tensorflow训练transformer模型
时间: 2023-09-08 07:09:23 浏览: 155
训练Transformer模型需要一定的准备工作,包括准备数据、构建模型、定义损失函数和优化器等。
下面是一个简单的TensorFlow代码示例,用于训练Transformer模型:
```python
import tensorflow as tf
from transformer import Transformer
# 准备数据
# ...
# 定义模型超参数
num_layers = 4
d_model = 128
dff = 512
num_heads = 8
dropout_rate = 0.1
# 构建模型
transformer = Transformer(num_layers, d_model, num_heads, dff,
input_vocab_size, target_vocab_size,
pe_input=input_vocab_size,
pe_target=target_vocab_size,
rate=dropout_rate)
# 定义损失函数和优化器
loss_object = tf.keras.losses.SparseCategoricalCrossentropy(
from_logits=True, reduction='none')
def loss_function(real, pred):
mask = tf.math.logical_not(tf.math.equal(real, 0))
loss_ = loss_object(real, pred)
mask = tf.cast(mask, dtype=loss_.dtype)
loss_ *= mask
return tf.reduce_sum(loss_)/tf.reduce_sum(mask)
train_loss = tf.keras.metrics.Mean(name='train_loss')
optimizer = tf.keras.optimizers.Adam()
# 定义训练函数
@tf.function
def train_step(inp, tar):
tar_inp = tar[:, :-1]
tar_real = tar[:, 1:]
with tf.GradientTape() as tape:
predictions, _ = transformer(inp, tar_inp, True)
loss = loss_function(tar_real, predictions)
gradients = tape.gradient(loss, transformer.trainable_variables)
optimizer.apply_gradients(zip(gradients, transformer.trainable_variables))
train_loss(loss)
# 开始训练
for epoch in range(EPOCHS):
train_loss.reset_states()
for (batch, (inp, tar)) in enumerate(train_dataset):
train_step(inp, tar)
if batch % 100 == 0:
print('Epoch {} Batch {} Loss {:.4f}'.format(
epoch + 1, batch, train_loss.result()))
```
其中,`Transformer`是我们自定义的Transformer模型类,`num_layers`、`d_model`、`dff`、`num_heads`和`dropout_rate`是超参数,需要根据具体情况进行调整。`loss_object`是损失函数,`SparseCategoricalCrossentropy`是一种适用于多分类问题的损失函数。`loss_function`是我们自定义的损失函数,用于计算每个时间步的损失值。`train_step`是训练函数,用于计算每个batch的损失值并更新模型参数。最后,我们可以根据需要设定epoch数,以及每个epoch中batch的大小,并且使用`train_dataset`作为输入数据进行训练。
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