slartgs.f man page

slartgs.f —

Synopsis

Functions/Subroutines

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.

Function/Subroutine Documentation

subroutine slartgs (realX, realY, realSIGMA, realCS, realSN)

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  ]  .  [ 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 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.

Date:

September 2012

Definition at line 91 of file slartgs.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

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

Sat Nov 16 2013 Version 3.4.2 LAPACK