Stop Using std::vector Wrong: C++ Optimization Techniques

• 0:00 Introduction: Discusses common misuses of std::vector in C++ and how to improve performance, particularly focusing on memory allocation and copying.
• 0:40 Stack vs. Heap: Emphasizes the performance difference between stack and heap memory allocation. std::array (stack) is faster than std::vector (heap). If the size is known, prefer std::array.
• 6:12 Example 1: Unnecessary Vector: Uses an example from a Tetris clone code review where a function returns a vector of 8 colors. This could be an std::array since the size is fixed.
• 10:15 Avoid Copying Vectors: Pass vectors by const reference to functions to avoid unnecessary copies, especially large vectors.
• 11:07 Example 2: Copying Within a Function: Shows how creating temporary vectors within functions leads to copying. Use const references instead.
• 11:33 Reserve or Resize: If the vector size is known or can be estimated, use reserve or resize to pre-allocate memory and avoid reallocations during push_back. Explains the behavior of push_back and capacity growth in different C++ standard library implementations (MSVC, Clang, GCC).
• 17:04 Emplace Back: Instead of creating objects and then pushing them onto the vector (which causes a copy), use emplace_back to construct objects directly in place within the vector's memory.
• 18:50 Move Semantics: While moving is better than copying, it's still less efficient than emplace_back. Explains how move constructors help, but are not the optimal solution.
• 21:05 Example 3: Back to Arrays: Reinforces using std::array whenever possible. Rewrites the example code to use an array and eliminates heap allocation entirely.
• 22:03 Summary: Three key takeaways: 1) Don't use std::vector if std::array will do; 2) Pre-allocate if the size is known; 3) Use emplace_back to avoid copies and moves.