Merge pull request #593 from andrewkern/patch_tdist

Fix Student's T kernel formula sign error in tdist()

Author: bhaller

VERSIONS

@@ -26,6 +26,7 @@ development head (in the master branch):
 	add further SIMD optimizations for exp(), log(), log10(), log2() based on the SLEEF framework (https://github.com/shibatch/sleef), thanks to Andy Kern, https://github.com/MesserLab/SLiM/pull/587
 	SIMD optimization for dnorm() using the previous SLEEF work, thanks to Andy Kern, https://github.com/MesserLab/SLiM/pull/588
 	SIMD optimizations for spatial interaction strength calculations, thanks to Andy Kern, https://github.com/MesserLab/SLiM/pull/590
+	fix #593, Student's T distribution had a sign error in tdist(), thanks to Andy Kern, https://github.com/MesserLab/SLiM/issues/591
 
 
 version 5.1 (Eidos version 4.1):

core/spatial_kernel.h

@@ -74,7 +74,7 @@ class SpatialKernel
 	// we don't use the GSL for this, because it does two gamma-function calculations that we don't need (they normalize away)
 	static inline double tdist(double x, double max, double nu, double tau) {
 		double x_over_tau = x / tau;
-		return max / pow(1.0 + x_over_tau * x_over_tau / nu, -(nu + 1.0) / 2.0);
+		return max * pow(1.0 + x_over_tau * x_over_tau / nu, -(nu + 1.0) / 2.0);
 	};
 
 public: