Keras 3 API documentation / KerasNLP / Pretrained Models / Albert / AlbertMaskedLMPreprocessor layer

AlbertMaskedLMPreprocessor layer

[source]

AlbertMaskedLMPreprocessor class

keras_nlp.models.AlbertMaskedLMPreprocessor(
    tokenizer,
    sequence_length=512,
    truncate="round_robin",
    mask_selection_rate=0.15,
    mask_selection_length=96,
    mask_token_rate=0.8,
    random_token_rate=0.1,
    **kwargs
)

ALBERT preprocessing for the masked language modeling task.

This preprocessing layer will prepare inputs for a masked language modeling task. It is primarily intended for use with the keras_nlp.models.AlbertMaskedLM task model. Preprocessing will occur in multiple steps.

  • Tokenize any number of input segments using the tokenizer.
  • Pack the inputs together with the appropriate "<s>", "</s>" and "<pad>" tokens, i.e., adding a single "<s>" at the start of the entire sequence, "</s></s>" between each segment, and a "</s>" at the end of the entire sequence.
  • Randomly select non-special tokens to mask, controlled by mask_selection_rate.
  • Construct a (x, y, sample_weight) tuple suitable for training with a keras_nlp.models.AlbertMaskedLM task model.

Arguments

  • tokenizer: A keras_nlp.models.AlbertTokenizer instance.
  • sequence_length: The length of the packed inputs.
  • mask_selection_rate: The probability an input token will be dynamically masked.
  • mask_selection_length: The maximum number of masked tokens supported by the layer.
  • mask_token_rate: float. mask_token_rate must be between 0 and 1 which indicates how often the mask_token is substituted for tokens selected for masking. Defaults to 0.8.
  • random_token_rate: float. random_token_rate must be between 0 and 1 which indicates how often a random token is substituted for tokens selected for masking. Default is 0.1. Note: mask_token_rate + random_token_rate <= 1, and for (1 - mask_token_rate - random_token_rate), the token will not be changed. Defaults to 0.1.
  • truncate: string. The algorithm to truncate a list of batched segments to fit within sequence_length. The value can be either round_robin or waterfall:
    • "round_robin": Available space is assigned one token at a time in a round-robin fashion to the inputs that still need some, until the limit is reached.
    • "waterfall": The allocation of the budget is done using a "waterfall" algorithm that allocates quota in a left-to-right manner and fills up the buckets until we run out of budget. It supports an arbitrary number of segments.

Examples

Directly calling the layer on data.

preprocessor = keras_nlp.models.AlbertMaskedLMPreprocessor.from_preset(
    "albert_base_en_uncased"
)

# Tokenize and mask a single sentence.
preprocessor("The quick brown fox jumped.")

# Tokenize and mask a batch of single sentences.
preprocessor(["The quick brown fox jumped.", "Call me Ishmael."])

# Tokenize and mask sentence pairs.
# In this case, always convert input to tensors before calling the layer.
first = tf.constant(["The quick brown fox jumped.", "Call me Ishmael."])
second = tf.constant(["The fox tripped.", "Oh look, a whale."])
preprocessor((first, second))

Mapping with tf.data.Dataset.

preprocessor = keras_nlp.models.AlbertMaskedLMPreprocessor.from_preset(
    "albert_base_en_uncased"
)

first = tf.constant(["The quick brown fox jumped.", "Call me Ishmael."])
second = tf.constant(["The fox tripped.", "Oh look, a whale."])

# Map single sentences.
ds = tf.data.Dataset.from_tensor_slices(first)
ds = ds.map(preprocessor, num_parallel_calls=tf.data.AUTOTUNE)

# Map sentence pairs.
ds = tf.data.Dataset.from_tensor_slices((first, second))
# Watch out for tf.data's default unpacking of tuples here!
# Best to invoke the `preprocessor` directly in this case.
ds = ds.map(
    lambda first, second: preprocessor(x=(first, second)),
    num_parallel_calls=tf.data.AUTOTUNE,
)

[source]

from_preset method

AlbertMaskedLMPreprocessor.from_preset(preset, **kwargs)

Instantiate a keras_nlp.models.Preprocessor from a model preset.

A preset is a directory of configs, weights and other file assets used to save and load a pre-trained model. The preset can be passed as one of:

  1. a built-in preset identifier like 'bert_base_en'
  2. a Kaggle Models handle like 'kaggle://user/bert/keras/bert_base_en'
  3. a Hugging Face handle like 'hf://user/bert_base_en'
  4. a path to a local preset directory like './bert_base_en'

For any Preprocessor subclass, you can run cls.presets.keys() to list all built-in presets available on the class.

As there are usually multiple preprocessing classes for a given model, this method should be called on a specific subclass like keras_nlp.models.BertTextClassifierPreprocessor.from_preset().

Arguments

  • preset: string. A built-in preset identifier, a Kaggle Models handle, a Hugging Face handle, or a path to a local directory.

Examples

# Load a preprocessor for Gemma generation.
preprocessor = keras_nlp.models.GemmaCausalLMPreprocessor.from_preset(
    "gemma_2b_en",
)

# Load a preprocessor for Bert classification.
preprocessor = keras_nlp.models.BertTextClassifierPreprocessor.from_preset(
    "bert_base_en",
)
Preset name Parameters Description
albert_base_en_uncased 11.68M 12-layer ALBERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus.
albert_large_en_uncased 17.68M 24-layer ALBERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus.
albert_extra_large_en_uncased 58.72M 24-layer ALBERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus.
albert_extra_extra_large_en_uncased 222.60M 12-layer ALBERT model where all input is lowercased. Trained on English Wikipedia + BooksCorpus.

tokenizer property

keras_nlp.models.AlbertMaskedLMPreprocessor.tokenizer

The tokenizer used to tokenize strings.