AbstractXoRoShiRo1024.java
/*
* 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.JumpableUniformRandomProvider;
import org.apache.commons.rng.LongJumpableUniformRandomProvider;
import org.apache.commons.rng.UniformRandomProvider;
import org.apache.commons.rng.core.util.NumberFactory;
/**
* This abstract class is a base for algorithms from the Xor-Shift-Rotate family of 64-bit
* generators with 1024-bits of state.
*
* @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
* @since 1.3
*/
abstract class AbstractXoRoShiRo1024 extends LongProvider implements LongJumpableUniformRandomProvider {
/** Size of the state vector. */
private static final int SEED_SIZE = 16;
/** The coefficients for the jump function. */
private static final long[] JUMP_COEFFICIENTS = {
0x931197d8e3177f17L, 0xb59422e0b9138c5fL, 0xf06a6afb49d668bbL, 0xacb8a6412c8a1401L,
0x12304ec85f0b3468L, 0xb7dfe7079209891eL, 0x405b7eec77d9eb14L, 0x34ead68280c44e4aL,
0xe0e4ba3e0ac9e366L, 0x8f46eda8348905b7L, 0x328bf4dbad90d6ffL, 0xc8fd6fb31c9effc3L,
0xe899d452d4b67652L, 0x45f387286ade3205L, 0x03864f454a8920bdL, 0xa68fa28725b1b384L,
};
/** The coefficients for the long jump function. */
private static final long[] LONG_JUMP_COEFFICIENTS = {
0x7374156360bbf00fL, 0x4630c2efa3b3c1f6L, 0x6654183a892786b1L, 0x94f7bfcbfb0f1661L,
0x27d8243d3d13eb2dL, 0x9701730f3dfb300fL, 0x2f293baae6f604adL, 0xa661831cb60cd8b6L,
0x68280c77d9fe008cL, 0x50554160f5ba9459L, 0x2fc20b17ec7b2a9aL, 0x49189bbdc8ec9f8fL,
0x92a65bca41852cc1L, 0xf46820dd0509c12aL, 0x52b00c35fbf92185L, 0x1e5b3b7f589e03c1L,
};
/** 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. A seed containing all zeros will create a non-functional generator.
*/
AbstractXoRoShiRo1024(long[] seed) {
setSeedInternal(seed);
}
/**
* Creates a copy instance.
*
* @param source Source to copy.
*/
protected AbstractXoRoShiRo1024(AbstractXoRoShiRo1024 source) {
super(source);
System.arraycopy(source.state, 0, state, 0, SEED_SIZE);
index = source.index;
}
/** {@inheritDoc} */
@Override
protected byte[] getStateInternal() {
final long[] s = Arrays.copyOf(state, SEED_SIZE + 1);
s[SEED_SIZE] = index;
return composeStateInternal(NumberFactory.makeByteArray(s),
super.getStateInternal());
}
/** {@inheritDoc} */
@Override
protected void setStateInternal(byte[] s) {
final byte[][] c = splitStateInternal(s, (SEED_SIZE + 1) * 8);
final long[] tmp = NumberFactory.makeLongArray(c[0]);
System.arraycopy(tmp, 0, state, 0, SEED_SIZE);
index = (int) tmp[SEED_SIZE];
super.setStateInternal(c[1]);
}
/**
* 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 int q = index;
index = (index + 1) & 15;
final long s0 = state[index];
long s15 = state[q];
final long result = transform(s0, s15);
s15 ^= s0;
state[q] = Long.rotateLeft(s0, 25) ^ s15 ^ (s15 << 27);
state[index] = Long.rotateLeft(s15, 36);
return result;
}
/**
* Transform the two consecutive 64-bit states of the generator to a 64-bit output.
* The transformation function shall vary with respect to different generators.
*
* @param s0 The current state.
* @param s15 The previous state.
* @return the output
*/
protected abstract long transform(long s0, long s15);
/**
* {@inheritDoc}
*
* <p>The jump size is the equivalent of 2<sup>512</sup>
* calls to {@link UniformRandomProvider#nextLong() nextLong()}. It can provide
* up to 2<sup>512</sup> non-overlapping subsequences.</p>
*/
@Override
public UniformRandomProvider jump() {
final UniformRandomProvider copy = copy();
performJump(JUMP_COEFFICIENTS);
return copy;
}
/**
* {@inheritDoc}
*
*
* <p>The jump size is the equivalent of 2<sup>768</sup> calls to
* {@link UniformRandomProvider#nextLong() nextLong()}. It can provide up to
* 2<sup>256</sup> non-overlapping subsequences of length 2<sup>768</sup>; each
* subsequence can provide up to 2<sup>256</sup> non-overlapping subsequences of
* length 2<sup>512</sup> using the {@link #jump()} method.</p>
*/
@Override
public JumpableUniformRandomProvider longJump() {
final JumpableUniformRandomProvider copy = copy();
performJump(LONG_JUMP_COEFFICIENTS);
return copy;
}
/**
* Create a copy.
*
* @return the copy
*/
protected abstract AbstractXoRoShiRo1024 copy();
/**
* Perform the jump to advance the generator state. Resets the cached state of the generator.
*
* @param jumpCoefficients the jump coefficients
*/
private void performJump(long[] jumpCoefficients) {
final long[] newState = new long[SEED_SIZE];
for (final long jc : jumpCoefficients) {
for (int b = 0; b < 64; b++) {
if ((jc & (1L << b)) != 0) {
for (int i = 0; i < SEED_SIZE; i++) {
newState[i] ^= state[(i + index) & 15];
}
}
next();
}
}
// Note: Calling the next() function updates 'index'.
// The present index effectively becomes 0.
for (int j = 0; j < 16; j++) {
state[(j + index) & 15] = newState[j];
}
resetCachedState();
}
}