323 lines
16 KiB
Python
323 lines
16 KiB
Python
"""Most of these tests come from the examples in Bronstein's book."""
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from sympy.integrals.risch import DifferentialExtension, derivation
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from sympy.integrals.prde import (prde_normal_denom, prde_special_denom,
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prde_linear_constraints, constant_system, prde_spde, prde_no_cancel_b_large,
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prde_no_cancel_b_small, limited_integrate_reduce, limited_integrate,
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is_deriv_k, is_log_deriv_k_t_radical, parametric_log_deriv_heu,
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is_log_deriv_k_t_radical_in_field, param_poly_rischDE, param_rischDE,
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prde_cancel_liouvillian)
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from sympy.polys.polymatrix import PolyMatrix as Matrix
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from sympy.core.numbers import Rational
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from sympy.core.singleton import S
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from sympy.core.symbol import symbols
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from sympy.polys.domains.rationalfield import QQ
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from sympy.polys.polytools import Poly
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from sympy.abc import x, t, n
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t0, t1, t2, t3, k = symbols('t:4 k')
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def test_prde_normal_denom():
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1 + t**2, t)]})
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fa = Poly(1, t)
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fd = Poly(x, t)
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G = [(Poly(t, t), Poly(1 + t**2, t)), (Poly(1, t), Poly(x + x*t**2, t))]
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assert prde_normal_denom(fa, fd, G, DE) == \
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(Poly(x, t, domain='ZZ(x)'), (Poly(1, t, domain='ZZ(x)'), Poly(1, t,
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domain='ZZ(x)')), [(Poly(x*t, t, domain='ZZ(x)'),
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Poly(t**2 + 1, t, domain='ZZ(x)')), (Poly(1, t, domain='ZZ(x)'),
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Poly(t**2 + 1, t, domain='ZZ(x)'))], Poly(1, t, domain='ZZ(x)'))
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G = [(Poly(t, t), Poly(t**2 + 2*t + 1, t)), (Poly(x*t, t),
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Poly(t**2 + 2*t + 1, t)), (Poly(x*t**2, t), Poly(t**2 + 2*t + 1, t))]
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t, t)]})
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assert prde_normal_denom(Poly(x, t), Poly(1, t), G, DE) == \
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(Poly(t + 1, t), (Poly((-1 + x)*t + x, t), Poly(1, t, domain='ZZ[x]')), [(Poly(t, t),
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Poly(1, t)), (Poly(x*t, t), Poly(1, t, domain='ZZ[x]')), (Poly(x*t**2, t),
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Poly(1, t, domain='ZZ[x]'))], Poly(t + 1, t))
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def test_prde_special_denom():
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a = Poly(t + 1, t)
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ba = Poly(t**2, t)
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bd = Poly(1, t)
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G = [(Poly(t, t), Poly(1, t)), (Poly(t**2, t), Poly(1, t)), (Poly(t**3, t), Poly(1, t))]
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t, t)]})
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assert prde_special_denom(a, ba, bd, G, DE) == \
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(Poly(t + 1, t), Poly(t**2, t), [(Poly(t, t), Poly(1, t)),
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(Poly(t**2, t), Poly(1, t)), (Poly(t**3, t), Poly(1, t))], Poly(1, t))
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G = [(Poly(t, t), Poly(1, t)), (Poly(1, t), Poly(t, t))]
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assert prde_special_denom(Poly(1, t), Poly(t**2, t), Poly(1, t), G, DE) == \
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(Poly(1, t), Poly(t**2 - 1, t), [(Poly(t**2, t), Poly(1, t)),
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(Poly(1, t), Poly(1, t))], Poly(t, t))
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(-2*x*t0, t0)]})
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DE.decrement_level()
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G = [(Poly(t, t), Poly(t**2, t)), (Poly(2*t, t), Poly(t, t))]
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assert prde_special_denom(Poly(5*x*t + 1, t), Poly(t**2 + 2*x**3*t, t), Poly(t**3 + 2, t), G, DE) == \
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(Poly(5*x*t + 1, t), Poly(0, t, domain='ZZ[x]'), [(Poly(t, t), Poly(t**2, t)),
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(Poly(2*t, t), Poly(t, t))], Poly(1, x))
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly((t**2 + 1)*2*x, t)]})
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G = [(Poly(t + x, t), Poly(t*x, t)), (Poly(2*t, t), Poly(x**2, x))]
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assert prde_special_denom(Poly(5*x*t + 1, t), Poly(t**2 + 2*x**3*t, t), Poly(t**3, t), G, DE) == \
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(Poly(5*x*t + 1, t), Poly(0, t, domain='ZZ[x]'), [(Poly(t + x, t), Poly(x*t, t)),
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(Poly(2*t, t, x), Poly(x**2, t, x))], Poly(1, t))
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assert prde_special_denom(Poly(t + 1, t), Poly(t**2, t), Poly(t**3, t), G, DE) == \
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(Poly(t + 1, t), Poly(0, t, domain='ZZ[x]'), [(Poly(t + x, t), Poly(x*t, t)), (Poly(2*t, t, x),
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Poly(x**2, t, x))], Poly(1, t))
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def test_prde_linear_constraints():
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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G = [(Poly(2*x**3 + 3*x + 1, x), Poly(x**2 - 1, x)), (Poly(1, x), Poly(x - 1, x)),
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(Poly(1, x), Poly(x + 1, x))]
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assert prde_linear_constraints(Poly(1, x), Poly(0, x), G, DE) == \
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((Poly(2*x, x, domain='QQ'), Poly(0, x, domain='QQ'), Poly(0, x, domain='QQ')),
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Matrix([[1, 1, -1], [5, 1, 1]], x))
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G = [(Poly(t, t), Poly(1, t)), (Poly(t**2, t), Poly(1, t)), (Poly(t**3, t), Poly(1, t))]
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t, t)]})
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assert prde_linear_constraints(Poly(t + 1, t), Poly(t**2, t), G, DE) == \
