• Anuj Goyal (12/12) Aug 28 2004 in what cases would it be preferred to use fortran rather than c++/c? At...
• Ilya Minkov (38/46) Sep 01 2004 I heard they are able to optimize more agressively, but definately not
• Anuj Goyal (12/12) Sep 02 2004 thanks for your reply Ilya, I also believe that higher level constructs ...

Anuj Goyal <Anuj_member pathlink.com> writes:

in what cases would it be preferred to use fortran rather than c++/c? At the
moment, please ignore parallel Fortran compilers and the parallel runtimes.
Please concentrate on this question in terms of perofrmance, not necessarily
maintainability of the codebase, the "coolness" of the language, or the "object
oriented features" that one language lacks and that another language has.


Since fortran compilers have been around for so long, are they more optimized
than c? It seems that the language is mostly for use in the scientific community
and that many libraries are readily available. These libraries boil down to
assembly anyways right? what is the difference between using C and using Fortran
for libraries? Is it the nature of scientific programming that demands Fortran,
or is just that the scientific communities' programmers are more familiar with
Fortran? 

Ilya Minkov <minkov cs.tum.edu> writes:

Anuj Goyal schrieb:
 Since fortran compilers have been around for so long, are they more optimized
 than c? 

I heard they are able to optimize more agressively, but definately not 
for the reason of being around longer. The current architectures we use 
are younger than compilers - DMC is more than 20 years old (previously: 
Zortech, some other names). GCC is also of comparable age. The 
performance characteristic of CPUs doesn't look now too much like it was 
back then.

However, there are ways to give hints to C compilers so that they can 
employ somewhat more agressive optimizations.

 It seems that the language is mostly for use in the scientific community
 and that many libraries are readily available. These libraries boil down to
 assembly anyways right? what is the difference between using C and using
Fortran
 for libraries? Is it the nature of scientific programming that demands Fortran,
 or is just that the scientific communities' programmers are more familiar with
 Fortran?

With the number of libraries... I don't think it really matters since 
every mathematical foeld is probably covered in each of the languages 
many times over.

I'm not so sure there is so much "demand" for Fortran... You know, the 
whole performance difference due to agressive optimizations boils down 
to perhaps a few per cent - so uncomparably small compared to, say, 
performance gained by utilizing parallel processing. And the whole 
small-scale optimization is probably overhyped anyway.

I'm getting the impression that scientific community moves to C++ and 
high-level solutions, which are far from being optimal on the small 
scale, but are very easy from the usage point of view, and aid in 
getting an optimal design on the large scale.

What i say here about C probably applies to Fortran to a large extent, 
though i must say that i'm not familiar with it. In C, what you are 
dealing are separate functions, which are compiled separately and take 
fixed kind and number of arguments. They must be called, which means 
some sort of overhead. In C++, the working of typical math libraries is 
radically different, in part due to Templates. Imagine, for example a 
matrix library. If you were writing it in C, you would have sets of 
functions handle matrices of certain fixed sizes, and/or you could have 
a set of functions to handle matrices of arbitrary size - which is 
slower. But all funcrions to handle matrices of a fixed size would be 
very similar among sizes. With templates, you are not limited to that, 
you can have the library generate the code that fits your size. And 
inlining has shown to be useful where the work done by functions can 
often be optimized away. Of course the compiler doesn't always get it 
perfectly optimal, nor is there much that can be done to improve it, but 
generally it is acceptable.

-eye

Anuj Goyal <Anuj_member pathlink.com> writes:

thanks for your reply Ilya, I also believe that higher level constructs allow
people to be more productive.  However, I believe that people have not been
looking at the proper language.  ie Java and python are both decent languages
but they suffer from high setup time.  Have you heard of APL?  It is an
extremely fast, productive language that is used in the finance and insurance
worlds when dealing with large data sets that need to be manipulated.  Current
incarnations of APL are j and k.

www.jsoftware.com
www.kx.com

check out my page for examples, I am trying to add 1 example every couple of
days.

http://goanuj.freeshell.org/k