Author: celestin
Date: Wed Aug 29 04:28:47 2012
New Revision: 1378440
URL: http://svn.apache.org/viewvc?rev=1378440&view=rev
Log:
In GammaDistributionTest, inlined previous implementation of
double Gamma.logGamma(doubl)) in order to allow for comparison with new
implementation.
This is in preparation of MATH-849.
Modified:
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/distribution/GammaDistributionTest.java
Modified:
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/distribution/GammaDistributionTest.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math3/distribution/GammaDistributionTest.java?rev=1378440&r1=1378439&r2=1378440&view=diff
==============================================================================
---
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/distribution/GammaDistributionTest.java
(original)
+++
commons/proper/math/trunk/src/test/java/org/apache/commons/math3/distribution/GammaDistributionTest.java
Wed Aug 29 04:28:47 2012
@@ -176,18 +176,40 @@ public class GammaDistributionTest exten
Assert.assertEquals(dist.getNumericalVariance(), 1.1d * 4.2d * 4.2d,
tol);
}
+ private static final double HALF_LOG_2_PI = 0.5 * FastMath.log(2.0 *
FastMath.PI);
+
+ public static double logGamma(double x) {
+ /*
+ * This is a copy of
+ * double Gamma.logGamma(double)
+ * prior to MATH-849
+ */
+ double ret;
+
+ if (Double.isNaN(x) || (x <= 0.0)) {
+ ret = Double.NaN;
+ } else {
+ double sum = Gamma.lanczos(x);
+ double tmp = x + Gamma.LANCZOS_G + .5;
+ ret = ((x + .5) * FastMath.log(tmp)) - tmp +
+ HALF_LOG_2_PI + FastMath.log(sum / x);
+ }
+
+ return ret;
+ }
+
public static double density(final double x, final double shape,
final double scale) {
/*
* This is a copy of
* double GammaDistribution.density(double)
- * prior to r1338548.
+ * prior to MATH-753.
*/
if (x < 0) {
return 0;
}
return FastMath.pow(x / scale, shape - 1) / scale *
- FastMath.exp(-x / scale) / FastMath.exp(Gamma.logGamma(shape));
+ FastMath.exp(-x / scale) / FastMath.exp(logGamma(shape));
}
/*
