Accelerating Sparse Linear Algebra and Deep Neural Networks on Reconfigurable Platforms
Yaman Umuroglu · BIBSYS Brage (BIBSYS (Norway)) · 2018
Regardless of whether the chosen figure of merit is execution time, throughput, battery life for an embedded system or total cost of ownership for a datacenter, today’s computers are fundamentally limited by their energy efficiency. Using specialized hardware-software solutions for particular applications or domains is a well-known approach to increase energy efficiency of computing systems. Reconfigurable logic in the form of Field-Programmable Gate Arrays (FPGAs) is a particularly promising substrate for hardware specialization, owing to its runtime reconfigurability, vastly parallel compute fabric and widespread availability. However, mapping computation to reconfigurable logic in a way which provides performance and efficiency benefits is a significant challenge due to the vast design space. In this thesis, we study how two particular domains can benefit from specialized architectures on reconfigurable logic. We focus on sparse linear algebra and deep neural network inference, whose execution is known to be particularly problematic on today’s general-purpose computers. For sparse linear algebra, lack of spatial and temporal locality in memory accesses pose a fundamental problem. We address this problem by taking advantage of the flexibility of reconfigurable logic to construct specialized memory systems.We propose a hardware-software caching scheme which uses lightweight preprocessing to extract key access pattern information fromsparse matrices to offer greatly increased random access efficiency with minimal on-chip memory usage. Furthermore, we demonstrate the broader applicability of the specialization for sparse linear algebra to graph analytics with an accelerator for breadth-first search that uses off-chip memory bandwidth more efficiently compared to prior work. For deep neural network inference, the sheer energy and hardware resource cost of floating point computation is a fundamental limitation on energy efficiency. Exploiting recent advances in training highly quantized neural networks (QNNs), we demonstrate how FPGAs can be leveraged for accurate, energy-efficient and high-performance neural network inference.We propose the FINN framework to generate customized architectures with compute resources tailored to user-specified performance requirements while exploiting multiple levels of parallelism for high energy efficiency. We also describe mathematical simplifications for making QNN inference more resourceefficient, and show how binary matrix operators can be used as bit-serial building blocks for higher-precision computation.