def test_composed_op():
from random import randrange
for N in range(100):
while 1:
D1 = randrange(10)
D2 = randrange(10)
F = fmpz_poly([randrange(-2, 3) for n in range(D1)])
G = fmpz_poly([randrange(-2, 3) for n in range(D2)])
if F.degree() >= 1 and G.degree() >= 1:
break
H = composed_op(F, G, operator.add)
for x, r in F.roots():
for y, r in G.roots():
v = H(x + y)
assert v.contains(0)
H = composed_op(F, G, operator.sub)
for x, r in F.roots():
for y, r in G.roots():
v = H(x - y)
assert v.contains(0)
H = composed_op(F, G, operator.mul)
for x, r in F.roots():
for y, r in G.roots():
v = H(x * y)
assert v.contains(0)
if G[0] != 0:
H = composed_op(F, G, operator.truediv)
for x, r in F.roots():
for y, r in G.roots():
v = H(x / y)
assert v.contains(0)
def __init__(self, v=0, _minpoly=None, _enclosure=None):
"""
An *alg* instance can be created from an existing *alg*
(this creates a copy), from a Python integer, or from
a FLINT *fmpz* or *fmpq*:
>>> alg(3)
3.00000 (deg 1)
>>> alg(alg(3))
3.00000 (deg 1)
>>> alg(fmpq(2,3))
0.666667 (deg 1)
It is also possible to create an *alg* instance *unsafely* from the
internal representation consisting of a minimal polynomial
and an enclosure:
>>> alg(_minpoly=fmpz_poly([-1,-1,1]), _enclosure=arb("1.618 +/- 0.001"))
1.61803 (deg 2)
The minimal polynomial must be an *fmpz_poly* that is irreducible and
normalized (no factors, GCD content removed, positive leading
coefficient), and the enclosure must isolate a unique root
of this polynomial. Warning: these properties are *not* checked.
Providing invalid input will silently produce wrong results
in subsequent computations.
"""
if _minpoly is not None:
assert type(_minpoly) == fmpz_poly
self._minpoly = _minpoly
self._enclosure = _enclosure
elif isinstance(v, (int, fmpz)):
self._minpoly = fmpz_poly([-v, 1])
self._enclosure = None
elif isinstance(v, fmpq):
self._minpoly = fmpz_poly([-v.p, v.q])
self._enclosure = None
elif isinstance(v, alg):
self._minpoly = v._minpoly
self._enclosure = v._enclosure
elif isinstance(v, float):
import math
m, e = math.frexp(v)
m = int(m * 2.0**53)
e -= 53
v = alg(m) * alg(2)**e
self._minpoly = v._minpoly
self._enclosure = v._enclosure
elif isinstance(v, complex):
v = alg(v.real) + alg(v.imag) * alg.i()
self._minpoly = v._minpoly
self._enclosure = v._enclosure
else:
raise NotImplementedError
self._hash = None
def root(self, n):
assert n >= 0
if n == 0:
raise ZeroDivisionError
if n == 1:
return self
F = self._minpoly
d = F.degree()
check_degree_limit(d * n)
H = [0] * (d * n + 1)
H[::n] = list(F)
H = fmpz_poly(H)
c, factors = H.factor()
prec = 64
orig_prec = ctx.prec
try:
while 1:
ctx.prec = prec
x = self.enclosure(pretty=True)
z = acb(x).root(n)
#if not z.imag == 0:
# eps = arb(0, z.rad())
# z += acb(eps,eps)
maybe_root = [
fac for fac, mult in factors if fac(z).contains(0)
]
if len(maybe_root) == 1:
fac = maybe_root[0]
z2 = alg._validate_root_enclosure(fac, z)
if z2 is not None:
return alg(_minpoly=fac, _enclosure=z2)
prec *= 2
finally:
ctx.prec = orig_prec
def pow(self, n):
if self.is_rational():
c0 = self._minpoly[0]
c1 = self._minpoly[1]
if abs(n) > 2:
check_bits_limit(c0.height_bits() * abs(n))
check_bits_limit(c1.height_bits() * abs(n))
if n >= 0:
return alg(fmpq(c0**n) / (-c1)**n)
else:
return alg((-c1)**(-n) / fmpq(c0**(-n)))
if n == 0:
return alg(1)
if n == 1:
return self
if n < 0:
return (1 / self).pow(-n)
# fast detection of perfect powers
pol, d = self.minpoly().deflation()
if d % n == 0:
