/* -- translated by f2c (version 20100827).
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*/
#include "f2c.h"
/* > \brief \b DLARTG generates a plane rotation with real cosine and real sine.
=========== DOCUMENTATION ===========
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http://www.netlib.org/lapack/explore-html/
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> \endhtmlonly
Definition:
===========
SUBROUTINE DLARTG( F, G, CS, SN, R )
DOUBLE PRECISION CS, F, G, R, SN
> \par Purpose:
=============
>
> \verbatim
>
> DLARTG generate a plane rotation so that
>
> [ CS SN ] . [ F ] = [ R ] where CS**2 + SN**2 = 1.
> [ -SN CS ] [ G ] [ 0 ]
>
> This is a slower, more accurate version of the BLAS1 routine DROTG,
> with the following other differences:
> F and G are unchanged on return.
> If G=0, then CS=1 and SN=0.
> If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any
> floating point operations (saves work in DBDSQR when
> there are zeros on the diagonal).
>
> If F exceeds G in magnitude, CS will be positive.
> \endverbatim
Arguments:
==========
> \param[in] F
> \verbatim
> F is DOUBLE PRECISION
> The first component of vector to be rotated.
> \endverbatim
>
> \param[in] G
> \verbatim
> G is DOUBLE PRECISION
> The second component of vector to be rotated.
> \endverbatim
>
> \param[out] CS
> \verbatim
> CS is DOUBLE PRECISION
> The cosine of the rotation.
> \endverbatim
>
> \param[out] SN
> \verbatim
> SN is DOUBLE PRECISION
> The sine of the rotation.
> \endverbatim
>
> \param[out] R
> \verbatim
> R is DOUBLE PRECISION
> The nonzero component of the rotated vector.
>
> This version has a few statements commented out for thread safety
> (machine parameters are computed on each entry). 10 feb 03, SJH.
> \endverbatim
Authors:
========
> \author Univ. of Tennessee
> \author Univ. of California Berkeley
> \author Univ. of Colorado Denver
> \author NAG Ltd.
> \date September 2012
> \ingroup auxOTHERauxiliary
=====================================================================
Subroutine */ int igraphdlartg_(doublereal *f, doublereal *g, doublereal *cs,
doublereal *sn, doublereal *r__)
{
/* System generated locals */
integer i__1;
doublereal d__1, d__2;
/* Builtin functions */
double log(doublereal), pow_di(doublereal *, integer *), sqrt(doublereal);
/* Local variables */
integer i__;
doublereal f1, g1, eps, scale;
integer count;
doublereal safmn2, safmx2;
extern doublereal igraphdlamch_(char *);
doublereal safmin;
/* -- LAPACK auxiliary routine (version 3.4.2) --
-- LAPACK is a software package provided by Univ. of Tennessee, --
-- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
September 2012
=====================================================================
LOGICAL FIRST
SAVE FIRST, SAFMX2, SAFMIN, SAFMN2
DATA FIRST / .TRUE. /
IF( FIRST ) THEN */
safmin = igraphdlamch_("S");
eps = igraphdlamch_("E");
d__1 = igraphdlamch_("B");
i__1 = (integer) (log(safmin / eps) / log(igraphdlamch_("B")) / 2.);
safmn2 = pow_di(&d__1, &i__1);
safmx2 = 1. / safmn2;
/* FIRST = .FALSE.
END IF */
if (*g == 0.) {
*cs = 1.;
*sn = 0.;
*r__ = *f;
} else if (*f == 0.) {
*cs = 0.;
*sn = 1.;
*r__ = *g;
} else {
f1 = *f;
g1 = *g;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale >= safmx2) {
count = 0;
L10:
++count;
f1 *= safmn2;
g1 *= safmn2;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale >= safmx2) {
goto L10;
}
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmx2;
/* L20: */
}
} else if (scale <= safmn2) {
count = 0;
L30:
++count;
f1 *= safmx2;
g1 *= safmx2;
/* Computing MAX */
d__1 = abs(f1), d__2 = abs(g1);
scale = max(d__1,d__2);
if (scale <= safmn2) {
goto L30;
}
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmn2;
/* L40: */
}
} else {
/* Computing 2nd power */
d__1 = f1;
/* Computing 2nd power */
d__2 = g1;
*r__ = sqrt(d__1 * d__1 + d__2 * d__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
}
if (abs(*f) > abs(*g) && *cs < 0.) {
*cs = -(*cs);
*sn = -(*sn);
*r__ = -(*r__);
}
}
return 0;
/* End of DLARTG */
} /* igraphdlartg_ */