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ENH: Free-Threading (No-GIL) Support for Python 3.13+ #130
Description
Activity
Initial thoughts..
uv venv --python 3.13t .ftci source .ftci/bin/activate uv pip install numpy scipy pytest-timeout pytest-durations pytest-run-parallel uv pip install -v . uv run --no-project python -Xgil=0 -m pytest --parallel-threads=2 --iterations=2 -v -s --timeout=600 --durations=10 -m "not thread_unsafe"
has one failure
PARALLEL FAILED test/test_solve_random_cone_prob.py::test_solve_feasible[True-False] - AssertionError:
Which goes away without
--iterations.Yes, it would be great to enable this, thanks for taking a look!
Reacted by Rohit Goswami- added a commit that references this issue
on Apr 17, 2026
As I see it (from a first look), the primary issue from a design perspective is to have all the Python threads synchronously access only one running
scsinstance. It is unclear ifscsitself has any locking or design decisions around concurrency.For the bindings here, it should mean introducing an instance-level lock within the SCS struct.
The standard TODOs for adding free-threading support are in two phases, the first of which is a baseline consisting of the following tasks:
pytest-run-parallelto find potential issues, and fix them.cp313t-*to CI to build free-threading wheels.The next phase is a bit more invasive, and it involves a single task:
For more details, please see the suggested plan of attack in the py-free-threading guide. The two phase approach is discussed in explosion/cymem#47 (comment) and gorakhargosh/watchdog#1105 (comment).
Note that this is the first time I've looked at this repo, so I might be
missing known issues or code that needs closer inspection. Any suggestions here
will be very useful.
Let me know if I ought to hold off for any reason.