Summary: `_ConstraintTarget` is an internal data structure that has some redundancy: tensors are identified by their id but also carry a weak reference. The weak reference was probably useful a year back but everything is done with ids right now, and the lifetime of these tensors ensures that using their ids is OK.
Test Plan: existing tests
Differential Revision: D61488816
Pull Request resolved: https://github.com/pytorch/pytorch/pull/133890
Approved by: https://github.com/tugsbayasgalan
Sorryyyyy for another refactor. This splits `_process_dynamic_shapes` into 3 parts:
1. `_combine_args` - mostly the same thing
2. `_check_dynamic_shapes`, which is responsible for raising 99% of UserErrors if the dynamic shapes spec is invalid (minus 1 UserError with DerivedDims)
3. `_process_dynamic_shapes`, which for now, is the same thing, minus the stuff in 2.
This refactor is helpful for incoming automatic dynamic shapes work, because, we're switching to `assume_static_by_default=False`, which is what `_dynamo.export` currently does. This means any unspecified dims are allocated a symbol, in contrast to export today which keeps unspecified dims static. Historically this has been desirable - export users don't want too much dynamism. So we want to change how the spec is translated into constraints.
This means when we switch over to automatic dynamic shapes, we want to plug in something in between steps 2. and 3. which patches up the spec for `assume_static_by_default=False`, filling in static shapes for any unspecified dims, and potentially clearing out the auto-dynamic dims (since they're no-ops). We would do this in-between 2. and 3. to keep `_process_dynamic_shapes` semantically the same, since it's used with `_dynamo.export`.
We could do this without a refactor, plugging in this transform before `_process_dynamic_shapes`, but since that function's responsible for both spec checking + constraint production, moving spec checking to before we transform the specs helps guarantee we're raising errors on what the user's specified, and not an internal export bug.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/133391
Approved by: https://github.com/avikchaudhuri
Summary:
- moves logging functionalities into `torch/_export/db/logging.py` file.
- add a check in `_dynamo/eval_frame.py` to check for optional input and error out with `UnsupportedError`
- change the case name of `torch_sym_int` to `unsupported_operator`
- Check if the case name is registered in exportdb, if so, we give a link to the case in exportdb.
- TODO: add test
Test Plan:
CI
Running the example in https://pytorch.org/docs/main/generated/exportdb/index.html#optional-input gives the following error logging:
```
E0730 10:53:33.687000 4155538 torch/_dynamo/eval_frame.py:1086] Parameter y is optional with a default value of tensor([[-0.1633, 1.2414, -0.1071],
E0730 10:53:33.687000 4155538 torch/_dynamo/eval_frame.py:1086] [-0.1936, -0.9425, -0.0824]])
E0730 10:53:33.688000 4155538 torch/export/_trace.py:1043] See optional_input in exportdb for unsupported case. https://pytorch.org/docs/main/generated/exportdb/index.html#optional-input
......
File "/data/users/shangdiy/fbsource/buck-out/v2/gen/fbcode/389acaeb40d57230/tutorials/pytorch/nntest/__torchtest__/torchtest#link-tree/torch/_dynamo/eval_frame.py", line 1091, in produce_matching
raise Unsupported(
torch._dynamo.exc.Unsupported: Tracing through optional input is not supported yet
```
It also logs a `export.error.classified` event in Scuba.
Reviewed By: zhxchen17
Differential Revision: D60427208
Pull Request resolved: https://github.com/pytorch/pytorch/pull/132420
Approved by: https://github.com/zhxchen17
Summary: The JK disables dynamo by passing None to set_eval_frame.
Test Plan:
Ran buck test mode/opt caffe2/test/dynamo:test_dynamo
Buck UI: https://www.internalfb.com/buck2/1fec33b4-c95a-4bdf-b47b-7c0b8ab9e24a
Test UI: https://www.internalfb.com/intern/testinfra/testrun/2814750010105363
Network: Up: 0B Down: 0B
Jobs completed: 9596. Time elapsed: 28:54.5s.
