Re: Numerical Computation and Ada95

[Gary Scott <Gary.L.Scott@lmtas.lmco.com>]

Hi, 

tmoran@acm.org wrote:
> 
> >From what you said I undestand that nobody has ever compared Ada's timing
> >performance with Fortran77/90/95, C and C++ in programs that require lots
> >of arithmetic and logical operations (perhaps FFT).  I think I will try to
> >do it when I learn Ada95 better
>   There was a substantial comparison someplace (perhaps Ada Letters?)
> some time ago, but I don't remember just when.  Try looking in
> www.adapower.com, www.adahome.com, or www.adaic.org  A simple minded
> transliteration from one language to another can have pitfalls,
> accessing arrays in row-major vs column-major order being an example.
> When I went to translate an algorithm from "Numerical Recipes in
> Fortran" it became obvious during the translation to Ada that the
> Fortran version was doing some extra, wasted, iterations.  Do you want
> to compare the Fortran version against an exact translation that
> includes those wasted cycles, or against an Ada version that preserves
> the algorithm, but not the poor coding?  It's not always obvious
> what's the appropriate comparison.

In that case, I'd probably clean up the Fortran code first, then
translate it and do the comparison.  Poorly written code is just that. 
However, the optimization possibilities of the language and the quality
of the optimizer itself has a lot more to do with the differences in
typical code (and cache accesses and memory alignment, etc.).