Vector: initialization or reserve?

Question

I know the size of a vector, which is the best way to initialize it?

Option 1:

vector vec(3); //in .h
vec.at(0)=var1;             


        

Answer 1

Another option is to Trust Your Compiler(tm) and do the push_backs without calling reserve first. It has to allocate some space when you start adding elements. Perhaps it does that just as well as you would?

It is "better" to have simpler code that does the same job.