Tests finished: Pass 4796. Fail 0. Fatal 0. Skip 17. Build failure 0
Also manually write a small local test with torch.compile and toggles the code to see if PT2 can be disabled. Validated with running the test and observing the log.
PT2 enabled: P1486847242. Can see dynamo log about graph breaks.
PT2 disabled: P1486847727. No dynamo log. The newly added warning printed.
Reviewed By: ezyang
Differential Revision: D59968925
Pull Request resolved: https://github.com/pytorch/pytorch/pull/131258
Approved by: https://github.com/c00w
## save&load support for OptimizedModule
[Issue Description](https://github.com/pytorch/pytorch/pull/101651)
English is not my native language; please excuse typing errors.
This pr is based on commit b9588101c4d3411b107fdc860acfa8a72c642f91\
I'll do something with the merge conflicts later
### test result for test/dynamo
Conclusion:\
It performs the same as before as far as I can see.
ENV(CPU only):\
platform linux -- Python 3.10.14, pytest-7.3.2, pluggy-1.5.0\
configfile: pytest.ini\
plugins: anyio-3.7.1, cpp-2.3.0, flakefinder-1.1.0, xdist-3.3.1, xdoctest-1.1.0, metadata-3.1.1, html-4.1.1, hypothesis-5.35.1, rerunfailures-14.0
#### before this pr:
[before](https://github.com/pytorch/pytorch/files/15329370/before.md)
#### after this pr:
[after](https://github.com/pytorch/pytorch/files/15329376/after.md)
### some changes
1. add test_save_and_load to test/dynamo/test_modules.py with & without "backend='inductor'"
2. add \_\_reduce\_\_ function to OptimizedModule and derived classes of _TorchDynamoContext for pickling & unpickling
3. change the wrappers into wrapper classes ( including convert_frame_assert, convert_frame, catch_errors_wrapper in torch/_dynamo/convert_frame.py & wrap_backend_debug in torch/_dynamo/repro/after_dynamo.py )
4. change self.output.compiler_fn into innermost_fn(self.output.compiler_fn) in torch/_dynamo/symbolic_convert.py to get the origin compiler_fn and to avoid the "compiler_fn is not eager" condition
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126374
Approved by: https://github.com/msaroufim, https://github.com/jansel
Use `typing_extensions.deprecated` for deprecation annotation if possible. Otherwise, add `category=FutureWarning` to `warnings.warn("message")` if the category is missing.
Note that only warnings that their messages contain `[Dd]eprecat(ed|ion)` are updated in this PR.
Resolves#126888
- #126888
This PR is split from PR #126898.
- #126898
------
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127689
Approved by: https://github.com/Skylion007
With the current state of export's dynamic shapes, we struggle with guards and constraints that are beyond the current dynamic shapes language, expressed with dims and derived dims. While we can compile and guarantee correctness for guards within the current language (e.g. min/max ranges, linear relationships, integer divisibility) we struggle to dynamically compile guards which extend beyond that.
For these "complex" guards, we typically do either of the following: 1) raise a constraint violation error, along the lines of "not all values of <symbol> in the specified range satisfy <guard>", with or without suggested fixes, 2) specialize to the provided static values and suggest removing dynamism, or 3) fail compilation due to some arbitrary unsupported case. Previous [work](https://github.com/pytorch/pytorch/pull/124949) went towards resolving this by disabling forced specializations, instead allowing the user to fail at runtime with incorrect inputs.
In this PR, relying on [hybrid backed-unbacked symints](https://github.com/pytorch/pytorch/issues/121749), [deferred runtime asserts](https://github.com/pytorch/pytorch/blob/main/torch/fx/passes/runtime_assert.py), and the function [_is_supported_equivalence()](d7de4c9d80/torch/fx/experimental/symbolic_shapes.py (L1824)), we add a flag `_allow_complex_guards_as_runtime_asserts` which allows the user to compile exported programs containing these guards and maintain dynamism, while adding correctness checks as runtime assertions in the graph.
