fix for asymmetric padding

[anirudhacharya]

Description

Fixes asymmetric padding issue in onnx-mxnet translators. MXNet conv operator supports only symmetric padding, whereas the conv operator in ONNX can have asymmetric padding. We are fixing this discrepancy by sequencing MXNet's 'Pad' operator and MXNet's 'Convolution' operator. Because the 'Pad' operator in MXNet supports asymmetric padding.

Checklist

Essentials

Please feel free to remove inapplicable items for your PR.

• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage: The 'Pad' operator has tests for both symmetric and asymmetric padding.
• To the my best knowledge, examples are either not affected by this change, or have been fixed to be compatible with this change

Comments

• @spidydev @anirudh2290 @zheng-da

[rajanksin]

Could you add some comments, why we are doing padding before conv

[rajanksin]

LGTM

[zheng-da]

Is there a unit test to cover this?

[anirudhacharya]

The CI failed in one of the flaky tests while trying to fetch test files -
ProtocolError: ("Connection broken: ConnectionResetError(104, 'Connection reset by peer')", ConnectionResetError(104, 'Connection reset by peer'))
Will rerun the CI.

[anirudh2290]

@marcoabreu I see that tutorials test have been added to the CI. How can I find the timeout set for the tutorials job ?

[anirudhacharya]

@marcoabreu the last two CI runs failed on the following tests -

• test_tutorials.test_onnx_inference_on_onnx_model (tutorial tests Python 3 GPU)
• test_tutorials.test_onnx_fine_tuning_gluon (tutorial tests Python 2 GPU)

both due to "Connection reset". What is the timeout set for these tests? Could you please take a look.

[anirudh2290]

Okay it seems to be set in test_tutorials to 7 mins: https://github.com/apache/incubator-mxnet/blob/master/tests/tutorials/test_tutorials.py#L49

[anirudh2290]

@piiswrong @eric-haibin-lin is this good to merge ?