org.jblas.util

Class Permutations

java.lang.Object

org.jblas.util.Permutations

public class Permutations
extends Object

Functions which generate random permutations.

Author:

Mikio L. Braun

Constructor Summary

Constructors

Constructor and Description
Permutations()

Method Summary

Modifier and Type	Method and Description
static DoubleMatrix	permutationDoubleMatrixFromPivotIndices(int size, int[] ipiv) Create a permutation matrix from a LAPACK-style 'ipiv' vector.
static FloatMatrix	permutationFloatMatrixFromPivotIndices(int size, int[] ipiv) Create a permutation matrix from a LAPACK-style 'ipiv' vector.
static int[]	randomPermutation(int size) Create a random permutation of the numbers 0, ..., size - 1.
static int[]	randomSubset(int k, int n) Get a random sample of k out of n elements.

Methods inherited from class java.lang.Object

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

Constructor Detail

Permutations

public Permutations()

Method Detail

randomPermutation

public static int[] randomPermutation(int size)

Create a random permutation of the numbers 0, ..., size - 1. see Algorithm P, D.E. Knuth: The Art of Computer Programming, Vol. 2, p. 145

randomSubset

public static int[] randomSubset(int k,
                                 int n)

Get a random sample of k out of n elements. See Algorithm S, D. E. Knuth, The Art of Computer Programming, Vol. 2, p.142.

permutationDoubleMatrixFromPivotIndices

public static DoubleMatrix permutationDoubleMatrixFromPivotIndices(int size,
                                                                   int[] ipiv)

Create a permutation matrix from a LAPACK-style 'ipiv' vector.

Parameters:

ipiv - row i was interchanged with row ipiv[i]

permutationFloatMatrixFromPivotIndices

public static FloatMatrix permutationFloatMatrixFromPivotIndices(int size,
                                                                 int[] ipiv)

Create a permutation matrix from a LAPACK-style 'ipiv' vector.

Parameters:

ipiv - row i was interchanged with row ipiv[i]