我目前正在学习数据结构和算法。 我发现Interactive python在打印机模拟python程序中如何计算waittime?
from pythonds.basic.queue import Queue
import random
class Printer:
def __init__(self, ppm):
self.pagerate = ppm
self.currentTask = None
self.timeRemaining = 0
def tick(self):
if self.currentTask != None:
self.timeRemaining = self.timeRemaining - 1
if self.timeRemaining <= 0:
self.currentTask = None
def busy(self):
if self.currentTask != None:
return True
else:
return False
def startNext(self,newtask):
self.currentTask = newtask
self.timeRemaining = newtask.getPages() * 60/self.pagerate
class Task:
def __init__(self,time):
self.timestamp = time
self.pages = random.randrange(1,21)
def getStamp(self):
return self.timestamp
def getPages(self):
return self.pages
def waitTime(self, currenttime):
return currenttime - self.timestamp
def simulation(numSeconds, pagesPerMinute):
labprinter = Printer(pagesPerMinute)
printQueue = Queue()
waitingtimes = []
for currentSecond in range(numSeconds):
if newPrintTask():
task = Task(currentSecond)
printQueue.enqueue(task)
if (not labprinter.busy()) and (not printQueue.isEmpty()):
nexttask = printQueue.dequeue()
waitingtimes.append(nexttask.waitTime(currentSecond))
labprinter.startNext(nexttask)
labprinter.tick()
averageWait=sum(waitingtimes)/len(waitingtimes)
print("Average Wait %6.2f secs %3d tasks remaining."%(averageWait,printQueue.size()))
def newPrintTask():
num = random.randrange(1,181)
if num == 180:
return True
else:
return False
for i in range(10):
simulation(3600,5)
这段代码可以请别人解释怎样的waitingtimes.append(nexttask.waitTime(currentSecond))计算waitime为currentsecond。 对于那个特定的currentsecond,它不会为零。 同样根据模拟,每180秒有一个新的任务,但它在同一个当前的秒中被排队和出队。 因此,printqueue在任何特定的时间总是空的,还是它?
请帮助...
谢谢,这是一个明确的解释...非常感谢! – 2014-11-15 13:11:54