Introduction

The Transformers repository from “Hugging Face” comprises a whole lot of prepared to make use of, state-of-the-art fashions, that are easy to obtain and fine-tune with Tensorflow & Keras.

For this goal the customers often must get:

• The mannequin itself (e.g. Bert, Albert, RoBerta, GPT-2 and and so forth.)
• The tokenizer object
• The weights of the mannequin

On this put up, we’ll work on a traditional binary classification activity and practice our dataset on 3 fashions:

Nevertheless, readers ought to know that one can work with transformers on a wide range of down-stream duties, akin to:

1. characteristic extraction
2. sentiment evaluation
3. textual content classification
4. query answering
5. summarization
6. translation and many extra.

Stipulations

Our first job is to put in the transformers package deal through reticulate.

reticulate::py_install('transformers', pip = TRUE)

Then, as regular, load normal ‘Keras’, ‘TensorFlow’ >= 2.0 and a few traditional libraries from R.

Observe that if operating TensorFlow on GPU one may specify the next parameters with the intention to keep away from reminiscence points.

physical_devices = tf$config$list_physical_devices('GPU')
tf$config$experimental$set_memory_growth(physical_devices[[1]],TRUE)

tf$keras$backend$set_floatx('float32')

Template

We already talked about that to coach an information on the particular mannequin, customers ought to obtain the mannequin, its tokenizer object and weights. For instance, to get a RoBERTa mannequin one has to do the next:

# get Tokenizer
transformer$RobertaTokenizer$from_pretrained('roberta-base', do_lower_case=TRUE)

# get Mannequin with weights
transformer$TFRobertaModel$from_pretrained('roberta-base')

Information preparation

A dataset for binary classification is offered in text2vec package deal. Let’s load the dataset and take a pattern for quick mannequin coaching.

Cut up our information into 2 components:

idx_train = pattern.int(nrow(df)*0.8)

practice = df[idx_train,]
check = df[!idx_train,]

Information enter for Keras

Till now, we’ve simply lined information import and train-test cut up. To feed enter to the community we have now to show our uncooked textual content into indices through the imported tokenizer. After which adapt the mannequin to do binary classification by including a dense layer with a single unit on the finish.

Nevertheless, we need to practice our information for 3 fashions GPT-2, RoBERTa, and Electra. We have to write a loop for that.

Observe: one mannequin normally requires 500-700 MB

# record of three fashions
ai_m = record(
  c('TFGPT2Model',       'GPT2Tokenizer',       'gpt2'),
   c('TFRobertaModel',    'RobertaTokenizer',    'roberta-base'),
   c('TFElectraModel',    'ElectraTokenizer',    'google/electra-small-generator')
)

# parameters
max_len = 50L
epochs = 2
batch_size = 10

# create a listing for mannequin outcomes
gather_history = record()

for (i in 1:size(ai_m)) {
  
  # tokenizer
  tokenizer = glue::glue("transformer${ai_m[[i]][2]}$from_pretrained('{ai_m[[i]][3]}',
                         do_lower_case=TRUE)") %>% 
    rlang::parse_expr() %>% eval()
  
  # mannequin
  model_ = glue::glue("transformer${ai_m[[i]][1]}$from_pretrained('{ai_m[[i]][3]}')") %>% 
    rlang::parse_expr() %>% eval()
  
  # inputs
  textual content = record()
  # outputs
  label = record()
  
  data_prep = perform(information) {
    for (i in 1:nrow(information)) {
      
      txt = tokenizer$encode(information[['comment_text']][i],max_length = max_len, 
                             truncation=T) %>% 
        t() %>% 
        as.matrix() %>% record()
      lbl = information[['target']][i] %>% t()
      
      textual content = textual content %>% append(txt)
      label = label %>% append(lbl)
    }
    record(do.name(plyr::rbind.fill.matrix,textual content), do.name(plyr::rbind.fill.matrix,label))
  }
  
  train_ = data_prep(practice)
  test_ = data_prep(check)
  
  # slice dataset
  tf_train = tensor_slices_dataset(record(train_[[1]],train_[[2]])) %>% 
    dataset_batch(batch_size = batch_size, drop_remainder = TRUE) %>% 
    dataset_shuffle(128) %>% dataset_repeat(epochs) %>% 
    dataset_prefetch(tf$information$experimental$AUTOTUNE)
  
  tf_test = tensor_slices_dataset(record(test_[[1]],test_[[2]])) %>% 
    dataset_batch(batch_size = batch_size)
  
  # create an enter layer
  enter = layer_input(form=c(max_len), dtype='int32')
  hidden_mean = tf$reduce_mean(model_(enter)[[1]], axis=1L) %>% 
    layer_dense(64,activation = 'relu')
  # create an output layer for binary classification
  output = hidden_mean %>% layer_dense(items=1, activation='sigmoid')
  mannequin = keras_model(inputs=enter, outputs = output)
  
  # compile with AUC rating
  mannequin %>% compile(optimizer= tf$keras$optimizers$Adam(learning_rate=3e-5, epsilon=1e-08, clipnorm=1.0),
                    loss = tf$losses$BinaryCrossentropy(from_logits=F),
                    metrics = tf$metrics$AUC())
  
  print(glue::glue('{ai_m[[i]][1]}'))
  # practice the mannequin
  historical past = mannequin %>% keras::match(tf_train, epochs=epochs, #steps_per_epoch=len/batch_size,
                validation_data=tf_test)
  gather_history[[i]]<- historical past
  names(gather_history)[i] = ai_m[[i]][1]
}

Extract outcomes to see the benchmarks:

Each the RoBERTa and Electra fashions present some further enhancements after 2 epochs of coaching, which can’t be stated of GPT-2. On this case, it’s clear that it may be sufficient to coach a state-of-the-art mannequin even for a single epoch.

Conclusion

On this put up, we confirmed methods to use state-of-the-art NLP fashions from R.
To know methods to apply them to extra complicated duties, it’s extremely advisable to assessment the transformers tutorial.

We encourage readers to check out these fashions and share their outcomes beneath within the feedback part!

Corrections

For those who see errors or need to counsel modifications, please create a problem on the supply repository.

Reuse

Textual content and figures are licensed beneath Inventive Commons Attribution CC BY 4.0. Supply code is accessible at https://github.com/henry090/transformers, except in any other case famous. The figures which have been reused from different sources do not fall beneath this license and will be acknowledged by a notice of their caption: “Determine from …”.

Quotation

For attribution, please cite this work as

Abdullayev (2020, July 30). Posit AI Weblog: State-of-the-art NLP fashions from R. Retrieved from https://blogs.rstudio.com/tensorflow/posts/2020-07-30-state-of-the-art-nlp-models-from-r/

BibTeX quotation

@misc{abdullayev2020state-of-the-art,
  writer = {Abdullayev, Turgut},
  title = {Posit AI Weblog: State-of-the-art NLP fashions from R},
  url = {https://blogs.rstudio.com/tensorflow/posts/2020-07-30-state-of-the-art-nlp-models-from-r/},
  12 months = {2020}
}