Muller's-Method.cpp

/* Muller's Method */
#include <iostream>
#include <iomanip>
#include <math.h>
#define I 2
using namespace std;
float y(float x){
    return cos(x)-x*exp(x);
}
int main(){
    int i,itr,maxitr;
    float x[4],li,di,mu,s,l,aerr;
    cout << "Enter the initial"
    "approximations" << endl;
    for (i = I-2;i<3;i++)
    cin >> x[i];
    cout << "Enter allowed error,"
    "maximum iterations" << endl;
    cin >> aerr >> maxitr;
    cout << fixed;
    for(itr = 1;itr <= maxitr;itr++){
        li = (x[I]-x[I-1])/(x[I-1]-x[I-2]);
        di = (x[I]-x[I-2])/(x[I-1]-x[I-2]);
        mu = y(x[I-2])*li*li
            - y(x[I-1])*di*di
            + y(x[I])*(di+li);
        s = sqrt((mu*mu - 4*y(x[I])*di*li
            *(y(x[I-2])*li-y(x[I-1])
            *di + y(x[I]))));
        if (mu < 0)     l = (2*y(x[I])*di)/(-mu+s);
        else    l = (2*y(x[I])*di)/(-mu-s);
        x[I+1] = x[I]+l*(x[I] - x[I-1]);
        cout << "Iteration no. " << setw(3) << itr
        << "X = " << setw(7) << setprecision(5)
        << x[I+1] << endl;
        if (fabs(x[I+1]-x[I]) < aerr){
        cout << "After" << setw(3) << itr
        << "iterations, the solution is"
        << setw(6) << setprecision(4)
        << x[I+1] << endl;
        return 0;
        }
    for (i=I-2;i<3;i++)
    x[i] = x[i+1];
    }
    cout << "Iterations not sufficient,"
        << "solution does not converge" << endl;
    return 1;
}