Summary:
**Review last commit only.** Stacked on top of #10949.
This commit fixes a number of issues connected to caching
differentiability status of graphs inside graph executors,
and changes the rules for optimization of differentiable subgraphs.
Previously every one of those was instantiated as a separate graph
executor, but now they are simply heavier-optimized graph regions,
and graph executors are only instantiated for their backward.
zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/10977
Differential Revision: D9600626
Pulled By: apaszke
fbshipit-source-id: dad09a0f586e396afbd5406319c1cd54fbb8a3d3
Summary:
Operators like aten::chunk used to return a number of tensors, but
now return a list. To make it easier to do shape prop through
aten::chunk and fuse it, I've also introduced prim::ConstantChunk,
which behaves like the previous implementation (has a variable length
output list).
The downside of this PR is that the introduction of more lists to the IR causes the LSTM and MiLSTM graphs to be considered as non-differentiable by the graph executor. I verified that they are still optimize correctly, and my next patch (that changes how the specializations/differentiation works) will restore those.
zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/10949
Reviewed By: zdevito
Differential Revision: D9556823
Pulled By: apaszke
fbshipit-source-id: 33e63b17fc7247cac6cfc05eb7eb9bf069b499ee
Summary:
Please review the expects carefully to make sure there are no regressions. I tried to go over them one by one when they changed, but it's sometimes easy to miss finer details.
Summary of changes:
- Renamed `TensorType` to `CompleteTensorType`. Added a new `TensorType` which records only the scalar type, number of dimensions, and device of a value. The argument behind the rename is to encourage people to use `CompleteTensorType` less, as most passes will only have limited information available. To make transition easier `complete_type->cast<TensorType>()` works, and makes our passes work with both kinds of specialization if they don't need extra the extra detail.
- Renamed `ArgumentSpec` to `CompleteArgumentSpec`. Added a new `ArgumentSpec`, which matches argument only at the level of the new `TensorType`.
- Shape analysis can process graphs with both `CompleteTensorType` and `TensorType`.
- Fuser was a part that heavily relied on full shape information being available. Now, we simply try to fuse the largest possible graphs, and have to do run-time checks to make sure they match the code we generate. If they don't, we fall back to regular interpretation. The shape checks are implementing using an optimized method exploiting algebraic properties of shapes with broadcasting, and the relations of broadcasting with pointwise ops. A full written proof of correctness of the shape checking algorithm is included in a comment in `graph_fuser.cpp`.
zdevito ezyang mruberry ngimel csarofeen
Pull Request resolved: https://github.com/pytorch/pytorch/pull/10844
Differential Revision: D9498705
Pulled By: apaszke
fbshipit-source-id: 0c53c2fcebd871cc2a29c260f8d012276479cc61
Summary:
More clang tidy cleanups in `torch/csrc`. This time:
1. `hicpp-use-equals-default` recommends `= default` instead of `{}` for constructors/destructors. This is better practice because it expresses the intent better (https://stackoverflow.com/questions/6502828/what-does-default-mean-after-a-class-function-declaration)
2. `readability-inconsistent-declaration-parameter-name` enforces that parameter names in the declaration match parameter names in the definition. This is just generally useful and can prevent confusion and bugs.
Also updated my script a little bit.
apaszke ezyang
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9737
Differential Revision: D9069069
Pulled By: goldsborough
fbshipit-source-id: f7b3f3a4eb4c9fadc30425a153566d3b613a41ae
Summary:
```
This adds TensorIterator, a helper class for computing element-wise
operations that's intended to replace the CPU and CUDA apply utils
functions.
CPU kernels are implemented as functions that operate on strided 1-d
tensors compared to CPUApplyUtils which operated individual elements. This
allows the kernels to handle vectorization, while TensorIterator handles
parallelization and non-coalesced dimensions.
GPU kernels continue to operate on elements, but the number of
specializations is reduced. The contiguous case remains the same. The
non-contiguous case uses a single (reduced) shape for all operands and
the fast integer division from THCIntegerDivider. To avoid extra
specializations for indexing with 64-bits, large operations are split
into smaller operations that can be indexed with 32-bits.
