> ## Documentation Index
> Fetch the complete documentation index at: https://rasa.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Nlu-dense

> Nlu-dense reference documentation for the Rasa Platform.

```python theme={null}
import numpy as np
import logging
from bpemb import BPEmb
from typing import Any, Text, Dict, List, Type

from rasa.engine.recipes.default_recipe import DefaultV1Recipe
from rasa.engine.graph import ExecutionContext, GraphComponent
from rasa.engine.storage.resource import Resource
from rasa.engine.storage.storage import ModelStorage
from rasa.nlu.featurizers.dense_featurizer.dense_featurizer import DenseFeaturizer
from rasa.nlu.tokenizers.tokenizer import Tokenizer
from rasa.shared.nlu.training_data.training_data import TrainingData
from rasa.shared.nlu.training_data.features import Features
from rasa.shared.nlu.training_data.message import Message
from rasa.nlu.constants import (
    DENSE_FEATURIZABLE_ATTRIBUTES,
    FEATURIZER_CLASS_ALIAS,
)
from rasa.shared.nlu.constants import (
    TEXT,
    TEXT_TOKENS,
    FEATURE_TYPE_SENTENCE,
    FEATURE_TYPE_SEQUENCE,
)

logger = logging.getLogger(__name__)

@DefaultV1Recipe.register(
    DefaultV1Recipe.ComponentType.MESSAGE_FEATURIZER, is_trainable=False
)
class BytePairFeaturizer(DenseFeaturizer, GraphComponent):
    @classmethod
    def required_components(cls) -> List[Type]:
        """Components that should be included in the pipeline before this component."""
        return [Tokenizer]

    @staticmethod
    def required_packages() -> List[Text]:
        """Any extra python dependencies required for this component to run."""
        return ["bpemb"]

    @staticmethod
    def get_default_config() -> Dict[Text, Any]:
        """Returns the component's default config."""
        return {
            **DenseFeaturizer.get_default_config(),
            # specifies the language of the subword segmentation model
            "lang": None,
            # specifies the dimension of the subword embeddings
            "dim": None,
            # specifies the vocabulary size of the segmentation model
            "vs": None,
            # if set to True and the given vocabulary size can't be loaded for the given
            # model, the closest size is chosen
            "vs_fallback": True,
        }

    def __init__(
        self,
        config: Dict[Text, Any],
        name: Text,
    ) -> None:
        """Constructs a new byte pair vectorizer."""
        super().__init__(name, config)
        # The configuration dictionary is saved in `self._config` for reference.
        self.model = BPEmb(
            lang=self._config["lang"],
            dim=self._config["dim"],
            vs=self._config["vs"],
            vs_fallback=self._config["vs_fallback"],
        )

    @classmethod
    def create(
        cls,
        config: Dict[Text, Any],
        model_storage: ModelStorage,
        resource: Resource,
        execution_context: ExecutionContext,
    ) -> GraphComponent:
        """Creates a new component (see parent class for full docstring)."""
        return cls(config, execution_context.node_name)

    def process(self, messages: List[Message]) -> List[Message]:
        """Processes incoming messages and computes and sets features."""
        for message in messages:
            for attribute in DENSE_FEATURIZABLE_ATTRIBUTES:
                self._set_features(message, attribute)
        return messages

    def process_training_data(self, training_data: TrainingData) -> TrainingData:
        """Processes the training examples in the given training data in-place."""
        self.process(training_data.training_examples)
        return training_data

    def _create_word_vector(self, document: Text) -> np.ndarray:
        """Creates a word vector from a text. Utility method."""
        encoded_ids = self.model.encode_ids(document)
        if encoded_ids:
            return self.model.vectors[encoded_ids[0]]

        return np.zeros((self.component_config["dim"],), dtype=np.float32)

    def _set_features(self, message: Message, attribute: Text = TEXT) -> None:
        """Sets the features on a single message. Utility method."""
        tokens = message.get(TEXT_TOKENS)

        # If the message doesn't have tokens, we can't create features.
        if not tokens:
            return None

        # We need to reshape here such that the shape is equivalent to that of sparsely
        # generated features. Without it, it'd be a 1D tensor. We need 2D (n_utterance, n_dim).
        text_vector = self._create_word_vector(document=message.get(TEXT)).reshape(
            1, -1
        )
        word_vectors = np.array(
            [self._create_word_vector(document=t.text) for t in tokens]
        )

        final_sequence_features = Features(
            word_vectors,
            FEATURE_TYPE_SEQUENCE,
            attribute,
            self._config[FEATURIZER_CLASS_ALIAS],
        )
        message.add_features(final_sequence_features)
        final_sentence_features = Features(
            text_vector,
            FEATURE_TYPE_SENTENCE,
            attribute,
            self._config[FEATURIZER_CLASS_ALIAS],
        )
        message.add_features(final_sentence_features)

    @classmethod
    def validate_config(cls, config: Dict[Text, Any]) -> None:
        """Validates that the component is configured properly."""
        if not config["lang"]:
            raise ValueError("BytePairFeaturizer needs language setting via `lang`.")
        if not config["dim"]:
            raise ValueError(
                "BytePairFeaturizer needs dimensionality setting via `dim`."
            )
        if not config["vs"]:
            raise ValueError("BytePairFeaturizer needs a vector size setting via `vs`.")
```


## Related topics

- [NLU Components](/docs/reference/config/components/nlu-components.md)
- [Rasa Pro Change Log](/docs/reference/changelogs/rasa-pro-changelog.md)
- [Nlu-sparse](/docs/reference/config/components/example-components/custom-graph-components/nlu-sparse.md)
- [NLU Command Adapter](/docs/reference/config/components/nlu-command-adapter.md)
- [Nlu-component-skeleton](/docs/reference/config/components/example-components/nlu-component-skeleton.md)