Enabled free-threading multithread tests and added more skips

[vfdev-5]

Description:

• reverted Temporarily disable free-threading build & multithread tests #191
• Added more skips from Skip test under multithreading #188

When running stress tests as following:

while python -m pytest -n 50  -vvv; do :; done

We get more numpy errors:

FAILED ml_dtypes/tests/intn_test.py::ArrayTest::testCasts0_multi_threaded - TypeError: Cannot cast array data from dtype('float16') to dtype(int2) according to the rule 'unsafe'

FAILED ml_dtypes/tests/intn_test.py::ArrayTest::testCasts48_multi_threaded - TypeError: Cannot cast array data from dtype('complex64') to dtype(uint2) according to the rule 'unsafe'

FAILED ml_dtypes/tests/intn_test.py::ArrayTest::testCasts44_multi_threaded - TypeError: Cannot cast array data from dtype(uint2) to dtype('int8') according to the rule 'unsafe'

FAILED ml_dtypes/tests/intn_test.py::ArrayTest::testCasts69_multi_threaded - TypeError: Cannot cast array data from dtype('complex128') to dtype(uint4) according to the rule 'unsafe'


E       Traceback (most recent call last):
E         File "/usr/local/lib/python3.13t/dist-packages/numpy/_core/numeric.py", line 2476, in isclose
E           dt = multiarray.result_type(y, 1.)
E       RuntimeError: A cast was already added for <class 'numpy.dtypes.Float16DType'> -> <class 'numpy.dtype[float8_e5m2]'>. (method: legacy_cast)
E       
E       For more information see https://pluggy.readthedocs.io/en/stable/api_reference.html#pluggy.PluggyTeardownRaisedWarning

/usr/local/lib/python3.13t/dist-packages/pluggy/_callers.py:50: PluggyTeardownRaisedWarning
========================================================================================================= short test summary info =========================================================================================================
FAILED ml_dtypes/tests/finfo_test.py::FinfoTest::testFInfo_float8_e5m2_multi_threaded - pluggy.PluggyTeardownRaisedWarning: A plugin raised an exception during an old-style hookwrapper teardown.


>         self.assertEqual(
              (float_type, d) in allowed_casts, np.can_cast(float_type, d)
          )
E         AssertionError: True != False

ml_dtypes/tests/custom_float_test.py:781: AssertionError
========================================================================================================= short test summary info =========================================================================================================
FAILED ml_dtypes/tests/custom_float_test.py::CustomFloatNumPyTest::testCanCast_float8_e8m0fnu_multi_threaded - AssertionError: True != False
FAILED ml_dtypes/tests/custom_float_test.py::CustomFloatNumPyTest::testCanCast_float8_e4m3fnuz_multi_threaded - AssertionError: True != False

Numpy code:

• https://github.com/numpy/numpy/blob/4206d096253dee344eb9b5c11abd83b3f03ecc57/numpy/_core/src/multiarray/convert_datatype.c#L809-L815

[jakevdp]

Did you add all the skips from #188? If so, I think you should revert them: some of those were due to finfo being incompatible with multithreading, which is a real error rather than a testing issue (that's why I ended up abandoning #188 and temporarily disabling the multithread build instead).

[hawkinsp]

I don't follow

If so, I think you should revert them: some of those were due to finfo being incompatible with multithreading, which is a real error rather than a testing issue

The finfo problems are now fixed (at head numpy, anyway), right?

[jakevdp]

The finfo problems are now fixed (at head numpy, anyway), right?

Yes - that's my point: some of the skips there were added due to finfo tests failing. We shouldn't copy all the skips from that PR to this PR, because some of them are no longer necessary.