gov.sandia.cognition.math.matrix.custom

Class DenseMatrix.LU

java.lang.Object

gov.sandia.cognition.math.matrix.custom.DenseMatrix.LU

Enclosing class:

DenseMatrix

public static class DenseMatrix.LU
extends java.lang.Object

Simple container class for LU decompositions. LU decomposition results in a lower triangular matrix (L) and an upper triangular matrix (U). This decomposition can be used for matrix inversion, determinant computation, etc.

Field Summary

Fields

Modifier and Type	Field and Description
Matrix	L The lower triangular matrix resulting from the factorization.
java.util.List<java.lang.Integer>	P The 0-based list of row swaps used in the factorization.
Matrix	U The upper triangular matrix resulting from the factorization.

Method Summary

Modifier and Type	Method and Description
Matrix	getPivotMatrix() Helper method converts P into a pivot matrix that can pre-multiply L*U.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

P

public java.util.List<java.lang.Integer> P

The 0-based list of row swaps used in the factorization. NOTE: If row 0 is swapped with row 1, P will contain [1, 1, 2, ...] (because if it said [1, 0, 2, ...] that would mean that it swapped row 0 with 1 and then row 1 with 0 (swapping back the original rows)). If this seems too confusing, just use the getPivotMatrix helper method.

L

public Matrix L

The lower triangular matrix resulting from the factorization.

U

public Matrix U

The upper triangular matrix resulting from the factorization.

Method Detail

getPivotMatrix

public Matrix getPivotMatrix()

Helper method converts P into a pivot matrix that can pre-multiply L*U.

Returns:

an identity matrix with the appropriate row swaps to re-generate the original matrix A when P * L * U is calculated.