def test_prob_negated_edge_basic_2():
r_expr = "a & ~(b | ~c)"
bdd = _bdd.BDD()
bdd.declare('a', 'b', 'c')
r = bdd.add_expr(r_expr)
x = {"a": 0.5, "b": 0.25, "c": 0.125}
assert (bdd_prob(bdd, r, x, dict()) == 0.046875)
def test_prob_negated_edge_basic():
r_expr = "a & ~b"
bdd = _bdd.BDD()
bdd.declare('a', 'b')
r = bdd.add_expr(r_expr)
x = {"a": 0.5, "b": 0.25}
assert (bdd_prob(bdd, r, x, dict()) == 0.375)
def risk_by_bdd(sg: SystemGraph, p, bdd_with_root=None):
if bdd_with_root is None:
bdd, root = build_bdd(sg)
else:
bdd, root = bdd_with_root
r = bdd_prob(bdd, root, p, dict())
return r
def test_prob_ex_rauzy_1():
vars = ["a", "c", "b"]
r_expr = "(a | c) & (b | c)"
bdd = _bdd.BDD()
bdd.declare(*vars)
r = bdd.add_expr(r_expr)
x = {v: 0.5 for v in vars}
assert bdd_prob(bdd, r, x, dict()) == .625
def test_prob_ex_sinnamon_1():
# pg 217, 1996 RAMS
vars = ["x1", "x2", "x3", "x4"]
bdd = _bdd.BDD()
bdd.declare(*vars)
r_expr = "ite(x1, ite(x2, ite(x3, TRUE, ite(x4, TRUE, FALSE)), ite(x3, TRUE, FALSE)), FALSE)"
r = bdd.add_expr(r_expr)
p = {"x1": 0.01, "x2": 0.02, "x3": 0.03, "x4": 0.04}
'''
minimal cutsets:
x1, x2, x3
x1, x2, x4
x1, x3
'''
assert pytest.approx(bdd_prob(bdd, r, p, dict()) == 3.0776e-4)
def test_prob_ex_nasa_1():
# NASA Fault Tree Handbook pp.VIII-12 - VIII-14
vars = ["T", "K_2", "S", "S_1", "K_1", "R"]
r_expr = "T | K_2 | (S & S_1) | (S & K_1) | (S & R)"
bdd = _bdd.BDD()
bdd.declare(*vars)
r = bdd.add_expr(r_expr)
x = {
"T": 5e-6,
"K_2": 3e-5,
"S": 1e-4,
"S_1": 3e-5,
"K_1": 3e-5,
"R": 1e-4
}
assert pytest.approx(bdd_prob(bdd, r, x, dict()) == 3.4e-5)