Hmm, this part might be hard as we don’t support strided indexing yet (it should be easy to add though). Apart from this, if you want to have a Parameter, that’s computed from another one, you should do that in the forward function of the model, and use our functional interface. Here’s a simple example with Linear:
class MyModule(nn.Module):
    def __init__(self):
        self.large_linear = nn.Linear(100, 100)

    def forward(self):
        x = F.sigmoid(self.large_linear(x))
        W_small = self.large_linear.weight[:10]
        b_small = self.large_linear.bias[:10]
        return F.linear(x, W_small, b_small)