Partially addresses https://github.com/pytorch/pytorch/issues/128150
When you have big sums of values, we end up computing long chains of
binary addition in our FX graph representation. Not only is this ugly,
it also is quadratic, as the sympy.Add constructor is O(N) in number
of arguments. Instead, ensure that we maintain the summation as a
single FX node so we can do the entire addition all in one go.
update_hint_regression benchmark, before and after:
```
update_hint_regression,compile_time_instruction_count,2648328980
update_hint_regression,compile_time_instruction_count,2563748678
```
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/136429
Approved by: https://github.com/isuruf
Fixes#135432
In the current implementation, if we try to store a symbolic number in Tensor's constructor, it assumes that the tensor's dtype and the symbolic number's type are matched, which is not the case.
In other words, if we try to store a `SymInt`, current implementation assumes tensor's dtype is `torch.int32`, `torch.int64` or something. And if we try to store a `SymFloat`, it assumes tensor's dtype is `torch.float32` or `torch.float64`. However, the tensor's dtype could also be `torch.float32` or something else when we try to store `SymInt`, which would be wrong.
This PR stores symbolic numbers by tensor's scalar type by wrapping `SymInt` and `SymFoat`'s guarded number into a PyObject.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/135433
Approved by: https://github.com/ezyang
There is one huge problem this fixes: today, sympify(symint)
produces a float(!!) because Sympy attempts to see if you can
coerce the symint to float in sympify and of course this works on
SymInt.
However, this also has another nontrivial effect: anywhere in Inductor
where sympy expressions are passed around, it is also valid to pass
around a SymInt now. I'm ambivalent about this: it's currently a
mistake to be passing around a SymInt when a sympy expression is
expected. But maybe this is fine?
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/130166
Approved by: https://github.com/yf225
In a previous life, we used sympy.oo to represent the lower/upper bounds of integer ranges. Later, we changed this to be sys.maxsize - 1 for a few reasons: (1) sometimes we do tests on a value being exactly sys.maxsize, and we wanted to avoid a data dependent guard in this case, (2) sympy.oo corresponds to floating point infinity, so you get incorrect types for value ranges with oo, and (3) you can do slightly better reasoning if you assume that input sizes fall within representable 64-bit integer range.
After working in the sys.maxsize regime for a bit, I've concluded that this was actually a bad idea. Specifically, the problem is that you end up with sys.maxsize in your upper bound, and then whenever you do any sort of size-increasing computation like size * 2, you end up with 2 * sys.maxsize, and you end up doing a ton of arbitrary precision int computation that is totally unnecessary. A symbolic bound is better.
But especially after #126905, we can't go back to using sympy.oo, because that advertises that it's not an integer, and now your ValueRanges is typed incorrectly. So what do we do? We define a new numeric constant `int_oo`, which is like `sympy.oo` but it advertises `is_integer`. **test/test_sympy_utils.py** describes some basic properties of the number, and **torch/utils/_sympy/numbers.py** has the actual implementation.
The rest of the changes of the PR are working out the implications of this change. I'll give more commentary as inline comments.
Fixes https://github.com/pytorch/pytorch/issues/127396
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127693
Approved by: https://github.com/lezcano
ghstack dependencies: #126905
In a previous life, we used sympy.oo to represent the lower/upper bounds of integer ranges. Later, we changed this to be sys.maxsize - 1 for a few reasons: (1) sometimes we do tests on a value being exactly sys.maxsize, and we wanted to avoid a data dependent guard in this case, (2) sympy.oo corresponds to floating point infinity, so you get incorrect types for value ranges with oo, and (3) you can do slightly better reasoning if you assume that input sizes fall within representable 64-bit integer range.
After working in the sys.maxsize regime for a bit, I've concluded that this was actually a bad idea. Specifically, the problem is that you end up with sys.maxsize in your upper bound, and then whenever you do any sort of size-increasing computation like size * 2, you end up with 2 * sys.maxsize, and you end up doing a ton of arbitrary precision int computation that is totally unnecessary. A symbolic bound is better.
But especially after #126905, we can't go back to using sympy.oo, because that advertises that it's not an integer, and now your ValueRanges is typed incorrectly. So what do we do? We define a new numeric constant `int_oo`, which is like `sympy.oo` but it advertises `is_integer`. **test/test_sympy_utils.py** describes some basic properties of the number, and **torch/utils/_sympy/numbers.py** has the actual implementation.
The rest of the changes of the PR are working out the implications of this change. I'll give more commentary as inline comments.
Fixes https://github.com/pytorch/pytorch/issues/127396
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127693
Approved by: https://github.com/lezcano
ghstack dependencies: #126905
At a high level, the idea behind this PR is:
* Make it clearer what the promotion and int/float rules for various Sympy operations are. Operators that previously were polymorphic over int/float are now split into separate operators for clarity. We never do mixed int/float addition/multiplication etc in sympy, instead, we always promote to the appropriate operator. (However, equality is currently not done correctly.)
* Enforce strict typing on ValueRanges: if you have a ValueRange for a float, the lower and upper MUST be floats, and so forth for integers.
The story begins in **torch/utils/_sympy/functions.py**. Here, I make some changes to how we represent certain operations in sympy expressions:
* FloorDiv now only supports integer inputs; to do float floor division, do a truediv and then a trunc. Additionally, we remove the divide out addition by gcd optimization, because sympy gcd is over fields and is willing to generate rationals (but rationals are bad for ValueRange strict typing).
* ModularIndexing, LShift, RShift now assert they are given integer inputs.
* Mod only supports integer inputs; eventually we will support FloatMod (left for later work, when we build out Sympy support for floating operations). Unfortunately, I couldn't assert integer inputs here, because of a bad interaction with sympy's inequality solver that is used by the offline solver
* TrueDiv is split into FloatTrueDiv and IntTrueDiv. This allows for us to eventually generate accurate code for Python semantics IntTrueDiv, which is written in a special way to preserve precision when the inputs are >= 2**53 beyond what first coercing the integer to floats and then doing true division.
* Trunc is split to TruncToFloat and TruncToInt.
* Round is updated to return a float, not an int, making it consistent with the round op handler in Inductor. To get Python-style conversion to int, we call TruncToInt on the result.
* RoundDecimal updated to consistently only ever return a float
* Add ToFloat for explicit coercion to float (required so we can enforce strict ValueRanges typing)
In **torch/__init__.py**, we modify SymInt and SymFloat to appropriately call into new bindings that route to these refined sympy operations. Also, we modify `torch.sym_min` and `torch.sym_max` to have promotion semantics (if one argument is a float, the return result is always a float), making them inconsistent with builtins.min/max, but possible to do type analysis without runtime information.
We also need to introduce some new op handlers in **torch/_inductor/ops_handler.py**:
* `to_int` for truncation to int64, directly corresponding to TruncToInt; this can be implemented by trunc and dtype, but with a dedicated handler it is more convenient for roundtripping in Sympy
* `int_truediv` for Python-style integer true division, which has higher precision than casting to floats and then running `truediv`
These changes have consequences. First, we need to make some administrative changes:
* Actually wire up these Sympy functions from SymInt/SymFloat in **torch/fx/experimental/sym_node.py**, including the new promotion rules (promote2)
* Add support for new Sympy functions in **torch/utils/_sympy/interp.py**, **torch/utils/_sympy/reference.py**
* In particular, in torch.utils._sympy.reference, we have a strong preference to NOT do nontrivial compute, instead, everything in ops handler should map to a singular sympy function
* TODO: I chose to roundtrip mod back to our Mod function, but I think I'm going to have to deal with the C/Python inconsistency this to fix tests here
* Add printer support for the Sympy functions in **torch/_inductor/codegen/common.py**, **torch/_inductor/codegen/cpp_utils.py**, **torch/_inductor/codegen/triton.py**. `int_truediv` and mixed precision equality is currently not implemented soundly, so we will lose precision in codegen for large values. TODO: The additions here are not exhaustive yet
* Update ValueRanges logic to use new sympy functions in **torch/utils/_sympy/value_ranges.py**. In general, we prefer to use the new Sympy function rather than try to roll things by hand, which is what was done previously for many VR analysis functions.
In **torch/fx/experimental/symbolic_shapes.py** we need to make some symbolic reasoning adjustments:
* Avoid generation of rational subexpressions by removing simplification of `x // y` into `floor(x / y)`. This simplification then triggers an addition simplification rule `(x + y) / c --> x / c + y / c` which is bad because x / c is a rational number now
* `_assert_bound_is_rational` is no more, we no longer generate rational bounds
* Don't intersect non-int value ranges with the `int_range`
* Support more sympy Functions for guard SYMPY_INTERP
* Assert the type of value range is consistent with the variable type
The new asserts uncovered necessary bug fixes:
* **torch/_inductor/codegen/cpp.py**, **torch/_inductor/select_algorithm.py**, **torch/_inductor/sizevars.py** - Ensure Wild/Symbol manually allocated in Inductor is marked `is_integer` so it's accepted to build expressions
* **torch/_inductor/utils.py** - make sure you actually pass in sympy.Expr to these functions
* **torch/_inductor/ir.py** - make_contiguous_strides_for takes int/SymInt, not sympy.Expr!
* **torch/export/dynamic_shapes.py** - don't use infinity to represent int ranges, instead use sys.maxsize - 1
Because of the removal of some symbolic reasoning that produced rationals, some of our symbolic reasoning has gotten worse and we are unable to simplify some guards. Check the TODO at **test/test_proxy_tensor.py**
**Reland notes.** This requires this internal fbcode diff https://www.internalfb.com/phabricator/paste/view/P1403322587 but I cannot prepare the diff codev due to https://fb.workplace.com/groups/osssupport/posts/26343544518600814/
It also requires this Executorch PR https://github.com/pytorch/executorch/pull/3911 but the ET PR can be landed prior to this landing.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126905
Approved by: https://github.com/xadupre, https://github.com/lezcano
At a high level, the idea behind this PR is:
* Make it clearer what the promotion and int/float rules for various Sympy operations are. Operators that previously were polymorphic over int/float are now split into separate operators for clarity. We never do mixed int/float addition/multiplication etc in sympy, instead, we always promote to the appropriate operator. (However, equality is currently not done correctly.)
* Enforce strict typing on ValueRanges: if you have a ValueRange for a float, the lower and upper MUST be floats, and so forth for integers.
The story begins in **torch/utils/_sympy/functions.py**. Here, I make some changes to how we represent certain operations in sympy expressions:
* FloorDiv now only supports integer inputs; to do float floor division, do a truediv and then a trunc. Additionally, we remove the divide out addition by gcd optimization, because sympy gcd is over fields and is willing to generate rationals (but rationals are bad for ValueRange strict typing).
* ModularIndexing, LShift, RShift now assert they are given integer inputs.
* Mod only supports integer inputs; eventually we will support FloatMod (left for later work, when we build out Sympy support for floating operations). Unfortunately, I couldn't assert integer inputs here, because of a bad interaction with sympy's inequality solver that is used by the offline solver
* TrueDiv is split into FloatTrueDiv and IntTrueDiv. This allows for us to eventually generate accurate code for Python semantics IntTrueDiv, which is written in a special way to preserve precision when the inputs are >= 2**53 beyond what first coercing the integer to floats and then doing true division.
* Trunc is split to TruncToFloat and TruncToInt.
* Round is updated to return a float, not an int, making it consistent with the round op handler in Inductor. To get Python-style conversion to int, we call TruncToInt on the result.
* RoundDecimal updated to consistently only ever return a float
* Add ToFloat for explicit coercion to float (required so we can enforce strict ValueRanges typing)
In **torch/__init__.py**, we modify SymInt and SymFloat to appropriately call into new bindings that route to these refined sympy operations. Also, we modify `torch.sym_min` and `torch.sym_max` to have promotion semantics (if one argument is a float, the return result is always a float), making them inconsistent with builtins.min/max, but possible to do type analysis without runtime information.
