Re: LuaJIT2 performance for number crunching

[Philippe Lhoste <PhiLho@...>]

On 16/02/2011 17:16, Mike Pall wrote:
> Rule #437: Never hoist out constants (if possible)!
>
> Always write constants inline, otherwise they are treated as
> variables, which generates worse code. And, yes, even plain Lua is
> able to fold 1/5 into a constant. It's important to write these
> unambiguously -- FP arithmetic is not associative!

Good to know, but bad programming practice from a formal point of view. :-)
I always recommend to beginners in programming to replace magic numbers with constants, 
for readability and consistency. I understand that speed optimizations sometime have to 
break these nice rules (like manual loop unrolling and such).

It would be nice, perhaps, if Lua had a way to define true, efficient constants.
(Yes, that's another bag of worm. Perhaps if someone want to comment on my remark, a new 
thread should be started...)

--
Philippe Lhoste
--  (near) Paris -- France
--  http://Phi.Lho.free.fr
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