需要帮助使用 SimPy 对火车系统进行建模

Question

我需要帮助在 SimPy 中建模火车系统（如地铁系统），问题是我的“模拟”老师要我使用 Python + SimPy，但我不知道如何使用它，经过一周阅读有关 SimPy 我设法理解了银行示例，这很容易，但现在我仍然不知道如何为老师给我的问题建模......

这个问题很大而且很广泛，但我只需要一点帮助，而不是整个项目完成，所以，如果有人可以提供帮助，我将不胜感激。

帮助我入门的简化问题是这样的：

假设您有 3 个车站（A、B、C），相隔一定距离（比如说 100m），我有 2 列火车，一列在 A 上，一列在 C 上（train1 从 A 到 C，tran2 从 C 到A）每列火车都有最大速度（假设两者都为 50m/s）和加速度（假设为 5m/s^2 和 -5m/s^2 用于制动），他们所要做的就是在每个车站停下来几秒钟（假设是 24 秒）然后继续到下一个车站，当他们到达终点时，他们等待并额外等待 20 秒（换轨）然后重新开始。

车站有乘客限制（不需要模拟），唯一的问题是每个车站的乘客数量是随机的，当火车到达时，有人起床，有人下车......

所以，基本上我需要一个小模型的火车和这 3 个车站的车站...如果有人可以帮助我...

真正的问题有 22 个车站、2 个额外的变道车站、随机等待时间、42 列不同最大速度和容量的列车、根据车站和一天中的时间产生不同的乘客数量等等......所有这东西我以后可以管理，但火车站系统的建模逻辑我似乎无法弄清楚......谢谢你的帮助！

Answer 1

我绝不是 SimPy 方面的专家，但这应该可以帮助您入门：

"""
Simulation of a train network
"""
from SimPy.Simulation import *
from math import sqrt
from random import randint
from itertools import cycle

def timeTo(A, maxV, d):
    """
    Given a trapezoidal velocity envelope defined by
    A       constant acceleration, m/s/s
    maxV    maximumum velocity, m/s
    return time in seconds required to travel
    d       distance, m
    """
    tA = float(maxV)/A          # time to accelerate to maxV
    dA = A*tA*tA                # distance traveled during acceleration from 0 to maxV and back to 0
    if (d < dA):                # train never reaches full speed?
        return sqrt(4.0*d/A)        # time needed to accelerate to half-way point then decelerate to destination
    else:
        return 2*tA + (d-dA)/maxV   # time to accelerate to maxV plus travel at maxV plus decelerate to destination

class Train(Process):
    def __init__(self, name, sim, accel=1.0, maxV=50.0, passengers=0, maxPassengers=400):
        super(Train, self).__init__(name, sim)
        self.accel = accel
        self.maxV  = maxV
        self.p     = passengers
        self.maxP  = maxPassengers

    def roll(self, route):
        here = route.next()     # starting location
        for dest in route:
            # travel to next station
            print "{:.1f}s: {} leaving {} for {}".format(self.sim.now(), self.name, here, dest)
            yield hold, self, timeTo(self.accel, self.maxV, here.distanceTo[dest])
            # arrive at next station
            here = dest
            print "{:.1f}s: {} at {}".format(self.sim.now(), self.name, here)
            yield hold, self, here.arrive(self)

    def getOff(self, num):
        if self.p >= num:
            print "  {} passengers got off".format(num)
            self.p -= num
        else:
            num = self.p
            print "  train is empty - only {} passengers got off".format(num)
            self.p = 0

    def getOn(self, num):
        if (self.maxP is None) or (self.p + num <= self.maxP):
            print "  {} passengers got on".format(num)
            self.p += num
        else:
            num = self.maxp - self.p
            print "  train is full - only {} passengers got on".format(num)
            self.p = self.maxp

class TrackNode(object):
    def __init__(self, name, delay=5.0):
        self.name = name
        self.delay = delay
        self.distanceTo = {}
    def arrive(self, train):
        pass
    def __str__(self):
        return self.name

class Station(TrackNode):
    def arrive(self, train):
        train.getOff(randint(1,15))
        train.getOn(randint(1,15))
        return self.delay

class Switch(TrackNode):
    def arrive(self, train):
        print("  switching tracks")
        return self.delay

class SampleRailroad(Simulation):
    def run(self, maxTime=100.0):
        self.initialize()
        # create places
        x = Switch("switch x", 20.0)
        A = Station("Station A", 24.0)
        B = Station("Station B", 27.0)
        C = Station("Station C", 25.0)
        y = Switch("switch y", 18.0)
        # distances between places
        x.distanceTo[A] = 50.0
        A.distanceTo[B] = 5000.0
        B.distanceTo[C] = 2000.0
        C.distanceTo[y] = 80.0
        y.distanceTo[C] = 80.0
        C.distanceTo[B] = 2000.0
        B.distanceTo[A] = 5000.0
        A.distanceTo[x] = 50.0
        # set up first train
        sf = Train("Santa Fe 219", self)
        self.activate(sf, sf.roll(cycle([A,B,C,y,C,B,A,x])), at=0.0)
        # set up second train
        cn = Train("Canadian National 41", self, maxPassengers=200)
        self.activate(cn, cn.roll(cycle([C,B,A,x,A,B,C,y])), at=5.0)
        # start simulating!
        self.simulate(until=maxTime)

def main():
    rr = SampleRailroad()
    rr.run(800.0)

if __name__=="__main__":
    main()