RE: [Dev-C++] Efficiency

[Williams, T. W. <TIM...@sa...>]

Good grief! I concur too.  Let me explain my point a bit clearer here:
o I assumed he was constrained to solving the problem recursively.
o I made that assumption because a frequently used method of teaching
recursion includes using a simple problemset, ie. fibonacci.
o This is mainly because once situations are complex enough to need
recursion, if a person doesn't already know it then they are stuck, for
instance learning how to implement a B+Tree and traversing it is a good time
to *already* know recursion.  
o If all he wanted was a fast way to compute the fib sequence, he probably
should have asked "how can I make this funcion more efficient" rather than
"how can I make this recursive function more efficient"  then I would have
been less likely to make assumptions about his constraints. 
o He could clear it up by letting us know what his constraints were or were
not.

I'm not arguing for a recursive solution in this case if he's doing it for
any *real* purpose, although I must say I didn't see any significant
performance difference for any relatively small n.  Just out of curiousity
how did you initially learn recursion?  I'm guessing it wasn't implementing
a tree structure for the first time, right?  Probably the fib sequence, I
think it's most ever intro to CS book out there. 

--tim


> -----Original Message-----
> From: Ioannis Vranos [mailto:no...@ya...]
> Sent: Tuesday, November 13, 2001 2:52 PM
> To: Dev-C++
> Subject: RE: [Dev-C++] Efficiency
> 
> 
> I astrongly agree with St0fF here. Recursion has time cost due to
> continuous function calls and space cost because of the storage of the
> function calls in the stack (or in the automatic storage if 
> you prefer).
> This applies to fibonacci too.
> 
> 
> Ioannis
> 
> * Ioannis Vranos
> * Programming pages: http://www.noicys.f2s.com
> * Alternative URL: http://run.to/noicys
> 
> 
> > -----Original Message-----
> > From: dev...@li... 
> > [mailto:dev...@li...] On Behalf 
> > Of St0fF 64
> > Sent: Tuesday, November 13, 2001 5:48 PM
> > To: DevCPP; Williams, Timothy W.
> > Subject: Re: [Dev-C++] Efficiency
> > 
> > 
> > Hi!
> > As I said, iteration speeds it all up because no unneccessary 
> > Stacking,
> > meaning: push return address, recursive recall, push return 
> > address, recursive recall, ... , recursive recall, return 
> > solution, pop return address, return solution, ... , pop 
> > return address, return solution, finished. This is the 
> > negative effect of recursion.  In the iterative version we do 
> > counting instead of accessing the stack.  The dealing with 
> > return addresses and the stack is not used in iteration.  
> > Thats why it is faster. St0fF.
> 
> 
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