I need to manage CPU-heavy multitaskable jobs in an interactive application. Just as background, my specific application is an engineering design interface. As a user tweaks
I don't know if you're looking for a C++ library (which I think you are), but Doug Lea's Fork/Join framework for Java 7 is pretty nifty, and does exactly what you want. You'd probably be able to implement it in C++ or find a pre-implemented library.
More info here: http://artisans-serverintellect-com.si-eioswww6.com/default.asp?W1