api: fix pickling of sparse operations

devito/operations/interpolators.py

@@ -13,7 +13,7 @@
 from devito.finite_differences.elementary import floor
 from devito.logger import warning
 from devito.symbolics import retrieve_function_carriers, retrieve_functions, INT
-from devito.tools import as_tuple, flatten, filter_ordered
+from devito.tools import as_tuple, flatten, filter_ordered, Pickable
 from devito.types import (ConditionalDimension, Eq, Inc, Evaluable, Symbol,
                           CustomDimension, SubFunction)
 from devito.types.utils import DimensionTuple
@@ -33,7 +33,7 @@ def wrapper(interp, *args, **kwargs):
     return wrapper
 
 
-class UnevaluatedSparseOperation(sympy.Expr, Evaluable):
+class UnevaluatedSparseOperation(sympy.Expr, Evaluable, Pickable):
 
     """
     Represents an Injection or an Interpolation operation performed on a
@@ -48,6 +48,7 @@ class UnevaluatedSparseOperation(sympy.Expr, Evaluable):
     """
 
     subdomain = None
+    __rargs__ = ('interpolator',)
 
     def __new__(cls, interpolator):
         obj = super().__new__(cls)
@@ -79,6 +80,9 @@ class Interpolation(UnevaluatedSparseOperation):
     Evaluates to a list of Eq objects.
     """
 
+    __rargs__ = ('expr', 'increment', 'implicit_dims', 'self_subs') + \
+        UnevaluatedSparseOperation.__rargs__
+
     def __new__(cls, expr, increment, implicit_dims, self_subs, interpolator):
         obj = super().__new__(cls, interpolator)
 
@@ -107,6 +111,8 @@ class Injection(UnevaluatedSparseOperation):
     Evaluates to a list of Eq objects.
     """
 
+    __rargs__ = ('field', 'expr', 'implicit_dims') + UnevaluatedSparseOperation.__rargs__
+
     def __new__(cls, field, expr, implicit_dims, interpolator):
         obj = super().__new__(cls, interpolator)
 

tests/test_pickle.py

@@ -183,6 +183,27 @@ def test_alias_sparse_function(self, pickle):
         assert sf.dtype == f0.dtype == new_f0.dtype
         assert sf.npoint == f0.npoint == new_f0.npoint
 
+    @pytest.mark.parametrize('interp', ['linear', 'sinc'])
+    @pytest.mark.parametrize('op', ['inject', 'interpolate'])
+    def test_sparse_op(self, pickle, interp, op):
+        grid = Grid(shape=(3,))
+        sf = SparseFunction(name='sf', grid=grid, npoint=3, space_order=2,
+                            coordinates=[(0.,), (1.,), (2.,)],
+                            interpolation=interp)
+        u = Function(name='u', grid=grid, space_order=4)
+
+        if op == 'inject':
+            expr = sf.inject(u, sf)
+        else:
+            expr = sf.interpolate(u)
+
+        pkl_expr = pickle.dumps(expr)
+        new_expr = pickle.loads(pkl_expr)
+
+        assert new_expr.interpolator._name == expr.interpolator._name
+        assert new_expr.implicit_dims == expr.implicit_dims
+        assert str(new_expr.evaluate) == str(expr.evaluate)
+
     def test_internal_symbols(self, pickle):
         s = dSymbol(name='s', dtype=np.float32)
         pkl_s = pickle.dumps(s)