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759 lines
26 KiB
759 lines
26 KiB
"""Tests for algorithms for computing symbolic roots of polynomials. """
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from sympy.core.numbers import (I, Rational, pi)
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from sympy.core.singleton import S
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from sympy.core.symbol import (Symbol, Wild, symbols)
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from sympy.functions.elementary.complexes import (conjugate, im, re)
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from sympy.functions.elementary.exponential import exp
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from sympy.functions.elementary.miscellaneous import (root, sqrt)
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from sympy.functions.elementary.piecewise import Piecewise
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from sympy.functions.elementary.trigonometric import (acos, cos, sin)
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from sympy.polys.domains.integerring import ZZ
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from sympy.sets.sets import Interval
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from sympy.simplify.powsimp import powsimp
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from sympy.polys import Poly, cyclotomic_poly, intervals, nroots, rootof
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from sympy.polys.polyroots import (root_factors, roots_linear,
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roots_quadratic, roots_cubic, roots_quartic, roots_quintic,
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roots_cyclotomic, roots_binomial, preprocess_roots, roots)
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from sympy.polys.orthopolys import legendre_poly
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from sympy.polys.polyerrors import PolynomialError, \
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UnsolvableFactorError
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from sympy.polys.polyutils import _nsort
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from sympy.testing.pytest import raises, slow
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from sympy.core.random import verify_numerically
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import mpmath
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from itertools import product
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a, b, c, d, e, q, t, x, y, z = symbols('a,b,c,d,e,q,t,x,y,z')
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def _check(roots):
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# this is the desired invariant for roots returned
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# by all_roots. It is trivially true for linear
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# polynomials.
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nreal = sum([1 if i.is_real else 0 for i in roots])
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assert sorted(roots[:nreal]) == list(roots[:nreal])
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for ix in range(nreal, len(roots), 2):
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if not (
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roots[ix + 1] == roots[ix] or
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roots[ix + 1] == conjugate(roots[ix])):
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return False
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return True
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def test_roots_linear():
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assert roots_linear(Poly(2*x + 1, x)) == [Rational(-1, 2)]
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def test_roots_quadratic():
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assert roots_quadratic(Poly(2*x**2, x)) == [0, 0]
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assert roots_quadratic(Poly(2*x**2 + 3*x, x)) == [Rational(-3, 2), 0]
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assert roots_quadratic(Poly(2*x**2 + 3, x)) == [-I*sqrt(6)/2, I*sqrt(6)/2]
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assert roots_quadratic(Poly(2*x**2 + 4*x + 3, x)) == [-1 - I*sqrt(2)/2, -1 + I*sqrt(2)/2]
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_check(Poly(2*x**2 + 4*x + 3, x).all_roots())
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f = x**2 + (2*a*e + 2*c*e)/(a - c)*x + (d - b + a*e**2 - c*e**2)/(a - c)
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assert roots_quadratic(Poly(f, x)) == \
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[-e*(a + c)/(a - c) - sqrt(a*b + c*d - a*d - b*c + 4*a*c*e**2)/(a - c),
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-e*(a + c)/(a - c) + sqrt(a*b + c*d - a*d - b*c + 4*a*c*e**2)/(a - c)]
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# check for simplification
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f = Poly(y*x**2 - 2*x - 2*y, x)
