正在观看:https://www.youtube.com/watch?v=GjrxO-PDPdk YouTube 上的视频启发了我用 C 语言实现 Round Robin 算法:
#include <stdio.h>
#include <stdlib.h>
int check_if_done(int processes[], int n)
{
int i;
for(i=0; i<n; i++)
if(processes[i] > 0)
return 0;
return 1;
}
int main()
{
int processes[5];
int waiting_times[5];
processes[0] = 6;
processes[1] = 5;
processes[2] = 2;
processes[3] = 3;
processes[4] = 7;
int tq = 2;
int i = 0, j, n = 5;
for(j=0; j<n; j++)
waiting_times[j] = 0;
while(1)
{
if(check_if_done(processes, n))
break;
if(processes[i] > 0)
{
printf("P%d = %d\n", i+1, processes[i]);
waiting_times[i] += processes[i];
processes[i] -= tq;
}
i ++;
if(i == n)
{
printf("\n");
i = 0;
}
}
printf("\n");
for(i=0; i<n; i++)
{
printf("P%d waiting time = %d\n", (i+1), waiting_times[i]);
}
return 0;
}
这是我的第一个日程安排方法,它似乎可以按需工作(是吗?)。但是,我在计算平均等待时间时遇到了一些麻烦。我得到了:
P1 waiting time = 12
P2 waiting time = 9
P3 waiting time = 2
P4 waiting time = 4
P5 waiting time = 16
代替:
P1 waiting time = 13
P2 waiting time = 15
P3 waiting time = 4
P4 waiting time = 12
P5 waiting time = 16
最佳答案
代码可以记录每个进程何时停止并记录何时开始。 等待
就是这个区别。
此外,当使用一小部分时间量子时,仅累积该部分。
int main(void) {
int last_run[5];
int processes[5];
int waiting_times[5];
processes[0] = 6;
processes[1] = 5;
processes[2] = 2;
processes[3] = 3;
processes[4] = 7;
int tq = 2;
int i = 0, j, n = 5;
int t = 0; // cumulative time.
for (j = 0; j < n; j++) {
last_run[j] = t; // All processes scheduled at t = 0
waiting_times[j] = 0;
}
while (!check_if_done(processes, n)) {
if (processes[i] > 0) {
printf("P%d = %d\n", i + 1, processes[i]);
waiting_times[i] += t - last_run[i]; // now - last runtime
int t_used = processes[i];
if (t_used > tq) // If time needed more than tq ...
t_used = tq;
processes[i] -= t_used;
t += t_used; // update now
last_run[i] = t;
}
i = (i + 1) % n;
}
printf("\n");
for (i = 0; i < n; i++) {
printf("P%d waiting time = %d\n", (i + 1), waiting_times[i]);
}
return 0;
}
代码可以使用 unsigned
时间值而不是 int
运行。没有负积累,也没有流逝的时间。
注意:代码可以用当前时间初始化 t
并得到相同的结果。 (时间类型应该是 time_t
)
// int t = 0; // cumulative time.
int t = time(0);
关于c - 如何计算循环法中的平均等待时间?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28245322/