def test_collect_garbage():
# all nodes are garbage
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
n = len(g)
assert n == 4, n
uref = g._ref[abs(u)]
assert uref == 0, uref
_, v, w = g._succ[abs(u)]
vref = g._ref[abs(v)]
wref = g._ref[w]
assert vref == 5, vref
assert wref == 1, wref
g.collect_garbage()
n = len(g)
assert n == 1, n
assert u not in g, g._succ
assert w not in g, g._succ
# some nodes not garbage
# projection of x is garbage
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
n = len(g)
assert n == 4, n
g._ref[abs(u)] += 1
uref = g._ref[abs(u)]
assert uref == 1, uref
g.collect_garbage()
n = len(g)
assert n == 3, n
def test_collect_garbage():
# all nodes are garbage
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
n = len(g)
assert n == 4, n
uref = g._ref[abs(u)]
assert uref == 0, uref
_, v, w = g._succ[abs(u)]
vref = g._ref[abs(v)]
wref = g._ref[w]
assert vref == 5, vref
assert wref == 1, wref
g.collect_garbage()
n = len(g)
assert n == 1, n
assert u not in g, g._succ
assert w not in g, g._succ
# some nodes not garbage
# projection of x is garbage
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
n = len(g)
assert n == 4, n
g._ref[abs(u)] += 1
uref = g._ref[abs(u)]
assert uref == 1, uref
g.collect_garbage()
n = len(g)
assert n == 3, n
def test_sifting():
# Figs. 6.24, 6.25 Baier 2008
g = BDD({'z1': 0, 'z2': 1, 'z3': 2, 'y1': 3, 'y2': 4, 'y3': 5})
u = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
g.collect_garbage()
n = len(g)
assert n == 15, n
_bdd.reorder(g)
u_ = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
g.collect_garbage()
g.assert_consistent()
assert u == u_, (u, u_)
def test_sifting():
# Figs. 6.24, 6.25 Baier 2008
g = BDD({'z1': 0, 'z2': 1, 'z3': 2,
'y1': 3, 'y2': 4, 'y3': 5})
u = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
g.collect_garbage()
n = len(g)
assert n == 15, n
_bdd.reorder(g)
u_ = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
g.collect_garbage()
g.assert_consistent()
assert u == u_, (u, u_)
def test_swap():
# x, y
g = BDD({'x': 0, 'y': 1})
x = g.add_expr('x')
y = g.add_expr('y')
g.incref(x)
g.incref(y)
n = len(g)
assert n == 3, n
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'y': 0, 'x': 1}, g.ordering
assert g.assert_consistent()
# functions remain invariant
x_ = g.add_expr('x')
y_ = g.add_expr('y')
assert x == x_, (x, x_, g._succ)
assert y == y_, (y, y_, g._succ)
# external reference counts remain unchanged
assert g._ref[abs(x)] == 1
assert g._ref[abs(y)] == 1
# x & y
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
g.incref(u)
nold, n = g.swap('x', 'y')
assert nold == n, (nold, n)
assert g.ordering == {'y': 0, 'x': 1}, g.ordering
u_ = g.add_expr('x & y')
assert u == u_, (u, u_)
assert g.assert_consistent()
# reference counts unchanged
assert g._ref[abs(u)] == 1
# x & !y
# tests handling of complement edges
e = 'x & !y'
g = x_and_not_y()
u = g.add_expr(e)
g.incref(u)
g.collect_garbage()
n = len(g)
assert n == 3, n
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'x': 1, 'y': 0}
assert g.assert_consistent()
u_ = g.add_expr(e)
# function u must have remained unaffected
assert u_ == u, (u, u_, g._succ)
# invert swap of:
# x & !y
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'x': 0, 'y': 1}
assert g.assert_consistent()
u_ = g.add_expr(e)
assert u_ == u, (u, u_, g._succ)
# Figs. 6.24, 6.25 Baier 2008
g = BDD({'z1': 0, 'y1': 1, 'z2': 2, 'y2': 3, 'z3': 4, 'y3': 5})
u = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
n = len(g)
assert n == 16, n
g.collect_garbage()
n = len(g)
assert n == 7, n
# sift to inefficient order
g.swap('y1', 'z2') # z1, z2, y1, y2, z3, y3
g.swap('y2', 'z3') # z1, z2, y1, z3, y2, y3
g.swap('y1', 'z3') # z1, z2, z3, y1, y2, y3
n = len(g)
assert n == 15, n
assert g.assert_consistent()
new_ordering = {'z1': 0, 'z2': 1, 'z3': 2, 'y1': 3, 'y2': 4, 'y3': 5}
assert g.ordering == new_ordering, g.ordering
u_ = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
assert u_ == u, (u, u_, g._succ)
def test_swap():
# x, y
g = BDD({'x': 0, 'y': 1})
x = g.add_expr('x')
y = g.add_expr('y')
g.incref(x)
g.incref(y)
n = len(g)
assert n == 3, n
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'y': 0, 'x': 1}, g.ordering
assert g.assert_consistent()
# functions remain invariant
x_ = g.add_expr('x')
y_ = g.add_expr('y')
assert x == x_, (x, x_, g._succ)
assert y == y_, (y, y_, g._succ)
# external reference counts remain unchanged
assert g._ref[abs(x)] == 1
assert g._ref[abs(y)] == 1
# x & y
g = BDD({'x': 0, 'y': 1})
u = g.add_expr('x & y')
g.incref(u)
nold, n = g.swap('x', 'y')
assert nold == n, (nold, n)
assert g.ordering == {'y': 0, 'x': 1}, g.ordering
u_ = g.add_expr('x & y')
assert u == u_, (u, u_)
assert g.assert_consistent()
# reference counts unchanged
assert g._ref[abs(u)] == 1
# x & !y
# tests handling of complement edges
e = 'x & !y'
g = x_and_not_y()
u = g.add_expr(e)
g.incref(u)
g.collect_garbage()
n = len(g)
assert n == 3, n
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'x': 1, 'y': 0}
assert g.assert_consistent()
u_ = g.add_expr(e)
# function u must have remained unaffected
assert u_ == u, (u, u_, g._succ)
# invert swap of:
# x & !y
nold, n = g.swap('x', 'y')
assert n == 3, n
assert nold == n, nold
assert g.ordering == {'x': 0, 'y': 1}
assert g.assert_consistent()
u_ = g.add_expr(e)
assert u_ == u, (u, u_, g._succ)
# Figs. 6.24, 6.25 Baier 2008
g = BDD({'z1': 0, 'y1': 1, 'z2': 2,
'y2': 3, 'z3': 4, 'y3': 5})
u = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
g.incref(u)
n = len(g)
assert n == 16, n
g.collect_garbage()
n = len(g)
assert n == 7, n
# sift to inefficient order
g.swap('y1', 'z2') # z1, z2, y1, y2, z3, y3
g.swap('y2', 'z3') # z1, z2, y1, z3, y2, y3
g.swap('y1', 'z3') # z1, z2, z3, y1, y2, y3
n = len(g)
assert n == 15, n
assert g.assert_consistent()
new_ordering = {
'z1': 0, 'z2': 1, 'z3': 2,
'y1': 3, 'y2': 4, 'y3': 5}
assert g.ordering == new_ordering, g.ordering
u_ = g.add_expr('(z1 & y1) | (z2 & y2) | (z3 & y3)')
assert u_ == u, (u, u_, g._succ)
