Precision selection for energy-efficient pixel shaders

In this work, we seek to realize energy savings in modern pixel shaders by reducing the precision of their arithmetic. We explore three schemes for controlling this reduction. The first is a static analysis technique, which analyzes shader programs to choose precision with guaranteed error bounds. This approach may be too conservative in practice since it cannot take advantage of run-time information, so we also examine two methods that take the actual data values into account - a programmer-directed approach and a closed-loop error-tracking approach, both of which can lead to higher savings. To use this last method, we developed several heuristics to control how the precisions will change over time. We simulate several series of frames from commercial applications to evaluate the performance of these different schemes. The average savings found by the static and dynamic approaches are 31%, 70%, and 62% in the pixel shader's arithmetic, respectively, which could result in as much as a 10--20% savings of the GPU's energy as a whole.