simpletransformers 0.4.3

An easy-to-use wrapper library for the Transformers library.

Simple Transformers

This library is based on the Pytorch-Transformers library by HuggingFace. Using this library, you can quickly train and evaluate Transformer models. Only 3 lines of code are needed to initialize a model, train the model, and evaluate the model on classification tasks.

Table of contents

• Setup
  • With Conda
• Usage
  • Minimal Start
  • Yelp Reviews Dataset
  • Multiclass Classification
  • Default Settings
  • TransformerModel
  • Current Pretrained Models
• Acknowledgements

Setup

With Conda

1. Install Anaconda or Miniconda Package Manager from here

2. Create a new virtual environment and install packages.
   conda create -n transformers python pandas tqdm
conda activate transformers
   If using cuda:
       conda install pytorch cudatoolkit=10.0 -c pytorch
   else:
       conda install pytorch cpuonly -c pytorch
conda install -c anaconda scipy
conda install -c anaconda scikit-learn
pip install transformers
pip install tensorboardx

3. Install Apex if you are using fp16 training. Please follow the instructions here. (Installing Apex from pip has caused issues for several people.)

4. Install simpletransformers.
   pip install simpletransformers

Usage

Minimal Start

from simpletransformers.model import TransformerModel
import pandas as pd


# Train and Evaluation data needs to be in a Pandas Dataframe of two columns. The first column is the text with type str, and the second column is the label with type int.
train_data = [['Example sentence belonging to class 1', 1], ['Example sentence belonging to class 0', 0]]
train_df = pd.DataFrame(train_data)

eval_data = [['Example eval sentence belonging to class 1', 1], ['Example eval sentence belonging to class 0', 0]]
eval_df = pd.DataFrame(eval_data)

# Create a TransformerModel
model = TransformerModel('roberta', 'roberta-base')

# Train the model
model.train_model(train_df)

# Evaluate the model
result, model_outputs, wrong_predictions = model.eval_model(eval_df)

If you wish to add any custom metrics, simply pass them as additional keyword arguments. The keyword is the name to be given to the metric, and the value is the function that will calculate the metric. Make sure that the function expects two parameters with the first one being the true label, and the second being the predictions. (This is the default for sklearn metrics)

import sklearn


result, model_outputs, wrong_predictions = model.eval_model(eval_df, acc=sklearn.metrics.accuracy_score)

To make predictions on arbitary data, the predict(to_predict) function can be used. For a list of text, it returns the model predictions and the raw model outputs.

predictions, raw_outputs = model.predict(['Some arbitary sentence'])

Yelp Reviews Dataset

Please refer to this Medium article for an example of using the library on the Yelp Reviews Dataset.

Multiclass Classification

For multiclass classification, simply pass in the number of classes to the num_labels optional parameter of TransformerModel.

See the tutorial on the AGNews Dataset here for a complete example, or check the minimal example below.

from simpletransformers.model import TransformerModel
import pandas as pd


# Train and Evaluation data needs to be in a Pandas Dataframe containing at least two columns. If the Dataframe has a header, it should contain a 'text' and a 'labels' column. If no header is present, the Dataframe should contain at least two columns, with the first column is the text with type str, and the second column in the label with type int.
train_data = [['Example sentence belonging to class 1', 1], ['Example sentence belonging to class 0', 0], ['Example eval senntence belonging to class 2', 2]]
train_df = pd.DataFrame(train_data)

eval_data = [['Example eval sentence belonging to class 1', 1], ['Example eval sentence belonging to class 0', 0], ['Example eval senntence belonging to class 2', 2]]
eval_df = pd.DataFrame(eval_data)

# Create a TransformerModel
model = TransformerModel('bert', 'bert-base-cased', num_labels=3, args={'reprocess_input_data': True, 'overwrite_output_dir': True})

# Train the model
model.train_model(train_df)

# Evaluate the model
result, model_outputs, wrong_predictions = model.eval_model(eval_df)

predictions, raw_outputs = model.predict(["Some arbitary sentence"])

Default Settings

The default args used are given below. Any of these can be overridden by passing a dict containing the corresponding key: value pairs to the the init method of TransformerModel.

self.args = {
   'output_dir': 'outputs/',
   'cache_dir': 'cache/',

   'fp16': True,
   'fp16_opt_level': 'O1',
   'max_seq_length': 128,
   'train_batch_size': 8,
   'eval_batch_size': 8,
   'gradient_accumulation_steps': 1,
   'num_train_epochs': 1,
   'weight_decay': 0,
   'learning_rate': 4e-5,
   'adam_epsilon': 1e-8,
   'warmup_ratio': 0.06,
   'warmup_steps': 0,
   'max_grad_norm': 1.0,

   'logging_steps': 50,
   'evaluate_during_training': False,
   'save_steps': 2000,
   'eval_all_checkpoints': True,
   'use_tensorboard': True,

