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.index.sai.utils;
  
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicReference;
  
  /**
   * AtomicRatio provides thread safe operations to maintain a {@link Ratio} of a numerator and denominator.
   * The ratio can be updated atomically by multiple threads calling the {@link #update(long, long)} method.
   * The current ratio value can be retrieved via the {@link #get} method.
   * <p>
   * The class also provides a thread safe {@link #updateCount} that maintains the number of times the {@link Ratio}
   * has been updated. This can be used to determine whether the {@link Ratio} is useful based on the number of updates.
   */
  public class AtomicRatio
  {
      private final AtomicReference<Ratio> ratio = new AtomicReference<>(new Ratio(0, 0));
      private final AtomicInteger updateCount = new AtomicInteger();
  
      private static class Ratio
      {
          public final long numerator;
          public final long denominator;
  
          public Ratio(long numerator, long denominator)
          {
              this.numerator = numerator;
              this.denominator = denominator;
          }
      }
  
      public void update(long numerator, long denominator)
      {
          ratio.updateAndGet((current) -> new Ratio(current.numerator + numerator, current.denominator + denominator));
          updateCount.incrementAndGet();
      }
  
      public double get()
      {
          Ratio current = ratio.get();
          return (double) current.numerator / current.denominator;
      }
  
      public int getUpdateCount()
      {
          return updateCount.get();
      }
  }
  