On 01/11/2007, Jecel Assumpcao Jr <jecel at merlintec.com> wrote:
> Joshua Gargus wrote:
> > Thanks for this interesting list of your relevant work.  I look
> > forward to any other thoughts that you could add to this thread, in
> > particular to provide a reality-check where your real-world
> > experience disagrees with my theoretical understanding :-)
>
> Sadly, my practical experience is far more limited than it should be,
> given all the years I have spent on this, since often a project would be
> abandoned after only preliminary results in favor of a "much better"
> one.
>
> One thing that I haven't tried yet is making messages to futures return
> new futures instead of blocking (which I understood from this dicussion
> to be the E way). I had thought about it but imagined it might lead to
> ever growing graphs of pending messages with no actual work being done.
> I see now that in practice the overhead might be comparable to what my
> deadlock detector had. This would probably also make my "tail send"
> optimization mostly useless, which is a good thing.
>
> In all my projects I took a very conservative path regarding blocks: I
> simply defined "." as a kind of barrier where all previous instructions
> must finish before any of the following instructions can be started.
> Since I was getting a lot of parallelism even with this I didn't worry
> too much about it and this allowed code like this to work just fine:
>
> | a |
> a := 1.
> 1 to: 20 do: [ :i | a := a + i ].
> a := a - 1.
> 1 to: 20 do: [ :x | a := a - x ].
> ^ a
>
> Having "." as a barrier is unecessary in the code below, but at least
> the results will be correct even if at a much reduced performance:
>
> | a b |
> a := (1 to: 20) collect: [ :i | i * i ].
> b := (1 to: 20) collect: [ :x | x + 7 ].
> ^ a + b
>
> It isn't very hard for the compiler to know which is the case for each
> example.
>

Yes, without barriers the following code simply will not work as desired:

| a b |
a := (1 to: 20) collect: [ :i | i * i ].
Interval removeSelector: #collect: .
b := (1 to: 20) collect: [ :x | x + 7 ].
^ a + b


-- 
Best regards,
Igor Stasenko AKA sig.