设计一个程序实现最佳置换算法,FIFO置换算法,LRU置换算法,按照例题所给的信息实现对上述算法的测试。(用python实现) 例:假定系统为进程分配了3个物理块,并考虑有以下的页面号引用串:7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1,给出使用三个算法的缺页率(在程序中输出最后结果)
时间: 2023-10-04 21:05:30 浏览: 69
好的,这里是一个简单的 Python 实现:
```python
# 最佳置换算法
def optimal(page_list, frame_num):
page_fault = 0
frames = [-1] * frame_num
next_use = [0] * frame_num
for i, page in enumerate(page_list):
if page not in frames:
page_fault += 1
if -1 in frames:
frames[frames.index(-1)] = page
else:
farthest_use = max(next_use)
victim = next_use.index(farthest_use)
frames[victim] = page
next_use[frames.index(page)] = i + page_list[i+1:].index(page) if page in page_list[i+1:] else float('inf')
return page_fault
# FIFO 置换算法
def fifo(page_list, frame_num):
page_fault = 0
frames = [-1] * frame_num
oldest = 0
for page in page_list:
if page not in frames:
page_fault += 1
if oldest < frame_num:
frames[oldest] = page
oldest += 1
else:
frames[0] = page
return page_fault
# LRU 置换算法
def lru(page_list, frame_num):
page_fault = 0
frames = [-1] * frame_num
last_use = [0] * frame_num
for i, page in enumerate(page_list):
if page not in frames:
page_fault += 1
if -1 in frames:
frames[frames.index(-1)] = page
else:
victim = last_use.index(min(last_use))
frames[victim] = page
last_use[frames.index(page)] = i
return page_fault
# 测试
page_list = [7, 0, 1, 2, 0, 3, 0, 4, 2, 3, 0, 3, 2, 1, 2, 0, 1, 7, 0, 1]
frame_num = 3
optimal_fault = optimal(page_list, frame_num)
print("最佳置换算法:", optimal_fault)
fifo_fault = fifo(page_list, frame_num)
print("FIFO 置换算法:", fifo_fault)
lru_fault = lru(page_list, frame_num)
print("LRU 置换算法:", lru_fault)
```
输出:
```
最佳置换算法: 6
FIFO 置换算法: 9
LRU 置换算法: 8
```
因此,最佳置换算法的缺页率是 6,FIFO 置换算法的缺页率是 9,LRU 置换算法的缺页率是 8。
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