Ersatz is a simple, language-agnostic toolkit for both training sentence segmentation models as well as providing pretrained, high-performing models for sentence segmentation in a multilingual setting.

For more information, please see:

• Rachel Wicks and Matt Post (2021) : A unified approach to sentence segmentation of punctuated text in many languages In Proceedings of ACL.

QUICK START

Install

Install the Python (3.7+) module via pip

pip install ersatz

or from source

python setup.py install

Splitting

Ersatz can accept input from either standard input, or via a file path. Similarly, it produces output in the same manner:

cat raw.txt | ersatz > output.txt

ersatz --input raw.txt --output output.txt

To use a specific model (rather than the default), you can pass a name via --model_name, or a path via --model_path

Scoring

Ersatz also provides a simple scoring script which computes F1 from a given segmented file.

ersatz_score GOLD_STANDARD_FILE FILE_TO_SCORE

The above will print all errors as well as additional metrics at bottom. The accompanying test suite can be found here.

Training a Model

Data Preprocessing

Vocabulary

Requires uses a pretrained sentencepiece model that has had --eos_piece replaced with <eos> and --bos_piece replaced with <mos>.

spm_train --input $TRAIN_DATA_PATH \
   --model_prefix ersatz \
   --bos_piece "<mos>" \
   --eos_piece "<eos>"

Create training data

This pipeline takes a raw text file with one sentence per line (to use as labels) and creates a new raw text file with the appropriate left/right context and labels. One line is one training example. User is expected to shuffle this file manually (ie via shuf) after creation.

1. To create:

python dataset.py \
    --sentencepiece_path $SPM_PATH \
    --left-size $LEFT_SIZE \
    --right-size $RIGHT_SIZE \
    --output_path $OUTPUT_PATH \
    $INPUT_TRAIN_FILE_PATHS


shuf $OUTPUT_PATH > $SHUFFLED_TRAIN_OUTPUT_PATH

2. Repeat for validation data

python dataset.py \
    --sentencepiece_path $SPM_PATH \
    --left-size $LEFT_SIZE \
    --right-size $RIGHT_SIZE \
    --output_path $VALIDATION_OUTPUT_PATH \
    $INPUT_DEV_FILE_PATHS

Training

Something like:

        python trainer.py \
        --sentencepiece_path=$vocab_path \
        --left_size=$left_size \
        --right_size=$right_size \
        --output_path=$out \
        --transformer_nlayers=$transformer_nlayers \
        --activation_type=$activation_type \
        --linear_nlayers=$linear_nlayers \
        --min-epochs=$min_epochs \
        --max-epochs=$max_epochs \
        --lr=$lr \
        --dropout=$dropout \
        --embed_size=$embed_size \
        --factor_embed_size=$factor_embed_size \
        --source_factors \
        --nhead=$nhead \
        --log_interval=$log_interval \
        --validation_interval=$validation_interval \
        --eos_weight=$eos_weight \
        --early_stopping=$early_stopping \
        --tb_dir=$LOGDIR \
        $train_path \
        $valid_path

Splitting with a Pre-Trained Model

1. Expects a model_path (should probably change to a default in expected folder location...)
2. ersatz reads from either stdin or a file path (via --input).
3. ersatz writes to either stdout or a file path (via --output).
4. An alternate candidate set for splitting may be given using --determiner_type
   • multilingual (default) is as described in paper
   • en requires a space following punctuation
   • all a space between any two characters
   • Custom can be written that uses the determiner.Split() base class
5. By default, expects raw sentences. Splitting a .tsv is also a supported behavior.
   1. --text_ids expects a comma separated list of column indices to split
   2. --delim changes the delimiter character (default is \t)
6. Uses gpu if available, to force cpu, use --cpu

Example usage

Typical python usage:

python split.py --input unsegmented.txt --output sentences.txt ersatz.model

std[in,out] usage:

cat unsegmented.txt | split.py ersatz.model > sentences.txt

To split .tsv file:

cat unsegmented.tsv | split.py ersatz.model --text_ids 1 > sentences.txt

Scoring a Model's Output

python score.py [gold_standard_file_path] [file_to_score]

(There are legacy arguments, but they're not used)