public double Solve(VariableRangeRestriction previousValue, VariableRangeRestriction restriction)
{
double result = _illinois.Solve(previousValue, restriction);
if (double.IsNaN(result)) {
result = _iteration.Solve(previousValue, restriction);
}
return result;
}
public double Solve(VariableRangeRestriction startValue, VariableRangeRestriction restriction)
{
double x0 = startValue.GetSomeValue();
double delta = _delta;
for (int i = 0; ; i++) {
Range[] possibleRanges = Range.CreateClosed(x0 - delta, x0 + delta).Intersect(restriction.PossibleRanges).ToArray();
if (possibleRanges.Length == 0) {
return double.NaN;
}
double x1 = possibleRanges[0].LoApproximateDouble; // TODO: But what if the range is open??
double x2 = possibleRanges[0].HiApproximateDouble;
for (int j = 1; j < possibleRanges.Length && x1 == x2; j++) {
x2 = possibleRanges[j].HiApproximateDouble;
}
double f1 = f(x1);
double f2 = f(x2);
// TODO: What if fL or fH is NaN? Should not happen, because we restrict ourselves to "restriction", but still ...
double k = (f2 - f1) / (x2 - x1);
double d = f2 - k * x2;
x0 = -d / k;
if (!restriction.Contains(x0)) {
// The secant intersects the x-axis in an undefined segment.
// So we have to replace x0 with some valid x; we use the nearest defined x.
double bestReplacement = 1e100;
foreach (var r in restriction.PossibleRanges) {
bestReplacement = BetterReplacement(bestReplacement, x0, r.LoApproximateDouble);
bestReplacement = BetterReplacement(bestReplacement, x0, r.HiApproximateDouble);
}
x0 = bestReplacement;
}
double f0 = f(x0);
// TODO: Again, f0 could be NaN? Should not happen, because we restrict ourselves to "restriction", but still ...
delta /= 2.0;
if (x1.Near(x2) && f0.Near(0)) {
return (x1 + x2) / 2;
}
if ((1e6 * f0).Near(0)) {
return (x1 + x2) / 2;
}
if (double.IsNaN(f0) || i > 100) {
return double.NaN;
}
}
}
public double Solve(VariableRangeRestriction previousValue, VariableRangeRestriction restriction)
{
foreach (var range in restriction.PossibleRanges) {
double x1 = range.LoApproximateDouble;
double x2 = range.HiApproximateDouble;
var f1 = f(x1);
var f2 = f(x2);
if (f1 * f2 <= 0) {
double result = Illinois(x1, x2, f1, f2);
if (!double.IsNaN(result)) {
return result;
}
}
}
return double.NaN;
}
