#include <iostream>
#include <fstream>
#include <chrono>

using namespace std;
using namespace std::chrono;

int main()
{
    ifstream in_file; // An input file stream variable
    int size = 0; // A number of elements in a signal series
    // Open the file stream
    in_file.open("signal.txt");
    // Check that the file was opened
    if (!in_file)
    {
        cerr << "Unable to open file signal.txt";
        exit(1);   // call system to stop
    }
    in_file >> size;
    cout << "Number of elements: " << size << endl;
    float *A = new float[ 2 * size ];
    float *Sums = new float[ 1 * size ];
    cout << "Reading series...";
    for (int i = 0; i < size; i++)
    {
        float value = 0.0;
        in_file >> value;
        A[i] = value;
        A[i + size] = value;
    }
    cout << "Done." << endl;
    // Serial implementation of the autocorrelation sum
    cout << "Calculating sums...";
    high_resolution_clock::time_point t1 = high_resolution_clock::now();
    for( int shift = 0; shift < size; shift++ )
    {
        float sum = 0.0;
        for (int i = 0; i < size; i++)
        {
            sum += A[i] * A[i + shift];
        }
        Sums[shift] = sum;
    }
    high_resolution_clock::time_point t2 = high_resolution_clock::now();
    duration<double> time_span = t2 - t1;
    cout << "Done in " << time_span.count() << " seconds." << endl;
    // Close the input stream
    in_file.close();
    delete [] A;
    delete [] Sums;
    return 0;
}