Re: Assuming optimization? What is best of these code alternatives?

[Jeffrey Carter <spam.jrcarter.not@spam.not.acm.org>]

On 09/11/2014 06:14 AM, reinkor wrote:
> 
> What is the "best" alternative?  Alternative 2 
> is shortest (and probably easier to read), but
> could it give slower code that for Alternative 1 ?

The question, as always, is what are your timing requirements, and does the
clearest version meet them? If so, then there's no need to waste effort worrying
about "efficiency".

The optimization algorithm is

Write the clearest code

loop
   Measure the result

   exit when measurement meets the requirements

   Determine what's using the most time, and improve it,
      keeping it as clear as possible
end loop;

Other than GNAT with -O0, I'm not aware of any compiler that does no
optimization. 25 years ago an Ada-83 compiler produced smaller and faster code
than assembler optimized by a team of experts, and optimizers have surely
improved since then. So it's folly to think a human can do better than the
compiler without some evidence to the contrary.

-- 
Jeff Carter
"Clear? Why, a 4-yr-old child could understand this
report. Run out and find me a 4-yr-old child. I can't
make head or tail out of it."
Duck Soup
94