From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: PAR (Was: Embedded languages based on early Ada)
Date: Thu, 8 Mar 2007 11:06:33 +0100
Date: 2007-03-08T11:06:33+01:00 [thread overview]
Message-ID: <j40y29mf7uzf$.r230fya6cy07.dlg@40tude.net> (raw)
In-Reply-To: ur6s03j1c.fsf@STRIPCAPStelus.net
On Wed, 07 Mar 2007 20:17:40 GMT, Ray Blaak wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>> Why is it bad programming? Consider this:
>>
>> declare
>> Sum : Numeric := 0.0;
>> begin in parallel
>> Sum := Sum + Integrate (Series (1..N);
>> Sum := Sum + Integrate (Series (N+1..2*N);
>> Sum := Sum + Integrate (Series (2*N+1..3*N);
>> ...
>> end;
>
> This is also bad programming. The assignments are in parallel, overwriting
> each other, and it is not clear in a given statement what initial value of Sum
> is being worked with.
That is what PAR have to define.
> As shown, this example looks like it is after a sequential summation, and that
> contradicts what the concurreny execution will do.
No, it is a concurrent incrementing of an atomic object Sum. An equivalent
should be
protected type Accumulator is
procedure Increment (By : Numeric);
end Accumulator;
>> If so, then what would be the contribution of PAR?
>
> A syntactic convenience to tediously writing task bodies explicitly. Consider
> the immediate example above written out explicitly.
In this form it barely would be convenient.
> The short answer is nothing. PAR spawns some tasks and waits for them to
> complete, nothing more or less.
>
> Parallel programing is hard. Relying on implicit optimization is what I
> recommend against, since in general it is a fiendishly complex problem as to
> how to sort out the interdependencies.
>
> Keep PAR simple, and leave it to the programmer to figure out the
> synchronization.
If the programmer should figure out the synchronization, then we are back
where we started before fine-granularity. See Pascal's example.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2007-03-08 10:06 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-23 0:59 Preferred OS, processor family for running embedded Ada? Mike Silva
2007-02-23 4:41 ` Steve
2007-02-23 16:00 ` Mike Silva
2007-02-23 4:49 ` Jeffrey R. Carter
2007-02-23 13:13 ` Mike Silva
2007-02-23 13:56 ` Stephen Leake
2007-02-23 14:10 ` Mike Silva
2007-02-24 10:45 ` Stephen Leake
2007-02-24 12:27 ` Jeffrey Creem
2007-02-24 22:10 ` Dr. Adrian Wrigley
2007-02-25 13:10 ` roderick.chapman
2007-02-25 17:53 ` Jeffrey R. Carter
2007-02-25 15:08 ` Stephen Leake
2007-02-28 17:20 ` Embedded languages based on early Ada (from "Re: Preferred OS, processor family for running embedded Ada?") Colin Paul Gloster
2007-03-01 9:18 ` Jean-Pierre Rosen
2007-03-01 11:22 ` Dr. Adrian Wrigley
2007-03-01 11:47 ` claude.simon
2007-03-01 13:57 ` Dmitry A. Kazakov
2007-03-01 18:09 ` Ray Blaak
2007-03-02 11:36 ` Dr. Adrian Wrigley
2007-03-02 16:32 ` Dmitry A. Kazakov
2007-03-03 0:00 ` Dr. Adrian Wrigley
2007-03-03 11:00 ` Dmitry A. Kazakov
2007-03-03 11:27 ` Jonathan Bromley
2007-03-03 12:12 ` Simon Farnsworth
2007-03-03 14:07 ` Dr. Adrian Wrigley
2007-03-03 17:28 ` Pascal Obry
2007-03-03 18:11 ` Dmitry A. Kazakov
2007-03-03 18:31 ` Pascal Obry
2007-03-03 20:26 ` Dmitry A. Kazakov
2007-03-03 21:28 ` Dr. Adrian Wrigley
2007-03-03 22:00 ` Pascal Obry
2007-03-03 13:40 ` Dr. Adrian Wrigley
2007-03-03 15:26 ` Jonathan Bromley
2007-03-03 16:59 ` Dr. Adrian Wrigley
2007-03-05 15:36 ` Colin Paul Gloster
2007-03-03 1:58 ` Ray Blaak
2007-03-03 8:14 ` Pascal Obry
2007-03-03 11:00 ` Dmitry A. Kazakov
2007-03-03 21:13 ` Ray Blaak
2007-03-05 19:01 ` PAR (Was: Embedded languages based on early Ada) Jacob Sparre Andersen
2007-03-06 2:01 ` Dr. Adrian Wrigley
2007-03-06 3:30 ` Randy Brukardt
2007-03-06 7:10 ` Ray Blaak
2007-03-06 18:05 ` Ray Blaak
2007-03-06 6:04 ` tmoran
2007-03-06 6:59 ` Ray Blaak
2007-03-06 7:07 ` Ray Blaak
2007-03-06 7:22 ` Martin Krischik
2007-03-06 13:18 ` Dr. Adrian Wrigley
2007-03-06 18:16 ` Ray Blaak
2007-03-06 23:49 ` Randy Brukardt
2007-03-07 8:59 ` Dmitry A. Kazakov
2007-03-07 18:26 ` Ray Blaak
2007-03-07 19:03 ` Dr. Adrian Wrigley
2007-03-07 19:55 ` Dmitry A. Kazakov
2007-03-07 20:17 ` Ray Blaak
2007-03-08 10:06 ` Dmitry A. Kazakov [this message]
2007-03-08 18:03 ` Ray Blaak
2007-03-07 20:18 ` Pascal Obry
2007-03-07 20:41 ` Dr. Adrian Wrigley
2007-03-08 5:45 ` Randy Brukardt
2007-03-08 10:06 ` Dmitry A. Kazakov
2007-03-10 1:58 ` Randy Brukardt
2007-03-10 9:11 ` Dmitry A. Kazakov
2007-03-08 18:08 ` Ray Blaak
2007-03-10 1:50 ` Randy Brukardt
2007-03-05 15:23 ` Embedded languages based on early Ada (from "Re: Preferred OS, processor family for running embedded Ada?") Colin Paul Gloster
2007-03-06 0:31 ` Dr. Adrian Wrigley
2007-03-01 16:09 ` Colin Paul Gloster
2007-03-01 13:23 ` Martin Thompson
2007-02-26 16:34 ` Preferred OS, processor family for running embedded Ada? Jean-Pierre Rosen
2007-02-26 21:18 ` Dr. Adrian Wrigley
2007-02-27 15:39 ` Jean-Pierre Rosen
2007-02-28 12:25 ` Jerome Hugues
2007-02-24 19:11 ` Mike Silva
2007-02-24 13:59 ` Jacob Sparre Andersen
2007-03-01 19:32 ` Jacob Sparre Andersen
2007-03-01 20:22 ` Mike Silva
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