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assert roots_quadratic(f) == \
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[-sqrt(2*y**2 + 1)/y + 1/y, sqrt(2*y**2 + 1)/y + 1/y]
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f = Poly(x**2 + (-y**2 - 2)*x + y**2 + 1, x)
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assert roots_quadratic(f) == \
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[1,y**2 + 1]
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f = Poly(sqrt(2)*x**2 - 1, x)
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r = roots_quadratic(f)
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assert r == _nsort(r)
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# issue 8255
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f = Poly(-24*x**2 - 180*x + 264)
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assert [w.n(2) for w in f.all_roots(radicals=True)] == \
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[w.n(2) for w in f.all_roots(radicals=False)]
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for _a, _b, _c in product((-2, 2), (-2, 2), (0, -1)):
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f = Poly(_a*x**2 + _b*x + _c)
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roots = roots_quadratic(f)
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assert roots == _nsort(roots)
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def test_issue_7724():
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eq = Poly(x**4*I + x**2 + I, x)
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assert roots(eq) == {
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sqrt(I/2 + sqrt(5)*I/2): 1,
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sqrt(-sqrt(5)*I/2 + I/2): 1,
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-sqrt(I/2 + sqrt(5)*I/2): 1,
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-sqrt(-sqrt(5)*I/2 + I/2): 1}
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def test_issue_8438():
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p = Poly([1, y, -2, -3], x).as_expr()
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roots = roots_cubic(Poly(p, x), x)
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z = Rational(-3, 2) - I*7/2 # this will fail in code given in commit msg
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post = [r.subs(y, z) for r in roots]
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assert set(post) == \
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set(roots_cubic(Poly(p.subs(y, z), x)))
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# /!\ if p is not made an expression, this is *very* slow
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assert all(p.subs({y: z, x: i}).n(2, chop=True) == 0 for i in post)
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def test_issue_8285():
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roots = (Poly(4*x**8 - 1, x)*Poly(x**2 + 1)).all_roots()
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assert _check(roots)
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f = Poly(x**4 + 5*x**2 + 6, x)
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ro = [rootof(f, i) for i in range(4)]
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roots = Poly(x**4 + 5*x**2 + 6, x).all_roots()
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assert roots == ro
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assert _check(roots)
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# more than 2 complex roots from which to identify the
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# imaginary ones
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roots = Poly(2*x**8 - 1).all_roots()
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assert _check(roots)
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assert len(Poly(2*x**10 - 1).all_roots()) == 10 # doesn't fail
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def test_issue_8289():
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roots = (Poly(x**2 + 2)*Poly(x**4 + 2)).all_roots()
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assert _check(roots)
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roots = Poly(x**6 + 3*x**3 + 2, x).all_roots()
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assert _check(roots)
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roots = Poly(x**6 - x + 1).all_roots()
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assert _check(roots)
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# all imaginary roots with multiplicity of 2
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roots = Poly(x**4 + 4*x**2 + 4, x).all_roots()
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assert _check(roots)
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def test_issue_14291():
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assert Poly(((x - 1)**2 + 1)*((x - 1)**2 + 2)*(x - 1)
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).all_roots() == [1, 1 - I, 1 + I, 1 - sqrt(2)*I, 1 + sqrt(2)*I]
