v0.3 - simplified seed initialization for mersenne twister

Author: csoroiu

README.md

@@ -31,12 +31,12 @@ I got the idea of reversing the generators from several places, after I had to b
 <dependency>
     <groupId>ro.derbederos</groupId>
     <artifactId>untwist</artifactId>
-    <version>0.2</version>
+    <version>0.3</version>
 </dependency>
 ```
 #### Gradle dependency
 ```groovy
-compile 'ro.derbederos:untwist:0.2'
+compile 'ro.derbederos:untwist:0.3'
 ```
 
 Enjoy using them!

pom.xml

@@ -22,7 +22,7 @@
 
     <groupId>ro.derbederos</groupId>
     <artifactId>untwist</artifactId>
-    <version>0.2</version>
+    <version>0.3</version>
 
     <name>untwist</name>
     <description>Java 8+ collection of PRNG's from CLR (.NET), FreePascal, TurboPascal, Python.</description>

src/main/java/ro/derbederos/untwist/ArrayUtils.java

@@ -56,12 +56,11 @@ public static int[] getTree(int n, RandomGenerator randomizer) {
     }
 
     public static int[] getPermutation(int n, RandomGenerator randomizer) {
-        // http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
         return getPermutation(n, 1, randomizer);
     }
 
     public static int[] getPermutationInsideOut(int n, RandomGenerator randomizer) {
-        // http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
+        // https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_.22inside-out.22_algorithm
         int[] perm = new int[n];
         for (int i = 1; i < n; i++) {
             int j = randomizer.nextInt(i + 1);

src/main/java/ro/derbederos/untwist/FreePascalRandom.java

@@ -76,14 +76,6 @@ public FreePascalRandom(long seed) {
         super(seed);
     }
 
-    /**
-     * {@inheritDoc}
-     */
-    @Override
-    public void setSeed(int seed) {
-        super.setSeed(seed);
-    }
-
     /**
      * {@inheritDoc}
      * <p>
@@ -96,7 +88,7 @@ public void setSeed(long seed) {
         if (high == 0) {
             setSeed((int) seed);
         } else {
-            setSeed(new int[]{high, (int) (seed & 0xFFFFFFFFL)});
+            setSeed(new int[]{(int) (seed & 0xFFFFFFFFL), high});
         }
     }
 
@@ -110,14 +102,18 @@ public void setSeed(int[] seed) {
         if (seed.length == 1) {
             setSeed(seed[0]);
         } else {
-            super.setSeed(reverseArray(seed));
+            super.setSeed(seed);
         }
     }
 
     /**
      * {@inheritDoc}
      * <p>
      * It uses only 32 bits to generate a double precision float number.
+     * <p>
+     * This method is the same as {@code genrand_real2} method in the
+     * <a href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c">original implementation</a>
+     * of theMersenne Twister.
      */
     @Override
     public double nextDouble() {
@@ -138,6 +134,10 @@ public double prevDouble() {
      * {@inheritDoc}
      * <p>
      * It simply calls {@link #nextDouble()} and does a cast.
+     * <p>
+     * This method is the same as {@code genrand_real2} method in the
+     * <a href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c">original implementation</a>
+     * of theMersenne Twister.
      */
     @Override
     public float nextFloat() {
@@ -238,13 +238,4 @@ public long prevLong(long n) throws IllegalArgumentException {
             return 0;
         }
     }
-
-    private static int[] reverseArray(int[] seed) {
-        int[] seedReversed = new int[seed.length];
-        int j = seed.length;
-        for (int i = 0; i < seedReversed.length; i++) {
-            seedReversed[i] = seed[--j];
-        }
-        return seedReversed;
-    }
 }

src/main/java/ro/derbederos/untwist/MersenneTwisterPy3k.java

@@ -22,9 +22,11 @@
  * A Mersenne Twister subclass which generates the same numbers as the Python 3 implementation.
  * Source code uses as reference is part of the files:
  * <ul>
- * <li><a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.</li>
- * <li><a href="https://svn.python.org/projects/python/trunk/Lib/random.py">random.py</a>.</li>
+ * <li><a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.</li>
+ * <li><a href="https://github.com/python/cpython/blob/master/Lib/random.py">random.py</a>.</li>
+ * <li><a href="https://github.com/python/cpython/blob/master/Lib/test/test_random.py">test_random.py</a>.</li>
  * </ul>
+ * Test
  */
 public class MersenneTwisterPy3k extends ReversibleMersenneTwister {
 
@@ -92,28 +94,19 @@ public void setSeed(long seed) {
         if (high == 0) {
             setSeed(new int[]{(int) seed});
         } else {
-            setSeed(new int[]{high, (int) (seed & 0xFFFFFFFFL)});
+            setSeed(new int[]{(int) (seed & 0xFFFFFFFFL), high});
         }
     }
 
-    /**
-     * {@inheritDoc}
-     * <p>
-     * Reverses the bytes in the {@code seed} array and calls{@code super.setSeed(int[])}.
-     * Python Mersenne Twister uses a different byte ordering for the {@code seed} array.
-     */
-    @Override
-    public void setSeed(int[] seed) {
-        // for python compatibility where the seed is a number (big integer)
-        // and it is big endian
