Re: else ladders practice

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.

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.