Temporarily deactivate torch-scatter while we wait for new release
Author: LysandreJik
Pull request: yes

Torch 1.9.0 just landed, incompatible with torch-scatter installed with version 1.8.0. While we wait for torch-scatter binaries compatible with 1.9.0 to be released, deactivating the torch-scatter-based tests.

cc @patrickvonplaten @sgugger @NielsRogge 

Comments:
Requested the binary build:
https://github.com/rusty1s/pytorch_scatter/issues/224


well, you can also change to `torch==1.8.1` and keep everything else the same.

That's a better alternative, let me update.

sorry, I meant `pip install torch==1.8.1` - torch-scatter doesn't have 1.8.1 - it's 1.8.0 but works with either pytorch-1.8.x

https://github.com/rusty1s/pytorch_scatter#pytorch-180

i.e. I suggested that we don't yet switch to pt-1.9.0 until all the dependants catch up.

Ah, thank you for clarifying. We do have quite a bunch of failures on torch 1.9.0 (all related to torch fx it seems):

```
FAILED tests/test_modeling_albert.py::AlbertModelTest::test_torch_fx -   File...
FAILED tests/test_modeling_albert.py::AlbertModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_bert.py::BertModelTest::test_torch_fx -   File "<e...
FAILED tests/test_modeling_bert.py::BertModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_electra.py::ElectraModelTest::test_torch_fx -   Fi...
FAILED tests/test_modeling_electra.py::ElectraModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_distilbert.py::DistilBertModelTest::test_torch_fx
FAILED tests/test_modeling_distilbert.py::DistilBertModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_gpt_neo.py::GPTNeoModelTest::test_torch_fx -   Fil...
FAILED tests/test_modeling_gpt_neo.py::GPTNeoModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_gpt2.py::GPT2ModelTest::test_torch_fx -   File "<e...
FAILED tests/test_modeling_gpt2.py::GPT2ModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_megatron_bert.py::MegatronBertModelTest::test_torch_fx
FAILED tests/test_modeling_megatron_bert.py::MegatronBertModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_mobilebert.py::MobileBertModelTest::test_torch_fx
FAILED tests/test_modeling_mobilebert.py::MobileBertModelTest::test_torch_fx_output_loss
FAILED tests/test_modeling_t5.py::T5ModelTest::test_torch_fx -   File "<eval_...
FAILED tests/test_modeling_t5.py::T5ModelTest::test_torch_fx_output_loss -   ...
```

So agreed to keep the CI on 1.8.1 until we resolve this and can update to 1.9.0. cc @michaelbenayoun 

Yes, the torch fx tests should either be skipped or fixed - @michaelbenayoun already knows about this.

The problem was uncovered with 1.9.0-RC.

He suggested a fix for pytorch instead, but I don't think it made it into 1.9.0

Merging since this seems all good I and would really like a green CI :-)

@LysandreJik, https://pytorch-geometric.com/whl/torch-1.9.0+cu111.html is ready.

One way to proceed is to wait for @michaelbenayoun - or skip those tests for now and swtich to `torch==1.9.0` while updating `torch-scatter` to the link above.

Also trying to ask for pytorch-core support to support "sum", "mean", "max" or "min" scatter reduction functions, so that we could drop the need to depend on `torch-scatter` - https://github.com/pytorch/pytorch/issues/22378#issuecomment-862705586
as it is a bit of an ordeal for being used in just a single model and even then it's optional.

Oh that would be terrific if we had support directly in PyTorch, thanks for asking!

One other approach is to provide a slower python-only implementation of the same and fall back to it if `torch-scatter` is not available, and not install the latter on CI.