aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/clapack/dlarrc.c
blob: ac08bff9da9d0ba86b98dc06d17092a31539112d (plain) (blame)
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
/* dlarrc.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"

/* Subroutine */ int dlarrc_(char *jobt, integer *n, doublereal *vl, 
	doublereal *vu, doublereal *d__, doublereal *e, doublereal *pivmin, 
	integer *eigcnt, integer *lcnt, integer *rcnt, integer *info)
{
    /* System generated locals */
    integer i__1;
    doublereal d__1;

    /* Local variables */
    integer i__;
    doublereal sl, su, tmp, tmp2;
    logical matt;
    extern logical lsame_(char *, char *);
    doublereal lpivot, rpivot;


/*  -- LAPACK auxiliary routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

/*     .. Scalar Arguments .. */
/*     .. */
/*     .. Array Arguments .. */
/*     .. */

/*  Purpose */
/*  ======= */

/*  Find the number of eigenvalues of the symmetric tridiagonal matrix T */
/*  that are in the interval (VL,VU] if JOBT = 'T', and of L D L^T */
/*  if JOBT = 'L'. */

/*  Arguments */
/*  ========= */

/*  JOBT    (input) CHARACTER*1 */
/*          = 'T':  Compute Sturm count for matrix T. */
/*          = 'L':  Compute Sturm count for matrix L D L^T. */

/*  N       (input) INTEGER */
/*          The order of the matrix. N > 0. */

/*  VL      (input) DOUBLE PRECISION */
/*  VU      (input) DOUBLE PRECISION */
/*          The lower and upper bounds for the eigenvalues. */

/*  D       (input) DOUBLE PRECISION array, dimension (N) */
/*          JOBT = 'T': The N diagonal elements of the tridiagonal matrix T. */
/*          JOBT = 'L': The N diagonal elements of the diagonal matrix D. */

/*  E       (input) DOUBLE PRECISION array, dimension (N) */
/*          JOBT = 'T': The N-1 offdiagonal elements of the matrix T. */
/*          JOBT = 'L': The N-1 offdiagonal elements of the matrix L. */

/*  PIVMIN  (input) DOUBLE PRECISION */
/*          The minimum pivot in the Sturm sequence for T. */

/*  EIGCNT  (output) INTEGER */
/*          The number of eigenvalues of the symmetric tridiagonal matrix T */
/*          that are in the interval (VL,VU] */

/*  LCNT    (output) INTEGER */
/*  RCNT    (output) INTEGER */
/*          The left and right negcounts of the interval. */

/*  INFO    (output) INTEGER */

/*  Further Details */
/*  =============== */

/*  Based on contributions by */
/*     Beresford Parlett, University of California, Berkeley, USA */
/*     Jim Demmel, University of California, Berkeley, USA */
/*     Inderjit Dhillon, University of Texas, Austin, USA */
/*     Osni Marques, LBNL/NERSC, USA */
/*     Christof Voemel, University of California, Berkeley, USA */

/*  ===================================================================== */

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. Executable Statements .. */

    /* Parameter adjustments */
    --e;
    --d__;

    /* Function Body */
    *info = 0;
    *lcnt = 0;
    *rcnt = 0;
    *eigcnt = 0;
    matt = lsame_(jobt, "T");
    if (matt) {
/*        Sturm sequence count on T */
	lpivot = d__[1] - *vl;
	rpivot = d__[1] - *vu;
	if (lpivot <= 0.) {
	    ++(*lcnt);
	}
	if (rpivot <= 0.) {
	    ++(*rcnt);
	}
	i__1 = *n - 1;
	for (i__ = 1; i__ <= i__1; ++i__) {
/* Computing 2nd power */
	    d__1 = e[i__];
	    tmp = d__1 * d__1;
	    lpivot = d__[i__ + 1] - *vl - tmp / lpivot;
	    rpivot = d__[i__ + 1] - *vu - tmp / rpivot;
	    if (lpivot <= 0.) {
		++(*lcnt);
	    }
	    if (rpivot <= 0.) {
		++(*rcnt);
	    }
/* L10: */
	}
    } else {
/*        Sturm sequence count on L D L^T */
	sl = -(*vl);
	su = -(*vu);
	i__1 = *n - 1;
	for (i__ = 1; i__ <= i__1; ++i__) {
	    lpivot = d__[i__] + sl;
	    rpivot = d__[i__] + su;
	    if (lpivot <= 0.) {
		++(*lcnt);
	    }
	    if (rpivot <= 0.) {
		++(*rcnt);
	    }
	    tmp = e[i__] * d__[i__] * e[i__];

	    tmp2 = tmp / lpivot;
	    if (tmp2 == 0.) {
		sl = tmp - *vl;
	    } else {
		sl = sl * tmp2 - *vl;
	    }

	    tmp2 = tmp / rpivot;
	    if (tmp2 == 0.) {
		su = tmp - *vu;
	    } else {
		su = su * tmp2 - *vu;
	    }
/* L20: */
	}
	lpivot = d__[*n] + sl;
	rpivot = d__[*n] + su;
	if (lpivot <= 0.) {
	    ++(*lcnt);
	}
	if (rpivot <= 0.) {
	    ++(*rcnt);
	}
    }
    *eigcnt = *rcnt - *lcnt;
    return 0;

/*     end of DLARRC */

} /* dlarrc_ */