Priority CPU Scheduling with different arrival time – Set 2

08 Dec, 2021
Prerequisite – Program for Priority Scheduling – Set 1Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems. Each process is assigned first arrival time (less arrival time process first) if two processes have same arrival time, then compare to priorities (highest process first). Also, if two processes have same priority then compare to process number (less process number first). This process is repeated while all process get executed.
Implementation – 
First input the processes with their arrival time, burst time and priority.First process will schedule, which have the lowest arrival time, if two or more processes will have lowest arrival time, then whoever has higher priority will schedule first.Now further processes will be schedule according to the arrival time and priority of the process. (Here we are assuming that lower the priority number having higher priority). If two process priority are same then sort according to process number.Note: In the question, They will clearly mention, which number will have higher priority and which number will have lower priority.Once all the processes have been arrived, we can schedule them based on their priority.
First input the processes with their arrival time, burst time and priority.
First process will schedule, which have the lowest arrival time, if two or more processes will have lowest arrival time, then whoever has higher priority will schedule first.
Now further processes will be schedule according to the arrival time and priority of the process. (Here we are assuming that lower the priority number having higher priority). If two process priority are same then sort according to process number.Note: In the question, They will clearly mention, which number will have higher priority and which number will have lower priority.
Once all the processes have been arrived, we can schedule them based on their priority.
Gantt Chart – 
Examples – 
Input :
process no-> 1 2 3 4 5 
arrival time-> 0 1 3 2 4
burst time-> 3 6 1 2 4
priority-> 3 4 9 7 8
Output :
Process_no   arrival_time   Burst_time   Complete_time    Turn_Around_Time       Waiting_Time
1             0               3                3                   3               0
2             1               6                9                   8               2 
3             3               1                16                  13              12
4             2               2                11                  9               7
5             4               4                15                  11              7
Average Waiting Time is : 5.6
Average Turn Around time is : 8.8 
C++
Java
Python3
// C++ implementation for Priority Scheduling with//Different Arrival Time priority scheduling/*1. sort the processes according to arrival time2. if arrival time is same the acc to priority3. apply fcfs*/ #include <bits/stdc++.h> using namespace std; #define totalprocess 5 // Making a struct to hold the given input struct process{int at,bt,pr,pno;}; process proc[50]; /*Writing comparator function to sort according to priority ifarrival time is same*/ bool comp(process a,process b){if(a.at == b.at){return a.pr<b.pr;}else{    return a.at<b.at;}} // Using FCFS Algorithm to find Waiting timevoid get_wt_time(int wt[]){// declaring service array that stores cumulative burst timeint service[50]; // Initialising initial elements of the arraysservice[0] = proc[0].at;wt[0]=0;  for(int i=1;i<totalprocess;i++){service[i]=proc[i-1].bt+service[i-1]; wt[i]=service[i]-proc[i].at; // If waiting time is negative, change it into zero         if(wt[i]<0)    {    wt[i]=0;    }} } void get_tat_time(int tat[],int wt[]){// Filling turnaroundtime array for(int i=0;i<totalprocess;i++){    tat[i]=proc[i].bt+wt[i];}     } void findgc(){//Declare waiting time and turnaround time arrayint wt[50],tat[50]; double wavg=0,tavg=0; // Function call to find waiting time arrayget_wt_time(wt);//Function call to find turnaround timeget_tat_time(tat,wt);     int stime[50],ctime[50]; stime[0] = proc[0].at;ctime[0]=stime[0]+tat[0]; // calculating starting and ending timefor(int i=1;i<totalprocess;i++)    {        stime[i]=ctime[i-1];        ctime[i]=stime[i]+tat[i]-wt[i];    }     cout<<"Process_no\tStart_time\tComplete_time\tTurn_Around_Time\tWaiting_Time"<<endl;         // display the process details     for(int i=0;i<totalprocess;i++)    {        wavg += wt[i];        tavg += tat[i];                 cout<<proc[i].pno<<"\t\t"<<            stime[i]<<"\t\t"<<ctime[i]<<"\t\t"<<            tat[i]<<"\t\t\t"<<wt[i]<<endl;    }             // display the average waiting time        //and average turn around time         cout<<"Average waiting time is : ";    cout<<wavg/(float)totalprocess<<endl;    cout<<"average turnaround time : ";    cout<<tavg/(float)totalprocess<<endl; } int main(){int arrivaltime[] = { 1, 2, 3, 4, 5 };int bursttime[] = { 3, 5, 1, 7, 4 };int priority[] = { 3, 4, 1, 7, 8 };     for(int i=0;i<totalprocess;i++){    proc[i].at=arrivaltime[i];    proc[i].bt=bursttime[i];    proc[i].pr=priority[i];    proc[i].pno=i+1;    }         //Using inbuilt sort function         sort(proc,proc+totalprocess,comp);         //Calling function findgc for finding Gantt Chart         findgc();     return 0;} // This code is contributed by Anukul Chand.
