Question

PROGRAMMING LANGUAGE : JAVA

• Problem specification.

In this assignment, you will create a simulation for a CPU scheduler. The number of CPU’s and the list of processes and their info will be read from a text file. The output, of your simulator will display the execution of the processes on the different available CPU’s. The simulator should also display:

-   The given info of each process

-   CPU utilization

- The average wait time

- Turnaround time for each process

- CPU response time for each process

• Implementation.

You need to start your demo with a UML diagram.

You need to implement the following algorithms:

• FCFS (First Come First Served)
• SJF (Shortest Job
• SRTF (Shortest Remaining Time First)
• RR with a user given queue

• Sample input file (text file contents)

numOfCPUs:      4

// list of processes to be scheduled

// processID       arrivalTime          totalExecTime   IO_RequestAtTime         IO_RequestAtTime ...

p0           0              10           2              5              8

p1           2              3

p2           10           7              1              2              3

- Further Details

The first line indicates how many CPU’s/cores do we have in the system. This sample file indicates that we have 4 CPU’s/cores

Any line that starts with // is a comment

Then we have a list of the processes. The first line:

p0           0              10           2              5              8

means we have process with process ID p0 that arrives at time 0. It needs 10 time on the CPU to finish executing its code. 2 time units after it has started, it asks for I/O. Any I/O request is fulfilled in 2 time units. At time 5 of its execution, p0 asks for I/O again. At time 8 of its execution, it asks for I/O again. There is no limit for how many times a process asks for I/O.

p1 does not ask for any I/O.

p2 arrives at time 10. 1 time unit after it stared execution, it requests I/O.

Answer 1

fcfs:

import java.util.*;

public class FCFS {

public static void main(String args[])

{

Scanner sc = new Scanner(System.in);

System.out.println("enter no of process: ");

int n = sc.nextInt();

int pid[] = new int[n];   // process ids

int ar[] = new int[n];     // arrival times

int bt[] = new int[n];     // burst or execution times

int ct[] = new int[n];     // completion times

int ta[] = new int[n];     // turn around times

int wt[] = new int[n];     // waiting times

int temp;

float avgwt=0,avgta=0;

for(int i = 0; i < n; i++)

{

System.out.println("enter process " + (i+1) + " arrival time: ");

ar[i] = sc.nextInt();

System.out.println("enter process " + (i+1) + " brust time: ");

bt[i] = sc.nextInt();

pid[i] = i+1;

}

//sorting according to arrival times

for(int i = 0 ; i <n; i++)

{

for(int  j=0;  j < n-(i+1) ; j++)

{

if( ar[j] > ar[j+1] )

{

temp = ar[j];

ar[j] = ar[j+1];

ar[j+1] = temp;

temp = bt[j];

bt[j] = bt[j+1];

bt[j+1] = temp;

temp = pid[j];

pid[j] = pid[j+1];

pid[j+1] = temp;

}

}

}

// finding completion times

for(int  i = 0 ; i < n; i++)

{

if( i == 0)

{

ct[i] = ar[i] + bt[i];

}

else

{

if( ar[i] > ct[i-1])

{

ct[i] = ar[i] + bt[i];

}

else

ct[i] = ct[i-1] + bt[i];

}

ta[i] = ct[i] - ar[i] ;          // turnaround time= completion time- arrival time

wt[i] = ta[i] - bt[i] ;          // waiting time= turnaround time- burst time

avgwt += wt[i] ;               // total waiting time

avgta += ta[i] ;               // total turnaround time

}

System.out.println("\npid  arrival  brust  complete turn waiting");

for(int  i = 0 ; i< n;  i++)

{

System.out.println(pid[i] + "  \t " + ar[i] + "\t" + bt[i] + "\t" + ct[i] + "\t" + ta[i] + "\t"  + wt[i] ) ;

}

sc.close();

System.out.println("\naverage waiting time: "+ (avgwt/n));     // printing average waiting time.

System.out.println("average turnaround time:"+(avgta/n));    // printing average turnaround time.

