# Resnet.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import tensorflow as tf
from tensorflow import keras
from tensorflow.keras import layers, Sequential
class BasicBlock(layers.Layer):
    def __init__(self, filter_num, stride=1):
        super(BasicBlock, self).__init__()
        self.conv1 = layers.Conv2D(filter_num, (3, 3), strides=stride, padding='same')
        self.bn1 = layers.BatchNormalization()
        self.relu = layers.Activation('relu')
        self.conv2 = layers.Conv2D(filter_num, (3, 3), strides=1, padding='same')
        self.bn2 = layers.BatchNormalization()
        if stride != 1:
            self.downsample = Sequential()
            self.downsample.add(layers.Conv2D(filter_num, (1, 1), strides=stride))
        else:
            self.downsample = lambda x: x
    def call(self, inputs, training=None):
        # [b,h,w,c]
        out = self.conv1(inputs)
        out = self.bn1(out)
        out = self.relu(out)
        out = self.conv2(out)
        out = self.bn2(out)
        identity = self.downsample(inputs)
        output = layers.add([out, identity])
        output = tf.nn.relu(output)
        return out

Res Block

ResNet18

# Resnet.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import tensorflow as tf
from tensorflow import keras
from tensorflow.keras import layers, Sequential
class BasicBlock(layers.Layer):
    def __init__(self, filter_num, stride=1):
        super(BasicBlock, self).__init__()
        self.conv1 = layers.Conv2D(filter_num, (3, 3), strides=stride, padding='same')
        self.bn1 = layers.BatchNormalization()
        self.relu = layers.Activation('relu')
        self.conv2 = layers.Conv2D(filter_num, (3, 3), strides=1, padding='same')
        self.bn2 = layers.BatchNormalization()
        if stride != 1:
            self.downsample = Sequential()
            self.downsample.add(layers.Conv2D(filter_num, (1, 1), strides=stride))
        else:
            self.downsample = lambda x: x
    def call(self, inputs, training=None):
        # [b,h,w,c]
        out = self.conv1(inputs)
        out = self.bn1(out)
        out = self.relu(out)
        out = self.conv2(out)
        out = self.bn2(out)
        identity = self.downsample(inputs)
        output = layers.add([out, identity])
        output = tf.nn.relu(output)
        return out
class ResNet(keras.Model):
    def __init__(self, layer_dims, num_classes=100):  # [2,2,2,2]
        super(ResNet, self).__init__()
        # 根部
        self.stem = Sequential([layers.Conv2D(64, (3, 3), strides=(1, 1,)),
                                layers.BatchNormalization(),
                                layers.Activation('relu'),
                                layers.MaxPool2D(pool_size=(2, 2), strides=(1, 1), padding='same')
                                ])
        # 64,128,256,512是通道数
        self.layer1 = self.build_resblock(64, layer_dims[0])
        self.layer2 = self.build_resblock(128, layer_dims[1], stride=2)
        self.layer3 = self.build_resblock(256, layer_dims[2], stride=2)
        self.layer4 = self.build_resblock(512, layer_dims[3], stride=2)
        # output: [b, 512, h, w]
        self.avgpool = layers.GlobalAveragePooling2D()
        self.fc = layers.Dense(num_classes)  # 分类
    def call(self, inputs, training=None):
        x = self.stem(inputs)
        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)
        x = self.layer4(x)
        # [b, c]
        x = self.avgpool(x)
        # [b]
        x = self.fc(x)
        return x
    def build_resblock(self, filter_num, blocks, stride=1):
        res_blocks = Sequential()
        # may down sample
        res_blocks.add(BasicBlock(filter_num, stride))
        for _ in range(1, blocks):
            res_blocks.add(BasicBlock(filter_num, stride=1))
        return res_blocks
def resnet18():
    return ResNet([2, 2, 2, 2])
def resnet34():
    return ResNet([3, 4, 6, 3])

