Rule of thumb for when passing by value is faster than passing by const reference?

Question

Suppose I have a function that takes an argument of type T. It does not mutate it, so I have the choice of passing it by const reference const T&

Answer 1

If you're going to use a "rule of thumb" for by-value vs. by-const-reference, then do this:

• pick ONE approach and use it everywhere
• agree upon which one among all your coworkers
• only later, in the "hand-tuning performance" phase, start changing things
• and then, only change them if you see a measurable improvement