Well I fixed my bizzarre problem last night. It turns out that I was building the argv list for each forked process from the main input file list instead of from the sub list passed to each thread. Now PCA runs in a much more stable fashion. Next I'd like to add some sort of progress reporting and also decompress support. I had the idea of using inotify on the output files (since their names are known a priori) however inotify is Linux only and I haven't yet found a drop in replacement for Mac OS.
Adding my initial PCA work. This project depends on packJPG. I see intermittent issues and I'm not sure if it is caused by my code or by the packJPG code.