Add Python nogil workflow (#2843)

* Use threads for nogil test

* Check equality across parallel simulations

* Update nogil workflow setup

* Update nogil workflow dependencies

* Install pkgconfig for nogil workflow

* Add nogil warning test and set PYTHON_GIL

* update test

* move test

* Update test_nogil.py

* Update test_nogil.py

* Update test_nogil.py

Author: FFroehlich

.github/actions/install-apt-dependencies/action.yml

@@ -11,5 +11,8 @@ runs:
               libboost-chrono-dev \
               libboost-math-dev \
               libboost-serialization-dev \
-              libhdf5-serial-dev
+              libhdf5-serial-dev \
+              pkg-config \
+              libxml2-dev \
+              libxslt1-dev
       shell: bash

.github/workflows/test_python_nogil.yml

@@ -0,0 +1,43 @@
+name: Python nogil Tests
+on:
+  push:
+  pull_request:
+    branches:
+      - main
+  merge_group:
+  workflow_dispatch:
+
+jobs:
+  nogil-tests:
+    name: Python nogil
+    runs-on: ubuntu-24.04
+    env:
+      AMICI_SKIP_CMAKE_TESTS: "TRUE"
+      AMICI_PARALLEL_COMPILE: ""
+    steps:
+    - run: echo "AMICI_DIR=$(pwd)" >> $GITHUB_ENV
+    - name: Set up Python 3.13 free-threaded
+      uses: actions/setup-python@v5
+      with:
+        python-version: '3.13'
+        freethreaded: true
+    - uses: actions/checkout@v4
+      with:
+        fetch-depth: 20
+    - name: Install apt dependencies
+      uses: ./.github/actions/install-apt-dependencies
+    - name: Install python package
+      run: |
+        python3 -m venv venv --clear
+        source venv/bin/activate
+        pip install --upgrade pip wheel
+        pip install numpy sympy cmake-build-extension==0.6.0 swig cython pkgconfig
+        AMICI_BUILD_TEMP="python/sdist/build/temp" \
+          pip install --verbose -e python/sdist[test] --no-build-isolation
+    - run: source venv/bin/activate && pip3 install "sympy>1.12"
+    - name: Python tests
+      env:
+        AMICI_NOGIL: "1"
+      run: |
+        source venv/bin/activate && \
+        pytest tests/test_nogil.py -vv

tests/test_nogil.py

@@ -0,0 +1,18 @@
+import os
+
+import pytest
+
+pytestmark = pytest.mark.skipif(
+    not os.environ.get("AMICI_NOGIL"),
+    reason="only run in nogil workflow",
+)
+
+
+def test_import_warns_without_python_gil(monkeypatch):
+    with pytest.raises(
+        RuntimeWarning,
+        match=r"The global interpreter lock \(GIL\) has been enabled to load module",
+    ):
+        import amici
+
+        print(amici.__version__)