Major semantic changes:
- No more s_add, s_mul, s_div, or s_sub. Broadcasting is handled by
TensorIterator. The autograd engine performs the reduction assuming
standard broadcasting if the gradient shape does not match the
expected shape. Functions that do not use standard broadcasting rules
should either continue to trace the expand calls or handle the
reduction in their derivative formula.
- Use ONNX v7, which supports broadcasting ops.
Performance impact:
- Small increased fixed overhead (~0.5 us)
- Larger overhead for wrapped numbers (~2.5 us)
- No significant change for ops on contiguous tensors
- Much faster worst-case performance for non-contiguous GPU tensors
- Faster CPU bias addition (~2x)
- Faster GPU bias addition (~30% faster)
Future work:
- Decrease overhead, especially for wrapping numbers in Tensors
- Handle general inter-type operations
- Extend to unary ops and reductions
- Use buffering for compute-bound operations on non-contiguous tensors
(pull in from CPUApplyUtils)
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/8919
Differential Revision: D8677600
Pulled By: colesbury
fbshipit-source-id: 61bc9cc2a36931dfd00eb7153501003fe0584afd
Summary:
Based on top of #9763 (first 3 commits belong to that PR). The first commits from this PR are "Stop using attributes ..."
I tried to separate the changes into fairly meaningful commits. I can't split them up into smaller PRs, because everything starts working and all tests pass only after the whole sequence, but hopefully this will make reviewing somewhat easier.
Known issues/regressions/future tasks:
- `aten::lerp` and `aten::clamp` are no longer fusable
- `CreateAutodiffSubgraphs` needs a rewrite
- It is much more strict now, and will miss a lot of opportunities, especially when viewing ops are involved. Our previous approach was "ignore the assumption on shape availability in gradient formulas to determine differentiability, and hope that shape prop will be robust enough to actually deliver them before we differentiate", which obviously doesn't scale well to more complex cases. We should either work on reducing the size dependency of grad formulas (feasible e.g. for `view`/`reshape`, unfeasible for `squeeze`/`unsqueeze`), or make `CreateAutodiffSubgraphs` integrate some kind of "I could integrate this node into an AD subgraph, but will I be able to infer the shape of its input" reasoning (kind of like a limited shape prop, that doesn't infer anything, and only tells if it *could* infer something).
- It sometimes creates constant-only (or constants + one node) graphs, which is useless
- Broken `aten::add` in auto-batching, because it gained a non-tensor input. I changed the test for pointwise operations to use `aten::mul` instead, but I needed to disable the LSTM cell test. I'm not sure how scalar constants should be implemented in this case, because I don't fully understand our format. cc: ChunliF
- Graph import does some hacks to recover type of constants. This code should be removed once we'll gain the ability to export the IR along with value types.
- There's still a fair amount of dead code that can be removed. I didn't want to make this diff any bigger, and removing it is an easy task.
- Graph fuser could be improved to use signature matching (possibly using `OperatorSet`) instead of basing on node kinds.
- Manual constant propagation for the `ListConstruct` node in `torch/onnx/utils.py` should be replaced with a proper constant propagation pass (or we should ensure that the one we have handles at least this case before we remove this code).
zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9807
Reviewed By: ezyang
Differential Revision: D9004285
Pulled By: apaszke
fbshipit-source-id: fe88026a765f6b687354add034c86402362508b7
Summary:
Follow up task of #9584.
Commit 1:
- change expect/cast to return shared pointers instead of raw pointer
- isSubtypeOf accept TypePtr instead. Use `x->isSubtypeOf(NumberType::get())` rather than `x->isSubtypeOf(*NumberType::get())`
Commit 2:
- to address enable_shared_from_this pitfalls, we make the constructor private and expose the factory method to make sure user can only create it using our factory method.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9786
Reviewed By: zdevito
Differential Revision: D8980441
Pulled By: wanchaol
fbshipit-source-id: e5c923fc57a701014310e77cf29985b43bb25364
Summary:
I got some tensor->variable conversion exceptions from `torch/csrc/autograd/variable.h`, which used the `TORCH_ASSERTM` macros instead of `AT_CHECK`, so they didn't have backtraces. This was such a substantial loss for debugability that I decided to update the whole codebase to use the backtrace-enabled ATen macros instead of `TORCH_ASSERT` and `JIT_ASSERT`, the latter having been an alias of the former.
ezyang apaszke zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9575
Differential Revision: D8924566
Pulled By: goldsborough
fbshipit-source-id: 7a4013b13eec9dbf024cef94cf49fca72f61d441
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9718
This patch switches the interpreter to use IValue's primitive numbers rather than tensors for computing on integers and floats. In addition to preparing the interpreter for first-class support of other types, this cleans up the handling of primitive numbers, making it possible to just use the normal operator overloading dispatch to find the right implementation for numbers. As a result of this change, a lot of other functionality needed to be updated since it was the first time we use non-tensors in a lot of places in the code base.
