modify the strides

[xuao575]

In PyTorch, when the stride is 0, RuntimeError: non-positive stride is not supported will be raised. Meanwhile, the default argument stride of nn.Conv2d is 1.

https://pytorch.org/docs/stable/generated/torch.nn.Conv2d.html#:~:text=%2C%20kernel_size%2C-,stride%3D1,-%2C%20padding%3D