Still too slow

[John Posner]

On 1/30/2010 6:08 PM, elsa wrote:
> Hello again,
>
> Thanks for the tips r.e random.ranint(). This improved matters
> somewhat, however my program is still too slow. If anyone has any
> further tips on how to speed it up, they would be much appreciated!
>
> So, I'm calling evolve(L,limit) from the interactive prompt. L is
> initally [[100],['NA']]. Ideally limit would be 10^7.
>
> Here is my program:
>
> import random
> n=100
>
> def evolve(L,limit):
> 	global n
> 	while n<limit:
> 		evnt = event()
> 		if evnt!="None":
> 			ind = chooseInd(L,n)
> 			action(evnt,L,ind)
>
> def chooseInd(L,n):
> 	choiceSum=0
> 	index=0
> 	choice = random.randint(1,n)
> 	while choiceSum<  choice:
> 		choiceSum+=L[index][0]
> 		index +=1
> 	return (index-1)
>
> def event():
> 	choice = random.random()
> 	if choice<= .3:
> 		event='b'
> 	elif choice<= .4:
> 		event ='d'
> 	elif choice<= .5:
> 		event = 'm'
> 	else:
> 		event = 'None'
> 	return event
>
> def action(event, L, index):
> 	global n
> 	if event == 'b':
> 		L[index][0]+=1
> 		n +=1
> 	elif event == 'd':
> 		L[index][0]-=1
> 		n -=1
> 	elif event == 'm':
> 		L.append([1,index])
> 		n +=1
>
>
> thanks in advance,
>
> Elsa.

Elsa,

1. You changed the subject line from "For loop searching takes too 
long!" to "Still too slow". This causes newsreader programs to start a 
new discussion thread, which makes life difficult for people who need to 
refer back to previous messages. Please don't change the subject line 
any more.

2. You provided a very clear description of your original question:

   Now, what I need to do is randomly choose one myList[i], however the
   distribution of my random choice needs to be proportional to the
   values of myList[i][0].

This description should be the doc string for the chooseInd() function 
-- for example:

   def chooseInd(L,n):
       """
       randomly choose one L[i], so that the distribution
       of choices is proportional to the values of L[i][0]
       """

It is not clear (to me, anyway) what the other functions are trying to 
accomplish. So please add a doc string to each of these functions, with 
descriptions of similar clarity. This will help us a lot. And it will 
help you, too, if you return to the code after a few days/weeks/months 
of directing your attention elsewhere.

3. Please provide a *complete* transcript of an interactive session that 
exercises this code.

Tx,
John