[BugFix][TOPI] Fix resize accuracy issue with non-floor rounding

[tqchen]

Summary

The int_div optimization in topi.image.resize was applied unconditionally
for nearest_neighbor + asymmetric mode, regardless of rounding method.
This caused accuracy issues when rounding_method is not "floor" (e.g.,
"round", "round_prefer_ceil"), because integer division truncates toward
zero rather than rounding.

Fix: Gate the int_div optimization on rounding_method == "floor" or
rounding_method == "" (the default, which gets resolved to "floor" for
non-align_corners modes).

• Updates _resize_2d in python/tvm/topi/image/resize.py
• Updates reference implementation in python/tvm/topi/testing/resize_python.py
• Updates legalize test expected output to reflect the new behavior

[gemini-code-assist]

Summary of Changes

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This pull request reintroduces a fix for resize operations within TOPI, specifically enhancing the nearest neighbor interpolation method. It introduces a new rounding_method parameter across several resize functions, allowing users to specify different rounding behaviors for index calculations. This change provides more granular control over how pixels are mapped during resizing, addressing potential inaccuracies and improving the flexibility of the resize implementation.

Highlights

• Enhanced Nearest Neighbor Rounding: Introduced a rounding_method parameter to control how indices are rounded during nearest neighbor interpolation, allowing for more precise control over resizing behavior.
• Flexible Rounding Strategies: Implemented various rounding strategies within the get_index function, including 'floor', 'round', 'round_prefer_floor', 'round_prefer_ceil', and 'ceil'.
• Conditional Integer Division Conversion: Updated the can_convert_multiply_to_intdiv logic to conditionally apply integer division based on the specified rounding_method for 'asymmetric' nearest neighbor resizing.

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Changelog

• python/tvm/topi/image/resize.py
  • Applied conditional logic for can_convert_multiply_to_intdiv based on the rounding_method when method is 'nearest_neighbor' and coordinate_transformation_mode is 'asymmetric'.
• python/tvm/topi/testing/resize_python.py
  • Modified get_index to accept a rounding_method parameter and implemented a dispatch mechanism for different rounding strategies (floor, round, round_prefer_floor, round_prefer_ceil, ceil).
  • Updated resize3d_nearest, resize3d_ncdhw, resize1d_python, resize2d_python, and resize3d_python to propagate the new rounding_method parameter.

Activity

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[gemini-code-assist]

Code Review

This pull request relands a fix for image resizing, specifically addressing rounding methods for nearest neighbor scaling. The changes introduce a rounding_method parameter across various resize functions and their testing counterparts. The core logic is updated in get_index in the test utilities and a corresponding optimization constraint is added in _resize_2d. The changes appear correct and improve consistency. I have one suggestion to improve code clarity in the test implementation.

[MasterJH5574]

LGTM.