dlartgs.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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NAME

dlartgs.f  

SYNOPSIS


 

Functions/Subroutines


subroutine dlartgs (X, Y, SIGMA, CS, SN)
DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.  

Function/Subroutine Documentation

 

subroutine dlartgs (double precision X, double precision Y, double precision SIGMA, double precision CS, double precision SN)

DLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

Purpose: 

 DLARTGS generates a plane rotation designed to introduce a bulge in
 Golub-Reinsch-style implicit QR iteration for the bidiagonal SVD
 problem. X and Y are the top-row entries, and SIGMA is the shift.
 The computed CS and SN define a plane rotation satisfying

    [  CS  SN  ]  .  [ X^2 - SIGMA ]  =  [ R ],
    [ -SN  CS  ]     [    X * Y    ]     [ 0 ]

 with R nonnegative.  If X^2 - SIGMA and X * Y are 0, then the
 rotation is by PI/2.


 

Parameters:

X 

          X is DOUBLE PRECISION
          The (1,1) entry of an upper bidiagonal matrix.


Y 

          Y is DOUBLE PRECISION
          The (1,2) entry of an upper bidiagonal matrix.


SIGMA 

          SIGMA is DOUBLE PRECISION
          The shift.


CS 

          CS is DOUBLE PRECISION
          The cosine of the rotation.


SN 

          SN is DOUBLE PRECISION
          The sine of the rotation.


 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2017

Definition at line 92 of file dlartgs.f.  

Author

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Index

NAME
SYNOPSIS
Functions/Subroutines
Function/Subroutine Documentation
subroutine dlartgs (double precision X, double precision Y, double precision SIGMA, double precision CS, double precision SN)
Author