1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 package org.apache.commons.rng.core.source32; 18 19 /** 20 * A Permuted Congruential Generator (PCG) that is composed of a 64-bit Linear Congruential 21 * Generator (LCG) combined with the XSH-RS (xorshift; random shift) output 22 * transformation to create 32-bit output. 23 * 24 * <p>State size is 128 bits and the period is 2<sup>64</sup>.</p> 25 * 26 * @see <a href="http://www.pcg-random.org/"> 27 * PCG, A Family of Better Random Number Generators</a> 28 * @since 1.3 29 */ 30 public class PcgXshRs32 extends AbstractPcg6432 { 31 /** 32 * Creates a new instance. 33 * 34 * @param seed Initial seed. 35 * If the length is larger than 2, only the first 2 elements will 36 * be used; if smaller, the remaining elements will be automatically set. 37 */ 38 public PcgXshRs32(long[] seed) { 39 super(seed); 40 } 41 42 /** {@inheritDoc} */ 43 @Override 44 protected int transform(long x) { 45 final int count = (int)(x >>> 61); 46 return (int)((x ^ (x >>> 22)) >>> (22 + count)); 47 } 48 }