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From: "G.B." <bauhaus@futureapps.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Everything You Know Is Wrong
Date: Tue, 29 Dec 2015 12:42:29 +0100
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On 28.12.15 21:40, Dmitry A. Kazakov wrote:
> On 2015-12-28 19:50, Nicholas Collin Paul de Gloucester wrote:
>
>> What is "this"?
>
> Energy saving set as the goal [of computing?]. The proper goal is better
> performance, when that require lower voltage be it so.
>
> I understood Georg meant "green computing" which is reverse - buying
> energy by selling performance.

I was thinking of mobile computing, among other forms of computing
that depend on the presence of, say, batteries.

The hardware people do a lot to reduce energy needs.  The software
people could add to that. One addition is almost existing already,
in JIT compilers that deploy alternative compiled routines. Of
course, the compilation step doesn't necessarily save energy
now. But optimization demonstrates that compiled routines could
differ by energy consumption.

Considering the above I was also thinking of resource sharing, the
resource, however, being energy. When the amount of energy available
to the computer depends on wall clock time, then a programmer
arranges for code whose execution can be postponed to when there is
sufficient energy.  For example, if two subprograms are independent
and their execution can be postponed until a third one needs their
results, then several orders of execution become possible and this
will not require tasking. Even interleaving is o.K.

op1
  |     op1     op2
op2       \   /
  |        op3
op3

Can pragma Pure be extended to allow this optimization?


> In the real world we get better performance at lower energy, just per
> laws of physics, as you pointed out.

You would be in control of Watts for performance.