tests: Ensure float type SparseFunctions have matching coordinate dtype

Author: EdCaunt

devito/types/sparse.py

@@ -204,9 +204,7 @@ def __subfunc_setup__(self, suffix, keys, dtype=None, inkwargs=False, **kwargs):
 
         # Complex coordinates are not valid, so fall back to corresponding
         # real floating point type if dtype is complex.
-        if issubclass(dtype, np.complexfloating):
-            dtype = {np.complex64: np.float32,
-                     np.complex128: np.float64}.get(dtype, np.float32)
+        dtype = dtype(0).real.__class__
 
         sf = SparseSubFunction(
             name=name, dtype=dtype, dimensions=dimensions,

tests/test_sparse.py

@@ -498,9 +498,13 @@ def test_mpi_no_data(self, mode):
         assert np.all(m.data[0, :, :] == ftest.data[:])
 
     @pytest.mark.parametrize('dtype, expected', [(np.complex64, np.float32),
-                                                 (np.complex128, np.float64)])
+                                                 (np.complex128, np.float64),
+                                                 (np.float16, np.float16)])
     def test_coordinate_type(self, dtype, expected):
-        """Test that coordinates are always real"""
+        """
+        Test that coordinates are always real and SparseFunction dtype is
+        otherwise preserved.
+        """
         grid = Grid(shape=(11,))
         s = SparseFunction(name='src', npoint=1,
                            grid=grid, dtype=dtype)