NotImplementedError: Cannot convert a symbolic Tensor (2nd_target:0) to a numpy array
For me, the issue occurred when upgrading from numpy 1.19 to 1.20 and using ray's RLlib, which uses tensorflow 2.2 internally.Simply downgrading with
pip install numpy==1.19.5solved the problem; the error did not occur anymore.
I found the solution to this problem:
It was because I mixed symbolic tensor with a non-symbolic type, such as a numpy. For example. It is NOT recommended to have something like this:
def my_mse_loss_b(b): def mseb(y_true, y_pred): ... a = np.ones_like(y_true) #numpy array here is not recommended return K.mean(K.square(y_pred - y_true)) + a return msebInstead, you should convert all to symbolic tensors like this:
def my_mse_loss_b(b): def mseb(y_true, y_pred): ... a = K.ones_like(y_true) #use Keras instead so they are all symbolic return K.mean(K.square(y_pred - y_true)) + a return msebHope this help!
It might be the issue with numpy version. Try to use numpy less than 1.20
pip install numpy==1.19