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.simple.internal; 18 19 import org.apache.commons.rng.core.source64.SplitMix64; 20 import org.apache.commons.rng.core.util.NumberFactory; 21 22 /** 23 * Uses a {@code long} value to seed a {@link SplitMix64} RNG and 24 * create a {@code int[]} with the requested number of random 25 * values. 26 * 27 * @since 1.0 28 */ 29 public class Long2IntArray implements Seed2ArrayConverter<Long, int[]> { 30 /** Size of the output array. */ 31 private final int size; 32 33 /** 34 * @param size Size of the output array. 35 */ 36 public Long2IntArray(int size) { 37 this.size = size; 38 } 39 40 /** {@inheritDoc} */ 41 @Override 42 public int[] convert(Long seed) { 43 return convertSeed(seed, size); 44 } 45 46 /** 47 * {@inheritDoc} 48 * 49 * @since 1.3 50 */ 51 @Override 52 public int[] convert(Long seed, int outputSize) { 53 return convertSeed(seed, outputSize); 54 } 55 56 /** 57 * Convert the seed. 58 * 59 * @param seed Input seed. 60 * @param size Output array size. 61 * @return the converted seed. 62 */ 63 private static int[] convertSeed(Long seed, int size) { 64 final int[] out = new int[size]; 65 final SplitMix64 rng = new SplitMix64(seed); 66 // Fill pairs of ints from a long. 67 // The array is filled from the end towards the start. 68 for (int i = size - 1; i > 0; i -= 2) { 69 final long v = rng.nextLong(); 70 out[i] = NumberFactory.extractHi(v); 71 out[i - 1] = NumberFactory.extractLo(v); 72 } 73 // An odd size requires a final single int at the start 74 if ((size & 1) == 1) { 75 out[0] = NumberFactory.extractHi(rng.nextLong()); 76 } 77 return out; 78 } 79 }