Re: polyForth multitasker question

From	anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups	comp.lang.forth
Subject	Re: polyForth multitasker question
Date	2017-04-14 14:12 +0000
Organization	Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID	<2017Apr14.161245@mips.complang.tuwien.ac.at> (permalink)
References	(6 earlier) <mqGdnYQe2bgs-W3FnZ2dnUU7-IXNnZ2d@supernews.com> <ocpr1b$p4b$1@dont-email.me> <6_ydnXUzTNeS523FnZ2dnUU7-THNnZ2d@supernews.com> <2017Apr14.095322@mips.complang.tuwien.ac.at> <uPednfe7K92eVm3FnZ2dnUU7-SPNnZ2d@supernews.com>

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Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>> "Elizabeth D. Rather" <erather@forth.com> writes:
>>>In fact, it's far less complicated than that. Each task knows how
>>>long it's sleeping, and each time around the round-robin checks to
>>>see if it's wake-up time yet. A very few instructions each time.
>> 
>> If you have 100 tasks waiting in MS,
>
>IMO, this is the wrong way to think about it.
>
>You probably don't, or at least it's unlikely in a system where most
>tasks are stopped most of the time waiting for some kind of I/O event.

Then you have the same scaling problem.

Also, an example of a system with a huge number of tasks waiting on
timers is a game, where various agents in the game are implemented as
tasks.  Some of these agents (and that can easily be hundreds or
thousands) just do something at various intervals, say every 5s; a
natural way to implement this is:

begin do-something 5000 ms again

[Yes, an interface that is not relative to the current time would be
even better than MS.]

>If you really do need hundreds of tasks waiting in MS, then you can
>code a version of MS which is optimized for a large number of tasks.
>That version of MS is complicated because you'll have to maintain a
>priority queue.  A fast priority queue with O(n log n) insertion time
>requires a heap or a balanced binary tree, and the result is more than
>an order of magnitude more complex than that simple version of MS.

True, but it scales.

As an intermediate variant, you can have a separate MS task list, and
scan that completely whenever the next MS timer is reached, and wakes
these tasks.  Slightly more complex than the polling variant, but
already much more efficient.

>> It's simple, but it does not scale.
>
>That's true.  And it's a good thing.  That's the big idea of Forth
>design: do the simple thing, and only if it turns out to be inadequate
>do the complicated thing.

This approach has its charms, but the other approach of having a
scalable thing, giving the users the freedom to roam outside the
narrow confines of the implementor's imagination, also has its
advantages.

In the present case, we know how to do the scalable thing, it's not
very expensive, and it has been used in other environments, so I think
that the advantages of the scalable approach outweigh the
disadvantages (unless you are on tiny hardware where you cannot afford
hundreds of tasks anyway).

- anton
-- 
M. Anton Ertl  http://www.complang.tuwien.ac.at/anton/home.html
comp.lang.forth FAQs: http://www.complang.tuwien.ac.at/forth/faq/toc.html
     New standard: http://www.forth200x.org/forth200x.html
   EuroForth 2016: http://www.euroforth.org/ef16/

