Operating_Systems/Lab/Lab5/code/main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define REQUEST_LENGTH 100
#define DISK_TRACKS 200

double fcfs(int* requestArray, int requestLength, int headStart, int* outputArray);
double sstf(int* requestArray, int requestLength, int headStart, int* outputArray);
double scan(int* requestArray, int requestLength, int headStart, int* outputArray);
double cscan(int* requestArray, int requestLength, int headStart, int* outputArray);
double fscan(int* requestArray1, int requestLength1, int* requestArray2, int requestLength2, int headStart, int *outputArray);


// 生成随机磁道访问序列
void generateRandomSequence(int* sequence, int length) {
    for (int i = 0; i < length; i++) {
        sequence[i] = rand() % DISK_TRACKS;
    }
}

// 打印磁道访问顺序及平均寻道数
void printResults(const char* algorithmName, int* accessSequence, int length, double avgSeek) {
    printf("%s Algorithm:\n", algorithmName);
    printf("Visit Order: ");
    for (int i = 0; i < length; i++) {
        printf("%d ", accessSequence[i]);
    }
    printf("\nAvg Seek Times: %.2f\n\n", avgSeek);
}

int main() {
    int requestSequence[REQUEST_LENGTH];
    int *outputSequence[REQUEST_LENGTH];
    int tempSequence[REQUEST_LENGTH];
    double avgSeek;
    int headStart = 50; // 假设的起始磁头位置

    // 生成随机磁道访问序列
    srand((unsigned)time(NULL));
    generateRandomSequence(requestSequence, REQUEST_LENGTH);

    // 测试 FCFS 算法
    memcpy(tempSequence, requestSequence, sizeof(requestSequence));
    avgSeek = fcfs(tempSequence, REQUEST_LENGTH, headStart, outputSequence);
    printResults("FCFS", outputSequence, REQUEST_LENGTH, avgSeek);

    // 测试 SSTF 算法
    memcpy(tempSequence, requestSequence, sizeof(requestSequence));
    avgSeek = sstf(tempSequence, REQUEST_LENGTH, headStart, outputSequence);
    printResults("SSTF", outputSequence, REQUEST_LENGTH, avgSeek);

    // 测试 SCAN 算法
    memcpy(tempSequence, requestSequence, sizeof(requestSequence));
    avgSeek = scan(tempSequence, REQUEST_LENGTH, headStart, outputSequence);
    printResults("SCAN", outputSequence, REQUEST_LENGTH, avgSeek);

    // 测试 CSCAN 算法
    memcpy(tempSequence, requestSequence, sizeof(requestSequence));
    avgSeek = cscan(tempSequence, REQUEST_LENGTH, headStart, outputSequence);
    printResults("CSCAN", outputSequence, REQUEST_LENGTH, avgSeek);

    // 测试 FSCAN 算法
    // 注意：FSCAN需要两个队列，但为简化，在这里使用相同的队列两次
    memcpy(tempSequence, requestSequence, sizeof(requestSequence));
    avgSeek = fscan(requestSequence, REQUEST_LENGTH / 2, requestSequence + REQUEST_LENGTH / 2, REQUEST_LENGTH / 2, headStart, outputSequence);
    printResults("FSCAN", outputSequence, REQUEST_LENGTH, avgSeek);

    return 0;
}


double fcfs(int* requestArray, int requestLength, int headStart, int* outputArray) {
    int totalMovement = 0;
    int currentPosition = headStart;

    for (int i = 0; i < requestLength; i++) {
        // 计算当前请求和磁头位置之间的距离
        totalMovement += abs(requestArray[i] - currentPosition);
        // 移动磁头到当前请求位置
        currentPosition = requestArray[i];
        // 记录移动过程
        outputArray[i] = currentPosition;
    }

    // 计算平均寻道数
    return (double)totalMovement / requestLength;
}

double sstf(int* requestArray, int requestLength, int headStart, int* outputArray) {
    int totalSeekCount = 0;
    int processedCount = 0;
    int currentPosition = headStart;
    int minDistance, closestIndex;

    // 初始化一个数组来标记已处理的请求
    int processed[REQUEST_LENGTH] = {0};
    for (int i = 0; i < requestLength; i++) processed[i] = 0;

    while (processedCount < requestLength) {
        minDistance = 2147483647;

