Efficient and Exact Design Space Exploration for Heterogeneous and Multi-Bus Platforms

Design Space Exploration of data-flow Systems-on-Chip either focuses on classical shared bus or on complex network-on-chip (NoC) architectures. A lack of research work exists that targets segmented bus architectures. These offer performance improvements (latency, power consumption) with respect to a shared bus, while employing much simpler communication structures and algorithms than a NoC. Despite the lack in the research work, segmented buses are popular in multiprocessor systems and in FPGA interconnects. This paper fills this lack with two contributions. First, we propose a Satisfiability Modulo Theory (SMT) formulation. Secondly, we provide a technique to reduce the design-space explosion problem that is portable to other formulations (e.g., ILP, MILP) and to problems where the scheduling on units (e.g., bus, CPU) is multiplexed in time. We integrated these contributions in a state-of-the-art design tool that we employ for evaluation purposes with a set of streaming applications and a MPSoC platform. The resulting framework can study the performance of fixed interconnects as well as determine the optimal architecture among a set of candidates. Our reduction technique improves considerably the scalability of DSE. For our testbench, we reduce the SMT solver run-time from 20 up to 589 times.