实现这个简单的寻根算法。 http://en.wikipedia.org/wiki/Durand%E2%80%93Kerner_method 我一生都无法弄清楚我的实现有什么问题。根不断膨胀,没有收敛的迹象。有什么建议么?
谢谢。
#include <iostream>
#include <complex>
using namespace std;
typedef complex<double> dcmplx;
dcmplx f(dcmplx x)
{
// the function we are interested in
double a4 = 3;
double a3 = -3;
double a2 = 1;
double a1 = 0;
double a0 = 100;
return a4 * pow(x,4) + a3 * pow(x,3) + a2 * pow(x,2) + a1 * x + a0;
}
int main()
{
dcmplx p(.9,2);
dcmplx q(.1, .5);
dcmplx r(.7,1);
dcmplx s(.3, .5);
dcmplx p0, q0, r0, s0;
int max_iterations = 20;
bool done = false;
int i=0;
while (i<max_iterations && done == false)
{
p0 = p;
q0 = q;
r0 = r;
s0 = s;
p = p0 - f(p0)/((p0-q0)*(p0-r0)*(p0-s0));
q = q0 - f(q0)/((q0-p)*(q0-r0)*(q0-s0));
r = r0 - f(r0)/((r0-p)*(r0-q)*(r0-s0));
s = s0 - f(s0)/((s0-p)*(s0-q)*(s0-r));
// if convergence within small epsilon, declare done
if (abs(p-p0)<1e-5 && abs(q-q0)<1e-5 && abs(r-r0)<1e-5 && abs(s-s0)<1e-5)
done = true;
i++;
}
cout<<"roots are :\n";
cout << p << "\n";
cout << q << "\n";
cout << r << "\n";
cout << s << "\n";
cout << "number steps taken: "<< i << endl;
return 0;
}