We also need to introduce some new op handlers in **torch/_inductor/ops_handler.py**:
* `to_int` for truncation to int64, directly corresponding to TruncToInt; this can be implemented by trunc and dtype, but with a dedicated handler it is more convenient for roundtripping in Sympy
* `int_truediv` for Python-style integer true division, which has higher precision than casting to floats and then running `truediv`
These changes have consequences. First, we need to make some administrative changes:
* Actually wire up these Sympy functions from SymInt/SymFloat in **torch/fx/experimental/sym_node.py**, including the new promotion rules (promote2)
* Add support for new Sympy functions in **torch/utils/_sympy/interp.py**, **torch/utils/_sympy/reference.py**
* In particular, in torch.utils._sympy.reference, we have a strong preference to NOT do nontrivial compute, instead, everything in ops handler should map to a singular sympy function
* TODO: I chose to roundtrip mod back to our Mod function, but I think I'm going to have to deal with the C/Python inconsistency this to fix tests here
* Add printer support for the Sympy functions in **torch/_inductor/codegen/common.py**, **torch/_inductor/codegen/cpp_utils.py**, **torch/_inductor/codegen/triton.py**. `int_truediv` and mixed precision equality is currently not implemented soundly, so we will lose precision in codegen for large values. TODO: The additions here are not exhaustive yet
* Update ValueRanges logic to use new sympy functions in **torch/utils/_sympy/value_ranges.py**. In general, we prefer to use the new Sympy function rather than try to roll things by hand, which is what was done previously for many VR analysis functions.
In **torch/fx/experimental/symbolic_shapes.py** we need to make some symbolic reasoning adjustments:
* Avoid generation of rational subexpressions by removing simplification of `x // y` into `floor(x / y)`. This simplification then triggers an addition simplification rule `(x + y) / c --> x / c + y / c` which is bad because x / c is a rational number now
* `_assert_bound_is_rational` is no more, we no longer generate rational bounds
* Don't intersect non-int value ranges with the `int_range`
* Support more sympy Functions for guard SYMPY_INTERP
* Assert the type of value range is consistent with the variable type
The new asserts uncovered necessary bug fixes:
* **torch/_inductor/codegen/cpp.py**, **torch/_inductor/select_algorithm.py**, **torch/_inductor/sizevars.py** - Ensure Wild/Symbol manually allocated in Inductor is marked `is_integer` so it's accepted to build expressions
* **torch/_inductor/utils.py** - make sure you actually pass in sympy.Expr to these functions
* **torch/_inductor/ir.py** - make_contiguous_strides_for takes int/SymInt, not sympy.Expr!
* **torch/export/dynamic_shapes.py** - don't use infinity to represent int ranges, instead use sys.maxsize - 1
Because of the removal of some symbolic reasoning that produced rationals, some of our symbolic reasoning has gotten worse and we are unable to simplify some guards. Check the TODO at **test/test_proxy_tensor.py**
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126905
Approved by: https://github.com/xadupre, https://github.com/lezcano
At a high level, the idea behind this PR is:
* Make it clearer what the promotion and int/float rules for various Sympy operations are. Operators that previously were polymorphic over int/float are now split into separate operators for clarity. We never do mixed int/float addition/multiplication etc in sympy, instead, we always promote to the appropriate operator. (However, equality is currently not done correctly.)
* Enforce strict typing on ValueRanges: if you have a ValueRange for a float, the lower and upper MUST be floats, and so forth for integers.
The story begins in **torch/utils/_sympy/functions.py**. Here, I make some changes to how we represent certain operations in sympy expressions:
* FloorDiv now only supports integer inputs; to do float floor division, do a truediv and then a trunc. Additionally, we remove the divide out addition by gcd optimization, because sympy gcd is over fields and is willing to generate rationals (but rationals are bad for ValueRange strict typing).
* ModularIndexing, LShift, RShift now assert they are given integer inputs.
