content: /*
   * Copyright (C) 2011 Clearspring Technologies, 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.clearspring.analytics.stream.cardinality;
  
  import java.io.IOException;
  
  import java.util.Arrays;
  
  import com.google.common.base.Charsets;
  import com.google.common.hash.HashFunction;
  import com.google.common.hash.Hashing;
  
  import org.junit.Ignore;
  import org.junit.Test;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  public class TestLogLog {
  
      @Test
      public void testSerialization() throws IOException {
          LogLog hll = new LogLog(8);
          hll.offer("a");
          hll.offer("b");
          hll.offer("c");
          hll.offer("d");
          hll.offer("e");
  
          LogLog hll2 = new LogLog(hll.getBytes());
          assertEquals(hll.cardinality(), hll2.cardinality());
      }
  
      @Test
      public void testHighCardinality() {
          long start = System.currentTimeMillis();
          LogLog loglog = new LogLog(10);
          int size = 10000000;
          for (int i = 0; i < size; i++) {
              loglog.offer(TestICardinality.streamElement(i));
          }
          System.out.println("time: " + (System.currentTimeMillis() - start));
          long estimate = loglog.cardinality();
          double err = Math.abs(estimate - size) / (double) size;
          System.out.println(err);
          assertTrue(err < .11);
      }
  
      @Test
      public void testHighCardinalityHighOrder() {
          long start = System.currentTimeMillis();
          LogLog loglog = new LogLog(25);
          int size = 100000000;
          for (int i = 0; i < size; i++) {
              loglog.offer(TestICardinality.streamElement(i));
          }
          System.out.println("time: " + (System.currentTimeMillis() - start));
          long estimate = loglog.cardinality();
          double err = Math.abs(estimate - size) / (double) size;
          System.out.println(size);
          System.out.println(estimate);
          System.out.println(err);
          assertTrue(err < .06);
      }
  
      @Test
      public void testMerge() throws CardinalityMergeException {
          int numToMerge = 5;
          int bits = 16;
          int cardinality = 1000000;
  
          LogLog[] loglogs = new LogLog[numToMerge];
          LogLog baseline = new LogLog(bits);
          for (int i = 0; i < numToMerge; i++) {
              loglogs[i] = new LogLog(bits);
              for (int j = 0; j < cardinality; j++) {
                  double val = Math.random();
                  loglogs[i].offer(val);
                  baseline.offer(val);
              }
          }
  
  
          LogLog hll = loglogs[0];
          loglogs = Arrays.asList(loglogs).subList(1, loglogs.length).toArray(new LogLog[0]);
          long mergedEstimate = hll.merge(loglogs).cardinality();
          long baselineEstimate = baseline.cardinality();
  
          System.out.println("Baseline estimate: " + baselineEstimate);
  
          assertEquals(mergedEstimate, baselineEstimate);
      }
  
      @Test
      @Ignore
      public void testPrecise() throws CardinalityMergeException {
          int cardinality = 1000000000;
          int b = 12;
          LogLog baseline = new LogLog(b);
          LogLog guava128 = new LogLog(b);
          HashFunction hf128 = Hashing.murmur3_128();
          for (int j = 0; j < cardinality; j++) {
              Double val = Math.random();
              String valString = val.toString();
              baseline.offer(valString);
              guava128.offerHashed(hf128.hashString(valString, Charsets.UTF_8).asLong());
              if (j > 0 && j % 1000000 == 0) {
                  System.out.println("current count: " + j);
              }
          }
  
  
          long baselineEstimate = baseline.cardinality();
          long g128Estimate = guava128.cardinality();
          double se = cardinality * (1.04 / Math.sqrt(Math.pow(2, b)));
          double baselineError = (baselineEstimate - cardinality) / (double) cardinality;
          double g128Error = (g128Estimate - cardinality) / (double) cardinality;
          System.out.format("b: %f g128 %f", baselineError, g128Error);
          assertTrue("baseline estimate bigger than expected", baselineEstimate >= cardinality - (2 * se));
          assertTrue("baseline estimate smaller than expected", baselineEstimate <= cardinality + (2 * se));
          assertTrue("g128 estimate bigger than expected", g128Estimate >= cardinality - (2 * se));
          assertTrue("g128 estimate smaller than expected", g128Estimate <= cardinality + (2 * se));
      }
  }
  