[Pkg-scicomp-devel] Bug#578052: Bug#578052: [atlas] providing >20 separate optimized library packages is insane

Sylvestre Ledru sylvestre at debian.org
Fri Apr 16 12:45:09 UTC 2010


Hello Fabian,

Thanks, it is always interesting to have feedbacks!

Le vendredi 16 avril 2010 à 13:52 +0200, Fabian Greffrath a écrit :

> thanks alot for the effort you put in packaging the several optimized 
> versions of the atlas libraries, BUT I consider it completely 
> unnecessary to put them all into separate packages and leave it up to 
> the user to manually select the one optimized for his system.
Well, some people do not agree on this.
I think it is important to let the user select the appropriate
optimisation for his computer. 


> 1) Many users do not even know which features their processor 
> supports. What happens if I install the core2sse3-optimized library 
> (and it becomes the main alternative due to its higher priority in the 
> update-alternatives machanism) if my processor is a simple Pentium 3?
I believe that a user looking for performances on tool based on BLAS
implementation (R, Scilab, Code Saturne, etc) is aware that it is
related to the CPU they have.

> 2) It is possible to let the dynamic linker select special optimized 
> libraries based on information the kernel knows about my system (no 
> human intervention necessary). You can simply install libraries in 
> subdirectories of /usr/lib which are named after the feature that they 
> make use of. For example, you put the altivec-optimized library into 
> /usr/lib/altivec and the normal one into /usr/lib. The linker will 
> select the right one for you and give the optimized one a higher 
> priority. It works on all architectures and has already proven in 
> other packages that benefit from architecture-dependent optimizations.
I noticed your message on my blog. I didn't have time to investigate it:
I am currently more focused on build issues on some architectures but I
have it in mind.

However, if I understand correctly, this would mean that I would have to
ship all libraries into a single package or to add some Depends on the
base package, isn't it ?
An atlas package is almost 5M. For example, under x86, we have 5
optimized packages. This would increase by 5 time the install of Atlas.

> Please consider reverting the separation into the multitude of library 
> packages and make use of this neat feature instead.
The separation has been in Debian for a very long time (more than 10
years) and it is the first strong complain that I see about that (I know
it is not an argument for not doing it).

Sylvestre







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