84 lines
1.7 KiB
C
84 lines
1.7 KiB
C
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/* -- translated by f2c (version 19940927).
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You must link the resulting object file with the libraries:
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-lf2c -lm (in that order)
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*/
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#include "f2c.h"
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doublereal dnrm2_(integer *n, doublereal *x, integer *incx)
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{
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/* System generated locals */
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integer i__1, i__2;
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doublereal ret_val, d__1;
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/* Builtin functions */
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double sqrt(doublereal);
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/* Local variables */
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static doublereal norm, scale, absxi;
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static integer ix;
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static doublereal ssq;
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/* DNRM2 returns the euclidean norm of a vector via the function
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name, so that
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DNRM2 := sqrt( x'*x )
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-- This version written on 25-October-1982.
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Modified on 14-October-1993 to inline the call to DLASSQ.
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Sven Hammarling, Nag Ltd.
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Parameter adjustments
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Function Body */
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#define X(I) x[(I)-1]
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if (*n < 1 || *incx < 1) {
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norm = 0.;
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} else if (*n == 1) {
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norm = abs(X(1));
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} else {
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scale = 0.;
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ssq = 1.;
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/* The following loop is equivalent to this call to the LAPACK
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auxiliary routine:
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CALL DLASSQ( N, X, INCX, SCALE, SSQ ) */
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i__1 = (*n - 1) * *incx + 1;
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i__2 = *incx;
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for (ix = 1; *incx < 0 ? ix >= (*n-1)**incx+1 : ix <= (*n-1)**incx+1; ix += *incx) {
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if (X(ix) != 0.) {
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absxi = (d__1 = X(ix), abs(d__1));
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if (scale < absxi) {
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/* Computing 2nd power */
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d__1 = scale / absxi;
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ssq = ssq * (d__1 * d__1) + 1.;
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scale = absxi;
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} else {
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/* Computing 2nd power */
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d__1 = absxi / scale;
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ssq += d__1 * d__1;
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}
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}
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/* L10: */
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}
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norm = scale * sqrt(ssq);
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}
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ret_val = norm;
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return ret_val;
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/* End of DNRM2. */
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} /* dnrm2_ */
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