std::vector::reserve performance penalty

Question

inline void add(const DataStruct& rhs) {
   using namespace boost::assign;
   vec.reserve(vec.size() + 3);
   vec += rhs.a, rhs.b, rhs.c;
}

The

Answer 1

If you profiled the code I bet you would see that the += IS very fast, the problem is the reserve is killing you. You should really only use reserve when you have some knowledge of how big the vector will grow to. If you can guess ahead of time then do ONE reserve, otherwise just go with the default push_back.