Optimize the sech²(x) function a bit.

[foosball] / foosrank.cpp

diff --git a/foosrank.cpp b/foosrank.cpp
index 99f88b0d5909699630d382785bb59385f5757371..d295c212ed04187a5ba42995a2d2a5852bf65150 100644 (file)
--- a/foosrank.cpp
+++ b/foosrank.cpp
@@ -32,8 +32,8 @@ static double fac(int x);
 // sech²(x)
 static double sech2(double x)
 {
-       double c = cosh(x);
-       return 1.0 / (c*c);
+       double e = exp(2.0 * x);
+       return 4.0 * e / ((e+1.0) * (e+1.0));
 }
 #endif
 
@@ -484,7 +484,11 @@ int main(int argc, char **argv)
                int score2 = atoi(argv[10]);
                double mu, sigma;
                compute_new_double_rating(mu1, sigma1, mu2, sigma2, mu3, sigma3, mu4, sigma4, score1, score2, mu, sigma);
-               printf("%f %f\n", mu, sigma);
+               if (score1 > score2) {
+                       printf("%f %f %f\n", mu, sigma, prob_score(score1, score2, mu3+mu4-(mu1+mu2)));
+               } else {
+                       printf("%f %f %f\n", mu, sigma, prob_score(score2, score1, mu1+mu2-(mu3+mu4)));
+               }
        } else if (argc > 8) {
                double mu3 = atof(argv[5]);
                double sigma3 = atof(argv[6]);
@@ -520,7 +524,12 @@ int main(int argc, char **argv)
                int score2 = atoi(argv[6]);
                double mu, sigma;
                compute_new_rating(mu1, sigma1, mu2, sigma2, score1, score2, mu, sigma);
-               printf("%f %f\n", mu, sigma);
+
+               if (score1 > score2) {
+                       printf("%f %f %f\n", mu, sigma, prob_score(score1, score2, mu2-mu1));
+               } else {
+                       printf("%f %f %f\n", mu, sigma, prob_score(score2, score1, mu1-mu2));
+               }
        } else {
                int k = atoi(argv[5]);