subroutine dlartgp (F, G, CS, SN, R)
DLARTGP generates a plane rotation so that the diagonal is nonnegative.
DLARTGP generates a plane rotation so that the diagonal is nonnegative.
Purpose:
DLARTGP generates a plane rotation so that
[ CS SN ] . [ F ] = [ R ] where CS**2 + SN**2 = 1.
[ -SN CS ] [ G ] [ 0 ]
This is a slower, more accurate version of the Level 1 BLAS 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.
The sign is chosen so that R >= 0.
Parameters:
F is DOUBLE PRECISION
The first component of vector to be rotated.
G
G is DOUBLE PRECISION
The second component of vector to be rotated.
CS
CS is DOUBLE PRECISION
The cosine of the rotation.
SN
SN is DOUBLE PRECISION
The sine of the rotation.
R
R is 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.
Author:
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
Definition at line 97 of file dlartgp.f.
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