   'overwrite_output_dir': False,
   'reprocess_input_data': False,
   'process_count': cpu_count() - 2 if cpu_count() > 2 else 1
}

Args Explained

output_dir: str

The directory where all outputs will be stored. This includes model checkpoints and evaluation results.

cache_dir: str

The directory where cached files will be saved.

fp16: bool

Whether or not fp16 mode should be used. Requires NVidia Apex library.

fp16_opt_level: str

Can be '01', '02', '03'. See the Apex docs for an explanation of the different optimization levels (opt_levels).

max_seq_length: int

Maximum sequence level the model will support.

train_batch_size: int

The training batch size.

gradient_accumulation_steps: int

The number of training steps to execute before performing a optimizer.step(). Effectively increases the training batch size while sacrificing training time to lower memory consumption.

eval_batch_size: int

The evaluation batch size.

num_train_epochs: int

The number of epochs the model will be trained for.

weight_decay: float

Adds L2 penalty.

learning_rate: float

The learning rate for training.

adam_epsilon: float

Epsilon hyperparameter used in AdamOptimizer.

max_grad_norm: float

Maximum gradient clipping.

logging_steps: int

Log training loss and learning at every specified number of steps.

save_steps: int

Save a model checkpoint at every specified number of steps.

overwrite_output_dir: bool

If True, the trained model will be saved to the ouput_dir and will overwrite existing saved models in the same directory.

reprocess_input_data: bool

If True, the input data will be reprocessed even if a cached file of the input data exists in the cache_dir.

process_count: int

Number of cpu cores (processes) to use when converting examples to features. Default is (number of cores - 2) or 1 if (number of cores <= 2)

TransformerModel

class simpletransformers.model.TransformerModel (model_type, model_name, args=None, use_cuda=True)
This is the main class of this library. All configuration, training, and evaluation is performed using this class.

Class attributes

• tokenizer: The tokenizer to be used.
• model: The model to be used. model_name: Default Transformer model name or path to Transformer model file (pytorch_nodel.bin).
• device: The device on which the model will be trained and evaluated.
• results: A python dict of past evaluation results for the TransformerModel object.
• args: A python dict of arguments used for training and evaluation.

Parameters

• model_type: (required) str - The type of model to use. Currently, BERT, XLNet, XLM, and RoBERTa models are available.
• model_name: (required) str - The exact model to use. Could be a pretrained model name or path to a directory containing a model. See Current Pretrained Models for all available models.
• num_labels (optional): The number of labels or classes in the dataset.
• args: (optional) python dict - A dictionary containing any settings that should be overwritten from the default values.
• use_cuda: (optional) bool - Default = True. Flag used to indicate whether CUDA should be used.

class methods
train_model(self, train_df, output_dir=None)

Trains the model using 'train_df'

Args:

train_df: Pandas Dataframe containing at least two columns. If the Dataframe has a header, it should contain a 'text' and a 'labels' column. If no header is present, the Dataframe should contain at least two columns, with the first column containing the text, and the second column containing the label. The model will be trained on this Dataframe.

output_dir: The directory where model files will be saved. If not given, self.args['output_dir'] will be used.

Returns:

None

eval_model(self, eval_df, output_dir=None, verbose=False)

Evaluates the model on eval_df. Saves results to output_dir.

Args:

eval_df: Pandas Dataframe containing at least two columns. If the Dataframe has a header, it should contain a 'text' and a 'labels' column. If no header is present, the Dataframe should contain at least two columns, with the first column containing the text, and the second column containing the label. The model will be evaluated on this Dataframe.

output_dir: The directory where model files will be saved. If not given, self.args['output_dir'] will be used.

verbose: If verbose, results will be printed to the console on completion of evaluation.

Returns:

result: Dictionary containing evaluation results. (Matthews correlation coefficient, tp, tn, fp, fn)

model_outputs: List of model outputs for each row in eval_df

wrong_preds: List of InputExample objects corresponding to each incorrect prediction by the model

predict(self, to_predict)

Performs predictions on a list of text.

Args:

to_predict: A python list of text (str) to be sent to the model for prediction.

Returns:

preds: A python list of the predictions (0 or 1) for each text.
model_outputs: A python list of the raw model outputs for each text.

train(self, train_dataset, output_dir)

Trains the model on train_dataset. Utility function to be used by the train_model() method. Not intended to be used directly.

evaluate(self, eval_df, output_dir, prefix="")

Evaluates the model on eval_df. Utility function to be used by the eval_model() method. Not intended to be used directly

load_and_cache_examples(self, examples, evaluate=False)

Converts a list of InputExample objects to a TensorDataset containing InputFeatures. Caches the InputFeatures. Utility function for train() and eval() methods. Not intended to be used directly

List of InputExample objects corresponding to each incorrect prediction by the model

Computes the evaluation metrics for the model predictions.

