public double[] Solve(
Func <double[], double> f,
Func <double[], double>[] df,
double[] startValue,
int nIter)
{
OptVector xOld = new OptVector(startValue);
OptVector xNew = new OptVector();
OptVector derivativeOld = OptimizationHelper.Derivative(df, xOld);
OptVector direction = -1.0 * derivativeOld;
OptVector derivativeNew = new OptVector();
for (int i = 0; i < nIter; i++)
{
StepSize = strongWolfeLineSearch.GetStepLength(f, df, direction, xOld, 20);
xNew = xOld + StepSize * direction;
if (CheckEarlyExit(xNew, xOld))
{
break;
}
derivativeNew = OptimizationHelper.Derivative(df, xNew);
double beta = PolakRibiere(derivativeNew, derivativeOld);
direction = beta * direction - derivativeNew;
xOld = xNew;
derivativeOld = derivativeNew;
}
return(xNew.MinArray);
}
public double GetStepLength(
Func <double[], double> f,
Func <double[], double>[] df,
OptVector d,
OptVector x0,
double alpham)
{
int maxIter = 15;
double alphap = 0;
double c1 = 1E-4;
double c2 = 0.5;
Random rnd = new Random();
double alphax = 1;
double fx0 = f(x0.MinArray);
double gx0 = OptimizationHelper.Derivative(df, x0) * d;
double fxp = fx0;
double gxp = gx0;
for (int i = 1; i < maxIter; i++)
{
OptVector xx = x0 + alphax * d;
double fxx = f(xx.MinArray);
double gxx = OptimizationHelper.Derivative(df, xx) * d;
if (fxx > fx0 + c1 * alphax * gx0 ||
(i > 1 && fxx >= fxp))
{
return(Zoom(f, df, x0, d, alphap, alphax));
}
if (Math.Abs(gxx) <= -c2 * gx0)
{
return(alphax);
}
if (gxx >= 0)
{
return(Zoom(f, df, x0, d, alphax, alphap));
}
alphap = alphax;
fxp = fxx;
gxp = gxx;
alphax = alphax + (alpham - alphax) * 0.3;
}
return(alphax);
}
public IEnumerable <Tuple <Expert, double> > GetOptimalWeights()
{
var wdm = new Func <double, double> (alpha => {
const int cdm = 1; // manager.GetDMCalibrationScore ();
var idm = GetDMInformationScore(alpha);
var sum = GetWeights(alpha).Sum(x => x.Item2);
return(sum > 0 ? ((cdm * idm) / sum) : (cdm * idm));
});
var upperbound = GetWeights().Max(x => x.Item2);
var optimalAlpha = OptimizationHelper.LocalMin(0, upperbound, x => - wdm(x), 1.2e-16, Math.Sqrt(Double.Epsilon));
Console.WriteLine(optimalAlpha);
return(GetWeights(optimalAlpha));
}
private static double Zoom(
Func <double[], double> f,
Func <double[], double>[] df,
OptVector x0,
OptVector d,
double alphal,
double alphah)
{
int maxIter = 10;
double c1 = 1E-4;
double c2 = 0.5;
double fx0 = f(x0.MinArray);
double gx0 = OptimizationHelper.Derivative(df, x0) * d;
double alphax = 0.0;
for (int i = 0; i < maxIter; i++)
{
alphax = 0.5 * (alphal + alphah);
OptVector xx = x0 + alphax * d;
double fxx = f(xx.MinArray);
double gxx = OptimizationHelper.Derivative(df, xx) * d;
OptVector xl = x0 + alphal * d;
double fxl = f(xl.MinArray);
if (fxx > fx0 + c1 * alphax * gx0 ||
fxx >= fxl)
{
alphah = alphax;
}
else
{
if (Math.Abs(gxx) <= -c2 * gx0)
{
return(alphax);
}
if (gxx * (alphah - alphal) >= 0.0)
{
alphah = alphal;
}
alphal = alphax;
}
}
return(alphax);
}
