Re: The Why's of Loop Unrolling

Chris,

You are correct, JS is invariably translated into compiled commands but
since it's not a one to one translation, and there's a lot of optimization,
rearrangement, etc that happens between JS being interpreted and executed at
machine level, low-level optimization like loop unrolling does little.  What
does make a difference is lowering the number of operations / loop.  Even
when writing assembly, loop unrolling begins to make sense when the overhead
for the loop iteration and branching is close to the time the loop
instructions take.  So it makes a lot more difference when you can slim down
the # of instructions / loop.

This is what I saw on that page (without going back and looking at all of
the examples again) is the timing compared two different things .. in the
faster examples, there were fewer # of instructions / loop.


-- Ben V. Y.



On 11/10/06, Chris <[email protected]> wrote:
>
>   Hi BY,
> > Since JS is interpreted, not compiled
> But again, it's ultimately interpreted into compiled commands. For
> conclusive results you need merely test the approach - and as you can
> see on this page the results are a significant speed increase.
>
> > The link you reference actually accomplishes
> > gains by reducing operations / loop (using variables with precalc'd
> > values).
> You have to scroll to the bottom for the loop-unrolling techniques. Many
> are presented on the page.
>
>  
>


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