On Clustering Tasks in IC-Optimal Dags

Abstract

Strategies are developed for "fattening" the tasks of computation-dags so as to accommodate the heterogeneity of remote clients in Internet-based computing (IC). Earlier work has developed the underpinnings of IC-scheduling theory, an algorithmic framework for scheduling computations having intertask dependencies for IC. The theory's schedules strive to render tasks eligible for execution at the maximum possible rate, so as to: (a) utilize remoteclients' computational resources well, by enhancing the likelihood of having work to allocate to an available client; (b) lessen the likelihood of a computation's stalling for lack of tasks that are eligible for allocation. The current study begins to enhance IC-scheduling theory so that it can accommodate the varying computational resources of remote clients. The techniques developed here render a dag multi-granular by clustering its tasks. Several clustering strategies are developed: one works for any dag but produces only a limited variety of "fattened" tasks; others exploit the detailed structure of the dag being scheduled but allow a broad range of "fattened" tasks.