# todo: is factoring needed here?
H = list(self.minpoly())
H = H[::n]
H = fmpz_poly(H)
c, factors = H.factor()
prec = 64
orig_prec = ctx.prec
try:
while 1:
ctx.prec = prec
x = self.enclosure(pretty=True)
z = acb(x)**n
maybe_root = [
fac for fac, mult in factors if fac(z).contains(0)
]
if len(maybe_root) == 1:
fac = maybe_root[0]
z2 = alg._validate_root_enclosure(fac, z)
if z2 is not None:
return alg(_minpoly=fac, _enclosure=z2)
prec *= 2
finally:
ctx.prec = orig_prec
if n == 2:
return self * self
v = self.pow(n // 2)
v = v * v
if n % 2:
v *= self
return v
def gaussian_integer(a, b):
if b == 0:
return alg(a)
a = fmpz(a)
b = fmpz(b)
orig = ctx.prec
ctx.prec = 64
try:
z = acb(a, b)
finally:
ctx.prec = orig
res = alg(_minpoly=fmpz_poly([a**2 + b**2, -2 * a, 1]), _enclosure=z)
return res
def test_sage_examples_slow(self):
if 0:
x = fmpz_poly([0, 1])
pol = x**10 + x**9 - x**7 - x**6 - x**5 - x**4 - x**3 + x + 1
root = arb("[1.17628081825991751 +/- 3.46e-18]")
alpha = alg(_minpoly=pol, _enclosure=root)
lhs = alpha**630 - 1
rhs_num = (alpha**315 - 1) * (alpha**210 - 1) * (
alpha**126 - 1)**2 * (alpha**90 - 1) * (alpha**3 - 1)**3 * (
alpha**2 - 1)**5 * (alpha - 1)**3
rhs_den = (alpha**35 - 1) * (alpha**15 - 1)**2 * (
alpha**14 - 1)**2 * (alpha**5 - 1)**6 * alpha**68
rhs = rhs_num / rhs_den
assert lhs == rhs
def test_sage_examples(self):
# from the sage qqbar docs
rt17 = alg(17).sqrt()
rt2 = alg(2).sqrt()
eps = (17 + rt17).sqrt()
epss = (17 - rt17).sqrt()
delta = rt17 - 1
alpha = (34 + 6 * rt17 + rt2 * delta * epss - 8 * rt2 * eps).sqrt()
beta = 2 * (17 + 3 * rt17 - 2 * rt2 * eps - rt2 * epss).sqrt()
x = rt2 * (15 + rt17 + rt2 * (alpha + epss)).sqrt() / 8
y = rt2 * (epss**2 - rt2 * (alpha + epss)).sqrt() / 8
cx, cy = alg(1), alg(0)
#for i in range(34): # slow
for i in range(3):
cx, cy = x * cx - y * cy, x * cy + y * cx
ax = fmpz_poly([0, 1])
x2 = alg.polynomial_roots(256 * ax**8 - 128 * ax**7 - 448 * ax**6 +
192 * ax**5 + 240 * ax**4 - 80 * ax**3 -
40 * ax**2 + 8 * ax + 1)[0][0]
y2 = (1 - x2**2).sqrt()
assert x == x2
assert y == y2
def imag(self):
if self.is_real():
return alg(0)
return (self - self.conjugate()) / alg(_minpoly=fmpz_poly([4, 0, 1]),
_enclosure=acb(0, 2))
def i():
return alg(_minpoly=fmpz_poly([1, 0, 1]), _enclosure=acb(0, 1))
def guess(z, deg=None, verbose=False, try_smaller=True, check=True):
"""
Use LLL to try to find an algebraic number matching the real or
complex enclosure *z* (given as a *flint.arb* or *flint.acb*).
Returns *None* if unsuccessful.
To determine the number of bits to use in the LLL matrix, the
algorithm accounts for the accuracy of the input as well as the
current Arb working precision (*flint.ctx.prec*).
The maximum degree is determined by the *deg* parameter.
By default the degree is set to roughly the square root of the working
precision.
If *try_smaller* is set, then the guessing is attempted recursively
with lower degree bounds to speed up detection of lower-degree
numbers.
If *check* is True (default), the algorithm verifies that the
result is contained in the complex interval *z*. (At high precision,
this reduces the likelihood of spurious results.)
"""
z = acb(z)
if not z.is_finite():
return None
if deg is None:
deg = max(1, int(ctx.prec**0.5))
if try_smaller and deg > 8:
g = alg.guess(z,
deg // 4,
verbose=verbose,
try_smaller=True,
check=check)
if g is not None:
return g
# todo: early detect exact (dyadic) real and imaginary parts?
# (avoid reliance on enclosure(pretty=True)
prec = ctx.prec
z = acb(z)
zpow = [z**i for i in range(deg + 1)]
magn = max(abs(t) for t in zpow)
if magn >= arb(2)**prec:
return None # too large
magnrad = max(abs(t.rad()) for t in zpow)
if magnrad >= 0.125:
return None # too imprecise
magnrad = max(2**(max(1, prec // 20)) * magnrad, arb(2)**(-2 * prec))
scale = 1 / magnrad
nonreal = z.imag != 0
A = fmpz_mat(deg + 1, deg + 2 + nonreal)
for i in range(deg + 1):
A[i, i] = 1
for i in range(deg + 1):
v = zpow[i] * scale
# fixme: don't use unique_fmpz
A[i, deg + 1] = v.real.mid().floor().unique_fmpz()
if nonreal:
A[i, deg + 2] = v.imag.mid().floor().unique_fmpz()
A = A.lll()
poly = fmpz_poly([A[0, i] for i in range(deg + 1)])
if verbose:
print("LLL-reduced matrix:")
print(A)
print("poly(z) =", poly(z))
if not check:
candidates = alg.polynomial_roots(poly) or [(alg(0), 1)]
return min([cand for (cand, mult) in candidates],
key=lambda x: abs(x.enclosure() - z).mid())
if not poly(z).contains(0):
return None
orig = ctx.prec
try:
candidates = alg.polynomial_roots(poly)
while ctx.prec <= 16 * orig:
for cand, mult in candidates:
r = cand.enclosure(pretty=True)
if z.contains(r):
return cand
ctx.prec *= 2
finally:
ctx.prec = orig
return None
