再進行SimpleRNNCell循環神經網絡學習過程中發現一個奇怪的bug，錯誤日誌如下：
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\execute.py", line 61, in quick_execute
num_outputs)
TypeError: An op outside of the function building code is being passed
a "Graph" tensor. It is possible to have Graph tensors
leak out of the function building context by including a
tf.init_scope in your function building code.
For example, the following function will fail:
@tf.function
def has_init_scope():
my_constant = tf.constant(1.)
with tf.init_scope():
added = my_constant * 2
The graph tensor has name: my_rnn/simple_rnn_cell/cond/Identity:0
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "e:/python_project/tensor_test/tensor_advantage/sentiment_analysis_single_layer.py", line 111,
in <module>
main()
File "e:/python_project/tensor_test/tensor_advantage/sentiment_analysis_single_layer.py", line 106,
in main
model.fit(db_train, epochs=epochs, validation_data=db_test)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\keras\engine\training.py", line 819, in fit
use_multiprocessing=use_multiprocessing)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\keras\engine\training_v2.py", line 342, in fit
total_epochs=epochs)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\keras\engine\training_v2.py", line 128, in run_one_epoch
batch_outs = execution_function(iterator)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\keras\engine\training_v2_utils.py", line 98, in execution_function
distributed_function(input_fn))
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\def_function.py", line 568, in __call__
result = self._call(*args, **kwds)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\def_function.py", line 632, in _call
return self._stateless_fn(*args, **kwds)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\function.py", line 2363, in __call__
return graph_function._filtered_call(args, kwargs) # pylint: disable=protected-access
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\function.py", line 1611, in _filtered_call
self.captured_inputs)
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\function.py", line 1692, in _call_flat
ctx, args, cancellation_manager=cancellation_manager))
File "C:\Users\Jame_Peng\AppData\Local\Programs\Python\Python37\lib\site-packages\tensorflow_core\python\eager\function.py", line 545, in call
ctx=ctx)
thon\eager\execute.py", line 75, in quick_execute
"tensors, but found {}".format(keras_symbolic_tensors))
tensorflow.python.eager.core._SymbolicException: Inputs to eager execution function cannot be Keras symbolic tensors, but found [<tf.Tensor 'my_rnn/simple_rnn_cell/cond/Identity:0' shape=(None, 100) dtype=float32>, <tf.Tensor 'my_rnn/simple_rnn_cell_1/cond/Identity:0' shape=(100, 64) dtype=float32>]
我在stackflow上也看到有人反映這個問題：
https://stackoverflow.com/questions/59403281/unable-to-use-mse-of-vgg-features-in-loss-function
In tensorflow 2.0, eager execution is enabled by default.
tensorflow2.0默認啓用Eager Execution
通過使用下列函數禁用eager_excution：
tf.compat.v1.disable_eager_execution()
我不太理解爲什麼禁用了就可以正常執行，也許是eager_excution有什麼Bug吧
另一種辦法是SimpleRNNCell初始化的時候放棄dropout參數，也可以解決這個問題
原來：
self.rnn_cell0 = layers.SimpleRNNCell(units, dropout=0.5)
self.rnn_cell1 = layers.SimpleRNNCell(units, dropout=0.5)
改爲：
self.rnn_cell0 = layers.SimpleRNNCell(units)
self.rnn_cell1 = layers.SimpleRNNCell(units)