keras.models 实现transformer回归模型

在Keras中实现Transformer回归模型的步骤如下：

1. 导入所需的库和模块：

import tensorflow as tf
from tensorflow import keras
from tensorflow.keras import layers

2. 定义Transformer的编码器层和解码器层：

class TransformerEncoder(layers.Layer):
    def __init__(self, num_heads, d_model, dff, rate=0.1):
        super(TransformerEncoder, self).__init__()
        self.multihead_attention = layers.MultiHeadAttention(num_heads=num_heads, key_dim=d_model)
        self.ffn = keras.Sequential([layers.Dense(dff, activation="relu"), layers.Dense(d_model)])
        self.layernorm1 = layers.LayerNormalization(epsilon=1e-6)
        self.layernorm2 = layers.LayerNormalization(epsilon=1e-6)
        self.dropout1 = layers.Dropout(rate)
        self.dropout2 = layers.Dropout(rate)

    def call(self, inputs, training=False):
        attention_output = self.multihead_attention(inputs, inputs)
        attention_output = self.dropout1(attention_output, training=training)
        attention_output = self.layernorm1(inputs + attention_output)
        ffn_output = self.ffn(attention_output)
        ffn_output = self.dropout2(ffn_output, training=training)
        return self.layernorm2(attention_output + ffn_output)

class TransformerDecoder(layers.Layer):
    def __init__(self, num_heads, d_model, dff, rate=0.1):
        super(TransformerDecoder, self).__init__()
        self.multihead_attention1 = layers.MultiHeadAttention(num_heads=num_heads, key_dim=d_model)
        self.multihead_attention2 = layers.MultiHeadAttention(num_heads=num_heads, key_dim=d_model)
        self.ffn = keras.Sequential([layers.Dense(dff, activation="relu"), layers.Dense(d_model)])
        self.layernorm1 = layers.LayerNormalization(epsilon=1e-6)
        self.layernorm2 = layers.LayerNormalization(epsilon=1e-6)
        self.layernorm3 = layers.LayerNormalization(epsilon=1e-6)
        self.dropout1 = layers.Dropout(rate)
        self.dropout2 = layers.Dropout(rate)
        self.dropout3 = layers.Dropout(rate)

    def call(self, inputs, encoder_output, training=False):
        attention1 = self.multihead_attention1(inputs, inputs)
        attention1 = self.dropout1(attention1, training=training)
        attention1 = self.layernorm1(inputs + attention1)
        attention2 = self.multihead_attention2(attention1, encoder_output)
        attention2 = self.dropout2(attention2, training=training)
        attention2 = self.layernorm2(attention1 + attention2)
        ffn_output = self.ffn(attention2)
        ffn_output = self.dropout3(ffn_output, training=training)
        return self.layernorm3(attention2 + ffn_output)

3. 定义Transformer模型：

class TransformerModel(tf.keras.Model):
    def __init__(self, num_layers, num_heads, d_model, dff, target_vocab_size, pe_input, pe_target, rate=0.1):
        super(TransformerModel, self).__init__()
        self.d_model = d_model
        self.embedding = layers.Embedding(target_vocab_size, d_model)
        self.pos_encoding = position_encoding(pe_input, self.d_model)
        self.transformer_encoders = [TransformerEncoder(num_heads, d_model, dff, rate) for _ in range(num_layers)]
        self.transformer_decoders = [TransformerDecoder(num_heads, d_model, dff, rate) for _ in range(num_layers)]
        self.dense = layers.Dense(target_vocab_size)

    def call(self, inputs, targets, training=False):
        inputs = self.embedding(inputs)
        inputs *= tf.math.sqrt(tf.cast(self.d_model, tf.float32))
        inputs += self.pos_encoding[:, :tf.shape(inputs)[1], :]
        for encoder in self.transformer_encoders:
            inputs = encoder(inputs, training=training)
        targets = self.embedding(targets)
        targets *= tf.math.sqrt(tf.cast(self.d_model, tf.float32))
        targets += self.pos_encoding[:, :tf.shape(targets)[1], :]
        for decoder in self.transformer_decoders:
            targets = decoder(targets, inputs, training=training)
        outputs = self.dense(targets)
        return outputs

4. 构建和编译模型：

num_layers = 4
num_heads = 8
d_model = 128
dff = 512
target_vocab_size = 10000
dropout_rate = 0.1

model = TransformerModel(num_layers, num_heads, d_model, dff, target_vocab_size, pe_input, pe_target, dropout_rate)
model.compile(optimizer=tf.keras.optimizers.Adam(), loss=tf.keras.losses.MeanSquaredError())

5. 训练模型：

model.fit(train_dataset, validation_data=val_dataset, epochs=num_epochs)

6. 进行预测：

predictions = model.predict(test_dataset)