public static double GradApproximation(List <double> parameters, int index, ConstraintRefBase constraint)
{
var pert = 1e-6;
var temper = parameters[index];
parameters[index] = temper - pert;
var first = constraint.Calc(parameters) * constraint.Calc(parameters);
parameters[index] = temper + pert;
var second = constraint.Calc(parameters) * constraint.Calc(parameters);
parameters[index] = temper;
var grad = .5 * (second - first) / pert;
return(grad);
}
protected void AddRefConstraint(ConstraintRefBase constraint)
{
ConstraintRefList.Add(constraint);
}