我想在构建于keras的自动编码器中定义perceptual_loss。我的自动编码器看起来像这样：

编码器：

input_encoder = Input((32,32,3),name = 'encoder_input')
encoder = Conv2D(16,(3,3),activation = 'relu',name = 'encoder_layer1')(input_encoder)
encoder = Flatten(name = 'encoder_layer2')(encoder)
latent_encoding = Dense(128 , activation = 'relu', name = 'encoder_layer3')(encoder)

Encoder = Model(inputs= [input_encoder], outputs=[latent_encoding],name = 'Encoder')

解码器：

input_decoder = Input(128,name = 'decoder_input')
decoder = Reshape((1, 1, 128),name = 'decoder_layer1')(input_decoder)
decoder = Conv2DTranspose(64, (2,2), activation='relu' , name = 'decoder_layer2')(decoder)
decoder = UpSampling2D(8 ,name = 'decoder_layer3')(decoder)
decoder = Conv2DTranspose(3, (9,9), activation='relu' , name = 'decoder_layer2')(decoder)

Decoder = Model(inputs= [input_decoder], outputs=[decoder ],name = 'Decoder')

自动编码器：

input = Input((32,32,3),name = 'input')
latent = Encoder(input)
output = Decoder(latent)
AE = Model(inputs= [input], outputs=[output ],name = 'AE')

现在我用预训练vgg19定义新的损失函数perceptual_loss像这样，我获取输入图像并重建图像以对vgg19进行预训练并从vgg19的某层获取结果，然后我将两个向量的相减作为vgg19中该层的误差，然后我使用图层误差的加权总和来计算总误差：

selected_layers = ['block1_conv1', 'block2_conv2',"block3_conv3" ,'block4_conv3','block5_conv4']
selected_layer_weights = [1.0, 4.0 , 4.0 , 8.0 , 16.0]

def perceptual_loss(input_image , reconstruct_image):
    vgg = VGG19(weights='imagenet', include_top=False, input_shape=(32,32,3))
    vgg.trainable = False

    outputs = [vgg.get_layer(l).output for l in selected_layers]
    model = Model(vgg.input, outputs)

    h1_list = model(input_image)
    h2_list = model(reconstruct_image)

    rc_loss = 0.0

    for h1, h2, weight in zip(h1_list, h2_list, selected_layer_weights):
        h1 = K.batch_flatten(h1)
        h2 = K.batch_flatten(h2)
        rc_loss = rc_loss + weight * K.sum(K.square(h1 - h2), axis=-1)

    return rc_loss

然后我编译AE：

rmsprop = RMSprop(learning_rate=0.00025)
AE.compile(loss= perceptual_loss, optimizer= rmsprop)

但是当我想适合AE时：

history = AE.fit(train_images, train_images,
                          epochs= 2,
                          verbose=1)

我得到错误

ValueError：tf.function-decorated函数试图在非首次调用时创建变量。

请帮我 。谢谢

更新：

我通过@Mr的答案来更新损失函数。例如，但是我得到新的错误：现在我有损失函数：

'''
define perceptual_loss
'''

selected_layers = ['block1_conv1', 'block2_conv2',"block3_conv3" ,'block4_conv3','block5_conv4']
selected_layer_weights = [1.0, 4.0 , 4.0 , 8.0 , 16.0]

vgg = VGG19(weights='imagenet', include_top=False, input_shape=(32,32,3))
vgg.trainable = False
outputs = [vgg.get_layer(l).output for l in selected_layers]
model = Model(vgg.input, outputs)

def perceptual_loss(input_image , reconstruct_image):
    h1_list = model(input_image)
    h2_list = model(reconstruct_image)

    rc_loss = 0.0
    for h1, h2, weight in zip(h1_list, h2_list, selected_layer_weights):
        h1 = K.batch_flatten(h1)
        h2 = K.batch_flatten(h2)
        rc_loss = rc_loss + weight * K.sum(K.square(h1 - h2), axis=-1)

    return rc_loss

我收到新错误：

ValueError                                Traceback (most recent call last)

<ipython-input-16-3133696ab8be> in <module>()
----> 1 VAE.fit(train_images[:5],train_images[:5],epochs=2,verbose=1)

2 frames

/usr/local/lib/python3.6/dist-packages/tensorflow/python/keras/engine/training.py in fit(self, x, y, batch_size, epochs, verbose, callbacks, validation_split, validation_data, shuffle, class_weight, sample_weight, initial_epoch, steps_per_epoch, validation_steps, validation_batch_size, validation_freq, max_queue_size, workers, use_multiprocessing)
   1098                 _r=1):
   1099               callbacks.on_train_batch_begin(step)
-> 1100               tmp_logs = self.train_function(iterator)
   1101               if data_handler.should_sync:
   1102                 context.async_wait()

/usr/local/lib/python3.6/dist-packages/tensorflow/python/eager/def_function.py in __call__(self, *args, **kwds)
    826     tracing_count = self.experimental_get_tracing_count()
    827     with trace.Trace(self._name) as tm:
--> 828       result = self._call(*args, **kwds)
    829       compiler = "xla" if self._experimental_compile else "nonXla"
    830       new_tracing_count = self.experimental_get_tracing_count()

/usr/local/lib/python3.6/dist-packages/tensorflow/python/eager/def_function.py in _call(self, *args, **kwds)
    862       results = self._stateful_fn(*args, **kwds)
    863       if self._created_variables:
--> 864         raise ValueError("Creating variables on a non-first call to a function"
    865                          " decorated with tf.function.")
    866       return results

ValueError: Creating variables on a non-first call to a function decorated with tf.function.

更新2

正如@Navid所说的，我@tf.function在损失函数之前添加，错误消失了！

'''
define perceptual_loss
'''

selected_layers = ['block1_conv1', 'block2_conv2',"block3_conv3" ,'block4_conv3','block5_conv4']
selected_layer_weights = [1.0, 4.0 , 4.0 , 8.0 , 16.0]

vgg = VGG19(weights='imagenet', include_top=False, input_shape=(32,32,3))
vgg.trainable = False
outputs = [vgg.get_layer(l).output for l in selected_layers]
model = Model(vgg.input, outputs)

@tf.function
def perceptual_loss(input_image , reconstruct_image):
    h1_list = model(input_image)
    h2_list = model(reconstruct_image)

    rc_loss = 0.0
    for h1, h2, weight in zip(h1_list, h2_list, selected_layer_weights):
        h1 = K.batch_flatten(h1)
        h2 = K.batch_flatten(h2)
        rc_loss = rc_loss + weight * K.sum(K.square(h1 - h2), axis=-1)

    return rc_loss ```