Beyond BFS: A Comparative Study of Rooted Spanning Tree Algorithms on GPUs
This addresses performance bottlenecks in parallel graph analytics for researchers and practitioners, but is incremental as it compares and adapts existing methods.
The study tackled the problem of rooted spanning tree construction on GPUs, which traditionally uses BFS with O(D) step complexity limiting parallelism, and found that a connectivity-based approach achieved up to 300x speedup over BFS on high-diameter graphs.
Rooted spanning trees (RSTs) are a core primitive in parallel graph analytics, underpinning algorithms such as biconnected components and planarity testing. On GPUs, RST construction has traditionally relied on breadth-first search (BFS) due to its simplicity and work efficiency. However, BFS incurs an O(D) step complexity, which severely limits parallelism on high-diameter and power-law graphs. We present a comparative study of alternative RST construction strategies on modern GPUs. We introduce a GPU adaptation of the Path Reversal RST (PR-RST) algorithm, optimizing its pointer-jumping and broadcast operations for modern GPU architecture. In addition, we evaluate an integrated approach that combines a state-of-the-art connectivity framework (GConn) with Eulerian tour-based rooting. Across more than 10 real-world graphs, our results show that the GConn-based approach achieves up to 300x speedup over optimized BFS on high-diameter graphs. These findings indicate that the O(log n) step complexity of connectivity-based methods can outweigh their structural overhead on modern hardware, motivating a rethinking of RST construction in GPU graph analytics.