Small 

for (int j = 0; j < 23; ++j) {
  std::string s;
  for (auto i = 0u; i < 22; ++i)
    s += 'a';
}

for (int j = 0; j < 22; ++j) {
  std::string s;
  for (auto i = 0u; i < 23; ++i)
    s += 'a';
}

* The benchmark is run under Apple Macbook Air M2.

* For the full benchmark code, please refer here.