#3646 set CMake parallelism for Windows wheels

.github/workflows/publish_pypi.yml

@@ -37,6 +37,16 @@ jobs:
         with:
           python-version: 3.8
 
+      - name: Get number of cores on Windows
+        id: get_num_cores
+        shell: python
+        run: |
+          from os import environ, sched_getaffinity
+          num_cpus = len(sched_getaffinity(0))
+          output_file = environ['GITHUB_OUTPUT']
+          with open(output_file, "a", encoding="utf-8") as output_stream:
+              output_stream.write(f"count={num_cpus}\n")
+
       - name: Clone pybind11 repo (no history)
         run: git clone --depth 1 --branch v2.11.1 https://github.com/pybind/pybind11.git
 
@@ -64,7 +74,14 @@ jobs:
       - name: Build 64-bit wheels on Windows
         run: pipx run cibuildwheel --output-dir wheelhouse
         env:
-          CIBW_ENVIRONMENT: 'PYBAMM_USE_VCPKG=ON VCPKG_ROOT_DIR=C:\vcpkg VCPKG_DEFAULT_TRIPLET=x64-windows-static-md VCPKG_FEATURE_FLAGS=manifests,registries CMAKE_GENERATOR="Visual Studio 17 2022" CMAKE_GENERATOR_PLATFORM=x64'
+          CIBW_ENVIRONMENT: >
+            PYBAMM_USE_VCPKG=ON
+            VCPKG_ROOT_DIR=C:\vcpkg
+            VCPKG_DEFAULT_TRIPLET=x64-windows-static-md
+            VCPKG_FEATURE_FLAGS=manifests,registries
+            CMAKE_GENERATOR="Visual Studio 17 2022"
+            CMAKE_GENERATOR_PLATFORM=x64'
+            CMAKE_BUILD_PARALLEL_LEVEL: ${{ steps.get_num_cores.outputs.num_cpus }}
           CIBW_ARCHS: "AMD64"
           CIBW_BEFORE_BUILD: python -m pip install setuptools wheel # skip CasADi and CMake
           CIBW_TEST_COMMAND: python -c "import pybamm; pybamm.IDAKLUSolver()"