NAME
DLARTG - generate a plane rotation so that [ CS SN ]
SYNOPSIS
- SUBROUTINE DLARTG(
-
F, G, CS, SN, R )
- DOUBLE
-
PRECISION CS, F, G, R, SN
PURPOSE
DLARTG generate a plane rotation so that
[ -SN CS ] [ G ] [ 0 ]
This is a slower, more accurate version of the BLAS1 routine DROTG, with the following other differences:
F and G are unchanged on return.
If G=0, then CS=1 and SN=0.
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).
If F exceeds G in magnitude, CS will be positive.
ARGUMENTS
- F (input) DOUBLE PRECISION
-
The first component of vector to be rotated.
- G (input) DOUBLE PRECISION
-
The second component of vector to be rotated.
- CS (output) DOUBLE PRECISION
-
The cosine of the rotation.
- SN (output) DOUBLE PRECISION
-
The sine of the rotation.
- 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.