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Deep Equilibrium Models

2019-09-03NeurIPS 2019Code Available1· sign in to hype

Shaojie Bai, J. Zico Kolter, Vladlen Koltun

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Abstract

We present a new approach to modeling sequential data: the deep equilibrium model (DEQ). Motivated by an observation that the hidden layers of many existing deep sequence models converge towards some fixed point, we propose the DEQ approach that directly finds these equilibrium points via root-finding. Such a method is equivalent to running an infinite depth (weight-tied) feedforward network, but has the notable advantage that we can analytically backpropagate through the equilibrium point using implicit differentiation. Using this approach, training and prediction in these networks require only constant memory, regardless of the effective "depth" of the network. We demonstrate how DEQs can be applied to two state-of-the-art deep sequence models: self-attention transformers and trellis networks. On large-scale language modeling tasks, such as the WikiText-103 benchmark, we show that DEQs 1) often improve performance over these state-of-the-art models (for similar parameter counts); 2) have similar computational requirements to existing models; and 3) vastly reduce memory consumption (often the bottleneck for training large sequence models), demonstrating an up-to 88% memory reduction in our experiments. The code is available at https://github.com/locuslab/deq .

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Benchmark Results

DatasetModelMetricClaimedVerifiedStatus
Penn Treebank (Word Level)DEQ-TrellisNetTest perplexity57.1Unverified
WikiText-103DEQ-Transformer (medium, adaptive embed)Test perplexity23.2Unverified
WikiText-103DEQ-TrellisNetTest perplexity29Unverified
WikiText-103DEQ-Transformer (small)Test perplexity32.4Unverified

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