AbhishekSinghDhadwal 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_r305745924
########## File path: commons-rng-core/src/main/java/org/apache/commons/rng/core/source64/PcgRxsMXs64.java ########## @@ -0,0 +1,100 @@ +/* + * 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.source64; + +import org.apache.commons.rng.core.util.NumberFactory; +/** + * RXS M XS -- random xorshift, mcg multiply, fixed xorshift. + * State size is 64 bits and the period is 2<sup>64</sup>. + * @see <a href="http://www.pcg-random.org/";> + * PCG, A Family of Better Random Number Generators</a> + * @since 1.3 + */ +public class PcgRxsMXs64 extends LongProvider { + + /** Size of the state array. */ + private static final int SEED_SIZE = 2; + + /** Displays the current state. */ + private long state; + + /** Used as a part of the LCG. */ + private long increment; + + /** + * Creates a new instance. + * + * @param seed Initial seed. + * If the length is larger than 2, only the first 2 elements will + * be used; if smaller, the remaining elements will be automatically set. + */ + public PcgRxsMXs64(long[] seed) { + if (seed.length < SEED_SIZE) { + final long[] tmp = new long[SEED_SIZE]; + fillState(tmp, seed); + setSeedInternal(tmp); + } else { + setSeedInternal(seed); + } + } + + /** + * Modifies input parameters into current state. + * @param seed the new seed. + */ + private void setSeedInternal(long[] seed) { + this.increment = (seed[1] << 1) | 1; + this.state = bump(seed[0] + this.increment); + } + + /** + * Provides the next state of the LCG. + * @param input - The previous state of the generator. + * @return Next state of the LCG. + */ + private long bump(long input) { + return input * 6364136223846793005L + increment; + } + + /** {@inheritDoc} */ + @Override + public long next() { + final long x = state; + state = bump(state); + final long word = ((x >>> ((x >>> 59) + 5)) ^ x) * -5840758589994634535L; + return (word >>> 43) ^ word; + } + + /** {@inheritDoc} */ + @Override + protected byte[] getStateInternal() { + return composeStateInternal(NumberFactory.makeByteArray( Review comment: Done. ---------------------------------------------------------------- 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
