Re: GSL, VSIPL, and the ultimate numerical library

[Gerard Jungman <jungman at lanl dot gov>]

One last point of emphasis, at the risk of repeating
myself...

Because of the VSIPL goals, all of the discussion in
the VSIPL/GSL thread has concentrated on linear algebra
operations, and other large linear operations like FFTs.

Scanning the web for scientific software (a sad hobby of mine),
you will find many projects (and many of these failed)
which declare one of their main goals to be "to provide
efficient and portable vector/matrix objects...".
Perhaps they also got as far as providing some
kind of linear algebra, either native or through
interfaces to lapack.

We can judge the success of these attempts by the fact
that we are still arguing about vector/matrix implementations.

So I would just like to say that it is very important
to draw a distinction between these "linear" parts of
a generic library and the other functionality. I'm glad
that GSL did not become one of these zombie projects,
wandering in circles in the "vector/matrix" swamp.

On the other hand, it means that GSL could not afford
to do anything substantial about these issues; we
can't drain the swamp, and I doubt if it is even
possible, given the limitations imposed by the
implementation language.

And although VSIPL is a very reasonable spec
in C, I think implementations will suffer
from the standard abstraction penalties
in generic situations. I don't think this
is a controversial statement, but people are
free to disagree. Also, the concentration on
dense arrays is very limiting from the standpoint
of general scientific computing. Maybe this
will be addressed in later specs, but
it looks like the standard combinatorial
explosion of interfaces will be unavoidable.
These are the issues which I am most
concerned with.

I optimistically hope that the brave new
template world will come to the rescue. Right
now things are looking pretty good for that.
Maybe we will finally be able to move on
in life. I personally find linear algebra
to be extremely tedious.


-- 
G. Jungman