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
|
/** \file opennl/superlu/spivotL.c
* \ingroup opennl
*/
/*
* -- SuperLU routine (version 3.0) --
* Univ. of California Berkeley, Xerox Palo Alto Research Center,
* and Lawrence Berkeley National Lab.
* October 15, 2003
*
*/
/*
Copyright (c) 1994 by Xerox Corporation. All rights reserved.
THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
Permission is hereby granted to use or copy this program for any
purpose, provided the above notices are retained on all copies.
Permission to modify the code and to distribute modified code is
granted, provided the above notices are retained, and a notice that
the code was modified is included with the above copyright notice.
*/
#include <math.h>
#include <stdlib.h>
#include "ssp_defs.h"
#undef DEBUG
int
spivotL(
const int jcol, /* in */
const double u, /* in - diagonal pivoting threshold */
int *usepr, /* re-use the pivot sequence given by perm_r/iperm_r */
int *perm_r, /* may be modified */
int *iperm_r, /* in - inverse of perm_r */
int *iperm_c, /* in - used to find diagonal of Pc*A*Pc' */
int *pivrow, /* out */
GlobalLU_t *Glu, /* modified - global LU data structures */
SuperLUStat_t *stat /* output */
)
{
/*
* Purpose
* =======
* Performs the numerical pivoting on the current column of L,
* and the CDIV operation.
*
* Pivot policy:
* (1) Compute thresh = u * max_(i>=j) abs(A_ij);
* (2) IF user specifies pivot row k and abs(A_kj) >= thresh THEN
* pivot row = k;
* ELSE IF abs(A_jj) >= thresh THEN
* pivot row = j;
* ELSE
* pivot row = m;
*
* Note: If you absolutely want to use a given pivot order, then set u=0.0.
*
* Return value: 0 success;
* i > 0 U(i,i) is exactly zero.
*
*/
int fsupc; /* first column in the supernode */
int nsupc; /* no of columns in the supernode */
int nsupr; /* no of rows in the supernode */
int lptr; /* points to the starting subscript of the supernode */
int pivptr, old_pivptr, diag, diagind;
double pivmax, rtemp, thresh;
double temp;
double *lu_sup_ptr;
double *lu_col_ptr;
int *lsub_ptr;
int isub, icol, k, itemp;
int *lsub, *xlsub;
double *lusup;
int *xlusup;
flops_t *ops = stat->ops;
/* Initialize pointers */
lsub = Glu->lsub;
xlsub = Glu->xlsub;
lusup = Glu->lusup;
xlusup = Glu->xlusup;
fsupc = (Glu->xsup)[(Glu->supno)[jcol]];
nsupc = jcol - fsupc; /* excluding jcol; nsupc >= 0 */
lptr = xlsub[fsupc];
nsupr = xlsub[fsupc+1] - lptr;
lu_sup_ptr = &lusup[xlusup[fsupc]]; /* start of the current supernode */
lu_col_ptr = &lusup[xlusup[jcol]]; /* start of jcol in the supernode */
lsub_ptr = &lsub[lptr]; /* start of row indices of the supernode */
#ifdef DEBUG
if ( jcol == MIN_COL ) {
printf("Before cdiv: col %d\n", jcol);
for (k = nsupc; k < nsupr; k++)
printf(" lu[%d] %f\n", lsub_ptr[k], lu_col_ptr[k]);
}
#endif
/* Determine the largest abs numerical value for partial pivoting;
Also search for user-specified pivot, and diagonal element. */
if ( *usepr ) *pivrow = iperm_r[jcol];
diagind = iperm_c[jcol];
pivmax = 0.0;
pivptr = nsupc;
diag = EMPTY;
old_pivptr = nsupc;
for (isub = nsupc; isub < nsupr; ++isub) {
rtemp = fabs (lu_col_ptr[isub]);
if ( rtemp > pivmax ) {
pivmax = rtemp;
pivptr = isub;
}
if ( *usepr && lsub_ptr[isub] == *pivrow ) old_pivptr = isub;
if ( lsub_ptr[isub] == diagind ) diag = isub;
}
/* Test for singularity */
if ( pivmax == 0.0 ) {
*pivrow = lsub_ptr[pivptr];
perm_r[*pivrow] = jcol;
*usepr = 0;
return (jcol+1);
}
thresh = u * pivmax;
/* Choose appropriate pivotal element by our policy. */
if ( *usepr ) {
rtemp = fabs (lu_col_ptr[old_pivptr]);
if ( rtemp != 0.0 && rtemp >= thresh )
pivptr = old_pivptr;
else
*usepr = 0;
}
if ( *usepr == 0 ) {
/* Use diagonal pivot? */
if ( diag >= 0 ) { /* diagonal exists */
rtemp = fabs (lu_col_ptr[diag]);
if ( rtemp != 0.0 && rtemp >= thresh ) pivptr = diag;
}
*pivrow = lsub_ptr[pivptr];
}
/* Record pivot row */
perm_r[*pivrow] = jcol;
/* Interchange row subscripts */
if ( pivptr != nsupc ) {
itemp = lsub_ptr[pivptr];
lsub_ptr[pivptr] = lsub_ptr[nsupc];
lsub_ptr[nsupc] = itemp;
/* Interchange numerical values as well, for the whole snode, such
* that L is indexed the same way as A.
*/
for (icol = 0; icol <= nsupc; icol++) {
itemp = pivptr + icol * nsupr;
temp = lu_sup_ptr[itemp];
lu_sup_ptr[itemp] = lu_sup_ptr[nsupc + icol*nsupr];
lu_sup_ptr[nsupc + icol*nsupr] = temp;
}
} /* if */
/* cdiv operation */
ops[FACT] += nsupr - nsupc;
temp = 1.0 / lu_col_ptr[nsupc];
for (k = nsupc+1; k < nsupr; k++)
lu_col_ptr[k] *= temp;
return 0;
}
|
