public double Integrate(BoundaryElement <T> elem, T eta, Func <T, T, double> f, bool etaOnElement = false)
{
if (etaOnElement && eta is Point2D)
{
// TODO : works properly only for f == Ln(|x-y|). Improve for derivates also.
// TODO : this is harcode. It uses fact that eta = element.Center, and hence eta=(fi1(0), fi2(0)), where fi1, fi2 - interpolation functions.
var t = 0;
var etaY = elem.Yakobian(new Point1D(t));
var exactIntegralPart = GetExactPart(t);
return(elem.GetIntegrationPoints(n).Sum(p => f(eta, p.Point) * (p.Jacobian - etaY))
- etaY * exactIntegralPart);
}
return(elem.GetIntegrationPoints(n).Sum(p => p.Weight * p.Jacobian * f(eta, p.Point)));
}
public double Integrate(BoundaryElement <T> elem1, BoundaryElement <T> elem2, Func <T, T, double> f)
{
return
(elem1.GetIntegrationPoints(n).Sum(
p1 =>
elem2.GetIntegrationPoints(n + 2).Sum(
p2 => p1.Weight * p2.Weight * p1.Jacobian * p2.Jacobian * f(p1.Point, p2.Point))));
}
public double Integrate(BoundaryElement <T> elem, T eta, Func <T, double> f, Func <T, T, double> fundamental)
{
return(elem.GetIntegrationPoints(n).Sum(p => p.Weight * p.Jacobian * f(p.Point) * fundamental(eta, p.Point)));
}