Round Robin Scheduling: Round Robin Scheduling

Round Robin Scheduling: Round Robin Scheduling: Round-robin job scheduling may not be desirable if the sizes of the jobs or tasks are highly variable. A process that produces large jobs w...

Round Robin Scheduling

Round-robin job scheduling may not be desirable if the sizes of the jobs or tasks are highly variable. A process that produces large jobs would be favoured over other processes. This problem may be solved by time-sharing, i.e. by giving each job a time slot or quantum(its allowance of CPU time), and interrupt the job if it is not completed by then. The job is resumed next time a time slot is assigned to that process.

Sample Implementation source code (C)

#include<stdio.h>

struct process

{

int pid,etime,ftime,hasfin,hasstr,wtime;

}pr[20];

int main()

{

int i,j,timeslice,temp,count=0,tclock=0,limit;

printf("Enter the time slice  :  ");

scanf("%d",&timeslice);

printf("Enter the number of process : ");

scanf("%d",&limit);

for(i=0;i<limit;i++)

{

printf("Enter the execution time of P%d  :  ",i);

scanf("%d",&pr[i].etime);

pr[i].hasfin=0;

pr[i].hasstr=0;

pr[i].pid=i+1;

}

printf("Process number     Time Elapsed  ");

i=0;

do

{

temp=timeslice;

do

{

count=0;

if(pr[i].hasstr == 0) 

{

pr[i].hasstr=1;

pr[i].wtime=tclock;

}

if(pr[i].hasfin == 0 )

{

tclock++;

temp--;

pr[i].etime-=1;

if(pr[i].hasfin == 0 && pr[i].etime == 0)

pr[i].ftime=tclock;

}

if(pr[i].etime == 0) 

{

pr[i].hasfin =1;

break;

}

}while(temp !=0);

for(j=0;j<limit;j++)

{

if(pr[j].hasfin == 0)

printf("\n P%d\t\t\t%d",pr[j].pid,pr[j].etime);

}

i++;

while(pr[i].etime == 0 && i <= limit)

i=i+1;

if(i >= limit)

{

i=0;

while(pr[i].etime == 0 && i <= limit)

i=i+1;

}

for(j=0;j<limit;j++)

{

if(pr[j].etime ==0 )

count=count+1;

}

}while(count < limit);

printf("\n\nProcess Id \tWait Time \tTurn Around Time ");

for(j=0;j<limit;j++)

printf("\nP%d\t\t       %d \t\t  %d",pr[j].pid,pr[j].wtime,pr[j].ftime);

return 0;

}