content: /*
   * 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.cassandra.utils;
  
  import java.util.concurrent.atomic.AtomicLongArray;
  
  import org.junit.Test;
  
  import static org.junit.Assert.assertArrayEquals;
  
  public class HistogramBuilderTest
  {
  
      @Test
      public void testStdevEmpty()
      {
          EstimatedHistogram hist = new HistogramBuilder().buildWithStdevRangesAroundMean();
          assertArrayEquals(new long[] { }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0 }, toArray(hist.buckets));
      }
  
      @Test
      public void testStdevSingletonRanges()
      {
          EstimatedHistogram hist;
          hist = new HistogramBuilder(new long[] { 5, 5, 5, 5, 5 }).buildWithStdevRangesAroundMean();
          assertArrayEquals(new long[] { 4, 5 }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0, 5, 0 }, toArray(hist.buckets));
          // should behave exactly the same for negative numbers
          hist = new HistogramBuilder(new long[] { -1 }).buildWithStdevRangesAroundMean();
          assertArrayEquals(new long[] { -2, -1 }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0, 1, 0 }, toArray(hist.buckets));
      }
  
      @Test
      public void testStdevNearZeroStdev()
      {
          EstimatedHistogram hist;
          long[] vals = new long[100000];
          vals[0] = 99;
          vals[1] = 101;
          for (int i = 2 ; i < vals.length ; i++)
              vals[i] = 100;
          hist = new HistogramBuilder(vals).buildWithStdevRangesAroundMean();
          assertArrayEquals(new long[] { 98, 99, 100, 101 }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0, 1, vals.length - 2, 1, 0 }, toArray(hist.buckets));
      }
  
      @Test
      public void testStdev()
      {
          long[] vals;
          EstimatedHistogram hist;
          vals = new long[] { -10, -3, -2, -2, -1, -1, -1, -1, -1, -1, -1, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 10 };
          hist = new HistogramBuilder(vals).buildWithStdevRangesAroundMean(2);
          assertArrayEquals(new long[] { -11, -6, -3, 0, 3, 6, 10 }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0, 1, 1, 10, 10, 0, 1, 0 }, toArray(hist.buckets));
      }
  
      private static long[] toArray(AtomicLongArray a)
      {
          final long[] r = new long[a.length()];
          for (int i = 0 ; i < r.length ; i++)
              r[i] = a.get(i);
          return r;
      }
  
      @Test
      public void testStdevLargeNumbers()
      {
          long[] vals;
          EstimatedHistogram hist;
          vals = new long[100000];
          for (int i = 0 ; i < vals.length ; i++)
          {
              if (i < vals.length * 0.6f)
                  vals[i] = 60;
              else if (i < vals.length * 0.8f)
                  vals[i] = 120;
              else if (i < vals.length * 0.9f)
                  vals[i] = 180;
              else if (i < vals.length * 0.95f)
                  vals[i] = 240;
              else if (i < vals.length * 0.98f)
                  vals[i] = 320;
              else
                  vals[i] = 1000;
          }
          hist = new HistogramBuilder(vals).buildWithStdevRangesAroundMean(2);
          assertArrayEquals(new long[] { 59, 120, 260, 400, 1000 }, hist.getBucketOffsets());
          assertArrayEquals(new long[] { 0, 80000, 15000, 3000, 2000, 0 }, toArray(hist.buckets));
      }
  
  }
  