Lita Yang

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BSEE, California Institute of Technology, 2012

MSEE, Stanford University, 2015

Admitted to Ph.D. Candidacy: 2013-2014

Email: yanglita AT stanford DOT edu
Research: Energy-efficient Memory and Communication Design for Error Tolerant Machine Learning Algorithms 

As transistor scaling is coming to a halt, systems today are becoming more and more power limited. Given recent trends in increasing network sizes and the need to process more data (such as Deep Learning and Big Data applications), the cost to store and move data around in a system can far exceed computation costs, prohibiting hardware implementations of machine learning algorithms in embedded applications. 

Recently, there has been an emergence of interest in the field of Approximate Computing, which explores the performance (accuracy) of an algorithm with reduced precision. Convolutional Neural Networks (ConvNets), the current top performing image classification networks, are an example of a class of stochastic algorithms which can tolerate reduced precision for little degradation in algorithmic performance. We propose to reduce the system energy by exploiting error tolerance of the algorithm using approximate memory and interconnect communication design. From a memory designer’s perspective, this is rarely considered a viable option since most general purpose systems require robust storage and communication.

From simulation, we have shown that ConvNets are tolerant to bit flips and reduction in precision [1]. To accurately quantify how allowing higher bit error rates (BERs) with low voltage memory affects classification error rate in ConvNets, a test chip has been taped out to perform stress testing on low leakage single-port SRAMs. The results from this measurement will demonstrate dynamic and leakage energy savings from operating memory at lowest possible voltage subject to a classification error rate.

[1] B. Murmann, D. Bankman, E. Chai, D. Miyashita, and L. Yang, "Mixed-Signal Circuits for Embedded Machine-Learning Applications," Asilomar Conference on Signals, Systems and Computers, Asilomar, CA, Nov. 2015.

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