Dynamically allocated arrays or std::vector

Question

I\'m trying to optimize my C++ code. I\'ve searched the internet on using dynamically allocated C++ arrays vs using std::vector and have generally seen a recommendation in f

Answer 1

I think the answer here is obvious: it doesn't matter. Like jalf said the code will end up being about the same, but even if it wasn't, look at the numbers. The code you posted creates a huge array of 10 MILLION items, yet iterating over the entire array takes only a few hundredths of a second.

Even if your application really is working with that much data, whatever it is you're actually doing with that data is likely to take much more time than iterating over your array. Just use whichever data structure you prefer, and focus your time on the rest of your code.

To prove my point, here's the code with one change: the assignment of i to the array item is replaced with an assignment of sqrt(i). On my machine using -O2, the execution time triples from .02 to .06 seconds.

#include 
#include 
#include 
#include 

using namespace std;

int main() {
  clock_t start,end;
  std::vector vec(9999999);
  std::vector::iterator vecIt = vec.begin();
  std::vector::iterator vecEnd = vec.end();

  start = clock();
  for (int i = 0; vecIt != vecEnd; i++) {
    *(vecIt++) = sqrt(i);
  }
  end = clock();
  cout<<"vector: "<<(double)(end-start)/CLOCKS_PER_SEC<