RE: [Caml-list] 32 bit floats, SSE instructions

["Brandon J. Van Every" <vanevery@indiegamedesign.com>]

Nicolas Cannasse wrote:
>
> The main problem with float's - whatever if they are 32 or 64
> bits - is
> their boxing . OCaml runtime value representation is
> efficient but a float -
> even 32 bits - cannot be carried in a register as it could be in C.
> (actually some unboxing can be performed locally by ocamlopt). This is
> mainly because OCaml is an high-level language, with a
> garbage collector,
> and so needs to keep the track of what is being allocated in
> an efficient
> way. Did you imagine having an higher level programming
> language for free ?

Sounds like someone decided to pay for efficiency with uncleanliness.
That is not the only way to pay for things.  One could instead, for
instance, pay with a more difficult implementation.

> So yes maybe OCaml is not the best language to perform floating point
> operations, although the cost of boxing is actually quite
> small compared to
> the power of implementing easily more efficient algorithms.

The old "ah, let the algorithm deal with it!" saw.  Yawn.

> That's why you
> should perform batched operations in C - using 32bits float
> if you want -
> and manipulate your 64-bits vectors on the Ocaml side.

Since when are all numeric problems batch problems?  Batching in C is
only practical when problems are simple and highly repetitive.  What a
3D graphics guy often really wants, is the ability to inline a bunch of
function "pipeline" stages into one fairly complicated function.  The
transitions between pipeline stages should all be optimized together.


Cheers,                         www.indiegamedesign.com
Brandon Van Every               Seattle, WA

"We live in a world of very bright people building
crappy software with total shit for tools and process."
                                - Ed Mckenzie


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