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Re: Global Warming - Forth as answer

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On 5/15/2013 8:42 AM, Anton Ertl wrote:
> albert@spenarnc.xs4all.nl (Albert van der Horst) writes:
>> In article<6d2b5778-d3e5-4a63-9300-e242bb3db8bf@googlegroups.com>,
>> <visualforth@rocketmail.com>  wrote:
>>> Forth is probably the greenest language - helping to reduce the heat!
>>>
>>> Today I got an Editor's Note from "Dr. Dobb's Update": Dealing With All
>>> Our Stuff
>>>
>>> There it says:
>>> "In 1961, Rolf Landauer theorized that there was a fundamental
>>> connection between the processing of information and the production of
>>> heat. Just last year, researchers at the University of Augsburg in
>>> Germany appear to have proven Landauer's theory. To reset a single bit,
>>> they showed, generates a minimum amount of heat; and the point is that
>>> this is a fundamental limit set not by the design of devices, but by the
>>> nature of information itself. Heat dissipation in computer chips is not
>>> merely a matter of mechanics, but is inherent in the processing of
>>> information."
>>> Source: http://www.drdobbs.com/article/print?articleId=240154150
>>
>> I've read an article in the Scientific American (a very long time ago)
>> that seems to imply that calculation is essentially a reversible process,
>> that can be done using infinitesimal energy. (And probably take a near
>> infinite time, but that was not clear to me.)
>
> Yes, if you do your calculations in reversible form, you can perform
> them with less energy consumption than Landauer's limit.  You still
> need some energy to drive this reversible computation in the direction
> you want (forward or reverse), and the more energy you spend, the
> faster it can go.

I don't remember the reversible issue in the article.  How does being 
irreversible cause a higher energy consumption?


> There was a course on reversible computing at TU Wien some years ago,
> and Gerald Wodni participated, and looked at how the concepts of that
> course could be integrated in Forth.  One interesting result was that
> "OVER +" is reversible (while OVER and + aren't).

I remember learning that in general computation does *not* create 
information, it actually destroys it, hence is irreversible.  When you 
perform a computation that clobbers a register, like ADD A,B where the 
result goes into B, B is lost and so the action is irreversible.  In 
Forth + may not be reversible, but I think OVER is, unless you are 
considering the state of the unused stack cell to be "information".

But like you say, today's computers are *far* from the theoretical limit 
of processing in order to be as fast as practical.

-- 

Rick

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Global Warming - Forth as answer visualforth@rocketmail.com - 2013-05-14 15:21 -0700
  Re: Global Warming - Forth as answer hughaguilar96@yahoo.com - 2013-05-14 18:40 -0700
    Re: Global Warming - Forth as answer Steve <nospam275@gmail.com> - 2013-05-14 21:00 -0700
      Re: Global Warming - Forth as answer visualforth@rocketmail.com - 2013-05-15 22:24 -0700
        Re: Global Warming - Forth as answer Steve <nospam275@gmail.com> - 2013-05-19 19:25 -0700
  Re: Global Warming - Forth as answer albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-15 10:05 +0000
    Re: Global Warming - Forth as answer anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-15 12:42 +0000
      Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-15 10:56 -0400
        Re: Global Warming - Forth as answer anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-15 15:08 +0000
          Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-15 11:19 -0400
            Re: Global Warming - Forth as answer anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-15 15:22 +0000
              Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-15 15:42 -0400
                Re: Global Warming - Forth as answer visualforth@rocketmail.com - 2013-05-15 13:45 -0700
                Re: Global Warming - Forth as answer Bernd Paysan <bernd.paysan@gmx.de> - 2013-05-15 23:38 +0200
                Re: Global Warming - Forth as answer anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-16 12:53 +0000
                Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-16 14:03 -0400
                Re: Global Warming - Forth as answer anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-17 12:41 +0000
        Re: Global Warming - Forth as answer albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-17 13:17 +0000
          Re: Global Warming - Forth as answer dirk.bruehl@usa.net - 2013-05-17 08:36 -0700
            Re: Global Warming - Forth as answer Steve <nospam275@gmail.com> - 2013-05-19 19:12 -0700
            Re: Global Warming - Forth as answer Steve <nospam275@gmail.com> - 2013-05-20 00:06 -0700
    Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-15 10:47 -0400
      Re: Global Warming - Forth as answer albert@spenarnc.xs4all.nl (Albert van der Horst) - 2013-05-17 13:23 +0000
        Re: Global Warming - Forth as answer rickman <gnuarm@gmail.com> - 2013-05-17 09:59 -0400
    Re: Global Warming - Forth as answer Steve <nospam275@gmail.com> - 2013-05-19 18:56 -0700
  Re: Global Warming - Forth as answer oh2aun@gmail.com - 2013-05-22 00:50 -0700

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