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/* ../../../dependencies/lapack/src/slasq6.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"
/* Subroutine */ int slasq6_(integer *i0, integer *n0, real *z__, integer *pp,
real *dmin__, real *dmin1, real *dmin2, real *dn, real *dnm1, real *
dnm2)
{
/* System generated locals */
integer i__1;
real r__1, r__2;
/* Local variables */
static real d__;
static integer j4, j4p2;
static real emin, temp;
extern doublereal slamch_(char *, ftnlen);
static real safmin;
/* -- LAPACK auxiliary routine (version 3.0) -- */
/* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/* Courant Institute, Argonne National Lab, and Rice University */
/* October 31, 1999 */
/* .. Scalar Arguments .. */
/* .. */
/* .. Array Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SLASQ6 computes one dqd (shift equal to zero) transform in */
/* ping-pong form, with protection against underflow and overflow. */
/* Arguments */
/* ========= */
/* I0 (input) INTEGER */
/* First index. */
/* N0 (input) INTEGER */
/* Last index. */
/* Z (input) REAL array, dimension ( 4*N ) */
/* Z holds the qd array. EMIN is stored in Z(4*N0) to avoid */
/* an extra argument. */
/* PP (input) INTEGER */
/* PP=0 for ping, PP=1 for pong. */
/* DMIN (output) REAL */
/* Minimum value of d. */
/* DMIN1 (output) REAL */
/* Minimum value of d, excluding D( N0 ). */
/* DMIN2 (output) REAL */
/* Minimum value of d, excluding D( N0 ) and D( N0-1 ). */
/* DN (output) REAL */
/* d(N0), the last value of d. */
/* DNM1 (output) REAL */
/* d(N0-1). */
/* DNM2 (output) REAL */
/* d(N0-2). */
/* ===================================================================== */
/* .. Parameter .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Function .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Executable Statements .. */
/* Parameter adjustments */
--z__;
/* Function Body */
if (*n0 - *i0 - 1 <= 0) {
return 0;
}
safmin = slamch_("Safe minimum", (ftnlen)12);
j4 = (*i0 << 2) + *pp - 3;
emin = z__[j4 + 4];
d__ = z__[j4];
*dmin__ = d__;
if (*pp == 0) {
i__1 = *n0 - 3 << 2;
for (j4 = *i0 << 2; j4 <= i__1; j4 += 4) {
z__[j4 - 2] = d__ + z__[j4 - 1];
if (z__[j4 - 2] == 0.f) {
z__[j4] = 0.f;
d__ = z__[j4 + 1];
*dmin__ = d__;
emin = 0.f;
} else if (safmin * z__[j4 + 1] < z__[j4 - 2] && safmin * z__[j4
- 2] < z__[j4 + 1]) {
temp = z__[j4 + 1] / z__[j4 - 2];
z__[j4] = z__[j4 - 1] * temp;
d__ *= temp;
} else {
z__[j4] = z__[j4 + 1] * (z__[j4 - 1] / z__[j4 - 2]);
d__ = z__[j4 + 1] * (d__ / z__[j4 - 2]);
}
*dmin__ = dmin(*dmin__,d__);
/* Computing MIN */
r__1 = emin, r__2 = z__[j4];
emin = dmin(r__1,r__2);
/* L10: */
}
} else {
i__1 = *n0 - 3 << 2;
for (j4 = *i0 << 2; j4 <= i__1; j4 += 4) {
z__[j4 - 3] = d__ + z__[j4];
if (z__[j4 - 3] == 0.f) {
z__[j4 - 1] = 0.f;
d__ = z__[j4 + 2];
*dmin__ = d__;
emin = 0.f;
} else if (safmin * z__[j4 + 2] < z__[j4 - 3] && safmin * z__[j4
- 3] < z__[j4 + 2]) {
temp = z__[j4 + 2] / z__[j4 - 3];
z__[j4 - 1] = z__[j4] * temp;
d__ *= temp;
} else {
z__[j4 - 1] = z__[j4 + 2] * (z__[j4] / z__[j4 - 3]);
d__ = z__[j4 + 2] * (d__ / z__[j4 - 3]);
}
*dmin__ = dmin(*dmin__,d__);
/* Computing MIN */
r__1 = emin, r__2 = z__[j4 - 1];
emin = dmin(r__1,r__2);
/* L20: */
}
}
/* Unroll last two steps. */
*dnm2 = d__;
*dmin2 = *dmin__;
j4 = (*n0 - 2 << 2) - *pp;
j4p2 = j4 + (*pp << 1) - 1;
z__[j4 - 2] = *dnm2 + z__[j4p2];
if (z__[j4 - 2] == 0.f) {
z__[j4] = 0.f;
*dnm1 = z__[j4p2 + 2];
*dmin__ = *dnm1;
emin = 0.f;
} else if (safmin * z__[j4p2 + 2] < z__[j4 - 2] && safmin * z__[j4 - 2] <
z__[j4p2 + 2]) {
temp = z__[j4p2 + 2] / z__[j4 - 2];
z__[j4] = z__[j4p2] * temp;
*dnm1 = *dnm2 * temp;
} else {
z__[j4] = z__[j4p2 + 2] * (z__[j4p2] / z__[j4 - 2]);
*dnm1 = z__[j4p2 + 2] * (*dnm2 / z__[j4 - 2]);
}
*dmin__ = dmin(*dmin__,*dnm1);
*dmin1 = *dmin__;
j4 += 4;
j4p2 = j4 + (*pp << 1) - 1;
z__[j4 - 2] = *dnm1 + z__[j4p2];
if (z__[j4 - 2] == 0.f) {
z__[j4] = 0.f;
*dn = z__[j4p2 + 2];
*dmin__ = *dn;
emin = 0.f;
} else if (safmin * z__[j4p2 + 2] < z__[j4 - 2] && safmin * z__[j4 - 2] <
z__[j4p2 + 2]) {
temp = z__[j4p2 + 2] / z__[j4 - 2];
z__[j4] = z__[j4p2] * temp;
*dn = *dnm1 * temp;
} else {
z__[j4] = z__[j4p2 + 2] * (z__[j4p2] / z__[j4 - 2]);
*dn = z__[j4p2 + 2] * (*dnm1 / z__[j4 - 2]);
}
*dmin__ = dmin(*dmin__,*dn);
z__[j4 + 2] = *dn;
z__[(*n0 << 2) - *pp] = emin;
return 0;
/* End of SLASQ6 */
} /* slasq6_ */
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