More recently, neural network-based methods have been used for document representation and these include average word embeddings (Mikolov et al., 2013), Doc2Vec (Le and Mikolov, 2014), Skip-Thought vectors (Kiros et al., 2015), recursive neural networkbased methods (Socher et al., 2014), LSTM architectures (Tai et al., 2015), and convolutional neural networks (Blunsom et al., 2014).
it is computationally expensive for long documents (Kusner et al., 2015).