[BUG] The Pass “eliminate_nop_pad" causes output mismatch

Issue
eliminate_nop_pad (onnxoptimizer 0.4.2) produces numerical differences between the optimized graph and oracle in case_02937_seed43509122. Only output tensors v17_0 (output[12]) and v49_0 (output[17]) differs.

Environment

• Ubuntu 20.04
• Python 3.10
• onnx==1.19.0
• onnxruntime==1.19.2
• onnxoptimizer==0.4.2 (latest)

Repro steps (run from this folder)

1. Download and unzip the attached archive below, then cd into the extracted directory

eliminate_nop_pad_repro.tar.gz

tar -xzvf eliminate_nop_pad_repro.tar.gz
cd eliminate_nop_pad_repro

2. Create a Python 3.10 virtual environment and install dependencies:

python -m venv .venv
source .venv/bin/activate
pip install --upgrade pip
pip install -r requirements.txt

3. Optimize the problematic case with only eliminate_nop_pad:

python optimize_model.py --case case_02937_seed43509122

4. Run the differential test to compare the optimized graph vs the oracle with ORT optimizations disabled:

python diff_test.py --case case_02937_seed43509122

Expected
All outputs should match the reference so diff_test.py prints “All outputs matched exactly.” NaN-laden tensors in other cases may trigger numpy warnings, but those are irrelevant because only case_02937 is being evaluated here, and disabling ORT graph optimizations keeps constant-fold warnings out of the log.

Differential Test Output Details

Case: case_02937_seed43509122
Mismatched outputs (optimized vs reference):
  v17_0 (output[12]): max_abs=1.221e-04, max_rel=7.163e-04, shape=(2, 1, 16, 2)
  v49_0 (output[17]): max_abs=1.221e-04, max_rel=9.747e-04, shape=(44, 1, 16, 46, 2)
Overall: max_abs=1.221e-04, max_rel=9.747e-04

Start by running optimize_model.py and diff_test.py for case_02937_seed43509122 from the extracted reproduction directory. Trace the eliminate_nop_pad pass while comparing outputs v17_0 and v49_0 against the oracle. Done means diff_test.py reports “All outputs matched exactly.”