Test if we can swap out with mpich

.github/workflows/docker.yml

@@ -89,4 +89,44 @@ jobs:
         docker run --rm local-test-image:latest bash -c "\
             python3 -m pip install pytest scipy && \
             cd /dolfinx/python/test && \
-            python3 -m pytest -vs"
+            python3 -m pytest -vs"
+
+
+    - name: Verify MPI ABI Swap (Stubs -> MPICH)
+      run: |
+        docker run --rm local-test-image:latest bash -c "\
+          cat << 'EOF' > test_comm.cpp
+          #include <iostream>
+          #include <mpi.h>
+          int main(int argc, char **argv) {
+              MPI_Init(&argc, &argv);
+              int rank, size;
+              MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+              MPI_Comm_size(MPI_COMM_WORLD, &size);
+              std::cout << \"Hello from rank \" << rank << \" of \" << size << std::endl;
+              MPI_Finalize();
+              return 0;
+          }
+          EOF
+
+          echo '--- Compiling with Stubs ---' && \
+          mpicxx -std=c++17 test_comm.cpp -o test_comm && \
+
+          echo '--- Running with Stubs ---' && \
+          mpiexec -n 1 ./test_comm && \
+
+          echo '--- Downloading & Building MPICH with ABI support ---' && \
+          MPICH_VERSION=4.3.2 && \
+          wget -q https://www.mpich.org/static/downloads/\${MPICH_VERSION}/mpich-\${MPICH_VERSION}.tar.gz && \
+          tar xfz mpich-\${MPICH_VERSION}.tar.gz && \
+          cd mpich-\${MPICH_VERSION} && \
+          ./configure --enable-mpi-abi --prefix=/opt/mpich --disable-fortran --disable-cxx --disable-romio && \
+          make -j4 install && \
+          cd .. && \
+
+          echo '--- Checking Dynamic Linking (ldd) ---' && \
+          export LD_LIBRARY_PATH=/opt/mpich/lib:\$LD_LIBRARY_PATH && \
+          ldd test_comm && \
+
+          echo '--- Running with real MPICH ---' && \
+          /opt/mpich/bin/mpiexec -n 1 ./test_comm"

CMakeLists.txt

@@ -12,11 +12,12 @@ add_library(mpistub SHARED ${MPI_STUB_SOURCES})
 
 # Force the output name to "mpi" to generate libmpi.so
 set_target_properties(mpistub PROPERTIES
-    OUTPUT_NAME "mpi"
-    VERSION "1.0.0"
-    SOVERSION "12"
+    OUTPUT_NAME "mpi_abi"
+    VERSION 0.0.0
+    SOVERSION 0
     C_STANDARD 11
     C_STANDARD_REQUIRED YES
+    WINDOWS_EXPORT_ALL_SYMBOLS 1
 )
 
 # Setup include directories

Dockerfile

@@ -56,7 +56,7 @@ RUN python3 -m venv ${VIRTUAL_ENV} && \
     pip install --no-cache-dir cython numpy==${NUMPY_VERSION}
 
 # Install mpi4py against our stub
-RUN env MPICC="${STUBS_DIR}/bin/mpicc" \
+RUN env MPI4PY_BUILD_MPIABI=1 MPICC="${STUBS_DIR}/bin/mpicc" \
     pip install --no-cache-dir --no-build-isolation --no-binary mpi4py mpi4py
 
 RUN python3 -c "from mpi4py import MPI; print(MPI.Get_version())" && \