DESCRIPTION

Students:  Please keep in mind the OMSI rules.  Save your files often,
make sure OMSI fills your entire screen at all times, etc.  Remember
that clicking CopyQtoA will copy the entire question box to the answer
box.

In questions involving code which will PARTIALLY be given to you in the
question specs, you may need add new lines.  There may not be
information given as to where the lines should be inserted.

MAKE SURE TO RUN THE CODE IN PROBLEMS THAT INVOLVE CODE!

QUESTION 

(20 pts) Fill in the blank with Python terminology: The second argument
of activate() is a/an _____________________.

QUESTION

(20 pts) Fill in the blanks:  In SimPy, a thread's turn ends when
_____________________.  With Python threads, a thread's turn ends when
either _______________________ or ________________________.

QUESTION

(20 pts) Consider the server code on pp.91-92.  In some cases, omission of
a line (individually) would result in the program running forever.
State the line numbers of such lines.  (List them in ascending numerical
order, please.)

QUESTION -ext .py -run 'python omsi_answer4.py'

(40 pts) Add code to the machine repair SimPy example so that it prints out
the mean down time.  For full credit, modify only code in main().  (Note
our point that "the leftover actions" near the end of the simulation
don't matter.)

from SimPy.Simulation import *
from random import Random,expovariate,uniform

class G:  
   Rnd = Random(12345)
   RepairPerson = Resource(1)

class MachineClass(Process):
   TotalUpTime = 0.0  
   NRep = 0  
   NImmedRep = 0  
   UpRate = 1/1.0  
   RepairRate = 1/0.5  
   NextID = 0  
   NUp = 0  
   def __init__(self):
      Process.__init__(self)  
      self.StartUpTime = 0.0  
      self.ID = MachineClass.NextID   
      MachineClass.NextID += 1
      MachineClass.NUp += 1  
   def Run(self):
      while 1:
         self.StartUpTime = now()  
         yield hold,self,G.Rnd.expovariate(MachineClass.UpRate)
         MachineClass.TotalUpTime += now() - self.StartUpTime
         MachineClass.NRep += 1
         if G.RepairPerson.n == 1:
            MachineClass.NImmedRep += 1
         yield request,self,G.RepairPerson
         yield hold,self,G.Rnd.expovariate(MachineClass.RepairRate)
         yield release,self,G.RepairPerson

def main():
   initialize()  
   for I in range(2):
      M = MachineClass()
      activate(M,M.Run())
   MaxSimtime = 10000.0
   simulate(until=MaxSimtime)

if __name__ == '__main__':  main()