ParRA: A Shared Memory Parallel FPGA Router Using Hybrid Partitioning Approach

Abstract

In this paper, we propose a shared-memory parallel field-programmable gate array (FPGA) router called ParRA. Basically, ParRA is composed of hybrid partitioning and parallel routing. During the hybrid partitioning, first an FPGA is split into multiple subregions and nets are geographically partitioned into local subsets. As the intersubregion nets usually overlap each other, these nets cannot be routed in parallel. Second, the intersubregion nets are further partitioned into conflict-free subsets. Since each conflict-free subset consists of intersubregion nets do not overlap each other, the nets in the same conflict-free subset can be routed in parallel. In this way, we significantly increase the number of nets that have potential to be routed in parallel. During the parallel routing process, two novel parallel routing strategies are applied to route the nets in conflict-free and local subsets, respectively. With conflict-free subsets, sinks in the same conflict-free subset are routed in parallel while conflict-free subsets are routed one by one. On the contrast, local subsets are routed in parallel while the nets in the same local subset are routed sequentially. With the two different parallel routing strategies, we reduce the interference between threads and balance the workload of threads, which contributes to gain more parallelism. The proposed parallel router provides deterministic routing results. The experimental results show that ParRA achieves an average speedup of $24.3 {\times }$ with 16 threads compared to VPR 7.0, has no negative impact on the quality of results.