84 lines
2.5 KiB
Python
84 lines
2.5 KiB
Python
from keras_core.api_export import keras_core_export
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@keras_core_export(
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["keras_core.Initializer", "keras_core.initializers.Initializer"]
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)
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class Initializer:
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"""Initializer base class: all Keras initializers inherit from this class.
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Initializers should implement a `__call__` method with the following
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signature:
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```python
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def __call__(self, shape, dtype=None, **kwargs):
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# returns a tensor of shape `shape` and dtype `dtype`
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# containing values drawn from a distribution of your choice.
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```
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Optionally, you an also implement the method `get_config()` and the class
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method `from_config` in order to support serialization -- just like with
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any Keras object.
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Here's a simple example: a random normal initializer.
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```python
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class ExampleRandomNormal(Initializer):
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def __init__(self, mean, stddev):
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self.mean = mean
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self.stddev = stddev
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def __call__(self, shape, dtype=None, **kwargs):
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return knp.random.normal(
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shape, mean=self.mean, stddev=self.stddev, dtype=dtype
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)
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def get_config(self): # To support serialization
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return {"mean": self.mean, "stddev": self.stddev}
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```
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Note that we don't have to implement `from_config()` in the example above
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since the constructor arguments of the class the keys in the config returned
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by `get_config()` are the same. In this case, the default `from_config()`
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works fine.
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"""
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def __call__(self, shape, dtype=None):
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"""Returns a tensor object initialized as specified by the initializer.
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Args:
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shape: Shape of the tensor.
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dtype: Optional dtype of the tensor.
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"""
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raise NotImplementedError(
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"Initializer subclasses must implement the `__call__()` method."
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)
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def get_config(self):
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"""Returns the initializer's configuration as a JSON-serializable dict.
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Returns:
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A JSON-serializable Python dict.
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"""
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return {}
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@classmethod
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def from_config(cls, config):
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"""Instantiates an initializer from a configuration dictionary.
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Example:
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```python
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initializer = RandomUniform(-1, 1)
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config = initializer.get_config()
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initializer = RandomUniform.from_config(config)
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```
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Args:
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config: A Python dictionary, the output of `get_config()`.
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Returns:
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An `Initializer` instance.
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"""
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return cls(**config)
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