// Java implementation for Priority Scheduling with//Different Arrival Time priority schedulingimport java.util.*; /// Data Structureclass Process {    int at, bt, pri, pno;    Process(int pno, int at, int bt, int pri)    {        this.pno = pno;        this.pri = pri;        this.at = at;        this.bt = bt;    }} /// Gantt chart structureclass GChart {    // process number, start time, complete time,    // turn around time, waiting time    int pno, stime, ctime, wtime, ttime;} // user define comparative method (first arrival first serve,// if arrival time same then heigh priority first)class MyComparator implements Comparator {     public int compare(Object o1, Object o2)    {         Process p1 = (Process)o1;        Process p2 = (Process)o2;        if (p1.at < p2.at)            return (-1);         else if (p1.at == p2.at && p1.pri > p2.pri)            return (-1);         else            return (1);    }}  // class to find Gantt chartclass FindGantChart {    void findGc(LinkedList queue)    {         // initial time = 0        int time = 0;         // priority Queue sort data according        // to arrival time or priority (ready queue)        TreeSet prique = new TreeSet(new MyComparator());         // link list for store processes data        LinkedList result = new LinkedList();         // process in ready queue from new state queue        while (queue.size() > 0)            prique.add((Process)queue.removeFirst());         Iterator it = prique.iterator();         // time set to according to first process        time = ((Process)prique.first()).at;         // scheduling process        while (it.hasNext()) {             // dispatcher dispatch the            // process ready to running state            Process obj = (Process)it.next();             GChart gc1 = new GChart();            gc1.pno = obj.pno;            gc1.stime = time;            time += obj.bt;            gc1.ctime = time;            gc1.ttime = gc1.ctime - obj.at;            gc1.wtime = gc1.ttime - obj.bt;             /// store the exxtreted process            result.add(gc1);        }         // create object of output class and call method        new ResultOutput(result);    }}
# Python3 implementation for Priority Scheduling with# Different Arrival Time priority scheduling"""1. sort the processes according to arrival time   2. if arrival time is same the acc to priority   3. apply fcfs """  totalprocess = 5proc = []for i in range(5):    l = []    for j in range(4):        l.append(0)    proc.append(l) # Using FCFS Algorithm to find Waiting timedef get_wt_time( wt):     # declaring service array that stores    # cumulative burst time    service = [0] * 5     # Initialising initial elements    # of the arrays    service[0] = 0    wt[0] = 0     for i in range(1, totalprocess):        service[i] = proc[i - 1][1] + service[i - 1]        wt[i] = service[i] - proc[i][0] + 1         # If waiting time is negative,        # change it o zero        if(wt[i] < 0) :                wt[i] = 0         def get_tat_time(tat, wt):     # Filling turnaroundtime array    for i in range(totalprocess):        tat[i] = proc[i][1] + wt[i] def findgc():         # Declare waiting time and    # turnaround time array    wt = [0] * 5    tat = [0] * 5     wavg = 0    tavg = 0     # Function call to find waiting time array    get_wt_time(wt)         # Function call to find turnaround time    get_tat_time(tat, wt)     stime = [0] * 5    ctime = [0] * 5    stime[0] = 1    ctime[0] = stime[0] + tat[0]         # calculating starting and ending time    for i in range(1, totalprocess):        stime[i] = ctime[i - 1]        ctime[i] = stime[i] + tat[i] - wt[i]     print("Process_no\tStart_time\tComplete_time",               "\tTurn_Around_Time\tWaiting_Time")     # display the process details    for i in range(totalprocess):        wavg += wt[i]        tavg += tat[i]                 print(proc[i][3], "\t\t", stime[i],                         "\t\t", end = " ")        print(ctime[i], "\t\t", tat[i], "\t\t\t", wt[i])      # display the average waiting time    # and average turn around time    print("Average waiting time is : ", end = " ")    print(wavg / totalprocess)    print("average turnaround time : " , end = " ")    print(tavg / totalprocess) # Driver codeif __name__ =="__main__":    arrivaltime = [1, 2, 3, 4, 5]    bursttime = [3, 5, 1, 7, 4]    priority = [3, 4, 1, 7, 8]         for i in range(totalprocess):         proc[i][0] = arrivaltime[i]        proc[i][1] = bursttime[i]        proc[i][2] = priority[i]        proc[i][3] = i + 1         # Using inbuilt sort function    proc = sorted (proc, key = lambda x:x[2])    proc = sorted (proc)         # Calling function findgc for    # finding Gantt Chart    findgc() # This code is contributed by# Shubham Singh(SHUBHAMSINGH10)
Output: 
Process_no Start_time Complete_time Turn_Around_Time Waiting_Time
1           1           4              3              0 
2           5           10             8              3
3           4           5              2              1
4          10           17             13             6
5          17           21             16             12
Average Waiting Time is : 4.4 
Average Turn Around time is : 8.4
Time Complexity: O(N * logN), where N is the total number of processes. Auxiliary Space: O(N) 
This article is contributed by Amit Verma . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. 
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