# Operating System | Priority Scheduling with different arrival time – Set 2

Prerequisite – Program for Priority Scheduling – Set 1
Priority scheduling is a non-preemptive algorithm and one of the most common scheduling algorithms in batch systems. Each process is assigned first arrival time (less arrival time process first) if two processes have same arrival time, then compare to priorities (highest process first). Also, if two processes have same priority then compare to process number (less process number first). This process is repeated while all process get executed.

Implementation –

1. First input the processes with their arrival time, burst time and priority.
2. Sort the processes, according to arrival time if two process arrival time is same then sort according process priority if two process priority are same then sort according to process number.
3. Now simply apply FCFS algorithm. Gantt Chart – Examples –

```Input :
process no-> 1 2 3 4 5
arrival time-> 0 1 3 2 4
burst time-> 3 6 1 2 4
priority-> 3 4 9 7 8
Output :
Process_no Start_time Complete_time Trun_Around_Time Wating_Time
1          0           3            3           0
2          3           9            8           2
4          9           11           9           7
3          11          12           9           8
5          12          16           12          8
Average Wating Time is : 5.0
Average Trun Around time is : 8.2

```

## C++

 `// C++ implementation for Priority Scheduling with  ` `//Different Arrival Time priority scheduling ` `/*1. sort the processes according to arrival time  ` `2. if arrival time is same the acc to priority ` `3. apply fcfs ` `*/` ` `  `#include ` ` `  `using` `namespace` `std; ` ` `  `#define totalprocess 5 ` ` `  `// Making a struct to hold the given input  ` ` `  `struct` `process ` `{ ` `int` `at,bt,pr,pno; ` `}; ` ` `  `process proc; ` ` `  `/* ` `Writing comparator function to sort according to priority if  ` `arrival time is same  ` `*/` ` `  `bool` `comp(process a,process b) ` `{ ` `if``(a.at == b.at) ` `{ ` `return` `a.pr

## Java

 `// Java implementation for Priority Scheduling with  ` `//Different Arrival Time priority scheduling ` `import` `java.util.*; ` ` `  `/// Data Structure ` `class` `Process { ` `    ``int` `at, bt, pri, pno; ` `    ``Process(``int` `pno, ``int` `at, ``int` `bt, ``int` `pri) ` `    ``{ ` `        ``this``.pno = pno; ` `        ``this``.pri = pri; ` `        ``this``.at = at; ` `        ``this``.bt = bt; ` `    ``} ` `} ` ` `  `/// Gantt chart structure ` `class` `GChart { ` `    ``// process number, start time, complete time, ` `    ``// turn around time, waiting time ` `    ``int` `pno, stime, ctime, wtime, ttime; ` `} ` ` `  `// user define comparative method (first arrival first serve, ` `// if arrival time same then heigh priority first) ` `class` `MyComparator ``implements` `Comparator { ` ` `  `    ``public` `int` `compare(Object o1, Object o2) ` `    ``{ ` ` `  `        ``Process p1 = (Process)o1; ` `        ``Process p2 = (Process)o2; ` `        ``if` `(p1.at < p2.at) ` `            ``return` `(-``1``); ` ` `  `        ``else` `if` `(p1.at == p2.at && p1.pri > p2.pri) ` `            ``return` `(-``1``); ` ` `  `        ``else` `            ``return` `(``1``); ` `    ``} ` `} ` ` `  ` `  `// class to find Gantt chart ` `class` `FindGantChart { ` `    ``void` `findGc(LinkedList queue) ` `    ``{ ` ` `  `        ``// initial time = 0 ` `        ``int` `time = ``0``; ` ` `  `        ``// priority Queue sort data according ` `        ``// to arrival time or priority (ready queue) ` `        ``TreeSet prique = ``new` `TreeSet(``new` `MyComparator()); ` ` `  `        ``// link list for store processes data ` `        ``LinkedList result = ``new` `LinkedList(); ` ` `  `        ``// process in ready queue from new state queue ` `        ``while` `(queue.size() > ``0``) ` `            ``prique.add((Process)queue.removeFirst()); ` ` `  `        ``Iterator it = prique.iterator(); ` ` `  `        ``// time set to according to first process ` `        ``time = ((Process)prique.first()).at; ` ` `  `        ``// scheduling process ` `        ``while` `(it.hasNext()) { ` ` `  `            ``// dispatcher dispatch the ` `            ``// process ready to running state ` `            ``Process obj = (Process)it.next(); ` ` `  `            ``GChart gc1 = ``new` `GChart(); ` `            ``gc1.pno = obj.pno; ` `            ``gc1.stime = time; ` `            ``time += obj.bt; ` `            ``gc1.ctime = time; ` `            ``gc1.ttime = gc1.ctime - obj.at; ` `            ``gc1.wtime = gc1.ttime - obj.bt; ` ` `  `            ``/// store the exxtreted process ` `            ``result.add(gc1); ` `        ``} ` ` `  `        ``// create object of output class and call method ` `        ``new` `ResultOutput(result); ` `    ``} ` `} `

