The cost of passing by shared_ptr

Always pass your shared_ptr by const reference:

void f(const shared_ptr<Dataset const>& pds) {...} 
void g(const shared_ptr<Dataset const>& pds) {...} 

Edit: Regarding the safety issues mentioned by others:

• When using shared_ptr heavily throughout an application, passing by value will take up a tremendous amount of time (I’ve seen it go 50+%).
• Use const T& instead of const shared_ptr<T const>& when the argument shall not be null.
• Using const shared_ptr<T const>& is safer than const T* when performance is an issue.