priority_scheduling.c

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

//#define INT_MAX 2147483647

typedef struct job{
    int id;
    int at;
    int bt;
    int st;
    int ct;
    int wt;
    int tat;
    int pr;
} job;

void sortJobsAT(job jobs[], int n){
    int i, j;
    job t;
    for(i = 0; i < n-1; i++){
        for(j = i+1; j < n; j++){
            if (jobs[i].at > jobs[j].at){
                t = jobs[i];
                jobs[i] = jobs[j];
                jobs[j] = t;
            }
        }
    }
}

void calc(job jobs[], int n){
    int *rt = (int*)malloc(sizeof(int)*n);
    int i, j;
    for(i = 0; i < n; i++){
        rt[i] = jobs[i].bt;
    }

    int complete = 0, t = 0, minm = INT_MAX;
    int mostImportant = 0, finish_time;
    bool check = false;

    while (complete != n){
        for(j = 0; j < n; j++){
            if ((jobs[j].at > t) || ((rt[j] == 0))){
               continue;
            }
            if (jobs[j].pr < minm){
                minm = jobs[j].pr;
                mostImportant = j;
                check = true;
            }
        }

        if (check == false){
            t++;
            continue; //no process in ready queue
        }

        //printf("\nt=%d, Process %d", t, mostImportant);

        if (rt[mostImportant] == jobs[mostImportant].bt){
            jobs[mostImportant].st = t;
        }

        rt[mostImportant]--;

        if (rt[mostImportant] == 0){
            complete++;
            check = false;
            minm = INT_MAX;

            jobs[mostImportant].ct = t+1;
            jobs[mostImportant].wt = jobs[mostImportant].ct - jobs[mostImportant].bt - jobs[mostImportant].at;

            jobs[mostImportant].wt = (jobs[mostImportant].wt < 0 ) ? 0 : jobs[mostImportant].wt;

            jobs[mostImportant].tat = jobs[mostImportant].ct - jobs[mostImportant].at;
        }

        t++;
    }
}

void solve(){
    int k;
    printf("\n\tPriority Scheduling Algorithm\n");
    printf("\n1. Same Arrival time (0)");
    printf("\n2. Different Arrival Times\n>>");
    scanf("%d", &k);
    if (!(k == 1) && !(k == 2)){
        printf("\nINVALID");
        exit(0);
    }
    int n;
    printf("Enter number of processes: ");
    scanf("%d", &n);
    job *jobs;
    jobs = (job*)malloc(sizeof(job)*n);
    int i;
    for(i=0; i < n; i++){
        jobs[i].id = i;
        if (k != 1){
            printf("Enter Arrival Time of Process %d: ", i);
            scanf("%d", &jobs[i].at);
        }
        else{
            jobs[i].at = 0;
        }
        printf("Enter Burst Time of Process %d: ", i);
        scanf("%d", &jobs[i].bt);
        printf("Enter Priority of Process %d: ", i);
        scanf("%d", &jobs[i].pr);
        printf("\n");
    }

    sortJobsAT(jobs, n);
    calc(jobs, n);

    printf("\nID\tAT\tBT\tPR\tST\tCT\tWT\tTAT");
    for (i = 0; i < n; i++){

        printf("\n%d\t%d\t%d\t%d\t%d\t%d\t%d\t%d", jobs[i].id, jobs[i].at, jobs[i].bt, jobs[i].pr, jobs[i].st, jobs[i].ct, jobs[i].wt, jobs[i].tat);
    }

    float avgWT = 0;
    float avgTAT = 0;

    for(i = 0; i < n; i++){
        avgWT += jobs[i].wt;
        avgTAT += jobs[i].tat;
    }
    avgWT /= n;
    avgTAT /= n;
    printf("\nAverage Waiting Time = %f\nAverage Turnaround Time = %f", avgWT, avgTAT);
}


int main(){
    solve();
    return 0;
}