Exploring hidden coherency of Ray-Tracing for heterogeneous systems using online feedback methodology

Although naturally adopting an embarrassingly parallel paradigm, Ray-Tracing is also categorized as an irregular program that is troublesome to run on graphics processing units (GPUs). Conventional designs suffer from a performance penalty due to the irregularity of the control flow and memory access caused by incoherent rays. This work aims to explore the hidden coherency of rays by designing a feedback-guided mechanism that serves the following concept: extraction of the hidden regular portions out of the irregular execution flow. The method records the correlation of ray attributes and the traversed path and groups the newly generated rays to reduce potential irregularities for the ongoing execution. This mechanism captures the information from the entire ray space and can extract the hidden coherency from both primary and derived rays. The result leads to performance gains and an increase in resource utilization. The performance becomes 2 to 2.5 times higher than the original GPU and CPU versions.