/**
* 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.mahout.cf.taste.impl.common;
import org.apache.mahout.cf.taste.impl.TasteTestCase;
import org.junit.Test;
public final class SamplingLongPrimitiveIteratorTest extends TasteTestCase {
@Test
public void testEmptyCase() {
assertFalse(new SamplingLongPrimitiveIterator(
countingIterator(0), 0.9999).hasNext());
assertFalse(new SamplingLongPrimitiveIterator(
countingIterator(0), 1).hasNext());
}
@Test
public void testSmallInput() {
SamplingLongPrimitiveIterator t = new SamplingLongPrimitiveIterator(
countingIterator(1), 0.9999);
assertTrue(t.hasNext());
assertEquals(0L, t.nextLong());
assertFalse(t.hasNext());
}
@Test(expected = IllegalArgumentException.class)
public void testBadRate1() {
new SamplingLongPrimitiveIterator(countingIterator(1), 0.0);
}
@Test(expected = IllegalArgumentException.class)
public void testBadRate2() {
new SamplingLongPrimitiveIterator(countingIterator(1), 1.1);
}
@Test
public void testExactSizeMatch() {
SamplingLongPrimitiveIterator t = new SamplingLongPrimitiveIterator(
countingIterator(10), 1);
for (int i = 0; i < 10; i++) {
assertTrue(t.hasNext());
assertEquals(i, t.next().intValue());
}
assertFalse(t.hasNext());
}
@Test
public void testSample() {
double p = 0.1;
int n = 1000;
double sd = Math.sqrt(n * p * (1.0 - p));
for (int i = 0; i < 1000; i++) {
SamplingLongPrimitiveIterator t = new SamplingLongPrimitiveIterator(countingIterator(n), p);
int k = 0;
while (t.hasNext()) {
long v = t.nextLong();
k++;
assertTrue(v >= 0L);
assertTrue(v < 1000L);
}
// Should be +/- 5 standard deviations except in about 1 out of 1.7M cases
assertTrue(k >= 100 - 5 * sd);
assertTrue(k <= 100 + 5 * sd);
}
}
private static LongPrimitiveArrayIterator countingIterator(int to) {
long[] data = new long[to];
for (int i = 0; i < to; i++) {
data[i] = i;
}
return new LongPrimitiveArrayIterator(data);
}
}