def _build(self) -> None:
"""Build Cayley graph and store it in self.G.
"""
self._G = nx.MultiDiGraph()
# Compute solutions to the four squares decomposition problem and
# retain only the ones eligible for the LPS construction.
four_squares = set(
[
s for x in power_representation(self.p, 2, 4, zeros=True)
for s in signed_permutations(x) if self.eligible_solution(s)
]
)
i = self.find_square_root(-1)
# One extra vertex for the infinity point
for x in range(self.q+1):
self._G.add_node(x)
for x in range(self.q):
for (a, b, c, d) in four_squares:
num = ((a + i*b) * x + c + i*d) % self.q
den = ((i*d - c) * x + a - i*b) % self.q
if den == 0:
self._G.add_edge(x, self.infinity_point)
else:
self._G.add_edge(x, num * self.modular_inv(den))
# Finally add the links from the infinity point
for (a, b, c, d) in four_squares:
num = (a + i*b) % self.q
den = (i*d - c) % self.q
if den == 0:
self._G.add_edge(
self.infinity_point, self.infinity_point
)
else:
self._G.add_edge(
self.infinity_point, num * self.modular_inv(den)
)
if self.remove_parallel_edges:
self._G = nx.Graph(self._G)
if self.remove_self_edges:
self._G.remove_edges_from(self._G.selfloop_edges())
else:
self._G = nx.MultiDiGraph(self._G)
def test_power_representation():
tests = [(1729, 3, 2), (234, 2, 4), (2, 1, 2), (3, 1, 3), (5, 2, 2), (12352, 2, 4),
(32760, 2, 3)]
for test in tests:
n, p, k = test
f = power_representation(n, p, k)
while True:
try:
l = next(f)
assert len(l) == k
chk_sum = 0
for l_i in l:
chk_sum = chk_sum + l_i**p
assert chk_sum == n
except StopIteration:
break
def test_power_representation():
tests = [(1729, 3, 2), (234, 2, 4), (2, 1, 2), (3, 1, 3), (5, 2, 2),
(12352, 2, 4), (32760, 2, 3)]
for test in tests:
n, p, k = test
f = power_representation(n, p, k)
while True:
try:
l = next(f)
assert len(l) == k
chk_sum = 0
for l_i in l:
chk_sum = chk_sum + l_i**p
assert chk_sum == n
except StopIteration:
break
def test_power_representation():
tests = [(1729, 3, 2), (234, 2, 4), (2, 1, 2), (3, 1, 3), (5, 2, 2),
(12352, 2, 4), (32760, 2, 3)]
for test in tests:
n, p, k = test
f = power_representation(n, p, k)
while True:
try:
l = next(f)
assert len(l) == k
chk_sum = 0
for l_i in l:
chk_sum = chk_sum + l_i**p
assert chk_sum == n
except StopIteration:
break
assert list(power_representation(20, 2, 4, True)) == \
[(1, 1, 3, 3), (0, 0, 2, 4)]
raises(ValueError, lambda: list(power_representation(1.2, 2, 2)))
raises(ValueError, lambda: list(power_representation(2, 0, 2)))
raises(ValueError, lambda: list(power_representation(2, 2, 0)))
assert list(power_representation(-1, 2, 2)) == []
assert list(power_representation(1, 1, 1)) == [(1, )]
assert list(power_representation(3, 2, 1)) == []
assert list(power_representation(4, 2, 1)) == [(2, )]
assert list(power_representation(3**4, 4, 6, zeros=True)) == \
[(1, 2, 2, 2, 2, 2), (0, 0, 0, 0, 0, 3)]
assert list(power_representation(3**4, 4, 5, zeros=False)) == []
assert list(power_representation(-2, 3, 2)) == [(-1, -1)]
assert list(power_representation(-2, 4, 2)) == []
assert list(power_representation(0, 3, 2, True)) == [(0, 0)]
assert list(power_representation(0, 3, 2, False)) == []
# when we are dealing with squares, do feasibility checks
assert len(list(power_representation(4**10 * (8 * 10 + 7), 2, 3))) == 0
# there will be a recursion error if these aren't recognized
big = 2**30
for i in [13, 10, 7, 5, 4, 2, 1]:
assert list(sum_of_powers(big, 2, big - i)) == []
def test_power_representation():
tests = [(1729, 3, 2), (234, 2, 4), (2, 1, 2), (3, 1, 3), (5, 2, 2), (12352, 2, 4),
(32760, 2, 3)]
for test in tests:
n, p, k = test
f = power_representation(n, p, k)
while True:
try:
l = next(f)
assert len(l) == k
chk_sum = 0
for l_i in l:
chk_sum = chk_sum + l_i**p
assert chk_sum == n
except StopIteration:
break
assert list(power_representation(20, 2, 4, True)) == \
[(1, 1, 3, 3), (0, 0, 2, 4)]
raises(ValueError, lambda: list(power_representation(1.2, 2, 2)))
raises(ValueError, lambda: list(power_representation(2, 0, 2)))
raises(ValueError, lambda: list(power_representation(2, 2, 0)))
assert list(power_representation(-1, 2, 2)) == []
assert list(power_representation(1, 1, 1)) == [(1,)]
assert list(power_representation(3, 2, 1)) == []
assert list(power_representation(4, 2, 1)) == [(2,)]
assert list(power_representation(3**4, 4, 6, zeros=True)) == \
[(1, 2, 2, 2, 2, 2), (0, 0, 0, 0, 0, 3)]
assert list(power_representation(3**4, 4, 5, zeros=False)) == []
assert list(power_representation(-2, 3, 2)) == [(-1, -1)]
assert list(power_representation(-2, 4, 2)) == []
assert list(power_representation(0, 3, 2, True)) == [(0, 0)]
assert list(power_representation(0, 3, 2, False)) == []
# when we are dealing with squares, do feasibility checks
assert len(list(power_representation(4**10*(8*10 + 7), 2, 3))) == 0
# there will be a recursion error if these aren't recognized
big = 2**30
for i in [13, 10, 7, 5, 4, 2, 1]:
assert list(sum_of_powers(big, 2, big - i)) == []