sum_row_col.cpp

// CacheSmth.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <chrono>
#include <iostream>

struct Timer
{
    Timer()
    {
        reset();
    }

    void reportAndReset(const std::string& msg)
    {
        const auto end = std::chrono::system_clock::now();

        std::chrono::duration<double> elapsedSeconds = end - m_time;
        std::cout << msg.c_str() << " done in: " << elapsedSeconds.count() << "s" << std::endl;
        reset();
    }

    void reset()
    {
        m_time = std::chrono::system_clock::now();
    }


private:
    std::chrono::system_clock::time_point m_time;
};

using namespace std;

const int kDim = 10000;

float calcRow(float* matrix)
{
    float result = 0;
    for (int r = 0; r < kDim; r++) {
        for (int c = 0; c < kDim; c++) {
            const int offset = r * kDim + c;
            result += matrix[offset];
        }
    }

    return result;
}

float calcColumn(float* matrix)
{
    float result = 0;
    for (int c = 0; c < kDim; c++) {
        for (int r = 0; r < kDim; r++) {
            const int offset = r * kDim + c;
            result += matrix[offset];
        }
    }

    return result;
}

int main()
{
    float* matrix = new float[kDim * kDim];
    for (int i = 0; i <  kDim * kDim; i++) {
        matrix[i] = 1;
    }

    Timer t;
    const float row = calcRow(matrix);
    t.reportAndReset("Row");
    const float column = calcRow(matrix);
    t.reportAndReset("Calc");

    cout << "row: " << row << endl;
    cout << "column: " << column << endl;

    delete[] matrix;
    return 0;
}