This project has retired. For details please refer to its Attic page.
Joshua Documentation | Building a language pack

Released November 5, 2015

Building a language pack

The information in this page applies to Joshua 6.0.3 and greater.

Joshua distributes language packs, which are models that have been trained and tuned for particular language pairs. You can easily create your own language pack after you have trained and tuned a model using the provided $JOSHUA/scripts/support/ script, which gathers files from a pipeline training directory and bundles them together for easy distribution and release.

The script takes just two mandatory arguments in the following order:

  1. The path to the Joshua configuration file to base the bundle on. This file should contain the tuned weights from the tuning run, so you can use either the final tuned file from the tuning run (tune/ or from the test run (test/model/joshua.config).
  2. The directory to place the language pack in. If this directory already exists, the script will die, unless you also pass --force.

In addition, there are a number of other arguments that may be important.

  • --root /path/to/root. If file paths in the Joshua config file are not absolute, you need to provide relative root. If you specify a tuned pipeline file (such as tune/ above), the paths should all be absolute. If you instead provide a config file from a previous run bundle (e.g., test/model/joshua.config), the bundle directory above is the relative root.

  • The config file options that are used in the pipeline are likely not the ones you want if you release a model. For example, the tuning configuration file contains options that tell Joshua to output 300 translation candidates for each sentence (-top-n 300) and to include lots of detail about each translation (-output-format '%i ||| %s ||| %f ||| %c'). Because of this, you will want to tell the run bundler to change many of the config file options to be more geared towards human-readable output. The default copy-config options are options are -top-n 0 -output-format %S -mark-oovs false, which accomplishes exactly this (human readability).

  • A very important issue has to do with the translation model (the “TM”, also sometimes called the grammar or phrase table). The translation model can be very large, so that it takes a long time to load and to pack. To reduce this time during model training, the translation model is filtered against the tuning and testing data in the pipeline, and these filtered models will be what is listed in the source config files. However, when exporting a model for use as a language pack, you need to export the full model instead of the filtered one so as to maximize your coverage on new test data. The --tm parameter is used to accomplish this; it takes an argument specifying the path to the full model. If you would additionally like the large model to be packed (this is recommended; it reformats the TM so that it can be quickly loaded at run time), you can use --pack-tm instead. You can only pack one TM (but typically there is only TM anyway). Multiple --tm parameters can be passed; they will replace TMs found in the config file in the order they are found.

Here is an example invocation for packing a hierarchical model using the final tuned Joshua config file:

./ \
  --force --verbose \
  /path/to/rundir/tune/ \
  language-pack-YYYY-MM-DD \
  --root /path/to/rundir \
  --pack-tm /path/to/rundir/grammar.gz \
  --copy-config-options \ 
    '-top-n 1 -output-format %S -mark-oovs false' \
  --server-port 5674

The copy config options tell the decoder to present just the single-best (-top-n 0) translated output string that has been heuristically capitalized (-output-format %S), to not append _OOV to OOVs (-mark-oovs false), and to use the translation model /path/to/rundir/grammar.gz as the main translation model, packing it before placing it in the bundle. Note that these arguments to --copy-config are the default, so you could leave this off entirely. See this page for a longer list of decoder options.

This command is a slight variation used for phrase-based models, which instead takes the test-set Joshua config (the result is the same):

./ \
  --force --verbose \
  /path/to/rundir/test/model/joshua.config \
  --root /path/to/rundir/test/model \
  language-pack-YYYY-MM-DD \
  --pack-tm /path/to/rundir/model/phrase-table.gz \
  --server-port 5674

In both cases, a new directory language-pack-YYYY-MM-DD will be created along with a README and a number of support files.