POV-Ray: Newsgroups: povray.text.tutorials: Tips & tricks: How speed-up calculations in loops - part II: Re: Tips & tricks: How speed-up calculations in loops

POV-Ray : Newsgroups : povray.text.tutorials : Tips & tricks: How speed-up calculations in loops - part II : Re: Tips & tricks: How speed-up calculations in loops - part II		Server Time 19 Jan 2025 05:10:05 EST (-0500)

From: Jonathan Wooldridge
Date: 25 May 2002 16:29:51
Message: <3ceff43f@news.povray.org>

> >
> >  One of the oldest tricks known, loop unrolling, should speed up as
well.
>
> Nobody likes unrolling 1000000 iterations ;-)
>

Loop unrolling isn't about coding every iteration, for that very reason.
Doing an unroll of a loop reduces the number of passes for the loop.

If you have a million iterations, then there is some overhead for each of a
million passes through the loop.
You can reduce this by a factor of ten, by unrolling the loop ten times
within the loop.

Try timing this:

// Unrolled Script
#local C=1000000;
#while(C)
#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#local C=C-1;
// Do stuff with C

#end

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