Remove mpi4py as dependency

.github/workflows/build-and-test.yml

@@ -74,12 +74,18 @@ jobs:
     steps:
       - name: Checkout Repository
         uses: actions/checkout@v2
-      - name: Install & upgrade pip3 and install OpenMPI
+      - name: Install & upgrade pip3
         run: |
           sudo apt-get -yy update
-          sudo apt-get install -y python3-pip libopenmpi-dev
+          sudo apt-get install -y python3-pip
           sudo rm -rf /var/lib/apt/lists/*
           pip3 install --upgrade --user pip
+      - name: Install OpenMPI and mpi4py
+        run: |
+          sudo apt-get -yy update
+          sudo apt-get install -y libopenmpi-dev
+          sudo rm -rf /var/lib/apt/lists/*
+          pip3 install --user mpi4py
       - name: Checkout precice and make required files discoverable
         run: |
           git clone https://github.com/precice/precice.git precice-core
@@ -93,7 +99,33 @@ jobs:
         run: |
           export CFLAGS=-I$GITHUB_WORKSPACE
           python3 setup.py test
-
+
+  setup_test_no_mpi:
+    name: Run setup test (without MPI based tests)
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v2
+      - name: Install & upgrade pip3
+        run: |
+          sudo apt-get -yy update
+          sudo apt-get install -y python3-pip
+          sudo rm -rf /var/lib/apt/lists/*
+          pip3 install --upgrade --user pip
+      - name: Checkout precice and make required files discoverable
+        run: |
+          git clone https://github.com/precice/precice.git precice-core
+          mkdir -p precice
+          cp precice-core/src/precice/SolverInterface.hpp precice/SolverInterface.hpp
+      - name: Install dependencies
+        run: |
+          pip3 install --user toml
+          python3 -c 'import toml; c = toml.load("pyproject.toml"); print("\n".join(c["build-system"]["requires"]))' | pip3 install -r /dev/stdin
+      - name: Run setup test
+        run: |
+          export CFLAGS=-I$GITHUB_WORKSPACE
+          python3 setup.py test
+
   pip_install:
     name: Run pip install
     needs: [setup_test]

.github/workflows/build-spack.yml

@@ -22,4 +22,4 @@ jobs:
           cp spack/repo/packages/py-pyprecice/*.patch /py-pyprecice-repo/packages/py-pyprecice/
       - name: Try to build py-pyprecice with spack and test it
         run: |
-          . /opt/spack/share/spack/setup-env.sh && spack env activate ci && spack arch && spack find && spack dev-build py-pyprecice@develop target=x86_64 && spack load precice py-numpy py-mpi4py py-cython openssh openmpi && mkdir runner && cd runner && python3 -c "import precice; print(precice.__version__)"
+          . /opt/spack/share/spack/setup-env.sh && spack env activate ci && spack arch && spack find && spack dev-build py-pyprecice@develop target=x86_64 && spack load precice py-numpy py-cython openssh openmpi && mkdir runner && cd runner && python3 -c "import precice; print(precice.__version__)"

README.md

@@ -13,8 +13,6 @@ Please refer to [precice.org](https://www.precice.org/installation-bindings-pyth
 
 **preCICE**: Refer to [the preCICE wiki](https://github.com/precice/precice/wiki#1-get-precice) for information on building and installation.
 
-**MPI**: `mpi4py` requires MPI to be installed on your system.
-
 # Installing the package
 
 We recommend using pip3 (version 19.0.0 or newer required) for the sake of simplicity. You can check your pip3 version via `pip3 --version`. To update pip3, use the following line:

cyprecice/cyprecice.pyx

@@ -7,7 +7,6 @@ The python module precice offers python language bindings to the C++ coupling li
 
 cimport cyprecice
 import numpy as np
-from mpi4py import MPI
 
 from cpython.version cimport PY_MAJOR_VERSION  # important for determining python version in order to properly normalize string input. See http://docs.cython.org/en/latest/src/tutorial/strings.html#general-notes-about-c-strings and https://github.com/precice/precice/issues/68 .
 

pyproject.toml

@@ -1,3 +1,3 @@
 [build-system]
 # PEP 518 - minimum build system requirements
-requires = ["setuptools", "wheel", "Cython>=0.29", "packaging", "pip>=19.0.0", "numpy", "mpi4py"]
+requires = ["setuptools", "wheel", "Cython>=0.29", "pip>=19.0.0", "numpy"]

setup.py

@@ -145,9 +145,7 @@ def initialize_options(self):
     author_email='[email protected]',
     license='LGPL-3.0',
     python_requires='>=3',
-    install_requires=['numpy', 'mpi4py'],
-    # mpi4py is only needed, if preCICE was compiled with MPI
-    # see https://github.com/precice/python-bindings/issues/8
+    install_requires=['numpy'],
     packages=['precice'],
     zip_safe=False  # needed because setuptools are used
 )

spack/repo/packages/py-pyprecice/package.py

@@ -44,7 +44,6 @@ class PyPyprecice(PythonPackage):
     depends_on("python@3:", type=("build", "run"))
     depends_on("py-setuptools", type="build")
     depends_on("py-numpy", type=("build", "run"))
-    depends_on("py-mpi4py", type=("build", "run"))
     depends_on("[email protected]:", type=("build"))
 
     phases = ['install_lib', 'build_ext', 'install']

test/test_bindings_module.py

@@ -1,7 +1,13 @@
 import precice
 from unittest import TestCase
 import numpy as np
-from mpi4py import MPI
+import warnings
+try:
+    from mpi4py import MPI
+    has_mpi = True
+except ModuleNotFoundError:
+    warnings.warn("No MPI detected. Some tests will not be run.")
+    has_mpi = False
 
 
 class TestBindings(TestCase):
@@ -13,10 +19,11 @@ def test_constructor(self):
         solver_interface = precice.Interface("test", "dummy.xml", 0, 1)
         self.assertTrue(True)
 
-    def test_constructor_custom_mpi_comm(self):
-        solver_interface = precice.Interface(
-            "test", "dummy.xml", 0, 1, MPI.COMM_WORLD)
-        self.assertTrue(True)
+    if has_mpi:
+        def test_constructor_custom_mpi_comm(self):
+            solver_interface = precice.Interface(
+                "test", "dummy.xml", 0, 1, MPI.COMM_WORLD)
+            self.assertTrue(True)
 
     def test_version(self):
         precice.__version__