"ocamlopt" does optimize data representation: for example, it can unbox
floats into registers, or into arrays of floats. However, there is a
tradeoff between such optimizations and efficiency: when you do too much
representation optimisation, you might end up performing a lot of tests
because a given type can be represented in multiple formats, and
performing a lot of transformations between the representations,
especially as the FFI (Ocaml interface to C) specifies the
representation of data.

Of course, I am not saying it is not possible to do better: it requires
a lot of energy, the compiler code becomes more complex, and the
improvement on speed is not clear.

--Fabrice


Sylvain Le Gall wrote, On 05/04/2010 03:42 PM:
> On 04-05-2010, rossberg@mpi-sws.org <rossberg@mpi-sws.org> wrote:
>> "Sylvain Le Gall" <sylvain@le-gall.net>:
>>> This is not about optimized compiler in this case but about data
>>> representation. Even if you use an optimized compiler (which is not
>>> really the case with ocamlopt), you won't change datastructure
>>> representation to optimize.
>> What do you mean? There is no reason in general why a compiler cannot
>> optimize data representations, and some do in cases like this.
>>
> 
> Anyway, if it comes to data alignement and things like that, the
> compiler should optimize data representations. But in this case, I
> really don't think we are talking about data alignement.
> 
> Regards,
> Sylvain Le Gall
> 
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-- 
Fabrice LE FESSANT
Chercheur, Equipe ASAP
(As Scalable As Possible)
http://www.lefessant.net/

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Parc Orsay Université
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