GRAEBO: FPGA General Routing Architecture Exploration via Bayesian Optimization

Modern FPGAs utilize complex routing architectures to optimize the area, critical path delay, and power consumption. General Routing Block (GRB) models the routing resources of modern FPGAs, enabling the design of better routing architectures than previous academic FPGAs based on the CB-SB model. However, the design space of the GRB model is too large to be explored manually. In this paper, we propose GRAEBO, a design space exploration (DSE) algorithm for FPGA routing architectures based on Bayesian optimization, which can optimize and accelerate the DSE by balancing exploration and exploitation. Moreover, we design pruning rules to further improve the DSE efficiency, which can serve as a multi-fidelity acceleration method. GRAEBO obtains better area, delay, and area-delay product than a 142-channel baseline CB-SB architecture, with improvements of 8%, 19%, and 26%, respectively. Compared to the GRB architecture found by the simulated annealing algorithm, GRAEBO achieves 9% smaller area, 5% shorter delay, and 13% better area-delay product on the VTR benchmarks.