Introduce int_oo (#127693) (#3936)

Summary:

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 pytorch/pytorch#127396

Signed-off-by: Edward Z. Yang <ezyang@meta.com>

X-link: pytorch/pytorch#127693
Approved by: https://github.com/lezcano
ghstack dependencies: #126905

bypass-github-export-checks pushed new commits to forward fix error

Test Plan: contbuild & OSS CI, see https://hud.pytorch.org/commit/pytorch/pytorch/9cab5987bdeb66df8efbc581b3469bfe300e168c

Differential Revision: D58394154

Pulled By: clee2000

.ci/docker/ci_commit_pins/pytorch.txt

@@ -1 +1 @@
-48b6c8dbc376db4406a979b35cd6909bcb428931
+70a1e8571802c22c0f09279b77876e6e85c81325

exir/sym_util.py

@@ -9,6 +9,7 @@
 import sympy
 
 import torch
+from torch.utils._sympy.numbers import int_oo
 from torch.utils._sympy.value_ranges import bound_sympy, ValueRanges
 
 
@@ -47,8 +48,8 @@ def eval_upper_bound(maybe_symint: Union[int, torch.SymInt]) -> Optional[int]:
             concrete_upper, int
         ), f"Expect upper bound to be a concrete int but got {concrete_upper}"
         return concrete_upper
-    elif isinstance(upper_bound, sympy.oo):
-        return None
+    elif upper_bound in (sympy.oo, int_oo):
+        return int_oo
     else:
         raise RuntimeError(
             f"Expect upper bound to be sympy.Integer or sympy.oo. but got {upper_bound}"

install_requirements.sh

@@ -59,7 +59,7 @@ done
 # NOTE: If a newly-fetched version of the executorch repo changes the value of
 # NIGHTLY_VERSION, you should re-run this script to install the necessary
 # package versions.
-NIGHTLY_VERSION=dev20240507
+NIGHTLY_VERSION=dev20240611
 
 # The pip repository that hosts nightly torch packages.
 TORCH_NIGHTLY_URL="https://download.pytorch.org/whl/nightly/cpu"