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/* minpack/enorm.f -- translated by f2c (version 20050501).
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
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/*< double precision function enorm(n,x) >*/
doublereal enorm_(integer *n, doublereal *x)
{
/* Initialized data */
static doublereal one = 1.; /* constant */
static doublereal zero = 0.; /* constant */
static doublereal rdwarf = 3.834e-20; /* constant */
static doublereal rgiant = 1.304e19; /* constant */
/* System generated locals */
integer i__1;
doublereal ret_val=0, d__1;
/* Builtin functions */
double sqrt(doublereal);
/* Local variables */
integer i__;
doublereal s1, s2, s3, xabs, x1max, x3max, agiant, floatn;
/*< integer n >*/
/*< double precision x(n) >*/
/* ********** */
/* function enorm */
/* given an n-vector x, this function calculates the */
/* euclidean norm of x. */
/* the euclidean norm is computed by accumulating the sum of */
/* squares in three different sums. the sums of squares for the */
/* small and large components are scaled so that no overflows */
/* occur. non-destructive underflows are permitted. underflows */
/* and overflows do not occur in the computation of the unscaled */
/* sum of squares for the intermediate components. */
/* the definitions of small, intermediate and large components */
/* depend on two constants, rdwarf and rgiant. the main */
/* restrictions on these constants are that rdwarf**2 not */
/* underflow and rgiant**2 not overflow. the constants */
/* given here are suitable for every known computer. */
/* the function statement is */
/* double precision function enorm(n,x) */
/* where */
/* n is a positive integer input variable. */
/* x is an input array of length n. */
/* subprograms called */
/* fortran-supplied ... dabs,dsqrt */
/* argonne national laboratory. minpack project. march 1980. */
/* burton s. garbow, kenneth e. hillstrom, jorge j. more */
/* ********** */
/*< integer i >*/
/*< >*/
/*< data one,zero,rdwarf,rgiant /1.0d0,0.0d0,3.834d-20,1.304d19/ >*/
/* Parameter adjustments */
--x;
/* Function Body */
/*< s1 = zero >*/
s1 = zero;
/*< s2 = zero >*/
s2 = zero;
/*< s3 = zero >*/
s3 = zero;
/*< x1max = zero >*/
x1max = zero;
/*< x3max = zero >*/
x3max = zero;
/*< floatn = n >*/
floatn = (doublereal) (*n);
/*< agiant = rgiant/floatn >*/
agiant = rgiant / floatn;
/*< do 90 i = 1, n >*/
i__1 = *n;
for (i__ = 1; i__ <= i__1; ++i__) {
/*< xabs = dabs(x(i)) >*/
xabs = (d__1 = x[i__], abs(d__1));
/*< if (xabs .gt. rdwarf .and. xabs .lt. agiant) go to 70 >*/
if (xabs > rdwarf && xabs < agiant) {
goto L70;
}
/*< if (xabs .le. rdwarf) go to 30 >*/
if (xabs <= rdwarf) {
goto L30;
}
/* sum for large components. */
/*< if (xabs .le. x1max) go to 10 >*/
if (xabs <= x1max) {
goto L10;
}
/*< s1 = one + s1*(x1max/xabs)**2 >*/
/* Computing 2nd power */
d__1 = x1max / xabs;
s1 = one + s1 * (d__1 * d__1);
/*< x1max = xabs >*/
x1max = xabs;
/*< go to 20 >*/
goto L20;
/*< 10 continue >*/
L10:
/*< s1 = s1 + (xabs/x1max)**2 >*/
/* Computing 2nd power */
d__1 = xabs / x1max;
s1 += d__1 * d__1;
/*< 20 continue >*/
L20:
/*< go to 60 >*/
goto L60;
/*< 30 continue >*/
L30:
/* sum for small components. */
/*< if (xabs .le. x3max) go to 40 >*/
if (xabs <= x3max) {
goto L40;
}
/*< s3 = one + s3*(x3max/xabs)**2 >*/
/* Computing 2nd power */
d__1 = x3max / xabs;
s3 = one + s3 * (d__1 * d__1);
/*< x3max = xabs >*/
x3max = xabs;
/*< go to 50 >*/
goto L50;
/*< 40 continue >*/
L40:
/*< if (xabs .ne. zero) s3 = s3 + (xabs/x3max)**2 >*/
if (xabs != zero) {
/* Computing 2nd power */
d__1 = xabs / x3max;
s3 += d__1 * d__1;
}
/*< 50 continue >*/
L50:
/*< 60 continue >*/
L60:
/*< go to 80 >*/
goto L80;
/*< 70 continue >*/
L70:
/* sum for intermediate components. */
/*< s2 = s2 + xabs**2 >*/
/* Computing 2nd power */
d__1 = xabs;
s2 += d__1 * d__1;
/*< 80 continue >*/
L80:
/*< 90 continue >*/
/* L90: */
;
}
/* calculation of norm. */
/*< if (s1 .eq. zero) go to 100 >*/
if (s1 == zero) {
goto L100;
}
/*< enorm = x1max*dsqrt(s1+(s2/x1max)/x1max) >*/
ret_val = x1max * sqrt(s1 + s2 / x1max / x1max);
/*< go to 130 >*/
goto L130;
/*< 100 continue >*/
L100:
/*< if (s2 .eq. zero) go to 110 >*/
if (s2 == zero) {
goto L110;
}
/*< >*/
if (s2 >= x3max) {
ret_val = sqrt(s2 * (one + x3max / s2 * (x3max * s3)));
}
/*< >*/
if (s2 < x3max) {
ret_val = sqrt(x3max * (s2 / x3max + x3max * s3));
}
/*< go to 120 >*/
goto L120;
/*< 110 continue >*/
L110:
/*< enorm = x3max*dsqrt(s3) >*/
ret_val = x3max * sqrt(s3);
/*< 120 continue >*/
L120:
/*< 130 continue >*/
L130:
/*< return >*/
return ret_val;
/* last card of function enorm. */
/*< end >*/
} /* enorm_ */
#ifdef __cplusplus
}
#endif
|