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p = x**4 + 10*x**2 + 1
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ans = [rootof(p, i) for i in range(4)]
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assert Poly(p).all_roots() == ans
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_check(ans)
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def test_issue_13340():
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eq = Poly(y**3 + exp(x)*y + x, y, domain='EX')
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roots_d = roots(eq)
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assert len(roots_d) == 3
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def test_issue_14522():
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eq = Poly(x**4 + x**3*(16 + 32*I) + x**2*(-285 + 386*I) + x*(-2824 - 448*I) - 2058 - 6053*I, x)
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roots_eq = roots(eq)
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assert all(eq(r) == 0 for r in roots_eq)
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def test_issue_15076():
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sol = roots_quartic(Poly(t**4 - 6*t**2 + t/x - 3, t))
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assert sol[0].has(x)
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def test_issue_16589():
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eq = Poly(x**4 - 8*sqrt(2)*x**3 + 4*x**3 - 64*sqrt(2)*x**2 + 1024*x, x)
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roots_eq = roots(eq)
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assert 0 in roots_eq
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def test_roots_cubic():
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assert roots_cubic(Poly(2*x**3, x)) == [0, 0, 0]
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assert roots_cubic(Poly(x**3 - 3*x**2 + 3*x - 1, x)) == [1, 1, 1]
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# valid for arbitrary y (issue 21263)
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r = root(y, 3)
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assert roots_cubic(Poly(x**3 - y, x)) == [r,
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r*(-S.Half + sqrt(3)*I/2),
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r*(-S.Half - sqrt(3)*I/2)]
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# simpler form when y is negative
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assert roots_cubic(Poly(x**3 - -1, x)) == \
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[-1, S.Half - I*sqrt(3)/2, S.Half + I*sqrt(3)/2]
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assert roots_cubic(Poly(2*x**3 - 3*x**2 - 3*x - 1, x))[0] == \
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S.Half + 3**Rational(1, 3)/2 + 3**Rational(2, 3)/2
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eq = -x**3 + 2*x**2 + 3*x - 2
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assert roots(eq, trig=True, multiple=True) == \
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roots_cubic(Poly(eq, x), trig=True) == [
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Rational(2, 3) + 2*sqrt(13)*cos(acos(8*sqrt(13)/169)/3)/3,
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-2*sqrt(13)*sin(-acos(8*sqrt(13)/169)/3 + pi/6)/3 + Rational(2, 3),
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-2*sqrt(13)*cos(-acos(8*sqrt(13)/169)/3 + pi/3)/3 + Rational(2, 3),
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]
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def test_roots_quartic():
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assert roots_quartic(Poly(x**4, x)) == [0, 0, 0, 0]
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assert roots_quartic(Poly(x**4 + x**3, x)) in [
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[-1, 0, 0, 0],
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[0, -1, 0, 0],
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[0, 0, -1, 0],
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[0, 0, 0, -1]
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]
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assert roots_quartic(Poly(x**4 - x**3, x)) in [
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[1, 0, 0, 0],
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[0, 1, 0, 0],
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[0, 0, 1, 0],
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[0, 0, 0, 1]
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]
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lhs = roots_quartic(Poly(x**4 + x, x))
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rhs = [S.Half + I*sqrt(3)/2, S.Half - I*sqrt(3)/2, S.Zero, -S.One]
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assert sorted(lhs, key=hash) == sorted(rhs, key=hash)
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# test of all branches of roots quartic
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for i, (a, b, c, d) in enumerate([(1, 2, 3, 0),
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(3, -7, -9, 9),
