aherbert commented on a change in pull request #56: RNG: 84 - Added members of the PCG suite of generators. URL: https://github.com/apache/commons-rng/pull/56#discussion_r308007144
########## File path: commons-rng-core/src/main/java/org/apache/commons/rng/core/source32/AbstractPcgMcg6432.java ########## @@ -0,0 +1,81 @@ +/* + * 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.rng.core.source32; + +import org.apache.commons.rng.core.util.NumberFactory; +/** + * This class aids in implementation of the Multiplicative congruential generator (MCG) + * versions of the PCG suite of generators, a family of simple fast space-efficient statistically + * good algorithms for random number generation. + * + * @see <a href="http://www.pcg-random.org/";> + * PCG, A Family of Better Random Number Generators</a> + * @since 1.3 + */ +abstract class AbstractPcgMcg6432 extends IntProvider { + + /** Displays the current state. */ + private long state; + + /** + * Creates a new instance. + * + * @param seed Initial seed. + */ + AbstractPcgMcg6432(Long seed) { + state = seed | 3; + } + + /** + * Provides the next state of the MCG. + * @param input - The previous state of the generator. + * @return Next state of the MCG. + */ + private long bump(long input) { + return input * 6364136223846793005L; + } + + /** {@inheritDoc} */ + @Override + public int next() { + final long x = state; + state = bump(state); + return transform(x); + } + + /** + * The transformation function shall vary with respect to different generators. + * @param x The input. + * @return The output of the generator. + */ + protected abstract int transform(long x); + + /** {@inheritDoc} */ + @Override + protected byte[] getStateInternal() { + return composeStateInternal(NumberFactory.makeByteArray(state), + super.getStateInternal()); + } + + /** {@inheritDoc} */ + @Override + protected void setStateInternal(byte[] s) { + final byte[][] d = splitStateInternal(s, 8); + state = NumberFactory.makeLong(d[0]); Review comment: For consistency with the LCG version (which transforms the state when it is read back in) can you apply the transform to set the lower 2 bits to 1 here, i.e. ` | 3`. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
