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/* blas/dnrm2.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 DNRM2 ( N, X, INCX ) >*/
doublereal dnrm2_(integer *n, doublereal *x, integer *incx)
{
/* System generated locals */
integer i__1, i__2;
doublereal ret_val, d__1;
/* Builtin functions */
double sqrt(doublereal);
/* Local variables */
integer ix;
doublereal ssq, norm, scale, absxi;
/* .. Scalar Arguments .. */
/*< INTEGER INCX, N >*/
/* .. Array Arguments .. */
/*< DOUBLE PRECISION X( * ) >*/
/* .. */
/* DNRM2 returns the euclidean norm of a vector via the function */
/* name, so that */
/* DNRM2 := sqrt( x'*x ) */
/* -- This version written on 25-October-1982. */
/* Modified on 14-October-1993 to inline the call to DLASSQ. */
/* Sven Hammarling, Nag Ltd. */
/* .. Parameters .. */
/*< DOUBLE PRECISION ONE , ZERO >*/
/*< PARAMETER ( ONE = 1.0D+0, ZERO = 0.0D+0 ) >*/
/* .. Local Scalars .. */
/*< INTEGER IX >*/
/*< DOUBLE PRECISION ABSXI, NORM, SCALE, SSQ >*/
/* .. Intrinsic Functions .. */
/*< INTRINSIC ABS, SQRT >*/
/* .. */
/* .. Executable Statements .. */
/*< IF( N.LT.1 .OR. INCX.LT.1 )THEN >*/
/* Parameter adjustments */
--x;
/* Function Body */
if (*n < 1 || *incx < 1) {
/*< NORM = ZERO >*/
norm = 0.;
/*< ELSE IF( N.EQ.1 )THEN >*/
} else if (*n == 1) {
/*< NORM = ABS( X( 1 ) ) >*/
norm = abs(x[1]);
/*< ELSE >*/
} else {
/*< SCALE = ZERO >*/
scale = 0.;
/*< SSQ = ONE >*/
ssq = 1.;
/* The following loop is equivalent to this call to the LAPACK */
/* auxiliary routine: */
/* CALL DLASSQ( N, X, INCX, SCALE, SSQ ) */
/*< DO 10, IX = 1, 1 + ( N - 1 )*INCX, INCX >*/
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 ).NE.ZERO )THEN >*/
if (x[ix] != 0.) {
/*< ABSXI = ABS( X( IX ) ) >*/
absxi = (d__1 = x[ix], abs(d__1));
/*< IF( SCALE.LT.ABSXI )THEN >*/
if (scale < absxi) {
/*< SSQ = ONE + SSQ*( SCALE/ABSXI )**2 >*/
/* Computing 2nd power */
d__1 = scale / absxi;
ssq = ssq * (d__1 * d__1) + 1.;
/*< SCALE = ABSXI >*/
scale = absxi;
/*< ELSE >*/
} else {
/*< SSQ = SSQ + ( ABSXI/SCALE )**2 >*/
/* Computing 2nd power */
d__1 = absxi / scale;
ssq += d__1 * d__1;
/*< END IF >*/
}
/*< END IF >*/
}
/*< 10 CONTINUE >*/
/* L10: */
}
/*< NORM = SCALE * SQRT( SSQ ) >*/
norm = scale * sqrt(ssq);
/*< END IF >*/
}
/*< DNRM2 = NORM >*/
ret_val = norm;
/*< RETURN >*/
return ret_val;
/* End of DNRM2. */
/*< END >*/
} /* dnrm2_ */
#ifdef __cplusplus
}
#endif
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