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/*
* Copyright 2009 Phil Burk, Mobileer Inc
*
* 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.
*/
/**
* Sep 9, 2009
* com.jsyn.engine.units.SynthRandom.java
*/
package com.jsyn.util;
import java.util.Random;
/**
* Pseudo-random numbers using predictable and fast linear-congruential method.
*
* @author Phil Burk (C) 2009 Mobileer Inc Translated from 'C' to Java by Lisa
* Tolentino.
*/
public class PseudoRandom {
// We must shift 1L or else we get a negative number!
private static final double INT_TO_DOUBLE = (1.0 / (1L << 31));
private long seed = 99887766;
/**
* Create an instance of SynthRandom.
*/
public PseudoRandom() {
this(new Random().nextInt());
}
/**
* Create an instance of PseudoRandom.
*/
public PseudoRandom(int seed) {
setSeed(seed);
}
public void setSeed(int seed) {
this.seed = (long) seed;
}
public int getSeed() {
return (int) seed;
}
/**
* Returns the next random double from 0.0 to 1.0
*
* @return value from 0.0 to 1.0
*/
public double random() {
int positiveInt = nextRandomInteger() & 0x7FFFFFFF;
return positiveInt * INT_TO_DOUBLE;
}
/**
* Returns the next random double from -1.0 to 1.0
*
* @return value from -1.0 to 1.0
*/
public double nextRandomDouble() {
return nextRandomInteger() * INT_TO_DOUBLE;
}
/** Calculate random 32 bit number using linear-congruential method. */
public int nextRandomInteger() {
// Use values for 64-bit sequence from MMIX by Donald Knuth.
seed = (seed * 6364136223846793005L) + 1442695040888963407L;
return (int) (seed >> 32); // The higher bits have a longer sequence.
}
public int choose(int range) {
long positiveInt = nextRandomInteger() & 0x7FFFFFFF;
long temp = positiveInt * range;
return (int) (temp >> 31);
}
}
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