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
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
/* ../../../dependencies/lapack/src/dlartg.f -- translated by f2c (version 20061008).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
#include "f2c.h"
/* Subroutine */ int dlartg_(doublereal *f, doublereal *g, doublereal *cs,
doublereal *sn, doublereal *r__)
{
/* Initialized data */
static logical first = TRUE_;
/* System generated locals */
integer i__1;
doublereal d__1, d__2;
/* Builtin functions */
double log(doublereal), pow_di(doublereal *, integer *), sqrt(doublereal);
/* Local variables */
static integer i__;
static doublereal f1, g1, eps, scale;
static integer count;
static doublereal safmn2, safmx2;
extern doublereal dlamch_(char *, ftnlen);
static doublereal safmin;
/* -- LAPACK auxiliary routine (version 3.0) -- */
/* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/* Courant Institute, Argonne National Lab, and Rice University */
/* September 30, 1994 */
/* .. Scalar Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* DLARTG generate 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 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. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Save statement .. */
/* .. */
/* .. Data statements .. */
/* .. */
/* .. Executable Statements .. */
if (first) {
first = FALSE_;
safmin = dlamch_("S", (ftnlen)1);
eps = dlamch_("E", (ftnlen)1);
d__1 = dlamch_("B", (ftnlen)1);
i__1 = (integer) (log(safmin / eps) / log(dlamch_("B", (ftnlen)1)) /
2.);
safmn2 = pow_di(&d__1, &i__1);
safmx2 = 1. / safmn2;
}
if (*g == 0.) {
*cs = 1.;
*sn = 0.;
*r__ = *f;
} else if (*f == 0.) {
*cs = 0.;
*sn = 1.;
*r__ = *g;
} else {
f1 = *f;
g1 = *g;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale >= safmx2) {
count = 0;
L10:
++count;
f1 *= safmn2;
g1 *= safmn2;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale >= safmx2) {
goto L10;
}
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmx2;
/* L20: */
}
} else if (scale <= safmn2) {
count = 0;
L30:
++count;
f1 *= safmx2;
g1 *= safmx2;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale <= safmn2) {
goto L30;
}
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmn2;
/* L40: */
}
} else {
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
}
if (abs(*f) > abs(*g) && *cs < 0.) {
*cs = -(*cs);
*sn = -(*sn);
*r__ = -(*r__);
}
}
return 0;
/* End of DLARTG */
} /* dlartg_ */
|
