Not sure if parameters are being updated

anawesumoposum: <p>So my implementation is to make a generator that spits out iteratively bigger and more complex networks. Since my amount of layers are dynamic I store them in a list bound to the class and I noticed that they aren’t automatically included in the .parameters, so I manually added them myself. After a round of testing the network almost immediately converges around 11-19% accuracy, so I have a strong feeling that the optimizer isn’t actually updating the layers. I’m having a hard time finding relevant examples on the google, can I get some advice?</p>
<pre><code class="lang-auto">class NNGenerator(torch.nn.Module):
  def __init__(self, num):
    super(NNGenerator, self).__init__()
    self.num = num
    self.res = 32
    self.power = 0
    self.layers = []

    for i in range(self.num * 2):
      self.layers.append( torch.nn.Conv2d( 3*(2**i), 3*(2**(i+1)), kernel_size=3) )
      self.res -= 2
      if(i % 2):
        self.res /= 2
        self.power = 3*(2**(i+1))
    
    self.pool = torch.nn.MaxPool2d(2, 2)

    self.feat = int( self.power * (self.res * self.res) )
    self.fc1 = torch.nn.Linear( self.feat, 100 )
    self.fc2 = torch.nn.Linear( 100, 10 )

  def forward(self, x): #-1, 3, 32, 32
    for idx, func in enumerate(self.layers):
      x = func(x)
      x = F.relu(x)
      if(idx % 2):
        x = self.pool(x) 
      
    x = F.relu( self.fc1(x.view(-1,self.feat)) )
    x = F.relu( self.fc2(x) )

    return F.softmax(x, -1)

teacher = NNGenerator(1)
#for idx, param in enumerate(teacher.layers):
#  teacher.register_parameter('conv'+str(idx), param)
#print(teacher.parameters)

optimizer = torch.optim.SGD(teacher.parameters(), lr=.001, momentum=0.9)
for param in teacher.layers:
  optimizer.add_param_group({'params': param.parameters()}) #aren't automatically added when they aren't a direct method
loss = torch.nn.CrossEntropyLoss()

def nntrain(epoch):
  teacher.train()

  for index, (images, targets) in enumerate(traingen):
    optimizer.zero_grad()
    output = teacher(images)
    if not (len(output) == len(targets)):
      print(len(output))
      print(len(targets))
    loss_out = loss(output, targets)
    loss_out.backward()
    optimizer.step()

    if not (index % 100):
      print(f'Epoch {epoch}: [{index*len(images)}/{len(trainin)}] Loss: {loss_out.item()}')

def nntest(epoch):
  teacher.eval() 

  test_loss = 0
  correct = 0

  with torch.no_grad():
    for images, targets in testgen:
      output = teacher(images)
      test_loss += loss(output, targets.long()).item()
      pred = output.data.max(1, keepdim=True)[1]
      correct += pred.eq(targets.data.view_as(pred)).sum()

  test_loss /= len(testin)
  print(f'Test result on epoch {epoch}: Avg loss is {test_loss}, Accuracy: {100.*correct/len(testin)}%')

for epoch in range(1, 3):
  nntrain(epoch)
  nntest(epoch)```</code></pre>

ptrblck: <p>You should use <code>nn.ModuleList</code> instead of Python <code>lists</code> to add your modules to <code>NNGenerator</code>.<br>
This would make sure to properly register these layers and return all parameters via <code>model.parameters()</code>.<br>
However, if you are planning to dynamically adding new layers to the model, you would still have to either recreate the optimizer or add the new parameters to it.</p>

anawesumoposum: <p>Hadn’t seen that before, thanks! Although after more testing it appears that this works - although this form only generates very small CNNs that converge quickly and perform poorly. On much larger fc layers it seems to have much better performance. I’ll def use your advice though</p>

anawesumoposum: <p>Nevermind, you’re entirely correct! I was under the impression that everything would be updated since the optimizer has the last layer passed in and I manually pass in each other layer, but upon more testing I realized that only the manually added layers are being updated and the initially passed in layers that are directly bound to the class aren’t! I imagine wrapping all of them in nn.modulelist solves this, so that’s my next attempt. Thank you so much!</p>