dlartgs.f man page

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 precisionX, double precisionY, double precisionSIGMA, double precisionCS, double precisionSN)

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:

September 2012

Definition at line 91 of file dlartgs.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

dlartgs(3) is an alias of dlartgs.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK