lru_aging.cpp

#include <iostream>
#include <vector>
#include <stdio.h>
#include <math.h>

int find_page_in_frames(int frames[], int aging_regs[], int page_num, int num_frames, int history) {
  for(int i = 0; i < num_frames; i++) {
    aging_regs[i] = aging_regs[i]>>1;
  }
  for(int i = 0; i < num_frames; i++) {
    // If found = HIT
    if(frames[i] == page_num) {
      aging_regs[i] += pow(2, history);
      return i;
    }
  }
  // If not found = MISS
  return -1;
}

// Called in case of a MISS
int replace(int frames[], int aging_regs[], int new_page, int num_frames, int history) {
  int min_idx = 0;
  int min = aging_regs[min_idx];
  for(int i = 0; i < num_frames; i++) {
    if(aging_regs[i] < min){
      min_idx = i;
      min = aging_regs[min_idx];
    }
  }

  frames[min_idx] = new_page;
  aging_regs[min_idx] += pow(2, history);

  return min_idx;
}

void print_regs(int aging_regs[], int num_frames) {
  printf("Registers values now :\n");
  for(int i = 0; i < num_frames; i++) {
    printf("      %d\n", aging_regs[i]);
  }
}

void print_frame_state(int frames[], int num_frames) {
  printf("Current values in frames are :\n");
  for(int i = 0; i < num_frames; i++) {
    printf("      %d\n", frames[i]);
  }
}

// Takes vector of requests as input and outputs number of page faults
int lru_aging(int requests[], // array containing requests
  int num_frames_in_system, // to define the page frames in system
  int history_to_look, // how much bits would the register have
  int num_requests)
  {
    int aging_regs[num_frames_in_system] = {0};
    int page_faults = 0;
    int index = 0;
    int frames[num_frames_in_system] = {0};

    for (int j = 0; j < num_requests; j++) {
      index = find_page_in_frames(frames, aging_regs, requests[j], num_frames_in_system, history_to_look);
      if (index == -1) {
        page_faults++;
        int replaced_frame_idx = replace(frames, aging_regs, requests[j], num_frames_in_system, history_to_look);
        // printf("We replaced %d\n", replaced_frame_idx);
      } else {
        // printf("We replaced nothing !\n");
      }
      // print_frame_state(frames, num_frames_in_system);
      // print_regs(aging_regs, num_frames_in_system);
    }
    printf("%d\n", page_faults);

    return page_faults;
}



// int main() {
//   int num_frames = 6;
//   int history = 10;
//   int requests_length = 15;
//
//   // pages in memory :
//   //   a: 1
//   //   b: 2
//   //   c: 3
//   //    ....
//   //   and so on...
//   // request array consists of page indexes referenced
//   int requests[requests_length] = {3, 5, 1, 6, 3, 6, 8, 1, 4, 9, 2, 7, 7, 9, 5};
//   int faults = 0;
//
//   faults = lru_aging_policy(requests, num_frames, history, requests_length);
//
//   return 0;
// }