BP-Transformer: Modelling Long-Range Context via Binary Partitioning

11 Nov 2019  ·  Zihao Ye, Qipeng Guo, Quan Gan, Xipeng Qiu, Zheng Zhang ·

The Transformer model is widely successful on many natural language processing tasks. However, the quadratic complexity of self-attention limit its application on long text. In this paper, adopting a fine-to-coarse attention mechanism on multi-scale spans via binary partitioning (BP), we propose BP-Transformer (BPT for short). BPT yields $O(k\cdot n\log (n/k))$ connections where $k$ is a hyperparameter to control the density of attention. BPT has a good balance between computation complexity and model capacity. A series of experiments on text classification, machine translation and language modeling shows BPT has a superior performance for long text than previous self-attention models. Our code, hyperparameters and CUDA kernels for sparse attention are available in PyTorch.

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Task Dataset Model Metric Name Metric Value Global Rank Benchmark
Sentiment Analysis IMDb BP-Transformer + GloVe Accuracy 92.12 # 24
Machine Translation IWSLT2015 Chinese-English BP-Transformer BLEU 19.84 # 1
Sentiment Analysis SST-5 Fine-grained classification BP-Transformer + GloVe Accuracy 52.71 # 14
Language Modelling Text8 BP-Transformer - 12 Layers Bit per Character (BPC) 1.11 # 8

Results from Other Papers

Task Dataset Model Metric Name Metric Value Rank Source Paper Compare
Language Modelling enwik8 BP-Transformer (12 layers) Bit per Character (BPC) 1.02 # 20
Number of params 38M # 32