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(1, 2, 3, 4),
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(1, 2, 3, 4),
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(-7, -3, 3, -6),
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(-3, 5, -6, -4),
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(6, -5, -10, -3)]):
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if i == 2:
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c = -a*(a**2/S(8) - b/S(2))
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elif i == 3:
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d = a*(a*(a**2*Rational(3, 256) - b/S(16)) + c/S(4))
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eq = x**4 + a*x**3 + b*x**2 + c*x + d
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ans = roots_quartic(Poly(eq, x))
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assert all(eq.subs(x, ai).n(chop=True) == 0 for ai in ans)
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# not all symbolic quartics are unresolvable
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eq = Poly(q*x + q/4 + x**4 + x**3 + 2*x**2 - Rational(1, 3), x)
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sol = roots_quartic(eq)
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assert all(verify_numerically(eq.subs(x, i), 0) for i in sol)
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z = symbols('z', negative=True)
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eq = x**4 + 2*x**3 + 3*x**2 + x*(z + 11) + 5
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zans = roots_quartic(Poly(eq, x))
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assert all([verify_numerically(eq.subs(((x, i), (z, -1))), 0) for i in zans])
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# but some are (see also issue 4989)
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# it's ok if the solution is not Piecewise, but the tests below should pass
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eq = Poly(y*x**4 + x**3 - x + z, x)
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ans = roots_quartic(eq)
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assert all(type(i) == Piecewise for i in ans)
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reps = (
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{"y": Rational(-1, 3), "z": Rational(-1, 4)}, # 4 real
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{"y": Rational(-1, 3), "z": Rational(-1, 2)}, # 2 real
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{"y": Rational(-1, 3), "z": -2}) # 0 real
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for rep in reps:
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sol = roots_quartic(Poly(eq.subs(rep), x))
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assert all([verify_numerically(w.subs(rep) - s, 0) for w, s in zip(ans, sol)])
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def test_issue_21287():
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assert not any(isinstance(i, Piecewise) for i in roots_quartic(
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Poly(x**4 - x**2*(3 + 5*I) + 2*x*(-1 + I) - 1 + 3*I, x)))
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def test_roots_quintic():
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eqs = (x**5 - 2,
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(x/2 + 1)**5 - 5*(x/2 + 1) + 12,
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x**5 - 110*x**3 - 55*x**2 + 2310*x + 979)
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for eq in eqs:
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roots = roots_quintic(Poly(eq))
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assert len(roots) == 5
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assert all(eq.subs(x, r.n(10)).n(chop = 1e-5) == 0 for r in roots)
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def test_roots_cyclotomic():
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assert roots_cyclotomic(cyclotomic_poly(1, x, polys=True)) == [1]
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assert roots_cyclotomic(cyclotomic_poly(2, x, polys=True)) == [-1]
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assert roots_cyclotomic(cyclotomic_poly(
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3, x, polys=True)) == [Rational(-1, 2) - I*sqrt(3)/2, Rational(-1, 2) + I*sqrt(3)/2]
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assert roots_cyclotomic(cyclotomic_poly(4, x, polys=True)) == [-I, I]
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assert roots_cyclotomic(cyclotomic_poly(
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6, x, polys=True)) == [S.Half - I*sqrt(3)/2, S.Half + I*sqrt(3)/2]
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assert roots_cyclotomic(cyclotomic_poly(7, x, polys=True)) == [
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-cos(pi/7) - I*sin(pi/7),
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-cos(pi/7) + I*sin(pi/7),
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-cos(pi*Rational(3, 7)) - I*sin(pi*Rational(3, 7)),
