Graph Coloring on the GPU and Some Techniques to Improve Load Imbalance

Graphics processing units (GPUs) have been increasingly used to accelerate irregular applications such as graph and sparse-matrix computation. Graph coloring is a key building block for many graph applications. The first step of many graph applications is graph coloring/partitioning to obtain sets of independent vertices for subsequent parallel computations. However, parallelization and optimization of coloring for GPUs have been a challenge for programmers. This paper studies approaches to implementing graph coloring on a GPU and characterizes their program behaviors with different graph structures. We also investigate load imbalance, which can be the main cause for performance bottlenecks. We evaluate the effectiveness of different optimization techniques, including the use of work stealing and the design of a hybrid algorithm. We are able to improve graph coloring performance by approximately 25% compared to a baseline GPU implementation on an AMD Radeon HD 7950 GPU. We also analyze some important factors affecting performance.