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BiT: Robustly Binarized Multi-distilled Transformer

Zechun Liu · Barlas Oguz · Aasish Pappu · Lin Xiao · Scott Yih · Meng Li · Raghuraman Krishnamoorthi · Yashar Mehdad

Hall J (level 1) #105

Keywords: [ transformers ] [ compression ] [ BERT ] [ Natural Language Processing ] [ Binary neural networks ]


Modern pre-trained transformers have rapidly advanced the state-of-the-art in machine learning, but have also grown in parameters and computational complexity, making them increasingly difficult to deploy in resource-constrained environments. Binarization of the weights and activations of the network can significantly alleviate these issues, however, is technically challenging from an optimization perspective. In this work, we identify a series of improvements that enables binary transformers at a much higher accuracy than what was possible previously. These include a two-set binarization scheme, a novel elastic binary activation function with learned parameters, and a method to quantize a network to its limit by successively distilling higher precision models into lower precision students. These approaches allow for the first time, fully binarized transformer models that are at a practical level of accuracy, approaching a full-precision BERT baseline on the GLUE language understanding benchmark within as little as 5.9%. Code and models are available at:

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