Long short-term memory networks in memristor crossbar arrays


Recent breakthroughs in recurrent deep neural networks with long short-term memory (LSTM) units have led to major advances in artificial intelligence. However, state-of-the-art LSTM models with significantly increased complexity and a large number of parameters have a bottleneck in computing power resulting from both limited memory capacity and limited data communication bandwidth. Here we demonstrate experimentally that the synaptic weights shared in different time steps in an LSTM can be implemented with a memristor crossbar array, which has a small circuit footprint, can store a large number of parameters and offers in-memory computing capability that contributes to circumventing the ‘von Neumann bottleneck’. We illustrate the capability of our crossbar system as a core component in solving real-world problems in regression and classification, which shows that memristor LSTM is a promising low-power and low-latency hardware platform for edge inference.

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Fig. 1: Schematic architecture of memristor accelerated LSTM network.
Fig. 2: LSTM units implemented in a memristor crossbar array.
Fig. 3: Regression experiment for predicting the next month’s number of airline passengers.
Fig. 4: Classification experiment for human identification by gait.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request. The code that supports the plots within this Article and other finding of this study is available at http://github.com/lican81/memNN. The code that supports the communication between the custom-built measurement system and the integrated chip is available from the corresponding author upon reasonable request.


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This work was supported in part by the US Air Force Research Laboratory (grant no. FA8750-15-2-0044) and the Intelligence Advanced Research Projects Activity (IARPA; contract no. 2014-14080800008). D.B., an undergraduate from Swarthmore College, was supported by the NSF Research Experience for Undergraduates (grant no. ECCS-1253073) at the University of Massachusetts. P.Y. was visiting from Huazhong University of Science and Technology with support from the Chinese Scholarship Council (grant no. 201606160074). Part of the device fabrication was conducted in the cleanroom of the Center for Hierarchical Manufacturing, an NSF Nanoscale Science and Engineering Center located at the University of Massachusetts Amherst.

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Q.X. and C.L. conceived the idea. Q.X., J.J.Y. and C.L. designed the experiments. C.L., Z.W. and D.B. carried out programming, measurements, data analysis and simulation. M.R., P.Y., C.L., H.J., N.G. and P.L. built the integrated chips. Y.L., C.L., W.S., M.H., Z.W. and J.P.S. built the measurement system and firmware. Q.X., C.L., J.J.Y. and R.S.W. wrote the manuscript. M.B., Q.W. and all other authors contributed to the results analysis and commented on the manuscript.

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Correspondence to J. Joshua Yang or Qiangfei Xia.

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Li, C., Wang, Z., Rao, M. et al. Long short-term memory networks in memristor crossbar arrays. Nat Mach Intell 1, 49–57 (2019). https://doi.org/10.1038/s42256-018-0001-4

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