- (IBAction)serialSync:(id)sender {
 NSLog(@"start log in main thread"]);
  dispatch_queue_t myQueue = dispatch_queue_create("myQueue", NULL);
  for (NSInteger n = 0; n < 3; n++) {
    dispatch_sync(myQueue, ^{
      for (NSInteger i = 0; i < 500000000; i++) {
        if (i == 0) {
          NSLog(@"串行同步任务%ld -> 开始%@",n,[NSThread currentThread]);
        }
        if (i == 499999999) {
          NSLog(@"串行同步任务%ld -> 完成",(long)n);
        }
      }
    });
  }
  NSLog(@"阻塞我没有？当前线程%@",[NSThread currentThread]);
}

- (IBAction)serialAsync:(id)sender {
  NSLog(@"start log in main thread"]);
  dispatch_queue_t myQueue = dispatch_queue_create("myQueue", NULL);//创建一个串行队列
  for (NSInteger n = 0; n < 3; n++) {
    dispatch_async(myQueue, ^{
      for (NSInteger i = 0; i < 500000000; i++) {
        if (i == 0) {
          NSLog(@"串行异步任务%ld -> 开始%@",n,[NSThread currentThread]);
        }
        if (i == 499999999) {
          NSLog(@"串行异步任务%ld -> 完成",(long)n);
        }
      }
    });
  }
  NSLog(@"阻塞我没有？当前线程%@",[NSThread currentThread]);
}

- (IBAction)concurrentSync:(id)sender {
  NSLog(@"start log in main thread"]);
  dispatch_queue_t myQueue = dispatch_queue_create("myQueue", DISPATCH_QUEUE_CONCURRENT);
  for (NSInteger n = 0; n < 3; n++) {
    dispatch_sync(myQueue, ^{
      for (NSInteger i = 0; i < 500000000; i++) {
        if (i == 0) {
          NSLog(@"并行同步任务%ld -> 开始%@",(long)n,[NSThread currentThread]);
        }
        if (i == 499999999) {
          NSLog(@"并行同步任务%ld -> 完成",(long)n);
        }
      }
    });
  }

  NSLog(@"阻塞我没有？当前线程%@",[NSThread currentThread]);
}
- (IBAction)concurrentAsync:(id)sender {
  NSLog(@"start log in main thread"]);
  dispatch_queue_t myQueue = dispatch_queue_create("myQueue", DISPATCH_QUEUE_CONCURRENT);
  for (NSInteger n = 0; n < 3; n++) {
    dispatch_async(myQueue, ^{
      for (NSInteger i = 0; i < 500000000; i++) {
        if (i == 0) {
          NSLog(@"并行异步任务%ld -> 开始%@",n,[NSThread currentThread]);
        }
        if (i == 499999999) {
          NSLog(@"并行异步任务%ld -> 完成",(long)n);
        }
      }
    });
  }
  NSLog(@"阻塞我没有？当前线程%@",[NSThread currentThread]);
}