## Python3

# Python3 implementation for Priority Scheduling with
# Different Arrival Time priority scheduling
“””1. sort the processes according to arrival time
2. if arrival time is same the acc to priority
3. apply fcfs “””

totalprocess = 5
proc = []
for i in range(5):
l = []
for j in range(4):
l.append(0)
proc.append(l)

# Using FCFS Algorithm to find Waiting time
def get_wt_time( wt):

# declaring service array that stores
# cumulative burst time
service =  * 5

# Initilising initial elements
# of the arrays
service = 0
wt = 0

for i in range(1, totalprocess):
service[i] = proc[i – 1] + service[i – 1]
wt[i] = service[i] – proc[i] + 1

# If waiting time is negative,
# change it o zero
if(wt[i] < 0) : wt[i] = 0 def get_tat_time(tat, wt): # Filling turnaroundtime array for i in range(totalprocess): tat[i] = proc[i] + wt[i] def findgc(): # Declare waiting time and # turnaround time array wt =  * 5 tat =  * 5 wavg = 0 tavg = 0 # Function call to find waiting time array get_wt_time(wt) # Function call to find turnaround time get_tat_time(tat, wt) stime =  * 5 ctime =  * 5 stime = 1 ctime = stime + tat # calculating starting and ending time for i in range(1, totalprocess): stime[i] = ctime[i - 1] ctime[i] = stime[i] + tat[i] - wt[i] print("Process_no Start_time Complete_time", " Turn_Around_Time Waiting_Time") # display the process details for i in range(totalprocess): wavg += wt[i] tavg += tat[i] print(proc[i], " ", stime[i], " ", end = " ") print(ctime[i], " ", tat[i], " ", wt[i]) # display the average waiting time # and average turn around time print("Average waiting time is : ", end = " ") print(wavg / totalprocess) print("average turnaround time : " , end = " ") print(tavg / totalprocess) # Driver code if __name__ =="__main__": arrivaltime = [1, 2, 3, 4, 5] bursttime = [3, 5, 1, 7, 4] priority = [3, 4, 1, 7, 8] for i in range(totalprocess): proc[i] = arrivaltime[i] proc[i] = bursttime[i] proc[i] = priority[i] proc[i] = i + 1 # Using inbuilt sort function proc = sorted (proc, key = lambda x:x) proc = sorted (proc) # Calling function findgc for # finding Gantt Chart findgc() # This code is contributed by # Shubham Singh(SHUBHAMSINGH10) [tabbyending] Output:

```Process_no Start_time Complete_time Trun_Around_Time Wating_Time
1           1           4              3            0
2           4           9              7            2
3           9           10             7            6
4          10           17             13           6
5          17           21             16           12
Average Wating Time is : 5.2
Average Trun Around time is : 9.2
```