算法设计：循环调度算法程序详细实现S1

2021年4月6日19:11:40 发表评论 1,322 次浏览

本文概述

轮循是一种CPU调度算法，它以循环的方式为每个进程分配一个固定的时隙。

  • 它简单, 易于实现且无饥饿, 因为所有进程都可以公平分配CPU。
  • 以CPU调度为核心的最常用技术之一。
  • 这是抢先的, 因为最多只在固定的时间段内为进程分配CPU。
  • 它的缺点是上下文切换的更多开销。
序列号。 优点 缺点
1. 这是公平的, 因为每个进程都获得相等的CPU份额。 等待时间和响应时间更长。
2. 新创建的进程将添加到就绪队列的末尾。 吞吐量低。
3. 循环调度程序通常使用分时, 为每个作业分配一个时隙或数量。 有上下文切换。
4. 在执行循环调度时, 会将特定的时间量分配给不同的作业。 甘特图似乎太大了(如果调度所需的量子时间较少, 例如：大调度需要1 ms。)
5. 在此调度中的特定量子时间之后, 每个进程都有机会重新调度。 小量子的费时调度。

插图：

轮循

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。

棘手的部分是计算等待时间。一旦计算出等待时间, 就可以快速计算周转时间。

查找所有进程的等待时间的步骤：

1- Create an array rem_bt[] to keep track of remaining
   burst time of processes. This array is initially a 
   copy of bt[] (burst times array)
2- Create another array wt[] to store waiting times
   of processes. Initialize this array as 0.
3- Initialize time : t = 0
4- Keep traversing the all processes while all processes
   are not done. Do following for i'th process if it is
   not done yet.
    a- If rem_bt[i] > quantum
       (i)  t = t + quantum
       (ii) bt_rem[i] -= quantum;
    c- Else // Last cycle for this process
       (i)  t = t + bt_rem[i];
       (ii) wt[i] = t - bt[i]
       (ii) bt_rem[i] = 0; // This process is over

一旦有了等待时间, 我们就可以将进程的周转时间tat [i]计算为等待时间和突发时间之和, 即w​​t [i] + bt [i]

以下是上述步骤的实现。

C/C++

// C++ program for implementation of RR 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[], int quantum)
{
     // Make a copy of burst times bt[] to store remaining
     // burst times.
     int rem_bt[n];
     for ( int i = 0 ; i < n ; i++)
         rem_bt[i] =  bt[i];
  
     int t = 0; // Current time
  
     // Keep traversing processes in round robin manner
     // until all of them are not done.
     while (1)
     {
         bool done = true ;
  
         // Traverse all processes one by one repeatedly
         for ( int i = 0 ; i < n; i++)
         {
             // If burst time of a process is greater than 0
             // then only need to process further
             if (rem_bt[i] > 0)
             {
                 done = false ; // There is a pending process
  
                 if (rem_bt[i] > quantum)
                 {
                     // Increase the value of t i.e. shows
                     // how much time a process has been processed
                     t += quantum;
  
                     // Decrease the burst_time of current process
                     // by quantum
                     rem_bt[i] -= quantum;
                 }
  
                 // If burst time is smaller than or equal to
                 // quantum. Last cycle for this process
                 else
                 {
                     // Increase the value of t i.e. shows
                     // how much time a process has been processed
                     t = t + rem_bt[i];
  
                     // Waiting time is current time minus time
                     // used by this process
                     wt[i] = t - bt[i];
  
                     // As the process gets fully executed
                     // make its remaining burst time = 0
                     rem_bt[i] = 0;
                 }
             }
         }
  
         // If all processes are done
         if (done == true )
           break ;
     }
}
  
// 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 ( int i = 0; i < n ; i++)
         tat[i] = bt[i] + wt[i];
}
  
// Function to calculate average time
void findavgTime( int processes[], int n, int bt[], int quantum)
{
     int wt[n], tat[n], total_wt = 0, total_tat = 0;
  
     // Function to find waiting time of all processes
     findWaitingTime(processes, n, bt, wt, quantum);
  
     // 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 ( int i=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
     int burst_time[] = {10, 5, 8};
  
     // Time quantum
     int quantum = 2;
     findavgTime(processes, n, burst_time, quantum);
     return 0;
}

