From dee0849a9704d532af0b550146cbafbaa6ee1d19 Mon Sep 17 00:00:00 2001
From: Raymond <siuchow@google.com>
Date: Thu, 2 Apr 2015 10:43:13 -0700
Subject: third party library: apache-commons-math

Change-Id: I52a325624a7f0dd652b362a9840626d6d9f3c42b
---
 .../org/apache/commons/math/random/Well44497b.java | 119 +++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 src/main/java/org/apache/commons/math/random/Well44497b.java

(limited to 'src/main/java/org/apache/commons/math/random/Well44497b.java')

diff --git a/src/main/java/org/apache/commons/math/random/Well44497b.java b/src/main/java/org/apache/commons/math/random/Well44497b.java
new file mode 100644
index 0000000..28b5dbb
--- /dev/null
+++ b/src/main/java/org/apache/commons/math/random/Well44497b.java
@@ -0,0 +1,119 @@
+/*
+ * 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.math.random;
+
+
+/** This class implements the WELL44497b pseudo-random number generator
+ * from Fran&ccedil;ois Panneton, Pierre L'Ecuyer and Makoto Matsumoto.
+
+ * <p>This generator is described in a paper by Fran&ccedil;ois Panneton,
+ * Pierre L'Ecuyer and Makoto Matsumoto <a
+ * href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng.pdf">Improved
+ * Long-Period Generators Based on Linear Recurrences Modulo 2</a> ACM
+ * Transactions on Mathematical Software, 32, 1 (2006). The errata for the paper
+ * are in <a href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng-errata.txt">wellrng-errata.txt</a>.</p>
+
+ * @see <a href="http://www.iro.umontreal.ca/~panneton/WELLRNG.html">WELL Random number generator</a>
+ * @version $Revision: 1003892 $ $Date: 2010-10-02 23:28:56 +0200 (sam. 02 oct. 2010) $
+ * @since 2.2
+
+ */
+public class Well44497b extends AbstractWell {
+
+    /** Serializable version identifier. */
+    private static final long serialVersionUID = 4032007538246675492L;
+
+    /** Number of bits in the pool. */
+    private static final int K = 44497;
+
+    /** First parameter of the algorithm. */
+    private static final int M1 = 23;
+
+    /** Second parameter of the algorithm. */
+    private static final int M2 = 481;
+
+    /** Third parameter of the algorithm. */
+    private static final int M3 = 229;
+
+    /** Creates a new random number generator.
+     * <p>The instance is initialized using the current time as the
+     * seed.</p>
+     */
+    public Well44497b() {
+        super(K, M1, M2, M3);
+    }
+
+    /** Creates a new random number generator using a single int seed.
+     * @param seed the initial seed (32 bits integer)
+     */
+    public Well44497b(int seed) {
+        super(K, M1, M2, M3, seed);
+    }
+
+    /** Creates a new random number generator using an int array seed.
+     * @param seed the initial seed (32 bits integers array), if null
+     * the seed of the generator will be related to the current time
+     */
+    public Well44497b(int[] seed) {
+        super(K, M1, M2, M3, seed);
+    }
+
+    /** Creates a new random number generator using a single long seed.
+     * @param seed the initial seed (64 bits integer)
+     */
+    public Well44497b(long seed) {
+        super(K, M1, M2, M3, seed);
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    protected int next(final int bits) {
+
+        // compute raw value given by WELL44497a generator
+        // which is NOT maximally-equidistributed
+        final int indexRm1 = iRm1[index];
+        final int indexRm2 = iRm2[index];
+
+        final int v0       = v[index];
+        final int vM1      = v[i1[index]];
+        final int vM2      = v[i2[index]];
+        final int vM3      = v[i3[index]];
+
+        // the values below include the errata of the original article
+        final int z0       = (0xFFFF8000 & v[indexRm1]) ^ (0x00007FFF & v[indexRm2]);
+        final int z1       = (v0 ^ (v0 << 24))  ^ (vM1 ^ (vM1 >>> 30));
+        final int z2       = (vM2 ^ (vM2 << 10)) ^ (vM3 << 26);
+        final int z3       = z1      ^ z2;
+        final int z2Prime  = ((z2 << 9) ^ (z2 >>> 23)) & 0xfbffffff;
+        final int z2Second = ((z2 & 0x00020000) != 0) ? (z2Prime ^ 0xb729fcec) : z2Prime;
+        int z4             = z0 ^ (z1 ^ (z1 >>> 20)) ^ z2Second ^ z3;
+
+        v[index]     = z3;
+        v[indexRm1]  = z4;
+        v[indexRm2] &= 0xFFFF8000;
+        index        = indexRm1;
+
+        // add Matsumoto-Kurita tempering
+        // to get a maximally-equidistributed generator
+        z4 = z4 ^ ((z4 <<  7) & 0x93dd1400);
+        z4 = z4 ^ ((z4 << 15) & 0xfa118000);
+
+        return z4 >>> (32 - bits);
+
+    }
+
+}
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