| /* |
| * 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 java.util.Arrays; |
| import org.apache.commons.rng.core.util.NumberFactory; |
| |
| /** |
| * A fast RNG. |
| * |
| * @see <a href="http://xorshift.di.unimi.it/xorshift1024star.c"> |
| * Original source code</a> |
| * |
| * @see <a href="https://en.wikipedia.org/wiki/Xorshift">Xorshift (Wikipedia)</a> |
| * @since 1.0 |
| */ |
| public class XorShift1024Star extends LongProvider { |
| /** Size of the state vector. */ |
| private static final int SEED_SIZE = 16; |
| /** State. */ |
| private final long[] state = new long[SEED_SIZE]; |
| /** Index in "state" array. */ |
| private int index; |
| |
| /** |
| * Creates a new instance. |
| * |
| * @param seed Initial seed. |
| * If the length is larger than 16, only the first 16 elements will |
| * be used; if smaller, the remaining elements will be automatically |
| * set. |
| */ |
| public XorShift1024Star(long[] seed) { |
| setSeedInternal(seed); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected byte[] getStateInternal() { |
| final long[] s = Arrays.copyOf(state, SEED_SIZE + 1); |
| s[SEED_SIZE] = index; |
| |
| return NumberFactory.makeByteArray(s); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected void setStateInternal(byte[] s) { |
| checkStateSize(s, (SEED_SIZE + 1) * 8); |
| |
| final long[] tmp = NumberFactory.makeLongArray(s); |
| |
| System.arraycopy(tmp, 0, state, 0, SEED_SIZE); |
| index = (int) tmp[SEED_SIZE]; |
| } |
| |
| /** |
| * Seeds the RNG. |
| * |
| * @param seed Seed. |
| */ |
| private void setSeedInternal(long[] seed) { |
| // Reset the whole state of this RNG (i.e. "state" and "index"). |
| // Filling procedure is not part of the reference code. |
| fillState(state, seed); |
| index = 0; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public long next() { |
| final long s0 = state[index]; |
| long s1 = state[index = (index + 1) & 15]; |
| s1 ^= s1 << 31; // a |
| state[index] = s1 ^ s0 ^ (s1 >>> 11) ^ (s0 >>> 30); // b,c |
| return state[index] * 1181783497276652981L; |
| } |
| } |