week6

week06/ex1.c

@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct {
+    int id, at, bt, et, tat, wt;
+} Process;
+
+int proc_cmp(const void *a, const void *b) {
+    return ((Process*)a)->at - ((Process*)b)->at;
+}
+
+int proc_cmp_id(const void *a, const void *b) {
+    return ((Process*)a)->id - ((Process*)b)->id;
+}
+
+int main() {
+    int n;
+    printf("Number of processes: ");
+    scanf("%d", &n);
+    Process p[n];
+
+    printf("Arrival time and Burst time:\n");
+    for (int i = 0; i < n; ++i) {
+        scanf("%d %d", &p[i].at, &p[i].bt);
+        p[i].id = i;
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp);
+
+    int curt = 0;
+    printf("ID\tAT\tBT\tET\tTAT\tWT\n");
+    double avg_tat = 0, avg_wt = 0;
+    for (int i = 0; i < n; ++i) {
+        p[i].et = (curt > p[i].at ? curt : p[i].at) + p[i].bt;
+        curt = p[i].et;
+
+        p[i].tat = p[i].et - p[i].at;
+        p[i].wt = p[i].tat - p[i].bt;
+        avg_tat += p[i].tat;
+        avg_wt += p[i].wt;
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp_id);
+    for (int i = 0; i < n; ++i) {
+        printf("%d\t%d\t%d\t%d\t%d\t%d\n", p[i].id, p[i].at, p[i].bt, p[i].et, p[i].tat, p[i].wt);
+    }
+
+    avg_tat /= n;
+    avg_wt /= n;
+    printf("avg:\t\t\t\t%lg\t%lg\n", avg_tat, avg_wt);
+}

week06/ex1.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+gcc ex1.c -o ex1.out
+./ex1.out

week06/ex2.c

@@ -0,0 +1,63 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+typedef struct {
+    int id, at, bt, et, tat, wt;
+} Process;
+
+int proc_cmp(const void *a, const void *b) {
+    return ((Process*)a)->bt - ((Process*)b)->bt;
+}
+
+int proc_cmp_id(const void *a, const void *b) {
+    return ((Process*)a)->id - ((Process*)b)->id;
+}
+
+int main() {
+    int n, mn = INT_MAX, curt = 0, jd = 0;
+    printf("Number of processes: ");
+    scanf("%d", &n);
+    Process p[n];
+
+    printf("Arrival time and Burst time:\n");
+    for (int i = 0; i < n; ++i) {
+        scanf("%d %d", &p[i].at, &p[i].bt);
+        p[i].id = i;
+        p[i].et = -1;
+        mn = (mn < p[i].at ? mn : p[i].at);
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp);
+
+    printf("ID\tAT\tBT\tET\tTAT\tWT\n");
+
+    double avg_tat = 0, avg_wt = 0;
+    while (jd < n) {
+        mn = INT_MAX;
+        for (int i = 0; i < n; ++i) {
+            if (p[i].et == -1)
+                mn = (mn < p[i].at ? mn : p[i].at);
+            if (p[i].at <= (mn > curt ? mn : curt) && p[i].et == -1) {
+                jd++;
+                p[i].et = (curt > p[i].at ? curt : p[i].at) + p[i].bt;
+                curt = p[i].et;
+                p[i].tat = p[i].et - p[i].at;
+                p[i].wt = p[i].tat - p[i].bt;
+                avg_tat += p[i].tat;
+                avg_wt += p[i].wt;
+                break;
+            }
+        }
+        curt = (curt > mn ? curt : mn);
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp_id);
+    for (int i = 0; i < n; ++i) {
+        printf("%d\t%d\t%d\t%d\t%d\t%d\n", p[i].id, p[i].at, p[i].bt, p[i].et, p[i].tat, p[i].wt);
+    }
+
+    avg_tat /= n;
+    avg_wt /= n;
+    printf("avg:\t\t\t\t%lg\t%lg\n", avg_tat, avg_wt);
+}

week06/ex2.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+gcc ex2.c -o ex2.out
+./ex2.out

week06/ex2.txt

@@ -0,0 +1,3 @@
+The shortest job first algorithm is definitely more fair compared to FCFS algorithm.
+The reason is obvious: the FCFS algorithm does care about only one thing - arival time,
+    which doesn't mean a lot to 'fairness' of a scheduler algorithm. As fairness, I mean decreasing the wait time and TAT.

week06/ex3.c

@@ -0,0 +1,99 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+
+typedef struct {
+    int id, at, bt, et, tat, wt, rt, used;
+} Process;
+
+int proc_cmp(const void *a, const void *b) {
+    return ((Process*)a)->at - ((Process*)b)->at;
+}
+
+int proc_cmp_id(const void *a, const void *b) {
+    return ((Process*)a)->id - ((Process*)b)->id;
+}
+
+int deq(int q[], int *sz) {
+    int res = q[0];
+    for (int i = 0; i < *sz-1; ++i) {
+        q[i] = q[i+1];
+    }
+    (*sz)--;
+    return res;
+}
+
+int main() {
+    int n, mn = INT_MAX, q, qsz = 0;
+    printf("Quantum: ");
+    scanf("%d", &q);
+    printf("Number of processes: ");
+    scanf("%d", &n);
+    Process p[n];
+    int ready[n];
+
+    printf("Arrival time and Burst time:\n");
+    for (int i = 0; i < n; ++i) {
+        scanf("%d %d", &p[i].at, &p[i].bt);
+        p[i].id = i;
+        p[i].et = -1;
+        p[i].used = 0;
+        p[i].rt = p[i].bt;
+        ready[i] = 0;
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp);
+
+    printf("ID\tAT\tBT\tET\tTAT\tWT\n");
+
+    double avg_tat = 0, avg_wt = 0;
+    int curt = 0, jd = 0;
+    ready[qsz++] = 0;
+    p[0].used = 1;
+    while (qsz > 0) {
+        int id = deq(ready, &qsz);
+        if (p[id].rt != 0) {
+            int ex = (p[id].rt < q ? p[id].rt : q);
+            p[id].rt -= ex;
+            p[id].et = curt + ex;
+            curt = p[id].et;
+            p[id].tat = p[id].et - p[id].at;
+            p[id].wt = p[id].tat - p[id].bt;
+            if (p[id].rt == 0) {
+                avg_tat += p[id].tat;
+                avg_wt += p[id].wt;
+                jd++;
+            }
+        }
+        for (int i = 0; i < n; ++i) {
+            if (curt >= p[i].at) {
+                ready[qsz++] = i;
+                p[i].used = 1;
+            }
+        }
+
+        if (p[id].rt != 0) {
+            ready[qsz++] = id;
+        }
+
+        if (qsz == 0) {
+            for (int i = 0; i < n; ++i) {
+                if (p[i].used != 0) {
+                    ready[qsz++] = i;
+                    p[i].used = 1;
+                    curt = p[i].at;
+                    break;
+                }
+            }
+        }
+    }
+
+    qsort(p, n, sizeof(Process), proc_cmp_id);
+    for (int i = 0; i < n; ++i) {
+        printf("%d\t%d\t%d\t%d\t%d\t%d\n", p[i].id, p[i].at, p[i].bt, p[i].et, p[i].tat, p[i].wt);
+    }
+
+    avg_tat /= n;
+    avg_wt /= n;
+    printf("avg:\t\t\t\t%lg\t%lg\n", avg_tat, avg_wt);
+}

week06/ex3.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+gcc ex3.c -o ex3.out
+./ex3.out