MATH-1337

Adaptor from new to old API.
Class is deprecated: it is temporarily provided to allow testing of the new RNGs (in user applications) with minimal changes.

src/main/java/org/apache/commons/math4/random/RngAdaptor.java

@@ -0,0 +1,229 @@
+/*
+ * 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.math4.random;
+
+import java.io.Serializable;
+import java.io.IOException;
+import java.io.ObjectOutputStream;
+import java.io.ObjectInputStream;
+import org.apache.commons.math4.util.FastMath;
+import org.apache.commons.math4.rng.UniformRandomProvider;
+import org.apache.commons.math4.rng.RandomSource;
+
+/**
+ * Adaptor that delegates to a {@link UniformRandomProvider} instance.
+ * <p>
+ * It is provided for users who wish to test the new RNG implementations
+ * the <i>current</i> generators (up to version 3.6 of Commons Math) in
+ * codes that require the {@code RandomGenerator} interface.
+ * </p>
+ * <p>
+ * Applications should upgrade to use the new generators ASAP.
+ * If problems are found that jeopardize the upgrade, please report them
+ * on the project's
+ * <a href="https://issues.apache.org/jira/browse/MATH">
+ *  issue tracking system</a>.
+ * </p>
+ *
+ * <p>
+ * <b>Notes:</b>
+ * <ul>
+ *  <li>
+ *   The
+ *   {@link RandomGenerator#setSeed(int) setSeed(int)},
+ *   {@link RandomGenerator#setSeed(int[]) setSeed(int[])} and
+ *   {@link RandomGenerator#setSeed(long) setSeed(long)}
+ *   methods of the {@link RandomGenerator} are not part of the
+ *   {@link UniformRandomProvider new API}.
+ *  </li>
+ *  <li>
+ *   The new RNG implementations are not {@code Serializable}.
+ *   Use {@link RandomSource#saveState(UniformRandomProvider)}
+ *   instead.
+ *  </li>
+ *  <li>
+ *   {@link RandomGenerator#nextGaussian() nextGaussian()} is not
+ *   part of the {@link UniformRandomProvider new API} as it defines
+ *   a "post-processing" of the output of a <i>uniform</i> RNG in
+ *   order to follow a different distribution.
+ *  </li>
+ * </p>
+ *
+ * @since 4.0
+ *
+ * @deprecated As of 4.0. This class is made available for testing
+ * the {@link RandomSource new RNG implementations} in existing
+ * applications.
+ * It will be removed in the next major release.
+ */
+@Deprecated
+public final class RngAdaptor
+    implements RandomGenerator,
+               Serializable {
+    /** Serializable version identifier. */
+    private static final long serialVersionUID = 12345L;
+    /** Source. */
+    private final RandomSource source;
+    /** Delegate. */
+    private transient UniformRandomProvider delegate;
+    /** Next gaussian. */
+    private double nextGaussian = Double.NaN;
+
+    /**
+     * Creates a new instance.
+     *
+     * @param source Source of randomness.
+     */
+    public RngAdaptor(RandomSource source) {
+        this(source, null);
+    }
+
+    /**
+     * Creates a new instance.
+     *
+     * @param source Source of randomness.
+     * @param seed Seed.  Can be {@code null}.
+     */
+    public RngAdaptor(RandomSource source,
+                      Object seed) {
+        this.source = source;
+        delegate = RandomSource.create(source, seed);
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void setSeed(int seed) {
+        delegate = RandomSource.create(source, seed);
+        clear();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void setSeed(int[] seed) {
+        delegate = RandomSource.create(source, seed);
+        clear();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void setSeed(long seed) {
+        delegate = RandomSource.create(source, seed);
+        clear();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public boolean nextBoolean() {
+        return delegate.nextBoolean();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void nextBytes(byte[] bytes) {
+        delegate.nextBytes(bytes);
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public double nextDouble() {
+        return delegate.nextDouble();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public float nextFloat() {
+        return delegate.nextFloat();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    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 * FastMath.PI * x;
+            final double r = FastMath.sqrt(-2 * FastMath.log(y));
+            random = r * FastMath.cos(alpha);
+            nextGaussian = r * FastMath.sin(alpha);
+        } else {
+            // use the second element of the pair already generated
+            random = nextGaussian;
+            nextGaussian = Double.NaN;
+        }
+
+        return random;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public int nextInt() {
+        return delegate.nextInt();
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public int nextInt(int n) {
+        return delegate.nextInt(n);
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public long nextLong() {
+        return delegate.nextLong();
+    }
+
+    /**
+     * Clears the cache used by the default implementation of
+     * {@link #nextGaussian}.
+     */
+    private void clear() {
+        nextGaussian = Double.NaN;
+    }
+
+    /**
+     * @param out Output stream.
+     * @throws IOException if an error occurs.
+     */
+    private void writeObject(ObjectOutputStream out)
+        throws IOException {
+        // Write non-transient fields.
+        out.defaultWriteObject();
+
+        // Save current state.
+        out.writeObject(RandomSource.saveState(delegate));
+   }
+
+    /**
+     * @param in Input stream.
+     * @throws IOException if an error occurs.
+     * @throws ClassNotFoundException if an error occurs.
+     */
+    private void readObject(ObjectInputStream in)
+        throws IOException,
+               ClassNotFoundException {
+        // Read non-transient fields.
+        in.defaultReadObject();
+
+        // Recreate the "delegate" from serialized info.
+        delegate = RandomSource.create(source);
+        // And restore its state.
+        final RandomSource.State state = (RandomSource.State) in.readObject();
+        RandomSource.restoreState(delegate, state);
+    }
+}