Are const_iterators faster?

c++ stl iterator const-iterator
aJ. picture aJ. · Apr 16, 2009 · Viewed 14.8k times · Source

Our coding guidelines prefer const_iterator, because they are a little faster compared to a normal iterator. It seems like the compiler optimizes the code when you use const_iterator.

Is this really correct? If yes, what really happens internally that makes const_iterator faster?.

EDIT: I wrote small test to check const_iterator vs iterator and found varying results:

For iterating 10,000 objects const_terator was taking a few milliseconds (around 16 ms) less. But not always. There were iterations in which both were equal.

Answer

unwind picture unwind · Apr 16, 2009

If nothing else, a const_iterator reads better, since it tells anyone reading the code "I'm just iterating over this container, not messing with the objects contained".

That's a great big win, never mind any performance differences.

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