mikeseven opened a new pull request #7912:
URL: https://github.com/apache/tvm/pull/7912
Pytorch Conv Transpose Padding Fix
==================================
Background
----------
* we noticed a discrepancy between the output shapes produced by Pytorch
and TVM for a Pytorch network containing a single ``torch.nn.ConvTranspose2d``
operator.
* When comparing the attributes of the ``torch.nn.ConvTranspose2d``
operator and the ``tvm.relay.nn.conv2d_transpose``
operator, the output_padding parameter in
``tvm.relay.nn.conv2d_transpose`` would always default to
0 regardless of what output padding was set in
``torch.nn.ConvTranspose2d``.
* Upon further inspection, it was found that in
``tvm/python/tvm/relay/frontend/pytorch.py``, the import logic for convolution
layers was missing the output_padding parameter.
The Fix
-------
* All fixes were implemented in ``tvm/relay/frontend/pytorch.py``.
* To resolve the missing padding parameter, ``convolution`` method of the
``PyTorchOpConverter`` class is updated so that when it constructed the
relay convolution op it supplied the ``output_padding`` attribute in the cases
where it was creating convolution transpose operations.
* Over the course of the fix I also discovered that the convolution class
automatically converted
``torch.nn.ConvTranspose1D`` operations into
``tvm.relay.nn.conv2d_transpose``. This was fixed so now they were
converted into ``tvm.relay.nn.conv1d_transpose`` operations.
* Over the couse of the fix we also discovered that ``torch.nn.Conv1d``
operations were being converted into
``tvm.relay.nn.conv2d`` operations. This was fixed so that they are now
converted into ``tvm.relay.nn.conv1d``
operations. There is a slight caveat where because tvm does not support
grouped 1D convolution as stated in the
description of ``tvm.relay.nn.conv1d``, in that case we convert the
operation to 2D convolution which does have
support for grouped convolution. After the 2D convolution, we then
squeeze the output to get the correct shape and
values for a grouped 1D convolution.
Test Coverage
-------------
* extended the ``test_forward_conv_transpose`` test in
``tvm/tests/python/frontend/pytorch/test_forward.py``.
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