Package org.ejml.sparse.csc.decomposition.qr

Class QrHelperFunctions_DSCC

java.lang.Object

org.ejml.sparse.csc.decomposition.qr.QrHelperFunctions_DSCC

public class QrHelperFunctions_DSCC
extends Object

Functions used with a sparse QR decomposition

Constructor Summary

Constructors

Constructor	Description
QrHelperFunctions_DSCC()

Method Summary

Modifier and Type	Method	Description
static void	applyHouseholder(DMatrixSparseCSC V, int colV, double beta, double[] x)	Applies a sparse Householder vector to a dense vector.
static double	computeHouseholder(double[] x, int xStart, int xEnd, double max, DScalar gamma)	Creates a householder reflection.
static void	rank1UpdateMultR(DMatrixSparseCSC V, int colV, double gamma, DMatrixSparseCSC A, DMatrixSparseCSC C, @Nullable IGrowArray gw, @Nullable DGrowArray gx)	Performs a rank-1 update operation on the submatrix specified by V with the multiply on the right. C = (I - γ*v*vT)*A

Methods inherited from class java.lang.Object

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

Constructor Details

QrHelperFunctions_DSCC

public QrHelperFunctions_DSCC()

Method Details

applyHouseholder

public static void applyHouseholder(DMatrixSparseCSC V,
 int colV,
 double beta,
 double[] x)

Applies a sparse Householder vector to a dense vector.

     x = x - v*(beta*(v'*x))

NOTE: This is the same as cs_happly() in csparse

Parameters:

V - (Input) Matrix containing the Householder

colV - Column in V with the Householder vector

beta - scalar

x - (Input and Output) vector that the Householder is applied to. Modified.

rank1UpdateMultR

public static void rank1UpdateMultR(DMatrixSparseCSC V,
 int colV,
 double gamma,
 DMatrixSparseCSC A,
 DMatrixSparseCSC C,
 @Nullable
 @Nullable IGrowArray gw,
 @Nullable
 @Nullable DGrowArray gx)

Performs a rank-1 update operation on the submatrix specified by V with the multiply on the right.

C = (I - γ*v*v^T)*A

The order that matrix multiplies are performed has been carefully selected to minimize the number of operations.

Before this can become a truly generic operation the submatrix specification needs to be made more generic.

computeHouseholder

public static double computeHouseholder(double[] x,
 int xStart,
 int xEnd,
 double max,
 DScalar gamma)

Creates a householder reflection. (I-gamma*v*v')*x = tau*e1

NOTE: Same as cs_house in csparse

Parameters:

x - (Input) Vector x (Output) Vector v. Modified.

xStart - First index in X that is to be processed

xEnd - Last + 1 index in x that is to be processed.

gamma - (Output) Storage for computed gamma

Returns:

variable tau