FCFS CPU 调度程序|设置 2（具有不同到达时间的进程）
我们已经讨论了具有相同到达时间的进程的 FCFS 调度。在这篇文章中，讨论了流程具有不同到达时间时的场景。给定 n 个进程及其突发时间和到达时间，任务是使用 FCFS 调度算法找到平均等待时间和平均周转时间。
FIFO 只是按照进程到达就绪队列的顺序对它们进行排队。在这里，先到的进程将首先执行，只有在前一个进程完全执行后才会启动下一个进程。
- 完成时间：流程完成执行的时间。
- 周转时间：完成时间和到达时间之间的时间差。周转时间 = 完成时间 - 到达时间
- 等待时间（WT）：周转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。
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Process Wait Time : Service Time - Arrival Time
P0 0 - 0 = 0
P1 5 - 1 = 4
P2 8 - 2 = 6
P3 16 - 3 = 13
Average Wait Time: (0 + 4 + 6 + 13) / 4 = 5.75服务时间：服务时间是指进程可以开始执行之前的时间量。它是先前进程（Processes that come before）的突发时间的总和
与具有相同到达时间的 FCFS代码相比，代码的变化：
求等待时间：当前进程启动前所有进程所花费的时间（即之前所有进程的突发时间）——当前进程的到达时间
等待时间[i] = (bt[0] + bt[1] +…… bt[i-1] ) – 到达时间[i]
执行：
1- Input the processes along with their burst time(bt)
and arrival time(at)
2- Find waiting time for all other processes i.e. for
a given process i:
wt[i] = (bt[0] + bt[1] +...... bt[i-1]) - at[i]
3- Now find turn around time
= waiting_time + burst_time for all processes
4- Average waiting time =
total_waiting_time / no_of_processes
5- Average turn around time =
total_turn_around_time / no_of_processesC++
// C++ program for implementation of FCFS
// scheduling with different arrival time
#include
using namespace std;
// Function to find the waiting time for all
// processes
void findWaitingTime(int processes[], int n, int bt[],
int wt[], int at[])
{
int service_time[n];
service_time[0] = at[0];
wt[0] = 0;
// calculating waiting time
for (int i = 1; i < n ; i++)
{
// Add burst time of previous processes
service_time[i] = service_time[i-1] + bt[i-1];
// Find waiting time for current process =
// sum - at[i]
wt[i] = service_time[i] - at[i];
// If waiting time for a process is in negative
// that means it is already in the ready queue
// before CPU becomes idle so its waiting time is 0
if (wt[i] < 0)
wt[i] = 0;
}
}
// 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 waiting and turn-around
// times.
void findavgTime(int processes[], int n, int bt[], int at[])
{
int wt[n], tat[n];
// Function to find waiting time of all processes
findWaitingTime(processes, n, bt, wt, at);
// 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 " << " Arrival Time "
<< " Waiting Time " << " Turn-Around Time "
<< " Completion Time \n";
int total_wt = 0, total_tat = 0;
for (int i = 0 ; i < n ; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
int compl_time = tat[i] + at[i];
cout << " " << i+1 << "\t\t" << bt[i] << "\t\t"
<< at[i] << "\t\t" << wt[i] << "\t\t "
<< tat[i] << "\t\t " << compl_time << 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[] = {5, 9, 6};
// Arrival time of all processes
int arrival_time[] = {0, 3, 6};
findavgTime(processes, n, burst_time, arrival_time);
return 0;
} Java
// Java program for implementation of FCFS
// scheduling with different arrival time
public class GFG{
// Function to find the waiting time for all
// processes
static void findWaitingTime(int processes[], int n, int bt[], int wt[], int at[])
{
int service_time[] = new int[n];
service_time[0] = at[0];
wt[0] = 0;
// calculating waiting time
for (int i = 1; i < n ; i++)
{
//representing wasted time in queue
int wasted=0;
// Add burst time of previous processes
service_time[i] = service_time[i-1] + bt[i-1];
// Find waiting time for current process =
// sum - at[i]
wt[i] = service_time[i] - at[i];
// If waiting time for a process is in negative
// that means it is already in the ready queue
// before CPU becomes idle so its waiting time is 0
// wasted time is basically time for process to wait after a process is over
if (wt[i] < 0) {
wasted = Math.abs(wt[i]);
wt[i] = 0;
}
//Add wasted time
service_time[i] = service_time[i] + wasted;
}
}
// 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 waiting and turn-around
// times.
