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Open Source Chemistry Library
/*******************************************************************************
* Copyright (c) 2010 Haifeng Li
*
* Licensed 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 smile.math;
import smile.math.random.MersenneTwister;
import smile.math.random.UniversalGenerator;
/**
* This is a high quality random number generator as a replacement of
* the standard Random class of Java system.
*
* @author Haifeng Li
*/
public class Random {
private UniversalGenerator real;
private MersenneTwister twister;
/**
* Initialize with default random number generator engine.
*/
public Random() {
real = new UniversalGenerator();
twister = new MersenneTwister();
}
/**
* Initialize with given seed for default random number generator engine.
*/
public Random(long seed) {
real = new UniversalGenerator(seed);
twister = new MersenneTwister(seed);
}
/**
* Generator a random number uniformly distributed in [0, 1).
* @return a pseudo random number
*/
public double nextDouble() {
return real.nextDouble();
}
/**
* Generate n uniform random numbers in the range [0, 1)
* @param d array of random numbers to be generated
*/
public void nextDoubles(double[] d) {
real.nextDoubles(d);
}
/**
* Generate a uniform random number in the range [lo, hi)
* @param lo lower limit of range
* @param hi upper limit of range
* @return a uniform random real in the range [lo, hi)
*/
public double nextDouble(double lo, double hi) {
return (lo + (hi - lo) * nextDouble());
}
/**
* Generate n uniform random numbers in the range [lo, hi)
* @param lo lower limit of range
* @param hi upper limit of range
* @param d array of random numbers to be generated
*/
public void nextDoubles(double[] d, double lo, double hi) {
real.nextDoubles(d);
double l = hi - lo;
int n = d.length;
for (int i = 0; i < n; i++) {
d[i] = lo + l * d[i];
}
}
/**
* Initialize the random generator with a seed.
*/
public void setSeed(long seed) {
real.setSeed(seed);
twister.setSeed(seed);
}
/**
* Returns a random integer.
*/
public int nextInt() {
return twister.nextInt();
}
/**
* Returns a random integer in [0, n).
*/
public int nextInt(int n) {
return twister.nextInt(n);
}
public long nextLong() {
return twister.nextLong();
}
/**
* Generates a permutation of 0, 1, 2, ..., n-1, which is useful for
* sampling without replacement.
*/
public int[] permutate(int n) {
int[] x = new int[n];
for (int i = 0; i < n; i++) {
x[i] = i;
}
permutate(x);
return x;
}
/**
* Generates a permutation of given array.
*/
public void permutate(int[] x) {
for (int i = 0; i < x.length; i++) {
int j = i + nextInt(x.length - i);
Math.swap(x, i, j);
}
}
/**
* Generates a permutation of given array.
*/
public void permutate(float[] x) {
for (int i = 0; i < x.length; i++) {
int j = i + nextInt(x.length - i);
Math.swap(x, i, j);
}
}
/**
* Generates a permutation of given array.
*/
public void permutate(double[] x) {
for (int i = 0; i < x.length; i++) {
int j = i + nextInt(x.length - i);
Math.swap(x, i, j);
}
}
/**
* Generates a permutation of given array.
*/
public void permutate(Object[] x) {
for (int i = 0; i < x.length; i++) {
int j = i + nextInt(x.length - i);
Math.swap(x, i, j);
}
}
}