Hello,

Here is the latest Caml Weekly News, week 11 to 18 February, 2003.

1) CamlAgent 0.1
2) Optimizing false polymorphic local functions
3) Any idea about Ocaml 3.07 release date?

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1) CamlAgent 0.1
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SooHyoung Oh announced:

CamlAgent version 0.1
 - Ocaml applications for Microsoft Agent: http://www.microsoft.com/msagent
 - You can see parallel and sequential agent play.
 - Home: http://www.taglib.co.kr/ocaml/camlAgent.html

Requirements:
 * MS agent characters
    - In download page, you can find
       = MS Agent core components
       = MS Agent character files: Genie, Merlin, Peedy, Robby
 * MS Visual C++ Compiler / MS Visual Studio
    - I tested on MS Visual Studio .Net.
 * Ocaml 3.06
 * Lablgtk 1.2.5 - you can source and binary in
  http://wwwfun.kurims.kyoto-u.ac.jp/soft/olabl/lablgtk.html
 * camlidl 1.04
 * camlidl 1.04 patch - I made some patches for MS agent ONLY.

Demos:
 - move: moveSquare, moveCircle
 - hello: parallel, sequential play

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2) Optimizing false polymorphic local functions
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Pascal Zimmer asked and Xavier Leroy answered:

> The other day, I ran into a significant speedup improvement.
> Here is a simpler (and artificial) version:
> 
> let min_list l =
>  let rec loop mini = function
>     [] -> mini
>   | (x::r) -> loop (if x <= mini then x else mini) r
>  in loop max_int l;;
> 
> This function computes the minimal element of an int list. Note however
> that the inner local function "loop" is polymorphic.
> 
> Now consider the slightly different version where "loop" is forced into
> a monomorphic function:
> 
> let min_list l =
>  let rec loop (mini:int) = function
>     [] -> mini
>   | (x::r) -> loop (if x <= mini then x else mini) r
>  in loop max_int l;;
> 
> On my computer in native code, the speedup is really significant: more
> than 6 times faster (OK this example was built on purpose...). The
> reason is that in the first case, the operator <= is replaced by a call
> to the internal polymorphic compare_val function, whereas is the second
> case a direct comparison between integers is performed.
> Note also that if you replace the "if" statement by "min x mini", you
> don't get any speedup because the polymorphic function "min" is called
> in any case.
> 
> I suspect there are other cases in which the compiler can produce a
> better code when it knows more precisely the types involved. 

Yes: besides comparisons, array and bigarray accesses can be compiled
more efficiently if the exact types of the data are known statically.

> So my question is: would it be possible to help him in this way by
> enforcing the type checker to infer a monomorphic type in such  
> situations ? By "such situations", I mean: local polymorphic
> functions that are used in exactly one monomorphic setting
> afterwards. Of course, this is not desirable for global functions,
> since it may break the calculus; but for local functions, it should 
> be of no harm since we know all the places where they are used, and
> it would not change the type of the wrapper, thus being transparent
> for the user...
> Any comment ?

The following paper formalizes exactly this idea, and gives a type
inference algorithm that avoids unecessary polymorphism like you suggest:

  http://citeseer.nj.nec.com/bjorner94minimal.html

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3) Any idea about Ocaml 3.07 release date?
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Alessandro Baretta wondered and Xavier Leroy answered:

> I am wondering whether the Ocaml team has any idea about the 
> next release date. Any ideas?

Certainly not before late April, and hopefully no later than early July.
I can't be any more precise than this at the moment.

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Alan Schmitt