51 lines
1.3 KiB
C
51 lines
1.3 KiB
C
#include "nrutil.h"
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#include "muller.h"
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#include <math.h>
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float rtmuller(float (*func)(float), float x1, float x2, float xacc) {
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int j;
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float fh, fl, fm, fnew, s, xl, r, x3, x0, x_prev, x_curr, x_next;
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float d0, d1, d2, a, b, c;
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x0 = x1;
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x_prev = x2;
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x_curr = (x0 + x_prev) / 2.0;
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if (x_prev == x_curr) x_curr += xacc;
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if (x0 == x_curr) x0 -= xacc;
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for (j = 1; j <= 200; j++) {
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d0 = func(x0);
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d1 = func(x_prev);
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d2 = func(x_curr);
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float h1 = x_prev - x0;
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float h2 = x_curr - x_prev;
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float delta1 = (d1 - d0) / h1;
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float delta2 = (d2 - d1) / h2;
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a = (delta2 - delta1) / (h2 + h1);
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b = a * h2 + delta2;
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c = d2;
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float disc = b * b - 4 * a * c;
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if (disc < 0) nrerror("Muller's method: complex roots encountered");
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float denom1 = b + sqrt(disc);
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float denom2 = b - sqrt(disc);
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if (fabs(denom1) < fabs(denom2)) {
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x_next = x_curr - (2 * c) / denom2;
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} else {
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x_next = x_curr - (2 * c) / denom1;
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}
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if (fabs(x_next - x_curr) < xacc) return x_next;
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x0 = x_prev;
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x_prev = x_curr;
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x_curr = x_next;
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}
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nrerror("Too many iterations in rtmuller");
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return 0.0;
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} |