Mailinglist Archive: opensuse-programming (84 mails)

["William A. Mahaffey III" <wam@xxxxxxxxxx>]

Stefan Hundhammer wrote:

> On Saturday 28 August 2004 05:07, William A. Mahaffey III wrote:
>  
>
> > By the by, I do do some C & (frankly) like it. Almost all new stuff I
> > write is, in fact, in C (no good w/ C++ yet ....), unless there are
> > definite speed requirements, whence I go to FORTRAN.
> >    
>
> Just curious: Did you do any hard benchmarking to support that supposed 
> performance advantage of Fortran compared to C used in a similar way - i.e. 
> not doing any fancy stuff, just number crunching?
>
> Any pointers, anybody?
>
>
> CU
>  
Absolutely, have posted about that in the past. I have some code that I 
originally ran on Convex & Cray computers, written in the late '80's, in 
F77 (originally), which does simple operations (dot products, 
matrix-vector op'ns, etc). It was motivated by linpack, but did some 
other operations. I have since fancied it up (with a C main routine to 
allocate memory & call the various F77 & C leaf routines to do the 
actual work & clock things, etc.), & have run it on various SGI Octanes 
(2 X 195, 2 X 300, 2 X 400, 2 X 600 out at MSFC in HSV, Al. USA), SGI 
servers (250 MHz based Origins, 600 MHz Origins), as well as a DEC Alpha 
based server, and numerous PCs, from 400 MHz PII up to 2400 MHz P4's, as 
well as AMD Athlons from 1600 MHz to 2200 MHz. F77 is 10 - 25% faster 
than C under commercial compilers. Commercial C compilers are 10 - 30% 
faster than GCC. The speedups are usually higher the more operations you 
do per loop. Simple assigns or copies (memset, memcpy) as equally fast 
under C & F77. It is only an issue if you do large numerical simulations 
that really do take many hours or days to complete, then any speedup is 
noticable.