Week 4 - Assignment 2 - Neural Art - Exercise 3

Course Q&A Deep Learning Specialization Convolutional Neural Networks
1

Hi guys,

I am running into trouble when computing the function: compute_layer_style_cost(a_S, a_G).
My implementation of the Gram matrix is correct and I simply implement the loss function with the tf functions, however I get an error stating that it the value is wrong. I’ve double checked the size of the a_S and a_G matrices which should be (3,16) based on the test values which is correct. I am not sure where I am going wrong here

tf.Tensor(2.9203947, shape=(), dtype=float32)

AssertionError Traceback (most recent call last)
in
9 assert np.isclose(J_style_layer_GG, 0.0), “Wrong value. compute_layer_style_cost(A, A) must be 0”
10 assert J_style_layer_SG > 0, “Wrong value. compute_layer_style_cost(A, B) must be greater than 0 if A != B”
—> 11 assert np.isclose(J_style_layer_SG, 14.017805), “Wrong value.”
12
13 print("J_style_layer = " + str(J_style_layer_SG))

AssertionError: Wrong value.

Help would be much appreciated!

Thanks

2

Can you please post your code of the function, so that we can see where the issue exactly lies. And you can remove the code once your query is resolved.

4

I guess the error is in these lines of code

a_S = tf.reshape(a_S, shape = [n_C,n_H*n_W])
a_G = tf.reshape(a_G, shape = [n_C,n_H*n_W])

The original shape is (1, n_h, n_w, n_c), so you will have to use tf.transpose as well in order to get the dimensions in the right order.

a_S = tf.transpose(tf.reshape(a_S, shape=(-1, n_C)), perm=[1, 0])
a_G = tf.transpose(tf.reshape(a_G, shape=(-1, n_C)), perm=[1, 0])

Try using these lines of code instead.
P.S. - tf.square worked just fine in my case.

3 Likes
5

This worked, thanks very much!

6

Posting code breaks the course Honor Code. Please don’t ask other students to do that.
Thanks.

7

I used transpose to reorder the last 3 dimensions (with 0 3 1 2) and only then reshape to get the right shape and it did the trick too! :slight_smile:

8

Sorry Sir, I am well aware of it. But it’s a little hard to debug without looking at the code, and I did ask the author to remove the code. I am sure the author will remove the code soon

2 Likes