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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.
*/
package com.jsyn.util;
import junit.framework.TestCase;
public class TestPseudoRandom extends TestCase {
PseudoRandom pseudoRandom;
private int[] bins;
private final static int BIN_SHIFTER = 8;
private final static int BIN_COUNT = 1 << BIN_SHIFTER;
private final static int BIN_MASK = BIN_COUNT - 1;
@Override
protected void setUp() throws Exception {
super.setUp();
pseudoRandom = new PseudoRandom();
bins = new int[BIN_COUNT];
}
@Override
protected void tearDown() throws Exception {
super.tearDown();
}
public void testMath() {
long seed = 3964771111L;
int positiveInt = (int) (seed & 0x7FFFFFFF);
assertTrue("masked random positive, " + positiveInt, (positiveInt >= 0));
double rand = positiveInt * (1.0 / (1L << 31));
assertTrue("not too low, " + rand, (rand >= 0.0));
assertTrue("not too high, " + rand, (rand < 1.0));
}
public void testIntegerDistribution() {
int scaler = 100;
for (int i = 0; i < (bins.length * scaler); i++) {
int rand = pseudoRandom.nextRandomInteger();
int positiveInt = rand & 0x7FFFFFFF;
assertTrue("masked random " + positiveInt, (positiveInt >= 0));
int index = (rand >> (32 - BIN_SHIFTER)) & BIN_MASK;
bins[index] += 1;
}
checkDistribution(scaler);
}
public void test01Distribution() {
int scaler = 100;
for (int i = 0; i < (bins.length * scaler); i++) {
double rand = pseudoRandom.random();
assertTrue("not too low, #" + i + " = " + rand, (rand >= 0.0));
assertTrue("not too high, #" + i + " = " + rand, (rand < 1.0));
int index = (int) (rand * BIN_COUNT);
bins[index] += 1;
}
checkDistribution(scaler);
}
private void checkDistribution(int scaler) {
// Generate running average that should stay near scaler
double average = scaler;
double coefficient = 0.9;
for (int i = 0; i < (bins.length); i++) {
average = (average * coefficient) + (bins[i] * (1.0 - coefficient));
assertEquals("average at " + i, scaler, average, 0.2 * scaler);
}
}
}
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