Matrix Drop Tolerance#

Matrix drop tolerance = <float>

Description / Usage#

This optional card indicates to Aztec a drop tolerance to be used in conjunction with preconditioners based on LU or on ILUT. The <float> input parameter is:


tol, a floating point number ( \(tol \geq 0\) ) that specifies the drop tolerance.

If the Matrix drop tolerance card is omitted, the default is 0.0.


Following is a sample card:

Matrix drop tolerance = 0.01

Technical Discussion#

When constructing the partial factorization(s), any value less than tol is dropped. If set to 0.0, then other parameters will govern preconditioner size and components (e.g., Matrix ILUT fill factor for the ILUT preconditioner).

The two main parameters when using the ILUT preconditioner are this card and the Matrix ILUT fill factor card. The restrictions in Matrix ILUT fill factor take precedence over the dropped entries caused by this card.