/*
    * 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.commons.rng.examples.jmh.simple;
  
  import org.openjdk.jmh.annotations.Benchmark;
  import org.openjdk.jmh.annotations.BenchmarkMode;
  import org.openjdk.jmh.annotations.Mode;
  import org.openjdk.jmh.annotations.Warmup;
  import org.openjdk.jmh.annotations.Measurement;
  import org.openjdk.jmh.annotations.State;
  import org.openjdk.jmh.annotations.Threads;
  import org.openjdk.jmh.annotations.Fork;
  import org.openjdk.jmh.annotations.Scope;
  import org.openjdk.jmh.annotations.Param;
  import org.openjdk.jmh.annotations.Setup;
  import org.openjdk.jmh.annotations.OutputTimeUnit;
  
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.concurrent.TimeUnit;
  
  import org.apache.commons.rng.UniformRandomProvider;
  import org.apache.commons.rng.simple.RandomSource;
  import org.apache.commons.rng.simple.ThreadLocalRandomSource;
  
  /**
   * Executes benchmark to compare the speed of generation of low frequency
   * random numbers on multiple-threads.
   */
  @BenchmarkMode(Mode.AverageTime)
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  @Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
  @Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)
  @State(Scope.Benchmark)
  @Fork(value = 1, jvmArgs = {"-server", "-Xms128M", "-Xmx128M"})
  public class ThreadLocalPerformance {
      /**
       * Number of random values to generate.
       */
      @Param({"0", "1", "10", "100"})
      private int numValues;
  
      /**
       * The benchmark state (to retrieve the various "RandomSource"s).
       */
      @State(Scope.Benchmark)
      public static class Sources {
          /** The random source. */
          protected RandomSource randomSource;
  
          /**
           * RNG providers.
           */
          @Param({"SPLIT_MIX_64"})
          private String randomSourceName;
  
          /**
           * @return the random source
           */
          public RandomSource getRandomSource() {
              return randomSource;
          }
  
          /** Instantiates the random source. */
          @Setup
          public void setup() {
              randomSource = RandomSource.valueOf(randomSourceName);
          }
      }
  
      /**
       * The benchmark state (to retrieve the various "RandomSource"s thread locally).
       */
      @State(Scope.Benchmark)
      public static class LocalSources extends Sources {
          /** The thread-local random provider. */
          private ThreadLocal<UniformRandomProvider> rng;
  
          /**
           * @return the random number generator
           */
          public UniformRandomProvider getRNG() {
              return rng.get();
          }
  
         /** Instantiates the ThreadLocal holding the random source. */
         @Override
         @Setup
         public void setup() {
             super.setup();
 
             rng = new ThreadLocal<UniformRandomProvider>() {
                 @Override
                 protected UniformRandomProvider initialValue() {
                     return randomSource.create();
                 }
             };
         }
     }
 
     /**
      * @return the result
      */
     @Benchmark
     @Threads(4)
     public long threadLocalRandom() {
         final ThreadLocalRandom rng = ThreadLocalRandom.current();
         long result = 0;
         for (int i = 0; i < numValues; i++) {
             result = result ^ rng.nextLong();
         }
         return result;
     }
 
     /**
      * @return the result
      */
     @Benchmark
     @Threads(4)
     public long threadLocalRandomWrapped() {
         final ThreadLocalRandom rand = ThreadLocalRandom.current();
         final UniformRandomProvider rng = rand::nextLong;
         long result = 0;
         for (int i = 0; i < numValues; i++) {
             result = result ^ rng.nextLong();
         }
         return result;
     }
 
     /**
      * @param sources Source of randomness.
      * @return the result
      */
     @Benchmark
     @Threads(4)
     public long randomSourceCreate(Sources sources) {
         final UniformRandomProvider rng = sources.getRandomSource().create();
         long result = 0;
         for (int i = 0; i < numValues; i++) {
             result = result ^ rng.nextLong();
         }
         return result;
     }
 
     /**
      * @param sources Source of randomness.
      * @return the result
      */
     @Benchmark
     @Threads(4)
     public long threadLocalRandomSourceCurrent(Sources sources) {
         final UniformRandomProvider rng = ThreadLocalRandomSource.current(sources.getRandomSource());
         long result = 0;
         for (int i = 0; i < numValues; i++) {
             result = result ^ rng.nextLong();
         }
         return result;
     }
 
     /**
      * @param localSources Local source of randomness.
      * @return the result
      */
     @Benchmark
     @Threads(4)
     public long threadLocalUniformRandomProvider(LocalSources localSources) {
         final UniformRandomProvider rng = localSources.getRNG();
         long result = 0;
         for (int i = 0; i < numValues; i++) {
             result = result ^ rng.nextLong();
         }
         return result;
     }
 }