Unveiling kernel concurrency in multiresolution filters on GPUs with an image processing DSL

Multiresolution filters, analyzing information at different scales, are crucial for many applications in digital image processing. The different space and time complexity at distinct scales in the unique pyramidal structure poses a challenge as well as an opportunity to implementations on modern accelerators such as GPUs with an increasing number of compute units. In this paper, we exploit the potential of concurrent kernel execution in multiresolution filters. As a major contribution, we present a model-based approach for performance analysis of as well single- as multi-stream implementations, combining both application- and architecture-specific knowledge. As a second contribution, the involved transformations and code generators using CUDA streams on Nvidia GPUs have been integrated into a compiler-based approach using an image processing DSL called Hipacc. We then apply our approach to evaluate and compare the achieved performance for four real-world applications on three GPUs. The results show that our method can achieve a geometric mean speedup of up to 2.5 over the original Hipacc implementation without our approach, up to 2.0 over the other state-of-the-art DSL Halide, and up to 1.3 over the recently released programming model CUDA Graph from Nvidia.