Re: "C Is The Greenest Programming Language" by: Chris Lott

From	David Brown <david.brown@hesbynett.no>
Newsgroups	comp.lang.c, comp.lang.c++
Subject	Re: "C Is The Greenest Programming Language" by: Chris Lott
Date	2021-11-23 20:02 +0100
Organization	A noiseless patient Spider
Message-ID	<snjds3$pdc$1@dont-email.me> (permalink)
References	(2 earlier) <snj2k7$vojf$1@news.xmission.com> <snj65u$tmi$1@dont-email.me> <snj6mo$q04$1@gioia.aioe.org> <snjbln$7rl$1@dont-email.me> <0KanJ.66939$VS2.55772@fx44.iad>

Cross-posted to 2 groups.

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On 23/11/2021 19:50, Richard Damon wrote:
> On 11/23/21 1:24 PM, David Brown wrote:
>> On 23/11/2021 18:00, DozingDog@thekennel.co wrote:
>>> On Tue, 23 Nov 2021 17:51:09 +0100
>>> David Brown <david.brown@hesbynett.no> wrote:
>>>> The power consumption for a processor is the sum of the static power
>>>> and
>>>> the dynamic power.  Dynamic power is proportional to the frequency and
>>>> the square of the voltage.  And energy usage is power times time.
>>>>
>>>> A processor that is designed to run at high frequency is likely to have
>>>> high-leakage transistors, and therefore high static power - when the
>>>> circuits are enabled.  But the faster you get the work done, the higher
>>>> a proportion of the time you can have in low-power modes with minimal
>>>> static power.  On the other hand, higher frequencies may need higher
>>>> voltages.
>>>>
>>>> As a rule of thumb, it is better to run your cpu at its highest
>>>> frequency - or at the highest it can do without raising the voltage -
>>>> and get the calculation done fast.  Then you can spend more time in
>>>> low-power sleep modes.  However, entering and exiting sleep modes takes
>>>> time and energy, so you don't want to do it too often - hence the
>>>> "big-little" processor combinations where you have a slower core that
>>>> can be switched on and off more efficiently.
>>>
>>> Why do many battery powered systems throttle the CPU to save the
>>> battery when
>>> its getting low then and why does undertaking CPU intensive tasks
>>> deplete the
>>> battery faster? You seem to be claiming that you can get something
>>> for nothing.
>>>
>>
>> If you have to do a certain calculation or set of calculations, it is
>> /usually/ more efficient to do them quickly and then let the processor
>> sleep deeper and longer.
>>
>> Modern cpus generally do /not/ throttle the cpu speed to save battery
>> power.  It only makes sense to slow down the processor if you have large
>> leakage currents that you can't turn off, in which case a slow clock can
>> mean lower energy overall.  With modern devices, clock gating lets you
>> turn off all or parts of the core much more effectively.
>>
> 
> Not sure if this holds for desktop/laptop caliber processors, but in the
> embedded world, many processors can have their core voltage dropped down
> when running at slower speeds, and since switching energy is
> proportional to V^2, slowing the processor and waiting less CAN save power.

That depends on the class of embedded system.  If you are talking about
large embedded processors - running embedded Linux, for instance - then
that's true.  But even there you usually aim for high speed and lots of
sleep if you can.  However, as I mentioned, entering and exiting sleep
modes takes some time - if you are doing it too frequently, that
overhead becomes dominant and it is better to run the whole thing at a
low clock rate.

Smaller embedded systems rarely change the voltage to the core.

> 
> I beleive this applies to processors with a 'Turbo' or 'Overclocked'
> mode in the desktop/laptop space, to run their fastest, they need to
> boost their power supplies at the cost of increase power consumption but
> fast speeds become available.
> 
> Then there is the fact that the 'simple' idle modes don't stop
> everything, so you are still burning the higher frequency power even
> when idle in parts of the circuit, and switching to more power savings
> mode can take a bit of time and actually cost power (as you power down
> then back up sections of the die) means that slower, higher usage, uses
> less power.
> 
> The problem is that this also limits you PEAK operational speed, so you
> need to balence those needs with your power concumption.

It is all a complicated balance, and a subject of continuous development
and improvement - no one choice fits everything.  (And the ideal power
management decisions need to know what a process is going to do before
it does it.)

