I am trying to implement a DQL model on one game of openAI gym. But it's giving me following error.
TypeError: len is not well defined for symbolic Tensors. (activation_3/Identity:0) Please call
x.shape
rather thanlen(x)
for shape information.
Creating a gym environment:
ENV_NAME = 'CartPole-v0'
env = gym.make(ENV_NAME)
np.random.seed(123)
env.seed(123)
nb_actions = env.action_space.n
My model looks like this:
model = Sequential()
model.add(Flatten(input_shape=(1,) + env.observation_space.shape))
model.add(Dense(16))
model.add(Activation('relu'))
model.add(Dense(nb_actions))
model.add(Activation('linear'))
print(model.summary())
Fitting that model to DQN model from keral-rl as follows:
policy = EpsGreedyQPolicy()
memory = SequentialMemory(limit=50000, window_length=1)
dqn = DQNAgent(model=model, nb_actions=nb_actions, memory=memory, nb_steps_warmup=10, target_model_update=0.001, policy=policy)
dqn.compile(Adam(lr=1e-3), metrics=['mse', 'mae'])
dqn.fit(env, nb_steps=5000, visualize=False, verbose=3)
The error is from this line:
dqn = DQNAgent(model=model, nb_actions=nb_actions, memory=memory, nb_steps_warmup=10, target_model_update=0.001, policy=policy)
I am using keras-rl==0.4.2 and tensorflow==2.1.0. Based on other answers, I also tried tensorflow==2.0.0-beta0 but it doesn't solve the error.
Can someone please explain to me why I am facing this error? and how to solve it?
Thank you.
The reason this breaks is because, tf.Tensor
TF 2.0.0 (and TF 1.15) has the __len__
overloaded and raises an exception. But TF 1.14 for example doesn't have the __len__
attribute.
Therefore, anything TF 1.15+ (inclusive) breaks keras-rl
(specifically here), which gives you the above error. So you got two options,
__len__
overloading in TensorFlow source (not recommended as this can break other things)a temporal solution for me was to change this line
if hasattr(model.output, '__len__') and len(model.output) > 1:
in the agentfile, where the error come from, in my case dqn.py to :
if hasattr(model.output, '__len__') and len([model.output.shape.dims.__len__()]) > 1:
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