因果语言模型

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CausalLM class

keras_nlp.models.CausalLM()

Base class for generative language modeling tasks.

CausalLM tasks wrap a keras_nlp.models.Backbone and a keras_nlp.models.Preprocessor to create a model that can be used for generation and generative fine-tuning.

CausalLM tasks provide an additional, high-level generate() function which can be used to auto-regressively sample a model token by token with a string in, string out signature. The compile() method of all CausalLM classes contains an additional sampler argument, which can be used to pass a keras_nlp.samplers.Sampler to control how the predicted distribution will be sampled.

When calling fit(), the tokenized input will be predicted token-by-token with a causal mask applied, which gives both a pre-training and supervised fine-tuning setup for controlling inference-time generation.

All CausalLM tasks include a from_preset() constructor which can be used to load a pre-trained config and weights.

Example

# Load a GPT2 backbone with pre-trained weights.
causal_lm = keras_nlp.models.CausalLM.from_preset(
    "gpt2_base_en",
)
causal_lm.compile(sampler="top_k")
causal_lm.generate("Keras is a", max_length=64)

# Load a Mistral instruction tuned checkpoint at bfloat16 precision.
causal_lm = keras_nlp.models.CausalLM.from_preset(
    "mistral_instruct_7b_en",
    dtype="bfloat16",
)
causal_lm.compile(sampler="greedy")
causal_lm.generate("Keras is a", max_length=64)

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from_preset method

CausalLM.from_preset(preset, load_weights=True, **kwargs)

Instantiate a keras_nlp.models.Task 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 a 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 Task subclass, you can run cls.presets.keys() to list all built-in presets available on the class.

This constructor can be called in one of two ways. Either from a task specific base class like keras_nlp.models.CausalLM.from_preset(), or from a model class like keras_nlp.models.BertClassifier.from_preset(). If calling from the a base class, the subclass of the returning object will be inferred from the config in the preset directory.

Arguments

• preset: string. A built in preset identifier, a Kaggle Models handle, a Hugging Face handle, or a path to a local directory.
• load_weights: bool. If True, the weights will be loaded into the model architecture. If False, the weights will be randomly initialized.

Examples

# Load a Gemma generative task.
causal_lm = keras_nlp.models.CausalLM.from_preset(
    "gemma_2b_en",
)

# Load a Bert classification task.
model = keras_nlp.models.Classifier.from_preset(
    "bert_base_en",
    num_classes=2,
)

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compile method

CausalLM.compile(
    optimizer="auto", loss="auto", weighted_metrics="auto", sampler="top_k", **kwargs
)

Configures the CausalLM task for training and generation.

The CausalLM task extends the default compilation signature of keras.Model.compile with defaults for optimizer, loss, and weighted_metrics. To override these defaults, pass any value to these arguments during compilation.

The CausalLM task adds a new sampler to compile, which can be used to control the sampling strategy used with the generate function.

Note that because training inputs include padded tokens which are excluded from the loss, it is almost always a good idea to compile with weighted_metrics and not metrics.

Arguments

• optimizer: "auto", an optimizer name, or a keras.Optimizer instance. Defaults to "auto", which uses the default optimizer for the given model and task. See keras.Model.compile and keras.optimizers for more info on possible optimizer values.
• loss: "auto", a loss name, or a keras.losses.Loss instance. Defaults to "auto", where a keras.losses.SparseCategoricalCrossentropy loss will be applied for the token classification CausalLM task. See keras.Model.compile and keras.losses for more info on possible loss values.
• weighted_metrics: "auto", or a list of metrics to be evaluated by the model during training and testing. Defaults to "auto", where a keras.metrics.SparseCategoricalAccuracy will be applied to track the accuracy of the model at guessing masked token values. See keras.Model.compile and keras.metrics for more info on possible weighted_metrics values.
• sampler: A sampler name, or a keras_nlp.samplers.Sampler instance. Configures the sampling method used during generate() calls. See keras_nlp.samplers for a full list of built-in sampling strategies.
• **kwargs: See keras.Model.compile for a full list of arguments supported by the compile method.

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generate method

CausalLM.generate(inputs, max_length=None, stop_token_ids="auto")

Generate text given prompt inputs.

This method generates text based on given inputs. The sampling method used for generation can be set via the compile() method.

If inputs are a tf.data.Dataset, outputs will be generated "batch-by-batch" and concatenated. Otherwise, all inputs will be handled as a single batch.

If a preprocessor is attached to the model, inputs will be preprocessed inside the generate() function and should match the structure expected by the preprocessor layer (usually raw strings). If a preprocessor is not attached, inputs should match the structure expected by the backbone. See the example usage above for a demonstration of each.

Arguments

• inputs: python data, tensor data, or a tf.data.Dataset. If a preprocessor is attached to the model, inputs should match the structure expected by the preprocessor layer. If a preprocessor is not attached, inputs should match the structure expected the backbone model.
• max_length: Optional. int. The max length of the generated sequence. Will default to the max configured sequence_length of the preprocessor. If preprocessor is None, inputs should be should be padded to the desired maximum length and this argument will be ignored.
• stop_token_ids: Optional. None, "auto", or tuple of token ids. Defaults to "auto" which uses the preprocessor.tokenizer.end_token_id. Not specifying a processor will produce an error. None stops generation after generating max_length tokens. You may also specify a list of token id's the model should stop on. Note that sequences of tokens will each be interpreted as a stop token, multi-token stop sequences are not supported.

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save_to_preset method

CausalLM.save_to_preset(preset_dir)

Save task to a preset directory.

Arguments

• preset_dir: The path to the local model preset directory.

preprocessor property

keras_nlp.models.CausalLM.preprocessor

A keras_nlp.models.Preprocessor layer used to preprocess input.

backbone property

keras_nlp.models.CausalLM.backbone

A keras_nlp.models.Backbone model with the core architecture.