Hybrid backed-unbacked symints allow us to easily bypass "implicit" guards emitted from computation - guards that we ~expect to be true. Popular examples revolve around reshapes:
```
# reshape
def forward(self, x, y): # x: [s0, s1], y: [s2]
return x.reshape([-1]) + y # guard s0 * s1 = s2
This leads to the following exported program
class GraphModule(torch.nn.Module):
def forward(self, x: "f32[s0, s1]", y: "f32[s2]"):
sym_size_int: "Sym(s2)" = torch.ops.aten.sym_size.int(y, 0)
mul: "Sym(-s2)" = -1 * sym_size_int; sym_size_int = None
sym_size_int_1: "Sym(s0)" = torch.ops.aten.sym_size.int(x, 0)
sym_size_int_2: "Sym(s1)" = torch.ops.aten.sym_size.int(x, 1)
mul_1: "Sym(s0*s1)" = sym_size_int_1 * sym_size_int_2; sym_size_int_1 = sym_size_int_2 = None
add: "Sym(s0*s1 - s2)" = mul + mul_1; mul = mul_1 = None
eq: "Sym(Eq(s0*s1 - s2, 0))" = add == 0; add = None
_assert_scalar = torch.ops.aten._assert_scalar.default(eq, "Runtime assertion failed for expression Eq(s0*s1 - s2, 0) on node 'eq'"); eq = None
view: "f32[s0*s1]" = torch.ops.aten.view.default(x, [-1]); x = None
add_1: "f32[s0*s1]" = torch.ops.aten.add.Tensor(view, y); view = y = None
return (add_1,)
```
Another case is symbol divisibility:
```
def forward(self, x): # x: [s0, s1]
return x.reshape([-1, x.shape[0] - 1]) # Eq(Mod(s0 * s1, s0 - 1), 0)
```
Applying deferred runtime asserts also helps dynamic compilation for "explicit" complex guards that typically cause problems for export. For example we can generate runtime asserts for not-equal guards, and complex conditions like the following:
```
class Foo(torch.nn.Module):
def forward(self, x, y):
# check that negation of first guard also shows up as runtime assertion
if x.shape[0] == y.shape[0]: # False
return x + y
elif x.shape[0] == y.shape[0] ** 3: # False
return x + 2, y + 3
elif x.shape[0] ** 2 == y.shape[0] * 3: # True
return x * 2.0, y * 3.0
```
For the above graph we will generate 3 runtime assertions: the negation of the first 2, and the 3rd condition as a guard.
One additional benefit here over the current state of exported programs is that this adds further correctness guarantees - previously with explicit complex guards, if compilation succeeded, the guards would be ignored at runtime, treated as given.
As shown above, the runtime asserts appear as math ops in the graph, generated by the sympy interpreter, resulting in an _assert_scalar call. There is an option to avoid adding these asserts into the graph, by setting `TORCH_DYNAMO_DO_NOT_EMIT_RUNTIME_ASSERTS=1`. This results in the "original" computation graph, with dynamism, and any incorrect inputs will fail on ops during runtime. Further work could go into prettifying the printer, so the majority of the graph isn't guard-related.
Ideally this PR would subsume and remove the recently added [_disable_forced_specializations](https://github.com/pytorch/pytorch/pull/124949) flag, but that flag still handles one additional case of specialization: single-variable equalities where the symbol is solvable for a concrete value: see this [PR](https://github.com/pytorch/pytorch/pull/126925)
This PR doesn't change any behavior around data-dependent errors/unbacked symints yet, that could be further work.
NOTE: will take naming change suggestions for the flag :)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127129
Approved by: https://github.com/avikchaudhuri
Use `typing_extensions.deprecated` for deprecation annotation if possible. Otherwise, add `category=FutureWarning` to `warnings.warn("message")` if the category is missing.
Note that only warnings that their messages contain `[Dd]eprecat(ed|ion)` are updated in this PR.
UPDATE: Use `FutureWarning` instead of `DeprecationWarning`.
Resolves#126888
- #126888
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126898
Approved by: https://github.com/albanD
Pull Request resolved: https://github.com/pytorch/pytorch/pull/125543
This PR address 2 issues with derived dim suggested fixes, 1) newly introduced roots, and 2) root swapping.
