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
|
/* sgesc2.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"
#include "blaswrap.h"
/* Table of constant values */
static integer c__1 = 1;
static integer c_n1 = -1;
/* Subroutine */ int sgesc2_(integer *n, real *a, integer *lda, real *rhs,
integer *ipiv, integer *jpiv, real *scale)
{
/* System generated locals */
integer a_dim1, a_offset, i__1, i__2;
real r__1, r__2;
/* Local variables */
integer i__, j;
real eps, temp;
extern /* Subroutine */ int sscal_(integer *, real *, real *, integer *),
slabad_(real *, real *);
extern doublereal slamch_(char *);
real bignum;
extern integer isamax_(integer *, real *, integer *);
extern /* Subroutine */ int slaswp_(integer *, real *, integer *, integer
*, integer *, integer *, integer *);
real smlnum;
/* -- LAPACK auxiliary routine (version 3.2) -- */
/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/* November 2006 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SGESC2 solves a system of linear equations */
/* A * X = scale* RHS */
/* with a general N-by-N matrix A using the LU factorization with */
/* complete pivoting computed by SGETC2. */
/* Arguments */
/* ========= */
/* N (input) INTEGER */
/* The order of the matrix A. */
/* A (input) REAL array, dimension (LDA,N) */
/* On entry, the LU part of the factorization of the n-by-n */
/* matrix A computed by SGETC2: A = P * L * U * Q */
/* LDA (input) INTEGER */
/* The leading dimension of the array A. LDA >= max(1, N). */
/* RHS (input/output) REAL array, dimension (N). */
/* On entry, the right hand side vector b. */
/* On exit, the solution vector X. */
/* IPIV (input) INTEGER array, dimension (N). */
/* The pivot indices; for 1 <= i <= N, row i of the */
/* matrix has been interchanged with row IPIV(i). */
/* JPIV (input) INTEGER array, dimension (N). */
/* The pivot indices; for 1 <= j <= N, column j of the */
/* matrix has been interchanged with column JPIV(j). */
/* SCALE (output) REAL */
/* On exit, SCALE contains the scale factor. SCALE is chosen */
/* 0 <= SCALE <= 1 to prevent owerflow in the solution. */
/* Further Details */
/* =============== */
/* Based on contributions by */
/* Bo Kagstrom and Peter Poromaa, Department of Computing Science, */
/* Umea University, S-901 87 Umea, Sweden. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Subroutines .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Set constant to control owerflow */
/* Parameter adjustments */
a_dim1 = *lda;
a_offset = 1 + a_dim1;
a -= a_offset;
--rhs;
--ipiv;
--jpiv;
/* Function Body */
eps = slamch_("P");
smlnum = slamch_("S") / eps;
bignum = 1.f / smlnum;
slabad_(&smlnum, &bignum);
/* Apply permutations IPIV to RHS */
i__1 = *n - 1;
slaswp_(&c__1, &rhs[1], lda, &c__1, &i__1, &ipiv[1], &c__1);
/* Solve for L part */
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
i__2 = *n;
for (j = i__ + 1; j <= i__2; ++j) {
rhs[j] -= a[j + i__ * a_dim1] * rhs[i__];
/* L10: */
}
/* L20: */
}
/* Solve for U part */
*scale = 1.f;
/* Check for scaling */
i__ = isamax_(n, &rhs[1], &c__1);
if (smlnum * 2.f * (r__1 = rhs[i__], dabs(r__1)) > (r__2 = a[*n + *n *
a_dim1], dabs(r__2))) {
temp = .5f / (r__1 = rhs[i__], dabs(r__1));
sscal_(n, &temp, &rhs[1], &c__1);
*scale *= temp;
}
for (i__ = *n; i__ >= 1; --i__) {
temp = 1.f / a[i__ + i__ * a_dim1];
rhs[i__] *= temp;
i__1 = *n;
for (j = i__ + 1; j <= i__1; ++j) {
rhs[i__] -= rhs[j] * (a[i__ + j * a_dim1] * temp);
/* L30: */
}
/* L40: */
}
/* Apply permutations JPIV to the solution (RHS) */
i__1 = *n - 1;
slaswp_(&c__1, &rhs[1], lda, &c__1, &i__1, &jpiv[1], &c_n1);
return 0;
/* End of SGESC2 */
} /* sgesc2_ */
|
