An optimized BFS algorithm: A path to load balancing in MIC

Graph traversal is a widely used algorithm in a variety of fields, including social networks, business analytics, and high-performance computing and so on. Graph traversal on single nodes has been well studied and optimized on modern CPU architectures. Now, heterogeneous computing is becoming more and more popular and CPU+MIC is a typical heterogeneous architectures. The Intel MIC (Many Integrated Core) has up to 57 cores and hasn't been fully evaluated for graph traversal. When use a MIC to traverse a graph, the MIC may suffer from loading imbalance for the reason that the degree of vertexes in a graph may differs very much, which can degrade system performance. So in this paper, an algorithmic design and optimization techniques are presented to load balancing in MIC. About the optimization design, the main idea is that treat the vertexes with big degree and the vertexes with small degree separately. For this reason, some adjustments will be made to existing algorithms and data structures. It has achieved almost big performance improvements over the BFS algorithm without loading balancing in MIC as shown in section VI. We believe that this novel algorithm can be successfully applied to a broader class of graph algorithms with many MIC cores.