Element Storage: Pointer-Owned vs Value-Owned Elements

Question 49 / 51 • Correct so far: 0 (0 answered)

Snippet A

Ptr Vector

std::vector<std::unique_ptr<Widget>> makeWidgets() {
    std::vector<std::unique_ptr<Widget>> v;
    v.reserve(kNumWidgets);
    for (int i = 0; i < kNumWidgets; ++i)
        v.push_back(std::make_unique<Widget>(i, static_cast<float>(i)));
    return v;
}

long long sum = 0;
for (const auto& p : PTR_WIDGETS)
    sum += p->id;
benchmark::DoNotOptimize(sum);
Snippet B

Value Vector

std::vector<Widget> makeWidgets() {
    std::vector<Widget> v;
    v.reserve(kNumWidgets);
    for (int i = 0; i < kNumWidgets; ++i)
        v.push_back(Widget{i, static_cast<float>(i)});
    return v;
}

long long sum = 0;
for (const auto& w : VAL_WIDGETS)
    sum += w.id;
benchmark::DoNotOptimize(sum);
Shared test data (shared-setup) 
struct Widget {
    Widget(int i, float v) : id(i), value(v) {}
    int   id;
    float value;
};

constexpr int kNumWidgets = 4096;

Which snippet is faster?

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