        // 找到最近的请求
        for (int i = 0; i < requestLength; i++) {
            if (!processed[i] && abs(requestArray[i] - currentPosition) < minDistance) {
                minDistance = abs(requestArray[i] - currentPosition);
                closestIndex = i;
            }
        }

        // 处理这个请求
        totalSeekCount += minDistance;
        currentPosition = requestArray[closestIndex];
        processed[closestIndex] = 1;
        outputArray[processedCount++] = currentPosition;
    }

    // 计算平均寻道数
    return (double)totalSeekCount / requestLength;
}

int compare(const void *a, const void *b) {
    return (*(int*)a - *(int*)b);
}

double scan(int* requestArray, int requestLength, int headStart, int* outputArray) {
    int totalSeekCount = 0;
    int processedCount = 0;
    int currentPosition = headStart;

    // 使用qsort进行排序
    qsort(requestArray, requestLength, sizeof(int), compare);

    // 找到起始位置最近的请求
    int startIndex;
    for (startIndex = 0; startIndex < requestLength; startIndex++) {
        if (requestArray[startIndex] >= headStart) break;
    }

    // 先向上移动
    for (int i = startIndex; i < requestLength; i++) {
        totalSeekCount += abs(currentPosition - requestArray[i]);
        currentPosition = requestArray[i];
        outputArray[processedCount++] = currentPosition;
    }

    // 然后向下移动
    for (int i = startIndex - 1; i >= 0; i--) {
        totalSeekCount += abs(currentPosition - requestArray[i]);
        currentPosition = requestArray[i];
        outputArray[processedCount++] = currentPosition;
    }

    // 计算平均寻道数
    return (double)totalSeekCount / requestLength;
}

double cscan(int* requestArray, int requestLength, int headStart, int* outputArray) {
    int totalSeekCount = 0;
    int processedCount = 0;
    int currentPosition = headStart;

    // 使用 qsort 进行排序
    qsort(requestArray, requestLength, sizeof(int), compare);

    // 找到起始位置最近的请求索引
    int startIndex;
    for (startIndex = 0; startIndex < requestLength; startIndex++) {
        if (requestArray[startIndex] >= headStart) break;
    }

    // 先处理磁头上方的请求
    for (int i = startIndex; i < requestLength; i++) {
        totalSeekCount += abs(currentPosition - requestArray[i]);
        currentPosition = requestArray[i];
        outputArray[processedCount++] = currentPosition;
    }

    // 如果有必要，跳转到最低请求
    if (startIndex != 0) {
        totalSeekCount += abs(currentPosition - requestArray[0]);
        currentPosition = requestArray[0];
    }

    // 然后处理磁头下方的请求
    for (int i = 0; i < startIndex; i++) {
        totalSeekCount += abs(currentPosition - requestArray[i]);
        currentPosition = requestArray[i];
        outputArray[processedCount++] = currentPosition;
    }

    // 计算平均寻道数
    return (double)totalSeekCount / requestLength;
}

void processQueue(int* queue, int length, int* currentPosition, int* totalSeekCount, int* outputArray, int* processedCount) {
    // 对队列进行排序
    qsort(queue, length, sizeof(int), compare);

    // 找到最接近当前磁头位置的请求
    int i = 0;
    while (i < length && queue[i] < *currentPosition) {
        i++;
    }

    // 先处理磁头位置之后（更高磁道号）的请求
    for (int j = i; j < length; j++) {
        *totalSeekCount += abs(*currentPosition - queue[j]);
        *currentPosition = queue[j];
        outputArray[(*processedCount)++] = queue[j];
    }

    // 再处理磁头位置之前（更低磁道号）的请求
    for (int j = i - 1; j >= 0; j--) {
        *totalSeekCount += abs(*currentPosition - queue[j]);
        *currentPosition = queue[j];
        outputArray[(*processedCount)++] = queue[j];
    }
}

double fscan(int* requestArray1, int requestLength1, int* requestArray2, int requestLength2, int headStart, int* outputArray) {
    int totalSeekCount = 0;
    int currentPosition = headStart;
    int processedCount = 0;

    // 处理第一个队列
    processQueue(requestArray1, requestLength1, &currentPosition, &totalSeekCount, outputArray, &processedCount);

    // 处理第二个队列
    processQueue(requestArray2, requestLength2, &currentPosition, &totalSeekCount, outputArray + requestLength1, &processedCount);

    // 计算平均寻道数
    return (double)totalSeekCount / (requestLength1 + requestLength2);
}