1 | Newly introduced roots appear with modulo guards, e.g. Mod(dx, 2) = 0 suggests dx is a derived dim equal to 2 * _dx, introducing a new root _dx. Currently the final suggested fixes handle this correctly, but we can get intermediate results where related derived dims don't rely on a unified root, and are a mixture of min/max range and derived suggestions.
For example:
```
"dx": {"eq": 3*_dx-1, "max": 36}
"dy": {"eq": dx+1}
This should lead to suggested fixes
_dx = Dim('_dx', max=12)
dx = 3 * _dx - 1
dy = 3 * _dx
```
This PR prettifies the suggested fixes routine by unifying to a single root, and making each intermediate suggestion either a derived dim or min/max range, not both.
2 | The current suggested fixes for derived dims can lead to root dims/derived dims being swapped, e.g. `dy - 1, dy` -> `dx, dx + 1`. This leads to problematic suggested fixes that look like `dy - 1 = Dim("dy - 1")` since we don't have access to the original variable name.
This PR only adds a suggested fix for the root dim, and removes all other derived suggestions.
For example, with the export test case test_derived_dim_out_of_order_simplified:
```
_dimz = torch.export.Dim("_dimz", min=6, max=8)
dimy = _dimz - 1
dimx = dimy - 1
dimz = torch.export.Dim("dimz", min=6, max=8) # doesn't work, should be = _dimz
class Foo(torch.nn.Module):
def forward(self, x, y, z):
return x + y[1:] + z[2:]
foo = Foo()
u, v, w = torch.randn(5), torch.randn(6), torch.randn(7)
export(
foo,
(u, v, w),
dynamic_shapes=({0: dimx}, {0: dimy}, {0: dimz}),
)
```
Before:
```
Suggested fixes:
_dimz = Dim('_dimz', min=3, max=9223372036854775807) # 2 <= _dimz - 1 <= 9223372036854775806
_dimz - 2 = Dim('_dimz - 2', min=4, max=6)
_dimz = Dim('_dimz', min=2, max=9223372036854775806) # 2 <= _dimz <= 9223372036854775806
_dimz - 1 = _dimz - 1
dimz = _dimz
```
New suggested fixes:
```
Suggested fixes:
dimz = _dimz
```
Note: This assumes the specified derived relations between dims are correct. This should be valid because: 1) if the relation is plain wrong (e.g. (dx, dx - 1) provided with inputs (6, 4)), this gets caught in beforehand in produce_guards. 2) if the relation is correct but does not match the emitted guard, for example:
```
def forward(self, x, y):
return x.reshape([-1]) + y # guard: s0 * 2 = s1
dx = Dim("dx")
export(
model,
(torch.randn(6, 2), torch.randn(12)),
dynamic_shapes={"x": (dx, 2), "y": (dx + 6, )}
)
```
This produces two linear equations, leading to specialization since a) produce_guards is able to solve for a concrete value, and b) the export constraint solver will anyways force specializations due to range constraints.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/125543
Approved by: https://github.com/avikchaudhuri
The original change was about 9.5% slower than then before #122074 .
This improves it to be only about 1.4% slower.
Also touched up some unrelated nits that the linter complained about.
Fixes#126293
Ran torchbench 3 times on each change. Perf values before (stable), after (fix),
and with #122074 backed out (backout):
```
../inductor-tools/scripts/modelbench/inductor_single_run.sh single inference performance torchbench pyhpc_isoneutral_mixing amp first dynamic cpp
stable:
43.948x
45.754x
44.906x
fix:
47.505x
49.987x
47.493x
backout:
48.243x
48.199x
48.192x
../inductor-tools/scripts/modelbench/inductor_single_run.sh single inference performance torchbench pyhpc_equation_of_state amp first static default
stable:
15.224x
13.286x
15.354x
fix:
16.402x
16.370x
16.183x
backout:
16.554x
16.675x
16.787x
../inductor-tools/scripts/modelbench/inductor_single_run.sh single inference performance torchbench lennard_jones float32 first static default
stable:
1.712x
1.651x
1.640x
fix:
1.804x
1.798x
1.792x
backout:
1.864x
1.824x
1.836x
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126996
Approved by: https://github.com/jansel
We save and restore the DynamicLayerStack during frame eval but since fx graph has no way to express a try/finally we just assume it will happen. If we throw an exception between the push and pop to the stack then we're left in a state that affects following operations poorly. Make sure that if it's in a bad state we restore it after frame eval.
