Is it counter-productive to pass primitive types by reference? [duplicate]

Question

Possible Duplicate:
Is it better to pass by value or by reference for basic datatypes?
Reasons to not pass simple types by reference?

I did some testing where I had two scenarios, each with two identical functions- one passing the parameter by reference and the other by value. The scenario with strings showed a massive performance increase (because a copy of string is made, calling a constructor) whereas the test with long didn't show any performance increase when passing the value by reference. In fact, sometimes the performance was worse.

Is this expected with primitive types? Is there no point passing them by reference?

I was expecting a copy of a primitive type is made when not using by reference and therefore expected a small performance-boost.

Answer 1

You get the best performance from passing primitive types by value. This is because:

• primitives are blitable, so the cost of the copy depends on the size
• primitives are small, only double and long long are bigger than a reference in most environments
• pass-by-value avoids aliasing, allowing the optimizer to really do its thing

This last point is often overlooked but can make a considerable difference.