X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=foosrank.cpp;h=b4f12dc927f2371e03769e2d279eb9fd0505c14c;hb=6d454fc54830023ce429861a14ef494aa2872445;hp=802464d6e4d81cd8eee49d7ee6c12ddb39bb78c1;hpb=8e3849860e66edb4742b3525e1d0fa436cc188b9;p=foosball

diff --git a/foosrank.cpp b/foosrank.cpp
index 802464d..b4f12dc 100644
--- a/foosrank.cpp
+++ b/foosrank.cpp
@@ -400,13 +400,16 @@ static void compute_new_rating(double mu1, double sigma1, double mu2, double sig
 	// Compute the overall probability of the given result, by integrating
 	// the entire resulting pdf. Note that since we're actually evaluating
 	// a double integral, we'll need to multiply by h² instead of h.
-	// (TODO: Use Simpson's rule here.)
+	// (For some reason, Simpson's rule gives markedly worse accuracy here.
+	// Probably related to h² somehow?)
 	{
 		double h = (curve.back().first - curve.front().first) / (curve.size() - 1);
 		double sum = 0.0;
 		for (unsigned i = 0; i < curve.size(); ++i) {
-			sum += h * h * curve[i].second;
+			sum += curve[i].second;
 		}
+
+		sum *= h * h;
 	
 		// FFT convolution multiplication factor (FFTW computes unnormalized
 		// transforms)
@@ -487,13 +490,17 @@ static void compute_new_double_rating(double mu1, double sigma1, double mu2, dou
 	// the entire resulting pdf. Note that since we're actually evaluating
 	// a triple integral, we'll need to multiply by 4h³ (no idea where the
 	// 4 factor comes from, probably from the 0..6000 range somehow) instead
-	// of h. (TODO: Use Simpson's rule here.)
+	// of h.
+	// (TODO: Evaluate Simpson's rule here, although it's probably even worse
+	// than for the single case.)
 	{
 		double h = (newcurve.back().first - newcurve.front().first) / (newcurve.size() - 1);
 		double sum = 0.0;
 		for (unsigned i = 0; i < newcurve.size(); ++i) {
-			sum += 4.0 * h * h * h * newcurve[i].second;
+			sum += newcurve[i].second;
 		}
+
+		sum *= 4.0 * h * h * h;
 	
 		// FFT convolution multiplication factor (FFTW computes unnormalized
 		// transforms)