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-cos(pi*Rational(3, 7)) + I*sin(pi*Rational(3, 7)),
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cos(pi*Rational(2, 7)) - I*sin(pi*Rational(2, 7)),
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cos(pi*Rational(2, 7)) + I*sin(pi*Rational(2, 7)),
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]
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assert roots_cyclotomic(cyclotomic_poly(8, x, polys=True)) == [
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-sqrt(2)/2 - I*sqrt(2)/2,
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-sqrt(2)/2 + I*sqrt(2)/2,
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sqrt(2)/2 - I*sqrt(2)/2,
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sqrt(2)/2 + I*sqrt(2)/2,
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]
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assert roots_cyclotomic(cyclotomic_poly(12, x, polys=True)) == [
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-sqrt(3)/2 - I/2,
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-sqrt(3)/2 + I/2,
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sqrt(3)/2 - I/2,
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sqrt(3)/2 + I/2,
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]
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assert roots_cyclotomic(
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cyclotomic_poly(1, x, polys=True), factor=True) == [1]
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assert roots_cyclotomic(
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cyclotomic_poly(2, x, polys=True), factor=True) == [-1]
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assert roots_cyclotomic(cyclotomic_poly(3, x, polys=True), factor=True) == \
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[-root(-1, 3), -1 + root(-1, 3)]
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assert roots_cyclotomic(cyclotomic_poly(4, x, polys=True), factor=True) == \
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[-I, I]
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assert roots_cyclotomic(cyclotomic_poly(5, x, polys=True), factor=True) == \
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[-root(-1, 5), -root(-1, 5)**3, root(-1, 5)**2, -1 - root(-1, 5)**2 + root(-1, 5) + root(-1, 5)**3]
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assert roots_cyclotomic(cyclotomic_poly(6, x, polys=True), factor=True) == \
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[1 - root(-1, 3), root(-1, 3)]
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def test_roots_binomial():
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assert roots_binomial(Poly(5*x, x)) == [0]
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assert roots_binomial(Poly(5*x**4, x)) == [0, 0, 0, 0]
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assert roots_binomial(Poly(5*x + 2, x)) == [Rational(-2, 5)]
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A = 10**Rational(3, 4)/10
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assert roots_binomial(Poly(5*x**4 + 2, x)) == \
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[-A - A*I, -A + A*I, A - A*I, A + A*I]
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_check(roots_binomial(Poly(x**8 - 2)))
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a1 = Symbol('a1', nonnegative=True)
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b1 = Symbol('b1', nonnegative=True)
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r0 = roots_quadratic(Poly(a1*x**2 + b1, x))
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r1 = roots_binomial(Poly(a1*x**2 + b1, x))
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assert powsimp(r0[0]) == powsimp(r1[0])
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assert powsimp(r0[1]) == powsimp(r1[1])
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for a, b, s, n in product((1, 2), (1, 2), (-1, 1), (2, 3, 4, 5)):
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if a == b and a != 1: # a == b == 1 is sufficient
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continue
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p = Poly(a*x**n + s*b)
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ans = roots_binomial(p)
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assert ans == _nsort(ans)
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# issue 8813
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assert roots(Poly(2*x**3 - 16*y**3, x)) == {
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2*y*(Rational(-1, 2) - sqrt(3)*I/2): 1,
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2*y: 1,
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2*y*(Rational(-1, 2) + sqrt(3)*I/2): 1}
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def test_roots_preprocessing():
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f = a*y*x**2 + y - b
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 1
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assert poly == Poly(a*y*x**2 + y - b, x)