* Mod only supports integer inputs; eventually we will support FloatMod (left for later work, when we build out Sympy support for floating operations). Unfortunately, I couldn't assert integer inputs here, because of a bad interaction with sympy's inequality solver that is used by the offline solver
* TrueDiv is split into FloatTrueDiv and IntTrueDiv. This allows for us to eventually generate accurate code for Python semantics IntTrueDiv, which is written in a special way to preserve precision when the inputs are >= 2**53 beyond what first coercing the integer to floats and then doing true division.
* Trunc is split to TruncToFloat and TruncToInt.
* Round is updated to return a float, not an int, making it consistent with the round op handler in Inductor. To get Python-style conversion to int, we call TruncToInt on the result.
* RoundDecimal updated to consistently only ever return a float
* Add ToFloat for explicit coercion to float (required so we can enforce strict ValueRanges typing)
In **torch/__init__.py**, we modify SymInt and SymFloat to appropriately call into new bindings that route to these refined sympy operations. Also, we modify `torch.sym_min` and `torch.sym_max` to have promotion semantics (if one argument is a float, the return result is always a float), making them inconsistent with builtins.min/max, but possible to do type analysis without runtime information.
We also need to introduce some new op handlers in **torch/_inductor/ops_handler.py**:
* `to_int` for truncation to int64, directly corresponding to TruncToInt; this can be implemented by trunc and dtype, but with a dedicated handler it is more convenient for roundtripping in Sympy
* `int_truediv` for Python-style integer true division, which has higher precision than casting to floats and then running `truediv`
These changes have consequences. First, we need to make some administrative changes:
* Actually wire up these Sympy functions from SymInt/SymFloat in **torch/fx/experimental/sym_node.py**, including the new promotion rules (promote2)
* Add support for new Sympy functions in **torch/utils/_sympy/interp.py**, **torch/utils/_sympy/reference.py**
* In particular, in torch.utils._sympy.reference, we have a strong preference to NOT do nontrivial compute, instead, everything in ops handler should map to a singular sympy function
* TODO: I chose to roundtrip mod back to our Mod function, but I think I'm going to have to deal with the C/Python inconsistency this to fix tests here
* Add printer support for the Sympy functions in **torch/_inductor/codegen/common.py**, **torch/_inductor/codegen/cpp_utils.py**, **torch/_inductor/codegen/triton.py**. `int_truediv` and mixed precision equality is currently not implemented soundly, so we will lose precision in codegen for large values. TODO: The additions here are not exhaustive yet
* Update ValueRanges logic to use new sympy functions in **torch/utils/_sympy/value_ranges.py**. In general, we prefer to use the new Sympy function rather than try to roll things by hand, which is what was done previously for many VR analysis functions.
In **torch/fx/experimental/symbolic_shapes.py** we need to make some symbolic reasoning adjustments:
* Avoid generation of rational subexpressions by removing simplification of `x // y` into `floor(x / y)`. This simplification then triggers an addition simplification rule `(x + y) / c --> x / c + y / c` which is bad because x / c is a rational number now
* `_assert_bound_is_rational` is no more, we no longer generate rational bounds
* Don't intersect non-int value ranges with the `int_range`
* Support more sympy Functions for guard SYMPY_INTERP
* Assert the type of value range is consistent with the variable type
The new asserts uncovered necessary bug fixes:
* **torch/_inductor/codegen/cpp.py**, **torch/_inductor/select_algorithm.py**, **torch/_inductor/sizevars.py** - Ensure Wild/Symbol manually allocated in Inductor is marked `is_integer` so it's accepted to build expressions
* **torch/_inductor/utils.py** - make sure you actually pass in sympy.Expr to these functions
* **torch/_inductor/ir.py** - make_contiguous_strides_for takes int/SymInt, not sympy.Expr!