Notes:
* Fixes code_template.py so that multi-line strings are indented correctly when used on a standalone line
* Cast operators (`int(x)`) now are functional. Some tests have addition conversions to integers because
we no longer allow implicit tensor -> integer conversions following the same convention as in python
* prim::ListConstruct/createList has been added to the interpreter for creating lists and this has
replaced aten::stack for integers lists
* gen_jit_dispatch.py has been refactored so that non-tensor types use operators on IValues to extract
the primitives
* IValue gains a .to<T> method that is the equivalent of tensor_as but for IValue instead of at::Tensor
* `constant_as<T>` is switched over to using IValues's `.to<T>` method, to make conversion from constant->IValue->C++ type
more consistent. This functionality combined with `toIValue(Value*)` replaces the `tensor_as` and `as_tensor` family of functions.
* conditional expressions (if, loop) and operators related to them are now computed on integers rather than tensors
* IValue gains constructors for constructing from at::Scalar and converting to it. However, IValue itself will always store
the scalars as a double or int64.
* To align with python 3 syntax, TK_INT, TK_FLOAT, and TK_BOOL have been removed from the parser, and int/float/bool are just treated as special identifiers in the compiler,
along with print. These are represented as special sugared values with a `call` method implemented. For int/float/bool this implements casting behavior.
* Dropped shared_from_this from Type/Module. They were not needed and they making debugging harder because they internally throw/catch exceptions.
* Shape propagation has been updated to support running nodes that include floating point primitive types, this required some refactoring of internal functions.
* TensorToNum and NumToTensor have actual implementations as operators now
* regster_prim_ops now contains implementations of math operators for float/int primitive types, and for mixed (prim <+> tensor) versions. This removes the need for special handling in compiler.cpp
* Primitive math is now entirely handled by letting the compiler choose the right overloads. This removes tons of special casing in the compiler.
* incorporates eellison's change to allow casting from return values. Due to the addition of primitive support, the code need slight modifications, so I just pre-merged it here.
* stack.h gains generic vararg versions of push/pop that know how to convert to/from C++ types:
```
at::Tensor a;
at::Scalar b;
pop(stack, a, b);
at::Tensor c = a + b;
push(stack, c);
```
apaszke
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9584
Reviewed By: apaszke
Differential Revision: D8910546
Pulled By: zdevito
fbshipit-source-id: 0f3e60d4d22217f196a8f606549430e43b7e7e30
Summary:
**REVIEW LAST COMMIT ONLY**
As discussed in our yesterday's meeting. Nodes can be now matched to particular overloads using the `matches(...)` function:
```cpp
n->matches("aten::type_as(Tensor self, Tensor other) -> Tensor")
```
This also changes the shape prop and peephole passes to use those functions for matching. This fixes a few bugs, makes them much more robust, and prepares us for removal of attributes.
zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9567
Reviewed By: zdevito
Differential Revision: D8938482
Pulled By: apaszke
fbshipit-source-id: eb2382eeeae99692aada2d78d5d0c87c8ef1545e
Summary:
This PR adds machinery to cache the schema in an IR node, and allows lookups of (possibly) constant inputs by their names (instead of position). The new methods are:
- `at::optional<T> get<T>(Symbol name)` - if the argument called name is a constant, then casts it to type `T` and returns it. If it's not constant returns `nullopt`. Raises an error if there's no argument with that name.
- `at::optional<IValue> get<T>(Symbol name)` - like above, but packs the result in an IValue
- `Value* getValue(Symbol name)` - retrieves a `Value*` for an argument (no need to know its position).
All above functions currently inspect the attributes as well, but that's only so that I could start using them in other places in the JIT without disrupting our current functionality. I wanted this diff to be a preparation that doesn't change the semantics too much, and so both the tracer and script create nodes with attributes. The next PR will put that to a stop, and hopefully the changes we need to make to other components will be simpler thanks to what I did here.
