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@jerryzh168 jerryzh168 commented Aug 21, 2025

Stacked PRs:


[test only] testing adding optioanl tensor arg to float8 tensor

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stack-info: PR: #2840, branch: jerryzh168/stack/33
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jerryzh168 added a commit that referenced this pull request Aug 21, 2025
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stack-info: PR: #2840, branch: jerryzh168/stack/33
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from c5eff30 to 1e1b457 Compare August 21, 2025 20:50
@meta-cla meta-cla bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Aug 21, 2025
@jerryzh168 jerryzh168 added the topic: not user facing Use this tag if you don't want this PR to show up in release notes label Aug 21, 2025
@jerryzh168 jerryzh168 changed the base branch from jerryzh168/stack/29 to main August 21, 2025 22:14
jerryzh168 added a commit that referenced this pull request Aug 21, 2025
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stack-info: PR: #2840, branch: jerryzh168/stack/33
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from 1e1b457 to c5db9f0 Compare August 21, 2025 22:14
@jerryzh168 jerryzh168 changed the base branch from main to jerryzh168/stack/29 August 21, 2025 22:14
@jerryzh168 jerryzh168 changed the base branch from jerryzh168/stack/29 to main August 21, 2025 22:22
jerryzh168 added a commit that referenced this pull request Aug 21, 2025
Summary:

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stack-info: PR: #2840, branch: jerryzh168/stack/33
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from c5db9f0 to a3bd28d Compare August 21, 2025 22:22
@jerryzh168 jerryzh168 changed the base branch from main to jerryzh168/stack/29 August 21, 2025 22:22
@jerryzh168 jerryzh168 changed the base branch from jerryzh168/stack/29 to main August 21, 2025 22:27
jerryzh168 added a commit that referenced this pull request Aug 21, 2025
Summary:

Test Plan:

Reviewers:

Subscribers:

Tasks:

Tags:

stack-info: PR: #2840, branch: jerryzh168/stack/33
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from a3bd28d to 5505809 Compare August 21, 2025 22:27
@jerryzh168 jerryzh168 changed the base branch from main to jerryzh168/stack/29 August 21, 2025 22:27
@jerryzh168 jerryzh168 changed the base branch from jerryzh168/stack/29 to main August 21, 2025 22:38
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from 5505809 to 089dc62 Compare August 21, 2025 22:38
jerryzh168 added a commit that referenced this pull request Aug 21, 2025
Summary:

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stack-info: PR: #2840, branch: jerryzh168/stack/33
@jerryzh168 jerryzh168 changed the base branch from main to jerryzh168/stack/29 August 21, 2025 22:39
jerryzh168 added a commit that referenced this pull request Aug 22, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see #2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
@jerryzh168 jerryzh168 force-pushed the jerryzh168/stack/33 branch from 089dc62 to 77e4a69 Compare August 22, 2025 18:15
@jerryzh168 jerryzh168 changed the base branch from jerryzh168/stack/29 to main August 22, 2025 18:15
jerryzh168 added a commit to jerryzh168/ao that referenced this pull request Aug 22, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see pytorch#2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
jerryzh168 added a commit to jerryzh168/ao that referenced this pull request Aug 22, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see pytorch#2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
jerryzh168 added a commit to jerryzh168/ao that referenced this pull request Aug 22, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see pytorch#2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
jerryzh168 added a commit to jerryzh168/ao that referenced this pull request Aug 23, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see pytorch#2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
jerryzh168 added a commit to jerryzh168/ao that referenced this pull request Aug 23, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see pytorch#2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
jerryzh168 added a commit that referenced this pull request Aug 23, 2025
Summary:

After this PR, tensors inheriting from TorchAOBaseTensor will have better support BC, that is if they add some optional tensor data attribute or optional non-tensor attribute, we will still have BC without any additional changes.

More Details: The BC story we are looking at is that, after we land some tensor, e.g. Int4Tensor, Float8Tensor, future changes should only add optional Tensor data attributes and optional non-Tensor attributes to the Tensor (other bigger changes will require a version bump, we need to add that too). The current TorchAOBaseTensor doesn’t support this very well.

also see #2840 for a real test that adds both an optional tensor and optional non-tensor attribute to Float8Tensor, and the BC test in https://github.com/pytorch/ao/blob/main/test/integration/test_load_and_run_checkpoint.py that tests Float8Tensor does not fail.

Docs for current TorchAOBaseTensor: https://github.com/pytorch/ao/blob/e6b38bb0e1477ae6aaca0a3d30de70598be43290/torchao/utils.py#L726-L731

`tensor_data_names` (List[str]): list of names of all requires tensor_data, order should match
the `__init__` list of tensor subclass
`optional_tensor_data_names` (List[str]): it's optional to define this field to have the additional boilerplate functions been implemented for you, but this will be need if there are some optional Tensor attributes, when defined, this will be a list of names of Tensors that can be optional
`tensor_attribute_names` (List[str]): list of names of non-Tensor attributes,
order should match the `__init__` list of tensor subclass, following all the `tensor_data_names` arguments and `optional_tensor_data_names`

Problems: current optional_tensor_data_names is not truly optional, since it is followed by tensor_attribute_names which contains both required and optional attributes. So if we add a tensor data attribute to Tensor, it will break BC.

Here are a few options:
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, act_scale=None, block_size=None, shape=None, _demo_only_optional_attr=None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None
```

```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    optional_tensor_data_names = ["act_scale"]
    required_tensor_attribute_names = ["block_size", "shape"]
    optional_tensor_attribute_names = ["_demo_only_optional_attr"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, act_scale=None, _demo_only_optional_attr = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```
```

class Int4Tensor(TorchAOBaseTensor):
    tensor_data_names = ["qdata", "scale", "zero_point"]
    tensor_attribute_names = ["block_size", "shape", "_demo_only_optional_attr"]
    optional_tensor_data_names = ["act_scale"]

    def __init__(self, qdata, scale, zero_point, block_size, shape, _demo_only_optional_attr = None, act_scale = None):
        ...

   # for BC
   def __setstate__(self, state):
      torch._utils._set_obj_state(self, state)
      if "act_scale" not in self.__dict__:
          self.act_scale = None

```

Test Plan:
python test/integration/test_load_and_run_checkpoint.py

Reviewers:

Subscribers:

Tasks:

Tags:
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