Re: Embedded languages based on early Ada (from "Re: Preferred OS, processor family for running embedded Ada?")

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sat, 03 Mar 2007 19:31:24 +0100, Pascal Obry wrote:

> Dmitry A. Kazakov a �crit :
> 
>> The idea (of PAR etc) is IMO quite opposite. It is about treating
>> parallelism rather as a compiler optimization problem, than as a part of
>> the domain. In the simplest possible form it can be illustrated on the
>> example of Ada's "or" and "or else." While the former is potentially
>> parallel, it has zero overhead compared to sequential "or else." (I don't
>> count the time required to evaluate the operands). If we compare it with
>> the overhead of creating tasks, we will see a huge difference both in terms
>> of CPU cycles and mental efforts.
> 
> I don't buy this :)

Well, maybe I don't buy it too... (:-)) Nevertheless, it is a very
challenging and intriguing idea.

> You don't have to create tasks for every computations.

(On some futuristic hardware tasks could become cheaper than memory and
arithmetic computations.)

> You put in place a writer/consumer model. A task prepare
> the data and put them into a list (protected object) and you have a set
> of tasks to consume those jobs. This works in many cases, requires only
> creation of tasks once (not as bad as OpenMP which creates threads for
> parallel computations).

Ah, but publisher/subscriber framework is itself a solution of some
problem, which is not a domain problem. If you had a distributed middleware
you would not care about publishers and subscribers. You would simply
assign/read a variable controlled by the middleware. Interlocking,
marshaling whatsoever would happen transparently.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de