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call(self, inputs, training=None, mask=None, **kwargs) -- Of course, you can have both masking and training-specific behavior at the same time. |
Additionally, if you implement the get_config method on your custom Layer or model, the functional models you create will still be serializable and cloneable. |
Here's a quick example of a custom RNN, written from scratch, being used in a functional model: |
units = 32 |
timesteps = 10 |
input_dim = 5 |
batch_size = 16 |
class CustomRNN(layers.Layer): |
def __init__(self): |
super(CustomRNN, self).__init__() |
self.units = units |
self.projection_1 = layers.Dense(units=units, activation="tanh") |
self.projection_2 = layers.Dense(units=units, activation="tanh") |
self.classifier = layers.Dense(1) |
def call(self, inputs): |
outputs = [] |
state = tf.zeros(shape=(inputs.shape[0], self.units)) |
for t in range(inputs.shape[1]): |
x = inputs[:, t, :] |
h = self.projection_1(x) |
y = h + self.projection_2(state) |
state = y |
outputs.append(y) |
features = tf.stack(outputs, axis=1) |
return self.classifier(features) |
# Note that you specify a static batch size for the inputs with the `batch_shape` |
# arg, because the inner computation of `CustomRNN` requires a static batch size |
# (when you create the `state` zeros tensor). |
inputs = keras.Input(batch_shape=(batch_size, timesteps, input_dim)) |
x = layers.Conv1D(32, 3)(inputs) |
outputs = CustomRNN()(x) |
model = keras.Model(inputs, outputs) |
rnn_model = CustomRNN() |
_ = rnn_model(tf.zeros((1, 10, 5)))Working with preprocessing layers |
Authors: Francois Chollet, Mark Omernick |
Date created: 2020/07/25 |
Last modified: 2021/04/23 |
Description: Overview of how to leverage preprocessing layers to create end-to-end models. |
View in Colab • GitHub source |
Keras preprocessing layers |
The Keras preprocessing layers API allows developers to build Keras-native input processing pipelines. These input processing pipelines can be used as independent preprocessing code in non-Keras workflows, combined directly with Keras models, and exported as part of a Keras SavedModel. |
With Keras preprocessing layers, you can build and export models that are truly end-to-end: models that accept raw images or raw structured data as input; models that handle feature normalization or feature value indexing on their own. |
Available preprocessing layers |
Core preprocessing layers |
TextVectorization layer: turns raw strings into an encoded representation that can be read by an Embedding layer or Dense layer. |
Normalization layer: performs feature-wise normalize of input features. |
Structured data preprocessing layers |
These layers are for structured data encoding and feature engineering. |
CategoryEncoding layer: turns integer categorical features into one-hot, multi-hot, or count dense representations. |
Hashing layer: performs categorical feature hashing, also known as the "hashing trick". |
Discretization layer: turns continuous numerical features into integer categorical features. |
StringLookup layer: turns string categorical values an encoded representation that can be read by an Embedding layer or Dense layer. |
IntegerLookup layer: turns integer categorical values into an encoded representation that can be read by an Embedding layer or Dense layer. |
CategoryCrossing layer: combines categorical features into co-occurrence features. E.g. if you have feature values "a" and "b", it can provide with the combination feature "a and b are present at the same time". |
Image preprocessing layers |
These layers are for standardizing the inputs of an image model. |
Resizing layer: resizes a batch of images to a target size. |
Rescaling layer: rescales and offsets the values of a batch of image (e.g. go from inputs in the [0, 255] range to inputs in the [0, 1] range. |
CenterCrop layer: returns a center crop of a batch of images. |
Image data augmentation layers |
These layers apply random augmentation transforms to a batch of images. They are only active during training. |
RandomCrop layer |
RandomFlip layer |
RandomTranslation layer |
RandomRotation layer |
RandomZoom layer |
RandomHeight layer |
RandomWidth layer |
The adapt() method |
Some preprocessing layers have an internal state that must be computed based on a sample of the training data. The list of stateful preprocessing layers is: |
TextVectorization: holds a mapping between string tokens and integer indices |
StringLookup and IntegerLookup: hold a mapping between input values and integer indices. |
Normalization: holds the mean and standard deviation of the features. |
Discretization: holds information about value bucket boundaries. |
Crucially, these layers are non-trainable. Their state is not set during training; it must be set before training, a step called "adaptation". |
You set the state of a preprocessing layer by exposing it to training data, via the adapt() method: |
import numpy as np |
import tensorflow as tf |
from tensorflow.keras.layers.experimental import preprocessing |
data = np.array([[0.1, 0.2, 0.3], [0.8, 0.9, 1.0], [1.5, 1.6, 1.7],]) |
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