本文概述

• C ++
• C
• Java
• Python 3
• C#

给定n个进程的突发时间, 任务是使用FCFS调度算法查找平均等待时间和平均周转时间。
最先进的调度算法是先进先出(FIFO), 也称为先来先服务(FCFS)。 FIFO只是按照进程到达就绪队列的顺序对其进行排队。
这样, 首先执行的进程将首先执行, 而下一个进程只有在前一个进程完全执行后才开始。
在这里, 我们考虑所有进程的到达时间为0。
如何使用程序在Round Robin中计算以下时间？

1. 完成时间：流程完成其执行的时间。
2. 周转时间：完成时间与到达时间之间的时间差。周转时间=完成时间–到达时间
3. 等待时间(W.T)：转向时间和突发时间之间的时间差。
   等待时间=周转时间–爆发时间

在这篇文章中, 我们假设到达时间为0, 因此转身和完成时间相同。

文章图片
实现

1-Input the processes along with their burst time (bt). 2-Find waiting time (wt) for all processes. 3-As first process that comes need not to wait so waiting time for process 1 will be 0 i.e. wt[0] = 0. 4-Find waiting time for all other processes i.e. for process i -> wt[i] = bt[i-1] + wt[i-1] . 5-Find turnaround time = waiting_time + burst_time for all processes. 6-Find average waiting time = total_waiting_time / no_of_processes. 7-Similarly, find average turnaround time = total_turn_around_time / no_of_processes.

C ++

// C++ program for implementation of FCFS // scheduling #include< iostream> using namespace std; // Function to find the waiting time for all // processes void findWaitingTime( int processes[], int n, int bt[], int wt[]) { // waiting time for first process is 0 wt[0] = 0; // calculating waiting time for ( inti = 1; i < n ; i++ ) wt[i] =bt[i-1] + wt[i-1] ; }// Function to calculate turn around time void findTurnAroundTime( int processes[], int n, int bt[], int wt[], int tat[]) { // calculating turnaround time by adding // bt[i] + wt[i] for ( inti = 0; i < n ; i++) tat[i] = bt[i] + wt[i]; }//Function to calculate average time void findavgTime( int processes[], int n, int bt[]) { int wt[n], tat[n], total_wt = 0, total_tat = 0; //Function to find waiting time of all processes findWaitingTime(processes, n, bt, wt); //Function to find turn around time for all processes findTurnAroundTime(processes, n, bt, wt, tat); //Display processes along with all details cout < < "Processes" < < " Burst time" < < " Waiting time" < < " Turn around time\n" ; // Calculate total waiting time and total turn // around time for ( inti=0; i< n; i++) { total_wt = total_wt + wt[i]; total_tat = total_tat + tat[i]; cout < < "" < < i+1 < < "\t\t" < < bt[i] < < "\t" < < wt[i] < < "\t\t" < < tat[i] < < endl; }cout < < "Average waiting time = " < < ( float )total_wt / ( float )n; cout < < "\nAverage turn around time = " < < ( float )total_tat / ( float )n; }// Driver code int main() { //process id's int processes[] = { 1, 2, 3}; int n = sizeof processes / sizeof processes[0]; //Burst time of all processes intburst_time[] = {10, 5, 8}; findavgTime(processes, n, burst_time); return 0; }

C

// C program for implementation of FCFS // scheduling #include< stdio.h> // Function to find the waiting time for all // processes void findWaitingTime( int processes[], int n, int bt[], int wt[]) { // waiting time for first process is 0 wt[0] = 0; // calculating waiting time for ( inti = 1; i < n ; i++ ) wt[i] =bt[i-1] + wt[i-1] ; } // Function to calculate turn around time void findTurnAroundTime( int processes[], int n, int bt[], int wt[], int tat[]) { // calculating turnaround time by adding // bt[i] + wt[i] for ( inti = 0; i < n ; i++) tat[i] = bt[i] + wt[i]; } //Function to calculate average time void findavgTime( int processes[], int n, int bt[]) { int wt[n], tat[n], total_wt = 0, total_tat = 0; //Function to find waiting time of all processes findWaitingTime(processes, n, bt, wt); //Function to find turn around time for all processes findTurnAroundTime(processes, n, bt, wt, tat); //Display processes along with all details printf ( "ProcessesBurst timeWaiting timeTurn around time\n" ); // Calculate total waiting time and total turn // around time for ( inti=0; i< n; i++) { total_wt = total_wt + wt[i]; total_tat = total_tat + tat[i]; printf ( "%d " , (i+1)); printf ( "%d " , bt[i] ); printf ( "%d" , wt[i] ); printf ( "%d\n" , tat[i] ); } int s=( float )total_wt / ( float )n; int t=( float )total_tat / ( float )n; printf ( "Average waiting time = %d" , s); printf ( "\n" ); printf ( "Average turn around time = %d " , t); } // Driver code int main() { //process id's int processes[] = { 1, 2, 3}; int n = sizeof processes / sizeof processes[0]; //Burst time of all processes intburst_time[] = {10, 5, 8}; findavgTime(processes, n, burst_time); return 0; } // This code is contributed by Shivi_Aggarwal

