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program.cpp
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program.cpp
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#include <bits/stdc++.h>
using namespace std;
struct Process
{
// Process and its attributes
public:
int process_id;
int burst_time;
int temp_burst_time;
int response_time;
int arrival_time;
int priority;
int out_time;
int in_time;
};
// Insert processes for execution in the ready queue
// queueSize defines the number of processes in execution depending on the currentTime variable
// currentTime keeps a record of the current CPU time.
void insert(Process Queue[], Process value, int* queue_size, int* current_time)
{
int start = *queue_size, i;
Queue[*queue_size] = value;
if (Queue[*queue_size].in_time == -1)
Queue[*queue_size].in_time = *current_time;
++(*queue_size);
// Reordering Queue[]
while (start != 0 && Queue[(start - 1) / 2].priority > Queue[start].priority)
{
Process temp = Queue[(start - 1) / 2];
Queue[(start - 1) / 2] = Queue[start];
Queue[start] = temp;
start = (start - 1) / 2;
}
}
// Reorder Queue[] after insertion of new processes
void order(Process Queue[], int* queue_size, int start)
{
int smallest = start;
int left = 2 * start + 1;
int right = 2 * start + 2;
if (left < *queue_size && Queue[left].priority < Queue[smallest].priority)
smallest = left;
if (right < *queue_size && Queue[right].priority < Queue[smallest].priority)
smallest = right;
// Reorderng the Queue
if (smallest != start)
{
Process temp = Queue[smallest];
Queue[smallest] = Queue[start];
Queue[start] = temp;
order(Queue, queue_size, smallest);
}
}
// Find highest priority process and reorder the Queue[] again
Process extractminimum(Process Queue[], int* queue_size, int* current_time) //
{
Process min = Queue[0];
if (min.response_time == -1)
min.response_time = *current_time - min.arrival_time;
--(*queue_size);
if (*queue_size >= 1)
{
Queue[0] = Queue[*queue_size];
order(Queue, queue_size, 0);
}
return min;
}
// Compares two intervals of processes according to arrival times
bool compare(Process p1, Process p2)
{
return (p1.arrival_time < p2.arrival_time);
}
// Execute the highest priority process from Queue[]
void scheduling(Process Queue[], Process array[], int n, int* queue_size, int* current_time)
{
if (queue_size == 0)
return;
Process min = extractminimum(Queue, queue_size, current_time);
min.out_time = *current_time + 1;
--min.burst_time;
cout << "Process ID = " << min.process_id << " Current Time = " << *current_time << '\n';
//Reinsert the unfinished process into the Queue[]
if (min.burst_time > 0)
{
insert(Queue, min, queue_size, current_time);
return;
}
for (int i = 0; i < n; i++)
{
if (array[i].process_id == min.process_id)
{
array[i] = min;
break;
}
}
}
// Manages the entire execution of the processes as they arrive in the CPU on the basis of their arrival time.
void Priority(Process array[], int n)
{
sort(array, array + n, compare);
int total_waiting_time = 0;
int total_burst_time = 0;
int total_turnaround_time = 0;
int inserted_process = 0;
int queue_size = 0;
int current_time = array[0].arrival_time;
int total_response_time = 0;
Process Queue[4 * n];
// Calculating the total burst time of the processes
for (int i = 0; i < n; i++)
{
total_burst_time += array[i].burst_time;
array[i].temp_burst_time = array[i].burst_time;
}
// Inserting the processes in Queue[] on the basis of arrival time
do{
if (inserted_process != n)
{
for (int i = 0; i < n; i++)
{
if (array[i].arrival_time == current_time)
{
++inserted_process;
array[i].in_time = -1;
array[i].response_time = -1;
insert(Queue, array[i], &queue_size, ¤t_time);
}
}
}
scheduling(Queue, array, n, &queue_size, ¤t_time);
++current_time;
if (queue_size == 0 && inserted_process == n)
break;
}while (1);
for (int i = 0; i < n; i++)
{
total_response_time += array[i].response_time;
total_waiting_time += (array[i].out_time - array[i].in_time - array[i].temp_burst_time);
total_burst_time += array[i].burst_time;
}
cout << "Average Waiting Time = " << (float)total_waiting_time / (float)n << '\n';
cout << "Average Response Time = " << (float)total_response_time / (float)n << '\n';
cout << "Average Turn Around Time = " << (float)(total_waiting_time + total_burst_time) / (float)n << '\n';
}
int main()
{
int n, priority, arrival_time, burst_time;
cout << "Enter no. of processes: ";
cin >> n;
Process process[n];
cout << '\n' << "Enter Priority, Arrival Time & Burst Time ";
for(int i = 0; i < n; i++)
{
cout << '\n' << "For Process ID " << i + 1 << "-->" << '\n';
cin >> priority >> arrival_time >> burst_time;
cout << '\n';
process[i].process_id = i + 1;
process[i].priority = priority;
process[i].arrival_time = arrival_time;
process[i].burst_time = burst_time;
}
Priority(process, n);
return 0;
}