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Shailrshah

Highest Response Ratio Next

Sep 14th, 2014
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C 3.27 KB | None | 0 0
  1. #include <stdio.h>
  2. #define N 9
  3. struct process{
  4.     char pid;
  5.     int at;
  6.     int et;
  7.     float pri;
  8.     int rem;
  9.     int done;
  10.     int ct;
  11.     int wt;
  12.     int tt;
  13. }pro[N] =   { //{'pid', at, et},
  14.                 {'A', 0, 10},
  15.                 {'B', 0, 5},
  16.                 {'C', 0, 2},
  17.                 {'D', 0, 4},
  18.                 {'E', 10, 8},
  19.                 {'F', 10, 16},
  20.                 {'G', 10, 6},
  21.                 {'H', 20, 3},
  22.                 {'I', 20, 1}
  23.             };
  24. void init(){ //initially, all processes are unfinished and their remaining and execution times are same.
  25.     int i;
  26.     for(i=0; i< N; i++){
  27.         pro[i].done=0;
  28.         pro[i].rem=pro[i].et;
  29.     }
  30. }
  31. int nextProc(int time){
  32.     int i, send=0;
  33.     for(i = 0; i < N; i++)
  34.         if(pro[i].done==0) break; //find first process that's not completed.
  35.     if(i==N) return -1;
  36.     send=i; //send will be returned at the end of function
  37.     for(; i < N; i++){
  38.         if(pro[i].done || pro[i].at > time) continue; //if the process is completed, skip it
  39.         if(time==0||time==10||time==20)
  40.                 pro[i].pri=((float)(time-pro[i].at)/(float)pro[i].rem)+1; //calculated at t=0,10,20...
  41.         if (pro[i].pri > pro[send].pri) send = i; //process with highest response time will be returned
  42.         else if(pro[i].pri == pro[send].pri && pro[i].et < pro[send].et) send = i; //compare execution time
  43.         else if(pro[i].et == pro[send].et && pro[i].at < pro[send].at) send = i; //compare arrival times
  44.         else if(pro[i].at == pro[send].at && pro[i].pid < pro[send].pid) send = i; //compare pids
  45.     }
  46.     if(time==0||time==10||time==20){
  47.         printf("\n\nAt t=%d, the processes already arrived but not completed are:-\n", time);
  48.             for(i=0; i < N; i++)
  49.                 if(pro[i].done || pro[i].at > time) continue;
  50.                 else printf("%c(Pri: %.3f)",pro[i].pid, pro[i].pri);
  51.         printf("\n\n");
  52.     }
  53.     return send;
  54. }
  55. void printResult(int sumWT, int sumTT){
  56.     int i;
  57.     printf("\tpid\tAT\tET\tCT\tWT\tTT\n");
  58.     for(i = 0; i < N; i++) printf("\t%c\t%d\t%d\t%d\t%d\t%d\n", pro[i].pid, pro[i].at, pro[i].et, pro[i].ct, pro[i].wt, pro[i].tt);
  59.     printf("\nThe average waiting time is %.2f\nThe average turn around time is %.2f\n", sumWT/(float)N, sumTT/(float)N);
  60. }
  61. int main(){
  62.     int i, time = 0, sumWT = 0, sumTT = 0,  curr;
  63.     init();
  64.     while(1){
  65.         curr = nextProc(time); //process to be executed
  66.         if(curr == -1) break; //if all processes have completed, print the result
  67.         printf("At time=%d, %c gets CPU.(RR: %.3f, remaining: %d)\n", time, pro[curr].pid, pro[curr].pri, pro[curr].rem);
  68.         pro[curr].rem--; //subtract one time unit from the process's remaining time
  69.         time++;
  70.         if(pro[curr].rem == 0){
  71.             pro[curr].done=1; //if remaining time is 0, the process is completed.
  72.             pro[curr].ct = time; //completed time is the time when process execution is completed
  73.             pro[curr].tt = pro[curr].ct - pro[curr].at;
  74.             pro[curr].wt = pro[curr].tt - pro[curr].et;
  75.             printf("\n%c has finished executing at %d\n\n", pro[curr].pid, time);
  76.             sumWT += pro[curr].wt;
  77.             sumTT += pro[curr].tt;
  78.         }
  79.     }
  80.     printResult(sumWT, sumTT);
  81.     return 0;
  82. }
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