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Discrepancy in actual and expected output for subgraph test : batchNormalization options.axis=0 + gelu

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
15/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Active
Tech stack
tensorflow

Research direction

Start from the subgraph conformance test that chains batchNormalization with options.axis=0 into gelu, using the inputs and expected values in the issue. Reproduce the ULP mismatch at index 4 on the CPU backend, then compare against the other backends the reporter tried. The thread asks the working group whether the tolerance or the expected values should change, so there is no code change to make until that decision is recorded. Done means a documented decision on the tolerance, plus either an updated threshold or a fix.

Written by the indexing model from the issue text.

Description

Agenda+ web-platform-tests

Issue

I was running this conformance test for NVIDIA's TensorRT-RTX EP with ORT backend and encountered a failure.

Input:

bnInput     shape [3,1,2] float32 = [-1, 0, 1, 2, 3, 4]
bnMean      shape [3]     float32 = [0, 3, 6]
bnVariance  shape [3]     float32 = [1.0, 1.5, 2.0]

Graph:

batchNormalization(input=bnInput, mean=bnMean, variance=bnVariance, {axis: 0}) -> bnOutput
gelu(bnOutput) -> output

Expected output: shape [3,1,2] float32

[-0.15865567326545715, 0, -0.08366739749908447,
 -0.16910307109355927, -0.03595117852091789, -0.1112278625369072]

Error happens at index 4

actual -0.035951320081949234 should be close enough to expected -0.03595117852091789 by ULP distance: expected <= 24 but got 38

Observations

I tested this with other execution providers in ORT and other backends and encountered similar or same error.

Backend Actual ULP Difference
ORT CPU EP −0.035951320081949234 38
TFLite −0.035951387137174606 56
LiteRT (GPU) −0.035951387137174606 56

Question for the Working Group

  • What is the expected behavior for this test ?
  • Should the discrepancy between the actual and expected outputs be investigated, or is the current error tolerance too strict and in need of adjustment?
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