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f = c**3*x**3 + c**2*x**2 + c*x + a
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 1/c
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assert poly == Poly(x**3 + x**2 + x + a, x)
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f = c**3*x**3 + c**2*x**2 + a
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 1/c
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assert poly == Poly(x**3 + x**2 + a, x)
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f = c**3*x**3 + c*x + a
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 1/c
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assert poly == Poly(x**3 + x + a, x)
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f = c**3*x**3 + a
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 1/c
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assert poly == Poly(x**3 + a, x)
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E, F, J, L = symbols("E,F,J,L")
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f = -21601054687500000000*E**8*J**8/L**16 + \
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508232812500000000*F*x*E**7*J**7/L**14 - \
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4269543750000000*E**6*F**2*J**6*x**2/L**12 + \
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16194716250000*E**5*F**3*J**5*x**3/L**10 - \
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27633173750*E**4*F**4*J**4*x**4/L**8 + \
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14840215*E**3*F**5*J**3*x**5/L**6 + \
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54794*E**2*F**6*J**2*x**6/(5*L**4) - \
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1153*E*J*F**7*x**7/(80*L**2) + \
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633*F**8*x**8/160000
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coeff, poly = preprocess_roots(Poly(f, x))
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assert coeff == 20*E*J/(F*L**2)
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assert poly == 633*x**8 - 115300*x**7 + 4383520*x**6 + 296804300*x**5 - 27633173750*x**4 + \
|
|
809735812500*x**3 - 10673859375000*x**2 + 63529101562500*x - 135006591796875
|
|
|
|
f = Poly(-y**2 + x**2*exp(x), y, domain=ZZ[x, exp(x)])
|
|
g = Poly(-y**2 + exp(x), y, domain=ZZ[exp(x)])
|
|
|
|
assert preprocess_roots(f) == (x, g)
|
|
|
|
|
|
def test_roots0():
|
|
assert roots(1, x) == {}
|
|
assert roots(x, x) == {S.Zero: 1}
|
|
assert roots(x**9, x) == {S.Zero: 9}
|
|
assert roots(((x - 2)*(x + 3)*(x - 4)).expand(), x) == {-S(3): 1, S(2): 1, S(4): 1}
|
|
|
|
assert roots(2*x + 1, x) == {Rational(-1, 2): 1}
|
|
assert roots((2*x + 1)**2, x) == {Rational(-1, 2): 2}
|
|
assert roots((2*x + 1)**5, x) == {Rational(-1, 2): 5}
|
|
assert roots((2*x + 1)**10, x) == {Rational(-1, 2): 10}
|
|
|
|
assert roots(x**4 - 1, x) == {I: 1, S.One: 1, -S.One: 1, -I: 1}
|
|
assert roots((x**4 - 1)**2, x) == {I: 2, S.One: 2, -S.One: 2, -I: 2}
|
|
|
|
assert roots(((2*x - 3)**2).expand(), x) == {Rational( 3, 2): 2}
|
|
assert roots(((2*x + 3)**2).expand(), x) == {Rational(-3, 2): 2}
|
|
|
|
assert roots(((2*x - 3)**3).expand(), x) == {Rational( 3, 2): 3}
|
|
assert roots(((2*x + 3)**3).expand(), x) == {Rational(-3, 2): 3}
|
|
|
|
assert roots(((2*x - 3)**5).expand(), x) == {Rational( 3, 2): 5}
|
|
assert roots(((2*x + 3)**5).expand(), x) == {Rational(-3, 2): 5}
|
|
|
|
assert roots(((a*x - b)**5).expand(), x) == { b/a: 5}
|
|
assert roots(((a*x + b)**5).expand(), x) == {-b/a: 5}
|
|
|
|
assert roots(x**2 + (-a - 1)*x + a, x) == {a: 1, S.One: 1}
|
|
|
|
assert roots(x**4 - 2*x**2 + 1, x) == {S.One: 2, S.NegativeOne: 2}
|
|
|
|
assert roots(x**6 - 4*x**4 + 4*x**3 - x**2, x) == \
|
|
{S.One: 2, -1 - sqrt(2): 1, S.Zero: 2, -1 + sqrt(2): 1}
|
|
|
|
assert roots(x**8 - 1, x) == {
|
|
sqrt(2)/2 + I*sqrt(2)/2: 1,
|
|
sqrt(2)/2 - I*sqrt(2)/2: 1,
|
|
-sqrt(2)/2 + I*sqrt(2)/2: 1,
|
|
-sqrt(2)/2 - I*sqrt(2)/2: 1,
|
|
S.One: 1, -S.One: 1, I: 1, -I: 1
|
|
}
|
|
|
|
f = -2016*x**2 - 5616*x**3 - 2056*x**4 + 3324*x**5 + 2176*x**6 - \
|
|
224*x**7 - 384*x**8 - 64*x**9
|
|
|
|
assert roots(f) == {S.Zero: 2, -S(2): 2, S(2): 1, Rational(-7, 2): 1,
|
|
Rational(-3, 2): 1, Rational(-1, 2): 1, Rational(3, 2): 1}
|
|
|
|
assert roots((a + b + c)*x - (a + b + c + d), x) == {(a + b + c + d)/(a + b + c): 1}
|
|
|
|
assert roots(x**3 + x**2 - x + 1, x, cubics=False) == {}
|
|
assert roots(((x - 2)*(
|
|
x + 3)*(x - 4)).expand(), x, cubics=False) == {-S(3): 1, S(2): 1, S(4): 1}
|
|
assert roots(((x - 2)*(x + 3)*(x - 4)*(x - 5)).expand(), x, cubics=False) == \
|
|
{-S(3): 1, S(2): 1, S(4): 1, S(5): 1}
|
|
assert roots(x**3 + 2*x**2 + 4*x + 8, x) == {-S(2): 1, -2*I: 1, 2*I: 1}
|
|
assert roots(x**3 + 2*x**2 + 4*x + 8, x, cubics=True) == \
|
|
{-2*I: 1, 2*I: 1, -S(2): 1}
|
|
assert roots((x**2 - x)*(x**3 + 2*x**2 + 4*x + 8), x ) == \
|
|
{S.One: 1, S.Zero: 1, -S(2): 1, -2*I: 1, 2*I: 1}
|
|
|
|
r1_2, r1_3 = S.Half, Rational(1, 3)
|
|
|
|
x0 = (3*sqrt(33) + 19)**r1_3
|
|
x1 = 4/x0/3
|
|
x2 = x0/3
|
|
x3 = sqrt(3)*I/2
|
|
x4 = x3 - r1_2
|
|
x5 = -x3 - r1_2
|
|
