pytorch/torch/nn/cpp.py
Peter Goldsborough 0bf1383f0a Python <-> C++ Frontend inter-op (#13481)
Summary:
This PR enables C++ frontend modules to be bound into Python and added as submodules of Python modules. For this, I added lots of pybind11 bindings for the `torch::nn::Module` class, and modified the `torch.nn.Module` class in Python to have a new Metaclass that makes `isinstance(m, torch.nn.Module)` return true when `m` is a C++ frontend module. The methods and fields of C++ modules are bound in such a way that they work seamlessly as submodules of Python modules for most operations (one exception I know of: calling `.to()` ends up calling `.apply()` on each submodule with a Python lambda, which cannot be used in C++ -- this may require small changes on Python side).

I've added quite a bunch of tests to verify the bindings and equality with Python. I think I should also try out adding a C++ module as part of some large PyTorch module, like a WLM or something, and see if everything works smoothly.

The next step for inter-op across our system is ScriptModule <-> C++ Frontend Module inter-op. I think this will then also allow using C++ frontend modules from TorchScript.

apaszke zdevito

CC dzhulgakov
Pull Request resolved: https://github.com/pytorch/pytorch/pull/13481

Differential Revision: D12981996

Pulled By: goldsborough

fbshipit-source-id: 147370d3596ebb0e94c82cec92993a148fee50a7
2018-12-13 08:04:02 -08:00

78 lines
2.3 KiB
Python

"""Functionality for Python <-> C++ frontend inter-op."""
from torch import nn
class OrderedDictWrapper(object):
"""
A wrapper around a C++ OrderedDict that dynamically evaluates the
OrderedDict getter on a bound C++ module, such that new changes on the C++
side are picked up. Otherwise accessing e.g. ``cpp_module._parameters`` just
once would get a frozen copy of the parameters at the time of access.
``torch.nn.Module`` accesses ``_parameters`` et al. via ``self.__dict__`` so
using properties does not work.
"""
def __init__(self, cpp_module, attr):
self.cpp_module = cpp_module
self.attr = attr
@property
def cpp_dict(self):
return getattr(self.cpp_module, self.attr)
# Magic methods cannot be assigned dynamically and bypass ``getattr``, so we
# must manually override them.
def items(self):
return self.cpp_dict.items()
def keys(self):
return self.cpp_dict.keys()
def values(self):
return self.cpp_dict.values()
def __iter__(self):
return self.cpp_dict.__iter__()
def __len__(self):
return self.cpp_dict.__len__()
def __contains__(self, key):
return self.cpp_dict.__contains__(key)
def __getitem__(self, key):
return self.cpp_dict.__getitem__(key)
class ModuleWrapper(nn.Module):
"""
A subclass of ``torch.nn.Module`` that wraps a C++ frontend module and
delegates all access.
"""
def __init__(self, cpp_module):
# Assign before the super class constructor so ``self.training`` can be
# assigned to in the super class constructor.
self.cpp_module = cpp_module
super(ModuleWrapper, self).__init__()
self._parameters = OrderedDictWrapper(cpp_module, "_parameters")
self._buffers = OrderedDictWrapper(cpp_module, "_buffers")
self._modules = OrderedDictWrapper(cpp_module, "_modules")
for attr in dir(cpp_module):
# Skip magic methods and the three attributes above.
if not attr.startswith("_"):
setattr(self, attr, getattr(self.cpp_module, attr))
@property
def training(self):
return self.cpp_module.training
@training.setter
def training(self, mode):
self.cpp_module.train(mode)
def __repr__(self):
return self.cpp_module.__repr__()