pointer vs integer indexing

#include <iostream>
#include <random>
#include <chrono>
#include <unistd.h>
#include <functional>

int main(void) {

  const int n{15000};
  int* p{new int[n]};

    int * ep{ p + n };

  auto rand2 = std::bind(std::uniform_int_distribution<>(7,102), std::mt19937(std::random_device()()));

    for(int * q{p}; q!=ep; ++q )
    {
    *q = rand2();
    }

  for (int j{0}; j < 20; j++) {
    {

      auto start_pointer = std::chrono::high_resolution_clock::now();
      for (int* q{p}; q != ep; ++q) {
        *q +=1;
      }
      auto end_pointer = std::chrono::high_resolution_clock::now();
      auto time_pointer = std::chrono::duration_cast<std::chrono::nanoseconds>(
                              end_pointer - start_pointer)
                              .count();
      std::cout << " Pointer: " << time_pointer << std::endl;
    }

    {
      auto start_pointer = std::chrono::high_resolution_clock::now();
      for (int* q{p}; q != ep; ++q) {
        *q += 1;
      }
      auto end_pointer = std::chrono::high_resolution_clock::now();
      auto time_pointer = std::chrono::duration_cast<std::chrono::nanoseconds>(
                              end_pointer - start_pointer)
                              .count();
      std::cout << " Pointer: " << time_pointer << std::endl;
    }

    {
      auto start_index_32 = std::chrono::high_resolution_clock::now();
      for (int i{0}; i != n; i++) {
        p[i] += 1;
      }
      auto end_index_32 = std::chrono::high_resolution_clock::now();
      auto time_index_32 = std::chrono::duration_cast<std::chrono::nanoseconds>(
                               end_index_32 - start_index_32)
                               .count();
      std::cout << "Index 32: " << time_index_32 << std::endl;
    }

    {
      auto start_index_32 = std::chrono::high_resolution_clock::now();
      for (int i{0}; i != n; i++) {
        p[i] += 1;
      }
      auto end_index_32 = std::chrono::high_resolution_clock::now();
      auto time_index_32 = std::chrono::duration_cast<std::chrono::nanoseconds>(
                               end_index_32 - start_index_32)
                               .count();
      std::cout << "Index 32: " << time_index_32 << std::endl;
    }

    {
      const std::size_t n_64{n};
      auto start_index_64 = std::chrono::high_resolution_clock::now();
      for (std::size_t i{0}; i != n_64; i++) {
        p[i] += 1;
      }
      auto end_index_64 = std::chrono::high_resolution_clock::now();
      auto time_index_64 = std::chrono::duration_cast<std::chrono::nanoseconds>(
                               end_index_64 - start_index_64)
                               .count();
      std::cout << "Index 64: " << time_index_64 << std::endl;
    }

    {
      const std::size_t n_64{n};
      auto start_index_64 = std::chrono::high_resolution_clock::now();
      for (std::size_t i{0}; i != n_64; i++) {
        p[i] += 1;
      }
      auto end_index_64 = std::chrono::high_resolution_clock::now();
      auto time_index_64 = std::chrono::duration_cast<std::chrono::nanoseconds>(
                               end_index_64 - start_index_64)
                               .count();
      std::cout << "Index 64: " << time_index_64 << std::endl;
    }
    std::cout << std::endl;
  }

  delete[] p;

  return 0;
}