On the Computational Complexity of a Generalized Scheduling Problem

The parallel scheduling of a partially ordered set of tasks has received great attention. The partially ordered tasks can be viewed as components of a straight-line program. In this note, we discuss some aspects of the nonpreemptive parallel scheduling of a program with more general control structures. We examine the existence of optimal k-processor schedules, and in line with recent interest in the complexity of computer computations and algorithms, we study the complexity of constructing optimal k-processor schedules. In particular we show that, for every k > 1, any algorithm that would yield an optimal k-processor schedule of a loop-free program, when such a schedule exists, will be of exponential-time complexity.