/// <summary>
/// Finds minimum of given function using the Gradient Descent algorithm.
/// </summary>
/// <param name="function">Function used in algorithm.</param>
/// <param name="e">Precision.</param>
/// <param name="startingPoint">Starting point of algorithm.</param>
/// <param name="usingGoldenSection">Flag used for tracking whether user wants to use Golden Section algorithm or not.</param>
/// <returns>Minimum of function.</returns>
public static Matrica FindMinimum(Function function, double e, Matrica startingPoint, bool usingGoldenSection)
{
Matrica x = new Matrica();
x.Equals(startingPoint);
function.SetParametersSize(x.NoOfRows);
Matrica v = new Matrica();
int brojac = 0;
Matrica xs = new Matrica();
if (usingGoldenSection == false)
{
do
{
xs.Equals(x);
v = function.CalculateGradientValue(x.VectorToArray());
function.IncreaseCounterGradientValue(algorithmName);
v.MultiplyByScalar(-1);
x.AddValue(v);
brojac++;
function.IncreaseCounterValue(algorithmName);
function.IncreaseCounterValue(algorithmName);
} while (brojac < 10000);
}
else
{
do
{
xs.Equals(x);
v = function.CalculateGradientValue(x.VectorToArray());
function.IncreaseCounterGradientValue(algorithmName);
v.MultiplyByScalar(-1);
v.MultiplyByScalar(1.0 / function.GetGradientNorm());
for (int i = 0; i < x.NoOfRows; i++)
{
double value = x.LoadedMatrix[i][0];
double vectorValue = v.LoadedMatrix[i][0];
Expression expression = lambda => value + lambda * vectorValue;
function.SetParameters(i, expression);
}
UnimodalInterval interval = UnimodalInterval.FindUnimodalInterval(function, 0, 1, algorithmName);
UnimodalInterval lambdaInterval = GoldenSection.FindMinimum(function, interval.Minimum, interval.Maximum, e, algorithmName);
double lambdaMin = (lambdaInterval.Minimum + lambdaInterval.Maximum) / 2;
v.MultiplyByScalar(lambdaMin);
x.AddValue(v);
function.IncreaseCounterValue(algorithmName);
function.IncreaseCounterValue(algorithmName);
} while (function.GetGradientNorm() >= e);
}
function.DeleteParameters();
return(x);
}
/// <summary>
/// Finds minimum of function using Box optimization method.
/// </summary>
/// <param name="function">Function used to optimize.</param>
/// <param name="implicitRestrictions">List of implicit restrictions used in Box method.</param>
/// <param name="explicitRestriction">List of explicit restrictions used in Box method.</param>
/// <param name="startingPoint">Starting point of algorithm.</param>
/// <param name="alfa">Constant alpha used in algorithm.</param>
/// <param name="iterations">Number of iterations of algorithm.</param>
/// <returns></returns>
public static Matrica FindMinimum(Function function, List <RestrictionExpression> implicitRestrictions, ExplicitRestriction explicitRestriction, Matrica startingPoint, double alfa, int iterations)
{
if (OptimizationUtils.CheckIfExplicitConstraintsAreMet(explicitRestriction, startingPoint) == false ||
OptimizationUtils.CheckIfImplicitConstraintsAreMet(implicitRestrictions, startingPoint) == false)
{
throw new ArgumentException("Starting point does not meet explicit and/or implicit conditions!");
}
int iter = 0;
function.SetParametersSize(startingPoint.NoOfRows);
Matrica centroid = new Matrica();
centroid.Equals(startingPoint);
int n = startingPoint.NoOfRows;
Random random = new Random();
double R;
List <Matrica> simplex = new List <Matrica>();
UnimodalInterval interval = explicitRestriction.GetInterval();
for (int t = 0; t < 2 * n; t++)
{
double[] point = new double[n];
for (int i = 0; i < n; i++)
{
R = random.NextDouble() * (maximumForRandom - minimumForRandom) + minimumForRandom;
point[i] = interval.Minimum + R * (interval.Maximum - interval.Minimum);
}
simplex.Insert(t, Matrica.ArrayToVector(point));
bool[] simplexPointMeetsImplicitRestrictions = new bool[implicitRestrictions.Count];
for (int i = 0; i < implicitRestrictions.Count; i++)
{
simplexPointMeetsImplicitRestrictions[i] = false;
}
while (true)
{
for (int i = 0; i < implicitRestrictions.Count; i++)
{
simplexPointMeetsImplicitRestrictions[i] = implicitRestrictions[i].CheckIfMet(simplex[t].VectorToArray());
if (simplexPointMeetsImplicitRestrictions[i] == false)
{
simplex[t].AddValue(centroid);
simplex[t].MultiplyByScalar(1.0 / 2);
