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Posted to commits@commons.apache.org by lu...@apache.org on 2009/07/21 23:33:31 UTC
svn commit: r796545 -
/commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java
Author: luc
Date: Tue Jul 21 21:33:31 2009
New Revision: 796545
URL: http://svn.apache.org/viewvc?rev=796545&view=rev
Log:
added a base class for bits streams based modern pseudo random generators
Added:
commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java (with props)
Added: commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java?rev=796545&view=auto
==============================================================================
--- commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java (added)
+++ commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java Tue Jul 21 21:33:31 2009
@@ -0,0 +1,152 @@
+/*
+ * 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;
+
+import org.apache.commons.math.MathRuntimeException;
+
+/** Base class for random number generators that generates bits streams.
+
+ * @version $Revision$ $Date$
+ * @since 2.0
+
+ */
+public abstract class BitsStreamGenerator implements RandomGenerator {
+
+ /** Next gaussian. */
+ private double nextGaussian;
+
+ /** Creates a new random number generator.
+ */
+ public BitsStreamGenerator() {
+ nextGaussian = Double.NaN;
+ }
+
+ /** {@inheritDoc} */
+ public abstract void setSeed(int seed);
+
+ /** {@inheritDoc} */
+ public abstract void setSeed(int[] seed);
+
+ /** {@inheritDoc} */
+ public abstract void setSeed(long seed);
+
+ /** Generate next pseudorandom number.
+ * <p>This method is the core generation algorithm. It is used by all the
+ * public generation methods for the various primitive types {@link
+ * #nextBoolean()}, {@link #nextBytes(byte[])}, {@link #nextDouble()},
+ * {@link #nextFloat()}, {@link #nextGaussian()}, {@link #nextInt()},
+ * {@link #next(int)} and {@link #nextLong()}.</p>
+ * @param bits number of random bits to produce
+ */
+ protected abstract int next(int bits);
+
+ /** {@inheritDoc} */
+ public boolean nextBoolean() {
+ return next(1) != 0;
+ }
+
+ /** {@inheritDoc} */
+ public void nextBytes(byte[] bytes) {
+ int i = 0;
+ final int iEnd = bytes.length - 3;
+ while (i < iEnd) {
+ final int random = next(32);
+ bytes[i] = (byte) (random & 0xff);
+ bytes[i + 1] = (byte) ((random >> 8) & 0xff);
+ bytes[i + 2] = (byte) ((random >> 16) & 0xff);
+ bytes[i + 3] = (byte) ((random >> 24) & 0xff);
+ i += 4;
+ }
+ int random = next(32);
+ while (i < bytes.length) {
+ bytes[i++] = (byte) (random & 0xff);
+ random = random >> 8;
+ }
+ }
+
+ /** {@inheritDoc} */
+ public double nextDouble() {
+ final long high = ((long) next(26)) << 26;
+ final int low = next(26);
+ return (high | low) * 0x1.0p-52d;
+ }
+
+ /** {@inheritDoc} */
+ public float nextFloat() {
+ return next(23) * 0x1.0p-23f;
+ }
+
+ /** {@inheritDoc} */
+ public double nextGaussian() {
+
+ final double random;
+ if (Double.isNaN(nextGaussian)) {
+ // generate a new pair of gaussian numbers
+ final double x = nextDouble();
+ final double y = nextDouble();
+ final double alpha = 2 * Math.PI * x;
+ final double r = Math.sqrt(-2 * Math.log(y));
+ random = r * Math.cos(alpha);
+ nextGaussian = r * Math.sin(alpha);
+ } else {
+ // use the second element of the pair already generated
+ random = nextGaussian;
+ nextGaussian = Double.NaN;
+ }
+
+ return random;
+
+ }
+
+ /** {@inheritDoc} */
+ public int nextInt() {
+ return next(32);
+ }
+
+ /** {@inheritDoc} */
+ public int nextInt(int n) throws IllegalArgumentException {
+
+ if (n < 1) {
+ throw MathRuntimeException.createIllegalArgumentException(
+ "upper bound must be positive ({0})", n);
+ }
+
+ // find bit mask for n
+ int mask = n;
+ mask |= mask >> 1;
+ mask |= mask >> 2;
+ mask |= mask >> 4;
+ mask |= mask >> 8;
+ mask |= mask >> 16;
+
+ while (true) {
+ final int random = next(32) & mask;
+ if (random < n) {
+ return random;
+ }
+ }
+
+ }
+
+ /** {@inheritDoc} */
+ public long nextLong() {
+ final long high = ((long) next(32)) << 32;
+ final long low = ((long) next(32)) & 0xffffffffL;
+ return high | low;
+ }
+
+}
Propchange: commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java
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Propchange: commons/proper/math/trunk/src/java/org/apache/commons/math/random/BitsStreamGenerator.java
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svn:keywords = Author Date Id Revision