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 com.alibaba.metrics;
  
  import org.junit.Test;
  
  import java.util.concurrent.TimeUnit;
  
  import static org.assertj.core.api.Assertions.assertThat;
  import static org.assertj.core.api.Assertions.offset;
  
  public class EWMATest {
      @Test
      public void aOneMinuteEWMAWithAValueOfThree() throws Exception {
          final EWMA ewma = EWMA.oneMinuteEWMA();
          ewma.update(3);
          ewma.tick();
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.6, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.22072766, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.08120117, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.02987224, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.01098938, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00404277, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00148725, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00054713, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00020128, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00007405, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00002724, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00001002, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00000369, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00000136, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00000050, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.00000018, offset(0.000001));
      }
  
      @Test
      public void aFiveMinuteEWMAWithAValueOfThree() throws Exception {
          final EWMA ewma = EWMA.fiveMinuteEWMA();
          ewma.update(3);
          ewma.tick();
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.6, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.49123845, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.40219203, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.32928698, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.26959738, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.22072766, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.18071653, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.14795818, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.12113791, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.09917933, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.08120117, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.06648190, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.05443077, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.04456415, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.03648604, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.02987224, offset(0.000001));
      }
  
      @Test
      public void aFifteenMinuteEWMAWithAValueOfThree() throws Exception {
          final EWMA ewma = EWMA.fifteenMinuteEWMA();
          ewma.update(3);
          ewma.tick();
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.6, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.56130419, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.52510399, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.49123845, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.45955700, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.42991879, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.40219203, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.37625345, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.35198773, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.32928698, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.30805027, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.28818318, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.26959738, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.25221023, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.23594443, offset(0.000001));
  
          elapseMinute(ewma);
  
          assertThat(ewma.getRate(TimeUnit.SECONDS)).isEqualTo(0.22072766, offset(0.000001));
      }
  
  
      private void elapseMinute(EWMA ewma) {
          for (int i = 1; i <= 12; i++) {
              ewma.tick();
          }
      }
  }
  