Args:

preds: Model predictions

labels: Ground truth labels

eval_examples: List of examples on which evaluation was performed

Returns:

result: Dictionary containing evaluation results. (Matthews correlation coefficient, tp, tn, fp, fn)

wrong: List of InputExample objects corresponding to each incorrect prediction by the model

Current Pretrained Models

The table below shows the currently available model types and their models. You can use any of these by setting the model_type and model_name in the args dictionary. For more information about pretrained models, see HuggingFace docs.

Architecture	Model Type	Model Name	Details
BERT	bert	bert-base-uncased	12-layer, 768-hidden, 12-heads, 110M parameters. Trained on lower-cased English text.
BERT	bert	bert-large-uncased	24-layer, 1024-hidden, 16-heads, 340M parameters. Trained on lower-cased English text.
BERT	bert	bert-base-cased	12-layer, 768-hidden, 12-heads, 110M parameters. Trained on cased English text.
BERT	bert	bert-large-cased	24-layer, 1024-hidden, 16-heads, 340M parameters. Trained on cased English text.
BERT	bert	bert-base-multilingual-uncased	(Original, not recommended) 12-layer, 768-hidden, 12-heads, 110M parameters. Trained on lower-cased text in the top 102 languages with the largest Wikipedias
BERT	bert	bert-base-multilingual-cased	(New, recommended) 12-layer, 768-hidden, 12-heads, 110M parameters. Trained on cased text in the top 104 languages with the largest Wikipedias
BERT	bert	bert-base-chinese	12-layer, 768-hidden, 12-heads, 110M parameters. Trained on cased Chinese Simplified and Traditional text.
BERT	bert	bert-base-german-cased	12-layer, 768-hidden, 12-heads, 110M parameters. Trained on cased German text by Deepset.ai
BERT	bert	bert-large-uncased-whole-word-masking	24-layer, 1024-hidden, 16-heads, 340M parameters. Trained on lower-cased English text using Whole-Word-Masking
BERT	bert	bert-large-cased-whole-word-masking	24-layer, 1024-hidden, 16-heads, 340M parameters. Trained on cased English text using Whole-Word-Masking
BERT	bert	bert-large-uncased-whole-word-masking-finetuned-squad	24-layer, 1024-hidden, 16-heads, 340M parameters. The bert-large-uncased-whole-word-masking model fine-tuned on SQuAD
BERT	bert	bert-large-cased-whole-word-masking-finetuned-squad	24-layer, 1024-hidden, 16-heads, 340M parameters The bert-large-cased-whole-word-masking model fine-tuned on SQuAD
BERT	bert	bert-base-cased-finetuned-mrpc	12-layer, 768-hidden, 12-heads, 110M parameters. The bert-base-cased model fine-tuned on MRPC
XLNet	xlnet	xlnet-base-cased	12-layer, 768-hidden, 12-heads, 110M parameters. XLNet English model
XLNet	xlnet	xlnet-large-cased	24-layer, 1024-hidden, 16-heads, 340M parameters. XLNet Large English model
XLM	xlm	xlm-mlm-en-2048	12-layer, 2048-hidden, 16-heads XLM English model
XLM	xlm	xlm-mlm-ende-1024	6-layer, 1024-hidden, 8-heads XLM English-German Multi-language model
XLM	xlm	xlm-mlm-enfr-1024	6-layer, 1024-hidden, 8-heads XLM English-French Multi-language model
XLM	xlm	xlm-mlm-enro-1024	6-layer, 1024-hidden, 8-heads XLM English-Romanian Multi-language model
XLM	xlm	xlm-mlm-xnli15-1024	12-layer, 1024-hidden, 8-heads XLM Model pre-trained with MLM on the 15 XNLI languages
XLM	xlm	xlm-mlm-tlm-xnli15-1024	12-layer, 1024-hidden, 8-heads XLM Model pre-trained with MLM + TLM on the 15 XNLI languages
XLM	xlm	xlm-clm-enfr-1024	12-layer, 1024-hidden, 8-heads XLM English model trained with CLM (Causal Language Modeling)
XLM	xlm	xlm-clm-ende-1024	6-layer, 1024-hidden, 8-heads XLM English-German Multi-language model trained with CLM (Causal Language Modeling)
RoBERTa	roberta	roberta-base	125M parameters RoBERTa using the BERT-base architecture
RoBERTa	roberta	roberta-large	24-layer, 1024-hidden, 16-heads, 355M parameters RoBERTa using the BERT-large architecture
RoBERTa	roberta	roberta-large-mnli	24-layer, 1024-hidden, 16-heads, 355M parameters roberta-large fine-tuned on MNLI.

Acknowledgements

None of this would have been possible without the hard work by the HuggingFace team in developing the Pytorch-Transformers library.