[Tutor] Simplicity vs. Speed

[Roeland Rengelink]

Hi Phil,

> Phil Bertram wrote:
> 
> Hi all,
> 
> I have a program that tracks scores and the results from a sports
> competition. Points are given for people who pick the winning team.
> 
> The data is held classes that have attributes that are lists of lists
> of lists etc.
> 
> I did it this way because I imagined that it would be faster as I
> would only have to iterate through 10 items rather than 100
> 
> eg.
> 
> Week1 = ['Game1', ........ 'Game10']
> Week2 = ['Game11',.........'Game20] etc etc
> 
> The above example is very simplified, data levels go 3 or 4 deep and
> so things sometimes become a little unclear.
> 
> I'm now thinking that it is better to keep data in just a single list
> and filter the list each time I need to do an operation.
> 
> eg
> 
> Games = ['Game1',..................'Game100']:
>     for game in games:
>         if game.week == 'Week1':
>             do something
> 
> Or would using the 'filter' function be more or less efficient ?
> 

I really don't know. I can guess, of course, but my guess is less
reliable than your measurement. 

>
> Would you suggest that a new programmer just keep things simple so as
> to get the code working bug free, and not worry at all about speed ?
> 

Yes! 

Especially since simplest is usually also fastest.

First get it working.
Does it work fast enough?
(fast enough is totally subjective and the only relevant criterium)
if yes:
    leave well enough alone
if no:
    profile!
    (measurement is the only objective criterium)
    optimize the parts you _know_ are slow.
    	- optimize by redisigning your algorithms
        - keep measuring
    if your best algorithm is still too slow
	- rewrite in C

In my experience slow code falls in one of three categories.

1. slow, but not slow enough to be worth the trouble
   - I don't care if something runs in 0.1 second rather than 1 second
2. so slow that it's not worth the trouble.
   - I don't care if something runs in 1 hour rather than 10 hours
3. Hmm, maybe
   - I may care if something runs in 1 second rather than 10 seconds

3 is, of course, the rarest category.

Having made the obligatory point about only rewriting for optimization
iff:
1. you are sure it is necessary, and
2. you have reaon to believe it may help

let me add that a nagging feeling that another approach would be more
elegant/shorter/neater or simply feel better is a perfectly good reason
to rewrite your code. The nice thing is that if your feeling happens to
be right, your code will usually become faster too.

Hope this helps,


-- 
r.b.rigilink@chello.nl

"Half of what I say is nonsense. Unfortunately I don't know which half"