Hello,

In tried not getting into this discussion but I could not resist
commenting on the following:

Jacques Garrigue wrote:
 >...
 > ... There are applications for that (ray tracing is
 > one), but this is not the kind of needs most people have.
 >...

As with most technology people will or will not use something
according to their perceived effort/pleasure to learn/use
something and the advantages it is supposed to bring.

Put it another way; if parallel/concurrent programming could be
easily used with a minimum of effort then I believe "most people"
would use it simply because it is available.

In other words the (ready) availability of (multi-core PCs and)
parallel computing support (in Ocaml) will certainly influence the
number of people that will take advantage of it simply because it
is available (confer with e-mails on this thread).

 >...
 > If I tell you that you just have to modify a bit your program to get a
 > near linear speedup, then it looks great. But in practice it is rather
 > having to rethink completely your algorithm, to eventually get a
 > speedup bounded by bandwidth, and starting from a point lower than the
 > original single thread program.
 >...

Rethinking our application/algorithmic structure may not be a real
deterrent. An application does not require parallel/concurrent
processing everywhere. It is really a question of identifying where
and when this is useful. Much like selecting the most "appropriate" 
data-structure for any application. It's not an all or nothing
proposition.

My 2 cents.

Regards,
Hugo F.