优先CPU调度程序|设置 1
优先级调度是批处理系统中最常见的调度算法之一。每个进程都被分配了一个优先级。优先级最高的进程将首先执行，依此类推。
具有相同优先级的进程以先到先得的方式执行。可以根据内存要求、时间要求或任何其他资源要求来决定优先级。
执行 ：
1- First input the processes with their burst time
and priority.
2- Sort the processes, burst time and priority
according to the priority.
3- Now simply apply FCFS algorithm.
注意：优先级调度的一个主要问题是无限阻塞或饥饿。解决低优先级进程无限阻塞问题的一个解决方案是老化。老化是一种逐渐增加在系统中等待很长时间的进程的优先级的技术。
C++
// C++ program for implementation of FCFS
// scheduling
#include
using namespace std;
struct Process
{
int pid; // Process ID
int bt; // CPU Burst time required
int priority; // Priority of this process
};
// Function to sort the Process acc. to priority
bool comparison(Process a, Process b)
{
return (a.priority > b.priority);
}
// Function to find the waiting time for all
// processes
void findWaitingTime(Process proc[], int n,
int wt[])
{
// waiting time for first process is 0
wt[0] = 0;
// calculating waiting time
for (int i = 1; i < n ; i++ )
wt[i] = proc[i-1].bt + wt[i-1] ;
}
// Function to calculate turn around time
void findTurnAroundTime( Process proc[], int n,
int wt[], int tat[])
{
// calculating turnaround time by adding
// bt[i] + wt[i]
for (int i = 0; i < n ; i++)
tat[i] = proc[i].bt + wt[i];
}
//Function to calculate average time
void findavgTime(Process proc[], int n)
{
int wt[n], tat[n], total_wt = 0, total_tat = 0;
//Function to find waiting time of all processes
findWaitingTime(proc, n, wt);
//Function to find turn around time for all processes
findTurnAroundTime(proc, n, wt, tat);
//Display processes along with all details
cout << "\nProcesses "<< " Burst time "
<< " Waiting time " << " Turn around time\n";
// Calculate total waiting time and total turn
// around time
for (int i=0; i Java
// Java program for implementation of FCFS
// scheduling
import java.util.*;
class Process
{
int pid; // Process ID
int bt; // CPU Burst time required
int priority; // Priority of this process
Process(int pid, int bt, int priority)
{
this.pid = pid;
this.bt = bt;
this.priority = priority;
}
public int prior() {
return priority;
}
}
public class GFG
{
// Function to find the waiting time for all
// processes
public void findWaitingTime(Process proc[], int n,
int wt[])
{
// waiting time for first process is 0
wt[0] = 0;
// calculating waiting time
for (int i = 1; i < n ; i++ )
wt[i] = proc[i - 1].bt + wt[i - 1] ;
}
// Function to calculate turn around time
public void findTurnAroundTime( Process proc[], int n,
int wt[], int tat[])
{
// calculating turnaround time by adding
// bt[i] + wt[i]
for (int i = 0; i < n ; i++)
tat[i] = proc[i].bt + wt[i];
}
// Function to calculate average time
public void findavgTime(Process proc[], int n)
{
int wt[] = new int[n], tat[] = new int[n], total_wt = 0, total_tat = 0;
// Function to find waiting time of all processes
findWaitingTime(proc, n, wt);
// Function to find turn around time for all processes
findTurnAroundTime(proc, n, wt, tat);
// Display processes along with all details
System.out.print("\nProcesses Burst time Waiting time Turn around time\n");
// Calculate total waiting time and total turn
// around time
for (int i = 0; i < n; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
System.out.print(" " + proc[i].pid + "\t\t" + proc[i].bt + "\t " + wt[i] + "\t\t " + tat[i] + "\n");
}
System.out.print("\nAverage waiting time = "
+(float)total_wt / (float)n);
System.out.print("\nAverage turn around time = "+(float)total_tat / (float)n);
}
public void priorityScheduling(Process proc[], int n)
{
// Sort processes by priority
Arrays.sort(proc, new Comparator() {
@Override
public int compare(Process a, Process b) {
return b.prior() - a.prior();
}
});
System.out.print("Order in which processes gets executed \n");
for (int i = 0 ; i < n; i++)
System.out.print(proc[i].pid + " ") ;
findavgTime(proc, n);
}
// Driver code
public static void main(String[] args)
{
GFG ob=new GFG();
int n = 3;
Process proc[] = new Process[n];
proc[0] = new Process(1, 10, 2);
proc[1] = new Process(2, 5, 0);
proc[2] = new Process(3, 8, 1);
ob.priorityScheduling(proc, n);
}
}
// This code is contributed by rahulpatil07109. Python3
# Python3 program for implementation of
# Priority Scheduling
# Function to find the waiting time
# for all processes
def findWaitingTime(processes, n, wt):
wt[0] = 0
# calculating waiting time
for i in range(1, n):
wt[i] = processes[i - 1][1] + wt[i - 1]
# Function to calculate turn around time
def findTurnAroundTime(processes, n, wt, tat):
# Calculating turnaround time by
# adding bt[i] + wt[i]
for i in range(n):
tat[i] = processes[i][1] + wt[i]
# Function to calculate average waiting
# and turn-around times.
def findavgTime(processes, n):
wt = [0] * n
tat = [0] * n
# Function to find waiting time
# of all processes
findWaitingTime(processes, n, wt)
# Function to find turn around time
# for all processes
findTurnAroundTime(processes, n, wt, tat)
# Display processes along with all details
print("\nProcesses Burst Time Waiting",
"Time Turn-Around Time")
total_wt = 0
total_tat = 0
for i in range(n):
total_wt = total_wt + wt[i]
total_tat = total_tat + tat[i]
print(" ", processes[i][0], "\t\t",
processes[i][1], "\t\t",
wt[i], "\t\t", tat[i])
print("\nAverage waiting time = %.5f "%(total_wt /n))
print("Average turn around time = ", total_tat / n)
def priorityScheduling(proc, n):
# Sort processes by priority
proc = sorted(proc, key = lambda proc:proc[2],
reverse = True);
print("Order in which processes gets executed")
for i in proc:
print(i[0], end = " ")
findavgTime(proc, n)
# Driver code
if __name__ =="__main__":
# Process id's
proc = [[1, 10, 1],
[2, 5, 0],
[3, 8, 1]]
n = 3
priorityScheduling(proc, n)
# This code is contributed
# Shubham Singh(SHUBHAMSINGH10)输出：
Order in which processes gets executed
1 3 2
Processes Burst time Waiting time Turn around time
1 10 0 10
3 8 10 18
2 5 18 23
Average waiting time = 9.33333
Average turn around time = 17