assert roots(x**3 + x**2 - x + 1, x, cubics=True) == {
|
|
-x1 - x2 - r1_3: 1,
|
|
-x1/x4 - x2*x4 - r1_3: 1,
|
|
-x1/x5 - x2*x5 - r1_3: 1,
|
|
}
|
|
|
|
f = (x**2 + 2*x + 3).subs(x, 2*x**2 + 3*x).subs(x, 5*x - 4)
|
|
|
|
r13_20, r1_20 = [ Rational(*r)
|
|
for r in ((13, 20), (1, 20)) ]
|
|
|
|
s2 = sqrt(2)
|
|
assert roots(f, x) == {
|
|
r13_20 + r1_20*sqrt(1 - 8*I*s2): 1,
|
|
r13_20 - r1_20*sqrt(1 - 8*I*s2): 1,
|
|
r13_20 + r1_20*sqrt(1 + 8*I*s2): 1,
|
|
r13_20 - r1_20*sqrt(1 + 8*I*s2): 1,
|
|
}
|
|
|
|
f = x**4 + x**3 + x**2 + x + 1
|
|
|
|
r1_4, r1_8, r5_8 = [ Rational(*r) for r in ((1, 4), (1, 8), (5, 8)) ]
|
|
|
|
assert roots(f, x) == {
|
|
-r1_4 + r1_4*5**r1_2 + I*(r5_8 + r1_8*5**r1_2)**r1_2: 1,
|
|
-r1_4 + r1_4*5**r1_2 - I*(r5_8 + r1_8*5**r1_2)**r1_2: 1,
|
|
-r1_4 - r1_4*5**r1_2 + I*(r5_8 - r1_8*5**r1_2)**r1_2: 1,
|
|
-r1_4 - r1_4*5**r1_2 - I*(r5_8 - r1_8*5**r1_2)**r1_2: 1,
|
|
}
|
|
|
|
f = z**3 + (-2 - y)*z**2 + (1 + 2*y - 2*x**2)*z - y + 2*x**2
|
|
|
|
assert roots(f, z) == {
|
|
S.One: 1,
|
|
S.Half + S.Half*y + S.Half*sqrt(1 - 2*y + y**2 + 8*x**2): 1,
|
|
S.Half + S.Half*y - S.Half*sqrt(1 - 2*y + y**2 + 8*x**2): 1,
|
|
}
|
|
|
|
assert roots(a*b*c*x**3 + 2*x**2 + 4*x + 8, x, cubics=False) == {}
|
|
assert roots(a*b*c*x**3 + 2*x**2 + 4*x + 8, x, cubics=True) != {}
|
|
|
|
assert roots(x**4 - 1, x, filter='Z') == {S.One: 1, -S.One: 1}
|
|
assert roots(x**4 - 1, x, filter='I') == {I: 1, -I: 1}
|
|
|
|
assert roots((x - 1)*(x + 1), x) == {S.One: 1, -S.One: 1}
|
|
assert roots(
|
|
(x - 1)*(x + 1), x, predicate=lambda r: r.is_positive) == {S.One: 1}
|
|
|
|
assert roots(x**4 - 1, x, filter='Z', multiple=True) == [-S.One, S.One]
|
|
assert roots(x**4 - 1, x, filter='I', multiple=True) == [I, -I]
|
|
|
|
ar, br = symbols('a, b', real=True)
|
|
p = x**2*(ar-br)**2 + 2*x*(br-ar) + 1
|
|
assert roots(p, x, filter='R') == {1/(ar - br): 2}
|
|
|
|
assert roots(x**3, x, multiple=True) == [S.Zero, S.Zero, S.Zero]
|
|
assert roots(1234, x, multiple=True) == []
|
|
|
|
f = x**6 - x**5 + x**4 - x**3 + x**2 - x + 1
|
|
|
|
assert roots(f) == {
|
|
-I*sin(pi/7) + cos(pi/7): 1,
|
|
-I*sin(pi*Rational(2, 7)) - cos(pi*Rational(2, 7)): 1,
|
|
-I*sin(pi*Rational(3, 7)) + cos(pi*Rational(3, 7)): 1,
|
|
I*sin(pi/7) + cos(pi/7): 1,
|
|
I*sin(pi*Rational(2, 7)) - cos(pi*Rational(2, 7)): 1,
|
|
I*sin(pi*Rational(3, 7)) + cos(pi*Rational(3, 7)): 1,
|
|
}
|
|
|
|
g = ((x**2 + 1)*f**2).expand()
|
|
|
|
assert roots(g) == {
|
|
-I*sin(pi/7) + cos(pi/7): 2,
|
|
-I*sin(pi*Rational(2, 7)) - cos(pi*Rational(2, 7)): 2,
|
|
-I*sin(pi*Rational(3, 7)) + cos(pi*Rational(3, 7)): 2,
|
|
I*sin(pi/7) + cos(pi/7): 2,
|
|
I*sin(pi*Rational(2, 7)) - cos(pi*Rational(2, 7)): 2,
|
|
I*sin(pi*Rational(3, 7)) + cos(pi*Rational(3, 7)): 2,
|
|
-I: 1, I: 1,
|
|
}
|
|
|
|
r = roots(x**3 + 40*x + 64)
|
|
real_root = [rx for rx in r if rx.is_real][0]
|
|
cr = 108 + 6*sqrt(1074)
|
|
assert real_root == -2*root(cr, 3)/3 + 20/root(cr, 3)
|
|
|
|
eq = Poly((7 + 5*sqrt(2))*x**3 + (-6 - 4*sqrt(2))*x**2 + (-sqrt(2) - 1)*x + 2, x, domain='EX')
|
|
assert roots(eq) == {-1 + sqrt(2): 1, -2 + 2*sqrt(2): 1, -sqrt(2) + 1: 1}
|
|
|
|
eq = Poly(41*x**5 + 29*sqrt(2)*x**5 - 153*x**4 - 108*sqrt(2)*x**4 +
|
|
175*x**3 + 125*sqrt(2)*x**3 - 45*x**2 - 30*sqrt(2)*x**2 - 26*sqrt(2)*x -
|
|
26*x + 24, x, domain='EX')
|
|
assert roots(eq) == {-sqrt(2) + 1: 1, -2 + 2*sqrt(2): 1, -1 + sqrt(2): 1,
|
|
-4 + 4*sqrt(2): 1, -3 + 3*sqrt(2): 1}
|
|
|
|
eq = Poly(x**3 - 2*x**2 + 6*sqrt(2)*x**2 - 8*sqrt(2)*x + 23*x - 14 +
|
|
14*sqrt(2), x, domain='EX')
|
|
assert roots(eq) == {-2*sqrt(2) + 2: 1, -2*sqrt(2) + 1: 1, -2*sqrt(2) - 1: 1}
|
|
|
|
assert roots(Poly((x + sqrt(2))**3 - 7, x, domain='EX')) == \
|
|
{-sqrt(2) + root(7, 3)*(-S.Half - sqrt(3)*I/2): 1,
|
|
-sqrt(2) + root(7, 3)*(-S.Half + sqrt(3)*I/2): 1,
|
|
-sqrt(2) + root(7, 3): 1}
|
|
|
|
def test_roots_slow():
|
|
"""Just test that calculating these roots does not hang. """
|
|
a, b, c, d, x = symbols("a,b,c,d,x")
|
|
|
|
f1 = x**2*c + (a/b) + x*c*d - a
|
|
f2 = x**2*(a + b*(c - d)*a) + x*a*b*c/(b*d - d) + (a*d - c/d)
|
|
|
|
assert list(roots(f1, x).values()) == [1, 1]
|
|
assert list(roots(f2, x).values()) == [1, 1]
|
|
|
|
(zz, yy, xx, zy, zx, yx, k) = symbols("zz,yy,xx,zy,zx,yx,k")
|
|
|
|
e1 = (zz - k)*(yy - k)*(xx - k) + zy*yx*zx + zx - zy - yx
|
|
e2 = (zz - k)*yx*yx + zx*(yy - k)*zx + zy*zy*(xx - k)
|
|
|
|
assert list(roots(e1 - e2, k).values()) == [1, 1, 1]
|
|
|
|
f = x**3 + 2*x**2 + 8
|
|
R = list(roots(f).keys())
|
|
|
|
assert not any(i for i in [f.subs(x, ri).n(chop=True) for ri in R])
|
|
|
|
|
|
def test_roots_inexact():
|
|
R1 = roots(x**2 + x + 1, x, multiple=True)
|
|
R2 = roots(x**2 + x + 1.0, x, multiple=True)
|
|
|
|
for r1, r2 in zip(R1, R2):
|
|
assert abs(r1 - r2) < 1e-12
|
|
|
|
f = x**4 + 3.0*sqrt(2.0)*x**3 - (78.0 + 24.0*sqrt(3.0))*x**2 \
|
|
+ 144.0*(2*sqrt(3.0) + 9.0)
|
|
|
|
R1 = roots(f, multiple=True)
|
|
R2 = (-12.7530479110482, -3.85012393732929,
|
|
4.89897948556636, 7.46155167569183)
|
|
|
|
for r1, r2 in zip(R1, R2):
|
|
assert abs(r1 - r2) < 1e-10
|
|
|
|
|
|
def test_roots_preprocessed():
|
|
E, F, J, L = symbols("E,F,J,L")
|
|
|
|