Thread

polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-08 20:53 +1000
  Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-08 12:29 -0500
    Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 09:50 +1000
      Re: polyForth multitasker question David Schultz <abuse@127.0.0.1> - 2017-04-09 19:25 -0500
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 10:52 +1000
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-10 08:58 -0500
            Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-15 10:39 +1000
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 11:12 +1000
          Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-10 18:22 -0700
            Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 12:17 +1000
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-11 03:10 -0500
      Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-09 14:37 -1000
        Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-09 18:05 -0700
          Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-09 15:50 -1000
          Re: polyForth multitasker question Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-10 07:47 +0200
        Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-10 12:20 +1000
        Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 09:11 +0100
          Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-10 04:20 -0500
            Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 10:53 +0100
              Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-10 11:24 +0100
              Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-11 12:05 +1000
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-11 14:27 +0100
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-11 07:08 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-11 18:06 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-11 18:58 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-12 13:57 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-12 18:02 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-12 19:47 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-12 21:22 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-13 02:57 -0700
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-12 23:17 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-13 00:13 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 09:43 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-13 19:34 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 19:57 -1000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 02:45 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 21:28 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 07:53 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 01:44 -0700
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-14 02:01 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 11:28 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 16:23 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 22:46 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 11:31 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 11:23 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 10:06 -1000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-14 08:13 -0500
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-14 14:12 +0000
                Re: polyForth multitasker question pahihu <pahihu@gmail.com> - 2017-04-14 09:30 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 08:46 +0000
                Re: polyForth multitasker question pahihu <pahihu@gmail.com> - 2017-04-15 13:07 -0700
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:27 -0700
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-15 18:18 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 13:53 +0000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-14 11:34 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 11:31 -0700
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-14 12:14 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:46 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:48 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 12:50 -0700
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 14:39 +0200
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-15 11:48 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-14 22:07 +0100
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 16:47 +0000
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-15 11:36 -1000
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-15 17:07 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-15 14:17 -1000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 18:27 -0700
                Re: polyForth multitasker question Ron Aaron <rambamist@gmail.com> - 2017-04-16 06:53 +0300
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 22:00 -0700
                Re: polyForth multitasker question Ron Aaron <rambamist@gmail.com> - 2017-04-16 08:59 +0300
                Re: polyForth multitasker question lehs <skydda.barnen@gmail.com> - 2017-04-15 22:19 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-15 17:26 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-16 09:10 -0500
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 09:13 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-16 16:28 +0000
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 09:27 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-16 14:45 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-16 17:50 -1000
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 12:13 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-17 13:27 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 03:49 -0500
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-18 13:47 +0100
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 14:30 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-16 20:58 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-18 11:47 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-17 19:19 -0700
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-18 04:34 -0500
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-19 02:00 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 18:10 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-19 01:41 -0700
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 21:38 +1000
                Re: polyForth multitasker question Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-19 10:56 +0200
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-19 07:22 -0500
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-17 20:10 -0700
                Re: polyForth multitasker question stephen@mpeforth.com (Stephen Pelc) - 2017-04-18 09:35 +0000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-18 08:01 -0700
                Re: polyForth multitasker question Julian Fondren <julian.fondren@gmail.com> - 2017-04-18 09:03 -0700
                Re: polyForth multitasker question Cecil Bayona <cbayona@cbayona.com> - 2017-04-18 11:07 -0500
                Re: polyForth multitasker question Cecil Bayona <cbayona@cbayona.com> - 2017-04-18 10:59 -0500
                Re: polyForth multitasker question "HAA" <someone@microsoft.com> - 2017-04-19 19:13 +1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:36 -0700
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-16 16:27 +0000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-16 04:32 -0500
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 10:15 -1000
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 13:07 +0200
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 15:13 +0000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 01:36 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 22:48 -1000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 16:36 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 14:55 -0700
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 15:27 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-14 23:45 +0100
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-16 21:13 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-17 16:57 +0100
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-17 20:08 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 20:29 -0400
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-14 15:34 -1000
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 19:43 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 23:03 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-14 23:50 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 03:55 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 01:38 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 11:50 -0400
                Re: polyForth multitasker question john <anon@example.com> - 2017-04-15 12:03 +0100
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-15 12:41 +0000
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 12:14 -0400
                Re: polyForth multitasker question Paul Rubin <no.email@nospam.invalid> - 2017-04-15 17:32 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 20:41 -0400
                Re: polyForth multitasker question anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2017-04-17 14:57 +0000
                Re: polyForth multitasker question hughaguilar96@gmail.com - 2017-04-14 20:45 -0700
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-14 23:56 -0400
                Re: polyForth multitasker question albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-15 14:32 +0200
                Re: polyForth multitasker question rickman <gnuarm@gmail.com> - 2017-04-15 12:05 -0400
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-15 04:10 -0500
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-13 03:19 -0700
                Re: polyForth multitasker question Alex <alex@rivadpm.com> - 2017-04-13 15:46 +0100
                Re: polyForth multitasker question foxaudioresearch@gmail.com - 2017-04-14 11:37 -0700
                Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-13 09:48 -1000
                Re: polyForth multitasker question Andrew Haley <andrew29@littlepinkcloud.invalid> - 2017-04-13 05:37 -0500
                Re: polyForth multitasker question minforth@arcor.de - 2017-04-11 22:12 -0700
                Multitasking with Forth processors Lars Brinkhoff <lars.spam@nocrew.org> - 2017-04-12 07:39 +0200
                Re: Multitasking with Forth processors Paul Rubin <no.email@nospam.invalid> - 2017-04-11 22:58 -0700
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-12 03:00 -0400
                Re: Multitasking with Forth processors albert@cherry.spenarnc.xs4all.nl (Albert van der Horst) - 2017-04-12 12:18 +0200
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-12 17:11 -0400
                Re: Multitasking with Forth processors foxaudioresearch@gmail.com - 2017-04-12 13:50 -0700
                Re: Multitasking with Forth processors "Elizabeth D. Rather" <erather@forth.com> - 2017-04-12 13:30 -1000
                Re: Multitasking with Forth processors Jan Coombs <jenfhaomndgfwutc@murmic.plus.com> - 2017-04-14 12:20 +0100
                Re: Multitasking with Forth processors rickman <gnuarm@gmail.com> - 2017-04-14 16:47 -0400
            Re: polyForth multitasker question "Elizabeth D. Rather" <erather@forth.com> - 2017-04-10 07:42 -1000

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