************************* Matrix Drop Tolerance ************************* :: Matrix drop tolerance = ----------------------- 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 input parameter is: **tol,** a floating point number ( :math:`tol \geq 0` ) that specifies the drop tolerance. If the *Matrix drop tolerance* card is omitted, the default is **0.0.** ------------ Examples ------------ 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.