Alternatives to gcc (was Re: gcc 4.3: when will it
become standard compiler?)
Stephen Montgomery-Smith
stephen at math.missouri.edu
Sun Jan 11 10:06:09 PST 2009
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
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