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