mpi: fix halo exchange for non-mpi devito within mpi code

devito/arch/compiler.py

@@ -877,7 +877,7 @@ def __init_finalize__(self, **kwargs):
         self.ldflags = filter_ordered(self.ldflags + extrald)
 
     def __lookup_cmds__(self):
-        self._base.__lookup_cmds__()
+        self._base.__lookup_cmds__(self)
         self.CC = environ.get('CC', self.CC)
         self.CXX = environ.get('CXX', self.CXX)
         self.MPICC = environ.get('MPICC', self.MPICC)

devito/mpi/distributed.py

@@ -185,7 +185,7 @@ class Distributor(AbstractDistributor):
     """
 
     def __init__(self, shape, dimensions, input_comm=None, topology=None):
-        super(Distributor, self).__init__(shape, dimensions)
+        super().__init__(shape, dimensions)
 
         if configuration['mpi']:
             # First time we enter here, we make sure MPI is initialized
@@ -426,7 +426,7 @@ class SparseDistributor(AbstractDistributor):
     """
 
     def __init__(self, npoint, dimension, distributor):
-        super(SparseDistributor, self).__init__(npoint, dimension)
+        super().__init__(npoint, dimension)
         self._distributor = distributor
 
         # The dimension decomposition
@@ -523,7 +523,7 @@ def __init__(self, neighborhood):
         self._entries = [i for i in neighborhood if isinstance(i, tuple)]
 
         fields = [(''.join(j.name[0] for j in i), c_int) for i in self.entries]
-        super(MPINeighborhood, self).__init__('nb', 'neighborhood', fields)
+        super().__init__('nb', 'neighborhood', fields)
 
     @property
     def entries(self):
@@ -552,7 +552,7 @@ def _C_typedecl(self):
                                    for i, j in groups])
 
     def _arg_defaults(self):
-        values = super(MPINeighborhood, self)._arg_defaults()
+        values = super()._arg_defaults()
         for name, i in zip(self.fields, self.entries):
             setattr(values[self.name]._obj, name, self.neighborhood[i])
         return values

devito/types/dense.py

@@ -741,7 +741,8 @@ def _C_get_field(self, region, dim, side=None):
 
     def _halo_exchange(self):
         """Perform the halo exchange with the neighboring processes."""
-        if not MPI.Is_initialized() or MPI.COMM_WORLD.size == 1:
+        if not MPI.Is_initialized() or MPI.COMM_WORLD.size == 1 or \
+                not configuration['mpi']:
             # Nothing to do
             return
         if MPI.COMM_WORLD.size > 1 and self._distributor is None:

tests/test_mpi.py

@@ -419,6 +419,21 @@ def test_local_indices(self, shape, expected):
         assert all(i == slice(*j)
                    for i, j in zip(f.local_indices, expected[grid.distributor.myrank]))
 
+    @pytest.mark.parallel(mode=4)
+    @pytest.mark.parametrize('shape', [(1,), (2, 3), (4, 5, 6)])
+    def test_mpi4py_nodevmpi(self, shape):
+
+        with switchconfig(mpi=False):
+            # Mimic external mpi init
+            MPI.Init()
+            # Check that internal Function work correctly
+            grid = Grid(shape=shape)
+            f = Function(name="f", grid=grid, space_order=1)
+            assert f.data.shape == shape
+            assert f.data_with_halo.shape == tuple(s+2 for s in shape)
+            assert f.data._local.shape == shape
+            MPI.Finalize()
+
 
 class TestSparseFunction(object):