OS page replacement strategy

LRU OPT FIFO

def fifo(frames):
    ram = []
    pageFault = 0 
    for i in data:
        # print(i)
        if i in ram:
            continue #在内存中不替换
        elif len(ram) < frames: # 仍然有空闲的区域可以放页
            ram.append(i)
        else: # 页面置换
            ram.pop(0) # 弹出头部元素     
            ram.append(i) # 将当前页面载入内存
        pageFault += 1
    return pageFault

def opt(frames):
    ram = set() # create a set as memory
    flag = []
    pageFault = 0
    for i in range(len(data)):
        # print(data[i])
        if(data[i] in ram):
            continue
        elif len(ram) < frames:
            ram.add(data[i])
        else:
            # 找到将来最晚使用的
            j = i
            while(j<len(data)):
                if j not in flag:
                    flag.append(data[j]) # flag中保存了页面的出现顺序
                j += 1
            for j in flag[::-1]: # 逆序遍历flag
                if j in ram:
                    ram.remove(j) # 如果存在则从内存中删除
                    break
            ram.add(data[i])
        pageFault += 1
    return pageFault

def lru(frames):
    pageFault = 0
    ram=set()
    pageAge = np.zeros(10)
    for page in data:
        # print(page)
        if page in ram:
            pass
        elif len(ram) < frames:
            ram.add(page)
            pageAge[page] = 1 
        else :
            # LRU替换策略
            pageFault += 1
            oldest = np.argmax(pageAge)
            # print("oldest page ===>", oldest)
            ram.remove(oldest)
            pageAge[oldest] = 0
            ram.add(page)
        "更新页面的年龄"    
        for i in ram: # 在内存中的页面要变老
            pageAge[i] = pageAge[i] + 1
        pageAge[page] = 1 # 进入内存则设置为1
    return pageFault