# resnet18_train.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import tensorflow as tf
from tensorflow.keras import layers, optimizers, datasets, Sequential
import os
from Resnet import resnet18
os.environ['TF_CPP_MIN_LOG_LEVEL'] = '2'
tf.random.set_seed(2345)
def preprocess(x, y):
    # [-1~1]
    x = tf.cast(x, dtype=tf.float32) / 255. - 0.5
    y = tf.cast(y, dtype=tf.int32)
    return x, y
(x, y), (x_test, y_test) = datasets.cifar100.load_data()
y = tf.squeeze(y, axis=1)
y_test = tf.squeeze(y_test, axis=1)
print(x.shape, y.shape, x_test.shape, y_test.shape)
train_db = tf.data.Dataset.from_tensor_slices((x, y))
train_db = train_db.shuffle(1000).map(preprocess).batch(512)
test_db = tf.data.Dataset.from_tensor_slices((x_test, y_test))
test_db = test_db.map(preprocess).batch(512)
sample = next(iter(train_db))
print('sample:', sample[0].shape, sample[1].shape,
      tf.reduce_min(sample[0]), tf.reduce_max(sample[0]))
def main():
    # [b, 32, 32, 3] => [b, 1, 1, 512]
    model = resnet18()
    model.build(input_shape=(None, 32, 32, 3))
    model.summary()
    optimizer = optimizers.Adam(lr=1e-3)
    for epoch in range(500):
        for step, (x, y) in enumerate(train_db):
            with tf.GradientTape() as tape:
                # [b, 32, 32, 3] => [b, 100]
                logits = model(x)
                # [b] => [b, 100]
                y_onehot = tf.one_hot(y, depth=100)
                # compute loss
                loss = tf.losses.categorical_crossentropy(y_onehot, logits, from_logits=True)
                loss = tf.reduce_mean(loss)
            grads = tape.gradient(loss, model.trainable_variables)
            optimizer.apply_gradients(zip(grads, model.trainable_variables))
            if step % 50 == 0:
                print(epoch, step, 'loss:', float(loss))
        total_num = 0
        total_correct = 0
        for x, y in test_db:
            logits = model(x)
            prob = tf.nn.softmax(logits, axis=1)
            pred = tf.argmax(prob, axis=1)
            pred = tf.cast(pred, dtype=tf.int32)
            correct = tf.cast(tf.equal(pred, y), dtype=tf.int32)
            correct = tf.reduce_sum(correct)
            total_num += x.shape[0]
            total_correct += int(correct)
        acc = total_correct / total_num
        print(epoch, 'acc:', acc)
if __name__ == '__main__':
    main()

(50000, 32, 32, 3) (50000,) (10000, 32, 32, 3) (10000,)
sample: (512, 32, 32, 3) (512,) tf.Tensor(-0.5, shape=(), dtype=float32) tf.Tensor(0.5, shape=(), dtype=float32)
Model: "res_net"
_________________________________________________________________
Layer (type)                 Output Shape              Param #   
=================================================================
sequential (Sequential)      multiple                  2048      
_________________________________________________________________
sequential_1 (Sequential)    multiple                  148736    
_________________________________________________________________
sequential_2 (Sequential)    multiple                  526976    
_________________________________________________________________
sequential_4 (Sequential)    multiple                  2102528   
_________________________________________________________________
sequential_6 (Sequential)    multiple                  8399360   
_________________________________________________________________
global_average_pooling2d (Gl multiple                  0         
_________________________________________________________________
dense (Dense)                multiple                  51300     
=================================================================
Total params: 11,230,948
Trainable params: 11,223,140
Non-trainable params: 7,808
_________________________________________________________________
WARNING: Logging before flag parsing goes to stderr.
W0601 16:59:57.619546 4664264128 optimizer_v2.py:928] Gradients does not exist for variables ['sequential_2/basic_block_2/sequential_3/conv2d_7/kernel:0', 'sequential_2/basic_block_2/sequential_3/conv2d_7/bias:0', 'sequential_4/basic_block_4/sequential_5/conv2d_12/kernel:0', 'sequential_4/basic_block_4/sequential_5/conv2d_12/bias:0', 'sequential_6/basic_block_6/sequential_7/conv2d_17/kernel:0', 'sequential_6/basic_block_6/sequential_7/conv2d_17/bias:0'] when minimizing the loss.
0 0 loss: 4.60512638092041

Out of memory

• 1. decrease batch size
• 1. tune resnet[2,2,2,2]
• 1. try Google CoLab
• 1. buy new NVIDIA GPU Card