break;
}
}
if (!simplexPointMeetsImplicitRestrictions.Contains(false))
{
break;
}
}
centroid = GetCentroidPoint(simplex);
}
List <double> functionValues = GetSimplexPointsFunctionValues(simplex, function);
Matrica xr = new Matrica();
do
{
int h = GetIndexOfWorstPoint(functionValues);
int h2 = GetIndexOfSecondWorstPoint(functionValues, h);
centroid = GetCentroidPoint(simplex, h);
xr = Reflection(centroid, simplex[h], alfa);
for (int i = 0; i < xr.NoOfRows; i++)
{
if (xr.LoadedMatrix[i][0] < interval.Minimum)
{
xr.LoadedMatrix[i][0] = interval.Minimum;
}
else if (xr.LoadedMatrix[i][0] > interval.Maximum)
{
xr.LoadedMatrix[i][0] = interval.Maximum;
}
}
bool[] reflectionMeetsImplicitRestrictions = new bool[implicitRestrictions.Count];
for (int i = 0; i < implicitRestrictions.Count; i++)
{
reflectionMeetsImplicitRestrictions[i] = false;
}
while (true)
{
for (int i = 0; i < implicitRestrictions.Count; i++)
{
reflectionMeetsImplicitRestrictions[i] = implicitRestrictions[i].CheckIfMet(xr.VectorToArray());
if (reflectionMeetsImplicitRestrictions[i] == false)
{
xr.AddValue(centroid);
xr.MultiplyByScalar(1.0 / 2);
break;
}
}
if (!reflectionMeetsImplicitRestrictions.Contains(false))
{
break;
}
}
double xrFunctionValue = function.CalculateValue(xr.VectorToArray());
function.IncreaseCounterValue(algorithmName);
if (xrFunctionValue > functionValues[h2])
{
xr.AddValue(centroid);
xr.MultiplyByScalar(1.0 / 2);
}
simplex[h] = xr;
functionValues[h] = xrFunctionValue;
iter++;
} while (iter < iterations);
function.DeleteParameters();
return(simplex.ElementAt(functionValues.IndexOf(functionValues.Min())));
}
/// <summary>
/// Finds minimum of function using Newton-Raphson algorithm.
/// </summary>
/// <param name="function">Function used in algorithm.</param>
/// <param name="e">Precision</param>
/// <param name="startingPoint">Starting point of algorithm.</param>
/// <param name="usingGoldenSection">Flag used for tracking whether user wants to use Golden Section algorithm or not.</param>
/// <returns>Minimum of function.</returns>
public static Matrica FindMinimum(Function function, double e, Matrica startingPoint, bool usingGoldenSection)
{
Matrica x = new Matrica();
x.Equals(startingPoint);
function.SetParametersSize(x.NoOfRows);
Matrica gradient = new Matrica();
Matrica hessianMatrix = new Matrica();
int brojac = 0;
Matrica xs = new Matrica();
if (usingGoldenSection == false)
{
do
{
xs.Equals(x);
gradient = function.CalculateGradientValue(x.VectorToArray());
function.IncreaseCounterGradientValue(algorithmName);
hessianMatrix = function.CalculateHessianMatrix(x.VectorToArray());
function.IncreaseCounterHessian(algorithmName);
Matrica LU = hessianMatrix.LUPDecomposition(e, gradient);
Matrica y = Matrica.ForwardSubstitution(LU, gradient);
Matrica deltaX = Matrica.BackwardSubstitution(LU, gradient, e);
x.AddValue(deltaX);
brojac++;
function.IncreaseCounterValue(algorithmName);
function.IncreaseCounterValue(algorithmName);
} while (brojac < 100);
}
else
{
do
{
xs.Equals(x);
gradient = function.CalculateGradientValue(x.VectorToArray());
function.IncreaseCounterGradientValue(algorithmName);
hessianMatrix = function.CalculateHessianMatrix(x.VectorToArray());
function.IncreaseCounterHessian(algorithmName);
Matrica LU = hessianMatrix.LUPDecomposition(e, gradient);
Matrica y = Matrica.ForwardSubstitution(LU, gradient);
Matrica deltaX = Matrica.BackwardSubstitution(LU, gradient, e);
x.AddValue(deltaX);
for (int i = 0; i < x.NoOfRows; i++)
{
double value = x.LoadedMatrix[i][0];
double vectorValue = deltaX.LoadedMatrix[i][0];
Expression expression = lambda => value + lambda * vectorValue;
function.SetParameters(i, expression);
}
UnimodalInterval interval = UnimodalInterval.FindUnimodalInterval(function, 0, 1, algorithmName);
UnimodalInterval lambdaInterval = GoldenSection.FindMinimum(function, interval.Minimum, interval.Maximum, e, algorithmName);
double lambdaMin = (lambdaInterval.Minimum + lambdaInterval.Maximum) / 2;
deltaX.MultiplyByScalar(lambdaMin);
x.AddValue(deltaX);
function.IncreaseCounterValue(algorithmName);
function.IncreaseCounterValue(algorithmName);
} while (function.GetGradientNorm() >= e);
}
function.DeleteParameters();
return(x);
}
