Word-length selection for power minimization via nonlinear optimization

This article describes the first method for minimizing the dynamic power consumption of a Digital Signal Processing (DSP) algorithm implemented on reconfigurable hardware via word-length optimization. Fast models for estimating the power consumption of the arithmetic components and the routing power of these algorithm implementations are used within a constrained nonlinear optimization formulation that solves a relaxed version of word-length optimization. Tight lower and upper bounds on the cost of the integer word-length problem can be obtained using the proposed solution, with typical upper bounds being 2.9% and 5.1% larger than the lower bounds for area and power consumption, respectively. Heuristics can then use the upper bound as a starting point from which to get even closer to the known lower bound. Results show that power consumption can be improved by up to 40% compared to that achieved when using simple word-length selection techniques, and further comparisons are made between the minimization of different cost functions that give insight into the advantages offered by multiple word-length optimization.