Esempio n. 1
0
        public static Vector2 FindMin(Vector2 x0, double eps)
        {
            double  alpha;
            double  f;
            Vector2 grad;
            int     i = 0;
            Vector2 x;

            do
            {
                //Устанавливаем максимальное значение alpha
                alpha = alphaMax;
                //Вычисляем градиент в x_k
                grad = Rosenbrock.Gradient(x0);
                //Проверяем условие Армихо
                do
                {
                    i++;
                    alpha *= 0.75;
                    x      = x0 - alpha * grad;
                    f      = -(Rosenbrock.F(x) - Rosenbrock.F(x0)) / (alpha * grad.Norm * grad.Norm);
                } while (!((delta1 <= f) && (f <= delta2)));

                x   = x0.Copy();
                x0 -= alpha * Rosenbrock.Gradient(x0);
            }while(grad.Norm > eps);
            Console.WriteLine("Iterations:\t{0}", i);
            return(x);
        }
Esempio n. 2
0
        public static Vector2 FindMin(Vector2 x, double EPS)
        {
            int     i = 0;
            double  alpha;
            Vector2 grad = Rosenbrock.Gradient(x);
            Vector2 d    = -1 * Rosenbrock.Gradient(x);
            double  prevGradSquare;

            do
            {
                i++;
                prevGradSquare = grad.Norm * grad.Norm;

                alpha = Rosenbrock.GoldenSearch(x, d);
                x    += alpha * d;
                grad  = Rosenbrock.Gradient(x);

                if (i % 2 == 0)
                {
                    d = -1 * grad;
                }
                else
                {
                    double beta = grad.Norm * grad.Norm / prevGradSquare;
                    d = beta * d - grad;
                }
            } while(d.Norm > EPS);
            Console.WriteLine("Iterations:\t{0}", i);
            return(x);
        }
Esempio n. 3
0
        public static Vector2 FindMin(Vector2 p, double eps)
        {
            Vector2 p0;

            double[,] H;

            Vector2 grad;

            do
            {
                p0   = p.Copy();
                H    = Newton.InverseHessian(p0);
                grad = Rosenbrock.Gradient(p0);

                p -= (H * grad);
            } while ((p - p0).Norm > eps);

            return(p);
        }
Esempio n. 4
0
        public static Vector2 FindMin(Vector2 point, double EPS)
        {
            Vector2 delta = new Vector2(0.1, 0.1);
            Vector2 df;
            Vector2 dfPrev = new Vector2(0, 0);

            int k = 0;

            do
            {
                k++;
                df = Rosenbrock.Gradient(point);
                for (int i = 0; i < 2; i++)
                {
                    double product = df[i] * dfPrev[i];
                    if (product > 0)
                    {
                        delta[i]  = Math.Min(delta[i] * etaPlus_, deltaMax_);
                        point[i] -= Math.Sign(df[i]) * delta[i];
                        dfPrev[i] = df[i];
                    }
                    else if (product < 0)
                    {
                        delta[i]  = Math.Max(delta[i] * etaMinus_, deltaMin_);
                        dfPrev[i] = 0;
                    }
                    else
                    {
                        point[i] -= Math.Sign(df[i]) * delta[i];
                        dfPrev[i] = df[i];
                    }
                }
            } while (df.Norm > 1e-7);

            Console.WriteLine("Iterations:\t{0}", k);

            return(point);
        }