Exploring the Performance Impacts of Memory Access Patterns - C++ Data Type

C++ examples for Data Type:time

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Description

Exploring the Performance Impacts of Memory Access Patterns

Demo Code

#include <chrono>
#include <iostream>

using namespace std;

const int NUM_ROWS{ 10000 };
const int NUM_COLUMNS{ 1000 };
int elements[NUM_ROWS][NUM_COLUMNS];
int* pElements[NUM_ROWS][NUM_COLUMNS];

int main(int argc, char* argv[])
{
    for (int i{ 0 }; i < NUM_ROWS; ++i)
    {/*from  w ww. j ava 2 s  . c  o  m*/
        for (int j{ 0 }; j < NUM_COLUMNS; ++j)
        {
            elements[i][j] = i*j;
            pElements[i][j] = new int{ elements[i][j] };
        }
    }

    auto start = chrono::high_resolution_clock::now();

    for (int i{ 0 }; i < NUM_ROWS; ++i)
    {
        for (int j{ 0 }; j < NUM_COLUMNS; ++j)
        {
            const int result{ elements[j][i] };
        }
    }

    auto end = chrono::high_resolution_clock::now();
    auto difference = end - start;

    cout << "Time taken for j then i: "
        << chrono::duration_cast<chrono::microseconds>(difference).count()
        << " microseconds!" << endl;

    start = chrono::high_resolution_clock::now();

    for (int i{ 0 }; i < NUM_ROWS; ++i)
    {
        for (int j{ 0 }; j < NUM_COLUMNS; ++j)
        {
            const int result{ elements[i][j] };
        }
    }
    end = chrono::high_resolution_clock::now();
    difference = end - start;

    cout << "Time taken for i then j: "
        << chrono::duration_cast<chrono::microseconds>(difference).count()
        << " microseconds!" << endl;

    start = chrono::high_resolution_clock::now();

    for (int i{ 0 }; i < NUM_ROWS; ++i)
    {
        for (int j{ 0 }; j < NUM_COLUMNS; ++j)
        {
            const int result{ *(pElements[i][j]) };
        }
    }

    end = chrono::high_resolution_clock::now();
    difference = end - start;

    cout << "Time taken for pointers with i then j: "
        << chrono::duration_cast<chrono::microseconds>(difference).count()
        << " microseconds!" << endl;

    return 0;
}

Result


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