Experimental evaluation of energy behavior of iteration space tiling

Optimizing compilers have traditionally focused on enhancing the performance of a given piece of code.With the proliferation of embedded software, it is becoming important to identify the energy impact of these traditional performance-oriented optimizations and to develop new energy-aware schemes. Towards this goal, this paper explores the energy consumption behavior of one of the widely-used loop-level compiler optimizations, iteration space tiling, by varying a set of software and hardware parameters. Our results show that the choice of tile size and input size critically impacts the system energy consumption. Specifically, we find that the best tile size for the least energy consumed is different from that for the best performance. Also, tailoring tile size to the input size generates better energy results than working with a fixed tile size. Our results also reveal that tiling should be applied more or less aggressively based on whether the low power objective is to prolong the battery life or to limit the energy dissipated within a package.