批处理作业调度伪代码

### 批处理作业调度算法伪代码

批处理作业调度是一种用于操作系统中的调度方法，旨在优化CPU利用率和吞吐量。以下是基于先来先服务（FCFS）、最短作业优先（SJF）以及最高响应比优先（HRRN）三种常见策略的批处理作业调度伪代码。

#### 1. 先来先服 (First-Come, First-Served, FCFS)

function fcfs_scheduling(jobs):
    time = 0
    for each job in jobs:
        start_time[job] = time
        finish_time[job] = time + burst_time[job]
        waiting_time[job] = start_time[job] - arrival_time[job]
        turn_around_time[job] = finish_time[job] - arrival_time[job]
        time += burst_time[job]

    return {start_time, finish_time, waiting_time, turn_around_time}

此函数按照到达顺序依次处理每个任务，并计算相应的等待时间和周转时间[^1]。

#### 2. 最短作业优先 (Shortest Job First, SJF)

function sjf_scheduling(jobs):
    sort_jobs_by_burst_time(jobs)
    
    time = 0
    for each job in jobs:
        start_time[job] = max(time, arrival_time[job])
        finish_time[job] = start_time[job] + burst_time[job]
        waiting_time[job] = start_time[job] - arrival_time[job]
        turn_around_time[job] = finish_time[job] - arrival_time[job]
        time = finish_time[job]

    return {start_time, finish_time, waiting_time, turn_around_time}

在此版本中，首先对所有待处理的任务按其所需执行的时间升序排列，从而使得较短的任务能够更早得到执行。

#### 3. 最高响应比优先 (Highest Response Ratio Next, HRRN)

function hrrn_scheduling(jobs):
    while not all_jobs_completed():
        current_time = get_current_system_time()
        
        eligible_jobs = filter_eligible_jobs(current_time, jobs)
        best_job = find_best_job(eligible_jobs, current_time)
        
        execute(best_job)
        update_statistics(best_job, current_time)

function calculate_response_ratio(job, system_time):
    response_ratio = (service_time[job] + (system_time - arrival_time[job])) / service_time[job]
    return response_ratio
    
function find_best_job(jobs, system_time):
    highest_ratio = -infinity
    selected_job = null
    
    foreach job in jobs do
        ratio = calculate_response_ratio(job, system_time)
        if ratio > highest_ratio then
            highest_ratio = ratio
            selected_job = job
            
    return selected_job

这种方法综合考虑了任务的等待时间和预计完成时间，每次选择当前时刻下具有最大响应比率的任务进行执行。