From: everything-list@googlegroups.com
[mailto:everything-list@googlegroups.com] On Behalf Of meekerdb
Sent: Friday, September 20, 2013 5:25 PM
To: everything-list@googlegroups.com
Subject: Re: What gives philosophers a bad name?

 

On 9/20/2013 4:40 PM, Chris de Morsella wrote:

Current software is very energy efficient -- and on so many levels. I worked
developing code used in the Windows Smartphone and it was during that time
that I had to first think hard about the energy efficiency dimension in
computing -- as measured by useful work done per unit of energy. The
engineering management in that group was constantly harping on the need to
produce energy efficient code. 

 

Programmers are deeply engrained with a lot of bad habits -- and not only in
terms of producing energy efficient software. For example most developers
will instinctively grab large chunks of resources -- in order to ensure that
their processes are not starved of resources in some kind of peak scenario.
While this may be good for the application -- when measured by itself -- it
is bad for the overall footprint of the application on the device  (bloat)
and for the energy requirements that that software will impose on the
hardware. Another example of a common bad practice poorly written
synchronization code (or synchronized containers).

 

These bad practices (anti-patterns in the jargon) can not only have a huge
impact on performance in peak usage scenarios, but also act to increase the
energy requirements for that software to run.

 

I think that -- with a lot of programming effort of course (which is why it
will never happen) that the current code base, and not only in the mobile
small device space, where it is clearly important, but in datacenter scale
applications and service (exposed) applications as well -- that the energy
efficiency of software has a huge headroom for improvement. But in order for
this to happen there has to first be a profound cultural change amongst
software developers who are being driven by speed to market, and other
draconian economic and marketing imperatives and are producing code under
these types od deadlines and constraints.


There's a lot of bad design in consumer electronics, particularly in user
interfaces, because the pressure is to get more and newer features and apps.
Eventually (maybe already) this will slow down and designers will start to
pay more attention to refining the stuff already there.




 

If there is a theoretical minimum that derives from the second law of
thermodynamics it must be exceedingly far below what the current practical
minimums are for actual real world computing systems. And I do not see how a
minimum can be determined without reference to the physical medium in which
the computing system being measured is implemented. 


It is determined by the temperature of the environment in which entropy must
be dumped in order to execute irreversible operations (like erasing a bit).
But you're right that current practicle minimums are very far above the
Landauer limit and so it has not effect on current design practice.  The
current practice is limited by heat dissipation and battery capacity.

Okay.. and interesting as well, but wouldn't the dissipated low grade heat -
i.e. the entropy - depend not just on the ambient temperature (the sink),
but also on how much energy was required, in the first place, in order to
flip the bit in this simple single bit state machine {1,0} 

 

In fact how could a switch be implemented without it being implemented in
some medium that contains the switch?


>>The way to completely avoid Landauer's limit is to make all operations
reversible, never lose any information so that the whole calculation could
be reversed.  Then there's no entropy dumped to the environment and
Landauer's limit doesn't apply.

 

Intriguing thought, but hard to see how it could be done. Not sure I
understand what you mean by a reversible operation and how would a fully
reversible universe square with causality. unless of course causality is a
side effect of some other deeper process that we experience as the
irreversible vector of time. But at least within the universe we experience,
some processes are not reversible. In order to unwind a transaction a log is
required and a log requires the recording of information, which requires
space. When the log runs out of room then what happens? Without erasure
memory will run out.



Brent

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