Package org.tribuo.math.la

Class DenseMatrix.LUFactorization

java.lang.Object

org.tribuo.math.la.DenseMatrix.LUFactorization

All Implemented Interfaces:

Matrix.Factorization

Enclosing class:

DenseMatrix

public static final class DenseMatrix.LUFactorization
extends Object
implements Matrix.Factorization

The output of a successful LU factorization.

Essentially wraps a pair of DenseMatrix, but has additional operations which allow more efficient implementations when the matrices are known to be the result of a LU factorization.

Mutating the wrapped matrices will cause undefined behaviour in the methods of this class.

May be refactored into a record in the future.

Method Summary

Modifier and Type	Method	Description
double	determinant()	Compute the matrix determinant of the factorized matrix.
int	dim1()	First dimension of the factorized matrix.
int	dim2()	Second dimension of the factorized matrix.
DenseMatrix	lower()	The lower triangular matrix, with ones on the diagonal.
boolean	oddSwaps()	Is there an odd number of row swaps (used to compute the determinant).
int[]	permutationArr()	The row permutations applied to get this factorization.
Matrix	permutationMatrix()	The row permutations stored as a sparse matrix of ones.
DenseMatrix	solve(Matrix matrix)	Solves the system A * X = Y, where Y is the input matrix, and A is the matrix which produced this LU factorization.
DenseVector	solve(SGDVector vector)	Solves a system of linear equations A * b = y, where y is the input vector, A is the matrix which produced this LU factorization, and b is the returned value.
DenseMatrix	upper()	The upper triangular matrix.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.tribuo.math.la.Matrix.Factorization

inverse

Method Details

lower

public DenseMatrix lower()

The lower triangular matrix, with ones on the diagonal.

Returns:

The lower triangular matrix.

upper

public DenseMatrix upper()

The upper triangular matrix.

Returns:

The upper triangular matrix.

permutationArr

public int[] permutationArr()

The row permutations applied to get this factorization.

Returns:

The permutations.

permutationMatrix

public Matrix permutationMatrix()

The row permutations stored as a sparse matrix of ones.

Returns:

A sparse matrix version of the permutations.

oddSwaps

public boolean oddSwaps()

Is there an odd number of row swaps (used to compute the determinant).

Returns:

True if there is an odd number of swaps.

dim1

public int dim1()

Description copied from interface: Matrix.Factorization

First dimension of the factorized matrix.

Specified by:

dim1 in interface Matrix.Factorization

Returns:

First dimension size.

dim2

public int dim2()

Description copied from interface: Matrix.Factorization

Second dimension of the factorized matrix.

Specified by:

dim2 in interface Matrix.Factorization

Returns:

Second dimension size.

determinant

public double determinant()

Compute the matrix determinant of the factorized matrix.

Specified by:

determinant in interface Matrix.Factorization

Returns:

The matrix determinant.

solve

public DenseVector solve(SGDVector vector)

Solves a system of linear equations A * b = y, where y is the input vector, A is the matrix which produced this LU factorization, and b is the returned value.

Specified by:

solve in interface Matrix.Factorization

Parameters:

vector - The input vector y.

Returns:

The vector b.

solve

public DenseMatrix solve(Matrix matrix)

Solves the system A * X = Y, where Y is the input matrix, and A is the matrix which produced this LU factorization.

Specified by:

solve in interface Matrix.Factorization

Parameters:

matrix - The input matrix Y.

Returns:

The matrix X.