Determinator is an experimental multiprocessor, distributed OS that creates an environment in which anything an application computes is exactly repeatable. It consists of a microkernel and a set of user-space runtime libraries and applications. The microkernel provides a minimal API and execution environment, supporting a hierarchy of “shared-nothing” address spaces that can execute in parallel, but enforcing the guarantee that these spaces evolve and interact deterministically. Atop this minimal environment, Determinator's user-space runtime library uses distributed systems techniques to emulate familiar shared-state abstractions such as Unix processes, global file systems, and shared memory multithreading.
A subset of Determinator comprises PIOS (“Parallel Instructional Operating System”), a teaching OS derived from and providing a course framework similar to JOS, where students fill in missing pieces of a reference skeleton. Determinator/PIOS represents a complete redesign and rewrite of the core components of JOS. To our knowledge PIOS is the first instructional OS to include and emphasize increasingly important parallel/multicore and distributed OS programming practices in an undergraduate-level OS course. It was used to teach CS422: Operating Systems at Yale in Spring 2010, and is freely available for use and adaptation by others.