Man page - lartgs(3)

Packages contains this manual

Manual

lartgs

NAME
SYNOPSIS
Functions
Detailed Description
Function Documentation
subroutine dlartgs (double precision x, double precision y, doubleprecision sigma, double precision cs, double precision sn)
subroutine slartgs (real x, real y, real sigma, real cs, real sn)
Author

NAME

lartgs - lartgs: generate plane rotation for bidiag SVD

SYNOPSIS

Functions

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.
subroutine slartgs (x, y, sigma, cs, sn)
SLARTGS generates a plane rotation designed to introduce a bulge in implicit QR iteration for the bidiagonal SVD problem.

Detailed Description

Function Documentation

subroutine dlartgs (double precision x, double precision y, doubleprecision 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 ] . [ Xˆ2 - SIGMA ] = [ R ],
[ -SN CS ] [ X * Y ] [ 0 ]

with R nonnegative. If Xˆ2 - 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.

subroutine slartgs (real x, real y, real sigma, real cs, real sn)

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

Purpose:

SLARTGS 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 ] . [ Xˆ2 - SIGMA ] = [ R ],
[ -SN CS ] [ X * Y ] [ 0 ]

with R nonnegative. If Xˆ2 - SIGMA and X * Y are 0, then the
rotation is by PI/2.

Parameters

X

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

Y

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

SIGMA

SIGMA is REAL
The shift.

CS

CS is REAL
The cosine of the rotation.

SN

SN is REAL
The sine of the rotation.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Author

Generated automatically by Doxygen for LAPACK from the source code.