One more thing I'd like to do before actually stopping creating the non-attributed nodes is to have a convenient way of creating a schema programmatically, matching nodes against it, and creating them without having to pack inputs into flat argument lists (which is quite error prone).
zdevito
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9505
Reviewed By: ezyang
Differential Revision: D8915496
Pulled By: apaszke
fbshipit-source-id: 39d14fc9a9d73d8494f128367bf70357dbba83f5
Summary:
IValue is short for interpreter value. It is used frequently so a short name is important.
This will allow us to implement more non-tensor types in an efficient way and remove
many hacks from the compiler.
This PR is limited. It only introduces IValue and changes interpreter to use it.
Follow up PRs will:
* Change the way aten_ops consume non-tensor types so that integer lists,
are no longer represented as Tensors.
* Introduce TensorList as a fundamental type and remove all vararg handling in gen_jit_dispatch
* Change the compiler to implement math on primitive numbers rather than converting to tensors.
jamesr66a apaszke
Pull Request resolved: https://github.com/pytorch/pytorch/pull/9368
Reviewed By: ezyang
Differential Revision: D8817598
Pulled By: zdevito
fbshipit-source-id: 29dce80611ce5f6384234de9d12a67861d2b112f
This commit implements the solution proposed in https://github.com/pytorch/pytorch/issues/8410
to workaround the need to create zero tensors with the same shape as inputs.
It introduces the concept of a LinearBlock which marks places in the code
where we know if all the inputs to the node are zero, then the outputs
to the node are also zero. Autodiff introduces LinearBlocks around
backwards functions, which have this property. specializeUndef then
propagates Undef nodes using this information.
Notes:
* Since we do not always specialize, we have a pass LowerLinearBlocks
that replaces the block with an if statement that dynamically guards
the Undef case.
* We introduce AutogradAdd which is addition that still works when
its inputs might be undefined. In cases where we specialize this will
get removed in favor of a normal add, but there are cases where
gradient graphs do not specialize (e.g. when they are not differentiable,
but a derivative is required) so it is important for this op to be executable.
* Created TensorOptions
Storing the type in TensorOptions to solve the Variable problem
Created convenience creation functions for TensorOptions and added tests
Converted zeros to TensorOptions
Converted rand to TensorOptions
Fix codegen for TensorOptions and multiple arguments
Put TensorOptions convenience functions into torch namespace too
All factory functions except *_like support TensorOptions
Integrated with recent JIT changes
Support *_like functions
Fix in place modification
Some cleanups and fixes
Support sparse_coo_tensor
Fix bug in Type.cpp
Fix .empty calls in C++ API
Fix bug in Type.cpp
Trying to fix device placement
Make AutoGPU CPU compatible
Remove some auto_gpu.h uses
Fixing some headers
Fix some remaining CUDA/AutoGPU issues
Fix some AutoGPU uses
Fixes to dispatch_tensor_conversion
Reset version of new variables to zero
Implemented parsing device strings
Random fixes to tests
Self review cleanups
flake8
Undo changes to variable.{h,cpp} because they fail on gcc7.2
Add [cuda] tag to tensor_options_cuda.cpp
Move AutoGPU::set_index_from into .cpp file because Windows is stupid and sucks
Fix linker error in AutoGPU.cpp
Fix bad merge conflict in native_functions.yaml
Fixed caffe2/contrib/aten
Fix new window functions added to TensorFactories.cpp
* Removed torch::TensorOptions
Added code to generate wrapper functions for factory methods
Add implicit constructor from Backend to TensorOptions
Remove Var() from C++ API and use torch:: functions
Use torch:: functions more subtly in C++ API
Make AutoGPU::set_device more exception safe
Check status directly in DynamicCUDAHooksInterface
Rename AutoGPU to DeviceGuard
Removed set_requires_grad from python_variables.h and warn appropriately in Variable::set_requires_grad
remove python_default_init: self.type()
Add back original factory functions, but with deprecation warnings
Disable DeviceGuard for a couple functions in ATen
Remove print statement
Fix DeviceGuard construction from undefined tensor
Fixing CUDA device compiler issues
Moved as many methods as possible into header files
Dont generate python functions for deprecated factories
Remove merge conflict artefact
Fix tensor_options_cuda.cpp
Fix set_requires_grad not being checked
Fix tensor_new.h
TEMPORARILY put some methods in .cpp files to see if it solves issues on windows and mac
