/* Copyright (c) 1992-2008 The University of Tennessee.  All rights reserved.
 * See file COPYING in this directory for details. */

#ifdef __cplusplus
extern "C" {
#endif

#include "f2c.h"
#include "hypre_lapack.h"

/* Subroutine */ integer dlartg_(doublereal *f, doublereal *g, doublereal *cs,
	doublereal *sn, doublereal *r__)
{
/*  -- LAPACK auxiliary routine (version 3.0) --
       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 */
    logical first = TRUE_;
    /* System generated locals */
    integer i__1;
    doublereal d__1, d__2;
    /* Builtin functions */
//    doublereal log(doublereal), pow_di(doublereal *, integer *), sqrt(doublereal);
    doublereal pow_di(doublereal *, integer *);
    /* Local variables */
    integer i__;
    doublereal scale;
    integer count;
    doublereal f1, g1, safmn2, safmx2;
    extern doublereal dlamch_(const char *);
//     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.);
        i__1 = HYPRE_REAL_MIN_EXP>>1;
	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__ <= 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
