Move Semantis: Two Nice Properties

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67

// packagedTask.cpp

#include <utility>
#include <future>
#include <iostream>
#include <thread>
#include <deque>

class SumUp{
  public:
    int operator()(int beg, int end){
      long long int sum{0};
      for (int i= beg; i < end; ++i ) sum += i;
      return sum;
    }
};

int main(){

  std::cout << std::endl;

  SumUp sumUp1;
  SumUp sumUp2;
  SumUp sumUp3;
  SumUp sumUp4;

  // define the tasks
  std::packaged_task<int(int,int)> sumTask1(sumUp1);
  std::packaged_task<int(int,int)> sumTask2(sumUp2);
  std::packaged_task<int(int,int)> sumTask3(sumUp3);
  std::packaged_task<int(int,int)> sumTask4(sumUp4);

  // get the futures
  std::future<int> sumResult1= sumTask1.get_future();
  std::future<int> sumResult2= sumTask2.get_future();
  std::future<int> sumResult3= sumTask3.get_future();
  std::future<int> sumResult4= sumTask4.get_future();

  // push the tasks on the container
  std::deque< std::packaged_task<int(int,int)> > allTasks;
  allTasks.push_back(std::move(sumTask1));
  allTasks.push_back(std::move(sumTask2));
  allTasks.push_back(std::move(sumTask3));
  allTasks.push_back(std::move(sumTask4));
  
  int begin{1};
  int increment{2500};
  int end= begin + increment;

  // execute each task in a separate thread
  while ( not allTasks.empty() ){
    std::packaged_task<int(int,int)> myTask= std::move(allTasks.front());
    allTasks.pop_front();
    std::thread sumThread(std::move(myTask),begin,end);
    begin= end;
    end += increment;
    sumThread.detach();
  }

  // get the results
  auto sum= sumResult1.get() + sumResult2.get() + sumResult3.get() + sumResult4.get();

  std::cout << "sum of 0 .. 10000 = " << sum << std::endl;

  std::cout << std::endl;

}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46

// moveAlgorithm.cpp
#include <numeric> 
#include <algorithm> 
#include <iostream>
#include <utility>
#include <vector>
 
class MyInt{
public:
    MyInt(int i_):i(i_){}
    
    // copy semantic
    MyInt(const MyInt&)= delete;
    MyInt& operator= (const MyInt&)= delete;
    
    // move semantic
    MyInt(MyInt&&)= default;
    MyInt& operator= (MyInt&&)= default;
    
    int getVal() const {
        return i;
    }
private:
    int i;
};

int main(){
    
    std::cout << std::endl;
    
    std::vector<MyInt> vecMyInt;
    for (auto i= 1; i <= 10; ++i){
        vecMyInt.push_back(std::move(MyInt(i)));
    }
    
    std::for_each(vecMyInt.begin(), vecMyInt.end(), [](MyInt& myInt){ std::cout << myInt.getVal() << " "; });
    
    std::cout << std::endl;
    
    auto myInt= MyInt(std::accumulate(vecMyInt.begin(), vecMyInt.end(),MyInt(1),[](MyInt& f, MyInt& s){ return f.getVal() * s.getVal(); }));
    
    std::cout << "myInt.getVal(): " << myInt.getVal() << std::endl;
    
    std::cout << std::endl;
    
}

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54

// copyFallbackMove.cpp

#include <iostream>
#include <type_traits>
#include <utility>

template <typename T>
void swapMove(T& a, T& b){
    T tmp(std::move(a));
    a= std::move(b);
    b= std::move(tmp);
}

class MyInt{
public:
    MyInt(int i_):i(i_){}
    
    // copy semantic
    MyInt(const MyInt& myInt):i(myInt.getVal()){}
    MyInt& operator= (const MyInt& myInt){
        i= myInt.getVal();
        return *this;
    }
        
    int getVal() const {
        return i;
    }
private:
    int i;
};

int main(){
    
    std::cout << std::endl;
    MyInt myInt1(1);
    MyInt myInt2(2);
    
    std::cout << std::boolalpha;
    
    std::cout << "std::is_trivially_move_constructible<MyInt>::value " << std::is_trivially_move_constructible<MyInt>::value << std::endl;
    std::cout << "std::is_trivially_move_assignable<MyInt>::value " << std::is_trivially_move_assignable<MyInt>::value << std::endl;
    
    std::cout << "myInt1.getVal() :" << myInt1.getVal() << std::endl;
    std::cout << "myInt2.getVal() :" << myInt2.getVal() << std::endl;
    
    swapMove(myInt1,myInt2);
    std::cout << std::endl;
    
    std::cout << "myInt1.getVal() :" << myInt1.getVal() << std::endl;
    std::cout << "myInt2.getVal() :" << myInt2.getVal() << std::endl;
    
    std::cout << std::endl;
    
}