Thread

"C Is The Greenest Programming Language" by: Chris Lott Lynn McGuire <lynnmcguire5@gmail.com> - 2021-11-22 16:19 -0600
  Re: "C Is The Greenest Programming Language" by: Chris Lott "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-22 14:58 -0800
    Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-11-23 07:10 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-23 13:12 -0800
        Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-11-24 10:54 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 12:01 +0100
            Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-24 13:58 +0100
      Re: "C Is The Greenest Programming Language" by: Chris Lott "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-23 13:23 -0800
  Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-22 18:25 -0500
    Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-11-23 07:21 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott Guillaume <message@bottle.org> - 2021-11-23 17:56 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-11-24 10:55 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Öö Tiib <ootiib@hot.ee> - 2021-11-24 05:54 -0800
      Re: "C Is The Greenest Programming Language" by: Chris Lott Lynn McGuire <lynnmcguire5@gmail.com> - 2021-11-23 19:00 -0600
        Re: "C Is The Greenest Programming Language" by: Chris Lott scott@slp53.sl.home (Scott Lurndal) - 2021-11-24 16:04 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 07:55 -0800
        Re: "C Is The Greenest Programming Language" by: Chris Lott legalize+jeeves@mail.xmission.com (Richard) - 2021-12-16 16:24 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-16 19:46 -0800
        Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-12-17 06:30 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-12-18 07:45 -0800
            Re: "C Is The Greenest Programming Language" by: Chris Lott legalize+jeeves@mail.xmission.com (Richard) - 2021-12-30 12:01 +0000
              Re: "C Is The Greenest Programming Language" by: Chris Lott Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-16 12:22 -0800
                Re: "C Is The Greenest Programming Language" by: Chris Lott legalize+jeeves@mail.xmission.com (Richard) - 2022-01-17 21:28 +0000
                Re: "C Is The Greenest Programming Language" by: Chris Lott Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-01-17 15:48 -0800
                Re: "C Is The Greenest Programming Language" by: Chris Lott legalize+jeeves@mail.xmission.com (Richard) - 2022-01-18 06:47 +0000
    Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 11:43 +0100
  Re: "C Is The Greenest Programming Language" by: Chris Lott om@iki.fi (Otto J. Makela) - 2021-11-23 14:17 +0200
    Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-23 16:53 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott om@iki.fi (Otto J. Makela) - 2021-11-24 11:40 +0200
        Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-24 15:49 +0000
    Re: "C Is The Greenest Programming Language" by: Chris Lott Lynn McGuire <lynnmcguire5@gmail.com> - 2021-11-23 19:01 -0600
      Re: "C Is The Greenest Programming Language" by: Chris Lott om@iki.fi (Otto J. Makela) - 2021-11-24 11:33 +0200
        Re: "C Is The Greenest Programming Language" by: Chris Lott Lynn McGuire <lynnmcguire5@gmail.com> - 2021-11-24 15:28 -0600
  Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 14:39 +0100
    Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-23 16:55 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-23 12:28 -0500
        Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 19:05 +0100
          Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-23 13:41 -0500
            Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-23 19:53 +0100
              Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-23 21:27 -0500
                Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-24 18:32 +0100
                Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-24 12:54 -0500
                Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-24 20:52 +0100
                Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-24 15:13 -0500
                Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-25 19:13 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-24 15:48 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-24 11:54 -0500
            Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-25 11:19 +0000
              Re: "C Is The Greenest Programming Language" by: Chris Lott Juha Nieminen <nospam@thanks.invalid> - 2021-11-25 11:46 +0000
                Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-25 15:57 +0000
              Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-25 07:04 -0500
                Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-25 15:59 +0000
  Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-23 16:03 +0100
    Re: "C Is The Greenest Programming Language" by: Chris Lott gazelle@shell.xmission.com (Kenny McCormack) - 2021-11-23 15:50 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-23 17:51 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott DozingDog@thekennel.co - 2021-11-23 17:00 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-23 12:36 -0500
          Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-23 19:24 +0100
            Re: "C Is The Greenest Programming Language" by: Chris Lott Richard Damon <Richard@Damon-Family.org> - 2021-11-23 13:50 -0500
              Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-23 20:02 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-23 20:59 +0100
          Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-23 20:50 +0000
            Re: "C Is The Greenest Programming Language" by: Chris Lott Ian Collins <ian-news@hotmail.com> - 2021-11-24 11:18 +1300
              Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-23 22:58 +0000
            Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-23 23:46 +0100
              Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-24 13:59 +0000
                Re: "C Is The Greenest Programming Language" by: Chris Lott antispam@math.uni.wroc.pl - 2021-12-11 13:25 +0000
                Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-12-11 14:54 +0000
            Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-25 12:12 +0100
          Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-23 23:35 +0100
            Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-24 15:30 +0100
              Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-24 14:43 +0000
      Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-23 20:29 +0100
    Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-23 16:14 +0000
    Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 11:56 +0100
      Re: "C Is The Greenest Programming Language" by: Chris Lott Öö Tiib <ootiib@hot.ee> - 2021-11-24 06:03 -0800
      Re: "C Is The Greenest Programming Language" by: Chris Lott Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2021-11-24 10:14 -0800
        Re: "C Is The Greenest Programming Language" by: Chris Lott David Brown <david.brown@hesbynett.no> - 2021-11-24 19:55 +0100
          Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 21:13 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 21:11 +0100
      Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 21:17 +0100
        Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-11-24 20:42 +0000
          Re: "C Is The Greenest Programming Language" by: Chris Lott Philipp Klaus Krause <pkk@spth.de> - 2021-11-24 23:25 +0100
          Re: "C Is The Greenest Programming Language" by: Chris Lott antispam@math.uni.wroc.pl - 2021-12-11 14:07 +0000
            Re: "C Is The Greenest Programming Language" by: Chris Lott Bart <bc@freeuk.com> - 2021-12-11 18:46 +0000
              [OT] Lisp.  Was: "C Is The Greenest Programming Language" by: Chris Lott Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-12-11 20:11 +0000
  Re: "C Is The Greenest Programming Language" by: Chris Lott "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-11-24 14:12 -0800
    Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-11-25 12:00 +0100
  Re: "C Is The Greenest Programming Language" by: Chris Lott Paavo Helde <eesnimi@osa.pri.ee> - 2021-12-05 22:51 +0200
    Re: "C Is The Greenest Programming Language" by: Chris Lott "Chris M. Thomasson" <chris.m.thomasson.1@gmail.com> - 2021-12-05 19:20 -0800
    Re: "C Is The Greenest Programming Language" by: Chris Lott Manfred <noname@add.invalid> - 2021-12-06 12:28 +0100
      Re: "C Is The Greenest Programming Language" by: Chris Lott Paavo Helde <eesnimi@osa.pri.ee> - 2021-12-06 13:40 +0200
    Re: "C Is The Greenest Programming Language" by: Chris Lott Bonita Montero <Bonita.Montero@gmail.com> - 2021-12-06 16:21 +0100

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