Задачки для себя 0x01

#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <future>
 
double CalculatePi(const size_t iterationsCount)
{
  double pi = 0.0;
  double nominator = 1.0;
  double denominator = 1.0;
  
  for (size_t i = 0; i < iterationsCount; i++)
  {
    pi = pi + nominator / denominator;
    nominator = nominator * (-1.0);
    denominator = denominator + 2.0;
  }  
  pi = pi * 4.0;
  
  return pi;
}
 
class TPiCalculator
{
private:
  std::vector<unsigned int> iterations;
  std::vector<double> calculationResults;
public:
  TPiCalculator(unsigned int iterations[], const size_t length);
  std::vector<double> getResults();
  void Calculate();
  std::string ComposeResults();
};
 
TPiCalculator::TPiCalculator(unsigned int descriptor[], const size_t length)
{
  iterations.assign(descriptor, descriptor + length);
}
 
void TPiCalculator::Calculate()
{
  std::vector<std::shared_future<double>> executionResults;
  
  for (auto it : iterations)
      executionResults.push_back(std::async(CalculatePi, it));
      
  for (auto it : executionResults)
      calculationResults.push_back(it.get());
}
 
std::vector<double> TPiCalculator::getResults()
{
  return calculationResults;
}
 
std::string TPiCalculator::ComposeResults()
{
  std::ostringstream oss;
  
  oss << std::setprecision(12);
  
  for (size_t i = 0; i < calculationResults.size(); i++)
  {
    oss << "Thread " << std::setw(3) << i + 1 << " : iterations = " 
        << std::setw(10) << iterations[i] << ",\tPi = " << calculationResults[i]
        << std::endl;
  }
  
  return oss.str();
}
 
int main()
{
  unsigned int a[] = {10000000, 1000000, 100000, 10000, 1000, 100, 10, 1};
    
  TPiCalculator calculator(a, sizeof(a) / sizeof(*a));
  
  calculator.Calculate();
  
  std::cout << calculator.ComposeResults() << std::endl;
  
  return 0;
}