| /* |
| * 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.JumpableUniformRandomProvider; |
| import org.apache.commons.rng.UniformRandomProvider; |
| import org.apache.commons.rng.core.util.NumberFactory; |
| |
| /** |
| * A 64-bit all purpose generator. |
| * |
| * <p>This is a member of the LXM family of generators: L=Linear congruential generator; |
| * X=Xor based generator; and M=Mix. This member uses a 128-bit LCG and 256-bit Xor-based |
| * generator. It is named as {@code "L128X256MixRandom"} in the {@code java.util.random} |
| * package introduced in JDK 17; the LXM family is described in further detail in: |
| * |
| * <blockquote>Steele and Vigna (2021) LXM: better splittable pseudorandom number generators |
| * (and almost as fast). Proceedings of the ACM on Programming Languages, Volume 5, |
| * Article 148, pp 1–31.</blockquote> |
| * |
| * <p>Memory footprint is 512 bits and the period is 2<sup>128</sup> (2<sup>256</sup> - 1). |
| * |
| * <p>This generator implements |
| * {@link org.apache.commons.rng.LongJumpableUniformRandomProvider LongJumpableUniformRandomProvider}. |
| * In addition instances created with a different additive parameter for the LCG are robust |
| * against accidental correlation in a multi-threaded setting. The additive parameters must be |
| * different in the most significant 127-bits. |
| * |
| * @see <a href="https://doi.org/10.1145/3485525">Steele & Vigna (2021) Proc. ACM Programming |
| * Languages 5, 1-31</a> |
| * @see <a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/random/package-summary.html"> |
| * JDK 17 java.util.random javadoc</a> |
| * @since 1.5 |
| */ |
| public class L128X256Mix extends AbstractL128 { |
| /** Size of the seed vector. */ |
| private static final int SEED_SIZE = 8; |
| /** Size of the XBG state vector. */ |
| private static final int XBG_STATE_SIZE = 4; |
| /** Low half of 128-bit LCG multiplier. */ |
| private static final long ML = LXMSupport.M128L; |
| |
| /** State 0 of the XBG. */ |
| private long x0; |
| /** State 1 of the XBG. */ |
| private long x1; |
| /** State 2 of the XBG. */ |
| private long x2; |
| /** State 3 of the XBG. */ |
| private long x3; |
| |
| /** |
| * Creates a new instance. |
| * |
| * @param seed Initial seed. |
| * If the length is larger than 8, only the first 8 elements will |
| * be used; if smaller, the remaining elements will be automatically |
| * set. A seed containing all zeros in the last four elements |
| * will create a non-functional XBG sub-generator and a low |
| * quality output with a period of 2<sup>128</sup>. |
| * |
| * <p>The 1st and 2nd elements are used to set the LCG increment; the least significant bit |
| * is set to odd to ensure a full period LCG. The 3rd and 4th elements are used |
| * to set the LCG state.</p> |
| */ |
| public L128X256Mix(long[] seed) { |
| super(seed = extendSeed(seed, SEED_SIZE)); |
| x0 = seed[4]; |
| x1 = seed[5]; |
| x2 = seed[6]; |
| x3 = seed[7]; |
| } |
| |
| /** |
| * Creates a new instance using an 8 element seed. |
| * A seed containing all zeros in the last four elements |
| * will create a non-functional XBG sub-generator and a low |
| * quality output with a period of 2<sup>128</sup>. |
| * |
| * <p>The 1st and 2nd elements are used to set the LCG increment; the least significant bit |
| * is set to odd to ensure a full period LCG. The 3rd and 4th elements are used |
| * to set the LCG state.</p> |
| * |
| * @param seed0 Initial seed element 0. |
| * @param seed1 Initial seed element 1. |
| * @param seed2 Initial seed element 2. |
| * @param seed3 Initial seed element 3. |
| * @param seed4 Initial seed element 4. |
| * @param seed5 Initial seed element 5. |
| * @param seed6 Initial seed element 6. |
| * @param seed7 Initial seed element 7. |
| */ |
| public L128X256Mix(long seed0, long seed1, long seed2, long seed3, |
| long seed4, long seed5, long seed6, long seed7) { |
| super(seed0, seed1, seed2, seed3); |
| x0 = seed4; |
| x1 = seed5; |
| x2 = seed6; |
| x3 = seed7; |
| } |
| |
| /** |
| * Creates a copy instance. |
| * |
| * @param source Source to copy. |
| */ |
| protected L128X256Mix(L128X256Mix source) { |
| super(source); |
| x0 = source.x0; |
| x1 = source.x1; |
| x2 = source.x2; |
| x3 = source.x3; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected byte[] getStateInternal() { |
| return composeStateInternal(NumberFactory.makeByteArray( |
| new long[] {x0, x1, x2, x3}), |
| super.getStateInternal()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected void setStateInternal(byte[] s) { |
| final byte[][] c = splitStateInternal(s, XBG_STATE_SIZE * Long.BYTES); |
| final long[] tmp = NumberFactory.makeLongArray(c[0]); |
| x0 = tmp[0]; |
| x1 = tmp[1]; |
| x2 = tmp[2]; |
| x3 = tmp[3]; |
| super.setStateInternal(c[1]); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public long next() { |
| // LXM generate. |
| // Old state is used for the output allowing parallel pipelining |
| // on processors that support multiple concurrent instructions. |
| |
| long s0 = x0; |
| final long sh = lsh; |
| |
| // Mix |
| final long z = LXMSupport.lea64(sh + s0); |
| |
| // LCG update |
| // The LCG is, in effect, "s = m * s + a" where m = ((1LL << 64) + ML) |
| final long sl = lsl; |
| final long al = lal; |
| final long u = ML * sl; |
| // High half |
| lsh = ML * sh + LXMSupport.unsignedMultiplyHigh(ML, sl) + sl + lah + |
| // Carry propagation |
| LXMSupport.unsignedAddHigh(u, al); |
| // Low half |
| lsl = u + al; |
| |
| // XBG update |
| long s1 = x1; |
| long s2 = x2; |
| long s3 = x3; |
| |
| final long t = s1 << 17; |
| |
| s2 ^= s0; |
| s3 ^= s1; |
| s1 ^= s2; |
| s0 ^= s3; |
| |
| s2 ^= t; |
| |
| s3 = Long.rotateLeft(s3, 45); |
| |
| x0 = s0; |
| x1 = s1; |
| x2 = s2; |
| x3 = s3; |
| |
| return z; |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>The jump size is the equivalent of moving the state <em>backwards</em> by |
| * (2<sup>256</sup> - 1) positions. It can provide up to 2<sup>128</sup> |
| * non-overlapping subsequences. |
| */ |
| @Override |
| public UniformRandomProvider jump() { |
| return super.jump(); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>The jump size is the equivalent of moving the state <em>backwards</em> by |
| * 2<sup>64</sup> (2<sup>256</sup> - 1) positions. It can provide up to |
| * 2<sup>64</sup> non-overlapping subsequences of length 2<sup>64</sup> |
| * (2<sup>256</sup> - 1); each subsequence can provide up to 2<sup>64</sup> |
| * non-overlapping subsequences of length (2<sup>256</sup> - 1) using the |
| * {@link #jump()} method. |
| */ |
| @Override |
| public JumpableUniformRandomProvider longJump() { |
| return super.longJump(); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| AbstractL128 copy() { |
| // This exists to ensure the jump function performed in the super class returns |
| // the correct class type. It should not be public. |
| return new L128X256Mix(this); |
| } |
| } |