Repro:
before:
```
$ rm test/dynamo_skips/TestSparseCPU.test_log1p_cpu_uint8
$ rm test/dynamo_expected_failures/FuncTorchHigherOrderOpTests.test_vmap_free_tensor
$ PYTORCH_TEST_WITH_DYNAMO=1 pytest test/jit/test_sparse.py test/dynamo/test_dynamic_shapes.py test/inductor/test_torchinductor_dynamic_shapes.py test/test_sparse.py -k 'test_log1p_cpu_uint8'
============= 1 passed, 8588 deselected in 9.75s =============
$ PYTORCH_TEST_WITH_DYNAMO=1 pytest test/jit/test_sparse.py test/dynamo/test_dynamic_shapes.py test/inductor/test_torchinductor_dynamic_shapes.py test/test_sparse.py -k
'test_vmap_free_tensor_dynamic_shapes or test_log1p_cpu_uint8'
================== short test summary info ===================
FAILED [0.0632s] test/test_sparse.py::TestSparseCPU::test_log1p_cpu_uint8 - AssertionError: "only Tensors of floating point dtype can require gradients"
does not match "You are attempting to call Tensor.requires_grad_() (or perhaps using torch.autograd.functional.* APIs) inside of a function ...
======= 1 failed, 1 skipped, 8587 deselected in 10.99s =======
```
(Note that adding test_vmap_free_tensor_dynamic_shapes causes test_vmap_free_tensor_dynamic_shapes to fail)
after:
```
$ rm test/dynamo_skips/TestSparseCPU.test_log1p_cpu_uint8
$ rm test/dynamo_expected_failures/FuncTorchHigherOrderOpTests.test_vmap_free_tensor
$ PYTORCH_TEST_WITH_DYNAMO=1 pytest test/jit/test_sparse.py test/dynamo/test_dynamic_shapes.py test/inductor/test_torchinductor_dynamic_shapes.py test/test_sparse.py -k 'test_log1p_cpu_uint8'
============= 1 passed, 8588 deselected in 9.89s =============
$ PYTORCH_TEST_WITH_DYNAMO=1 pytest test/jit/test_sparse.py test/dynamo/test_dynamic_shapes.py test/inductor/test_torchinductor_dynamic_shapes.py test/test_sparse.py -k
'test_vmap_free_tensor_dynamic_shapes or test_log1p_cpu_uint8'
======= 1 passed, 1 skipped, 8587 deselected in 11.34s =======
```
(test_vmap_free_tensor_dynamic_shapes passes either way)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/122074
Approved by: https://github.com/oulgen
This PR has a lot of "draw the rest of the fucking owl" energy. Here's how to break it down.
1. **torch/_inductor/graph.py** - We start by tightening unbacked symbol invariants. Specifically, as we lower FX nodes, we check whether or not every unbacked_binding recorded on the FX node meta, actually ends up getting bound (according to get_unbacked_symbol_defs) in all the buffers generated by the lowering. Hopefully this invariant is self evident. This leads to a lot of failures.
