TestHistogram.java

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 * 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
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 */
package org.apache.avro.ipc.stats;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.TreeSet;

import org.apache.avro.ipc.stats.Histogram.Entry;
import org.apache.avro.ipc.stats.Histogram.Segmenter;
import org.junit.Test;

public class TestHistogram {

  @Test
  public void testBasicOperation() {
    Segmenter<String, Integer> s = new Histogram.TreeMapSegmenter<Integer>(
        new TreeSet<Integer>(Arrays.asList(0, 1, 2, 4, 8, 16)));

    Histogram<String, Integer> h = new Histogram<String, Integer>(s);

    for(int i = 0; i < 20; ++i) {
      h.add(i);
    }
    assertEquals(20, h.getCount());
    assertArrayEquals(new int[] { 1, 1, 2, 4, 8, 4 }, h.getHistogram());

    assertEquals("[0,1)=1;[1,2)=1;[2,4)=2;[4,8)=4;[8,16)=8;[16,infinity)=4", h.toString());

    String[] correctBucketLabels = {
        "[0,1)", "[1,2)", "[2,4)", "[4,8)", "[8,16)", "[16,infinity)"};

    // test bucket iterator
    int pos = 0;
    Iterator<String> it = h.getSegmenter().getBuckets();
    while (it.hasNext()) {
      assertEquals(correctBucketLabels[pos], it.next());
      pos = pos + 1;
    }
    assertEquals(correctBucketLabels.length, pos);

    List<String> labels = h.getSegmenter().getBucketLabels();
    assertEquals(correctBucketLabels.length, labels.size());
    if (labels.size() == correctBucketLabels.length) {
      for (int i = 0; i < labels.size(); i++) {
        assertEquals(correctBucketLabels[i], labels.get(i));
      }
    }

    String[] correctBoundryLabels = {
        "0", "1", "2", "4", "8", "16"};
    List<String> boundryLabels = h.getSegmenter().getBoundaryLabels();

    assertEquals(correctBoundryLabels.length, boundryLabels.size());
    if (boundryLabels.size() == correctBoundryLabels.length) {
      for (int i = 0; i < boundryLabels.size(); i++) {
        assertEquals(correctBoundryLabels[i], boundryLabels.get(i));
      }
    }

    List<Entry<String>> entries = new ArrayList<Entry<String>>();
    for (Entry<String> entry : h.entries()) {
      entries.add(entry);
    }
    assertEquals("[0,1)", entries.get(0).bucket);
    assertEquals(4, entries.get(5).count);
    assertEquals(6, entries.size());

    h.add(1010);
    h.add(9191);
    List<Integer> recent = h.getRecentAdditions();
    assertTrue(recent.contains(1010));
    assertTrue(recent.contains(9191));

  }

  @Test(expected=Histogram.SegmenterException.class)
  public void testBadValue() {
    Segmenter<String, Long> s = new Histogram.TreeMapSegmenter<Long>(
        new TreeSet<Long>(Arrays.asList(0L, 1L, 2L, 4L, 8L, 16L)));

    Histogram<String, Long> h = new Histogram<String, Long>(s);
    h.add(-1L);
  }

  /** Only has one bucket */
  static class SingleBucketSegmenter implements Segmenter<String, Float >{
    @Override
    public Iterator<String> getBuckets() {
      return Arrays.asList("X").iterator();
    }

    public List<String> getBoundaryLabels() {
      return Arrays.asList("X");
    }

    public List<String> getBucketLabels() {
      return Arrays.asList("X");
    }

    @Override
    public int segment(Float value) { return 0; }

    @Override
    public int size() { return 1; }

  }

  @Test
  public void testFloatHistogram() {
    FloatHistogram<String> h = new FloatHistogram<String>(new SingleBucketSegmenter());
    h.add(12.0f);
    h.add(10.0f);
    h.add(20.0f);

    assertEquals(3, h.getCount());
    assertEquals(14.0f, h.getMean(), 0.0001);
    assertEquals(5.291f, h.getUnbiasedStdDev(), 0.001);
  }

}