Scheduling under Resource Constraints using Dis-Equations

Scheduling is an important step in high-level synthesis (HLS). In our tool, we perform scheduling in two steps: coarse-grain scheduling, in which we take into account the whole control structure of the program including imperfect loop nests, and fine-grain scheduling, where we refine each logical step using a detailed description of the available resources. This paper focuses on the second step. Tasks are modeled as reservation tables (or templates) and we express resource constraints using dis-equations (i.e., negations of equations). We give an exact algorithm based on a branch-and-bound method, coupled with variants of Dijkstra´s algorithm, which we compare with a greedy heuristic. Both algorithms are tested on pieces of scientific applications to demonstrate their suitability for HLS tools