max_element benchmarking

max_element.c++

#include <nonius/main.h++>

#include <vector>
#include <algorithm>

namespace my {
int* max_element1(int* first, int* last)
{
    int* result = first;

    while(++first != last)
        if(*result < *first)
            result = first;
    return result;
}
int* max_element2(int* first, int* last)
{
    int* result = first;

    ++first;
    for(; first != last; ++first)
        if(*result < *first)
            result = first;
    return result;
}
int* max_element3(int* first, int* last)
{
    int* result = first, prev = *result;

    while(++first != last)
        if(prev < *first)
            result = first, prev = *result;
    return result;
}
decltype(max_element1)* max_element_f[] = {max_element1, max_element2, max_element3};
}

std::vector<int> make_test_vector()
{
    const int size = 1 << 20;
    std::vector<int> vec;
    for (int i = 0; i < size; i++)
    {
        if (i == 59)
        {
            vec.push_back(1000000012);
        }
        else
        {
            vec.push_back(i);
        }
    }
    return vec;
}

NONIUS_BENCHMARK("with while", [](nonius::chronometer meter)
{
    auto data = make_test_vector();
    meter.measure([&] { volatile int i = *my::max_element_f[0](&*data.begin(), &*data.end()); });
})

NONIUS_BENCHMARK("with for", [](nonius::chronometer meter)
{
    auto data = make_test_vector();
    meter.measure([&] { volatile int i = *my::max_element_f[1](&*data.begin(), &*data.end()); });
})

NONIUS_BENCHMARK("commoned", [](nonius::chronometer meter)
{
    auto data = make_test_vector();
    meter.measure([&] { volatile int i = *my::max_element_f[2](&*data.begin(), &*data.end()); });
})