Hi everyone! I’m new to pytorch and I’m working on a custom model based on this medium article, but for some reason my weights aren’t updating. When I try to print out the gradients of the weights as they are training I simply end up seeing zero tensors. My model and the training loop is shown below:

```
class Model(nn.Module):
def __init__(self):
super().__init__()
weights = torch.zeros([n_vec, 2])
self.weights = nn.Parameter(weights)
def forward(self):
return torch.cdist(self.weights, self.weights, p=2)
def training_loop(model, optimizer, n=1000):
losses = []
for i in range(n):
preds = model()
loss = torch.sum((preds - x) ** 2)
loss.backward()
optimizer.step()
optimizer.zero_grad()
losses.append(loss)
return losses
m = Model()
opt = torch.optim.Adam(m.parameters(), lr=0.005)
losses = training_loop(m, opt)
```

I can’t figure out why this is, the only thing I can think of is that torch.cdist is somehow messing up the autograd. Any help would be greatly appreciated!