Compile-Time Scheduling of Dynamic Constructs in Data ow Program Graphs

|Scheduling data ow graphs onto processors consists of assigning actors to processors, ordering their execution within the processors, and specifying their ring time. While all scheduling decisions can be made at runtime, the overhead is excessive for most real systems. To reduce this overhead, compile-time decisions can be made for assigning and/or ordering actors on processors. Compile-time decisions are based on known pro les available for each actor at compile time. The pro le of an actor such as the execution time and the communication patterns. However, a dynamic construct within a macro actor, such as a conditional and a data-dependent iteration, makes the pro le of the actor unpredictable at compile time. For those constructs, we propose to assume some pro le at compile-time and de ne a cost to be minimized when deciding on the pro le under the assumption that the runtime statistics are available at compile-time. Our decisions on the pro les of dynamic constructs are shown to be optimal under some bold assumptions, and expected to be near-optimal in most cases. The proposed scheduling technique has been implemented as one of the rapid prototyping facilities in Ptolemy. This paper presents the preliminary results on the performance with synthetic examples. Keywords| multiprocessor scheduling, dynamic constructs, pro le, macro actor, data ow program graphs.