Program Optimization of Stencil Based Application on the GPU-Accelerated System

Graphic Processing Unit (GPU), with many light-weight data-parallel cores, can provide substantial parallel computational power to accelerate general purpose applications. But the powerful computing capacity could not be fully utilized for memory-intensive applications, which are limited by off-chip memory bandwidth and latency. Stencil computation has abundant parallelism and low computational intensity which make it a useful architectural evaluation benchmark. In this paper, we propose some memory optimizations for a stencil based application mgrid from SPEC 2K benchmarks. Through exploiting data locality in 3-level memory hierarchies and tuning the thread granularity, we reduce the pressure on the off-chip memory bandwidth. To hide the long off-chip memory access latency, we further prefetch data during computation through double-buffer. In order to fully exploit the CPU-GPU heterogeneous system, we redistribute the computation between these two computing resource. Through all these optimizations, we gain 24.2x speedup compared to the simple mapping version, and get as high as 34.3x speedup when compared with a CPU implementation.