#include "f2c.h"

/* Subroutine */ int slartg_(real *f, real *g, real *cs, real *sn, real *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   

    =======   

    SLARTG 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 SROTG,   

    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 SBDSQR when   

          there are zeros on the diagonal).   

    If F exceeds G in magnitude, CS will be positive.   

    Arguments   

    =========   

    F       (input) REAL   

            The first component of vector to be rotated.   

    G       (input) REAL   

            The second component of vector to be rotated.   

    CS      (output) REAL   

            The cosine of the rotation.   

    SN      (output) REAL   

            The sine of the rotation.   

    R       (output) REAL   

            The nonzero component of the rotated vector.   

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

*/

    /* Initialized data */

    static logical first = TRUE_;

    /* System generated locals */

    integer i__1;

    real r__1, r__2;

    /* Builtin functions */

    double log(doublereal), pow_ri(real *, integer *), sqrt(doublereal);

    /* Local variables */

    static integer i;

    static real scale;

    static integer count;

    static real f1, g1, safmn2, safmx2;

    extern float slamch_(char *);

    static real safmin, eps;

    if (first) {

	first = FALSE_;

	safmin = slamch_("S");

	eps = slamch_("E");

	r__1 = slamch_("B");

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

	safmn2 = pow_ri(&r__1, &i__1);

	safmx2 = 1.f / safmn2;

    }

    if (*g == 0.f) {

	*cs = 1.f;

	*sn = 0.f;

	*r = *f;

    } else if (*f == 0.f) {

	*cs = 0.f;

	*sn = 1.f;

	*r = *g;

    } else {

	f1 = *f;

	g1 = *g;

/* Computing MAX */

	r__1 = dabs(f1), r__2 = dabs(g1);

	scale = dmax(r__1,r__2);

	if (scale >= safmx2) {

	    count = 0;

L10:

	    ++count;

	    f1 *= safmn2;

	    g1 *= safmn2;

/* Computing MAX */

	    r__1 = dabs(f1), r__2 = dabs(g1);

	    scale = dmax(r__1,r__2);

	    if (scale >= safmx2) {

		goto L10;

	    }

/* Computing 2nd power */

	    r__1 = f1;

/* Computing 2nd power */

	    r__2 = g1;

	    *r = sqrt(r__1 * r__1 + r__2 * r__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 */

	    r__1 = dabs(f1), r__2 = dabs(g1);

	    scale = dmax(r__1,r__2);

	    if (scale <= safmn2) {

		goto L30;

	    }

/* Computing 2nd power */

	    r__1 = f1;

/* Computing 2nd power */

	    r__2 = g1;

	    *r = sqrt(r__1 * r__1 + r__2 * r__2);

	    *cs = f1 / *r;

	    *sn = g1 / *r;

	    i__1 = count;

	    for (i = 1; i <= count; ++i) {

		*r *= safmn2;

/* L40: */

	    }

	} else {

/* Computing 2nd power */

	    r__1 = f1;

/* Computing 2nd power */

	    r__2 = g1;

	    *r = sqrt(r__1 * r__1 + r__2 * r__2);

	    *cs = f1 / *r;

	    *sn = g1 / *r;

	}

	if (dabs(*f) > dabs(*g) && *cs < 0.f) {

	    *cs = -(doublereal)(*cs);

	    *sn = -(doublereal)(*sn);

	    *r = -(doublereal)(*r);

	}

    }

    return 0;

/*     End of SLARTG */

} /* slartg_ */