code: /*
   * Copyright (c) 2016-present, RxJava Contributors.
   *
   * 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 io.reactivex.rxjava3.core;
  
  import java.util.*;
  import java.util.concurrent.TimeUnit;
  
  import org.openjdk.jmh.annotations.*;
  import org.openjdk.jmh.infra.Blackhole;
  
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  
  @BenchmarkMode(Mode.Throughput)
  @OutputTimeUnit(TimeUnit.SECONDS)
  public class OperatorMergePerf {
  
      // flatMap
      @Benchmark
      public void oneStreamOfNthatMergesIn1(final InputMillion input) throws InterruptedException {
          Flowable<Flowable<Integer>> os = Flowable.range(1, input.size)
                  .map(new Function<Integer, Flowable<Integer>>() {
                      @Override
                      public Flowable<Integer> apply(Integer v) {
                          return Flowable.just(v);
                      }
                  });
          PerfSubscriber o = input.newLatchedObserver();
          Flowable.merge(os).subscribe(o);
  
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      // flatMap
      @Benchmark
      public void merge1SyncStreamOfN(final InputMillion input) throws InterruptedException {
          Flowable<Flowable<Integer>> os = Flowable.just(1).map(new Function<Integer, Flowable<Integer>>() {
              @Override
              public Flowable<Integer> apply(Integer i) {
                      return Flowable.range(0, input.size);
              }
          });
          PerfSubscriber o = input.newLatchedObserver();
          Flowable.merge(os).subscribe(o);
  
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      @Benchmark
      public void mergeNSyncStreamsOfN(final InputThousand input) throws InterruptedException {
          Flowable<Flowable<Integer>> os = input.flowable.map(new Function<Integer, Flowable<Integer>>() {
              @Override
              public Flowable<Integer> apply(Integer i) {
                      return Flowable.range(0, input.size);
              }
          });
          PerfSubscriber o = input.newLatchedObserver();
          Flowable.merge(os).subscribe(o);
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      @Benchmark
      public void mergeNAsyncStreamsOfN(final InputThousand input) throws InterruptedException {
          Flowable<Flowable<Integer>> os = input.flowable.map(new Function<Integer, Flowable<Integer>>() {
              @Override
              public Flowable<Integer> apply(Integer i) {
                      return Flowable.range(0, input.size).subscribeOn(Schedulers.computation());
              }
          });
          PerfSubscriber o = input.newLatchedObserver();
          Flowable.merge(os).subscribe(o);
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      @Benchmark
      public void mergeTwoAsyncStreamsOfN(final InputThousand input) throws InterruptedException {
          PerfSubscriber o = input.newLatchedObserver();
          Flowable<Integer> ob = Flowable.range(0, input.size).subscribeOn(Schedulers.computation());
          Flowable.merge(ob, ob).subscribe(o);
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      @Benchmark
      public void mergeNSyncStreamsOf1(final InputForMergeN input) throws InterruptedException {
          PerfSubscriber o = input.newLatchedObserver();
          Flowable.merge(input.observables).subscribe(o);
          if (input.size == 1) {
              while (o.latch.getCount() != 0) { }
          } else {
              o.latch.await();
          }
      }
  
      @State(Scope.Thread)
      public static class InputForMergeN {
          @Param({ "1", "100", "1000" })
          //        @Param({ "1000" })
          public int size;
  
          private Blackhole bh;
          List<Flowable<Integer>> observables;
  
          @Setup
          public void setup(final Blackhole bh) {
              this.bh = bh;
              observables = new ArrayList<>();
              for (int i = 0; i < size; i++) {
                  observables.add(Flowable.just(i));
              }
          }
  
          public PerfSubscriber newLatchedObserver() {
              return new PerfSubscriber(bh);
          }
      }
  
      @State(Scope.Thread)
      public static class InputMillion extends InputWithIncrementingInteger {
  
          @Param({ "1", "1000", "1000000" })
          //        @Param({ "1000" })
          public int size;
  
          @Override
          public int getSize() {
              return size;
          }
  
      }
  
      @State(Scope.Thread)
      public static class InputThousand extends InputWithIncrementingInteger {
  
          @Param({ "1", "1000" })
          //        @Param({ "1000" })
          public int size;
  
          @Override
          public int getSize() {
              return size;
          }
  
      }
  }
  