Infrastructure/software/nltk

Background

The Natural Language Toolkit (NLTK) provides a large collection of core NLP utilities (e.g. sentence splitting and tokenization, part of speech tagging, various approaches to parsing, and many more) in an integrated Python environment. The NLTK distribution also bundles a broad range of common, freely available data sets, which are made accessible through a uniform API. Albeit often neither quite state of the art nor blindingly efficient, NLTK is popular as a teaching environment and go-to repository of common ‘basic’ preprocessing tasks, e.g. sentence splitting, stop word removal, or lemmatization (for English, at least).

Usage on Abel

The module nlpl-nltk provides an NLTK installation in a Python 3.5 virtual environment.

module purge
module use -a /projects/nlpl/software/modulefiles
module load nlpl-nltk

This installation (just as other NLPL-maintained Python virtual environments) can be combined with other Python-based modules, for example the NLPL installations of PyTorch or TensorFlow. To ‘stack’ multiple Python environments, they can simply be loaded together, e.g.

module load nlpl-nltk nlpl-tensorflow

Because PyTorch and TensorFlow are ‘special’ in their requirements for dynamic libraries and support for both cpu and gpu nodes, it is important for them to be activated last, i.e. on the ‘top’ of a multi-module stack. This can be validated by inspecting which python binary is active according to the search order in the $PATH environment variable:

type -all python

In late September 2018, for example, the output from the above command would look as follows:

python is /projects/nlpl/software/tensorflow/1.11/bin/python
python is /projects/nlpl/software/nltk/3.3/bin/python
python is /usr/bin/python
python is /opt/rocks/bin/python

Installation on Abel

module purge
module load python3/3.5.0

mkdir /projects/nlpl/software/nltk
virtualenv /projects/nlpl/software/nltk/3.3

Next, we need to create a module definition, in this case /projects/nlpl/software/modulefiles/nlpl-nltk/3.3; make sure to establish the environment variable $NLTK_DATA, pointing to the data sub-directory of the NLTK tree, as established by the command-line data download below.

module load nlpl-nltk/3.3
pip install --upgrade pip
pip install --upgrade $(pip list | tail -n +3 | gawk '{print $1}')

Finally, install the NLTK code and all data packages.

pip install nltk
python -m nltk.downloader -d /projects/nlpl/software/nltk/3.3/data all