Shallow-copy indices and values in sparse tensor ctor (#20330)
Summary:
After the Variable/Tensor merge, there is no guarantee that `indices` and `values` passed into the sparse tensor constructor don't contain AutogradMeta. However, we want to maintain the existing invariant that `indices_` and `values_` of a sparse tensor don't contain AutogradMeta, and to achieve this we need do shallow-copy in the sparse tensor constructor.
Note that this is BC-breaking for code that changes the sizes / strides of the indices or values tensor after it's used to create a sparse tensor. In current master, such changes will be reflected in the sparse tensor and break sparse tensor invariants. After this PR, those changes will not be reflected in the sparse tensor, and thus the sparse tensor invariants are always preserved. Specifically, running in-place size/stride-changing ops such as `resize_` / `resize_as_` / `as_strided_` / `set_` / `transpose_` on the original values tensor will not update the sparse tensor's `values_`. For example:
```python
# Calling resize_ on non-requires-grad value tensor
i2 = torch.zeros([1, 1])
v2 = torch.ones([1, 2, 3])
t2 = torch.sparse_coo_tensor(i2, v2, torch.Size([2, 2, 3]))
v2.resize_(4, 5)
t2.coalesce().values().size()
# On current master, this throws "indices and values must have same nnz, but got nnz from indices: 1, nnz from values: 4", because resizing the original value tensor affects `values_` of the sparse tensor.
# After this PR, this prints "torch.Size([1, 2, 3])", which means resizing the original value tensor doesn't affect `values_` of the sparse tensor.
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20330
Differential Revision: D15373683
Pulled By: yf225
fbshipit-source-id: 32e7275d7121e17937c7cc258e8a60bb0848ff25