Fix bug in DeviceGuard.h
Missing includes
TEMPORARILY moving a few more methods into .cpp to see if it fixes windows
Fixing linker errors
* Fix up SummaryOps to use new factories
Undo device agnostic behavior of DeviceGuard
Use -1 instead of optional for default device index
Also move DeviceGuard methods into header
Fixes around device index after optional -> int32_t switch
Fix use of DeviceGuard in new_with_tensor_copy
Fix tensor_options.cpp
* Fix Type::copy(
* Remove test_non_float_params from ONNX tests
* Set requires_grad=False in ONNX tests that use ints
* Put layout/dtype/device on Tensor
* Post merge fixes
* Change behavior of DeviceGuard to match AutoGPU
* Fix C++ API integration tests
* Fix flip functions
* add comparison operators to jit
* try to fix CI
* address review comments
* fix type of comparison ops result
* address review comments
* fix indentation
* add comments
* require type_as to have non-dynamic tensor arg
* Typo (should check if template argument of type_as, inputs()[1], is tensor)
* Use .at() instead of []
* Use .at() again
This lets aten::expand be differentiable in torchscript. It was probably
omitted from the list by accident in the past b/c gradientForNode does
already support aten::expand.
Also adds a test to check expand and its gradient in a torchscript fn.
* Namespaced symbols
- Our interned strings now have structure, "ns::symname" rather than just
"symname" before. We support efficient namespace testing for uniques
by encoding the namespace in one byte in the Symbol internal representation.
See torch/csrc/jit/interned_strings.h for a more in-depth implementation
discussion.
- All uses of ksymbol are now attr::symbol (or some appropriate namespace).
The valid namespaces are prim, attr, onnx and aten.
- Symbol is bound in Python as a qualified string "attr::symbol", EXCEPT for the
attribute setting/getting API, whose symbols must always be attr
symbols; they get special cased to assume strings are passed.
There's a little bit of naughtiness in the implementation, maybe you know
how to solve it.
- However, the g.op() convenience function assumes that you're generating
ONNX operators, unless you explicitly qualify.
- All ATen operators and nodes have built-in interned strings generated
for them, so you should never have to write a string literal ever again.
The tracing code is adjusted to use it.
- ONNX exporter now properly tests to see that all operators are in
onnx namespace before accepting the export. This is way more
robust than the previous exporter, which would be willing to
export capitalized operators which were not actually ONNX operators.
- A slight organizational change for symbolic.py; this module now ONLY
contains aten operators. In particular, the exporter for Constant
has moved into utils.py (along with Undefined, from the C++ side),
since primitive ops get "special treatment."
- The un-inplacing logic in recording is more robust, so that we don't
delete a trailing underscore from __and__. This never affected us
before because we didn't have any tests for it.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
* Delete ""_sym literal form.
Two reasons:
1. It's unnecessary now; all of the uses of the literal form would
be better directly referring to the interned string (esp. since
now we are autogenerating symbols.)
2. When I add namespacing, there will be no convenient way to specify
the desired namespace with just _sym. If we add it back, we would
need distinct suffixes for each different type. Easiest to delete
it while we don't need it.
Add script::Module C++ class to represent script modules
switch AST -> IR conversion to work on Modules/Methods rather than raw graphs
function-only AST -> IR conversion is just a simplified case where there is
only one module with a single method and no parameters.
introduce SugaredValue in compiler.h to represent values in scope in a script
function that are not first-class and that get desugared. This is used to
represent the module's self parameter, as well as python function calls,
and method calls on tensor
provide a Python ScriptModule that provides a nice API on top of script::Module
allowing for the definition of script modules with methods, parameters,
and submodules
Not in this PR but intended for the future:
ScriptModule actually subclasses nn.Module, with most methods implemented
Unification of tracedmodule and script module functionality into one container class.
Detailed changelog:
* Switch compiler over to using Module, but don't
use them yet.
* Remove intermediate attribute encoding in compiler
* Create SugaredValue object to handle resolution
of compiled module.
