001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018package org.apache.commons.rng.core.source64; 019 020import java.util.Arrays; 021import org.apache.commons.rng.core.util.NumberFactory; 022 023/** 024 * A fast RNG. 025 * 026 * @see <a href="http://xorshift.di.unimi.it/xorshift1024star.c"> 027 * Original source code</a> 028 * 029 * @see <a href="https://en.wikipedia.org/wiki/Xorshift">Xorshift (Wikipedia)</a> 030 * @since 1.0 031 */ 032public class XorShift1024Star extends LongProvider { 033 /** Size of the state vector. */ 034 private static final int SEED_SIZE = 16; 035 /** State. */ 036 private final long[] state = new long[SEED_SIZE]; 037 /** Index in "state" array. */ 038 private int index; 039 040 /** 041 * Creates a new instance. 042 * 043 * @param seed Initial seed. 044 * If the length is larger than 16, only the first 16 elements will 045 * be used; if smaller, the remaining elements will be automatically 046 * set. 047 */ 048 public XorShift1024Star(long[] seed) { 049 setSeedInternal(seed); 050 } 051 052 /** {@inheritDoc} */ 053 @Override 054 protected byte[] getStateInternal() { 055 final long[] s = Arrays.copyOf(state, SEED_SIZE + 1); 056 s[SEED_SIZE] = index; 057 058 return NumberFactory.makeByteArray(s); 059 } 060 061 /** {@inheritDoc} */ 062 @Override 063 protected void setStateInternal(byte[] s) { 064 checkStateSize(s, (SEED_SIZE + 1) * 8); 065 066 final long[] tmp = NumberFactory.makeLongArray(s); 067 068 System.arraycopy(tmp, 0, state, 0, SEED_SIZE); 069 index = (int) tmp[SEED_SIZE]; 070 } 071 072 /** 073 * Seeds the RNG. 074 * 075 * @param seed Seed. 076 */ 077 private void setSeedInternal(long[] seed) { 078 // Reset the whole state of this RNG (i.e. "state" and "index"). 079 // Filling procedure is not part of the reference code. 080 fillState(state, seed); 081 index = 0; 082 } 083 084 /** {@inheritDoc} */ 085 @Override 086 public long next() { 087 final long s0 = state[index]; 088 long s1 = state[index = (index + 1) & 15]; 089 s1 ^= s1 << 31; // a 090 state[index] = s1 ^ s0 ^ (s1 >>> 11) ^ (s0 >>> 30); // b,c 091 return state[index] * 1181783497276652981L; 092 } 093}