Java

// Java program for implementation of RR scheduling
  
public class GFG 
{
     // Method to find the waiting time for all
     // processes
     static void findWaitingTime( int processes[], int n, int bt[], int wt[], int quantum)
     {
         // Make a copy of burst times bt[] to store remaining
         // burst times.
         int rem_bt[] = new int [n];
         for ( int i = 0 ; i < n ; i++)
             rem_bt[i] =  bt[i];
       
         int t = 0 ; // Current time
       
         // Keep traversing processes in round robin manner
         // until all of them are not done.
         while ( true )
         {
             boolean done = true ;
       
             // Traverse all processes one by one repeatedly
             for ( int i = 0 ; i < n; i++)
             {
                 // If burst time of a process is greater than 0
                 // then only need to process further
                 if (rem_bt[i] > 0 )
                 {
                     done = false ; // There is a pending process
       
                     if (rem_bt[i] > quantum)
                     {
                         // Increase the value of t i.e. shows
                         // how much time a process has been processed
                         t += quantum;
       
                         // Decrease the burst_time of current process
                         // by quantum
                         rem_bt[i] -= quantum;
                     }
       
                     // If burst time is smaller than or equal to
                     // quantum. Last cycle for this process
                     else
                     {
                         // Increase the value of t i.e. shows
                         // how much time a process has been processed
                         t = t + rem_bt[i];
       
                         // Waiting time is current time minus time
                         // used by this process
                         wt[i] = t - bt[i];
       
                         // As the process gets fully executed
                         // make its remaining burst time = 0
                         rem_bt[i] = 0 ;
                     }
                 }
             }
       
             // If all processes are done
             if (done == true )
               break ;
         }
     }
       
     // Method 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];
     }
       
     // Method to calculate average time
     static void findavgTime( int processes[], int n, int bt[], int quantum)
     {
         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, quantum);
       
         // Function to find turn around time for all processes
         findTurnAroundTime(processes, n, bt, wt, tat);
       
         // Display processes along with all details
         System.out.println( "Processes " + " Burst time " +
                       " Waiting time " + " Turn around time" );
       
         // 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.println( " " + (i+ 1 ) + "\t\t" + bt[i] + "\t " +
                               wt[i] + "\t\t " + tat[i]);
         }
       
         System.out.println( "Average waiting time = " +
                           ( float )total_wt / ( float )n);
         System.out.println( "Average turn around time = " +
                            ( float )total_tat / ( float )n);
     }
      
     // Driver Method
     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 };
       
         // Time quantum
         int quantum = 2 ;
         findavgTime(processes, n, burst_time, quantum);
     }
}

Python3

# Python3 program for implementation of 
# RR scheduling 
  
# Function to find the waiting time 
# for all processes 
def findWaitingTime(processes, n, bt, wt, quantum): 
     rem_bt = [ 0 ] * n
  
     # Copy the burst time into rt[] 
     for i in range (n): 
         rem_bt[i] = bt[i]
     t = 0 # Current time 
  
     # Keep traversing processes in round 
     # robin manner until all of them are
     # not done. 
     while ( 1 ):
         done = True
  
         # Traverse all processes one by
         # one repeatedly 
         for i in range (n):
              
             # If burst time of a process is greater 
             # than 0 then only need to process further 
             if (rem_bt[i] > 0 ) :
                 done = False # There is a pending process
                  
                 if (rem_bt[i] > quantum) :
                  
                     # Increase the value of t i.e. shows 
                     # how much time a process has been processed 
                     t + = quantum 
  
                     # Decrease the burst_time of current 
                     # process by quantum 
                     rem_bt[i] - = quantum 
                  
                 # If burst time is smaller than or equal  
                 # to quantum. Last cycle for this process 
                 else :
                  
                     # Increase the value of t i.e. shows 
                     # how much time a process has been processed 
                     t = t + rem_bt[i] 
  
                     # Waiting time is current time minus 
                     # time used by this process 
                     wt[i] = t - bt[i] 
  
                     # As the process gets fully executed 
                     # make its remaining burst time = 0 
                     rem_bt[i] = 0
                  
         # If all processes are done 
         if (done = = True ):
             break
              
# Function to calculate turn around time 
def findTurnAroundTime(processes, n, bt, wt, tat):
      
     # Calculating turnaround time 
     for i in range (n):
         tat[i] = bt[i] + wt[i] 
  
  
# Function to calculate average waiting 
# and turn-around times. 
def findavgTime(processes, n, bt, quantum): 
     wt = [ 0 ] * n
     tat = [ 0 ] * n 
  
