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Re: LuaJIT2 performance for number crunching

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KHMan wrote:
> "this is a major advance in computer science because"
> 
> Yes, you should try sending a paper somewhere and see if they let
> you keep such claims.
This is hyperbole, for sure.
> The HP Dynamo trace compiler was doing
> faster-than-compiled-original speeds years ago.
Oh no, not that again. Everybody is repeating that claim, but
nobody has actually bothered to read the paper! Here's my standard
rant on that:
 This is a common misinterpretation of the Dynamo paper: they
 compiled their C code at the _lowest_ optimization level and
 then ran the (suboptimal) machine code through Dynamo. So there
 was actually something left to optimize.
 Think about it this way: a 20% difference isn't unrealistic if
 you compare -O1 vs. -O3.
 But it's completely unrealistic to expect a 20% improvement if
 you'd try this with the machine code generated by a modern
 C compiler at the highest optimization level.
 Claiming that JIT compilers outperform static compilers, solely
 based on this paper, is utter nonsense.
 
 [In fact a very good JIT compiler _can_ outperform a very good
 static compilers under specific, but rare, circumstances. But
 this has more to do with extra specialization opportunities at
 runtime and is completely unrelated to this paper.]
--Mike

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