[ARITH] Fix canonical simplify for LE with incorrect range assumptions #18025
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
tqchen
approved these changes
May 30, 2025
Fix a bug in canonical simplification of less-than expressions where the algorithm incorrectly assumed variables could have negative values when simplifying expressions of the form `ax + b < c`. The previous implementation checked if `-d < xn < d` before simplifying, but this was incorrect when variables are constrained to non-negative ranges. For example, with constraints `0 < x, y < 2` and expression `2x + y < 8`, the algorithm would incorrectly check if `-2 < y < 2` and then simplify to `x < 4`. However, when x=4 and y=-1, we get 2*4 + (-1) = 7 < 8, which satisfies the original constraint but violates the intended variable bounds. The fix changes the range check to `0 <= xn < d`, ensuring that simplification only occurs when variables are properly bounded from below at zero. Co-authored-by: FeiyangChen <[email protected]>
|
@tvm-bot rerun |
ShiboXing
pushed a commit
to ShiboXing/tvm
that referenced
this pull request
Aug 10, 2025
apache#18025) Fix a bug in canonical simplification of less-than expressions where the algorithm incorrectly assumed variables could have negative values when simplifying expressions of the form `ax + b < c`. The previous implementation checked if `-d < xn < d` before simplifying, but this was incorrect when variables are constrained to non-negative ranges. For example, with constraints `0 < x, y < 2` and expression `2x + y < 8`, the algorithm would incorrectly check if `-2 < y < 2` and then simplify to `x < 4`. However, when x=4 and y=-1, we get 2*4 + (-1) = 7 < 8, which satisfies the original constraint but violates the intended variable bounds. The fix changes the range check to `0 <= xn < d`, ensuring that simplification only occurs when variables are properly bounded from below at zero. Co-authored-by: FeiyangChen <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fix a bug in canonical simplification of less-than expressions where the algorithm incorrectly assumed variables could have negative values when simplifying expressions of the form
ax + b < c.The previous implementation checked if
-d < xn < dbefore simplifying, but this was incorrect when variables are constrained to non-negative ranges. For example, with constraints0 < x, y < 2and expression2x + y < 8, the algorithm would incorrectly check if-2 < y < 2and then simplify tox < 4. However, when x=4 and y=-1, we get 2*4 + (-1) = 7 < 8, which satisfies the original constraint but violates the intended variable bounds.The fix changes the range check to
0 <= xn < d, ensuring that simplification only occurs when variables are properly bounded from below at zero.