Re: else ladders practice

On 30/11/2024 05:25, Tim Rentsch wrote:

Michael S <already5chosen@yahoo.com> writes:
 

On Wed, 27 Nov 2024 21:18:09 -0800
Tim Rentsch <tr.17687@z991.linuxsc.com> wrote:
>

Bart <bc@freeuk.com> writes:
>

On 26/11/2024 12:29, Tim Rentsch wrote:
>

Bart <bc@freeuk.com> writes:
>

On 25/11/2024 18:49, Tim Rentsch wrote:
>

Bart <bc@freeuk.com> writes:
>

It's funny how nobody seems to care about the speed of
compilers (which can vary by 100:1), but for the generated
programs, the 2:1 speedup you might get by optimising it is
vital!

>
I think most people would rather take this path (these times
are actual measured times of a recently written program):
>
       compile time:       1 second
       program run time:   ~7 hours
>
than this path (extrapolated using the ratios mentioned above):
>
       compile time:       0.01 second
       program run time:   ~14 hours

>
I'm trying to think of some computationally intensive app that
would run non-stop for several hours without interaction.

>
The conclusion is the same whether the program run time
is 7 hours, 7 minutes, or 7 seconds.

>
Funny you should mention 7 seconds.  If I'm working on single
source file called sql.c for example, that's how long it takes for
gcc to create an unoptimised executable:
>
   c:\cx>tm gcc sql.c            #250Kloc file
   TM:  7.38

>
Your example illustrates my point.  Even 250 thousand lines of
source takes only a few seconds to compile.  Only people nutty
enough to have single source files over 25,000 lines or so --
over 400 pages at 60 lines/page!  -- are so obsessed about
compilation speed.

>
My impression was that Bart is talking about machine-generated code.
For machine generated code 250Kloc is not too much.  I would think
that in field of compiled-code HDL simulation people are interested
in compilation of as big sources as the can afford.

 Sure.  But Bart is implicitly saying that such cases make up the
bulk of C compilations, whereas in fact the reverse is true.  People
don't care about Bart's complaint because the circumstances of his
examples almost never apply to them.  And he must know this, even
though he tries to pretend he doesn't.
 

And of course you picked the farthest-most
outlier as your example, grossly misrepresenting any sort of
average or typical case.

>
I remember having much shorter file (core of 3rd-party TCP protocol
implementation) where compilation with gcc took several seconds.
>
Looked at it now - only 22 Klocs.
Text size in .o - 34KB.
Compilation time on much newer computer than the one I remembered, with
good SATA SSD and 4 GHz Intel Haswell CPU - a little over 1 sec.  That
with gcc 4.7.3.  I would guess that if I try gcc13 it would be 1.5 to 2
times longer.
So, in terms of Klock/sec it seems to me that time reported by Bart
is not outrageous.  Indeed, gcc is very slow when compiling any source
several times above average size.
In this particular case I can not compare gcc to alternative, because
for a given target (Altera Nios2) there are no alternatives.

 I'm not disputing his ratios on compilation speeds.  I implicitly
agreed to them in my earlier remarks.  The point is that the
absolute times are so small that most people don't care.  For
some reason I can't fathom Bart does care, and apparently cannot
understand why most other people do not care.  My conclusion is
that Bart is either quite immature or a narcissist.  I have tried
to explain to him why other people think differently than he does,
but it seems he isn't really interested in having it explained.
Oh well, not my problem.

EVERYBODY cares about compilation speeds. Except in this newsgroup where people try to pretent that it's irrelevant.
But then at the same time, they strive to keep those compile-times small:
* By using tools that have themselves been optimised to reduce their runtimes, and where considerable resources have been expended to get the best possible code, which naturally also benefits the tool
* By using the fastest possible hardware
* By trying to do parallel builds across multiple cores
* By organising source code into artificially small modules so that recompilation of just one module is quicker. So, relying on independent compilation.
* By going to considerable trouble to define inter-dependencies between modules, so that a make system can AVOID recompiling modules. (Why on earth would it need to? Oh, because it would be slower!)
* By using development techniques involving thinking deeply about what to change, to avoid a costly rebuild.
Etc.
All instead of relying on raw compilation speed and a lot of those points become less relevant.
 > My conclusion is
 > that Bart is either quite immature or a narcissist.
I'd never bothered much about compile-speed in the past, except to ensure that an edit-run cycle was usually a fraction of second, except when I had to compile all modules of a project then it might have been a few seconds.
My tools were naturally fast, even though unoptimised, through being small and simple. It's only recently that I took advantage of that through developing whole-program compilers.
This normally needs language support (eg. a decent module scheme). Applying it to C is harder (if 50 modules of a project each use some huge, 0.5Mloc header, then it means processing it 50 times).
I think it is possilble without changing the language, but decided it wasn't worth the effort. I don't use it enough myself, and nobody else seems to care.