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Re: polyForth multitasker question

From anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups comp.lang.forth
Subject Re: polyForth multitasker question
Date 2017-04-15 16:47 +0000
Organization Institut fuer Computersprachen, Technische Universitaet Wien
Message-ID <2017Apr15.184706@mips.complang.tuwien.ac.at> (permalink)
References (6 earlier) <6_ydnXUzTNeS523FnZ2dnUU7-THNnZ2d@supernews.com> <2017Apr14.095322@mips.complang.tuwien.ac.at> <uPednfe7K92eVm3FnZ2dnUU7-SPNnZ2d@supernews.com> <2017Apr14.161245@mips.complang.tuwien.ac.at> <Vv6dnYA3-LOtZ23FnZ2dnUU7-K_NnZ2d@supernews.com>

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Andrew Haley <andrew29@littlepinkcloud.invalid> writes:
>Anton Ertl <anton@mips.complang.tuwien.ac.at> wrote:
>> 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.
>
>Not entirely, no: there a substantial difference between stopped tasks
>and tasks that are woken every time around the round robin.

Makes me wonder why waiting for I/O is optimized in this way, but
waiting for the timer is not.

And of course, because all the stopped tasks are still visited when
there is a PAUSE, you incur the cache accesses (and cache evictions)
that I mentioned earlier.  It will not incur the cost of executing the
checking code (and avoid the I-cache cost associated with that), but
whether these savings are substantial is in the eye of the beholder.

>> 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.
>
>I agree.  It's a contrast between the "add the hooks and facilities
>now just in case" approach and the Forth approach that's described in
>Thinking Forth.  One can lead to very neat, compact, and simple
>systems, and one leads to more complex but perhaps more scalable and
>general-purpose ones.

It's a false dichotomy.  You don't get a scalable and general-purpose
system by adding "hooks and facilities just in case", you get a
bloated system.  You have to find a good balance, and the art is in
finding that balance.

And the dogmas "minimize implementation complexity" and "minimize
functionality" that are advocated by many here are adverse to finding a
good balance.  People stop exploring the options, because the dogmas
prevent them.  And as a result, we get functionally deficient systems,
or alternatively, accumulations of special-purpose hacks, each of
which may satisfy the "minimize functionality to minimize
implementation complexity" meme, but in combination are not neat,
compact, and simple, but at least satisfy the "minimize functionality"
dogma by being inflexible.

>The Forth scheduler, despite its supposed lack of sophistication, was
>able to run many terminals on a lowly IBM PC even when it was
>supposedly "impossible" to run conventional multi-user systems on that
>hardware.

Which multi-user system was that?  VM/CMS?  Or VMS?  Yes, you cannot
run these systems on an IBM 5150.

>Those multi-user systems used things like priority queues
>and sophisticated schedulers, supposedly for efficiency, but such
>systems didn't scale *downwards*.  Scalability goes in both
>directions!

Doing the MS optimizations discussed here would certainly be possible
on an IBM PC, but with 256KB max (i.e., a few hundred tasks at the
most) at least the O(n log(n)) implementation of looking up the next
task to be woken would probably be overkill.  You probably don't want
to do concurrency-oriented programming with that little RAM, so you
don't need the scalability.

But the IBM 5150 has long been replaced by machines with much more
RAM.  Being nostalgic about the great deeds of the 70s and 80s, and
the principles that were helpful (or at least sufficient) at the time
does not help in finding a good balance for many of today's
programming problems.

>  That "tiny hardware" probably makes up many (most?) of
>the computers in the world.

That may be the case, but how many programmers program them?  And how
many program them in Forth?  If a few dozen programmers at Bosch
program the engine control microcontrolers for millions of cars, you
may count that as millions of computers, but I still count it as a few
dozen programmers.  But even these few dozen probably don't program in
Forth, because Forth is not widespread enough.  And the unbalanced
minimization dogmas have something to do with that.  Or in other
words: If you give up the desktop, you also give up a large part of
the tiny computers.

>Also, I'm thinking about the joy of knowing that the system you just
>shipped is the simplest cleanest, and (yes!) most perfect you know how
>to make.  That's got to be worth something.

Sure, it may get you a prize at a demo coding contest.  In the rest of
the world, sorry, this is not worth much.

- 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/

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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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