test_alloc_elapse.cpp

#include <iostream>

using namespace std;

// compile without optimization
// clang++ -std=c++17 -stdlib=libc++ -O0 test_alloc.cpp

// elapse 6.25 seconds with N=100*1000*1000
size_t test_alloc(size_t N) {
    size_t r;
    while (N--) {
        auto p = new size_t(N); // malloc and init
        r = *p; // read once
        delete p; // dealloc
    }
    return N;
}

// elapse 0.17 seconds with N=100*1000*1000
size_t test_stack(size_t N) {
    size_t r;
    while (N--) {
        size_t a = N; // define and init
        r = a; // read once
    }
    return r;
}

int main() {
    return test_alloc(1000*1000*100);
    return test_stack(1000*1000*100);
}