to the row_sum option) before these other scalings are applied. Note that when a nontrivial scaling is selected, the matrix is overwritten with a rescaled system.