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Tracing through `__init__` is important because it initializes (calls STORE_ATTR) on members. By doing that, we kick in the mutation tracking for these objects. So, things like mutating `_modules` etc is tracked automatically. Pull Request resolved: https://github.com/pytorch/pytorch/pull/126578 Approved by: https://github.com/jansel ghstack dependencies: #128001
59 lines
1.9 KiB
Python
59 lines
1.9 KiB
Python
import threading
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from contextlib import contextmanager
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import torch
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doc = """
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This is used when dynamo traces torch.nn.Parameter, which normally would not trace properly
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with AOTAutograd. We instead create a placeholder torch.nn.Parameter before the graph, which
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becomes a graph arg and has no storage backing it. At the point in the graph where the parameter
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actually should be created we mutate this sacrificial placeholder into it. This allows gradients
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to flow into the parameter as if it were an input to the graph (which is the only thing we are
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allowed to compute gradients on).
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""".strip()
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class TracableCreateParameter(torch.autograd.Function):
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@staticmethod
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def forward(ctx, tensor, placeholder):
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assert not tensor.requires_grad
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return placeholder.set_(tensor)
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@staticmethod
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def backward(ctx, grad):
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return None, grad # grad flows to placeholder
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def tracable_create_parameter(tensor, placeholder):
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with torch.set_grad_enabled(placeholder.requires_grad):
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out = TracableCreateParameter.apply(tensor, placeholder)
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return out
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def new_parameter_placeholder(size, dtype, device, requires_grad):
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"""Create a placeholder to be passed to the above functions"""
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result = torch.nn.Parameter(
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torch.empty(size, dtype=dtype, device=device), requires_grad=requires_grad
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)
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# TODO(jansel): alloc followed by free is inefficient, need a way to allocate an unbacked tensor.
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# Allocating a zero tensor would causes assert failures in autograd.
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result.untyped_storage().resize_(0)
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return result
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_TLS = threading.local()
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@contextmanager
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def do_not_convert_to_tracable_parameter():
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old_flag = getattr(_TLS, "convert_tracable_parameter", True)
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_TLS.convert_tracable_parameter = False
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try:
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yield False
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finally:
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_TLS.convert_tracable_parameter = old_flag
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def can_convert_to_tracable_parameter():
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return getattr(_TLS, "convert_tracable_parameter", True)
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