[Insight-users] Speed

[Gib Bogle]

I have encountered something that surprises me, and I'd like to hear any 
comments.  I'm not being critical, it's just interesting.  I was using 
MeanImageFilter, and was surprised at how slowly it ran on my image.  Since the 
filter function is very simple, I decided to code up my own version, to see if I 
could get it done faster.  I'm not really a competent C++ programmer, so I've 
just implemented an efficient algorithm in C.

I'm testing with a greyscale image 955x963x100, on a Core i7 W7 machine (4 
cores, 8 threads).  Setting each filter radius to 5, the MeanImageFilter 
processing takes 1184 sec, using all 8 threads (100% CPU usage).  My own 
averaging code takes 105 sec, using only a single thread (12.5% CPU usage).

Why the big difference?

Gib