Mailinglist Archive: opensuse-programming (84 mails)

[Michael Stevens <Michael.Stevens@xxxxxxxx>]

On Monday 30 August 2004 18:33, John Lamb wrote:
> Stefan Hundhammer wrote:
> > OK, thanks, that's a very informative site.
> >
> > But according to the charts there, there is hardly any difference in
> > performance, right? Sometimes even C/C++ appears to be faster.
> >
> > Or am I reading those charts wrong?
An interesting paper. I would probably ignore the details of the charts 
however as the results date from 1996!

> No, though there may be other examples where F is actually faster,
> depending on the usual things, how it's compiled, what number-crunching
> is done etc.
Agreed

> There are still F libraries such as ATLAS that are 
> reputedly better than the C equivalent.
This is rather odd. ATLAS is most definitely written in C. It has both F77 and 
C interfaces. ATLAS is fast because of it's high quality algorithms and 
tuning ability.

That said if you are doing ordinary numeric computation I don't think you will 
notice any performance differences between F77/C/C++. If you are "fancy 
stuff" other factors will probably be more important. Compiler 
availability/strength, existing code etc etc

In terms of performance optimisation one of the biggest advantages Fortran has 
is the lack of pointers and therefore the lack off possible aliases.
C/C++ compilers have to employ comlex alias optimisation analysis. Here C++ is 
significantly better then C. Reference types (instead of pointers), the use 
of 'const', and inline member functions all help the complier.

Michael