tf.keras.DTypePolicy

A dtype policy for a Keras layer.

tf.keras.DTypePolicy(
    name
)

Used in the notebooks

Used in the guide

A dtype policy determines a layer's computation and variable dtypes. Each layer has a policy. Policies can be passed to the dtype argument of layer constructors, or a global policy can be set with keras.config.set_dtype_policy.

name The policy name, which determines the compute and variable dtypes. Can be any dtype name, such as "float32" or "float64", which causes both the compute and variable dtypes will be that dtype. Can also be the string "mixed_float16" or "mixed_bfloat16", which causes the compute dtype to be float16 or bfloat16 and the variable dtype to be float32.

Typically you only need to interact with dtype policies when using mixed precision, which is the use of float16 or bfloat16 for computations and float32 for variables. This is why the term mixed_precision appears in the API name. Mixed precision can be enabled by passing "mixed_float16" or "mixed_bfloat16" to keras.mixed_precision.set_dtype_policy().

keras.config.set_dtype_policy("mixed_float16")
layer1 = keras.layers.Dense(10)
layer1.dtype_policy  # layer1 will automatically use mixed precision
<DTypePolicy "mixed_float16">
# Can optionally override layer to use float32
# instead of mixed precision.
layer2 = keras.layers.Dense(10, dtype="float32")
layer2.dtype_policy
<DTypePolicy "float32">
# Set policy back to initial float32.
keras.config.set_dtype_policy('float32')

In the example above, passing dtype="float32" to the layer is equivalent to passing dtype=keras.config.DTypePolicy("float32"). In general, passing a dtype policy name to a layer is equivalent to passing the corresponding policy, so it is never necessary to explicitly construct a DTypePolicy object.

compute_dtype The compute dtype of this policy.

This is the dtype layers will do their computations in. Typically layers output tensors with the compute dtype as well.

Note that even if the compute dtype is float16 or bfloat16, hardware devices may not do individual adds, multiplies, and other fundamental operations in float16 or bfloat16, but instead may do some of them in float32 for numeric stability. The compute dtype is the dtype of the inputs and outputs of the ops that the layer executes. Internally, many ops will do certain internal calculations in float32 or some other device-internal intermediate format with higher precision than float16/bfloat16, to increase numeric stability.

name Returns the name of this policy.
variable_dtype The variable dtype of this policy.

This is the dtype layers will create their variables in, unless a layer explicitly chooses a different dtype. If this is different than DTypePolicy.compute_dtype, Layers will cast variables to the compute dtype to avoid type errors.

Variable regularizers are run in the variable dtype, not the compute dtype.

Methods

convert_input

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convert_input(
    x, autocast, dtype
)

from_config

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@classmethod
from_config(
    config
)

get_config

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get_config()