def find_opts(expr):
if not isinstance(expr, Basic):
return
if expr.is_Atom:
return
if isinstance(expr, CSE_NO_DESCEND_CLASSES):
return
if iterable(expr):
for item in expr:
find_opts(item)
return
if expr in seen_subexp:
return expr
seen_subexp.add(expr)
for arg in expr.args:
find_opts(arg)
if _coeff_isneg(expr):
neg_expr = -expr
if not neg_expr.is_Atom:
opt_subs[expr] = Unevaluated(Mul, (-1, neg_expr))
seen_subexp.add(neg_expr)
expr = neg_expr
if isinstance(expr, Mul):
muls.add(expr)
elif isinstance(expr, Add):
adds.add(expr)
elif isinstance(expr, Pow):
base, exp = expr.args
if _coeff_isneg(exp):
opt_subs[expr] = Unevaluated(Pow, (Pow(base, -exp), -1))
def test_nested_substitution():
# Substitution within a substitution.
e = Add(Pow(w*x + y, 2), sqrt(w*x + y))
substs, reduced = cse([e])
assert substs == [(x0, w*x + y)]
assert reduced == [sqrt(x0) + x0**2]
def test_cse_single():
# Simple substitution.
e = Add(Pow(x + y, 2), sqrt(x + y))
substs, reduced = cse([e])
assert substs == [(x0, x + y)]
assert reduced == [sqrt(x0) + x0**2]