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Language Model Wiki-103

Step 1: Download and clean the data, prepare subword model​

Preliminary steps are defined in the prepare_wikitext-103_data.sh script.

The following command will download the WikiText103 dataset, remove empty lines and shuffle the training corpus. It will also call the learn_bpe.py script to train a bpe of 40000 symbols on the training dataset using pyonmttok. The bpe model will be stored in data/wikitext/wikitext-103-raw-v1/subwords.bpe.

chmod u+x prepare_wikitext-103_data.sh
./prepare_wikitext-103_data.sh

Step 2: Build the vocabulary​

An example of yaml configuration for language modeling task is available in wiki_103.yaml. This configuration will be used for building the vocabulary and training the model. BPE and language modeling specificities are explained in the following sections.

Language Model specificities​

In LM tasks we expect a single source, therefore path_tgt is not required for LM tasks.

data:
    corpus_1:
        path_src: data/wikitext-103-raw/wiki.train.raw

BPE specificities​

To use BPE tokenization on the fly, the following parameters must be in the config file. Slight differences between on the fly tokenization and outputed tokenized files from step 1 can be observed.

transforms: [onmt_tokenize, filtertoolong]
transforms_configs:
  onmt_tokenize:
    src_subword_type: bpe
    src_subword_model: data/wikitext-103-raw/subwords.bpe
    src_onmttok_kwargs: {"mode": "aggressive", "joiner_annotate": True, "preserve_placeholders":
    True, "case_markup": True, "soft_case_regions": True, "preserve_segmented_tokens":
    True}

Build vocabulary command​

The vocabulary is built using:

eole build_vocab -config wiki_103.yaml -n_sample -1 # -n_threads 4

Step 3: Train the model​

The training is launched using:

eole train -config wiki_103.yaml

Tensorboard can be used to monitor the training.

Expected results: perplexity of 20-22 on the validation set.

Step 4: Generate output​

Options contained in the loaded model will trigger language modeling specific inference.

input.txt must contain already tokenized examples, with the same method as the training data. Here, part of validation data will be used:

head data/wikitext-103-raw/wiki.valid.bpe | cut -d" " -f-15 > data/wikitext/wikitext-103-raw-v1/test_input.txt

To proceed with LM inference, sampling methods such as top-k sampling or nucleus sampling are usually applied. Details and options about inference methods can be found in eole/config/inference.py.

The following command will provide inference with nucleus sampling of p=0.9 and return the 3 sequences with the lowest perplexity out of the 10 generated sequences (see inference.yaml):

eole predict -config inference.yaml -model_path data/wikitext/wikitext-103-raw-v1/run/model-lm/step_1000000 -src data/wikitext/wikitext-103-raw-v1/test_input.txt -output data/wikitext/wikitext-103-raw-v1/test_pred.txt