Java

// Java program for implementation of FCFS // scheduling import java.text.ParseException; class GFG {// Function to find the waiting time for all // processes static void findWaitingTime( int processes[], int n, int bt[], int wt[]) { // waiting time for first process is 0 wt[ 0 ] = 0 ; // calculating waiting time for ( int i = 1 ; i < n; i++) { wt[i] = bt[i - 1 ] + wt[i - 1 ]; } }// Function to calculate turn around time static void findTurnAroundTime( int processes[], int n, int bt[], int wt[], int tat[]) { // calculating turnaround time by adding // bt[i] + wt[i] for ( int i = 0 ; i < n; i++) { tat[i] = bt[i] + wt[i]; } }//Function to calculate average time static void findavgTime( int processes[], int n, int bt[]) { int wt[] = new int [n], tat[] = new int [n]; int total_wt = 0 , total_tat = 0 ; //Function to find waiting time of all processes findWaitingTime(processes, n, bt, wt); //Function to find turn around time for all processes findTurnAroundTime(processes, n, bt, wt, tat); //Display processes along with all details System.out.printf( "Processes 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.printf( " %d " , (i + 1 )); System.out.printf( "%d " , bt[i]); System.out.printf( "%d" , wt[i]); System.out.printf( "%d\n" , tat[i]); } float s = ( float )total_wt /( float ) n; int t = total_tat / n; System.out.printf( "Average waiting time = %f" , s); System.out.printf( "\n" ); System.out.printf( "Average turn around time = %d " , t); }// Driver code public static void main(String[] args) throws ParseException { //process id's int processes[] = { 1 , 2 , 3 }; int n = processes.length; //Burst time of all processes int burst_time[] = { 10 , 5 , 8 }; findavgTime(processes, n, burst_time); } } // This code is contributed by 29ajaykumar

Python 3

# Python3 program for implementation # of FCFS scheduling# Function to find the waiting # time for all processes def findWaitingTime(processes, n, bt, wt):# waiting time for # first process is 0 wt[ 0 ] = 0# calculating waiting time for i in range ( 1 , n ): wt[i] = bt[i - 1 ] + wt[i - 1 ] # Function to calculate turn # around time def findTurnAroundTime(processes, n, bt, wt, tat):# calculating turnaround # time by adding bt[i] + wt[i] for i in range (n): tat[i] = bt[i] + wt[i]# Function to calculate # average time def findavgTime( processes, n, bt):wt = [ 0 ] * n tat = [ 0 ] * n total_wt = 0 total_tat = 0# Function to find waiting # time of all processes findWaitingTime(processes, n, bt, wt)# Function to find turn around # time for all processes findTurnAroundTime(processes, n, bt, wt, tat)# Display processes along # with all details print ( "Processes Burst time " + " Waiting time " + " Turn around time" )# Calculate total waiting time # and total turn around time for i in range (n):total_wt = total_wt + wt[i] total_tat = total_tat + tat[i] print ( " " + str (i + 1 ) + "\t\t" + str (bt[i]) + "\t " + str (wt[i]) + "\t\t " + str (tat[i])) print ( "Average waiting time = " + str (total_wt / n)) print ( "Average turn around time = " + str (total_tat / n))# Driver code if __name__ = = "__main__" :# process id's processes = [ 1 , 2 , 3 ] n = len (processes)# Burst time of all processes burst_time = [ 10 , 5 , 8 ]findavgTime(processes, n, burst_time)# This code is contributed # by ChitraNayal

C#

// C# program for implementation of FCFS // scheduling using System; class GFG {// Function to find the waiting time for all // processes static void findWaitingTime( int []processes, int n, int []bt, int [] wt) { // waiting time for first process is 0 wt[0] = 0; // calculating waiting time for ( int i = 1; i < n; i++) { wt[i] = bt[i - 1] + wt[i - 1]; } }// Function to calculate turn around time static void findTurnAroundTime( int []processes, int n, int []bt, int []wt, int []tat) { // calculating turnaround time by adding // bt[i] + wt[i] for ( int i = 0; i < n; i++) { tat[i] = bt[i] + wt[i]; } }// Function to calculate average time static void findavgTime( int []processes, int n, int []bt) { int []wt = new int [n]; int []tat = new int [n]; int total_wt = 0, total_tat = 0; //Function to find waiting time of all processes findWaitingTime(processes, n, bt, wt); //Function to find turn around time for all processes findTurnAroundTime(processes, n, bt, wt, tat); //Display processes along with all details Console.Write( "Processes 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]; Console.Write( " {0} " , (i + 1)); Console.Write( "{0} " , bt[i]); Console.Write( "{0}" , wt[i]); Console.Write( "{0}\n" , tat[i]); } float s = ( float )total_wt /( float ) n; int t = total_tat / n; Console.Write( "Average waiting time = {0}" , s); Console.Write( "\n" ); Console.Write( "Average turn around time = {0} " , t); }// Driver code public static void Main(String[] args) { // process id's int []processes = {1, 2, 3}; int n = processes.Length; // Burst time of all processes int []burst_time = {10, 5, 8}; findavgTime(processes, n, burst_time); } }// This code contributed by Rajput-Ji

输出如下：

ProcessesBurst timeWaiting timeTurn around time 110010 251015 381523 Average waiting time = 8.33333 Average turn around time = 16

重要事项：
非抢先平均等待时间不是最佳的
无法并行利用资源：产生Convoy效果(考虑存在许多IO绑定进程和一个CPU绑定进程的情况。当CPU绑定进程获取CPU时, IO绑定进程必须等待CPU绑定进程。IO绑定进程可能会最好将CPU占用一段时间, 然后再使用IO设备)。
资源 ：
http://web.cse.ohio-state.edu/~agrawal/660/Slides/jan18.pdf
在S2中我们将讨论到达时间不同的过程。
【FCFS CPU调度算法程序实现|S1】如果发现任何不正确的地方, 或者想分享有关上述主题的更多信息, 请写评论。

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