org.apache.commons.math.linear

Interface FieldLUDecomposition<T extends FieldElement<T>>

• Type Parameters:
T - the type of the field elements
All Known Implementing Classes:
FieldLUDecompositionImpl

public interface FieldLUDecomposition<T extends FieldElement<T>>
An interface to classes that implement an algorithm to calculate the LU-decomposition of a real matrix.

The LU-decomposition of matrix A is a set of three matrices: P, L and U such that P×A = L×U. P is a rows permutation matrix that is used to rearrange the rows of A before so that it can be decomposed. L is a lower triangular matrix with unit diagonal terms and U is an upper triangular matrix.

This interface is based on the class with similar name from the JAMA library.

• a getP method has been added,
• the det method has been renamed as getDeterminant,
• the getDoublePivot method has been removed (but the int based getPivot method has been kept),
• the solve and isNonSingular methods have been replaced by a getSolver method and the equivalent methods provided by the returned DecompositionSolver.
Since:
2.0
MathWorld, Wikipedia
• Method Detail

• getL

FieldMatrix<T> getL()
Returns the matrix L of the decomposition.

L is an lower-triangular matrix

Returns:
the L matrix (or null if decomposed matrix is singular)
• getU

FieldMatrix<T> getU()
Returns the matrix U of the decomposition.

U is an upper-triangular matrix

Returns:
the U matrix (or null if decomposed matrix is singular)
• getP

FieldMatrix<T> getP()
Returns the P rows permutation matrix.

P is a sparse matrix with exactly one element set to 1.0 in each row and each column, all other elements being set to 0.0.

The positions of the 1 elements are given by the pivot permutation vector.

Returns:
the P rows permutation matrix (or null if decomposed matrix is singular)
getPivot()
• getPivot

int[] getPivot()
Returns the pivot permutation vector.
Returns:
the pivot permutation vector
getP()
• getDeterminant

T getDeterminant()
Return the determinant of the matrix
Returns:
determinant of the matrix
• getSolver

FieldDecompositionSolver<T> getSolver()
Get a solver for finding the A × X = B solution in exact linear sense.
Returns:
a solver