static void findavgTime(int processes[], int n, int bt[], int at[])
{
int wt[] = new int[n], tat[] = new int[n];
// Function to find waiting time of all processes
findWaitingTime(processes, n, bt, wt, at);
// Function to find turn around time for all processes
findTurnAroundTime(processes, n, bt, wt, tat);
// Display processes along with all details
System.out.print("Processes " + " Burst Time " + " Arrival Time "
+ " Waiting Time " + " Turn-Around Time "
+ " Completion Time \n");
int total_wt = 0, total_tat = 0;
for (int i = 0 ; i < n ; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
int compl_time = tat[i] + at[i];
System.out.println(i+1 + "\t\t" + bt[i] + "\t\t"
+ at[i] + "\t\t" + wt[i] + "\t\t "
+ tat[i] + "\t\t " + compl_time);
}
System.out.print("Average waiting time = "
+ (float)total_wt / (float)n);
System.out.print("\nAverage turn around time = "
+ (float)total_tat / (float)n);
}
// 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[] = {5, 9, 6};
// Arrival time of all processes
int arrival_time[] = {0, 3, 6};
findavgTime(processes, n, burst_time, arrival_time);
}
}
/*This code is contributed by PrinciRaj1992*/Python3
# Python3 program for implementation of FCFS
# scheduling with different arrival time
# Function to find the waiting time
# for all processes
def findWaitingTime(processes, n, bt, wt, at):
service_time = [0] * n
service_time[0] = 0
wt[0] = 0
# calculating waiting time
for i in range(1, n):
# Add burst time of previous processes
service_time[i] = (service_time[i - 1] +
bt[i - 1])
# Find waiting time for current
# process = sum - at[i]
wt[i] = service_time[i] - at[i]
# If waiting time for a process is in
# negative that means it is already
# in the ready queue before CPU becomes
# idle so its waiting time is 0
if (wt[i] < 0):
wt[i] = 0
# 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 waiting
# and turn-around times.
def findavgTime(processes, n, bt, at):
wt = [0] * n
tat = [0] * n
# Function to find waiting time
# of all processes
findWaitingTime(processes, n, bt, wt, at)
# 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 Arrival Time Waiting",
"Time Turn-Around Time Completion Time \n")
total_wt = 0
total_tat = 0
for i in range(n):
total_wt = total_wt + wt[i]
total_tat = total_tat + tat[i]
compl_time = tat[i] + at[i]
print(" ", i + 1, "\t\t", bt[i], "\t\t", at[i],
"\t\t", wt[i], "\t\t ", tat[i], "\t\t ", compl_time)
print("Average waiting time = %.5f "%(total_wt /n))
print("\nAverage turn around time = ", total_tat / n)
# Driver code
if __name__ =="__main__":
# Process id's
processes = [1, 2, 3]
n = 3
# Burst time of all processes
burst_time = [5, 9, 6]
# Arrival time of all processes
arrival_time = [0, 3, 6]
findavgTime(processes, n, burst_time,
arrival_time)
# This code is contributed
# Shubham Singh(SHUBHAMSINGH10)C#
// C# program for implementation of FCFS
// scheduling with different arrival time
using System;
public class GFG{
// Function to find the waiting time for all
// processes
static void findWaitingTime(int []processes, int n, int []bt, int []wt, int []at)
{
int []service_time = new int[n];
service_time[0] = 0;
wt[0] = 0;
// calculating waiting time
for (int i = 1; i < n ; i++)
{
// Add burst time of previous processes
service_time[i] = service_time[i-1] + bt[i-1];
// Find waiting time for current process =
// sum - at[i]
wt[i] = service_time[i] - at[i];
// If waiting time for a process is in negative
// that means it is already in the ready queue
// before CPU becomes idle so its waiting time is 0
if (wt[i] < 0)
wt[i] = 0;
}
}
// 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 waiting and turn-around
// times.
static void findavgTime(int []processes, int n, int []bt, int []at)
{
int []wt = new int[n]; int []tat = new int[n];
// Function to find waiting time of all processes
findWaitingTime(processes, n, bt, wt, at);
// 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 " + " Arrival Time "
+ " Waiting Time " + " Turn-Around Time "
+ " Completion Time \n");
int total_wt = 0, total_tat = 0;
for (int i = 0 ; i < n ; i++)
{
total_wt = total_wt + wt[i];
total_tat = total_tat + tat[i];
int compl_time = tat[i] + at[i];
Console.WriteLine(i+1 + "\t\t" + bt[i] + "\t\t"
+ at[i] + "\t\t" + wt[i] + "\t\t "
+ tat[i] + "\t\t " + compl_time);
}
Console.Write("Average waiting time = "
+ (float)total_wt / (float)n);
Console.Write("\nAverage turn around time = "
+ (float)total_tat / (float)n);
}
// 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 = {5, 9, 6};
// Arrival time of all processes
int []arrival_time = {0, 3, 6};
findavgTime(processes, n, burst_time, arrival_time);
}
}
// This code is contributed by Princi SinghJavascript
输出：
Processes Burst Time Arrival Time Waiting Time Turn-Around Time Completion Time
1 5 0 0 5 5
2 9 3 2 11 14
3 6 6 8 14 20
Average waiting time = 3.33333
Average turn around time = 10.0