On Tue, 20 Nov 2001, Marcin 'Qrczak' Kowalczyk wrote:

> Wed, 21 Nov 2001 01:35:53 +0300 (MSK), malc <malc@pulsesoft.com> pisze:
> 
> >> let use_refs' time =
> >>   let rif = ref 0 in
> >>   for i = 0 to time - 1 do rif := !rif + 1 done;
> >>   !rif
> > let use_refs' time =
> >   let rif = ref 0 in
> >   for i = 0 to pred time do incr rif done;
> >   !rif
> 
> The generated code is exactly the same :-P
Precisely ;) It's more "camlish" in my opinion, which is why i couldnt
resist posting it.

> 
> But none of the following produces optimal code (judging by looking
> at the generated code):
> 
> let current = ref 0
> let next1 () = let x = !current in incr current; x
> let next2 () = let x = !current in current := x + 1; x
> let next3 () = incr current; !current
> let next4 () = let x = !current + 1 in current := x; x
> 
> Moreover, making the counter private on the declaration level:
> 
> let next1 =
>   let current = ref 0 in
>   fun () -> let x = !current in incr current; x
> 
> yields worse code, even though the semantics is the same.
Semantics are not the same here: first 'current' is module global and
statically allocated in module storage. Second 'current' is lexically
bound.

When i was playing with Doug Bagley's "Great Computer Language Shootout"
http://www.bagley.org/~doug/shootout/bench/sumcol/ , i found that no
matter how hard i try to invent some ingenious summing function caml
generated code leaves a lot to be desired. (I think this holds for any
use of global references).

P.S. When playing with those functions you might find -dcmm option
useful.

-- 
mailto:malc@pulsesoft.com

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