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super(Perceiver, self).__init__()
self.latent_dim = latent_dim
self.data_dim = data_dim
self.patch_size = patch_size
self.projection_dim = projection_dim
self.num_heads = num_heads
self.num_transformer_blocks = num_transformer_blocks
self.ffn_units = ffn_units
self.dropout_rate = dropout_rate
self.num_iterations = num_iterations
self.classifier_units = classifier_units
def build(self, input_shape):
# Create latent array.
self.latent_array = self.add_weight(
shape=(self.latent_dim, self.projection_dim),
initializer=\"random_normal\",
trainable=True,
)
# Create patching module.
self.patcher = Patches(self.patch_size)
# Create patch encoder.
self.patch_encoder = PatchEncoder(self.data_dim, self.projection_dim)
# Create cross-attenion module.
self.cross_attention = create_cross_attention_module(
self.latent_dim,
self.data_dim,
self.projection_dim,
self.ffn_units,
self.dropout_rate,
)
# Create Transformer module.
self.transformer = create_transformer_module(
self.latent_dim,
self.projection_dim,
self.num_heads,
self.num_transformer_blocks,
self.ffn_units,
self.dropout_rate,
)
# Create global average pooling layer.
self.global_average_pooling = layers.GlobalAveragePooling1D()
# Create a classification head.
self.classification_head = create_ffn(
hidden_units=self.classifier_units, dropout_rate=self.dropout_rate
)
super(Perceiver, self).build(input_shape)
def call(self, inputs):
# Augment data.
augmented = data_augmentation(inputs)
# Create patches.
patches = self.patcher(augmented)
# Encode patches.
encoded_patches = self.patch_encoder(patches)
# Prepare cross-attention inputs.
cross_attention_inputs = {
\"latent_array\": tf.expand_dims(self.latent_array, 0),
\"data_array\": encoded_patches,
}
# Apply the cross-attention and the Transformer modules iteratively.
for _ in range(self.num_iterations):
# Apply cross-attention from the latent array to the data array.
latent_array = self.cross_attention(cross_attention_inputs)
# Apply self-attention Transformer to the latent array.
latent_array = self.transformer(latent_array)
# Set the latent array of the next iteration.
cross_attention_inputs[\"latent_array\"] = latent_array
# Apply global average pooling to generate a [batch_size, projection_dim] repesentation tensor.
representation = self.global_average_pooling(latent_array)
# Generate logits.
logits = self.classification_head(representation)
return logits
Compile, train, and evaluate the mode
def run_experiment(model):
# Create LAMB optimizer with weight decay.
optimizer = tfa.optimizers.LAMB(
learning_rate=learning_rate, weight_decay_rate=weight_decay,
)
# Compile the model.
model.compile(
optimizer=optimizer,
loss=keras.losses.SparseCategoricalCrossentropy(from_logits=True),
metrics=[
keras.metrics.SparseCategoricalAccuracy(name=\"acc\"),
keras.metrics.SparseTopKCategoricalAccuracy(5, name=\"top5-acc\"),
],
)