2. **torch/_inductor/ir.py** - Problem 1: There is softness in how Inductor computes defs of unbacked symbols in IR node. Previously, we tried to infer it by looking at the output sizes/strides/etc and see if new unbacked symbols popped up that we hadn't seen in the inputs. I don't know exactly what was buggy about the old code, but sometimes we would fail to notice an unbacked symbol had been bound, or rebind an unbacked symbol multiple times. Fortunately, thanks to the earlier PRs in our stack, we now have a nice list of unbacked symbol bindings from FX, so we now just store it directly on ExternKernel and use it directly to report defs. This has to be done twice: once for FallbackKernel (e.g., nonzero) and once for DynamicScalar (e.g., item) (see also **torch/_inductor/lowering.py**, **torch/_inductor/codegen/wrapper.py** and **torch/_inductor/codegen/cpp_wrapper_cpu.py** for the lowering and codegen changes for item)
* **process_kernel** - Sidequest! It turns out that Inductor lowering can reallocate unbacked symbols. This happens specifically when we repropagate fake tensors through the operator in `process_kernel`. This repropagation process is necessary because Inductor may have changed the strides of input tensors, and it must now recompute the strides so that it can continue to appropriately plan the rest of the lowering process. This is fine: we just make sure we do the rebind unbacked + compute_unbacked_bindings dance we've been doing previously in the PR stack. But instead of putting unbacked_bindings on a new FX node, they go straight into our unbacked_bindings on the Inductor IR node.
* **codegen_unbacked_symbol_defs** - Sidequest! FallbackKernel lowering is done in two steps. First, you emit the FallbackKernel buffer. Then, you emit MultiOutput buffers which actually give access to the individual outputs of FallbackKernel, which may have been multi-output. There is a design decision here: does the FallbackKernel bind the unbacked symbols, or the MultiOutput buffer? Historically, we put the binding on MultiOutput buffer, because it's more convenient: the FallbackKernel buffer is fake, in fact, it doesn't even get a name in C++ codegen. But it's kind of inconsistent with the keypath model that we've been tracking unbacked bindings with: if you have a multi-output node, you'd expect a keypath like `[0].size()[0]` representing the first output's first dimension size. That suggests that it's the FallbackKernel that should define the things. So that was my first implementation. Unfortunately, the C++ codegen is too cursed and I could not understand how to make it work in that case. So now we just unsoundly assume you cannot have multi-output data dependent output, and do the codegen in MultiOutput. There are some comments explaining exactly what we are improperly assuming.
3. **_rename_unbacked_to** in **torch/fx/experimental/symbolic_shapes.py** - Previously, when we renamed unbacked symbols, we clobbered any facts we previously knew about them. So for example, if we had a replacement `u0 -> s0` but then we renamed u0 to u1, we would now setup the replacement `u0 -> u1`, clobbering the old replacement. This apparently didn't matter in earlier PRs in the stack, but with Inductor now on the ball, there were some tests that indicated this was a problem. The solution is easy: if u0 had a preexisting replacement, reapply it to u1. However...
* **torch/_functorch/_aot_autograd/collect_metadata_analysis.py** - When we run forward analysis, this triggers fake tensor repropagation and fresh allocations. Previously, we just cleared out the pending symbols when finished the analysis. But with the change above, this would also migrate replacements to the new symbols... which are now dead. So now we explicitly suppress generation of these symbols with `ignore_fresh_unbacked_symbols` so that no rebinding happens at all.
* **torch/_dynamo/eval_frame.py** - same deal; I just searched for all sites we called clear() on pending
4. The last step is fixing the long tail of extra problems that show up, now that unbacked_bindings are load bearing into Inductor
* **torch/_dynamo/eval_frame.py** - Some of the exports are making copies of nodes without repropagating fake tensors, so in this case, it is important to also copy the `unbacked_bindings` (apparently this didn't matter before without the Inductor changes)
* **torch/_export/pass_base.py** - I discover that this is doing fake tensor repropagation via a test suite failure. Do the same playbook as AOTAutograd: PropagateUnbackedSymInts too! Actually, they also have implemented their own tracer as well, so do the same playbook as proxy_tensor: record unbacked_bindings on the newly traced nodes. UGH code duplication.
