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From pste...@apache.org
Subject svn commit: r1197896 - in /commons/proper/math/trunk/src: main/java/org/apache/commons/math/random/AbstractWell.java main/java/org/apache/commons/math/random/MersenneTwister.java site/xdoc/changes.xml
Date Sat, 05 Nov 2011 06:48:13 GMT
Author: psteitz
Date: Sat Nov  5 06:48:12 2011
New Revision: 1197896

URL: http://svn.apache.org/viewvc?rev=1197896&view=rev
Log:
Changed default seeding for MersenneTwister, WELL generators to add system identity hash code.
 JIRA: MATH-701.

Modified:
    commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/AbstractWell.java
    commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/MersenneTwister.java
    commons/proper/math/trunk/src/site/xdoc/changes.xml

Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/AbstractWell.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/AbstractWell.java?rev=1197896&r1=1197895&r2=1197896&view=diff
==============================================================================
--- commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/AbstractWell.java
(original)
+++ commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/AbstractWell.java
Sat Nov  5 06:48:12 2011
@@ -61,15 +61,15 @@ public abstract class AbstractWell exten
     protected final int[] i3;
 
     /** Creates a new random number generator.
-     * <p>The instance is initialized using the current time as the
-     * seed.</p>
+     * <p>The instance is initialized using the current time plus the
+     * system identity hash code of this instance as the seed.</p>
      * @param k number of bits in the pool (not necessarily a multiple of 32)
      * @param m1 first parameter of the algorithm
      * @param m2 second parameter of the algorithm
      * @param m3 third parameter of the algorithm
      */
     protected AbstractWell(final int k, final int m1, final int m2, final int m3) {
-        this(k, m1, m2, m3, System.currentTimeMillis());
+        this(k, m1, m2, m3, null);
     }
 
     /** Creates a new random number generator using a single int seed.
@@ -145,14 +145,15 @@ public abstract class AbstractWell exten
     /** Reinitialize the generator as if just built with the given int array seed.
      * <p>The state of the generator is exactly the same as a new
      * generator built with the same seed.</p>
-     * @param seed the initial seed (32 bits integers array), if null
-     * the seed of the generator will be related to the current time
+     * @param seed the initial seed (32 bits integers array). If null
+     * the seed of the generator will be the system time plus the system identity
+     * hash code of the instance.
      */
     @Override
     public void setSeed(final int[] seed) {
 
         if (seed == null) {
-            setSeed(System.currentTimeMillis());
+            setSeed(System.currentTimeMillis() + System.identityHashCode(this));
             return;
         }
 

Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/MersenneTwister.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/MersenneTwister.java?rev=1197896&r1=1197895&r2=1197896&view=diff
==============================================================================
--- commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/MersenneTwister.java
(original)
+++ commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/MersenneTwister.java
Sat Nov  5 06:48:12 2011
@@ -100,12 +100,12 @@ public class MersenneTwister extends Bit
     private int   mti;
 
     /** Creates a new random number generator.
-     * <p>The instance is initialized using the current time as the
-     * seed.</p>
+     * <p>The instance is initialized using the current time plus the
+     * system identity hash code of this instance as the seed.</p>
      */
     public MersenneTwister() {
         mt = new int[N];
-        setSeed(System.currentTimeMillis());
+        setSeed(System.currentTimeMillis() + System.identityHashCode(this));
     }
 
     /** Creates a new random number generator using a single int seed.
@@ -156,13 +156,14 @@ public class MersenneTwister extends Bit
      * <p>The state of the generator is exactly the same as a new
      * generator built with the same seed.</p>
      * @param seed the initial seed (32 bits integers array), if null
-     * the seed of the generator will be related to the current time
+     * the seed of the generator will be the current system time plus the
+     * system identity hash code of this instance
      */
     @Override
     public void setSeed(int[] seed) {
 
         if (seed == null) {
-            setSeed(System.currentTimeMillis());
+            setSeed(System.currentTimeMillis() + System.identityHashCode(this));
             return;
         }
 

Modified: commons/proper/math/trunk/src/site/xdoc/changes.xml
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/site/xdoc/changes.xml?rev=1197896&r1=1197895&r2=1197896&view=diff
==============================================================================
--- commons/proper/math/trunk/src/site/xdoc/changes.xml (original)
+++ commons/proper/math/trunk/src/site/xdoc/changes.xml Sat Nov  5 06:48:12 2011
@@ -52,6 +52,13 @@ The <action> type attribute can be add,u
     If the output is not quite correct, check for invisible trailing spaces!
      -->
     <release version="3.0" date="TBD" description="TBD">
+      <action dev="psteitz" type="update" issue="MATH-701">
+        Changed the default seed used for RandomDataImpl, AbstractWell and MersenneTwister
+        PRNGs to add the system identity hash code of the instance to the current system
+        time, so generators initialized with default seeds within system clock resolution
+        will generate different sequences. Changed the default non-secure generator used
+        by RandomDataImpl to Well19937c.
+      </action>
       <action dev="luc" type="fix" issue="MATH-695">
         Fixed an event resetting issue in ODE.
       </action>



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