OpenGrm installation instructions

This document covers installation of two libraries: NGram, a C++ library for building finite-state language models, and Pynini, a Python library for finite-state grammar development. Both are part of the OpenGrm project and depend on OpenFst, another C++ library.

The easy way

The easiest way to install these dependencies is via Anaconda. If you already have a working conda installation, you can just issue the following command:

$ conda install ngram pynini -c conda-forge

to install all the libraries you'll need.

The hard way

To begin installation, you will need:

Python 3.6 or better:
A compiler that supports C++11, C99, and POSIX:
1. On Windows 10, install the Windows Subsystem for Linux.
2. On Mac OS X, in a terminal window, type xcode-select --install and follow the prompts.
3. On Linux, install the appropriate package from your distribution; for instance for Ubuntu, type sudo apt install build-essential and follow the prompts.

OpenFst

OpenFst is a C++ library which acts as a backend for both tools.

Visit http://www.openfst.org. Click on "Download", then click on the link for the current version (openfst-1.7.5.tar.gz) and save the file to your hard drive.
In your terminal window, navigate to the directory containing the file you just downloaded and decompress it:
```
$ tar xvzf openfst-1.7.5.tar.gz
```
This will create a directory called openfst-1.7.5; enter it:
```
$ cd openfst-1.7.5
```

Issue the following commands to compile and install it:

$ ./configure --enable-grm && make -j4 && sudo make -j4 install

NGram

Visit http://ngram.opengrm.org. Click on "Download", then click on the link for the current version (opengrm-ngram-1.3.8.tar.gz) and save the file to your hard drive.
In your terminal window, navigate to the directory containing the file you just downloaded and decompress it:
```
$ tar xvzf ngram-1.3.8.tar.gz
```
This will create a directory called ngram-1.3.8; enter it:
```
$ cd ngram-1.3.8
```
Issue the following commands to compile and install it:
```
$ ./configure && make -j4 && sudo make -j4 install
```

Pynini

Pynini is a Python library for finite-state grammar compilation.

Visit http://pynini.opengrm.org. Click on "Download", then click on the link for the current version (pynini-2.0.9.post2.tar.gz) and save the file to your hard drive.
In your terminal window, navigate to the directory containing the file you just downloaded and decompress it:
```
$ tar xvzf pynini-2.0.9.post2.tar.gz
```
This will create a directory called pynini-2.0.9.post2; enter it:
```
$ cd pynini-2.0.9.post2
```
Issue the following commands to compile and install it:
```
$ python setup.py install
```
If you are on Mac OS X and encounter an error here, try the following instead:
```
$ CFLAGS=-stdlib=libc++ python setup.py install
```

Testing

To test Pynini, open Python (or a Jupyter notebook) and execute import pynini.
To test NGram, open a terminal window and execute ngraminfo --helpshort.

Notes

You can delete all the temporary files (both the .tar.gz files and the directories) once these steps are complete.
If you plan to use Pynini in combination with Jupyter, you may wish to install GraphViz, which will allow you to visualize FSTs from within a notebook.