}

}

sjf:

import java.util.*; public class SJF { public static void main(String args[]) { Scanner sc = new Scanner(System.in); System.out.println ("enter no of process:"); int n = sc.nextInt(); int pid[] = new int[n]; int at[] = new int[n]; // at means arrival time int bt[] = new int[n]; // bt means burst time int ct[] = new int[n]; // ct means complete time int ta[] = new int[n]; // ta means turn around time int wt[] = new int[n];  //wt means waiting time int f[] = new int[n];  // f means it is flag it checks process is completed or not int st=0, tot=0; float avgwt=0, avgta=0; for(int i=0;i<n;i++) { System.out.println ("enter process " + (i+1) + " arrival time:"); at[i] = sc.nextInt(); System.out.println ("enter process " + (i+1) + " brust time:"); bt[i] = sc.nextInt(); pid[i] = i+1; f[i] = 0; } boolean a = true; while(true) { int c=n, min=999; if (tot == n) // total no of process = completed process loop will be terminated break; for (int i=0; i<n; i++) { /* * If i'th process arrival time <= system time and its flag=0 and burst<min * That process will be executed first */ if ((at[i] <= st) && (f[i] == 0) && (bt[i]<min)) { min=bt[i]; c=i; } } /* If c==n means c value can not updated because no process arrival time< system time so we increase the system time */ if (c==n) st++; else { ct[c]=st+bt[c]; st+=bt[c]; ta[c]=ct[c]-at[c]; wt[c]=ta[c]-bt[c]; f[c]=1; tot++; } } System.out.println("\npid  arrival brust  complete turn waiting"); for(int i=0;i<n;i++) { avgwt+= wt[i]; avgta+= ta[i]; System.out.println(pid[i]+"\t"+at[i]+"\t"+bt[i]+"\t"+ct[i]+"\t"+ta[i]+"\t"+wt[i]); } System.out.println ("\naverage tat is "+ (float)(avgta/n)); System.out.println ("average wt is "+ (float)(avgwt/n)); sc.close(); } } srtf: import java.io.*; public class SRTF { public static void main(String args[]) throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); int n; System.out.println("Please enter the number of Processes: "); n = Integer.parseInt(br.readLine()); int proc[][] = new int[n + 1][4];//proc[][0] is the AT array,[][1] - RT,[][2] - WT,[][3] - TT for(int i = 1; i <= n; i++) { System.out.println("Please enter the Arrival Time for Process " + i + ": "); proc[i][0] = Integer.parseInt(br.readLine()); System.out.println("Please enter the Burst Time for Process " + i + ": "); proc[i][1] = Integer.parseInt(br.readLine()); } System.out.println(); //Calculation of Total Time and Initialization of Time Chart array int total_time = 0; for(int i = 1; i <= n; i++) { total_time += proc[i][1]; } int time_chart[] = new int[total_time]; for(int i = 0; i < total_time; i++) { //Selection of shortest process which has arrived int sel_proc = 0; int min = 99999; for(int j = 1; j <= n; j++) { if(proc[j][0] <= i)//Condition to check if Process has arrived { if(proc[j][1] < min && proc[j][1] != 0) { min = proc[j][1]; sel_proc = j; } } } //Assign selected process to current time in the Chart time_chart[i] = sel_proc; //Decrement Remaining Time of selected process by 1 since it has been assigned the CPU for 1 unit of time proc[sel_proc][1]--; //WT and TT Calculation for(int j = 1; j <= n; j++) { if(proc[j][0] <= i) { if(proc[j][1] != 0) { proc[j][3]++;//If process has arrived and it has not already completed execution its TT is incremented by 1 if(j != sel_proc)//If the process has not been currently assigned the CPU and has arrived its WT is incremented by 1 proc[j][2]++; } else if(j == sel_proc)//This is a special case in which the process has been assigned CPU and has completed its execution proc[j][3]++; } } //Printing the Time Chart if(i != 0) { if(sel_proc != time_chart[i - 1]) //If the CPU has been assigned to a different Process we need to print the current value of time and the name of //the new Process { System.out.print("--" + i + "--P" + sel_proc); } } else//If the current time is 0 i.e the printing has just started we need to print the name of the First selected Process System.out.print(i + "--P" + sel_proc); if(i == total_time - 1)//All the process names have been printed now we have to print the time at which execution ends System.out.print("--" + (i + 1)); } System.out.println(); System.out.println(); //Printing the WT and TT for each Process System.out.println("P\t WT \t TT "); for(int i = 1; i <= n; i++) { System.out.printf("%d\t%2dms\t%2dms",i,proc[i][2],proc[i][3]); System.out.println(); } System.out.println(); //Printing the average WT & TT float WT = 0,TT = 0; for(int i = 1; i <= n; i++) { WT += proc[i][2]; TT += proc[i][3]; } WT /= n; TT /= n; System.out.println("The Average WT is: " + WT + "ms"); System.out.println("The Average TT is: " + TT + "ms"); } } RR: // Java program for implementation of RR scheduling public class GFG {    // Method to find the waiting time for all    // processes    static void findWaitingTime(int processes[], int n,                int bt[], int wt[], int quantum)    {        // Make a copy of burst times bt[] to store remaining        // burst times.        