Question

我想为电梯系统编写一个多线程程序。电梯系统只能在状态为running或wait状态时移动。在系统中，可以以多线程方式添加指令（要转到的楼层）。为了管理指令队列并获得升降机的下一站，我编写了一个QueueManager类。我无法弄清楚如何实现QueueManager。问题是我无法理解编写QueueManager。特别是在弄清楚如何从队列中获取Lift的下一站。这是我在python3中对系统的实现：

"""Implementation of a lift System"""

from enum import Enum
from typing import TypeVar
from threading import Thread
import queue


LiftType = TypeVar('LiftType', bound='Lift')
QueueManagerType = TypeVar('QueueManagerType', bound='QueueManager')
SensorNameType = TypeVar('SensorNameType', bound='SensorName')
DirectionType = TypeVar('DirectionType', bound='DirectionType')

class SensorName(Enum):
  weight = 'weight'
  smoke = 'smoke'

class Direction(Enum):
  up = 1
  down = -1

class State(Enum):
  running = 'running'
  wait = 'waiting'
  stop = 'stop'

class Lift:
  def __init__(self, num_floors: int, queue_manager: QueueManagerType):
    """
    Contains all the properties of lift
    """
    self.num_floors = num_floors
    self.curr_direction = Direction.up
    self.state = State.running
    self.curr_floor = 0
    self.queue_manager = queue_manager

  def move(self):
    """
    Moves the lift according to the instruction
    """
    if self.state in [State.running, State.wait]:
      if self.queue_manager.has_instruction():
        self.state = State.running
        stop = self.queue_manager.next_stop(self.curr_direction, self.curr_floor)
        if stop:
          print(stop)
        else:
          if self.curr_direction == Direction.up:
            self.curr_direction = Direction.down
            stop = self.queue_manager.next_stop(self.curr_direction,
                                                self.curr_floor)
            print(stop)
          else:
            self.curr_direction = Direction.up
      else:
        self.state = State.wait

  def add_instruction(self, floor, direction=None):
    """Adds the instruction to the queue"""
    if direction is None:
      if self.curr_floor > floor:
        direction = Direction.down
      else:
        direction = Direction.up
    Thread(target=self.queue_manager.add_instruction, args=(floor, direction)).start()
    self.move()

class QueueManager:
  def __init__(self):
    self.instruction_queue = queue.Queue()

  def add_instruction(self, floor: int, direction: DirectionType):
    """Add an instruction to the queue. Direction is used """
    self.instruction_queue.put([floor, direction])

  def next_stop(self, direction: int, curr_floor: int):
    """Tells which is the next stop based on the direction provided."""
    pass


  def has_instruction(self):
    """If there are any instructions for the lift"""
    pass


if __name__ == '__main__':
  # weight_sensor = WeightSensor(SensorName.weight)
  instruction_queue = QueueManager()
  lift_1 = Lift(21, instruction_queue)
  lift_1.add_instruction(floor=0, direction=Direction.up)
  lift_1.add_instruction(floor=2)

对上述程序的扩展是编写一个在后台运行的Sensor类，如果某个传感器被触发，则将提升设置为停止状态。这也是我无法弄清楚的事情。

Answer 1

根据我在评论中得到的反馈。这是电梯系统的多线程解决方案。

"""Implementation of a lift System"""

from enum import Enum
from typing import TypeVar
from threading import Lock, Thread
from heapq import heappush, heappop
import time
import random


LiftType = TypeVar('LiftType', bound='Lift')
QueueManagerType = TypeVar('QueueManagerType', bound='QueueManager')
SensorNameType = TypeVar('SensorNameType', bound='SensorName')
DirectionType = TypeVar('DirectionType', bound='DirectionType')

class SensorName(Enum):
  weight = 'weight'
  smoke = 'smoke'

class Direction(Enum):
  up = 1
  down = -1

class State(Enum):
  running = 'running'
  wait = 'waiting'
  stop = 'stop'

class Lift:
  def __init__(self, num_floors: int):
    """
    Contains all the properties of lift
    :param sensors: A list of sensor objects
    """
    self.num_floors = num_floors
    self.curr_direction = Direction.up
    self.state = State.running
    self.curr_floor = 0
    self.instruction_queue = {Direction.up: [], Direction.down: []}
    self.queue_lock = Lock()

  def move(self):
    """
    Moves the lift according to the instruction
    """
    if self.state in [State.running, State.wait]:
      if len(self.instruction_queue[Direction.up]) or len(self.instruction_queue[Direction.down]):
        self.state = State.running
        try:
          stop = heappop(self.instruction_queue[Direction.up])
        except IndexError:
          stop = -1
        if stop > -1:
          self.curr_floor = stop
          print(stop, Direction.up)
        else:
          if self.curr_direction == Direction.up:
            self.curr_direction = Direction.down
            if len(self.instruction_queue[Direction.down]):
              stop = heappop(self.instruction_queue[Direction.down])
              self.curr_floor = stop
              print(stop, Direction.down)
            else:
              self.state = State.wait
          else:
            self.curr_direction = Direction.up
        self.move()
      else:
        self.state = State.wait

  def add_instruction(self, floor, direction=None):
    if direction == Direction.up:
      time.sleep(random.uniform(0,1))
    else:
      time.sleep(random.uniform(0,4))
    if direction is None:
      if self.curr_floor > floor:
        direction = Direction.down
      else:
        direction = Direction.up
    with self.queue_lock:
      heappush(self.instruction_queue[direction], floor)
    self.move()


if __name__ == '__main__':
  lift_1 = Lift(21)
  lift_1.add_instruction(0, Direction.up)
  Thread(target=lift_1.add_instruction, args=(2,)).start()
  Thread(target=lift_1.add_instruction, args=(5,)).start()
  Thread(target=lift_1.add_instruction, args=(2,)).start()
  Thread(target=lift_1.add_instruction, args=(18,)).start()
  Thread(target=lift_1.add_instruction, args=(12,)).start()
  Thread(target=lift_1.add_instruction, args=(21,)).start()

如何设计多线程电梯系统并处理并发？

1 个答案: