CI: Python w/ MPI (#182)

* CI: Python w/ MPI

Test Python with MPI as well.

* Fix: mpi4py requirement for `--target pip_install`

.github/workflows/ubuntu.yml

@@ -8,7 +8,7 @@ concurrency:
 
 jobs:
   build_gcc:
-    name: GCC w/ MPI
+    name: GCC w/ MPI w/ Python
     runs-on: ubuntu-20.04
     if: github.event.pull_request.draft == false
     env:
@@ -39,8 +39,10 @@ jobs:
       run: |
         cmake -S . -B build            \
           -DCMAKE_BUILD_TYPE=Debug     \
-          -DCMAKE_VERBOSE_MAKEFILE=ON
+          -DCMAKE_VERBOSE_MAKEFILE=ON  \
+          -DImpactX_PYTHON=ON
         cmake --build build -j 2
+        cmake --build build --target pip_install
 
     - name: run ImpactX
       run: |

CMakeLists.txt

@@ -385,8 +385,13 @@ if(ImpactX_PYTHON)
     )
 
     # this will also upgrade/downgrade dependencies, e.g., when the version of numpy changes
+    if(ImpactX_MPI)
+        set(pyImpactX_REQUIREMENT_FILE "requirements_mpi.txt")
+    else()
+        set(pyImpactX_REQUIREMENT_FILE "requirements.txt")
+    endif()
     add_custom_target(${ImpactX_CUSTOM_TARGET_PREFIX}pip_install_requirements
-        ${Python_EXECUTABLE} -m pip install ${PYINSTALLOPTIONS} -r "${ImpactX_SOURCE_DIR}/requirements.txt"
+        ${Python_EXECUTABLE} -m pip install ${PYINSTALLOPTIONS} -r "${ImpactX_SOURCE_DIR}/${pyImpactX_REQUIREMENT_FILE}"
         WORKING_DIRECTORY
             ${ImpactX_BINARY_DIR}
     )

requirements_mpi.txt

@@ -0,0 +1,2 @@
+-r requirements.txt
+mpi4py>=2.1.0