1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
|
*> \brief \b DROTG
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition
* ==========
*
* SUBROUTINE DROTG(DA,DB,C,S)
*
* .. Scalar Arguments ..
* DOUBLE PRECISION C,DA,DB,S
* ..
*
* Purpose
* =======
*
*>\details \b Purpose:
*>\verbatim
*>
*> DROTG construct givens plane rotation.
*>
*>\endverbatim
*
* Authors
* =======
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup double_blas_level1
*
*
* Further Details
* ===============
*>\details \b Further \b Details
*> \verbatim
*>
*> jack dongarra, linpack, 3/11/78.
*>
*> \endverbatim
*>
* =====================================================================
SUBROUTINE DROTG(DA,DB,C,S)
*
* -- Reference BLAS level1 routine (version 3.4.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
DOUBLE PRECISION C,DA,DB,S
* ..
*
* =====================================================================
*
* .. Local Scalars ..
DOUBLE PRECISION R,ROE,SCALE,Z
* ..
* .. Intrinsic Functions ..
INTRINSIC DABS,DSIGN,DSQRT
* ..
ROE = DB
IF (DABS(DA).GT.DABS(DB)) ROE = DA
SCALE = DABS(DA) + DABS(DB)
IF (SCALE.EQ.0.0d0) THEN
C = 1.0d0
S = 0.0d0
R = 0.0d0
Z = 0.0d0
ELSE
R = SCALE*DSQRT((DA/SCALE)**2+ (DB/SCALE)**2)
R = DSIGN(1.0d0,ROE)*R
C = DA/R
S = DB/R
Z = 1.0d0
IF (DABS(DA).GT.DABS(DB)) Z = S
IF (DABS(DB).GE.DABS(DA) .AND. C.NE.0.0d0) Z = 1.0d0/C
END IF
DA = R
DB = Z
RETURN
END
|
