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std::vector spec leaves quite a bit of performance-critical details unspecified. I imagine the allocator behaviour differs enough between implementations that t

by plq 11y ago

std::vector spec leaves quite a bit of performance-critical details unspecified. I imagine the allocator behaviour differs enough between implementations that they implemented their own to keep performance in different platforms more predictable. The performance requirements for a physics engine can be quite different from the general case that the std::vector spec is aiming for. I imagine templates are frowned upon for the same reason -- too many moving parts. Otherwise they're perfectly fine to use in projects that have goals other than portably predictable performance.

hellofunk 11y ago
Good points, I hadn't considered that the implementation of a vector could widely vary. That makes sense.
- vvanders 11y ago
  Yup, the spec is also really vague on if clear() actually releases memory. AFAIK the only "correct" way to actually clear a vector is "vec = std::vector<T>()" with the STL.
  - hellofunk 11y ago
    That is rather interesting!
  - pragmatib 11y ago
    Actually you'd have to try harder: even this might leave the current capacity unchanged. The blessed idiom is vec.swap(std::vector<T>()); c++11 added shrink_to_fit which is a non binding request to reduce capacity.