Operating-System-Lab/8_LRU_Page_Replacement.c at main · Suraj-G-Rao/Operating-System-Lab · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
/*
Page Reference String : 1 2 3 4 1 2 5 1 2 3 4 5

Page Fault      Frames: 1 -1 -1
Page Fault      Frames: 1 2 -1
Page Fault      Frames: 1 2 3
Page Fault      Frames: 4 2 3
Page Fault      Frames: 4 1 3
Page Fault      Frames: 4 1 2
Page Fault      Frames: 5 1 2
Page Hit        Frames: 5 1 2
Page Hit        Frames: 5 1 2
Page Fault      Frames: 3 1 2
Page Fault      Frames: 3 4 2
Page Fault      Frames: 3 4 5

Total Page Faults: 10
*/
#include <stdio.h>
#include <stdbool.h>

void lru(int pages[], int n, int capacity) {
    int frames[capacity];
    int pageLastUsed[capacity];
    int pageFaults = 0;

    for (int i = 0; i < capacity; i++) {
        frames[i] = -1;
        pageLastUsed[i] = -1;
    }
    for (int i = 0; i < n; i++) {
        int currentPage = pages[i];
        bool pageFound = false;

        for (int j = 0; j < capacity; j++) {
            if (frames[j] == currentPage) {
                pageFound = true;
                pageLastUsed[j] = i;
                break;
            }
        }

        if (!pageFound) {
            int lruIndex = 0;
            int minLastUsed = pageLastUsed[0];
            for (int j = 1; j < capacity; j++) {
                if (pageLastUsed[j] < minLastUsed) {
                    minLastUsed = pageLastUsed[j];
                    lruIndex = j;
                }
            }
            frames[lruIndex] = currentPage;
            pageLastUsed[lruIndex] = i;
            pageFaults++;
            printf("Page Fault   \t");
        } else {
            printf("Page Hit     \t");
        }

        printf("Frames: ");
        for (int j = 0; j < capacity; j++)
            printf("%d ", frames[j]);
        printf("\n");
    }

    printf("\n\nTotal Page Faults: %d\n", pageFaults);
}

int main() {
    int num,frames;

    printf("Enter the number of pages : ");
    scanf("%d", &num);
    int pages[num];
    printf("Enter The Reference String : ");
    for (int i = 0; i < num; i++)    scanf("%d", &pages[i]);

    printf("Enter the number of frames : ");
    scanf("%d", &frames);

    printf("Page Reference String : ");
    for (int i = 0; i < num; i++)    printf("%d ", pages[i]);
    printf("\n\n");

    lru(pages, num, frames);

    return 0;
}