org.apache.commons.rng.simple.internal.Long2IntArray Maven / Gradle / Ivy
/*
* 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.simple.internal;
import org.apache.commons.rng.core.source64.SplitMix64;
import org.apache.commons.rng.core.util.NumberFactory;
/**
* Uses a {@code long} value to seed a {@link SplitMix64} RNG and
* create a {@code int[]} with the requested number of random
* values.
*
* @since 1.0
*/
public class Long2IntArray implements Seed2ArrayConverter {
/** Size of the output array. */
private final int size;
/**
* @param size Size of the output array.
*/
public Long2IntArray(int size) {
this.size = size;
}
/** {@inheritDoc} */
@Override
public int[] convert(Long seed) {
return convertSeed(seed, size);
}
/**
* {@inheritDoc}
*
* @since 1.3
*/
@Override
public int[] convert(Long seed, int outputSize) {
return convertSeed(seed, outputSize);
}
/**
* Convert the seed.
*
* @param seed Input seed.
* @param size Output array size.
* @return the converted seed.
*/
private static int[] convertSeed(Long seed, int size) {
final int[] out = new int[size];
final SplitMix64 rng = new SplitMix64(seed);
// Fill pairs of ints from a long.
// The array is filled from the end towards the start.
for (int i = size - 1; i > 0; i -= 2) {
final long v = rng.nextLong();
out[i] = NumberFactory.extractHi(v);
out[i - 1] = NumberFactory.extractLo(v);
}
// An odd size requires a final single int at the start
if ((size & 1) == 1) {
out[0] = NumberFactory.extractHi(rng.nextLong());
}
return out;
}
}