Multi-Task-Learning BiLSTM-CNN-CRF

The network can be used to perform multi-task learning.

See Train_MultiTask.py for an example.

You specify the different datasets using the datasets variable:

datasets = {
    'unidep_pos':
        {'columns': {1:'tokens', 3:'POS'},
         'label': 'POS',
         'evaluate': True,
         'commentSymbol': None},
    'conll2000_chunking':
        {'columns': {0:'tokens', 2:'chunk_BIO'},
         'label': 'chunk_BIO',
         'evaluate': True,
         'commentSymbol': None},
}

Here we specify to train on the two datasets unidep_pos and conll2000_chunking. The format of this dictionary is as described in Training.md.

Note: If columns in two datasets have the same name, then they are mapped to the same embeddings space. I.e., if columns have the same names, ensure that they have the same content. It would not be advisable to name your label column label in all datasets.

The variable evaluate can be set to False for Multi-Task Learning setups: Then, the networks trains on this dataset, however, it is not evaluated on the development and test set for this dataset. This can be useful for example if you have a main task and some auxiliary tasks.

Multi-Task Specific Hyperparameters

You can use the hyperparameter customClassifier to specify custom classifiers for all your different datasets.

See Train_MultiTask_Different_Levels.py for an example. In that file, we pass the following parameters to the network:

params = {'classifier': ['CRF'], 'LSTM-Size': [100], 'dropout': (0.25, 0.25),
          'customClassifier': {'unidep_pos': ['Softmax'], 'conll2000_chunking': [('LSTM', 50), 'CRF']}}

For our POS-task (unidep_pos) we specify a simple softmax classifier. However, the chunking task (conll2000_chunking) has a task-specific LSTM-layer with 50 recurrent units followed by a CRF-classifier.

Using this technique, you can implement the technique that is described in this paper: Sogard, Goldberg: Deep multi-task learning with low level tasks supervised at lower layers