43 lines
1.0 KiB
C++
43 lines
1.0 KiB
C++
#ifdef __cplusplus
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extern "C" {
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#endif
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#include "lmp_f2c.h"
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doublereal dnrm2_(integer *n, doublereal *x, integer *incx)
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{
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integer i__1, i__2;
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doublereal ret_val, d__1;
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double sqrt(doublereal);
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integer ix;
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doublereal ssq, norm, scale, absxi;
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--x;
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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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i__1 = (*n - 1) * *incx + 1;
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i__2 = *incx;
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for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
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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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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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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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}
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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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}
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#ifdef __cplusplus
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}
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#endif
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