14.试比较短进程优先和最短剩余时间优先这两种进程调度算法。

这是一个技术问题，我可以回答。短进程优先调度算法是指优先调度执行时间短的进程，而最短剩余时间优先调度算法则是在短进程优先的基础上，根据进程的剩余运行时间来进行调度，即优先调度剩余时间最短的进程。最短剩余时间优先调度算法能够更为准确地反映进程的运行情况，但会导致更频繁的进程切换，影响系统的运行效率。

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代码实现时间片轮转调度、优先数调度、最短进程优先、最短剩余时间优先四种调度方法

时间片轮转调度：

class Process:
    def __init__(self, name, arrival_time, burst_time):
        self.name = name
        self.arrival_time = arrival_time
        self.burst_time = burst_time
        self.remaining_time = burst_time

    def execute(self, quantum):
        if self.remaining_time > quantum:
            self.remaining_time -= quantum
            return quantum
        else:
            time_executed = self.remaining_time
            self.remaining_time = 0
            return time_executed


def schedule_rr(processes, quantum):
    time = 0
    num_processes = len(processes)
    queue = processes[:]
    completed_processes = []
    current_process = None

    while len(completed_processes) < num_processes:
        # add arriving processes to the queue
        for p in processes:
            if p.arrival_time == time and p not in queue and p not in completed_processes:
                queue.append(p)

        # get next process to execute
        if not current_process or current_process.remaining_time == 0:
            if queue:
                current_process = queue.pop(0)
            else:
                time += 1
                continue

        # execute current process for a quantum
        time_executed = current_process.execute(quantum)
        time += time_executed

        # check if process has completed
        if current_process.remaining_time == 0:
            completed_processes.append(current_process)

    return completed_processes

优先数调度：

class Process:
    def __init__(self, name, arrival_time, burst_time, priority):
        self.name = name
        self.arrival_time = arrival_time
        self.burst_time = burst_time
        self.remaining_time = burst_time
        self.priority = priority

    def execute(self):
        self.remaining_time -= 1


def schedule_priority(processes):
    time = 0
    num_processes = len(processes)
    queue = processes[:]
    completed_processes = []
    current_process = None

    while len(completed_processes) < num_processes:
        # add arriving processes to the queue
        for p in processes:
            if p.arrival_time == time and p not in queue and p not in completed_processes:
                queue.append(p)

        # get next process to execute
        if not current_process or current_process.remaining_time == 0:
            if queue:
                queue.sort(key=lambda p: p.priority)
                current_process = queue.pop(0)
            else:
                time += 1
                continue

        # execute current process
        current_process.execute()
        time += 1

        # check if process has completed
        if current_process.remaining_time == 0:
            completed_processes.append(current_process)

    return completed_processes

最短进程优先：

class Process:
    def __init__(self, name, arrival_time, burst_time):
        self.name = name
        self.arrival_time = arrival_time
        self.burst_time = burst_time
        self.remaining_time = burst_time

    def execute(self):
        self.remaining_time -= 1


def schedule_sjf(processes):
    time = 0
    num_processes = len(processes)
    queue = processes[:]
    completed_processes = []
    current_process = None

    while len(completed_processes) < num_processes:
        # add arriving processes to the queue
        for p in processes:
            if p.arrival_time == time and p not in queue and p not in completed_processes:
                queue.append(p)

        # get next process to execute
        if not current_process or current_process.remaining_time == 0:
            if queue:
                queue.sort(key=lambda p: p.burst_time)
                current_process = queue.pop(0)
            else:
                time += 1
                continue

        # execute current process
        current_process.execute()
        time += 1

        # check if process has completed
        if current_process.remaining_time == 0:
            completed_processes.append(current_process)

    return completed_processes

最短剩余时间优先：

class Process:
    def __init__(self, name, arrival_time, burst_time):
        self.name = name
        self.arrival_time = arrival_time
        self.burst_time = burst_time
        self.remaining_time = burst_time

    def execute(self):
        self.remaining_time -= 1


def schedule_srt(processes):
    time = 0
    num_processes = len(processes)
    queue = processes[:]
    completed_processes = []
    current_process = None

    while len(completed_processes) < num_processes:
        # add arriving processes to the queue
        for p in processes:
            if p.arrival_time == time and p not in queue and p not in completed_processes:
                queue.append(p)

        # get next process to execute
        if not current_process or current_process.remaining_time == 0:
            if queue:
                queue.sort(key=lambda p: p.remaining_time)
                current_process = queue.pop(0)
            else:
                time += 1
                continue

        # execute current process
        current_process.execute()
        time += 1

        # check if process has completed
        if current_process.remaining_time == 0:
            completed_processes.append(current_process)

    return completed_processes

抢占式短作业优先和最短剩余时间优先

抢占式短作业优先（Shortest Job First, SJF）和最短剩余时间优先（Shortest Remaining Time, SRT）都是基于短作业优先（Shortest Job First, SJN）算法的改进版本。

SJF算法是指在进程队列中，按照估计的运行时间（或执行的指令数）进行排序，然后按照排好序的顺序依次执行进程。但是，SJF算法存在一个问题，即如果有一个长作业进入队列，那么短作业就必须一直等待，这会导致短作业的等待时间变长。

抢占式短作业优先算法是在SJF算法的基础上改进而来的，它允许新的短作业插入到正在运行的作业之前，从而减少短作业的等待时间。如果有一个新的短作业进入队列，那么它会立即替换正在运行的长作业，从而实现抢占。

最短剩余时间优先算法也是在SJF算法的基础上改进而来的。在这种算法中，进程的优先级是根据它们还需要执行的时间来确定的，即所谓的剩余时间。每当一个新进程到达时，它会与正在执行的进程的剩余时间进行比较。如果新进程的剩余时间比正在执行的进程的剩余时间短，那么新进程就会被优先执行。如果正在执行的进程的剩余时间比新进程的剩余时间短，那么当前进程就会继续执行，直到完成或者被抢占。

总的来说，抢占式短作业优先算法和最短剩余时间优先算法都可以有效地减少短作业的等待时间，提高系统的性能。但是，它们都需要记录每个进程的剩余时间，这会增加系统的开销。此外，抢占式算法可能会导致长作业的等待时间变长，因为短作业会频繁抢占正在执行的长作业。