-        super.setSeed(reverseArray(seed));
-    }
-
     /**
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_random} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
+     * <p>
+     * This method is the same as {@code genrand_res53} method in the
+     * <a href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c">original implementation</a>
+     * of the Mersenne Twister.
      */
     @Override
     public double nextDouble() {
@@ -124,7 +117,7 @@ public double nextDouble() {
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_random} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public double prevDouble() {
@@ -135,6 +128,13 @@ public double prevDouble() {
      * {@inheritDoc}
      * <p>
      * It simply calls {@link #nextDouble()} and does a cast.
+     * <p>
+     * Source code: {@code random_random} method in the file
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
+     * <p>
+     * This method is the same as {@code genrand_res53} method in the
+     * <a href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c">original implementation</a>
+     * of the Mersenne Twister.
      */
     @Override
     public float nextFloat() {
@@ -155,7 +155,7 @@ public float prevFloat() {
      * {@inheritDoc}
      * <p>
      * Source code: {@code _randbelow} method in the file
-     * <a href="https://svn.python.org/projects/python/trunk/Lib/random.py">random.py</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Lib/random.py">random.py</a>.
      */
     @Override
     public int nextInt(int n) throws IllegalArgumentException {
@@ -174,7 +174,7 @@ public int nextInt(int n) throws IllegalArgumentException {
      * {@inheritDoc}
      * <p>
      * Source code: {@code _randbelow} method in the file
-     * <a href="https://svn.python.org/projects/python/trunk/Lib/random.py">random.py</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Lib/random.py">random.py</a>.
      */
     @Override
     public int prevInt(int n) throws IllegalArgumentException {
@@ -196,7 +196,7 @@ public int prevInt(int n) throws IllegalArgumentException {
      * when called for 8 bytes.
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public long nextLong() {
@@ -212,7 +212,7 @@ public long nextLong() {
      * when called for 8 bytes.
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public long prevLong() {
@@ -225,7 +225,7 @@ public long prevLong() {
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public void nextBytes(byte[] bytes, int start, int len) {
@@ -243,7 +243,7 @@ public void nextBytes(byte[] bytes, int start, int len) {
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public void nextBytes(byte[] bytes) {
@@ -275,7 +275,7 @@ private void nextBytesFill(byte[] bytes, int start, int len) {
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public void prevBytes(byte[] bytes) {
@@ -286,7 +286,7 @@ public void prevBytes(byte[] bytes) {
      * {@inheritDoc}
      * <p>
      * Source code: {@code random_getrandbits} method in the file
-     * <a href="http://svn.python.org/projects/python/trunk/Modules/_randommodule.c">_randommodule.c</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Modules/_randommodule.c">_randommodule.c</a>.
      */
     @Override
     public void prevBytes(byte[] bytes, int start, int len) {
@@ -328,7 +328,7 @@ private void prevBytesFill(byte[] bytes, int start, int len) {
      * {@inheritDoc}
      * <p>
      * Source code: {@code _randbelow} method in the file
-     * <a href="https://svn.python.org/projects/python/trunk/Lib/random.py">random.py</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Lib/random.py">random.py</a>.
      */
     @Override
     public long nextLong(long n) throws IllegalArgumentException {
@@ -350,7 +350,7 @@ public long nextLong(long n) throws IllegalArgumentException {
      * {@inheritDoc}
      * <p>
      * Source code: {@code _randbelow} method in the file
-     * <a href="https://svn.python.org/projects/python/trunk/Lib/random.py">random.py</a>.
+     * <a href="https://github.com/python/cpython/blob/master/Lib/random.py">random.py</a>.
      */
     @Override
     public long prevLong(long n) throws IllegalArgumentException {
@@ -369,13 +369,4 @@ public long prevLong(long n) throws IllegalArgumentException {
         throw new IllegalArgumentException("n must be strictly positive");
 
     }
-
-    private static int[] reverseArray(int[] seed) {
-        int[] seedReversed = new int[seed.length];
-        int j = seed.length;
-        for (int i = 0; i < seedReversed.length; i++) {
-            seedReversed[i] = seed[--j];
-        }
-        return seedReversed;
-    }
 }

src/main/java/ro/derbederos/untwist/ReversibleMersenneTwister.java

@@ -21,6 +21,9 @@
 
 
 /**
+ * This class is a copy of {@link org.apache.commons.math3.random.MersenneTwister}
+ * which also implements {@link ReverseRandomGenerator}.
+ * <p>
  * This class implements a powerful pseudo-random number generator
  * developed by Makoto Matsumoto and Takuji Nishimura during
  * 1996-1997.