* **torch/export/dynamic_shapes.py** - don't use infinity to represent int ranges, instead use sys.maxsize - 1
Because of the removal of some symbolic reasoning that produced rationals, some of our symbolic reasoning has gotten worse and we are unable to simplify some guards. Check the TODO at **test/test_proxy_tensor.py**
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/126905
Approved by: https://github.com/xadupre, https://github.com/lezcano
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 `usort` config in `pyproject.toml` has no effect due to a typo. Fixing the typo make `usort` do more and generate the changes in the PR. Except `pyproject.toml`, all changes are generated by `lintrunner -a --take UFMT --all-files`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127126
Approved by: https://github.com/kit1980
The `usort` config in `pyproject.toml` has no effect due to a typo. Fixing the typo make `usort` do more and generate the changes in the PR. Except `pyproject.toml`, all changes are generated by `lintrunner -a --take UFMT --all-files`.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/127126
Approved by: https://github.com/kit1980
ghstack dependencies: #127122, #127123, #127124, #127125
A common complaint when working with data-dependent code in PyTorch is that it's hard to tell how far you are from the finish line: every time a GuardOnDataDependentSymNode error is hit, you have to somehow fix or workaround it to see the next one.
This PR adds a new mode `torch._functorch.config.fake_tensor_propagate_real_tensors` which modifies fake tensors to also propagate real tensors. This means that when we try to guard on a data-dependent SymNode, we can actually produce a real result. We also produce a warning which you should consult to figure out what the crux points are.
I ran this on vision_maskrcnn. In the baseline (without this mode), the model has 27 graph breaks, resulting in 40 graphs. With this mode on, the model has only 11 graph breaks, resulting in 15 graphs (the remaining graph breaks are due to missing functionality for item() on float tensor and some other Dynamo missing features.) You get a list of things that would have errored like this:
```
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u1) < 2) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u1), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u1), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Ne(Max(1, u1), 1)) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u0) < 2) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u0), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u0), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Ne(Max(1, u0), 1)) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u1) < 2) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u1), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u1), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Ne(Max(1, u1), 1)) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u0) < 2) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u0), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u0), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Ne(Max(1, u0), 1)) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u1) < 2) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u1), 1)) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Ne(Max(1, u1), 1)) -> True
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Max(1, u0) < 2) -> False
WARNING:torch.fx.experimental.symbolic_shapes:propagate_real_tensors evaluate_expr(Eq(Max(1, u0), 1)) -> False
```
Potential later follow ups:
* Improve the warning messages (in particular, should provide user frames)
* GC real tensors when they are no longer needed by tracing. Right now, this will use A LOT of memory, equal to as if your GC was broken and every intermediate tensor was kept live
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/125115
Approved by: https://github.com/IvanKobzarev
**Motivation**: There's a Meta-internal use case that deepcopies a bunch of metadata, which includes shapes. When we try to use NestedTensor with this tool, it errors out when we try to deepcopy the metadata, because SymNodes cannot be deepcopied. The change here is to add an implementation of `__deepcopy__`.
**Implementation**:
1. `__deepcopy__` on SymNode calls clone()
2. Implement `clone()` in NestedIntSymNode, which previously didn't have this implemented
**Potential Issues**:
Right now, this works.
But, regarding (2): Eventually we'll have some mapping between the NestedSymIntNode and its corresponding offsets/lengths tensor (cc @soulitzer who is working on this). How should this work with `__deepcopy__`? Should the offsets/lengths tensor also be cloned, or should the new symint reference the same offsets as the old symint?
On one hand, we already have this issue with NestedIntSymNodeImpl::mul(): mul() creates a new NestedIntSymNodeImpl. On the other hand, `__deepcopy__` might imply different semantics.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121361
Approved by: https://github.com/soulitzer
Fixes https://github.com/pytorch/pytorch/issues/123854
Important comment:
```
# Never replace unbacked symbols with other unbacked symbols.
# This is error prone because you can cause references to
# unbacked symbols to time travel backwards. E.g.,
#
# u1 = x.item()
# ... use of u1 ...
# u2 = y.item()
# u3 = z.item()
# torch._check(u1 == u2 + u3)
#
# If you replace u1 with u2 + u3, then the use of u1 now
# references u2 and u3 prior to them actually being bound at
# runtime. It's pretty inconvenient to setup control
# dependencies for substitutions, so ban it entirely.
```
This is kind of risky for the internal MRS workstream, because we added these substitutions upon their request in the first place. Fortunately, we still allow substitutions to backed SymInts and constants, and I believe that is what is actually load bearing.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/124316
Approved by: https://github.com/ColinPeppler, https://github.com/lezcano
ghstack dependencies: #124310, #124314
Sympy simplifications don't obey floating point semantics, so don't
use Sympy for this. Keep them as is, only evaluate with the reference
implementations when all arguments are known.
