[OS] Added Scheduling Algorithms

Author: geekswaroop

Operating-Systems/Lab-03 Scheduling Algorithms/SRTF.c

@@ -0,0 +1,53 @@
+#include<stdio.h>
+int main()
+{
+    int at[100],bt[100],rt[100],endTime,i,smallest,flag=0,idle_time=0,context_switches=0;
+    int remain=0,n,time,sum_wait=0,sum_turnaround=0;
+    printf("Enter no of Processes : ");
+    scanf("%d",&n);
+    for(i=0;i<n;i++)
+    {
+        printf("Enter arrival time for Process P%d : ",i+1);
+        scanf("%d",&at[i]);
+        printf("Enter burst time for Process P%d : ",i+1);
+        scanf("%d",&bt[i]);
+        rt[i]=bt[i];
+    }
+    printf("\n\nProcess\t|Turnaround Time| Waiting Time\n\n");
+    rt[99]=10000;
+    int prev_smallest = 10000;
+    for(time=0;remain!=n;time++)
+    {   prev_smallest=smallest;
+        smallest=101;
+        flag=0;
+        for(i=0;i<n;i++)
+        {
+            if(at[i]<=time && rt[i]<rt[smallest] && rt[i]>0)
+            {   
+                flag++;
+                smallest=i;
+            }
+        }
+        if(flag==0)
+        {
+            idle_time++;
+        }
+        if(prev_smallest!=smallest)
+        {
+            context_switches++;
+        }
+        rt[smallest]--;
+        if(rt[smallest]==0)
+        {
+            remain++;
+            endTime=time+1;
+            printf("\nP[%d]\t|\t%d\t|\t%d",smallest+1,endTime-at[smallest],endTime-bt[smallest]-at[smallest]);
+            // sum_wait+=endTime-bt[smallest]-at[smallest];
+            // sum_turnaround+=endTime-at[smallest];
+        }
+    }
+    // printf("\n\nAverage waiting time = %f\n",sum_wait*1.0/n);
+    // printf("Average Turnaround time = %f",sum_turnaround*1.0/5);
+    printf("Idle Time: %d\n", idle_time);
+    return 0;
+}

Operating-Systems/Lab-03 Scheduling Algorithms/round_robin.cpp

@@ -0,0 +1,98 @@
+#include<bits/stdc++.h>
+#define pb push_back
+#define ll long long
+#define double long double
+#define pii pair<int,int>
+#define pll pair<ll,ll>
+#define f first
+#define s second
+#define int long long
+#define sz(x) (ll)(x.size())
+#define MAX 200005
+using namespace std;
+
+signed main(){
+  cout<<"enter number of process and quant\n";
+  int n,quant;
+  cin>>n>>quant;
+  pair<int,pair<int,int> > arr[n];
+  cout<<"Enter Arrival time and burst time\n";
+  for(int i=0;i<n;i++){
+    cin>>arr[i].f>>arr[i].s.f;
+    arr[i].s.s=i;
+  }
+  int burst_sort[n],arr_sort[n];
+  sort(arr,arr+n);
+  vector<pii> cur;
+  for(int i=0;i<n;i++){
+    burst_sort[arr[i].s.s]=arr[i].s.f;
+    arr_sort[arr[i].s.s]=arr[i].f;
+  }
+  int time_exec=0;
+  int done[n]={0};
+  int cnt=0;
+  int ans[n];
+  int tmp=0;
+  int cs=0;
+  int prev=-1;
+  vector<pii> cpu_idle;
+  for(int i=0;i<n;i++){
+    cur.pb(make_pair(arr[i].s.f,arr[i].s.s));
+    if(time_exec<arr[i].f){
+      cpu_idle.pb(make_pair(time_exec,arr[i].f));
+      time_exec=arr[i].f;
+    }
+    // if(i<n-1) cout<<time_exec<<" "<<arr[i+1].f<<" "<<"here\n";
+    while(i<n-1 and cnt!=cur.size() and arr[i+1].f>time_exec){
+      if(cur[tmp].f<=quant and cur[tmp].f!=0){
+        if(prev!=tmp) cs++,prev=tmp;
+        ans[cur[tmp].s]=time_exec+cur[tmp].f;
+        cur[tmp].f=0;
+        time_exec+=cur[tmp].f;
+        cnt++;
+        // cout<<"gandu\n";
+        tmp++;
+        if(tmp==cur.size() and time_exec<arr[i+1].f) tmp=0;
+        continue;
+      }
+      if(cur[tmp].f>0){
+        // cout<<"hesa\n";
+        if(prev!=tmp) cs++,prev=tmp;
+        time_exec+=quant;
+        cur[tmp].f-=quant;
+        tmp++;
+        if(tmp==cur.size() and time_exec<arr[i+1].f) tmp=0;
+      }
+    }
+  }
+  while(cnt!=n){
+    for(int i=tmp;i<n;i++){
+      if(cur[i].f>0 and cur[i].f<=quant){
+        if(prev!=i) cs++,prev=i;
+        time_exec+=cur[i].f;
+        ans[cur[i].s]=time_exec;
+        cur[i].f=0;
+        cnt++;
+      }
+      else if(cur[i].f>0){
+        if(prev!=i) cs++,prev=i;
+        time_exec+=quant;
+        cur[i].f-=quant;
+      }
+    }
+    tmp=0;
+  }
+  int wait_time[n],turn_around[n];
+  for(int i=0;i<n;i++){
+    turn_around[i]=ans[i]-arr_sort[i];
+    wait_time[i]=turn_around[i]-burst_sort[i];
+  }
+  for(int i=0;i<n;i++){
+    cout<<turn_around[i]<<" "<<wait_time[i]<<"\n";
+  }
+  cout<<"context_switches are "<<cs-1<<"\n";
+  cout<<"cpu idle time is\n";
+  for(int i=0;i<cpu_idle.size();i++){
+    cout<<cpu_idle[i].f<<" "<<cpu_idle[i].s<<"\n";
+  }
+}