.TH DLARTG 1 "November 2006" " LAPACK auxiliary routine (version 3.1) " " LAPACK auxiliary routine (version 3.1) "
.SH NAME
DLARTG - a plane rotation so that [ CS SN ]
.SH SYNOPSIS
.TP 19
SUBROUTINE DLARTG(
F, G, CS, SN, R )
.TP 19
.ti +4
DOUBLE
PRECISION CS, F, G, R, SN
.SH PURPOSE
DLARTG generate a plane rotation so that
[ -SN CS ] [ G ] [ 0 ]
.br
This is a slower, more accurate version of the BLAS1 routine DROTG,
with the following other differences:
.br
F and G are unchanged on return.
.br
If G=0, then CS=1 and SN=0.
.br
If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any
floating point operations (saves work in DBDSQR when
there are zeros on the diagonal).
.br
If F exceeds G in magnitude, CS will be positive.
.br
.SH ARGUMENTS
.TP 8
F (input) DOUBLE PRECISION
The first component of vector to be rotated.
.TP 8
G (input) DOUBLE PRECISION
The second component of vector to be rotated.
.TP 8
CS (output) DOUBLE PRECISION
The cosine of the rotation.
.TP 8
SN (output) DOUBLE PRECISION
The sine of the rotation.
.TP 8
R (output) DOUBLE PRECISION
The nonzero component of the rotated vector.
This version has a few statements commented out for thread safety
(machine parameters are computed on each entry). 10 feb 03, SJH.