casting.cc

#include <iostream>
#include <chrono>

class A {

 public:

  enum class Type {
    B,C,D
  };

 private:
  const Type _type;

 public:

  explicit A(Type t): _type(t) {
  }

  Type getType() { return _type; }


  virtual void print() = 0;
  

};

class B : public A {
 public:
  B(): A(Type::B) {}

  virtual void print() override {
    std::cout << "B" << std::endl;
  }
  
};

class C : public A {
 public:
  C() : A(Type::C){}

  virtual void print() override {
    std::cout << "B" << std::endl;
  }
};

class D : public A {
 public:
  D() : A(Type::D){}
  virtual void print() override {
    std::cout << "B" << std::endl;
  }
};

#include <random>

int main() {

  std::random_device rd;
  std::mt19937 gen(rd());
  std::uniform_int_distribution<> dis(1, 3);
  
  size_t upper = 100000000;

  std::vector<A*> data;
  for(size_t i=0; i < upper; ++i) {
    auto v = dis(gen);
    if (v == 1) {
      data.push_back(new B());
    } else if (v == 2) {
      data.push_back(new C());
    } else {
      data.push_back(new D());
    }
  }
    
  std::chrono::time_point<std::chrono::system_clock> start, end;
  size_t x = 0;
  
  start = std::chrono::system_clock::now();
  for(size_t i=0; i < upper; ++i)
    x += dynamic_cast<B*>(data[i]) != nullptr ? 1 : 0;
  end = std::chrono::system_clock::now();
  std::cout << x << " " <<  std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count() << std::endl;


  for(size_t j=0; j < 3; ++j) {
    x = 0;
    for(size_t i=upper-1; i >= 9; --i) {
      x += dynamic_cast<C*>(data[i]) != nullptr ? 1 : 0;
    }
  }


  x = 0;
  start = std::chrono::system_clock::now();
  for(size_t i=0; i < upper; ++i)
    x += data[i]->getType() == A::Type::B ? 1 : 0;
  end = std::chrono::system_clock::now();
  std::cout << x << " " <<  std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count() << std::endl;

  return 0;
}