Attribute serialization (#17423)
Summary:
Allows serialization/loading of attributes (`IValue`s of any type).
* metadata (attribute name, type) is stored in the `model.json`
* The binary format is a subset of the `pickle` module that supports the operations necessary for `IValue`s
* Attributes are serialized in the order they are defined on a module to a list in a single `attributes` file, with submodule attributes coming first. This order directly matches the order attributes are listed in `model.json`
* This can be inspected in Python with `pickle.load()` or with `pickletools` (PyTorch need not be installed for this to work)
* A class is used to store a tensor's index into the tensor table of the model, so to unpickle the file you have to use a custom Unpickler:
```python
class TensorID(object):
def __setstate__(self, id):
self.id = id
class JitUnpickler(pickle.Unpickler):
def find_class(self, module, name):
if module == '__main__' and name == 'TensorID':
return TensorID
JitUnpickler(open("my_model/attributes.pkl", "rb")).load()
```
* pickle format: https://svn.python.org/projects/python/trunk/Lib/pickletools.py
* It currently does not support/guarantee that anything saved out with `pickle` (i.e. if you edit `attributes` with `pickle` directly) instead of our tools will be imported correctly
Also will fix #17683 and fix #16367
Followup Work:
* document format / choice of pickle: #17951
* create an example
* list specializations
* int size specializations, large binputs
* do a first pass over attributes to output only necessary `BINPUT` ops
* attribute reassignment (e.g `self.my_attribute = new_value`)
* `tensor.save("some_checkpoint.pkl")` support with tensors embedded in Pickle file
Pull Request resolved: https://github.com/pytorch/pytorch/pull/17423
Differential Revision: D14470965
Pulled By: driazati
fbshipit-source-id: 6a21a9939efdbe59b4bc57fd31d6d630bab5297e