Copy vs Reference, C++ (vc++)

Copy vs Reference

#include <iostream>
#include <chrono>
#include <array>

#define USE_BRANCH 0

struct TestStruct {
    // int val0{ 1 };
    int val1{ 2 };
    int val2{ 3 };
    // std::array<int, 100> padding{};
    // bool val3{};
};

std::array<TestStruct, 200> values{};
static int sum;

static void Copy() {
    for (const TestStruct ts : values) {
#if USE_BRANCH
        if (ts.val3)
#endif
        {
            sum += ts.val1;
            sum += ts.val2;
        }
    }
}

static void Reference() {
    for (const TestStruct& ts : values) {
#if USE_BRANCH
        if (ts.val3)
#endif
        {
            sum += ts.val1;
            sum += ts.val2;
        }
    }
}

int main()
{
    srand(time(0));

std::cout << "Struct: \t" << sizeof(TestStruct) << " bytes\n";

sum = 0;
    for (TestStruct& ts : values)
    {
        ts.val1 = rand() % 100;
        ts.val2 = rand() % 100;
    }

constexpr size_t NUM_ITERS = 10'000;
    long long copyTime, refTime;
    {
        const auto start = std::chrono::high_resolution_clock::now();

for (size_t i = 0; i < NUM_ITERS; ++i) {
            Copy();
        }

const auto end = std::chrono::high_resolution_clock::now();
        copyTime = std::chrono::duration_cast<std::chrono::microseconds>(end - start).count();
        std::cout << "Copy: \t\t" << copyTime << " microseconds\n";
        std::cout << "Sum: \t\t" << sum << "\n";
    }

sum = 0;
    for (TestStruct& ts : values)
    {
        ts.val1 = rand() % 100;
        ts.val2 = rand() % 100;
    }

{
        const auto start = std::chrono::high_resolution_clock::now();

for (size_t i = 0; i < NUM_ITERS; ++i) {
            Reference();
        }

const auto end = std::chrono::high_resolution_clock::now();
        refTime = std::chrono::duration_cast<std::chrono::microseconds>(end - start).count();
        std::cout << "Reference: \t" << refTime << " microseconds\n";
        std::cout << "Sum: \t\t" << sum << "\n";
    }
    std::cout << "\nRef is " << 1.0 / (double(refTime) / double(copyTime)) << "x the speed of Copy";
}


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