---
license: mit
language:
- vi
pipeline_tag: token-classification
tags:
- vietnamese
- accents inserter
metrics:
- accuracy
---

# A Transformer model for inserting Vietnamese accent marks

This model is finetuned from the XLM-Roberta Large.

Example input: Nhin nhung mua thu di  
Target output: Nhìn những mùa thu đi

## Model training
This problem was modelled as a token classification problem. For each input token, the goal is to asssign a "tag" that will transform it
to the accented token.  

For more details on the training process, please refer to this 
<a href="https://peterhung.org/tech/insert-vietnamese-accent-transformer-model/" target="_blank">blog post</a>.


## How to use this model
There are just a few steps: 
- Step 1: Load the model as a token classification model (*AutoModelForTokenClassification*).
- Step 2: Run the input through the model to obtain the tag index for each input token.
- Step 3: Use the tags' index to retreive the actual tags in the file *selected_tags_names.txt*. Then,
  apply the conversion indicated by the tag to each token to obtain accented tokens.

### Step 1: Load model
Note: Install *transformers*, *torch*, *numpy* packages first. 

```python
from transformers import AutoTokenizer, AutoModelForTokenClassification
import torch
import numpy as np

def load_trained_transformer_model():
    model_path = "peterhung/transformer-vnaccent-marker"
    tokenizer = AutoTokenizer.from_pretrained(model_path, add_prefix_space=True)
    model = AutoModelForTokenClassification.from_pretrained(model_path)
    return model, tokenizer

model, tokenizer = load_trained_transformer_model() 
```

### Step 2: Run input text through the model 

```python
# only needed if it's run on GPU
device = torch.device("cuda") if torch.cuda.is_available() else torch.device("cpu")
model.to(device)

# set to eval mode
model.eval()

def insert_accents(text, model, tokenizer):
    our_tokens = text.strip().split()

    # the tokenizer may further split our tokens
    inputs = tokenizer(our_tokens,
                        is_split_into_words=True,
                        truncation=True,
                        padding=True,
                        return_tensors="pt"
                        )
    input_ids = inputs['input_ids']
    tokens = tokenizer.convert_ids_to_tokens(input_ids[0])
    tokens = tokens[1:-1]

    with torch.no_grad():
        inputs.to(device)
        outputs = model(**inputs)

    predictions = outputs["logits"].cpu().numpy()
    predictions = np.argmax(predictions, axis=2)

    # exclude output at index 0 and the last index, which correspond to '<s>' and '</s>'
    predictions = predictions[0][1:-1]

    assert len(tokens) == len(predictions)

    return tokens, predictions 


text = "Nhin nhung mua thu di, em nghe sau len trong nang."

tokens, predictions = insert_accents(text, model, tokenizer)
```

### Step3: Obtain the accented words 

3.1 Download the tags set file from this repo. Then load it 
```python
def _load_tags_set(fpath):
    labels = []
    with open(fpath, 'r') as f:
        for line in f:
            line = line.strip()
            if line:
                labels.append(line)

    return labels
    
label_list = _load_tags_set("/content/training_data/vnaccent/corpus-title.train.selected_tags_names.txt")
assert len(label_list) == 528, f"Expect {len(label_list)} tags"
```

3.2 Print out `tokens` and `predictions` obtained above to see what we're having here
```python
print(tokens)
print(list(f"{pred} ({label_list[pred]})" for pred in predictions))
```
Obtained 
```python
['▁Nhi', 'n', '▁nhu', 'ng', '▁mua', '▁thu', '▁di', ',', '▁em', '▁nghe', '▁sau', '▁len', '▁trong', '▁nang', '.']
['217 (i-ì)', '217 (i-ì)', '388 (u-ữ)', '388 (u-ữ)', '407 (ua-ùa)', '378 (u-u)', '120 (di-đi)', '0 (-)', '185 (e-e)', '185 (e-e)', '41 (au-âu)', '188 (e-ê)', '302 (o-o)', '14 (a-ắ)', '0 (-)']
```


## Limitations 
- This model will accept a maximum of 512 tokens, which is a limitation inherited from the base pretrained XLM-Roberta model.