compiler: Fix uxreplace's eval of subbed numeric exprs

Author: FabioLuporini

devito/symbolics/manipulation.py

@@ -14,7 +14,7 @@
 from devito.symbolics.queries import q_leaf
 from devito.symbolics.search import retrieve_indexed, retrieve_functions
 from devito.symbolics.unevaluation import (
-    Add as UnevalAdd, Mul as UnevalMul, Pow as UnevalPow
+    Add as UnevalAdd, Mul as UnevalMul, Pow as UnevalPow, UnevaluableMixin
 )
 from devito.tools import as_list, as_tuple, flatten, split, transitive_closure
 from devito.types.basic import Basic, Indexed
@@ -300,7 +300,11 @@ def _eval_numbers(expr, args):
     """
     numbers, others = split(args, lambda i: i.is_Number)
     if len(numbers) > 1:
-        args[:] = [expr.func(*numbers)] + others
+        if isinstance(expr, UnevaluableMixin):
+            cls = expr.func.__base__
+        else:
+            cls = expr.func
+        args[:] = [cls(*numbers)] + others
 
 
 def flatten_args(args, op, ignore=None):

tests/test_symbolics.py

@@ -4,7 +4,7 @@
 import pytest
 import numpy as np
 
-from sympy import Expr, Symbol
+from sympy import Expr, Number, Symbol
 from devito import (Constant, Dimension, Grid, Function, solve, TimeFunction, Eq,  # noqa
                     Operator, SubDimension, norm, Le, Ge, Gt, Lt, Abs, sin, cos,
                     Min, Max)
@@ -13,7 +13,7 @@
 from devito.symbolics import (retrieve_functions, retrieve_indexed, evalrel,  # noqa
                               CallFromPointer, Cast, DefFunction, FieldFromPointer,
                               INT, FieldFromComposite, IntDiv, Namespace, Rvalue,
-                              ReservedWord, ListInitializer, uxreplace,
+                              ReservedWord, ListInitializer, uxreplace, pow_to_mul,
                               retrieve_derivatives, BaseCast)
 from devito.tools import as_tuple
 from devito.types import (Array, Bundle, FIndexed, LocalObject, Object,
@@ -636,6 +636,21 @@ def __new__(cls, name=None, arguments=None, p0=None, p1=None, p2=None):
         assert func1.p1 == (g,)
         assert func1.p2 == 'bar'
 
+    def test_reduce_to_number(self):
+        grid = Grid(shape=(4, 4))
+        x, _ = grid.dimensions
+        h_x = x.spacing
+
+        # Emulate lowered coefficient
+        w = -0.0354212/(h_x*h_x)
+        w_lowered = pow_to_mul(w)
+
+        w_sub = uxreplace(w_lowered, {h_x: Number(3)})
+
+        assert np.isclose(w_sub, -0.003935689)
+        assert not w_sub.is_Mul
+        assert w_sub.is_Number
+
 
 def test_minmax():
     grid = Grid(shape=(5, 5))