Don't assume that complicated code is necessarily faster than simple code

Reason

Simple code can be very fast. Optimizers sometimes do marvels with simple code

Example, good

// clear expression of intent, fast execution

vector<uint8_t> v(100000);

for (auto& c : v)
    c = ~c;

Example, bad

// intended to be faster, but is often slower

vector<uint8_t> v(100000);

for (size_t i = 0; i < v.size(); i += sizeof(uint64_t)) {
    uint64_t& quad_word = *reinterpret_cast<uint64_t*>(&v[i]);
    quad_word = ~quad_word;
}

Note

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