[fpc-devel] Simplicity vs. Complexity

[Joao Schuler]

Dear Moreton,
I think that you might have touched the most important question of all.
I'll express my own professional opinion in regards to this (not wishing to
convince others - just expressing my own).

I've been thinking on this question for more than 20 years. If you own a
company and your developers develop code towards speed to a point that is
too hard to find new employees able to understand the code, you will be in
a dangerous/costly zone. Firstly, because you have to spend too much
finding brave/qualified developers. Secondly, the harder the code gets to
be understood, the harder will be future improvements and eventual bug
fixes. Imagine that you own a company and your developers can't fix a bug
introduced 10 years before...Worst, some companies that I worked for in the
past had contractual requirements for fixing some problems in just 2
hours... It's a horrible place to be. In my mind, when you start modifying
a code with only speed in mind, your code optimization reaches a local
maxima (https://en.wikipedia.org/wiki/Maxima_and_minima). No one can safely
optimize a code that doesn't fully understand. So, there is a paradox: by
optimizing, you may prevent future optimizations because the human energy
needed to understand the code might defuse future optimization attempts.
The harder the code gets, more numerous voices will say "we need to trash
and recode this".

There are ways to deal with extreme optimizations. One way is extreme
documentation.  As an example, there is a 12 pages documentation about a
one page code here: https://cnugteren.github.io/tutorial/pages/page1.html .

As this email will be, our code will be read by others. I don't care if my
mind understands it. Will others understand it?

Food for thought I hope.

Cheers!

On Tue, Mar 26, 2019 at 5:20 PM J. Gareth Moreton <gareth at moreton-family.com>
wrote:

> This is a question regarding the compiler
> in general, and I sense there is no single
> correct answer.
>
> As you may already know, FPC compiles
> source code into intermediate nodes. Most
> of these are quite straightforward, like
> addition and a procedure call, but then
> you get quite a few that map onto internal
> functions and intrinsics like "abs" and
> are otherwise handled directly by the
> compiler rather than calling a function in
> the System unit, say.
>
> In your experience, and through theory,
> where should the line be drawn with
> internal routines and explicitly writing a
> function? I can see advantages in both
> approaches, like it's easier to assemble a
> node into a specific instruction set, but
> it can cause a lot of bloat in the
> compiler, while having an explicit
> function reduces this compiler complexity
> and allows for internal code improvements
> and better acceptance of features like
> pure functions, but may increase
> compilation time and make optimisation
> more difficult, depending on how it is
> implemented.
>
> Just looking for discussion.
>
> Gareth aka. Kit
>
>
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