text: /* slartg.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"
  
  /* Subroutine */ int slartg_(real *f, real *g, real *cs, real *sn, real *r__)
  {
      /* System generated locals */
      integer i__1;
      real r__1, r__2;
  
      /* Builtin functions */
      double log(doublereal), pow_ri(real *, integer *), sqrt(doublereal);
  
      /* Local variables */
      integer i__;
      real f1, g1, eps, scale;
      integer count;
      real safmn2, safmx2;
      extern doublereal slamch_(char *);
      real safmin;
  
  
  /*  -- LAPACK auxiliary routine (version 3.2) -- */
  /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
  /*     November 2006 */
  
  /*     .. Scalar Arguments .. */
  /*     .. */
  
  /*  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. */
  
  /*  This version has a few statements commented out for thread safety */
  /*  (machine parameters are computed on each entry). 10 feb 03, SJH. */
  
  /*  ===================================================================== */
  
  /*     .. 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 = 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;
  /*        FIRST = .FALSE. */
  /*     END IF */
      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__ <= i__1; ++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__ <= i__1; ++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 = -(*cs);
  	    *sn = -(*sn);
  	    *r__ = -(*r__);
  	}
      }
      return 0;
  
  /*     End of SLARTG */
  
  } /* slartg_ */
  