pytorch - 💡(How to fix) Fix DISABLED test_forward_nn_LinearCrossEntropyLoss_cuda_bfloat16 (__main__.TestModuleCUDA)

Platforms: linux, slow

This test was disabled because it is failing in CI. See recent examples and the most recent trunk workflow logs.

Over the past 6 hours, it has been determined flaky in 3 workflow(s) with 6 failures and 3 successes.

Debugging instructions (after clicking on the recent samples link): DO NOT ASSUME THINGS ARE OKAY IF THE CI IS GREEN. We now shield flaky tests from developers so CI will thus be green but it will be harder to parse the logs. To find relevant log snippets:

1. Click on the workflow logs linked above
2. Click on the Test step of the job so that it is expanded. Otherwise, the grepping will not work.
3. Grep for test_forward_nn_LinearCrossEntropyLoss_cuda_bfloat16
4. There should be several instances run (as flaky tests are rerun in CI) from which you can study the logs.

Traceback (most recent call last):
  File "/__w/pytorch/pytorch/test/test_modules.py", line 85, in test_forward
    self.assertEqual(outputs, ref_outputs)
  File "/opt/conda/envs/py_3.10/lib/python3.10/site-packages/torch/testing/_internal/common_utils.py", line 4576, in assertEqual
    raise error_metas.pop()[0].to_error(  # type: ignore[index]
AssertionError: Scalars are not close!

Expected 1.4453125 but got 1.46875.
Absolute difference: 0.0234375 (up to 1e-05 allowed)
Relative difference: 0.016216216216216217 (up to 0.016 allowed)

To execute this test, run the following from the base repo dir:
    PYTORCH_TEST_CUDA_MEM_LEAK_CHECK=1 PYTORCH_TEST_WITH_SLOW_GRADCHECK=1 python test/test_modules.py TestModuleCUDA.test_forward_nn_LinearCrossEntropyLoss_cuda_bfloat16

This message can be suppressed by setting PYTORCH_PRINT_REPRO_ON_FAILURE=0

Test file path: test_modules.py

For all disabled tests (by GitHub issue), see https://hud.pytorch.org/disabled.

cc @albanD @mruberry @jbschlosser @walterddr @mikaylagawarecki