Scaling Word2Vec on Big Corpus

Word embedding has been well accepted as an important feature in the area of natural language processing (NLP). Specifically, the Word2Vec model learns high-quality word embeddings and is widely used in various NLP tasks. The training of Word2Vec is sequential on a CPU due to strong dependencies between word–context pairs. In this paper, we target to scale Word2Vec on a GPU cluster. To do this, one main challenge is reducing dependencies inside a large training batch. We heuristically design a variation of Word2Vec, which ensures that each word–context pair contains a non-dependent word and a uniformly sampled contextual word. During batch training, we “freeze” the context part and update only on the non-dependent part to reduce conflicts. This variation also directly controls the training iterations by fixing the number of samples and treats high-frequency and low-frequency words equally. We conduct extensive experiments over a range of NLP tasks. The results show that our proposed model achieves a 7.5 times acceleration on 16 GPUs without accuracy drop. Moreover, by using high-level Chainer deep learning framework, we can easily implement Word2Vec variations such as CNN-based subword-level models and achieves similar scaling results.