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/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dlartgs.f(3) Library Functions Manual /home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/dlartgs.f(3)

NAME

/home/abuild/rpmbuild/BUILD/lapack-3.12.0/SRC/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.

Definition at line 89 of file dlartgs.f.

Author

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Version 3.12.0 LAPACK