[python,parallel] add additional test for Communication bindings

dune/python/test/pythontests.py

@@ -54,6 +54,36 @@ void run(pybind11::array_t< T >& a)
 }
 """
 
+def test_communicator():
+    """
+    Test mapping between Dune::Communication and mpi4py.MPI.Comm
+    """
+    import dune.common
+    from dune.common import Communication, No_Comm, comm
+    if comm != No_Comm: # we are actually able to use MPI
+        from mpi4py import MPI
+        comm1 = MPI.COMM_WORLD
+        c1 = Communication(comm1)
+        c2 = Communication(c1)
+        c3 = Communication(dune.common.comm)
+        c4 = Communication(MPI.COMM_SELF)
+        assert(c1 == c2)
+        assert(c1 == c3)
+        assert(c1 != c4)
+        assert(c1 == MPI.COMM_WORLD)
+        assert(c1 != MPI.COMM_SELF)
+        assert(c4 == MPI.COMM_SELF)
+        assert(c1.rank == MPI.COMM_WORLD.rank)
+        assert(c1.size == MPI.COMM_WORLD.size)
+        assert(c4.rank == 0)
+        assert(c4.size == 1)
+    else: # we are working without MPI
+        c = Communication(dune.common.comm)
+        assert(c == comm)
+        assert(c == No_Comm)
+        assert(c is No_Comm)
+        assert(comm is No_Comm)
+
 def test_numpyvector():
     """
     Test correct exchange of numpy arrays to C++ side.
@@ -87,3 +117,4 @@ if __name__ == "__main__":
     _ = getDunePyDir()
     test_class_export()
     test_numpyvector()
+    test_communicator()