api: make sure reconstructed factor are None

devito/ir/equations/equation.py

@@ -8,7 +8,7 @@
                                Stencil, detect_io, detect_accesses)
 from devito.symbolics import IntDiv, uxreplace
 from devito.tools import Pickable, Tag, frozendict
-from devito.types import Eq, Inc, ReduceMax, ReduceMin
+from devito.types import Eq, Inc, ReduceMax, ReduceMin, relational_min
 
 __all__ = ['LoweredEq', 'ClusterizedEq', 'DummyEq', 'OpInc', 'OpMin', 'OpMax']
 
@@ -188,15 +188,19 @@ def __new__(cls, *args, **kwargs):
         for d in ordering:
             if not d.is_Conditional:
                 continue
-            if d.condition is None:
+            if d._factor is not None:
                 conditionals[d] = GuardFactor(d)
             else:
                 cond = diff2sympy(lower_exprs(d.condition))
-                if d.factor is not None:
+                if d._factor is not None:
                     cond = sympy.And(cond, GuardFactor(d))
                 conditionals[d] = cond
-            if d.factor is not None:
-                expr = uxreplace(expr, {d: IntDiv(d.fact_index, d.factor)})
+            # Replace dimension with index
+            index = d.index
+            if d.condition is not None:
+                index = index - relational_min(d.condition, d.parent)
+            expr = uxreplace(expr, {d: IntDiv(index, d.factor)})
+
         conditionals = frozendict(conditionals)
 
         # Lower all Differentiable operations into SymPy operations

devito/types/dimension.py

@@ -13,7 +13,6 @@
 from devito.types.args import ArgProvider
 from devito.types.basic import Symbol, DataSymbol, Scalar
 from devito.types.constant import Constant
-from devito.types.relational import relational_min
 
 
 __all__ = ['Dimension', 'SpaceDimension', 'TimeDimension', 'DefaultDimension',
@@ -866,7 +865,7 @@ def __init_finalize__(self, name, parent=None, factor=None, condition=None,
         super().__init_finalize__(name, parent)
 
         # Always make the factor symbolic to allow overrides with different factor.
-        if factor is None:
+        if factor is None or factor == 1:
             self._factor = None
         elif is_integer(factor):
             self._factor = Constant(name="%sf" % name, value=factor, dtype=np.int32)
@@ -895,18 +894,6 @@ def condition(self):
     def indirect(self):
         return self._indirect
 
-    @property
-    def fact_index(self):
-        if self.condition is None or self._factor is None:
-            return self.index
-
-        # This is the corner case where both a condition and a factor are provided
-        # the index will need to be `self.parent - min(self.condition)` to avoid
-        # shifted indexing. E.g if you have `factor=2` and `condition=Ge(time, 10)`
-        # then the lowered index needs to be `(time - 10)/ 2`
-        ltkn = relational_min(self.condition, self.parent)
-        return self.index - ltkn
-
     @cached_property
     def free_symbols(self):
         retval = set(super().free_symbols)

devito/types/relational.py

@@ -218,7 +218,8 @@ def relational_min(expr, s):
         - if `expr` is `s < 10`, then the minimum valid value for `s` is 0
         - if `expr` is `s >= 10`, then the minimum valid value for `s` is 10
     """
-    assert expr.has(s), "Symbol %s not found in expression %s" % (s, expr)
+    if not expr.has(s):
+        return 0
 
     return _relational_min(expr, s)