shared_ptr in a Loop: Copy per Iteration vs. Reuse Handle

Question 32 / 51 • Correct so far: 0 (0 answered)

Snippet A

Shared Ptr Loop Copy

long long processShared(const std::shared_ptr<std::vector<int>>& src) {
    long long sum = 0;
    for (int iter = 0; iter < kLoopCount; ++iter) {
        std::shared_ptr<std::vector<int>> local = src;
        for (int x : *local) sum += x;
    }
    return sum;
}

long long result = processShared(SHARED_DATA);
Snippet B

Raw Ptr Cached

long long processRaw(const std::shared_ptr<std::vector<int>>& src) {
    long long sum = 0;
    for (int iter = 0; iter < kLoopCount; ++iter)
        for (int x : *src) sum += x;
    return sum;
}

long long result = processRaw(SHARED_DATA);
Shared test data (shared-setup) 
constexpr int kDataSize  = 16;
constexpr int kLoopCount = 16;

static std::shared_ptr<std::vector<int>> makeData() {
    auto v = std::make_shared<std::vector<int>>(kDataSize);
    std::iota(v->begin(), v->end(), 1);
    return v;
}

static const std::shared_ptr<std::vector<int>> SHARED_DATA = makeData();

Which snippet is faster?

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