Regularizing and Optimizing LSTM Language Models

Recurrent neural networks (RNNs), such as long short-term memory networks (LSTMs), serve as a fundamental building block for many sequence learning tasks, including machine translation, language modeling, and question answering. In this paper, we consider the specific problem of word-level language modeling and investigate strategies for regularizing and optimizing LSTM-based models. We propose the weight-dropped LSTM which uses DropConnect on hidden-to-hidden weights as a form of recurrent regularization. Further, we introduce NT-ASGD, a variant of the averaged stochastic gradient method, wherein the averaging trigger is determined using a non-monotonic condition as opposed to being tuned by the user. Using these and other regularization strategies, we achieve state-of-the-art word level perplexities on two data sets: 57.3 on Penn Treebank and 65.8 on WikiText-2. In exploring the effectiveness of a neural cache in conjunction with our proposed model, we achieve an even lower state-of-the-art perplexity of 52.8 on Penn Treebank and 52.0 on WikiText-2.

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Task Dataset Model Metric Name Metric Value Global Rank Result Benchmark
Language Modelling Penn Treebank (Word Level) AWD-LSTM + continuous cache pointer Validation perplexity 53.9 # 13
Test perplexity 52.8 # 17
Params 24M # 7
Language Modelling Penn Treebank (Word Level) AWD-LSTM Validation perplexity 60.0 # 24
Test perplexity 57.3 # 30
Params 24M # 7
Language Modelling WikiText-2 AWD-LSTM Validation perplexity 68.6 # 23
Test perplexity 65.8 # 31
Number of params 33M # 23
Language Modelling WikiText-2 AWD-LSTM + continuous cache pointer Validation perplexity 53.8 # 11
Test perplexity 52.0 # 19
Number of params 33M # 23

Methods