Data and Computation Reuse in CNNs Using Memristor TCAMs

Abstract

Exploiting computational and data reuse in CNNs is crucial for the successful design of resource-constrained platforms. In image recognition applications, high levels of input locality and redundancy present in CNNs have become the golden goose for skipping costly arithmetic operations. One promising technique for this consists in storing function responses of some input patterns into offline lookup tables and replacing online computation with search operations, which are highly efficient when implemented by emerging non-volatile memory technologies. In this work, we rethink both algorithm and architecture for exploiting locality and reuse opportunities by replacing entire convolutions with searches on Content-addressable Memories. By previously calculating convolution results and building compact lookup tables with our novel clustering algorithm, one can evaluate activations at constant time complexity, also requiring a single read operation of the current input tensor. Then, we devise a reconfigurable array of processing elements based on memristive Ternary Content-addressable Memories to efficiently implement the algorithmic solution and meet the flexibility requirements of several CNN architectures. Results show that our design reduces the number of multiplications and memory accesses proportionally to the number of convolutional layer channels. The average performance is 1,172 and 82 FPS for AlexNet and VGG-16 models, thus outperforming state-of-the-art works by 13×.