Republic Day Insights: Effective Vector Memory Management
vector memory management
#include <iostream>
#include <vector>
int main(){
std::vector<int> v;
std::cout<<"Initial Capacity: "<< v.capacity() <<"\n";
for (int i = 0; i < 10; ++i){
v.push_back(i);
std::cout<<" Size: " << v.size()
<<" | Capacity: "<< v.capacity()
<<" | Address of v[0]: " << &v[0] << "\n";
}
return 0;
}
This code scales, but it has a problem known as the doubling strategy!
but, it’s not a problem, basically we all know vector is a dynamic array
but what makes it dynamic is the doubling strategy
the vector starts with 0 initial capacity, then we add 1, so it increase it’s capacity by 1
basically the whole vector moves to new position of size: 1 , now we add another element: 2,
it resizes itself to 1×2 = 2 , not resize but move to a new space with size:2
now another element:3 (here) , it resizes 2×2=4, and so on,
the vector sizes become 0,1,2,4,8,16…
this is a problem for high frequency trading firm
THE SOLUTION(WRONG ONE: My thought) → we use v(10) at the starting of the vector while initializing
vector<int> v(10);
what’s wrong? it actually makes an array with 10 zeroes initialized
and the element to be added will go to 11th position where size of v: 10×2=20;
LOL
correct approach? use reverse()
vector<int> v;
v.reserve(10);
- it tells the compiler, we are expecting 10 values here, until then don’t resize!!!!!
