test_nested_parallel_limit fails on 1-core-VM

[bmwiedemann]

While working on reproducible builds for openSUSE, I noticed
that 2 tests would fail on 1-core-VMs (using python-joblib 0.12.1)

_______________________ test_nested_parallel_limit[loky] _______________________

>       assert backend_types_and_levels == expected_types_and_levels
E       AssertionError: assert [('LokyBacken...lBackend', 2)] == [('LokyBackend...lBackend', 3)]

____________________ test_nested_parallel_limit[threading] _____________________        
backend = 'threading'

    @with_multiprocessing
    @parametrize('backend', ['loky', 'threading'])
    def test_nested_parallel_limit(backend):
        with parallel_backend(backend, n_jobs=2):
            backend_types_and_levels = _recursive_backend_info()

        top_level_backend_type = backend.title() + 'Backend'
        expected_types_and_levels = [
            (top_level_backend_type, 0),
            ('ThreadingBackend', 1),
            ('SequentialBackend', 2),
            ('SequentialBackend', 3)
        ]
>       assert backend_types_and_levels == expected_types_and_levels
E       AssertionError: assert [('ThreadingB...lBackend', 2)] == [('ThreadingBa...lBackend', 3)]

[ogrisel]

Thanks for the report.

I can reproduce on master with:

$ taskset -c 0 pytest -k test_nested_parallelism_limit

I will investigate.

[bmwiedemann]

I verified that it also fixes the tests in our 1-core-VMs. Thanks for the quick response 👍