* Convolution derivatives in ATen
This PR introduces ATen implementation of convolution, which dispatches to
THNN/CuDNN/nnpack based on input parameters. The general strategy is to compose
this function out of the various forward-backward pairs of specific
implementations, rather than write a monolithic function with backwards (which
is what we did before because the boilerplate of doing it otherwise would have
been very high.) The new API provides the following functions:
- _convolution, which is a fully generic, native convolution implementation
that dispatches to various other convolution implementations depending on
input characteristics. This is prefixed with an underscore because it
explicitly takes benchmark, deterministic and cudnn_enabled which are
implementation details for CuDNN. The intent is to eventually provide a
convolution that reads these parameters out of the context using #4104.
- _convolution_nogroup is a convolution implementation for non-CuDNN
algorithms which don't support group convolution natively.
- _convolution_double_backward is the generic double-backwards implementation
for convolution.
In more detail:
- Most functionality from torch/csrc/autograd/functions/convolution.cpp has been
moved into aten/src/ATen/native/Convolution.cpp
- We continue to make use of ConvParams, but we now construct the parameters
upon entry to a function from the function signature (which does not use
ConvParams; having convolution take ConvParams directly would require teaching
the code generator how to accept these as parameters, complicating ATen's API
model) and destruct them when making subprocedure calls.
- I introduce a new idiom, input_r, which represents a const Tensor& reference,
which will subsequently be assigned to a local Tensor input. This is helpful
because a lot of the existing algorithms relied on being able to assign to
locals, which is not permitted with a const reference.
- The native argument parser now supports std::array<bool,2> inputs (NB: there
MUST NOT be a space; this is the same hack as is applied to derivatives.yaml)
- Native parser now supports Tensor? arguments, which indicates a nullable
tensor. Previously this function was only used by NN methods.
- Documentation updates on THNN library
- I added an extra fgradInput argument to VolumetricConvolutionMM_updateOutput
and VolumetricConvolutionMM_accGradParameters so that its buffer list lines up
with the backward argument list. This makes it possible to write derivative
for conv3d which previously was not supported (commented out in
derivatives.yaml)
- Extra double_backward declarations for all convolution backwards functions was
added.
- You can now use the syntax Tensor? in native_functions.yaml to indicate that a
tensor argument is nullable. There are adjustments to propagate this to the
Python argument parser.
- NNPACK was ported to ATen, and ATen now builds and links against ATen if
possible. New AT_NNPACK_ENABLED macro. The nnpack functions are
nnpack_spatial_convolution.
- Some modest CuDNN convolution refactoring to remove _forward from names.
- There's a new cudnn_convolution_backward function to deal with the fact that
CuDNN convolution double backward requires you to have computed all gradients
in one go.
- Variable set_flags now checks if the tensor is undefined, fixing a silent memory
corruption.
- checkSameType updated to not raise an exception if called with Variable arguments
- "no ATen declaration found for" error message is improved to say what available declarations are
- make_variable now accepts undefined tensors, and returns an undefined tensor in this case.
* Add interpreter support for Handles/PythonOp/CppOp
This treats Handles as a first-class type in the interpreter
since this turned out to be conceptually simpler than treating
them as a separate concept, which requires a second channel for
register allocating and moving data from one op to the next.
Notes:
* The refcounting nature of tensors is factored into its own base type
so that it can be shared with other refcounted types such as handle.
* Some methods redundant with TensorBase have been deleted from Tensor
* The interpreter uses raw refcounted handles. In addition to being
able to treat Tensors and Handles as the same base object, it removes
a lot of redundant refcounting as objects moved from tensors to input/
output lists.
* aten_dispatch has been updated to work directly on the raw refcounted
lists to avoid refcounting and duplicate lists.
* Removing jit_closure.cpp, The interpreter can now handle all pathways.
* Functions like `unsafeToTensorShare` describe how
ownership transfers in the interpreter. The `Steal` variants
take rvalue references as arguments, and invalidate those
arguments to prevent potential problems.
* Make TensorTemporary is not a subtype relationship because it is too easy to
do something horribly unsafe:
```
void foo(at::Tensor bar) {
// bar destructor call release on a temporary!
}
foo(TensorTemporary(retainable)); // structure slicing!
```
Allow in-place operations on views
Adds VariableViewImpl, a subclass of VariableImpl which has a pointer to
the base Variable on which it is a view. In-place operations on views
change the grad_fn of the base.
Note that in-place operations only work on views that are the first output of the function that created them. All C++/ATen implemented functions have this behavior, but it's possible to write Python-implemented autograd functions that do not. In-place operations on these view will raise an exception.
Fixes#3313
- Cleaned up THNN and THCUNN code and kernels
- Improved THCUNN kernel performance 5x, making it match cuDNN performance
- Added support for computing softmax over arbitrary dims
NOTE: The default dim for 3D inputs is now 1 (used to be 0)
- Both functions now accept inputs with arbitrarily many dimensions
- Autograd functions no longer save the input (it's unnecessary)
- Added cuDNN bindings for softmax, but they are unused as THCUNN
matches or even exceeds cuDNN performance
This adds some generated autograd functions implemented in C++, which
are generated from derivatives.yaml. It also generates Python bindings
for the Variable methods. The generated files are:
Functions.cpp/h: subclasses of torch::autograd::Function
VariableType.cpp/h: The at::Type for autograd Variables
python_variable_methods.cpp: Python bindings to torch::autograd::Variable
python_variable_methods_dispatch.h: wrapper which releases GIL and sets the
CUDA device
python_functions.cpp/h: exposes generated autograd functions as Python
objects
The generated functions are mostly shadowed by the definitions in
variable.py. We'll remove the Python implementations in favor of the
generated C++ implementations in a subsequent commit.
Variable is now a subclass of at::Tensor backed by a VariableImpl* pImpl. The implementation of the ATen functions is defined in the auto-generated VariableType.h/cpp file.
Currently, only functions which fall through to the base type, such as sizes() and isCuda() are implemented. Differentiable ops like add() and mul() will be added in a subsequent PR.
Along the way I added converters for Variable and TracingInput. Variable should
probably be moved to a more widely known spot.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Basic idea:
- Pass buffers (marked as non-Variable tensors) as input variables to
the trace. Every buffer gets represented as an input variable
to the trace, and we remember a correspondence of the underlying
TH pointer and an input variable in the trace.
- When we initially trace a function, we DO NOT record the buffers
as edges. This is so autograd doesn't have to know anything about buffers.
If we ever turn buffers into requires_grad=False parameters, then
this problem goes away.
- When we primspec the buffer, NOW we reach into the cached buffers
(now appropriately named) and gin up the buffer information we need.
Other things:
- CppOp execution is now supported (but lightly tested) using
SimpleEval (thanks @apaszke!)
Todo:
- E2E tests need to have their hacks removed.
- Figure out what is going on with backwards
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
* Implement BatchNorm double backwards as a python function called directly from C++.
This will be converted to C++ code once ATen is integrated with autograd.
* Some performance improvements via inplace ops and reusing calculations.
* add support for groups in double backward
* add tests for group in double backward
* fix lint
* separate some tests to reduce number of test cases
* remove redundant testing for different number of output channels
Because of this Variables can no longer appear in the graph.
Every usage of a leaf Variable will leave an AccumulateGrad
function that has no outputs, but modifies var.grad as a side
effect.
The core autograd Variable, Function, and Engine no longer depend on the
Python API. This let's us implement functions in C++. In the future, we
can also multithread engine and release the GIL for most of the
non-Python backwards.
