lapack/dlapy3.c

/* dlapy3.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 "blaswrap.h"
#include "lapack_datatypes.h"

doublereal dlapy3_(doublereal *x, doublereal *y, doublereal *z__)
{
    /* System generated locals */
    doublereal ret_val, d__1, d__2, d__3;

    /* Builtin functions */
    double sqrt(doublereal);

    /* Local variables */
    doublereal w, xabs, yabs, zabs;


/*  -- LAPACK auxiliary routine (version 3.2) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
/*     November 2006 */

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

/*  Purpose */
/*  ======= */

/*  DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause */
/*  unnecessary overflow. */

/*  Arguments */
/*  ========= */

/*  X       (input) DOUBLE PRECISION */
/*  Y       (input) DOUBLE PRECISION */
/*  Z       (input) DOUBLE PRECISION */
/*          X, Y and Z specify the values x, y and z. */

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

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

    xabs = abs(*x);
    yabs = abs(*y);
    zabs = abs(*z__);
/* Computing MAX */
    d__1 = max(xabs,yabs);
    w = max(d__1,zabs);
    if (w == 0.) {
/*     W can be zero for max(0,nan,0) */
/*     adding all three entries together will make sure */
/*     NaN will not disappear. */
	ret_val = xabs + yabs + zabs;
    } else {
/* Computing 2nd power */
	d__1 = xabs / w;
/* Computing 2nd power */
	d__2 = yabs / w;
/* Computing 2nd power */
	d__3 = zabs / w;
	ret_val = w * sqrt(d__1 * d__1 + d__2 * d__2 + d__3 * d__3);
    }
    return ret_val;

/*     End of DLAPY3 */

} /* dlapy3_ */