Wolfe_unknown_quality

double QNM::Wulf(vect xk, vect dk)
{
    double eps1 = 1E-4, eps2 = 5E-1, alpha = 1, a_bot = 0, a_top = 0;
    double thet1 = 1.1, thet2 = 0.5, scal = d_f(xk, dim).scal_mul(dk);
    vect xk_adk(dim);

    int stop_index = 0;
    while (stop_index < 1E3)//1E4
    {
        stop_index++;
        xk_adk = (dk*alpha) + xk;
        /*
        cout << xk[0]<<" " << xk[1] <<"||" << xk_adk[0] << " " << xk_adk[1]
        <<"|(1)|" << f_x(xk_adk) - f_x(xk) - eps1 * alpha * scal
        <<"|(2)|" << d_f(xk_adk, dim).scal_mul(dk) - eps2 * scal <<"\n";
        */
        if (f_x(xk_adk) - f_x(xk) - eps1 * alpha * scal < 0) // с вешественным нулем все только хуже.
        {
            double check1 = d_f(xk_adk, dim).scal_mul(dk) - eps2 * scal;
            if (d_f(xk_adk, dim).scal_mul(dk) - eps2 * scal > 0)
            {
                break;
            }
            else
            {
                a_bot = alpha;
                if (abs(a_top) < 0)
                {
                    alpha *= thet1;
                }
            }
        }
        else
        {
            a_top = alpha;
            alpha = (1 - thet2)*a_bot + thet2*a_top;

        }
    }
    cout<<"Wulf_iterations = " << stop_index << "\n";
    return alpha;
}