Negative dimension error while using keras Convolutional1D Layer

Question

I\'m trying to create a char cnn using Keras. That type of cnn requires you to use Convolutional1D layer. But all the ways I try to add them to my model, it giv

Answer 1

Your downsampling is too aggressive and the key argument here is max_len: when it's too small, the sequence becomes too short to perform either a convolution or a max-pooling. You set pool_size=3, hence it shrinks the sequence by a factor of 3 after each pooling (see the example below). I suggest you try pool_size=2.

The minimal max_len that this network can handle is max_len=123. In this case x shape is transformed in the following way (according to conv_layers):

(?, 123, 128)
(?, 39, 256)
(?, 11, 256)
(?, 9, 256)
(?, 7, 256)
(?, 5, 256)

Setting a smaller value, like max_len=120 causes x.shape=(?, 4, 256) before the last layer and this can't be performed.