f = -21601054687500000000*E**8*J**8/L**16 + \
|
|
508232812500000000*F*x*E**7*J**7/L**14 - \
|
|
4269543750000000*E**6*F**2*J**6*x**2/L**12 + \
|
|
16194716250000*E**5*F**3*J**5*x**3/L**10 - \
|
|
27633173750*E**4*F**4*J**4*x**4/L**8 + \
|
|
14840215*E**3*F**5*J**3*x**5/L**6 + \
|
|
54794*E**2*F**6*J**2*x**6/(5*L**4) - \
|
|
1153*E*J*F**7*x**7/(80*L**2) + \
|
|
633*F**8*x**8/160000
|
|
|
|
assert roots(f, x) == {}
|
|
|
|
R1 = roots(f.evalf(), x, multiple=True)
|
|
R2 = [-1304.88375606366, 97.1168816800648, 186.946430171876, 245.526792947065,
|
|
503.441004174773, 791.549343830097, 1273.16678129348, 1850.10650616851]
|
|
|
|
w = Wild('w')
|
|
p = w*E*J/(F*L**2)
|
|
|
|
assert len(R1) == len(R2)
|
|
|
|
for r1, r2 in zip(R1, R2):
|
|
match = r1.match(p)
|
|
assert match is not None and abs(match[w] - r2) < 1e-10
|
|
|
|
|
|
def test_roots_strict():
|
|
assert roots(x**2 - 2*x + 1, strict=False) == {1: 2}
|
|
assert roots(x**2 - 2*x + 1, strict=True) == {1: 2}
|
|
|
|
assert roots(x**6 - 2*x**5 - x**2 + 3*x - 2, strict=False) == {2: 1}
|
|
raises(UnsolvableFactorError, lambda: roots(x**6 - 2*x**5 - x**2 + 3*x - 2, strict=True))
|
|
|
|
|
|
def test_roots_mixed():
|
|
f = -1936 - 5056*x - 7592*x**2 + 2704*x**3 - 49*x**4
|
|
|
|
_re, _im = intervals(f, all=True)
|
|
_nroots = nroots(f)
|
|
_sroots = roots(f, multiple=True)
|
|
|
|
_re = [ Interval(a, b) for (a, b), _ in _re ]
|
|
_im = [ Interval(re(a), re(b))*Interval(im(a), im(b)) for (a, b),
|
|
_ in _im ]
|
|
|
|
_intervals = _re + _im
|
|
_sroots = [ r.evalf() for r in _sroots ]
|
|
|
|
_nroots = sorted(_nroots, key=lambda x: x.sort_key())
|
|
_sroots = sorted(_sroots, key=lambda x: x.sort_key())
|
|
|
|
for _roots in (_nroots, _sroots):
|
|
for i, r in zip(_intervals, _roots):
|
|
if r.is_real:
|
|
assert r in i
|
|
else:
|
|
assert (re(r), im(r)) in i
|
|
|
|
|
|
def test_root_factors():
|
|
assert root_factors(Poly(1, x)) == [Poly(1, x)]
|
|
assert root_factors(Poly(x, x)) == [Poly(x, x)]
|
|
|
|
assert root_factors(x**2 - 1, x) == [x + 1, x - 1]
|
|
assert root_factors(x**2 - y, x) == [x - sqrt(y), x + sqrt(y)]
|
|
|
|
assert root_factors((x**4 - 1)**2) == \
|
|
[x + 1, x + 1, x - 1, x - 1, x - I, x - I, x + I, x + I]
|
|
|
|
assert root_factors(Poly(x**4 - 1, x), filter='Z') == \
|
|
[Poly(x + 1, x), Poly(x - 1, x), Poly(x**2 + 1, x)]
|
|
assert root_factors(8*x**2 + 12*x**4 + 6*x**6 + x**8, x, filter='Q') == \
|
|
[x, x, x**6 + 6*x**4 + 12*x**2 + 8]
|
|
|
|
|
|
@slow
|
|
def test_nroots1():
|
|
n = 64
|
|
p = legendre_poly(n, x, polys=True)
|
|
|
|
raises(mpmath.mp.NoConvergence, lambda: p.nroots(n=3, maxsteps=5))
|
|
|
|
roots = p.nroots(n=3)
|
|
# The order of roots matters. They are ordered from smallest to the
|
|
# largest.
|
|
assert [str(r) for r in roots] == \
|
|
['-0.999', '-0.996', '-0.991', '-0.983', '-0.973', '-0.961',
|
|
'-0.946', '-0.930', '-0.911', '-0.889', '-0.866', '-0.841',
|
|
'-0.813', '-0.784', '-0.753', '-0.720', '-0.685', '-0.649',
|
|
'-0.611', '-0.572', '-0.531', '-0.489', '-0.446', '-0.402',
|
|
'-0.357', '-0.311', '-0.265', '-0.217', '-0.170', '-0.121',
|
|
'-0.0730', '-0.0243', '0.0243', '0.0730', '0.121', '0.170',
|
|
'0.217', '0.265', '0.311', '0.357', '0.402', '0.446', '0.489',
|
|
'0.531', '0.572', '0.611', '0.649', '0.685', '0.720', '0.753',
|
|
'0.784', '0.813', '0.841', '0.866', '0.889', '0.911', '0.930',
|
|
'0.946', '0.961', '0.973', '0.983', '0.991', '0.996', '0.999']
|
|
|
|
def test_nroots2():
|
|
p = Poly(x**5 + 3*x + 1, x)
|
|
|
|
roots = p.nroots(n=3)
|
|
# The order of roots matters. The roots are ordered by their real
|
|
# components (if they agree, then by their imaginary components),
|
|
# with real roots appearing first.
|
|
assert [str(r) for r in roots] == \
|
|
['-0.332', '-0.839 - 0.944*I', '-0.839 + 0.944*I',
|
|
'1.01 - 0.937*I', '1.01 + 0.937*I']
|
|
|
|
roots = p.nroots(n=5)
|
|
assert [str(r) for r in roots] == \
|
|
['-0.33199', '-0.83907 - 0.94385*I', '-0.83907 + 0.94385*I',
|
|
'1.0051 - 0.93726*I', '1.0051 + 0.93726*I']
|
|
|
|
|
|
def test_roots_composite():
|
|
assert len(roots(Poly(y**3 + y**2*sqrt(x) + y + x, y, composite=True))) == 3
|
|
|
|
|
|
def test_issue_19113():
|
|
eq = cos(x)**3 - cos(x) + 1
|
|
raises(PolynomialError, lambda: roots(eq))
|
|
|
|
|
|
def test_issue_17454():
|
|
assert roots([1, -3*(-4 - 4*I)**2/8 + 12*I, 0], multiple=True) == [0, 0]
|
|
|
|
|
|
def test_issue_20913():
|
|
assert Poly(x + 9671406556917067856609794, x).real_roots() == [-9671406556917067856609794]
|
|
assert Poly(x**3 + 4, x).real_roots() == [-2**(S(2)/3)]
|
|
|
|
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def test_issue_22768():
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e = Rational(1, 3)
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r = (-1/a)**e*(a + 1)**(5*e)
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assert roots(Poly(a*x**3 + (a + 1)**5, x)) == {
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r: 1,
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-r*(1 + sqrt(3)*I)/2: 1,
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r*(-1 + sqrt(3)*I)/2: 1}
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