DNN Acceleration: A High-Accuracy Implementation for Base-2 Softmax Layer

This paper introduces a high-accuracy implementation of the softmax layer in Deep Neural Networks (DNN) used in multi-category classification applications. Calculation of the exponentials or logarithms in the traditional base-e softmax is mathematically complex, which makes it hard to have a high-accuracy hardware implementation without being resource-consuming, so instead of using $e$ as the exponential base, this paper presents a hardware implementation of the base-2 softmax function that makes use of 2 as the exponential base. Thus, the complex operations in base-e softmax will be replaced by simple shift and addition operations, with simpler LUTs and higher accuracy. The implemented hardware model relies on single-precision floating-point arithmetic cores, it achieves classification accuracy equal to 100 ^% relative to a reference software model and has an area of 0.0802 mm ² with a power consumption of 8.93 mW when synthesized under TSMC 28nm CMOS technology at the frequency of 1 GHz.