页面置换算法c语言 4种

页面置换算法是操作系统中的一个重要部分，主要用于管理内存。下面介绍四种常见的页面置换算法的C语言实现。

1. 先进先出（FIFO）算法：

int pages[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int frames = 3; // 物理内存中的页框数
int page_faults = 0; // 缺页数
int frame_buffer[frames];
int frame_index = 0;

for(int i = 0; i < 10; i++) {
    int page = pages[i];
    int found = 0;
    for(int j = 0; j < frames; j++) {
        if(frame_buffer[j] == page) {
            found = 1;
            break;
        }
    }
    if(!found) {
        frame_buffer[frame_index] = page;
        frame_index = (frame_index + 1) % frames;
        page_faults++;
    }
}
printf("缺页数: %d", page_faults);

2. 最近最少使用（LRU）算法：

int pages[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int frames = 3; // 物理内存中的页框数
int page_faults = 0; // 缺页数
int frame_buffer[frames];
int lru_index[frames];

for(int i = 0; i < frames; i++) {
    frame_buffer[i] = -1;
    lru_index[i] = 0;
}

for(int i = 0; i < 10; i++) {
    int page = pages[i];
    int found = 0;
    for(int j = 0; j < frames; j++) {
        if(frame_buffer[j] == page) {
            found = 1;
            lru_index[j] = 0;
            break;
        }
    }
    if(!found) {
        int lru_frame = 0;
        for(int j = 0; j < frames; j++) {
            if(lru_index[j] > lru_index[lru_frame]) {
                lru_frame = j;
            }
        }
        frame_buffer[lru_frame] = page;
        lru_index[lru_frame] = 0;
        page_faults++;
    }
    for(int j = 0; j < frames; j++) {
        lru_index[j]++;
    }
}
printf("缺页数: %d", page_faults);

3. 时钟（Clock）算法：

int pages[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int frames = 3; // 物理内存中的页框数
int page_faults = 0; // 缺页数
int frame_buffer[frames];
int reference_bit[frames];
int hand = 0;

for(int i = 0; i < frames; i++) {
    frame_buffer[i] = -1;
    reference_bit[i] = 0;
}

for(int i = 0; i < 10; i++) {
    int page = pages[i];
    int found = 0;
    for(int j = 0; j < frames; j++) {
        if(frame_buffer[j] == page) {
            found = 1;
            reference_bit[j] = 1;
            break;
        }
    }
    if(!found) {
        while(reference_bit[hand] != 0) {
            reference_bit[hand] = 0;
            hand = (hand + 1) % frames;
        }
        frame_buffer[hand] = page;
        reference_bit[hand] = 1;
        hand = (hand + 1) % frames;
        page_faults++;
    }
}
printf("缺页数: %d", page_faults);

4. 最不常用（LFU）算法：

int pages[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
int frames = 3; // 物理内存中的页框数
int page_faults = 0; // 缺页数
int frame_buffer[frames];
int frequency[frames];

for(int i = 0; i < frames; i++) {
    frame_buffer[i] = -1;
    frequency[i] = 0;
}

for(int i = 0; i < 10; i++) {
    int page = pages[i];
    int found = 0;
    for(int j = 0; j < frames; j++) {
        if(frame_buffer[j] == page) {
            found = 1;
            frequency[j]++;
            break;
        }
    }
    if(!found) {
        int lfu_frame = 0;
        for(int j = 0; j < frames; j++) {
            if(frequency[j] < frequency[lfu_frame]) {
                lfu_frame = j;
            }
        }
        frame_buffer[lfu_frame] = page;
        frequency[lfu_frame] = 1;
        page_faults++;
    }
}
printf("缺页数: %d", page_faults);