// modified pointer chase from:
// http://www.mathematik.uni-ulm.de/numerik/teaching/ss11/ScientificComputing/teil1/pointer-chasing.cpp

#include <iostream>
#include <chrono>
#include <stdlib.h>

typedef std::chrono::system_clock::time_point  tp_t;
typedef std::chrono::milliseconds ms_t;

volatile void* global; // so not to have optimizations

void chase_pointers(ms_t allowed_time);

int main(int argc, char* argv[]) {
  chase_pointers(ms_t(atoi(argv[1])));
  return 0;
}

void chase_pointers(ms_t allowed_time) {
  tp_t exit_time(std::chrono::system_clock::now() + allowed_time);

  static unsigned int size = 1024;
  static unsigned int len = size/sizeof(void*) + 1;
  void** memory = new void*[len];

  static unsigned int count = size*256;

  void** p;

  // shuffle indices
  int* indices = new int[len];
  for (unsigned int i = 0; i < len; i++) {
    if (exit_time < std::chrono::system_clock::now()) { goto do_exit; }
    indices[i] = i;
  }

  for (unsigned int i = 0; i < (len - 1); i++) {
    if (exit_time < std::chrono::system_clock::now()) { goto do_exit; }
    unsigned int j = i + lrand48()%(len - i);
    if (i != j) {
      int tmp = indices[i]; indices[i] = indices[j]; indices[j] = tmp;
    }
  }

  // fill memory with pointer references
  for (unsigned int i = 1; i < len; ++i) {
    if (exit_time < std::chrono::system_clock::now()) { goto do_exit; }
    memory[indices[i - 1]] = (void*)&memory[indices[i]];
  }
  memory[indices[len - 1]] = (void*)&memory[indices[0]];
  delete[] indices;

  // chase the pointers
  p = (void**)memory[0];
  while (count-- > 0) {
    if (exit_time < std::chrono::system_clock::now()) { goto do_exit; }
    p = (void**)*p;
  }
  global = *p;

 do_exit:
  delete[] memory;
}