What is fastest?

[carl]

What is fastest, indexing or iterating a std::vector:


std::vector<std::string> container;
// Add 100000 strings to container

std::vector<std::string>::iterator it = container.begin()
while (it != container.end()) {
std::string str = *it;
// do something with str
it++;
}


or

int size = container.size();
for (int i=0; i< size; i++) {
std::string str = container;
// do something with str
}

On this page:

http://stackoverflow.com/questions/...-an-stl-vector-with-vectoriterator-or-with-at


there are some different opinions, but what are your experinces?

 

[Victor Bazarov]

What is fastest, indexing or iterating a std::vector:


std::vector<std::string> container;
// Add 100000 strings to container

std::vector<std::string>::iterator it = container.begin()
while (it != container.end()) {
std::string str = *it;
// do something with str
it++;
}


or

int size = container.size();
for (int i=0; i< size; i++) {
std::string str = container;
// do something with str
}

On this page:

http://stackoverflow.com/questions/...-an-stl-vector-with-vectoriterator-or-with-at



there are some different opinions, but what are your experinces?

In my experience, those things are compiler-specific, system-specific,
and cannot be theorised upon. They need to be measured.

V

 

[Bo Persson]

What is fastest, indexing or iterating a std::vector:


std::vector<std::string> container;
// Add 100000 strings to container

std::vector<std::string>::iterator it = container.begin()
while (it != container.end()) {
std::string str = *it;
// do something with str
it++;
}


or

int size = container.size();
for (int i=0; i< size; i++) {
std::string str = container;
// do something with str
}

On this page:

http://stackoverflow.com/questions/...-an-stl-vector-with-vectoriterator-or-with-at


there are some different opinions, but what are your experinces?

I think that "different opinions" is the correct result

It varies some, but the difference is VERY small. The "do something
with str" is highly likely to dominate the timing anyway.


Bo Persson