Problems with reshape in GAN's discriminator (Tensorflow) - tensorflow

Question

I was trying to implement various GANs in Tensorflow (after doing it successfully in PyTorch), and I am having some problems while coding the discriminator part.
The code of the discriminator (very similar to the MNIST CNN tutorial) is:
def discriminator(x):
"""Compute discriminator score for a batch of input images.
Inputs:
- x: TensorFlow Tensor of flattened input images, shape [batch_size, 784]
Returns:
TensorFlow Tensor with shape [batch_size, 1], containing the score
for an image being real for each input image.
"""
with tf.variable_scope("discriminator"):
x = tf.reshape(x, [tf.shape(x)[0], 28, 28, 1])
h_1 = leaky_relu(tf.layers.conv2d(x, 32, 5))
m_1 = tf.layers.max_pooling2d(h_1, 2, 2)
h_2 = leaky_relu(tf.layers.conv2d(m_1, 64, 5))
m_2 = tf.layers.max_pooling2d(h_2, 2, 2)
m_2 = tf.contrib.layers.flatten(m_2)
h_3 = leaky_relu(tf.layers.dense(m_2, 4*4*64))
logits = tf.layers.dense(h_3, 1)
return logits
while the code for the generator (architecture of InfoGAN paper) is:
def generator(z):
"""Generate images from a random noise vector.
Inputs:
- z: TensorFlow Tensor of random noise with shape [batch_size, noise_dim]
Returns:
TensorFlow Tensor of generated images, with shape [batch_size, 784].
"""
with tf.variable_scope("generator"):
batch_size = tf.shape(z)[0]
fc = tf.nn.relu(tf.layers.dense(z, 1024))
bn_1 = tf.layers.batch_normalization(fc)
fc_2 = tf.nn.relu(tf.layers.dense(bn_1, 7*7*128))
bn_2 = tf.layers.batch_normalization(fc_2)
bn_2 = tf.reshape(bn_2, [batch_size, 7, 7, 128])
c_1 = tf.nn.relu(tf.contrib.layers.convolution2d_transpose(bn_2, 64, 4, 2, padding='valid'))
bn_3 = tf.layers.batch_normalization(c_1)
c_2 = tf.tanh(tf.contrib.layers.convolution2d_transpose(bn_3, 1, 4, 2, padding='valid'))
So far, so good. The number of parameters is correct (checked it). However, I am having some problems in the next block of code:
tf.reset_default_graph()
# number of images for each batch
batch_size = 128
# our noise dimension
noise_dim = 96
# placeholder for images from the training dataset
x = tf.placeholder(tf.float32, [None, 784])
# random noise fed into our generator
z = sample_noise(batch_size, noise_dim)
# generated images
G_sample = generator(z)
with tf.variable_scope("") as scope:
#scale images to be -1 to 1
logits_real = discriminator(preprocess_img(x))
# Re-use discriminator weights on new inputs
scope.reuse_variables()
logits_fake = discriminator(G_sample)
# Get the list of variables for the discriminator and generator
D_vars = tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES, 'discriminator')
G_vars = tf.get_collection(tf.GraphKeys.TRAINABLE_VARIABLES, 'generator')
# get our solver
D_solver, G_solver = get_solvers()
# get our loss
D_loss, G_loss = gan_loss(logits_real, logits_fake)
# setup training steps
D_train_step = D_solver.minimize(D_loss, var_list=D_vars)
G_train_step = G_solver.minimize(G_loss, var_list=G_vars)
D_extra_step = tf.get_collection(tf.GraphKeys.UPDATE_OPS, 'discriminator')
G_extra_step = tf.get_collection(tf.GraphKeys.UPDATE_OPS, 'generator')
The problem I am getting is where I am doing the reshape in the discriminator, and the error says:
ValueError: None values not supported.
Sure, the value for the batch_size is None (btw, the same error I am getting even where I am changing it to some number), but shape function (as far as I understand) should get the dynamic shape, not the static one. I think that I am a bit lost here.
For what is worth, I am giving here the link to the entire notebook I am working: https://github.com/TheRevanchist/GANs/blob/master/GANs-TensorFlow.ipynb if someone wants to look at it.
NB: The code here is part of the Stanford CS231n assignment. I have no affiliation with Stanford though, so it isn't homework cheating (proof: the course is finished months ago).

Answer 1

The generator seems to be the problem. The output size should match the discriminator. And the other issues are batch norm should be applied before the activation unit. I have modified the code:
with tf.variable_scope("generator"):
fc = tf.layers.dense(z, 4*4*128)
bn_1 = leaky_relu(tf.layers.batch_normalization(fc))
bn_1 = tf.reshape(bn_1, [-1, 4, 4, 128])
c_1 = tf.layers.conv2d_transpose(bn_1, 64, 5, strides=2, padding='same')
bn_2 = leaky_relu(tf.layers.batch_normalization(c_1))
c_2 = tf.layers.conv2d_transpose(bn_2, 32, 5, strides=2, padding='same')
bn_3 = leaky_relu(tf.layers.batch_normalization(c_2))
c_3 = tf.layers.conv2d_transpose(bn_3, 1, 5, strides=2, padding='same')
c_3 = tf.layers.batch_normalization(c_3)
c_3 = tf.image.resize_images(c_3, (28, 28))
c_3 = tf.contrib.layers.flatten(c_3)
c_3 = tf.tanh(c_3)
return c_3
Your code gives the below output when run with the above changes

Answer 2

Instead of passing None to reshape you must pass -1.
So this:
x = tf.reshape(x, [tf.shape(x)[0], 28, 28, 1])
becomes
x = tf.reshape(x, [-1, 28, 28, 1])
and this:
bn_2 = tf.reshape(bn_2, [batch_size, 7, 7, 128])
becomes:
bn_2 = tf.reshape(bn_2, [-1, 7, 7, 128])
It will infer the batch size from the rest of the shape you provided.