Reference pass speed question

Question

Suppose I have an overloaded function that takes references to an int, a vector of ints, and a vector of vectors of ints.  For example, take the declarations to be:

void MyFunction(int& parameter);

void MyFunction(vector<int>& parameter);

void MyFunction(vector< vector<int> >& parameter);

My question is how do these different passed references affect execution time?  That is does the vector< vector<int> > reference take longer to pass than the vector<int> which takes longer than the int, or do they all take the same amount of time and execution time is unaffected?

Answer 1

Executiontime is unaffected, because you pass a reference, which have pointer-size.

It would be different, if you would pass the object itself, because then, the object must be copied, and copying would cost time.

Answer 2

>My question is how do these different passed references affect execution time?  That is does the vector< vector<int> > reference take longer to pass than the vector<int> which takes longer than the int, or do they all take the same amount of time and execution time is unaffected?

They're identical - what's passed is a reference, which is essentially
a pointer in all situations.

Dave

Answer 3

That is does the vector< vector<int> > reference take longer to pass han the vector<int> which takes longer than the int, or do they all take the same amount of time and execution time is unaffected?

Both take same time, exactly 4 byte or 8 bytes to push on stack, depending on 32/64-bit compilation. Reference and pointers need word-size of platform.

Answer 4

http://www.parashift.com/c++-faq-lite/value-vs-ref-semantics.html