Example #1
0
        public double FindRoot(Func <double, double> function, Func <double, double> derivative, double a, double b, double eps1, double eps2, ref int numOfIterations)
        {
            var bisectA         = a;
            var bisectB         = b;
            var bisectionresult = new Bisection().FindRoot(ref bisectA, ref bisectB, eps1, function, ref numOfIterations);

            Console.WriteLine("Interval after bisection: [{0};{1}]", bisectA, bisectB);
            double xPrev = (bisectA + bisectB) / 2;

            Console.Write("{0} ", xPrev);
            double x = 0;
            int    i;

            for (i = 0; i < 100; i++) //prevent infinite loop
            {
                x = xPrev - function(xPrev) / derivative(xPrev);
                Console.Write("{0} ", x);
                if (Math.Abs(x - xPrev) < eps2)
                {
                    break;
                }
                xPrev = x;
            }
            numOfIterations += i + 1;
            Console.WriteLine("Finished in {0} iterations", i + 1);
            return(x);
        }
Example #2
0
        static void Main(string[] args)
        {
            Func <double, double> fn1 = x => (x * Math.Pow(Math.E, 0.8 * x)) - 12;                   //Andris x*e^(0.8*x) - 12
            Func <double, double> fn2 = x => (x * x * Math.Sin(x)) - 0.12;                           //Alina (x^2)*sinx - 0.12
            Func <double, double> fn3 = x => (Math.Pow(Math.Log(x), 2) / x) - 12;                    //Moritz ((lnx)^2)/x - 12

            Func <double, double> fn1d = x => 0.8 * Math.Pow(Math.E, (0.8 * x)) * (x + 1.25);        //Andris
            Func <double, double> fn2d = x => x * (x * Math.Cos(x) + 2 * Math.Sin(x));               //Alina
            Func <double, double> fn3d = x => - ((-2 + Math.Log(x)) * Math.Log(x)) / Math.Pow(x, 2); //Moritz

            var bisection = new Algorithms.Bisection();

            Console.WriteLine("Bisection");
            double a = 2;
            double b = 3;
            int    numOfIterations = 0;

            Console.WriteLine(bisection.FindRoot(ref a, ref b, 0.0001, fn1, ref numOfIterations));
            Console.WriteLine(numOfIterations);
            a = 3; b = 4;
            numOfIterations = 0;
            Console.WriteLine(bisection.FindRoot(ref a, ref b, 0.0001, fn2, ref numOfIterations));
            Console.WriteLine(numOfIterations);
            a = 0; b = 1;
            numOfIterations = 0;
            Console.WriteLine(bisection.FindRoot(ref a, ref b, 0.0001, fn3, ref numOfIterations));
            Console.WriteLine(numOfIterations);
            numOfIterations = 0;
            Console.WriteLine();
            var newtons = new Algorithms.NewtonsCombined();

            Console.WriteLine("Andris x*e^(0.8*x) - 12 - Newtons Method - eps = 0.01, eps for bisection = 0.1");
            newtons.FindRoot(fn1, fn1d, 2, 3, 0.1, 0.0001, ref numOfIterations);
            Console.WriteLine(numOfIterations);
            numOfIterations = 0;
            Console.WriteLine("Alina (x^2)*sinx - 0.12 - Newtons Method - eps = 0.01, eps for bisection = 0.1");
            newtons.FindRoot(fn2, fn2d, 3, 4, 0.1, 0.0001, ref numOfIterations);
            Console.WriteLine(numOfIterations);
            numOfIterations = 0;
            Console.WriteLine("Moritz ((lnx)^2)/x - 12 - Newtons Method - eps = 0.01, eps for bisection = 0.1");
            newtons.FindRoot(fn3, fn3d, 0, 1, 0.1, 0.0001, ref numOfIterations);
            Console.WriteLine(numOfIterations);
            Console.Read();
        }