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/* slarrc.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 slarrc_(char *jobt, integer *n, real *vl, real *vu, real
*d__, real *e, real *pivmin, integer *eigcnt, integer *lcnt, integer *
rcnt, integer *info)
{
/* System generated locals */
integer i__1;
real r__1;
/* Local variables */
integer i__;
real sl, su, tmp, tmp2;
logical matt;
extern logical lsame_(char *, char *);
real 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.f) {
++(*lcnt);
}
if (rpivot <= 0.f) {
++(*rcnt);
}
i__1 = *n - 1;
for (i__ = 1; i__ <= i__1; ++i__) {
/* Computing 2nd power */
r__1 = e[i__];
tmp = r__1 * r__1;
lpivot = d__[i__ + 1] - *vl - tmp / lpivot;
rpivot = d__[i__ + 1] - *vu - tmp / rpivot;
if (lpivot <= 0.f) {
++(*lcnt);
}
if (rpivot <= 0.f) {
++(*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.f) {
++(*lcnt);
}
if (rpivot <= 0.f) {
++(*rcnt);
}
tmp = e[i__] * d__[i__] * e[i__];
tmp2 = tmp / lpivot;
if (tmp2 == 0.f) {
sl = tmp - *vl;
} else {
sl = sl * tmp2 - *vl;
}
tmp2 = tmp / rpivot;
if (tmp2 == 0.f) {
su = tmp - *vu;
} else {
su = su * tmp2 - *vu;
}
/* L20: */
}
lpivot = d__[*n] + sl;
rpivot = d__[*n] + su;
if (lpivot <= 0.f) {
++(*lcnt);
}
if (rpivot <= 0.f) {
++(*rcnt);
}
}
*eigcnt = *rcnt - *lcnt;
return 0;
/* end of SLARRC */
} /* slarrc_ */
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