int rem_bt[] = new int[n];        for (int i = 0 ; i < n ; i++)            rem_bt[i] = bt[i];           int t = 0; // Current time           // Keep traversing processes in round robin manner        // until all of them are not done.        while(true)        {            boolean done = true;               // Traverse all processes one by one repeatedly            for (int i = 0 ; i < n; i++)            {                // If burst time of a process is greater than 0                // then only need to process further                if (rem_bt[i] > 0)                {                    done = false; // There is a pending process                       if (rem_bt[i] > quantum)                    {                        // Increase the value of t i.e. shows                        // how much time a process has been processed                        t += quantum;                           // Decrease the burst_time of current process                        // by quantum                        rem_bt[i] -= quantum;                    }                       // If burst time is smaller than or equal to                    // quantum. Last cycle for this process                    else                    {                        // Increase the value of t i.e. shows                        // how much time a process has been processed                        t = t + rem_bt[i];                           // Waiting time is current time minus time                        // used by this process                        wt[i] = t - bt[i];                           // As the process gets fully executed                        // make its remaining burst time = 0                        rem_bt[i] = 0;                    }                }            }               // If all processes are done            if (done == true)            break;        }    }       // Method to calculate turn around time    static void findTurnAroundTime(int processes[], int n,                            int bt[], int wt[], int tat[])    {        // calculating turnaround time by adding        // bt[i] + wt[i]        for (int i = 0; i < n ; i++)            tat[i] = bt[i] + wt[i];    }       // Method to calculate average time    static void findavgTime(int processes[], int n, int bt[],                                        int quantum)    {        int wt[] = new int[n], tat[] = new int[n];        int total_wt = 0, total_tat = 0;           // Function to find waiting time of all processes        findWaitingTime(processes, n, bt, wt, quantum);           // Function to find turn around time for all processes        findTurnAroundTime(processes, n, bt, wt, tat);           // Display processes along with all details        System.out.println("Processes " + " Burst time " +                    " Waiting time " + " Turn around time");           // Calculate total waiting time and total turn        // around time        for (int i=0; i<n; i++)        {            total_wt = total_wt + wt[i];            total_tat = total_tat + tat[i];            System.out.println(" " + (i+1) + "\t\t" + bt[i] +"\t " +                            wt[i] +"\t\t " + tat[i]);        }           System.out.println("Average waiting time = " +                        (float)total_wt / (float)n);        System.out.println("Average turn around time = " +                        (float)total_tat / (float)n);    }       // Driver Method    public static void main(String[] args)    {        // process id's        int processes[] = { 1, 2, 3};        int n = processes.length;           // Burst time of all processes        int burst_time[] = {10, 5, 8};           // Time quantum        int quantum = 2;        findavgTime(processes, n, burst_time, quantum);    } }