def test_compose():
ordering = {'x': 0, 'y': 1, 'z': 2}
g = BDD(ordering)
# x & (x | z)
a = g.add_expr('x && y')
b = g.add_expr('x || z')
c = g.let({'y': b}, a)
d = g.add_expr('x && (x || z)')
assert c == d, (c, d)
# (y | z) & x
ordering = {'x': 0, 'y': 1, 'z': 2, 'w': 3}
g = BDD(ordering)
a = g.add_expr('(x && y) || z')
b = g.add_expr('(y || z) && x')
c = g.let({'z': b}, a)
assert c == b, (c, b)
# long expr
ordering = {'x': 0, 'y': 1, 'z': 2, 'w': 3}
g = BDD(ordering)
a = g.add_expr('(x && y) || (!z || (w && y && x))')
b = g.add_expr('(y || !z) && x')
c = g.let({'y': b}, a)
d = g.add_expr('(x && ((y || !z) && x)) ||'
' (!z || (w && ((y || !z) && x) && x))')
assert c == d, (c, d)
# complemented edges
ordering = {'x': 0, 'y': 1}
g = BDD(ordering)
f = g.add_expr('x <-> y')
var = 'y'
new_level = 0
var_node = g.find_or_add(new_level, -1, 1)
u = g.let({var: var_node}, f)
assert u == 1, g.to_expr(u)
def test_rename():
ordering = {'x': 0, 'xp': 1}
g = BDD(ordering)
x = g.add_expr('x')
xp = g.add_expr('xp')
dvars = {'x': 'xp'}
xrenamed = g.let(dvars, x)
assert xrenamed == xp, xrenamed
ordering = {'x': 0, 'xp': 1, 'y': 2, 'yp': 3, 'z': 4, 'zp': 5}
g = BDD(ordering)
u = g.add_expr('x && y && ! z')
dvars = {'x': 'xp', 'y': 'yp', 'z': 'zp'}
urenamed = g.let(dvars, u)
up = g.add_expr('xp && yp && ! zp')
assert urenamed == up, urenamed
# assertion violations
# non-neighbors
dvars = {'x': 'yp'}
r = g.let(dvars, u)
r_ = g.add_expr('yp && y && ! z')
assert r == r_, (r, r_)
# u not in bdd
dvars = {'x': 'xp'}
with nt.assert_raises(AssertionError):
g.let(dvars, 1000)
# y essential for u
dvars = {'xp': 'y'}
with nt.assert_raises(AssertionError):
g.let(dvars, u)
# old and new vars intersect
dvars = {'x': 'x'}
with nt.assert_raises(AssertionError):
g.let(dvars, u)
def test_cofactor():
ordering = {'x': 0, 'y': 1, 'z': 2}
g = BDD(ordering)
# u not in g
with nt.assert_raises(AssertionError):
g.let({'x': False, 'y': True, 'z': False}, 5)
# x & y
e = g.add_expr('x && y')
x = g.add_expr('x')
assert g.let({'x': False}, x) == -1
assert g.let({'x': True}, x) == 1
assert g.let({'x': False}, -x) == 1
assert g.let({'x': True}, -x) == -1
y = g.add_expr('y')
assert g.let({'x': True}, e) == y
assert g.let({'x': False}, e) == -1
assert g.let({'y': True}, e) == x
assert g.let({'y': False}, e) == -1
assert g.let({'x': False}, -e) == 1
assert g.let({'x': True}, -e) == -y
assert g.let({'y': False}, -e) == 1
assert g.let({'y': True}, -e) == -x