* **torch/_subclasses/fake_tensor.py**, **torch/_subclasses/fake_impls.py** (with call site updates at **torch/_functorch/_aot_autograd/traced_function_transforms.py** and **torch/fx/passes/fake_tensor_prop.py**) - What's this new epoch thing? I noticed that sometimes I would be retracing, call nonzero() on a fake tensor, and not allocate a new unbacked symbol. This is actually bad, because if I don't get a new unbacked symbol, I don't know there's a binding site, and `unbacked_bindings` is now missing a binding. The reason for this is memoization: if I reuse the exact same fake tensor on my retrace, it will already have an unbacked symint memoized on it and we will short circuit allocation. Well, that's no good. So I associate the memos with a fake tensor epoch, and every time you start a new fake tensor propagation from scratch, you bump the epoch so that I clear all the memos.
* **torch/_inductor/scheduler.py** - I notice in unit tests that V.current_node is not always set when we call process_kernel. So I save it into the IR node and restore it when we are running `get_estimated_runtime`.
* **torch/fx/experimental/symbolic_shapes.py** - A few things
* **rebind_unbacked** (re **_tensor_version**). Ordinarily, when you have an unbacked SymInt, you persistently hvae it all the way to the end of the program. `_tensor_version` violates this: this generates an unbacked SymInt (for reasons I don't quite understand?) and then gets rid of it later. This triggered an assert violation. I think this op is kind of misusing unbacked SymInt, but I didn't know how to refactor it, so it gets a special case.
* **rebind_unbacked** (re **Simplify SymBool binding**). Ugh, SymBool, what a pain in the butt. I have an assert that you can only rebind unbacked symbol to another unbacked symbol. This assert fails when a boolean is involved, because the result of running keypath on the result is not `u1`, it's `sympy.Piecewise(... sympy.Eq(u1, 1) ...)`. This is actually just `u1`, but Sympy doesn't know it because it doesn't know that `u1` value range is `[0, 1]`. So we manually implement the simplification needed to get the assert to pass.
* **compute_unbacked_bindings** (re **This is pretty fragile**). There is a really funny disaster involving memoization and Inductor process kernel. Ordinarily when I retrace, if there was a memo hit in the old trace, there will be a memo hit in the new trace. However, Inductor process kernel breaks this, because it recreates fake tensor inputs to the operator call from scratch (since they might have different strides), and obviously these tensor inputs don't have the memo from the old one. I tried a little bit to try to manually transplant the memo to the new fake tensor but it seemed hopeless, so I just let the fresh symbol ride, allocating a new unbacked symbol. However, in one of our tests, we rely on knowing that the first nonzero call is equal to the second (memoized) nonzero call. The equality test looked pretty easy to discharge, so I just went ahead and added a deferred runtime assert to this effect and it worked.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/124394
Approved by: https://github.com/jansel
ghstack dependencies: #124310, #124314, #124316
This is a partial revert of https://github.com/pytorch/pytorch/pull/124059
Like in #124297, profiling has revealed that testing equality on *every* output is kind of expensive. So we only test equality when we know there is an unbacked binding. This is the same playbook as the previous PR, just on FakeTensorProp instead of PropagateUnbackedSymInts. Note that we also need to populate `unbacked_bindings` in proxy_tensor.py, since we're generating an entirely new graph in that case.
We now have enough propagation that we're able to trigger a bug related to divisibility replacement. In https://github.com/pytorch/pytorch/pull/113165 we allowed to replace `u0` with `u1 * c` for some constant c, when we have determined that u0 is divisible by c. However, where does the binding for u1 come from? What we will have in practice is that there is some node that is supposed to have bound u1, but which actually is getting a `u1 * c` in its output. So, to get u1, we must divide out c. Fortunately, under the divisibility condition, this is always possible (but remember, we must test divisibility at runtime!)
Because we have tightened up asserts, it is now an error to allocate unbacked SymInts and then fail to track them under unbacked_bindings. In torch/_dynamo/eval_frame.py and torch/_functorch/_aot_autograd/collect_metadata_analysis.py there are examples of benign cases where we repropagated fake tensors but then immediately threw away the results. In these cases, it's not appropriate to rebind, since we're still using the old FX graph that has all of the old symbols. So we just manually clear it. It is possible that other cases will need to be updated, so this PR is "risky" from the perspective of hitting fbcode.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/124310
Approved by: https://github.com/lezcano
