Book Image

Natural Language Processing with TensorFlow

By : Motaz Saad, Thushan Ganegedara
Book Image

Natural Language Processing with TensorFlow

By: Motaz Saad, Thushan Ganegedara

Overview of this book

Natural language processing (NLP) supplies the majority of data available to deep learning applications, while TensorFlow is the most important deep learning framework currently available. Natural Language Processing with TensorFlow brings TensorFlow and NLP together to give you invaluable tools to work with the immense volume of unstructured data in today’s data streams, and apply these tools to specific NLP tasks. Thushan Ganegedara starts by giving you a grounding in NLP and TensorFlow basics. You'll then learn how to use Word2vec, including advanced extensions, to create word embeddings that turn sequences of words into vectors accessible to deep learning algorithms. Chapters on classical deep learning algorithms, like convolutional neural networks (CNN) and recurrent neural networks (RNN), demonstrate important NLP tasks as sentence classification and language generation. You will learn how to apply high-performance RNN models, like long short-term memory (LSTM) cells, to NLP tasks. You will also explore neural machine translation and implement a neural machine translator. After reading this book, you will gain an understanding of NLP and you'll have the skills to apply TensorFlow in deep learning NLP applications, and how to perform specific NLP tasks.
Table of Contents (16 chapters)
Natural Language Processing with TensorFlow
Contributors
Preface
Index

Perplexity – measuring the quality of the text result


It is not just enough to produce text; we also need a way to measure the quality of the produced text. One such way is to measure how surprised or perplexed the RNN was to see the output given the input. That is, if the cross-entropy loss for an input xi and its corresponding output yi is , then the perplexity would be as follows:

Using this, we can compute the average perplexity for a training dataset of size N with the following:

In Figure 6.12, we show the behavior of the training and validation perplexities over time. We can see that the train perplexity goes down over time steadily, where the validation perplexity is fluctuating significantly. This is expected because what we are essentially evaluating in the validation perplexity is our RNN's ability to predict a unseen text based on our learning on training data. Since language can be quite difficult to model, this is a very difficult task, and these fluctuations are natural:

Figure...