python - 启用急切执行时不支持 tf.gradients。使用 tf.GradientTape 代替

Question

from tensorflow.keras.applications import VGG16
from tensorflow.keras import backend as K

model = VGG16(weights='imagenet',
              include_top=False)

layer_name = 'block3_conv1'
filter_index = 0

layer_output = model.get_layer(layer_name).output
loss = K.mean(layer_output[:, :, :, filter_index])

grads = K.gradients(loss, model.input)[0]

我无法执行 grads = K.gradients(loss, model.input)[0] ，它会产生一个错误: tf.gradients is not supported when eager execution is enabled. Use tf.GradientTape instead

Answer 1

您有两个选项也可以解决此错误:

.gradients 在 TF2 中被删除 - 按照此处的建议将梯度替换为 GradientTape https://github.com/tensorflow/tensorflow/issues/33135

只需使用 tf1 的兼容模式禁用急切执行约束形式 tf2

解决方案 2 的示例运行代码:

from tensorflow.keras.applications import VGG16
from tensorflow.keras import backend as K
import tensorflow as tf
tf.compat.v1.disable_eager_execution()


model = VGG16(weights='imagenet',
              include_top=False)

layer_name = 'block3_conv1'
filter_index = 0

layer_output = model.get_layer(layer_name).output
loss = K.mean(layer_output[:, :, :, filter_index])

grads = K.gradients(loss, model.input)[0]