Okay, here we go - trunk at svn/r2966 now seems to be working using GCD. Essentially, whatever computation is otherwise using CMTK's built-in thread pool will now use GCD on OS-X 10.6 and higher by default. Code parallelized using OpenMP will be gradually ported to GCD as much as possible (Note that Apple's current compiler cannot "dispatch" from class or function templates, so there are some functions that cannot be ported to GCD at this time). Guess this post should have gone to the developers forum instead ;)