how to implement multiple subscribers simply

edit

I am studying ROS2 dashing. I 'd like to create many simple subscribers which subscribe same topic and test CPU performance. Now I am trying as follws. This is a example which two subscribers run. I'd like to test a case in which ,for example, 100 subscribers are running. Is there any better way to realize multiple such ? Thanks.

//subnodes.hpp
#include <rclcpp/rclcpp.hpp>
#include <std_msgs/msg/int16.hpp>

class MinimalSubscriber1:public rclcpp::Node{
private:
    rclcpp::Subscription<std_msgs::msg::Int16>::SharedPtr subscription_;
    void topic_callback_(const std_msgs::msg::Int16::SharedPtr msg);
public:
    MinimalSubscriber1();
};

class MinimalSubscriber2:public rclcpp::Node{
private:
    rclcpp::Subscription<std_msgs::msg::Int16>::SharedPtr subscription_;
    void topic_callback_(const std_msgs::msg::Int16::SharedPtr msg);
public:
    MinimalSubscriber2();
};

//subnodes.cpp
#include <rclcpp/rclcpp.hpp>
#include <std_msgs/msg/int16.hpp>
#include "subnodes.hpp"

void MinimalSubscriber1::topic_callback_(const std_msgs::msg::Int16::SharedPtr msg){
    RCLCPP_INFO(this->get_logger(), "No.1 heard:%d",msg->data);
}
 MinimalSubscriber1::MinimalSubscriber1()
:Node("minimal_subscriber_test1"){
    subscription_ = this->create_subscription<std_msgs::msg::Int16>(
        "testtopic",
        std::bind(&MinimalSubscriber1::topic_callback_,this,std::placeholders::_1)
    );
}

void MinimalSubscriber2::topic_callback_(const std_msgs::msg::Int16::SharedPtr msg){
    RCLCPP_INFO(this->get_logger(), "No.2 heard:%d",msg->data);
}
 MinimalSubscriber2::MinimalSubscriber2()
:Node("minimal_subscriber_test2"){
    subscription_ = this->create_subscription<std_msgs::msg::Int16>(
        "testtopic",
        std::bind(&MinimalSubscriber2::topic_callback_,this,std::placeholders::_1)
    );
}

//main.cpp
#include <rclcpp/rclcpp.hpp>
#include "subnodes.hpp"

int main(int argc,char*argv[]){
  rclcpp::init(argc,argv);
  rclcpp::executors::SingleThreadedExecutor exec;

  auto node1 = std::make_shared<MinimalSubscriber1>();
  auto node2 = std::make_shared<MinimalSubscriber2>();
  exec.add_node(node1);
  exec.add_node(node2);
  exec::spin();
  rclcpp::shutdown();
  return 0;
}