This may end up getting subsumed by some other changes later, but I
wanted to understand if this was easy and it seems to be easy.
This doesn't actually depend on the earlier diffs on the stack and I can detach it.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/122823
Approved by: https://github.com/lezcano
Previously, when we applied a replacement, a SymInt that was
previously an unbacked SymInt would then transmute into whatever
we replaced it into (e.g., a constant).
This has a major downside: we often look at SymInts associated with
FX nodes (e.g., the meta of x.item() return) to find out where the
unbacked SymInt was allocated. If we replace it, we no longer can
find out where, e.g., u1 was allocated! But we need to know this
so we can generate deferred runtime asserts like u1 == s0.
To solve this problem, I have a special mode for replace, resolve_unbacked=False, which lets you disable substitutions on unbacked SymInts. When reporting node.expr, we preferentially avoid applying unbacked SymInt substitutions. To understand if we might accidentally reapply the substitution later, before we have reached the deferred runtime assert, we must study the calls to simplify() in ShapeEnv. My audit turns up these sites:
* `produce_guards`: this is fine, deferred runtime asserts never show up here, we must NOT have unbacked SymInts show up here. Similarly `get_nontrivial_guards`.
* `_maybe_evaluate_static`: this is fine, we are using this to determine if it is necessary to produce a guard/runtime assert. We don't want to reissue a runtime assert if we've already asserted on it, and replacements can help us understand if this has occurred.
* `_simplify_floor_div`: this is a legitimate bug, it needs to be `resolve_unbacked=False`
* `_refine_ranges`: this is fine, a refined range doesn't affect what runtime asserts we issue
* `_update_divisible`: this updates the `self.divisible` set, which specifies when we can simplify away divisibility constraints. Since this affects replacements only, it won't cause us to oversimplify a user provided expression.
There are some situations where we DO want to always apply the substitution, specifically when we have the duplicate symbol problem (we retrace an item call and get u0 and u1 which refer to the same thing.) I don't want two symbols in this case, so a special `rename_unbacked_to` is provided which sets up the unconditional renaming.
Along the way, I make a refinement to `_update_var_to_range`: if you update a var range for a size-like unbacked SymInt, you are now no longer allowed to set its lower bound below 2. This is because if you could, then our size oblivious tests for it would be inconsistent. Actually, I think there is still some inconsistency, because if you assert `u0 == 0` we will still end up with this in deferred runtime asserts, and we will then use this to simplify these statements to be True everywhere else. Maybe we should forbid this kind of refinement; not done in this PR.
Fixes https://github.com/pytorch/pytorch/issues/119689
Fixes https://github.com/pytorch/pytorch/issues/118385
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120816
Approved by: https://github.com/lezcano
Context: view fake-ification should handle closed-over state in ViewFuncs for use in view replay by:
* fake-ifying tensors
* symbolicizing SymInts
This avoids invalid specialization during view replay. However, the symbols / tensors created as intermediates in the view chain should not stick around or be guarded on. This PR introduces an `EphemeralSource` intended to be used as a source for this purpose. It has the following properties:
* Considered first to be simplified out in symbol simplification logic
* Errors if guarded on
Differential Revision: [D54561597](https://our.internmc.facebook.com/intern/diff/D54561597)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120948
Approved by: https://github.com/ezyang
This is basically done the obvious way. For better or worse, I jammed this into what used to be `_maybe_guard_eq` but now is `_maybe_guard_rel`. I was careful to test all the off by one conditions, and each permutation. Let me know if you think I missed anything. Importantly, this now works for unbacked SymInts.
While testing, I noticed we are silently duck sizing all symbolic variables in `test_dynamic_shapes.py`. This may or may not be covering up bugs.
