On 4 November 2011 17:44, Phil Steitz <phil.ste...@gmail.com> wrote: > On 11/4/11 10:25 AM, sebb wrote: >> On 4 November 2011 16:20, <pste...@apache.org> wrote: >>> Author: psteitz >>> Date: Fri Nov 4 16:20:05 2011 >>> New Revision: 1197626 >>> >>> URL: http://svn.apache.org/viewvc?rev=1197626&view=rev >>> Log: >>> Changed default non-secure generator to Well19937c and changed default >>> seeds to add system identity haschode to timestamp. JIRA: MATH-701. >> You've actually use the object hashcode - did you mean to use >> j.l.System.indentityHashcode() ? > > Yes, maybe I am wrong, but I thought that's what you got by default > when hashcode is not overridden. What we want is just something > that will be unique by instance (with high probability) and is > relatively fast to compute.
Yes, you do get that if it is not overridden, but if the hashcode is later overriden then: - the Javadoc will not be accurate - it may not be as quick to compute. It would be easy to overlook this in a future update, so I'd recommend using what the Javadoc says. > Phil >> >>> Modified: >>> >>> commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/RandomDataImpl.java >>> >>> Modified: >>> commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/RandomDataImpl.java >>> URL: >>> http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/RandomDataImpl.java?rev=1197626&r1=1197625&r2=1197626&view=diff >>> ============================================================================== >>> --- >>> commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/RandomDataImpl.java >>> (original) >>> +++ >>> commons/proper/math/trunk/src/main/java/org/apache/commons/math/random/RandomDataImpl.java >>> Fri Nov 4 16:20:05 2011 >>> @@ -49,7 +49,7 @@ import org.apache.commons.math.util.Resi >>> * instance to generate non-secure data and a {@link >>> java.security.SecureRandom} >>> * instance to provide data for the <code>nextSecureXxx</code> methods. If >>> no >>> * <code>RandomGenerator</code> is provided in the constructor, the default >>> is >>> - * to use a generator based on {@link java.util.Random}. To plug in a >>> different >>> + * to use a {@link Well19937c} generator. To plug in a different >>> * implementation, either implement <code>RandomGenerator</code> directly or >>> * extend {@link AbstractRandomGenerator}. >>> * <p> >>> @@ -81,10 +81,10 @@ import org.apache.commons.math.util.Resi >>> * When a new <code>RandomDataImpl</code> is created, the underlying random >>> * number generators are <strong>not</strong> initialized. If you do not >>> * explicitly seed the default non-secure generator, it is seeded with the >>> - * current time in milliseconds on first use. The same holds for the secure >>> - * generator. If you provide a <code>RandomGenerator</code> to the >>> constructor, >>> - * however, this generator is not reseeded by the constructor nor is it >>> reseeded >>> - * on first use.</li> >>> + * current time in milliseconds plus the system identity hash code on >>> first use. >>> + * The same holds for the secure generator. If you provide a >>> <code>RandomGenerator</code> >>> + * to the constructor, however, this generator is not reseeded by the >>> constructor >>> + * nor is it reseeded on first use.</li> >>> * <li> >>> * The <code>reSeed</code> and <code>reSeedSecure</code> methods delegate >>> to the >>> * corresponding methods on the underlying <code>RandomGenerator</code> and >>> @@ -827,7 +827,8 @@ public class RandomDataImpl implements R >>> /** >>> * Returns the RandomGenerator used to generate non-secure random data. >>> * <p> >>> - * Creates and initializes a default generator if null. >>> + * Creates and initializes a default generator if null. Uses a {@link >>> Well19937c} >>> + * generator with {@code System.currentTimeMillis() + hashCode()} as >>> the default seed. >>> * </p> >>> * >>> * @return the Random used to generate random data >>> @@ -835,8 +836,7 @@ public class RandomDataImpl implements R >>> */ >>> private RandomGenerator getRan() { >>> if (rand == null) { >>> - rand = new JDKRandomGenerator(); >>> - rand.setSeed(System.currentTimeMillis()); >>> + rand = new Well19937c(System.currentTimeMillis() + hashCode()); >>> } >>> return rand; >>> } >>> @@ -844,7 +844,8 @@ public class RandomDataImpl implements R >>> /** >>> * Returns the SecureRandom used to generate secure random data. >>> * <p> >>> - * Creates and initializes if null. >>> + * Creates and initializes if null. Uses >>> + * {@code System.currentTimeMillis() + hashCode()} as the default seed. >>> * </p> >>> * >>> * @return the SecureRandom used to generate secure random data >>> @@ -852,7 +853,7 @@ public class RandomDataImpl implements R >>> private SecureRandom getSecRan() { >>> if (secRand == null) { >>> secRand = new SecureRandom(); >>> - secRand.setSeed(System.currentTimeMillis()); >>> + secRand.setSeed(System.currentTimeMillis() + hashCode()); >>> } >>> return secRand; >>> } >>> >>> >>> >> --------------------------------------------------------------------- >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> For additional commands, e-mail: dev-h...@commons.apache.org >> >> > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
