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We see that different filters in the kernel have different locality spans, and this pattern is likely to evolve with more training. |
Final notes |
There's been a recent trend on fusing convolutions with other data-agnostic operations like self-attention. Following works are along this line of research: |
ConViT (d'Ascoli et al.) |
CCT (Hassani et al.) |
CoAtNet (Dai et al.) |
Image classification with a Transformer that leverages external attention. |
Introduction |
This example implements the EANet model for image classification, and demonstrates it on the CIFAR-100 dataset. EANet introduces a novel attention mechanism named external attention, based on two external, small, learnable, and shared memories, which can be implemented easily by simply using two cascaded linear layers ... |
pip install -U tensorflow-addons |
Setup |
import numpy as np |
import tensorflow as tf |
from tensorflow import keras |
from tensorflow.keras import layers |
import tensorflow_addons as tfa |
import matplotlib.pyplot as plt |
Prepare the data |
num_classes = 100 |
input_shape = (32, 32, 3) |
(x_train, y_train), (x_test, y_test) = keras.datasets.cifar100.load_data() |
y_train = keras.utils.to_categorical(y_train, num_classes) |
y_test = keras.utils.to_categorical(y_test, num_classes) |
print(f\"x_train shape: {x_train.shape} - y_train shape: {y_train.shape}\") |
print(f\"x_test shape: {x_test.shape} - y_test shape: {y_test.shape}\") |
x_train shape: (50000, 32, 32, 3) - y_train shape: (50000, 100) |
x_test shape: (10000, 32, 32, 3) - y_test shape: (10000, 100) |
Configure the hyperparameters |
weight_decay = 0.0001 |
learning_rate = 0.001 |
label_smoothing = 0.1 |
validation_split = 0.2 |
batch_size = 128 |
num_epochs = 50 |
patch_size = 2 # Size of the patches to be extracted from the input images. |
num_patches = (input_shape[0] // patch_size) ** 2 # Number of patch |
embedding_dim = 64 # Number of hidden units. |
mlp_dim = 64 |
dim_coefficient = 4 |
num_heads = 4 |
attention_dropout = 0.2 |
projection_dropout = 0.2 |
num_transformer_blocks = 8 # Number of repetitions of the transformer layer |
print(f\"Patch size: {patch_size} X {patch_size} = {patch_size ** 2} \") |
print(f\"Patches per image: {num_patches}\") |
Patch size: 2 X 2 = 4 |
Patches per image: 256 |
Use data augmentation |
data_augmentation = keras.Sequential( |
[ |
layers.Normalization(), |
layers.RandomFlip(\"horizontal\"), |
layers.RandomRotation(factor=0.1), |
layers.RandomContrast(factor=0.1), |
layers.RandomZoom(height_factor=0.2, width_factor=0.2), |
], |
name=\"data_augmentation\", |
) |
# Compute the mean and the variance of the training data for normalization. |
data_augmentation.layers[0].adapt(x_train) |
Implement the patch extraction and encoding layer |
class PatchExtract(layers.Layer): |
def __init__(self, patch_size, **kwargs): |
super(PatchExtract, self).__init__(**kwargs) |
self.patch_size = patch_size |
def call(self, images): |
batch_size = tf.shape(images)[0] |
patches = tf.image.extract_patches( |
images=images, |
sizes=(1, self.patch_size, self.patch_size, 1), |
strides=(1, self.patch_size, self.patch_size, 1), |
rates=(1, 1, 1, 1), |
padding=\"VALID\", |
) |
patch_dim = patches.shape[-1] |
patch_num = patches.shape[1] |
return tf.reshape(patches, (batch_size, patch_num * patch_num, patch_dim)) |
class PatchEmbedding(layers.Layer): |
def __init__(self, num_patch, embed_dim, **kwargs): |
super(PatchEmbedding, self).__init__(**kwargs) |
self.num_patch = num_patch |
self.proj = layers.Dense(embed_dim) |
self.pos_embed = layers.Embedding(input_dim=num_patch, output_dim=embed_dim) |
def call(self, patch): |
pos = tf.range(start=0, limit=self.num_patch, delta=1) |
return self.proj(patch) + self.pos_embed(pos) |
Implement the external attention block |
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