/* fortran/dlartg.f -- translated by f2c (version 20200916).
   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
*/

#ifdef __cplusplus
extern "C" {
#endif
#include "lmp_f2c.h"

/* > \brief \b DLARTG generates a plane rotation with real cosine and real sine. */

/*  =========== DOCUMENTATION =========== */

/* Online html documentation available at */
/*            http://www.netlib.org/lapack/explore-html/ */

/* > \htmlonly */
/* > Download DLARTG + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlartg.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlartg.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlartg.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */

/*  Definition: */
/*  =========== */

/*       SUBROUTINE DLARTG( F, G, CS, SN, R ) */

/*       .. Scalar Arguments .. */
/*       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 December 2016 */

/* > \ingroup OTHERauxiliary */

/*  ===================================================================== */
/* Subroutine */ int dlartg_(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_lmp_di(doublereal *, integer *), sqrt(doublereal);

    /* Local variables */
    integer i__;
    doublereal f1, g1, eps, scale;
    integer count;
    doublereal safmn2, safmx2;
    extern doublereal dlamch_(char *, ftnlen);
    doublereal safmin;


/*  -- LAPACK auxiliary routine (version 3.7.0) -- */
/*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
/*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */
/*     December 2016 */

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

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     LOGICAL            FIRST */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Save statement .. */
/*     SAVE               FIRST, SAFMX2, SAFMIN, SAFMN2 */
/*     .. */
/*     .. Data statements .. */
/*     DATA               FIRST / .TRUE. / */
/*     .. */
/*     .. Executable Statements .. */

/*     IF( FIRST ) THEN */
    safmin = dlamch_((char *)"S", (ftnlen)1);
    eps = dlamch_((char *)"E", (ftnlen)1);
    d__1 = dlamch_((char *)"B", (ftnlen)1);
    i__1 = (integer) (log(safmin / eps) / log(dlamch_((char *)"B", (ftnlen)1)) / 2.);
    safmn2 = pow_lmp_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 */

} /* dlartg_ */

#ifdef __cplusplus
        }
#endif