如何在 SimPy 中拆分相关事件

Question

我想实现一个离散事件维护调度模拟，其中一些维护活动必须在另一个维护活动发生时发生。

例如，如果墙壁每 5 年重新粉刷一次，干衬里每 14 年更换一次，那么每当更换干衬里并重新启动时钟时，都必须重新粉刷墙壁。

yr 5:  paint walls
yr 10: paint walls
yr 14: replace dry-lining
yr 14: paint walls
yr 19: paint walls
...

我不确定我是否应该将每个 activity 实现为一个引用依赖进程的进程，或者 "wall maintenance" 是否应该是一个内部处理逻辑的进程，或者其他一些

我的代码将每个 activity 作为一个进程，从属进程存储为一个属性，但我觉得我可能错过了执行此操作的正确方法，因为我看到事件发生了两次同年

Answer 1

这是我最后采用的方法：

import simpy
from simpy.events import Interrupt


class Construction(object):

    def __init__(self, name, components):
        self.name = name
        self.components = components
        self.link_components()

    def link_components(self):
        """Link each component to the next outermost component      
        """
        for i, component in enumerate(self.components):
            try:
                component.dependent = self.components[i+1]
            except IndexError:
                component.dependent = None                

class Component(object):

    def __init__(self, env, name, lifespan):
        """Represents a component used in a construction.

        """
        self.env = env
        self.name = name
        self.lifespan = lifespan    
        self.action = env.process(self.run())

    def run(self):
        while True:
            try:
                yield self.env.timeout(self.lifespan)
                self.replace()
            except Interrupt:  # don't replace
                pass

    def replace(self):
        print "yr %d:  replace %s" % (env.now, self.name)
        if self.dependent:
            self.dependent.action.interrupt()  # stop the dependent process
            self.dependent.replace()  # replace the dependent component


env = simpy.Environment()
components = [Component(env, 'structure', 60),
              Component(env, 'dry-lining', 14),
              Component(env, 'paint', 5)]
wall = Construction('wall', components)
env.run(until=65)

Answer 2

您应该始终从一个非常简单（且错误）的实现开始，以便更好地理解您的用例并感受一切是如何工作的，例如：

import simpy


def paint_walls(env, interval):
    while True:
        yield env.timeout(interval)
        print('yr %2d: paint walls' % env.now)


def replace_dry_lining(env, interval):
    while True:
        yield env.timeout(interval)
        print('yr %d: replace dry-lining' % env.now)


env = simpy.Environment()
env.process(paint_walls(env, interval=5))
env.process(replace_dry_lining(env, interval=14))
env.run(until=20)

输出：

yr  5: paint walls
yr 10: paint walls
yr 14: replace dry-lining
yr 15: paint walls

然后您可以开始extending/modifying您的模拟。以下是如何为您的问题建模的两种可能性：

变体 A

我们继续使用两个独立的进程，但需要一种方法在它们之间交换事件 "dry-lining replaced"，这样我们也可以刷墙：

import simpy


class Maintenance:
    PAINT_WALL_INTERVAL = 5
    REPLACE_DRY_LINING_INTERVAL= 14

    def __init__(self, env):
        self.env = env
        self.dry_lining_replaced = env.event()

        self.p_paint_walls = env.process(self.paint_walls())
        self.p_replace_dry_lining = env.process(self.replace_dry_lining())

    def paint_walls(self):
        timeout = self.PAINT_WALL_INTERVAL
        while True:
            yield self.env.timeout(timeout) | self.dry_lining_replaced
            print('yr %2d: paint walls' % self.env.now)

    def replace_dry_lining(self):
        timeout = self.REPLACE_DRY_LINING_INTERVAL
        while True:
            yield self.env.timeout(timeout)
            print('yr %2d: replace dry-lining' % self.env.now)
            self.dry_lining_replaced.succeed()
            self.dry_lining_replaced = self.env.event()


env = simpy.Environment()
m = Maintenance(env)
env.run(until=20)

输出：

yr  5: paint walls
yr 10: paint walls
yr 14: replace dry-lining
yr 14: paint walls
yr 19: paint walls

变体 B

我们也可以只用一个等待 "paint walls" 或 "replace dry-lining" 事件的进程对其进行建模：

import simpy


def maintenance(env):
    PAINT_WALL_INTERVAL = 5
    REPLACE_DRY_LINING_INTERVAL = 14

    paint_wall = env.timeout(PAINT_WALL_INTERVAL)
    replace_dry_lining = env.timeout(REPLACE_DRY_LINING_INTERVAL)

    while True:
        results = yield paint_wall | replace_dry_lining
        do_paint = paint_wall in results
        do_replace = replace_dry_lining in results

        if do_replace:
            print('yr %2d: replace dry-lining' % env.now)
            replace_dry_lining = env.timeout(REPLACE_DRY_LINING_INTERVAL)

        if do_paint or do_replace:
            print('yr %2d: paint walls' % env.now)
            paint_wall = env.timeout(PAINT_WALL_INTERVAL)


env = simpy.Environment()
env.process(maintenance(env))
env.run(until=20)

输出：

yr  5: paint walls
yr 10: paint walls
yr 14: replace dry-lining
yr 14: paint walls
yr 19: paint walls

如何在 SimPy 中拆分相关事件

How to split up dependent events in SimPy

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