Deformable registration in D

[Saaa]

> Second, the numerical
> stability of the algorithm increased, helping reduce a major fundamental 
> issue/flaw in algorithm (Ah, the joys of a continuous algorithm working on

What does numerical stability actually mean?
and... what is a continuous algorithm?

> discrete data). And lastly, it ran three to four times slower. The culprit 
> turned out to be the exponential function, which is the crux of the 
> algorithm and also what I assume was responsible for the increased 
> stability. I switched to using an exponential with finite support and 
> regained the speed while keeping the stability.

Exp with finite support, how does this go?

It all sounds interesting so I would like to understand it all :)