Rate-energy-accuracy optimization of convolutional architectures for face recognition

• We optimize the energy-rate-accuracy characteristics of a convolutional architecture for face recognition.
• We profile a convolutional network implementation on low-power hardware, i.e., a Raspberry Pi.
• We obtain a speedup of 17 without significantly affecting task accuracy.
• We propose a coding architecture tailored to features extracted by such model, obtaining very compact yet effective features.

Face recognition systems based on Convolutional Neural Networks (CNNs) or convolutional architectures currently represent the state of the art, achieving an accuracy comparable to that of humans. Nonetheless, there are two issues that might hinder their adoption on distributed battery-operated devices (e.g., visual sensor nodes, smartphones, and wearable devices). First, convolutional architectures are usually computationally demanding, especially when the depth of the network is increased to maximize accuracy. Second, transmitting the output features produced by a CNN might require a bitrate higher than the one needed for coding the input image. Therefore, in this paper we address the problem of optimizing the energy-rate-accuracy characteristics of a convolutional architecture for face recognition. We carefully profile a CNN implementation on a Raspberry Pi device and optimize the structure of the neural network, achieving a 17-fold speedup without significantly affecting recognition accuracy. Moreover, we propose a coding architecture custom-tailored to features extracted by such model.