Along the way, I had to fix a bug in export constraints, where we weren't checking that the final var_to_range was consistent with what the user requested at top level.
After I implemented all this, I realized that applying this to non-unbacked SymInts was duplicative with @ysiraichi's previous work on https://github.com/pytorch/pytorch/pull/97963 . The upside is I now understand what Yukio was trying to do in the original PR, and I think my new logic is simpler and less error prone. In Yukio's earlier diff, Yukio tried very hard to avoid changing what guards we actually issue (since this would cause tests to wobble). Thus, when he refined a range, he also saved the guard that actually caused the range to refine. In this PR, I don't bother saving these guards; instead I just tighten var_to_range directly and rely on generating guards on this to be correct. The key insight is that if I assert `x < y`, it's always safe to emit (potentially) more restrictive range guards, because this won't invalidate our guards, it will just make them a little too strong (but actually, I think we are precise along the way.) If these guards make it unnecessary to test `x < y`, because now the ranges for x and y are disjoint, this is fine, we've subsumed the x < y guard and can just not bother testing it. If I've gotten it right, TV will agree with me.
In fact, I had a bug in this PR which TV didn't catch, which is that when we have a recorded var_to_guards for a symbol, we unconditionally never generate the range guard for it, even if the var_to_guards is potentially inconsistent with var_to_range (because var_to_range was updated separately). With var_to_guards removed, I don't have to worry abou this inconsistency.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/120800
Approved by: https://github.com/Skylion007, https://github.com/avikchaudhuri, https://github.com/ysiraichi
Fixes https://github.com/pytorch/pytorch/issues/117268; check this issue for background.
This PR does the following:
* Do not perform a replacement if the expression we're replacing the symbol with has a less refined value range than the original. There's a little bit of trickiness around the handling for values close to INT64_MAX; when checking if a range refines another, I *only* consider the range representable in 64-bit integers. This is enough to prevent us from doing a substitution like `i0 = 10 - i1`, but it appears to still let us do the other substitutions we like, such as `i0 = i1` or `i0 = 12 * i1`
* The test above is order dependent: if we assert an equality BEFORE we have refined a range, we might be willing to do the replacement because there isn't a meaningful range. This means that it's important to mark things as sizes, before you start doing other error checking. `split_with_sizes` is adjusted accordingly. It would be good to raise an error if you get the ordering wrong, but I leave this to future work.
* It turns out this is not enough to fix AOTAutograd, because we lose the size-ness of unbacked SymInts when AOTAutograd retraces the Dynamo graph. So update deferred runtime assert insertion to also insert size-ness and value ranges annotations. Note that, in principle, it shouldn't be necessary to explicitly do the latter; these should just show up as deferred runtime asserts. That's some extra refactoring for a later day.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/117356
Approved by: https://github.com/lezcano
Fixes https://github.com/pytorch/pytorch/issues/117268; check this issue for background.
This PR does the following:
* Do not perform a replacement if the expression we're replacing the symbol with has a less refined value range than the original. There's a little bit of trickiness around the handling for values close to INT64_MAX; when checking if a range refines another, I *only* consider the range representable in 64-bit integers. This is enough to prevent us from doing a substitution like `i0 = 10 - i1`, but it appears to still let us do the other substitutions we like, such as `i0 = i1` or `i0 = 12 * i1`
* The test above is order dependent: if we assert an equality BEFORE we have refined a range, we might be willing to do the replacement because there isn't a meaningful range. This means that it's important to mark things as sizes, before you start doing other error checking. `split_with_sizes` is adjusted accordingly. It would be good to raise an error if you get the ordering wrong, but I leave this to future work.
* It turns out this is not enough to fix AOTAutograd, because we lose the size-ness of unbacked SymInts when AOTAutograd retraces the Dynamo graph. So update deferred runtime assert insertion to also insert size-ness and value ranges annotations. Note that, in principle, it shouldn't be necessary to explicitly do the latter; these should just show up as deferred runtime asserts. That's some extra refactoring for a later day.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/117356
Approved by: https://github.com/lezcano
