TechTalks from event: ICML 2011

Neural Networks and NLP

  • Parsing Natural Scenes and Natural Language with Recursive Neural Networks Authors: Richard Socher; Cliff Chiung-Yu Lin; Andrew Ng; Chris Manning
    Recursive structure is commonly found in the inputs of different modalities such as natural scene images or natural language sentences. Discovering this recursive structure helps us to not only identify the units that an image or sentence contains but also how they interact to form a whole. We introduce a max-margin structure prediction architecture based on recursive neural networks that can successfully recover such structure both in complex scene images as well as sentences. The same algorithm can be used both to provide a competitive syntactic parser for natural language sentences from the Penn Treebank and to outperform alternative approaches for semantic scene segmentation, annotation and classification. For segmentation and annotation our algorithm obtains a new level of state-of-the-art performance on the Stanford background dataset (78.1%). The features from the image parse tree outperform Gist descriptors for scene classification by 4%.
  • Domain Adaptation for Large-Scale Sentiment Classification: A Deep Learning Approach Authors: Xavier Glorot; Antoine Bordes; Yoshua Bengio
    The exponential increase in the availability of online reviews and recommendations makes sentiment classification an interesting topic in academic and industrial research. Reviews can span so many different domains that it is difficult to gather annotated training data for all of them. Hence, this paper studies the problem of domain adaptation for sentiment classifiers, hereby a system is trained on labeled reviews from one source domain but is meant to be deployed on another. We propose a deep learning approach which learns to extract a meaningful representation for each review in an unsupervised fashion. Sentiment classifiers trained with this high-level feature representation clearly outperform state-of-the-art methods on a benchmark composed of reviews of 4 types of Amazon products. Furthermore, this method scales well and allowed us to successfully perform domain adaptation on a larger industrial-strength dataset of 22 domains.
  • Large-Scale Learning of Embeddings with Reconstruction Sampling Authors: Yann Dauphin; Xavier Glorot; Yoshua Bengio
    In this paper, we present a novel method to speed up the learning of embeddings for large-scale learning tasks involving very sparse data, as is typically the case for Natural Language Processing tasks. Our speed-up method has been developed in the context of Denoising Auto-encoders, which are trained in a purely unsupervised way to capture the input distribution, and learn embeddings for words and text similar to earlier neural language models. The main contribution is a new method to approximate reconstruction error by a sampling procedure. We show how this approximation can be made to obtain an unbiased estimator of the training criterion, and we show how it can be leveraged to make learning much more computationally efficient. We demonstrate the effectiveness of this method on the Amazon and RCV1 NLP datasets. Instead of reducing vocabulary size to make learning practical, our method allows us to train using very large vocabularies. In particular, reconstruction sampling requires 22x less training time on the full Amazon dataset.
  • Generating Text with Recurrent Neural Networks Authors: Ilya Sutskever; James Martens; Geoffrey Hinton
    Recurrent Neural Networks (RNNs) are very powerful sequence models that do not enjoy widespread use because it is extremely difficult to train them properly. Fortunately, recent advances in Hessian-free optimization have been able to overcome the difficulties associated with training RNNs, making it possible to apply them successfully to challenging sequence problems. In this paper we demonstrate the power of RNNs trained with the new Hessian-Free optimizer (HF) by applying them to character-level language modeling tasks. The standard RNN architecture, while effective, is not ideally suited for such tasks, so we introduce a new RNN variant that uses multiplicative (or ``gated'') connections which allow the current input character to determine the transition matrix from one hidden state vector to the next. After training the multiplicative RNN with the HF optimizer for five days on 8 high-end Graphics Processing Units, we were able to surpass the performance of the best previous single method for character-level language modeling -- a hierarchical non-parametric sequence model. To our knowledge this represents the largest recurrent neural network application to date.
  • Contractive Auto-Encoders: Explicit Invariance During Feature Extraction Authors: Salah Rifai; Pascal Vincent; Xavier Muller; Xavier Glorot; Yoshua Bengio
    We present in this paper a novel approach for training deterministic auto-encoders. We show that by adding a well chosen penalty term to the classical reconstruction cost function, we can achieve results that equal or surpass those attained by other regularized auto-encoders as well as denoising auto-encoders on a range of datasets. This penalty term corresponds to the Frobenius norm of the Jacobian matrix of the encoder activations with respect to the input. We show that this penalty term results in a localized space contraction which in turn yields robust features on the activation layer. Furthermore, we show how this penalty term is related to both regularized auto-encoders and denoising auto-encoders and how it can be seen as a link between deterministic and non-deterministic auto-encoders. We find empirically that this penalty helps to carve a representation that better captures the local directions of variation dictated by the data, corresponding to a lower-dimensional non-linear manifold, while being more invariant to the vast majority of directions orthogonal to the manifold. Finally, we show that by using the learned features to initialize an MLP, we achieve state of the art classification error on a range of datasets, surpassing other methods of pre-training.