compiler: make lower_expr apply the mapper to indices in case functio…

…n only appear as index

.github/workflows/pytest-gpu.yml

@@ -84,6 +84,10 @@ jobs:
         echo "PATH=$PATH" >> $GITHUB_ENV
         echo "LD_LIBRARY_PATH=$LD_LIBRARY_PATH" >> $GITHUB_ENV
 
+    - name: Check pip
+      run: |
+        type -a pip3
+
     - name: Install dependencies
       run: |
         pip3 install --upgrade pip

devito/ir/equations/algorithms.py

@@ -134,7 +134,7 @@ def lower_exprs(expressions, **kwargs):
             dimension_map = {}
 
         # Handle Functions (typical case)
-        mapper = {f: f.indexify(lshift=True, subs=dimension_map)
+        mapper = {f: lower_exprs(f.indexify(subs=dimension_map), **kwargs)
                   for f in retrieve_functions(expr)}
 
         # Handle Indexeds (from index notation)
@@ -160,6 +160,7 @@ def lower_exprs(expressions, **kwargs):
         mapper.update(dimension_map)
         # Add the user-supplied substitutions
         mapper.update(subs)
+        # Apply mapper to expression
         processed.append(uxreplace(expr, mapper))
 
     if isinstance(expressions, Iterable):

devito/types/basic.py

@@ -1069,7 +1069,7 @@ def _data_alignment(self):
         """
         return default_allocator().guaranteed_alignment
 
-    def indexify(self, indices=None, lshift=False, subs=None):
+    def indexify(self, indices=None, subs=None):
         """Create a types.Indexed from the current object."""
         if indices is not None:
             return Indexed(self.indexed, *indices)
@@ -1078,11 +1078,9 @@ def indexify(self, indices=None, lshift=False, subs=None):
         subs = subs or {}
         subs = [{**{d.spacing: 1, -d.spacing: -1}, **subs} for d in self.dimensions]
 
-        # Add halo shift
-        shift = self._size_nodomain.left if lshift else tuple([0]*len(self.dimensions))
         # Indices after substitutions
-        indices = [sympy.sympify((a - o + f).xreplace(s)) for a, o, f, s in
-                   zip(self.args, self.origin, shift, subs)]
+        indices = [sympy.sympify((a - o).xreplace(s)) for a, o, s in
+                   zip(self.args, self.origin, subs)]
         indices = [i.xreplace({k: sympy.Integer(k) for k in i.atoms(sympy.Float)})
                    for i in indices]
         return self.indexed[indices]

tests/test_operator.py

@@ -317,6 +317,34 @@ def test_nested_lowering(self):
         assert np.all(u0.data[:2, :2] == 1) and np.all(u0.data[1:3, 1:3] == 1)
         assert np.all(u0.data[2:3, 3] == 2) and np.all(u0.data[3, 2:3] == 2)
 
+    def test_nested_lowering_indexify(self):
+        """
+        Tests that nested function are lowered if only used as index.
+        """
+        grid = Grid(shape=(4, 4), dtype=np.int32)
+        x, y = grid.dimensions
+
+        u0 = Function(name="u0", grid=grid)
+        u1 = Function(name="u1", grid=grid)
+        u2 = Function(name="u2", grid=grid)
+
+        u0.data[:, :] = 2
+        u1.data[:, :] = 1
+        u2.data[:, :] = 1
+
+        # Function as index only
+        eq0 = Eq(u0._subs(x, u1), 2*u0)
+        # Function as part of expression as index only
+        eq1 = Eq(u0._subs(x, u1._subs(y, u2) + 1), 4*u0)
+
+        op0 = Operator(eq0)
+        op0.apply()
+        op1 = Operator(eq1)
+        op1.apply()
+        assert np.all(np.all(u0.data[i, :] == 2) for i in [0, 3])
+        assert np.all(u0.data[1, :] == 4)
+        assert np.all(u0.data[2, :] == 8)
+
 
 class TestArithmetic(object):