     # Function to find waiting time
     # of all processes 
     findWaitingTime(processes, n, bt, wt, quantum) 
  
     # 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" )
     total_wt = 0
     total_tat = 0
     for i in range (n):
  
         total_wt = total_wt + wt[i] 
         total_tat = total_tat + tat[i] 
         print ( " " , i + 1 , "\t\t" , bt[i], "\t\t" , wt[i], "\t\t" , tat[i])
  
     print ( "\nAverage waiting time = %.5f " % (total_wt / n) )
     print ( "Average turn around time = %.5f " % (total_tat / n)) 
      
# Driver code 
if __name__ = = "__main__" :
      
     # Process id's 
     proc = [ 1 , 2 , 3 ]
     n = 3
  
     # Burst time of all processes 
     burst_time = [ 10 , 5 , 8 ] 
  
     # Time quantum 
     quantum = 2 ; 
     findavgTime(proc, n, burst_time, quantum)
  
# This code is contributed by
# Shubham Singh(SHUBHAMSINGH10)

C#

// C# program for implementation of RR
// scheduling
using System;
  
public class GFG {
      
     // Method to find the waiting time
     // for all processes
     static void findWaitingTime( int []processes, int n, int []bt, int []wt, int quantum)
     {
          
         // Make a copy of burst times bt[] to 
         // store remaining burst times.
         int []rem_bt = new int [n];
          
         for ( int i = 0 ; i < n ; i++)
             rem_bt[i] = bt[i];
      
         int t = 0; // Current time
      
         // Keep traversing processes in round
         // robin manner until all of them are
         // not done.
         while ( true )
         {
             bool done = true ;
      
             // Traverse all processes one by
             // one repeatedly
             for ( int i = 0 ; i < n; i++)
             {
                 // If burst time of a process
                 // is greater than 0 then only
                 // need to process further
                 if (rem_bt[i] > 0)
                 {
                      
                     // There is a pending process
                     done = false ;
      
                     if (rem_bt[i] > quantum)
                     {
                         // Increase the value of t i.e.
                         // shows how much time a process
                         // has been processed
                         t += quantum;
      
                         // Decrease the burst_time of 
                         // current process by quantum
                         rem_bt[i] -= quantum;
                     }
      
                     // If burst time is smaller than
                     // or equal to quantum. Last cycle
                     // for this process
                     else
                     {
                          
                         // Increase the value of t i.e.
                         // shows how much time a process
                         // has been processed
                         t = t + rem_bt[i];
      
                         // Waiting time is current
                         // time minus time used by 
                         // this process
                         wt[i] = t - bt[i];
      
                         // As the process gets fully 
                         // executed make its remaining
                         // burst time = 0
                         rem_bt[i] = 0;
                     }
                 }
             }
      
             // If all processes are done
             if (done == true )
             break ;
         }
     }
      
     // Method 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];
     }
      
     // Method to calculate average time
     static void findavgTime( int []processes, int n, int []bt, int quantum)
     {
         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, quantum);
      
         // Function to find turn around time
         // for all processes
         findTurnAroundTime(processes, n, bt, wt, tat);
      
         // Display processes along with
         // all details
         Console.WriteLine( "Processes " + " Burst time " +
                     " Waiting time " + " Turn around time" );
      
         // 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.WriteLine( " " + (i+1) + "\t\t" + bt[i] 
                          + "\t " + wt[i] + "\t\t " + tat[i]);
         }
      
         Console.WriteLine( "Average waiting time = " +
                         ( float )total_wt / ( float )n);
         Console.Write( "Average turn around time = " +
                         ( float )total_tat / ( float )n);
     }
      
     // Driver Method
     public static void Main()
     {
         // process id's
         int []processes = { 1, 2, 3};
         int n = processes.Length;
      
         // Burst time of all processes
         int []burst_time = {10, 5, 8};
      
         // Time quantum
         int quantum = 2;
         findavgTime(processes, n, burst_time, quantum);
     }
}
  
// This code is contributed by nitin mittal.

输出如下：

Processes  Burst time  Waiting time  Turn around time
 1        10     13         23
 2        5     10         15
 3        8     13         21
Average waiting time = 12
Average turn around time = 19.6667

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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