Update: One of the things you didn't mention was what to do if it is impossible to schedule all jobs of one priority given the constraints. This is bound to happen and could cause infinite loops if you don't allow for it in your code.

Ahh, that explains those few days a month when I'm so overwhelmed I don't get anything done. I must be spending the entire day running my scheduling algorithm!

-- Randal L. Schwartz, Perl hacker