On Sat, 2005-01-29 at 21:09 +0100, J�rgen Hermanrud Fjeld wrote:
> Since BitC is targeted to be fast, I wondered how you plan to handle
> arrays, and the compilation of methods on arrays. 
> This might be of topic for the purpose of BitC, but it is certainly
> important for speed and safety of matrix multiplication or other
> operations on arrays. 
> The work shape analysis for efficient code generation in the research
> language FISh [1] does demonstrate very good results in comparison to C,
> and has a theoretical foundation. 
> Have you considered such approaches, and if, what where your
> considerations?

This is well outside the class of problems that we are considering. I
think that the best response on this topic is to suggest that BitC is
not, over the long haul, a frozen thing. If people want to take up other
research foci based on what we are doing, that would be wonderful, and
we would encourage it as best we can.

Much of the problem of fast floating point processing is a matter of
highly aggressive optimization. One of the things the we expressly are
NOT pursuing in the BitC project is aggressive optimization. The good
news is that the BitC framework should lend itself to this if other
people want to pursue it.

> The O'Caml type system does not regard array size as a statically
> checked property, neither does the extensional polymorphism. 

Experience in the '70s with Pascal strongly suggests that considering
array size as part of time is very problematic. In particular, it is a
problem when declaring formal parameters on procedures that one would
like to have be more generally applicable. Later versions of Pascal
introduced various kludgy workarounds.

My opinion, for whatever it is worth, is that there are times when the
size of a vector *is* part of its type, and times when it is not, and it
should be feasible to declare the vector accordingly.


shap

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