2010-07-16 20:54:53 +08:00
|
|
|
/* snrm2.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
|
|
|
|
|
*/
|
|
|
|
|
|
2010-05-12 01:44:00 +08:00
|
|
|
#include "clapack.h"
|
|
|
|
|
|
2010-07-16 20:54:53 +08:00
|
|
|
|
2010-05-12 01:44:00 +08:00
|
|
|
doublereal snrm2_(integer *n, real *x, integer *incx)
|
|
|
|
|
{
|
|
|
|
|
/* System generated locals */
|
|
|
|
|
integer i__1, i__2;
|
|
|
|
|
real ret_val, r__1;
|
|
|
|
|
|
|
|
|
|
/* Builtin functions */
|
|
|
|
|
double sqrt(doublereal);
|
|
|
|
|
|
|
|
|
|
/* Local variables */
|
|
|
|
|
integer ix;
|
|
|
|
|
real ssq, norm, scale, absxi;
|
|
|
|
|
|
|
|
|
|
/* .. Scalar Arguments .. */
|
|
|
|
|
/* .. */
|
|
|
|
|
/* .. Array Arguments .. */
|
|
|
|
|
/* .. */
|
|
|
|
|
|
|
|
|
|
/* Purpose */
|
|
|
|
|
/* ======= */
|
|
|
|
|
|
|
|
|
|
/* SNRM2 returns the euclidean norm of a vector via the function */
|
|
|
|
|
/* name, so that */
|
|
|
|
|
|
|
|
|
|
/* SNRM2 := sqrt( x'*x ). */
|
|
|
|
|
|
|
|
|
|
/* Further Details */
|
|
|
|
|
/* =============== */
|
|
|
|
|
|
|
|
|
|
/* -- This version written on 25-October-1982. */
|
|
|
|
|
/* Modified on 14-October-1993 to inline the call to SLASSQ. */
|
|
|
|
|
/* Sven Hammarling, Nag Ltd. */
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
/* .. Parameters .. */
|
|
|
|
|
/* .. */
|
|
|
|
|
/* .. Local Scalars .. */
|
|
|
|
|
/* .. */
|
|
|
|
|
/* .. Intrinsic Functions .. */
|
|
|
|
|
/* .. */
|
|
|
|
|
/* Parameter adjustments */
|
|
|
|
|
--x;
|
|
|
|
|
|
|
|
|
|
/* Function Body */
|
|
|
|
|
if (*n < 1 || *incx < 1) {
|
|
|
|
|
norm = 0.f;
|
|
|
|
|
} else if (*n == 1) {
|
|
|
|
|
norm = dabs(x[1]);
|
|
|
|
|
} else {
|
|
|
|
|
scale = 0.f;
|
|
|
|
|
ssq = 1.f;
|
|
|
|
|
/* The following loop is equivalent to this call to the LAPACK */
|
|
|
|
|
/* auxiliary routine: */
|
|
|
|
|
/* CALL SLASSQ( N, X, INCX, SCALE, SSQ ) */
|
|
|
|
|
|
|
|
|
|
i__1 = (*n - 1) * *incx + 1;
|
|
|
|
|
i__2 = *incx;
|
|
|
|
|
for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
|
|
|
|
|
if (x[ix] != 0.f) {
|
|
|
|
|
absxi = (r__1 = x[ix], dabs(r__1));
|
|
|
|
|
if (scale < absxi) {
|
|
|
|
|
/* Computing 2nd power */
|
|
|
|
|
r__1 = scale / absxi;
|
|
|
|
|
ssq = ssq * (r__1 * r__1) + 1.f;
|
|
|
|
|
scale = absxi;
|
|
|
|
|
} else {
|
|
|
|
|
/* Computing 2nd power */
|
|
|
|
|
r__1 = absxi / scale;
|
|
|
|
|
ssq += r__1 * r__1;
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
/* L10: */
|
|
|
|
|
}
|
|
|
|
|
norm = scale * sqrt(ssq);
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
ret_val = norm;
|
|
|
|
|
return ret_val;
|
|
|
|
|
|
|
|
|
|
/* End of SNRM2. */
|
|
|
|
|
|
|
|
|
|
} /* snrm2_ */
|
