Repository: commons-numbers Updated Branches: refs/heads/master 1aa1ddcd5 -> d79edb264
NUMBERS-33: Small changes. Made "LanczosApproximation" public (used by "Commons Math"). Moved "Lanczos constant" staic field to appropriate class and provided accessor. Project: http://git-wip-us.apache.org/repos/asf/commons-numbers/repo Commit: http://git-wip-us.apache.org/repos/asf/commons-numbers/commit/d79edb26 Tree: http://git-wip-us.apache.org/repos/asf/commons-numbers/tree/d79edb26 Diff: http://git-wip-us.apache.org/repos/asf/commons-numbers/diff/d79edb26 Branch: refs/heads/master Commit: d79edb264f71db3e88779efe2681fa8c48310c3c Parents: 1aa1ddc Author: Gilles Sadowski <gil...@harfang.homelinux.org> Authored: Sat May 13 16:20:25 2017 +0200 Committer: Gilles Sadowski <gil...@harfang.homelinux.org> Committed: Sat May 13 16:20:25 2017 +0200 ---------------------------------------------------------------------- .../org/apache/commons/numbers/gamma/Gamma.java | 4 +-- .../numbers/gamma/LanczosApproximation.java | 11 ++++++- .../numbers/gamma/LanczosApproximationTest.java | 30 ++++++++++++++++++++ 3 files changed, 41 insertions(+), 4 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/commons-numbers/blob/d79edb26/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Gamma.java ---------------------------------------------------------------------- diff --git a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Gamma.java b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Gamma.java index d2bb559..3fbb838 100644 --- a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Gamma.java +++ b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/Gamma.java @@ -31,8 +31,6 @@ package org.apache.commons.numbers.gamma; * </p> */ public class Gamma { - /** \( g = \frac{607}{128} \). */ - private static final double LANCZOS_G = 607d / 128d; /** √(2π). */ private static final double SQRT_TWO_PI = 2.506628274631000502; @@ -86,7 +84,7 @@ public class Gamma { return 1 / (prod * (1 + InvGamma1pm1.value(t))); } } else { - final double y = absX + LANCZOS_G + 0.5; + final double y = absX + LanczosApproximation.g() + 0.5; final double gammaAbs = SQRT_TWO_PI / absX * Math.pow(y, absX + 0.5) * Math.exp(-y) * LanczosApproximation.value(absX); http://git-wip-us.apache.org/repos/asf/commons-numbers/blob/d79edb26/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/LanczosApproximation.java ---------------------------------------------------------------------- diff --git a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/LanczosApproximation.java b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/LanczosApproximation.java index 0fad0ae..fec4ac3 100644 --- a/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/LanczosApproximation.java +++ b/commons-numbers-gamma/src/main/java/org/apache/commons/numbers/gamma/LanczosApproximation.java @@ -31,7 +31,9 @@ package org.apache.commons.numbers.gamma; * <a href="http://my.fit.edu/~gabdo/gamma.txt";>Note on the computation * of the convergent Lanczos complex Gamma approximation</a>. */ -class LanczosApproximation { +public class LanczosApproximation { + /** \( g = \frac{607}{128} \). */ + private static final double LANCZOS_G = 607d / 128d; /** Lanczos coefficients. */ private static final double[] LANCZOS = { 0.99999999999999709182, @@ -64,4 +66,11 @@ class LanczosApproximation { } return sum + LANCZOS[0]; } + + /** + * @return the Lanczos constant \( g = \frac{607}{128} \). + */ + public static double g() { + return LANCZOS_G; + } } http://git-wip-us.apache.org/repos/asf/commons-numbers/blob/d79edb26/commons-numbers-gamma/src/test/java/org/apache/commons/numbers/gamma/LanczosApproximationTest.java ---------------------------------------------------------------------- diff --git a/commons-numbers-gamma/src/test/java/org/apache/commons/numbers/gamma/LanczosApproximationTest.java b/commons-numbers-gamma/src/test/java/org/apache/commons/numbers/gamma/LanczosApproximationTest.java new file mode 100644 index 0000000..bd33ee0 --- /dev/null +++ b/commons-numbers-gamma/src/test/java/org/apache/commons/numbers/gamma/LanczosApproximationTest.java @@ -0,0 +1,30 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.numbers.gamma; + +import org.junit.Assert; +import org.junit.Test; + +/** + * Tests for {@link LanczosApproximation}. + */ +public class LanczosApproximationTest { + @Test + public void testG() { + Assert.assertEquals(607d / 128d, LanczosApproximation.g(), 0d); + } +}
