#include "f2c.h"

/* Subroutine */ int dlartg_(doublereal *f, doublereal *g, doublereal *cs, 

	doublereal *sn, doublereal *r)

{

/*  -- LAPACK auxiliary routine (version 2.0) --   

       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   

       Courant Institute, Argonne National Lab, and Rice University   

       September 30, 1994   

    Purpose   

    =======   

    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.   

    Arguments   

    =========   

    F       (input) DOUBLE PRECISION   

            The first component of vector to be rotated.   

    G       (input) DOUBLE PRECISION   

            The second component of vector to be rotated.   

    CS      (output) DOUBLE PRECISION   

            The cosine of the rotation.   

    SN      (output) DOUBLE PRECISION   

            The sine of the rotation.   

    R       (output) DOUBLE PRECISION   

            The nonzero component of the rotated vector.   

    ===================================================================== 

*/

    /* Initialized data */

    static logical first = TRUE_;

    /* System generated locals */

    integer i__1;

    doublereal d__1, d__2;

    /* Builtin functions */

    double log(doublereal), pow_di(doublereal *, integer *), sqrt(doublereal);

    /* Local variables */

    static integer i;

    static doublereal scale;

    static integer count;

    static doublereal f1, g1, safmn2, safmx2;

    extern doublereal dlamch_(char *);

    static doublereal safmin, eps;

    if (first) {

	first = FALSE_;

	safmin = dlamch_("S");

	eps = dlamch_("E");

	d__1 = dlamch_("B");

	i__1 = (integer) (log(safmin / eps) / log(dlamch_("B")) / 2.);

	safmn2 = pow_di(&d__1, &i__1);

	safmx2 = 1. / safmn2;

    }

    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 <= count; ++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 <= count; ++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_ */