[Haskell-cafe] Can't Haskell catch upwith Clean's uniqueness typing?

[John Meacham]

On Wed, Dec 07, 2005 at 04:38:19PM +0300, Bulat Ziganshin wrote:
> may be, John Meacham can say something about it? his JHC compiler uses
> region analysis to avoid garbage collection - may be these techniques
> has something in common?

By the time jhc makes any decisions regarding memory management, the
code has already been transformed into a first order, strict, imperative
language (but with stronger types than normal and in a monad) so I am
not sure how much they would have in common.

But there definitely are higher level optimizations that achieve similar
things, update avoidance being a particular one as it collects pretty
much exactly the info we want, when a node will only be referenced once.
GHC has some very advanced algorithms for this sort of thing and I
believe from first glance they will do a better job than the clean
system. 

The update analysis info in jhc is not propegated all the way to the
back end, the grin compiler does do a separate analysis to recapture
this type of info after various transformations. I found it somewhat
tricky to maintain the annotations all the way through various
optimizations so I recalculate it (and perhaps get better results on the
simpler program).

However figuring out a way to propagate  that info would be vital if we
wanted user supplied region annotations, which several papers have said
can be very beneficial. It is not clear at all what they would look like
in a lazy language though since your run-time stack does not follow your
program structure. (I'm open to ideas...)

        John

-- 
John Meacham - ⑆repetae.net⑆john⑈