chore(onnx): Remove dead code in find_scales and add test coverage

[shantoislamdev]

What does this PR do?

Type of change: Dead code cleanup, new tests

Overview: Remove confusing dead code in find_scales function and add test coverage.

The commented-out line # z = -np.round(temp).clip(...) in quant_utils.py represented a buggy implementation due to operator precedence. Python interprets -np.round(temp).clip(...) as -(np.round(temp).clip(...)), which incorrectly produces 0 for negative input ranges. The active code correctly performs negation before clipping.

This PR:

1. Removes the confusing commented-out dead code
2. Adds a parametrized test to verify the zero-point calculation works correctly for various input ranges

Testing

Added test_find_scales_zero_point which tests:

• Negative-only range
• Mixed range (negative to positive)
• Positive-only range
• Symmetric around zero

Before your PR is "Ready for review"

• Make sure you read and follow Contributor guidelines and your commits are signed. ✅
• Is this change backward compatible?: Yes
• Did you write any new necessary tests?: Yes
• Did you add or update any necessary documentation?: No (code cleanup, no API changes)
• Did you update Changelog?: No (minor cleanup, not a feature/bug fix)

Additional Information

Files changed:

• modelopt/onnx/quantization/quant_utils.py: Removed 1 line of dead code
• tests/unit/onnx/test_quant_utils.py: Added test for find_scales

Summary by CodeRabbit

• Chores

  • Removed obsolete comment from quantization utilities code.

• Tests

  • Added test coverage for asymmetric quantization zero-point calculations to validate scale values, shape consistency, and zero-point bounds.

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📝 Walkthrough

Walkthrough

A comment line was removed from the find_scales function in the quantization utility module, and a new test case was added to validate asymmetric quantization zero-point calculations. These changes maintain existing functionality while improving test coverage.

Changes

Cohort / File(s)	Summary
Code Cleanup modelopt/onnx/quantization/quant_utils.py	Removed an unused/outdated comment from the zero-point branch within find_scales. No functional changes to computation logic.
Test Coverage tests/unit/onnx/test_quant_utils.py	Added new test function test_find_scales_zero_point to validate asymmetric quantization behavior, including positive scales, non-None zero-point, shape consistency, and zero-point bounds verification. Updated imports to include find_scales.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: removing dead code (the commented line) from find_scales and adding test coverage for zero-point calculation.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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