textgenrnn

textgenrnn is a Python 3 module on top of Keras/TensorFlow which can easily generate text using a pretrained recurrent neural network:

from textgenrnn import textgenrnn

textgen = textgenrnn()
textgen.generate()

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The model can easily be trained on new texts, and can generate appropriate text even after a single pass of the input data.

textgen.train_from_file('hacker-news-2000.txt', num_epochs=1)
textgen.generate(5)

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The model weights are very small (845 KB on disk), and they can easily be saved and loaded into a new textgenrnn instance. As a result, you can play with models which have been trained on hundreds of passes through the data.

textgen_2 = textgenrnn('hacker_news_500_epochs.hdf5')
textgen_2.generate(5)

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Usage

textgenrnn can be installed from pypi via pip:

sudo pip3 install textgenrnn

You can view a demo of common features in this Jupyter Notebook. (full documentation coming soon)

/datasets contains example datasets using Hacker News/Reddit data for training textgenrnn.

/weights contains further-pretrained models on the aforementioned datasets which can be loaded into textgenrnn.

/outputs contains examples of text generated from the above pretrained models.

Neural Network Architecture and Implementation

textgenrnn is based off of the char-rnn project by Andrej Karpathy with a few optimizations, such as the ability to work with very small text sequences.

textgenrnn takes in an input of up to 40 characters, converts each character to a 100D character embedding vector, and feeds those into a 128-cell long-short-term-memory layer. That output is mapped to probabilities for up to 394 different characters that they are the next character in the sequence, including uppercase characters, lowercase, punctuation, and emoji.

The model weights included with the package are trained on hundreds of thousands of text documents, from Reddit submissions (via BigQuery) and Facebook Pages (via my Facebook Page Post Scraper), from a very diverse variety of subreddits/Pages. The network was also trained in such a way that the rnn layer is decontextualized in order to both improve training performance and mitigate authorial bias.

When fine-tuning the model on a new dataset of texts, all layers are retrained. However, since the original pretrained network has a much more robust "knowledge" initially, the new textgenrnn trains faster and more accurately in the end, and can potentially learn new relationships not present in the original dataset (e.g. the pretrained character embeddings include the context for the character for all possible types of modern internet grammar).

Additionally, the retraining is done with a momentum-based optimizer and a linearly decaying learning rate, both of which prevent exploding gradients and makes it much less likely that the model diverges after training for a long time.

Notes

• RESULTS WILL VARY GREATLY BETWEEN DATASETS. Because the RNN is relatively small (128 cells), it cannot store as much data as RNNs typically flaunted in blog posts. For best results, use a dataset with atleast 2,000-5,000 documents. If a dataset is smaller, you'll need to train it for longer by setting num_epochs higher when calling a training method. Even then, there is currently no good heuristic for determining a "good" model, and I hope to update this module with a more robust training regimen.

• textgenrnn is less effective when training on/predicting longer sequences (> 200 characters). Likewise textgenrnn is less effective when training on/predicting texts with very disparate grammatical styles. If a source dataset has both, it may lead to unexpected results.

• A GPU is not required to retrain textgenrnn, but it may take awhile to train on a CPU. If you do use a GPU, I recommend increasing the batch_size for better hardware utilization. Additionally, I recommend using the CNTK backend for Keras, as it trains recurrent neural networks much faster than TensorFlow.

Future Plans for textgenrnn

• A web-based implementation using Keras.js (works especially well due to the network's small size)

• A way to visualize the outputs of the RNN's neurons to see how the network "learns."

• A larger pretrained network which can accommodate longer character sequences and a more indepth understanding of language, creating better generated sentences. This may be released as a commercial product instead, if any venture capitalists are interested.

Maintainer/Creator

Max Woolf (@minimaxir)

Max's open-source projects are supported by his Patreon. If you found this project helpful, any monetary contributions to the Patreon are appreciated and will be put to good creative use.

Credits

Andrej Karpathy for the original proposal of the char-rnn via the blog post The Unreasonable Effectiveness of Recurrent Neural Networks.