path: root/tests/functional_tests/cpu_power_test.cpp

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const char * descr = 
"This program prints the time (ms) needed to calculate a mathematical challenge. It's purpose \n\
is to be able to use the result to compare the CPU power available on the machine it's being executed \n\
and under the given circumstances, which can differ for the same machine. For example: \n\
The printed value will be different when using 2 of 2 cores, when there an another process \n\
running on one of the cores core, and when no other intense process running. \n\
 \n\
The program expects a one argument: a numerical value of the threads to start the calculations on. \n\
 \n\
Prints: \n\
Time to calculate a mathematical challenge in MILLISECONDS. \n\
 \n\
Returns: \n\
0 on success, \n\
1 on a missing argument, \n\
2 on an incorrect format of the argument.\n";

#include <iostream>
#include <future>
#include <vector>
#include <sstream>
#include <chrono>

using namespace std;

/**
Uses Leibniz Formula for Pi.
https://en.wikipedia.org/wiki/Leibniz_formula_for_%CF%80
*/
static double calcPi(const size_t max_iter)
{
    const double n = 4;
    double pi = 0;
    double d = 1;
    for (size_t i = 1; i < max_iter; ++i)
    {
        const double a = 2.0 * (i % 2) - 1.0;
        pi += a * n / d;
        d += 2;
    }
    return pi;
}

int main(int argc, const char ** argv)
{
    const size_t max_iter = 1e9;
    if (argc < 2)
    {
        cout << "Please pass the number of threads to run.\n";
        
        cout << '\n' << descr << '\n';
        return 1;
    }
    
    // Convert argument to an integer.
    int numThreads = 1;
    const char * numThreadsStr = argv[1];
    std::istringstream iss(numThreadsStr);
    if (! (iss >> numThreads) )
    {
        cout << "Incorrect format of number of threads = '" << numThreadsStr << "'\n";
        return 2;
    }
    // Run the calculation in parallel.
    std::vector<std::future<double>> futures;
    for(int i = 0; i < numThreads; ++i) 
    {
        futures.push_back(std::async(calcPi, max_iter));
    }    
    
    // Start measuring the time.
    const std::chrono::steady_clock::time_point tbegin = std::chrono::steady_clock::now();
    for(auto & e : futures) 
    {
       e.get();
    }
    // Stop measuring the time.
    const std::chrono::steady_clock::time_point tend = std::chrono::steady_clock::now();
    
    // Print the measured duration.
    cout << std::chrono::duration_cast<std::chrono::milliseconds>(tend - tbegin).count() << std::endl;
    return 0;
}