Tweak dynamo behavior in 2 places when calling nn.Modules,
to route the call to __call__ instead of .forward(), since
__call__ is the codepath that eager users hit and will dispatch
to hooks correctly.
(1) inside NNModuleVariable.call_function, which covers the common case
of calling a module from code dynamo is already tracing
(2) at the OptimizedModule layer, which is the entrypoint
into a top-level nn.Module dynamo is about to compile
This exposes a new bug: NNModuleVariable used to special-case calling
module.forward() (which is a method) as a UserFunctionVariable with an extra
'self' arg. After tracing into module.__call__, there is no longer a special
case for the eventual call into .forward, and it gets wrapped in a
UserDefinedObjectVariable following standard behavior of ._wrap(). UDOV can't be
called, so this broke some tests.
- Fix: add a new special case in _wrap() that treats methods as a UserDefinedMethod
instead of UserDefinedObjectVariable. Now, the forward method can be called.
Also, fix NNModuleVar.call_method routing forward back to __call__
Pull Request resolved: https://github.com/pytorch/pytorch/pull/92125
Approved by: https://github.com/ezyang, https://github.com/jansel, https://github.com/voznesenskym
The old code didn't actually fakeify traceable tensor subclasses at the
time they are added as a GraphArg to the module; now we do, by ignoring
the subclass during fakeification and relying on Dynamo to simulate
the subclass on top. See comments for more details.
BTW, this codepath is super broken, see filed issues linked on the
inside.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90009
Approved by: https://github.com/wconstab, https://github.com/voznesenskym
This is an API change, so please review carefully.
With this PR, torchdynamo returns an `OptimizedModule` class object, a subclass of `torch.nn.Module`, when asked to optimize a `nn.Module` object. Most of the methods are redirected to the original `nn.Module`, which is installed as `_mod` in the `OptimizedModule`.
This is helpful for many cases
```
mod = MockModule()
opt_mod = torch._dynamo.optimize()(mod)
print(opt_mod) # Works
opt_mod = opt_mod.to(device="cuda")
print(opt_mod) # Works
opt_mod(input) # Triggers recompile if necessary, earlier we were shedding the TorchDynamo wrapper
opt_mod.parameters() # Refers to the original module
```
Topics unclear to me
* I have overridden many methods to raise NotImplementedError. A careful review of those will be good.
* hooks
* For the optimized forward, should we call torchdynamo optimization on `__call__` or `forward`
* What else to test
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88629
Approved by: https://github.com/Chillee, https://github.com/jansel, https://github.com/msaroufim
