Matrix BILU Threshold#
Matrix BILU threshold = <float>
Description / Usage#
This capability is only present within the Trilinos library. This optional card provides a means to modify the way the block ILU preconditioner (Matrix subdomain solver = bilu) is constructed. The input parameter is defined as:
t, a floating point number ( t ≥ 0.0 ) that sets the Matrix Relative Threshold and Matrix Absolute Threshold thresholds.
When the Matrix BILU threshold card is omitted, the default value is 0.0.
Following is a sample card:
Matrix BILU Threshold = 1.0e-14
Using this card is equivalent to supplying both the Matrix Relative Threshold and Matrix Absolute Threshold with the value specified with this card.
The value of t defaults to zero, and if given a small value, say 1.0e-14, the condition number of the preconditioner, as reported when using the bilu option, should decrease. Try increasing up to around 1.0e-3 to get added benefit. The bilu preconditioner is not actually the cheapest or most efficient preconditioner, but it is very robust.