> What cutoff are you using? Denormals are only generated for x around -11300 for 80-bit reals, but for floats they'll happen for x between about -85 and -105. IIRC, denormals are ~100 times slower than normals on x87, so could easily be performance killers.

I first started with -5 and and used -3 in the release, as the method is multi-resolution/sigma. Matlab, if I remember, used a sigma of 2.5 as its default cutoff for Gaussian window. And yes, due to their slow speed, I included denormal detection in order to error early. (infinity or nan are invalid outputs and happen only when the algorithm becomes unstable)

Robert Jacques wrote:
> I recently presented at the 49th Annual Meeting of the American Association of Physicists in Medicine an application of a deformable registration algorithm during the general poster discussion session. Of course, the reason I?m posting this here is that I wrote it in D. Or more precisely, I refactored it to D from C++, with some surprising 

What did the audience think of D?

> results. First, the main algorithm dropped to half the lines of code and I was able to completely remove some supporting routines. 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 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. For reference, I was using Microsoft Visual Studio 2003 and D1.x/Phobos on Intel/XP box.
> The code is now open source and available at:
> http://dailabs.duhs.duke.edu/imagequality.html
> And the associated abstract is published in Medical Physics:
> http://www.medphys.org/
> 
> P.S. Thank you Walter and the community for this great language.

> What did the audience think of D?

My plane got delayed, so I missed a portion of the poster session, but I did get talking in depth with one person about it. He had heard about D before, but hadn’t yet had a chance to try it and generally seemed positive, or at least as much as anyone would be towards an unknown (to them) language.