Re: st: Slowing process when running a program with multiple nested loops

[David Kantor <kantor.d@att.net>]

At 11:44 AM 1/14/2013, Ly Tran wrote:
> I wrote a program, in which there are multiple nested loops (because
> there are 7 parameters, each could receive one of 5-7 different
> values).
> The program runs really fast at first, but starts slowing down when
> getting to around the 300th iteration. By 500th iteration, it slows
> down significantly, and I could never wait until the whole thing ends
> (the longest I have waited was 2 hours).
>
> Does anybody know what could be the cause of this slowing down? "Set
> memory" doesn't seem to help.
>
> Any idea will be much appreciated.
> thank you.

I think that most of would agree that we would need to see your code 
to be able to say what the problem is.
Meanwhile, did you mean that the loops are nested to a depth of 7? 
That's unusually deep.

Just generally speaking, with loops, there are often actions that are 
placed inside that don't need to be there; they can be moved "up" or 
"out" (sometimes requiring a bit of modification) so as to not be 
done multiple times unnecessarily.
From what you describe, it seems that the work done in each 
iteration is accumulating; each iteration does a bit more work than 
the previous. There may be some unnecessary repetition as described 
above. But it also seems that there is something that grows and gets 
dragged along with each iteration -- again possibly unnecessarily. 
This is analogous to a cumulative song, such as "The Twelve Days of 
Christmas"; the 12th verse is much longer than the first.

On the other hand, does the true complexity of the task grow with 
each iteration? Do you expect the 300th iteration to naturally be 
more complex to perform than the first?

Show us your code if you want more help.

HTH
--David

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