| /* |
| * 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; |
| |
| /** |
| * Implement the Small, Fast, Counting (SFC) 64-bit generator of Chris Doty-Humphrey. |
| * The original source is the PractRand test suite by the same author. |
| * |
| * <p>The state size is 256-bits; the period is a minimum of 2<sup>64</sup> and an |
| * average of approximately 2<sup>255</sup>.</p> |
| * |
| * @see <a href="http://pracrand.sourceforge.net/">PractRand</a> |
| * @since 1.3 |
| */ |
| public class DotyHumphreySmallFastCounting64 extends LongProvider { |
| /** Size of the seed. */ |
| private static final int SEED_SIZE = 3; |
| |
| /** State a. */ |
| private long a; |
| /** State b. */ |
| private long b; |
| /** State c. */ |
| private long c; |
| /** Counter. */ |
| private long counter; |
| |
| /** |
| * Creates an instance with the given seed. |
| * |
| * @param seed Initial seed. |
| * If the length is larger than 3, only the first 3 elements will |
| * be used; if smaller, the remaining elements will be automatically set. |
| */ |
| public DotyHumphreySmallFastCounting64(long[] seed) { |
| if (seed.length < SEED_SIZE) { |
| final long[] state = new long[SEED_SIZE]; |
| fillState(state, seed); |
| setSeedInternal(state); |
| } else { |
| setSeedInternal(seed); |
| } |
| } |
| |
| /** |
| * Seeds the RNG. |
| * |
| * @param seed Seed. |
| */ |
| private void setSeedInternal(long[] seed) { |
| a = seed[0]; |
| b = seed[1]; |
| c = seed[2]; |
| counter = 1L; |
| for (int i = 0; i < 18; i++) { |
| next(); |
| } |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public final long next() { |
| final long tmp = a + b + counter++; |
| a = b ^ (b >>> 11); |
| b = c + (c << 3); |
| c = Long.rotateLeft(c, 24) + tmp; |
| return tmp; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected byte[] getStateInternal() { |
| return composeStateInternal(NumberFactory.makeByteArray(new long[] {a, b, c, counter}), |
| super.getStateInternal()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected void setStateInternal(byte[] s) { |
| final byte[][] parts = splitStateInternal(s, 4 * 8); |
| |
| final long[] tmp = NumberFactory.makeLongArray(parts[0]); |
| a = tmp[0]; |
| b = tmp[1]; |
| c = tmp[2]; |
| counter = tmp[3]; |
| |
| super.setStateInternal(parts[1]); |
| } |
| } |