* switch to_ir to modules, implement Select
* hacky python wrappers
* Private ScriptModule
* Add `define` to script module
* Attributes use TK_LIST_LITERAL
this anticipates adding a real list literal expression to the language.
* Add a metaclass to make sure script stubs are registered
* Add a test
* Doc createResolutionCallback
* Docs and minor editing
* Address PR comments
* Document
* Fix unicode issue
* Support native namespace functions with type dispatch.
Use 'ones' as an example. Note this is a "halfway" solution; i.e. the call chain is:
at::ones(shape, dtype) -> dtype.ones(shape, dtype) -> CPUFloatType.ones(shape, dtype) -> at::native::ones(shape, dtype)
The "nicer" solution would probably be something like:
at::ones(shape, dtype) -> dtype.ones(shape) -> CPUFloatType.ones(shape) -> at::native::ones(shape, this)
* Fix type inference.
* Fix test install.
* Fix extensions.
* Put dtype argument at the beginning.
* Fix extension.cpp.
* Fix rnn.
* Move zeros in the same manner.
* Fix cuda.
* Change randn.
* Change rand.
* Change randperm.
* Fix aten contrib.
* Resize in randperm_out.
* Implement eye.
* Fix sparse zeros.
* linspace, logspace.
* arange.
* range.
* Remove type dispatch from gen_python_functions.
* Properly generate maybe_init_cuda for type dispatch functions not named type.
* Don't duplicate dtype, this parameters for native type dispatched functions.
* Call VariableType factory methods from the base type so it gets version number 0.
* Address review comments.
Support shape propagation with control-flow
* This allows us to enable optimization in the GraphExecutor for most
script tests.
* Changes Type to always be present (non-null) on a Value, removing `hasType()`
and `typeOption()`. A new type kind 'DynamicType' now represents when
a specific type has not been determined.
* If/Loop nodes propagate shapes/types in the simple cases where types of
outputs do not change depending on where control flows. In other
cases, we propagate DynamicType to indicate we do not know what
the shape will be.
* Remove the `cond` input to the body of Loop to simplify handling in
interpreter and shape propagation.
* Bugfix for zero-dim contiguousStridesOf
* Remove addValues and use WithInsertPoint
* Use blocks to simplify differentiate
Using @ezyang's suggestion, this change uses a block rather than
staging annotations to represent the reverse pass. This allows us
to reuse the machinery to copy graphs/blocks to extract the
reverse pass concisely.
This also change the input order of Gradients df to:
[output vjps][temporary vjps][captures]
In addition to being simpler to generate in this order, it also
will allow ExecutionPlan to append the captures onto the already-
existing input list of vjps that are given by the autograd,
rather than have to prepend them, which should be slightly cheaper.
* Enforce that input capture are before outputs
This changes the Gradient struct to enforce that input
captures appear before output captures in the capture list,
which makes it easier to use in ExecutionPlan.
This commit is getting the IR ready for representing ONNX control flow.
It adds nested blocks to the IR.
* Each node now has blocks(), addBlock(), and eraseBlock() similar to a node's
output list.
* Blocks are a property of every node rather than an attribute because
to make it easier to manage the lifetime of the containing nodes and because
the behavior of cloning Blocks will likely be different from the way we clone other
attributes.
* A block itself has a list of nodes, as well as inputs and outputs.
The meaning of the nested input/output nodes are specific to the particular
node kind containing the block. It is safe to assume inputs to a block will be
in scope in the block.
* Each Block has an owningNode() and each node has an owningBlock().
The owningNode of the top-most block is null.
* Values are lexically scoped: nested blocks can use values from outer blocks
that have been defined in previous nodes. Lint has been updated with these
new scoping rules.
* This change preserves almost all of the pre-Block API. No attempt has been made
to make optimizations aware of Blocks. This will need to be done on a case-by-case
basis as we make optimizations capable of handling Blocks.
This adds the initial implementation of graph executor for the new JIT design. It includes a few python tests ensuring that nograd, backward, and double-backward cases work for simple examples and some corner cases. More work needs to be done to performance optimize as there are many extra copies and places where we hold onto variables longer than we should. These are noted in the comments.
This pass splits differentiable subgraphs into their own Node,
similar to a fusion group.
This initial implementation does not create optimal subgraphs, but
it works well in the case where most things are differentiable,
and has the building blocks (`mergeNodes`) to extend to the
better implementation.
