On-line Multiprocessor Tasks Scheduling with Rejection

This paper deals with multiprocessor task scheduling with ready times, due dates and prespecified processor allocation. In the studied problem tasks are not initially all available in the scheduler and can be executed only by given ready times, respecting their due dates. Moreover, a task can be examined in order to be processed only when it enters the scheduler. The concept of rejection is introduced as a further ingredient, i.e., when a task can be scheduled only by a time greater than its due date then it must be discarded. The goal is to try to schedule as much tasks as possible. We devised an algorithm based on a function which, in the case a task should be rejected, moves tasks already tentatively scheduled afterwards, to try to make room for a successive possible inclusion in the schedule of the former task. Experimental results are provided.