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/* drotg.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"
/* Table of constant values */
static doublereal c_b4 = 1.;
/* Subroutine */ int drotg_(doublereal *da, doublereal *db, doublereal *c__,
doublereal *s)
{
/* System generated locals */
doublereal d__1, d__2;
/* Builtin functions */
double sqrt(doublereal), d_sign(doublereal *, doublereal *);
/* Local variables */
doublereal r__, z__, roe, scale;
/* .. Scalar Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* construct givens plane rotation. */
/* jack dongarra, linpack, 3/11/78. */
/* .. Local Scalars .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
roe = *db;
if (abs(*da) > abs(*db)) {
roe = *da;
}
scale = abs(*da) + abs(*db);
if (scale != 0.) {
goto L10;
}
*c__ = 1.;
*s = 0.;
r__ = 0.;
z__ = 0.;
goto L20;
L10:
/* Computing 2nd power */
d__1 = *da / scale;
/* Computing 2nd power */
d__2 = *db / scale;
r__ = scale * sqrt(d__1 * d__1 + d__2 * d__2);
r__ = d_sign(&c_b4, &roe) * r__;
*c__ = *da / r__;
*s = *db / r__;
z__ = 1.;
if (abs(*da) > abs(*db)) {
z__ = *s;
}
if (abs(*db) >= abs(*da) && *c__ != 0.) {
z__ = 1. / *c__;
}
L20:
*da = r__;
*db = z__;
return 0;
} /* drotg_ */
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