real_2d_array x=[[1,0],[2,0],[3,0]];
real_1d_array y=[0,2.01,4];
real_1d_array c=[1,1,0];
real_1d_array cu=[1e8,1e8,0];
real_1d_array cd=[-1e8,1e8,0];

double epsf = 0;
double epsx = 1e-10;
ae_int_t maxits = 0;
ae_int_t info;
lsfitstate state;
lsfitreport rep;
double diffstep = 1e-7;
int differentturns=0;

lsfitcreatef(x, y, c, diffstep, state);
lsfitsetcond(state, epsf, epsx, maxits);
lsfitsetbc(state, cd, cu);
alglib::lsfitfit(state, function_cx_1_func);
lsfitresults(state, info, c, rep);

    void function_cx_1_func(const real_1d_array &c, const real_1d_array &x, double &func, void *ptr)
{
   func = c[0]*pow(x[0]+c[1],2)/pow(1+c[2]*x[1],2);
}