AOS vs SOA

main.cpp

#include <chrono>
#include <iostream>
#include <vector>
#include <numeric>

const int size = 8 * 1024 * 1024;

double average(std::vector<long> const &v) {
    if (v.empty()) {
        return 0;
    }

    return std::reduce(v.begin(), v.end()) / (double) v.size();
}

struct MyStruct {
    int a,
        b,
        c,
        d,
        e,
        f,
        g,
        h;
};
auto aos = new MyStruct[size];
auto aop = new MyStruct *[size];

struct SOA {
    int a[size];
    int b[size];
    int c[size];
    int d[size];
    int e[size];
    int f[size];
    int g[size];
    int h[size];
};

long testAOP();

long testAOS();

long testSOA();

auto soa = new SOA;

int main() {

    std::vector<long> aop;
    std::vector<long> aos;
    std::vector<long> soa;
    for (int i = 0; i < 20; i++) {
        aop.push_back(testAOP());
        aos.push_back(testAOS());
        soa.push_back(testSOA());
    }

    std::cout << "AOP: " << average(aop) << std::endl;
    std::cout << "AOS: " << average(aos) << std::endl;
    std::cout << "SOA: " << average(soa) << std::endl;
}

long testSOA() {
    std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
    for (int i = 0; i < size; ++i) {
        soa->a[i] = soa->a[i] + 1;
    }
    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
    return std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count();
}

long testAOS() {
    std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
    for (int i = 0; i < size; ++i) {
        aos[i].a = aos[i].a + 1;
    }
    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
    return std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count();
}

long testAOP() {
    long ms;
    std::vector<char *> pointersToClear;
    for (int i = 0; i < size; ++i) {
        aop[i] = new MyStruct;
        for (int k = 1; k < rand() % 15 + 1; k++)//simulate memory load
            pointersToClear.push_back(new char[64]{});
    }
    for (const auto &item: pointersToClear)
        delete[] item;
    std::chrono::steady_clock::time_point begin = std::chrono::steady_clock::now();
    for (int i = 0; i < size; ++i) {
        aop[i]->a = aop[i]->a + 1;
    }
    std::chrono::steady_clock::time_point end = std::chrono::steady_clock::now();
    ms = std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count();

    for (int i = 0; i < size; ++i) {
        delete aop[i];
    }
    return ms;


}