Thread

#include <iostream>
#include <windows.h>
#include <list>
#include <iterator> 
using namespace std;

CRITICAL_SECTION cs;

static long num_steps = 100000;
double step, pi;
double sum = 0.0;



DWORD WINAPI CaculaSum(LPVOID p) {
    // em Chưa convert được LPVOID thành list 
     list<int> arrs = (list<int>) p;
     double x;
      EnterCriticalSection(&cs); // đầu vào đợi
      
      for (list <int> ::iterator it = g.begin(); it != g.end(); ++it) {
          x = (*it + 0.5) * step;
          sum = sum + 4.0 / (1.0 + x * x);
      }

      LeaveCriticalSection(&cs);// Xong thì ra

      return 0;
  }


int main()
{
    list<int> params1;
    list<int> params2;
    list<int> params3;
    list<int> params4;

    HANDLE hThreads[4];
    InitializeCriticalSection(&cs);

    step = 1.0 / (double)num_steps;

    for (int i = 0; i < num_steps; i++) {

        if (i % 4 == 0) {
            params1.push_back(i);
        }
        if (i % 4 == 1) {
            params2.push_back(i);
        }
        if (i % 4 == 2) {
            params3.push_back(i);
        }
        if (i % 4 == 3) {
            params4.push_back(i);
        }

    }

    hThreads[0] = CreateThread(0, 0, CaculaSum, &params1, 0, 0);
    hThreads[1] = CreateThread(0, 0, CaculaSum, &params2, 0, 0);
    hThreads[2] = CreateThread(0, 0, CaculaSum, &params3, 0, 0);
    hThreads[3] = CreateThread(0, 0, CaculaSum, &params4, 0, 0);


    WaitForMultipleObjects(4, hThreads, TRUE, INFINITE); // đa luồng
    pi = step * sum;
    std::cout<< pi;
    DeleteCriticalSection(&cs); // xóa luồng

}