Dynamic Parallelization of Recursive Code Part I: Managing Control Flow Interactions with the Continuator
While most approaches to automatic parallelization focus on compilation approaches for parallelizing loop iterations, we advocate the need for new virtual machines that can parallelize the execution of recursive programs. In this paper, we show that recursive programs can be effectively parallelized when arguments to procedures are evaluated concurrently and branches of conditional statements are speculatively executed in parallel. We introduce the continuator concept, a runtime structure that tracks and manages the control dependences between such concurrently spawned tasks, ensuring adherence to the sequential semantics of the parallelized program. As a proof of concept, we discuss the details of a parallel interpreter for Scheme (implemented in Common Lisp) based on these ideas, and show the results from executing the Clinger benchmark suite for Scheme.
recursion continuator automatic parallelization virtual machines languages performance software speculation