[rescue] Perverse Question

Frank Van Damme frank.vandamme at student.kuleuven.ac.be
Sun Jun 15 11:46:27 CDT 2003

On Sunday 15 June 2003 13:21, Francisco Javier Mesa-Martinez wrote:
> > Actually, do you have benchmarks of that? In 3 years of using linux [1]
> > I've become sceptical about every sort of fud (no offense here).
> RTFM, you have been using linux on a X86 machine I suppose. GCC is mostly
> X86 optimized, RISC versions of GCC are notoriously bad when compared to
> vendor specific offerings. Then again, this is just another proof that you
> get what you pay for.

Indeed, mainly x86 (and a powerlite laptop, which is sun4m) (and if I'm lucky
maybe I lay my hands on an ultra5 soon).

Don't get me wrong, I don't want to just break down any claims from people who
know a 100 times more about computers as I do. I just have enough of
breakdown arguments like "it's free so it's cheap", many people just repeat
statements like this without thinking about whether they're true or where
they've originated - and in a good deal of cases they originate from the
marketing department of some proprietary vendor of operating systems or
office suites (think MS), or from a proprietary X server vendor (think
Accelerated X, I tried their Xserver and I don't think for my box it's really
much faster then what the dri project currently offers).

> On the average I have seen mips tools (Which are the ones I use most)
> producing code that is about 20% smaller in footprint (which is
> significant for a RISC machine, instruction bandwith is a major
> bottleneck). And the autoparallelization framework that the compiler has
> is just fantastic. Most SGIs I have dealt with are large SMP boxes, so
> this is fundamentals. Still some people still use gcc+mpi on these boxes
> too, but it is just because they do not want to spend the extra time to
> learn the tools (specially since the makefiles, compiler flags, etc, will
> be non portable), which I find really annoying. One should take advantage

Ah, I never realised compiler flags are incompatible across different
products. And I thought that would be a matter ox "export CC=/usr/bin/foo"...

So if I want a linux system that's completely compiled with eg a compiler from
Sun, I have to recreate every single makefile of the applications I compile?

> of the underlying architecture, so you should learn the damned specific
> tools :). BUt then again, most people assume that their code will
> eventually be migrated to a large linux cluster so they are already
> building their code from the ground up to be using message passign, even
> though it is going to be run on a large SMP-ish machine (Cc-NUMA is not
> really SMP but close enough).
> Under sun for example, we have run some interesting benchmarks. For
> example a graph coloring algorithm runs well over 40% faster with the
> sun tools than with gcc 2.8.ish (this was over a year ago or so, so the gcc
> was not current... but neither were the sun workshop compilers). This
> meant that our ultra 60 with a 400 (maybe 450) USII was actually keeping
> up with a 1GHz Athlon linux box running the same code!!! So I saw that as
> a fantastic achievement... of course this may be application specific
> though.

"Not current" seems an understatement. 2.8.1 is from 1998. 40 % seems like "a
tad faster" in any case.

> Thanks for the insult BTW....

Excuse me?

> > (Not that it would astonish me much, after all who knows more about Sun
> > cpu's then Sun?)
> Also the ratio of x86 gcc developers to other architectures is like 100:1,
> so of course the x86 will have better cisc intel support.

Well that plainly sucks.

> To give credit where credit is due, it is a fantastic achievement to have
> a free compiler set that supports so many architectures. So even if it
> ain't optimal, I salute them for offering tools for free to the masses :).

...and one that should crosscompile from any to any of the supported
architectures (though I did not manage to compile one yet).

> Also I asusme that the tradeoffs between designing a portable framework
> and trying to also optimize it must be a complete nightmare...

Frank Van Damme    http://www.openstandaarden.be
~~~~~~~~~~~~~~~    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Je pense, donc je suis breveti."

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