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
|
/* ========================================================================== */
/* === UMF_scale ============================================================ */
/* ========================================================================== */
/* -------------------------------------------------------------------------- */
/* UMFPACK Version 4.1 (Apr. 30, 2003), Copyright (c) 2003 by Timothy A. */
/* Davis. All Rights Reserved. See ../README for License. */
/* email: davis@cise.ufl.edu CISE Department, Univ. of Florida. */
/* web: http://www.cise.ufl.edu/research/sparse/umfpack */
/* -------------------------------------------------------------------------- */
/* Divide a vector of stride 1 by the pivot value. */
#include "umf_internal.h"
GLOBAL void UMF_scale
(
Int n,
Entry pivot,
Entry X [ ]
)
{
Int i ;
Entry x ;
double s ;
/* ---------------------------------------------------------------------- */
/* compute the approximate absolute value of the pivot, and select method */
/* ---------------------------------------------------------------------- */
APPROX_ABS (s, pivot) ;
if (s < RECIPROCAL_TOLERANCE || IS_NAN (pivot))
{
/* ------------------------------------------------------------------ */
/* tiny, or zero, pivot case */
/* ------------------------------------------------------------------ */
/* The pivot is tiny, or NaN. Do not divide zero by the pivot value,
* and do not multiply by 1/pivot, either. */
for (i = 0 ; i < n ; i++)
{
/* X [i] /= pivot ; */
x = X [i] ;
if (IS_NONZERO (x))
{
DIV (X [i], x, pivot) ;
}
}
}
else
{
/* ------------------------------------------------------------------ */
/* normal case. select the x/pivot or x * (1/pivot) method */
/* ------------------------------------------------------------------ */
/* The pivot is not tiny, and is not NaN. Don't bother to check for
* zeros in the pivot column, X. */
#if !defined (NRECIPROCAL) && !(defined (__GNUC__) && defined (COMPLEX))
/* -------------------------------------------------------------- */
/* multiply x by (1/pivot) */
/* -------------------------------------------------------------- */
/* Slightly less accurate, but faster. It allows the use of
* the level-1 BLAS dscal or zscal routine. This not used when
* UMFPACK is used in MATLAB (either as a built-in routine, or as
* a mexFunction).
*
* Using gcc version 3.2 can cause the following code to fail for
* some complex matrices (not all), with or without the BLAS. This
* was found in Red Hat Linux 7.3 on a Dell Latitude C840 with a
* Pentium 4M. Thus, this code is not used when gcc is used, for
* the complex case.
*
* It works just fine with Intel's icc compiler, version 7.0.
*/
/* pivot = 1 / pivot */
RECIPROCAL (pivot) ;
#if defined (USE_NO_BLAS)
for (i = 0 ; i < n ; i++)
{
/* X [i] *= pivot ; */
x = X [i] ;
MULT (X [i], x, pivot) ;
}
#else
BLAS_SCAL (n, pivot, X) ;
#endif
#else
/* -------------------------------------------------------------- */
/* divide x by the pivot */
/* -------------------------------------------------------------- */
/* This is slightly more accurate, particularly if the pivot column
* consists of only IEEE subnormals. Always do this if UMFPACK is
* being compiled as a built-in routine or mexFunction in MATLAB,
* or if gcc is being used with complex matrices. */
for (i = 0 ; i < n ; i++)
{
/* X [i] /= pivot ; */
x = X [i] ;
DIV (X [i], x, pivot) ;
}
#endif
}
}
|
