Re: Alternatives to gcc (was Re: gcc 4.3: when will it become standard compiler?)

Pedro F. Giffuni wrote:
> 
> ----- Original Message ----
> ...
>> Well, initially my question was triggered by reading a performance duell
>> between FreeBSD 7/8, most recent U(n)buntu and OpenSolaris and someone
>> stated the 3% performance gain of U(n)buntu over FreeBSD was due to the
>> gcc4.3 compiler, which generates more efficient code. 3% mean
>> performance gain could mean (as I made this experience) a better
>> advantage in some special cases and having in mind numerical modelling
>> running on my lab's FreeBSd box (yet, but I think this is about to
>> change and move towards a RH Linux system due to the better support of
>> HPC and, a pitty, our admins build the cluster with RH and not FBSD).
>>
> 
> Even when it can be measured, performance can be very subjective, performance
> depends on many factors: the threading libraries, the options used to build the 
> packages, the filesystems and maybe even the position of the moon ;-). Most of 
> my numerical packages don't depend on the system compiler but rather depend on 
> what the ports system uses as the Fortran compiler so you will be glad to know 
> that we are indeed using gcc4.3 since last week.

I also do quite a bit of numerical work.  For me a 3% performance gain 
is not that much, and really becomes negligible compared to other issues.

I have written some software that, a year ago, ran twice as fast under 
Fedora Linux than it did under FreeBSD.  Now FreeBSD has completely 
caught up!  And I didn't change the software itself in any substantial 
manner.  My guess is that FreeBSD has improved its cache 
management/threading management considerably (because my programs (a) 
use large amounts of data and (b) are threaded).

So, for me, a big difference is 2 to 1.  A factor of 3% is definitely 
something dependent on the "position of the moon" as Pedro put it so 
eloquently.

Stephen