def _expand_conditional_conditional(node, self):
if self.predicate(node):
condition, then, else_ = map(self, node.children)
return Sum(Product(Conditional(condition, one, Zero()), then),
Product(Conditional(condition, Zero(), one), else_))
else:
return reuse_if_untouched(node, self)
def _replace_delta_delta(node, self):
i, j = node.i, node.j
if isinstance(i, Index) or isinstance(j, Index):
if isinstance(i, Index) and isinstance(j, Index):
assert i.extent == j.extent
if isinstance(i, Index):
assert i.extent is not None
size = i.extent
if isinstance(j, Index):
assert j.extent is not None
size = j.extent
return Indexed(Identity(size), (i, j))
else:
def expression(index):
if isinstance(index, int):
return Literal(index)
elif isinstance(index, VariableIndex):
return index.expression
else:
raise ValueError("Cannot convert running index to expression.")
e_i = expression(i)
e_j = expression(j)
return Conditional(Comparison("==", e_i, e_j), one, Zero())
def test_conditional_simplification():
a = Variable("A", ())
b = Variable("B", ())
expr = Conditional(LogicalAnd(b, a), a, a)
assert expr == a
def _collect_monomials_conditional(expression, self):
"""Refactorises a conditional expression into a sum-of-products form,
pulling only "atomics" out of conditional expressions.
:arg expression: a GEM expression to refactorise
:arg self: function for recursive calls
:returns: :py:class:`MonomialSum`
"""
condition, then, else_ = expression.children
# Recursively refactorise both branches to `MonomialSum`s
then_ms = self(then)
else_ms = self(else_)
result = MonomialSum()
# For each set of atomics, create a new Conditional node. Atomics
# are considered safe to be pulled out of conditionals, but other
# expressions remain inside conditional branches.
zero = Zero()
for k in then_ms.monomials.keys() | else_ms.monomials.keys():
_then = then_ms.monomials.get(k, zero)
_else = else_ms.monomials.get(k, zero)
result.monomials[k] = Conditional(condition, _then, _else)
# Construct a deterministic ordering
result.ordering = then_ms.ordering.copy()
for k, v in else_ms.ordering.items():
result.ordering.setdefault(k, v)
return result
def test_conditional_zero_folding():
b = Variable("B", ())
a = Variable("A", (3, ))
i = Index()
expr = Conditional(LogicalAnd(b, b), Product(Indexed(a, (i, )), Zero()),
Zero())
assert expr == Zero()