As the DNN accelerator space consists of upwards of 14 free parameters, a thorough exploration is infeasible. The second problem is that evaluating the energy and accuracy of a single design point is costly as it involves both training a DNN and simulating hardware. This expense limits the number of points that can be explored, requiring good designs to be found with minimal point evaluations. Finally, the effects of the parameters on the objectives (energy and accuracy), as well as between the parameters themselves, are intertwined, creating an unintuitive and rough optimization landscape. Consider optimizing just two parameters: the bitwidth of fixed-point datatypes (a well known energy efficiency optimization [16]), and the L2 regularization parameter, used to prevent overfitting during training. While regularization is only intended to directly affect the accuracy objective, it also indirectly affects the energy objective: regularizing weights compresses their dynamic range, impacting the number of bits required to store the weights. Likewise, using a fixed-point datatype does not directly affect the regularization parameter, but it does reduce the resolution of a model's weights and the overall model accuracy, which both end up affecting the choice of regularization strength. Nearly all the design parameters in Table I impact both objectives, and the complex interactions between them are difficult to capture using traditional modeling techniques used to reason about hardware design spaces [11], [12].