I am using an implementation of the VAE-GAN 2 from the original paper of ABL Larsen et al. in PyTorch.
I have not the used dataset on hand but trying to use the same implementation with my data, returns me the error:
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-10-b7345b0afa68> in <module>()
     42         datav = Variable(data).cuda()
     43         datav = datav.float()
---> 44         mean, logvar, rec_enc = G(datav)
     45         #print ("The size of rec_enc:", rec_enc.size())
     46 

8 frames
/usr/local/lib/python3.6/dist-packages/torch/nn/functional.py in linear(input, weight, bias)
   1368     if input.dim() == 2 and bias is not None:
   1369         # fused op is marginally faster
-> 1370         ret = torch.addmm(bias, input, weight.t())
   1371     else:
   1372         output = input.matmul(weight.t())

RuntimeError: size mismatch, m1: [4 x 262144], m2: [16384 x 2048] at /pytorch/aten/src/THC/generic/THCTensorMathBlas.cu:290

I am not really sure which size is mismatching though and I couldn’t find something relevant in the documentation. The only thing I 've changed is the channel=1 as it is grayscale images and
#data, _ = next(iter(train_loader))
data = np.squeeze(next(iter(train_loader)))

instead. Still I can’t find the original type and shape of the original dataset so it’s like looking in the dark. Thanks 
For your reference here is my dataloader:
class NiftyDataset(Dataset):
  '''
    Class that loads nii files, resizes them to 96x96 and feeds them
  '''
  def __init__(self, root_dir, transform):
    '''
      root_dir - string - path towards the folder containg the data
    '''
    # Save the root_dir as a class variable
    self.root_dir = root_dir
    # Save the filenames in the root_dir as a class variable
    self.filenames = listdir(self.root_dir)
    self.transform = transform

  def __len__(self):
    return len(self.filenames)
  
  def __getitem__(self,idx):
    # Fetch file filename
    img_name = self.filenames[idx]
    # Load the nifty image
    img = nib.load(os.path.join(self.root_dir,img_name))
    # Get the voxel values as a numpy array
    img = np.array(img.get_fdata())
    print(f"Inside __getitem__ {img.shape} is the image shape")
    # Expanding the array with 1 new dimension as feature channel
    img = np.expand_dims(img, 0)
    print(f"Inside __getitem__ {img.shape} with extra channel")
    return img


batch_size = 4
num_workers = 4
image_size = 64

T = transforms.Compose([transforms.Resize(image_size),
                        transforms.ToTensor(),
                        transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5)),])

# Loading the data
dataset = NiftyDataset(
    root_dir=join("/content/ImagesHands/"), transform = T
)

# Create the required DataLoaders for training and testing
dataset_loader = DataLoader(
    dataset,
    shuffle=True,
    batch_size=batch_size,
    num_workers=num_workers,
    drop_last=True
)

# Show a random image from training
plt.imshow(np.squeeze(next(iter(dataset))), cmap="gray")
plt.axis('off')
plt.show()

Which gives me:
Inside __getitem__ (256, 256) is the image shape
Inside __getitem__ (1, 256, 256) with extra channel