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((Poly(t, t, domain='QQ'), Poly(t**2, t, domain='QQ'), Poly(t**3, t, domain='QQ')),
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Matrix(0, 3, [], t))
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G = [(Poly(2*x, t), Poly(t, t)), (Poly(-x, t), Poly(t, t))]
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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assert prde_linear_constraints(Poly(1, t), Poly(0, t), G, DE) == \
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((Poly(0, t, domain='QQ[x]'), Poly(0, t, domain='QQ[x]')), Matrix([[2*x, -x]], t))
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def test_constant_system():
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A = Matrix([[-(x + 3)/(x - 1), (x + 1)/(x - 1), 1],
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[-x - 3, x + 1, x - 1],
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[2*(x + 3)/(x - 1), 0, 0]], t)
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u = Matrix([[(x + 1)/(x - 1)], [x + 1], [0]], t)
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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R = QQ.frac_field(x)[t]
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assert constant_system(A, u, DE) == \
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(Matrix([[1, 0, 0],
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[0, 1, 0],
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[0, 0, 0],
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[0, 0, 1]], ring=R), Matrix([0, 1, 0, 0], ring=R))
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def test_prde_spde():
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D = [Poly(x, t), Poly(-x*t, t)]
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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# TODO: when bound_degree() can handle this, test degree bound from that too
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assert prde_spde(Poly(t, t), Poly(-1/x, t), D, n, DE) == \
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(Poly(t, t), Poly(0, t, domain='ZZ(x)'),
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[Poly(2*x, t, domain='ZZ(x)'), Poly(-x, t, domain='ZZ(x)')],
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[Poly(-x**2, t, domain='ZZ(x)'), Poly(0, t, domain='ZZ(x)')], n - 1)
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def test_prde_no_cancel():
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# b large
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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assert prde_no_cancel_b_large(Poly(1, x), [Poly(x**2, x), Poly(1, x)], 2, DE) == \
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([Poly(x**2 - 2*x + 2, x), Poly(1, x)], Matrix([[1, 0, -1, 0],
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[0, 1, 0, -1]], x))
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assert prde_no_cancel_b_large(Poly(1, x), [Poly(x**3, x), Poly(1, x)], 3, DE) == \
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([Poly(x**3 - 3*x**2 + 6*x - 6, x), Poly(1, x)], Matrix([[1, 0, -1, 0],
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[0, 1, 0, -1]], x))
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assert prde_no_cancel_b_large(Poly(x, x), [Poly(x**2, x), Poly(1, x)], 1, DE) == \
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([Poly(x, x, domain='ZZ'), Poly(0, x, domain='ZZ')], Matrix([[1, -1, 0, 0],
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[1, 0, -1, 0],
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[0, 1, 0, -1]], x))
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# b small
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# XXX: Is there a better example of a monomial with D.degree() > 2?
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t**3 + 1, t)]})
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# My original q was t**4 + t + 1, but this solution implies q == t**4
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# (c1 = 4), with some of the ci for the original q equal to 0.
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G = [Poly(t**6, t), Poly(x*t**5, t), Poly(t**3, t), Poly(x*t**2, t), Poly(1 + x, t)]
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R = QQ.frac_field(x)[t]
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assert prde_no_cancel_b_small(Poly(x*t, t), G, 4, DE) == \
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([Poly(t**4/4 - x/12*t**3 + x**2/24*t**2 + (Rational(-11, 12) - x**3/24)*t + x/24, t),
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Poly(x/3*t**3 - x**2/6*t**2 + (Rational(-1, 3) + x**3/6)*t - x/6, t), Poly(t, t),
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Poly(0, t), Poly(0, t)], Matrix([[1, 0, -1, 0, 0, 0, 0, 0, 0, 0],
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[0, 1, Rational(-1, 4), 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 1, 0, 0, 0, 0, 0, 0],
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[0, 0, 0, 0, 1, 0, 0, 0, 0, 0],
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[1, 0, 0, 0, 0, -1, 0, 0, 0, 0],
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[0, 1, 0, 0, 0, 0, -1, 0, 0, 0],
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[0, 0, 1, 0, 0, 0, 0, -1, 0, 0],
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[0, 0, 0, 1, 0, 0, 0, 0, -1, 0],
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[0, 0, 0, 0, 1, 0, 0, 0, 0, -1]], ring=R))
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# TODO: Add test for deg(b) <= 0 with b small
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1 + t**2, t)]})
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b = Poly(-1/x**2, t, field=True) # deg(b) == 0
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q = [Poly(x**i*t**j, t, field=True) for i in range(2) for j in range(3)]
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h, A = prde_no_cancel_b_small(b, q, 3, DE)
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V = A.nullspace()
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R = QQ.frac_field(x)[t]
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assert len(V) == 1
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assert V[0] == Matrix([Rational(-1, 2), 0, 0, 1, 0, 0]*3, ring=R)
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assert (Matrix([h])*V[0][6:, :])[0] == Poly(x**2/2, t, domain='QQ(x)')
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assert (Matrix([q])*V[0][:6, :])[0] == Poly(x - S.Half, t, domain='QQ(x)')
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def test_prde_cancel_liouvillian():
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### 1. case == 'primitive'
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# used when integrating f = log(x) - log(x - 1)
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# Not taken from 'the' book
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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p0 = Poly(0, t, field=True)
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p1 = Poly((x - 1)*t, t, domain='ZZ(x)')
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p2 = Poly(x - 1, t, domain='ZZ(x)')
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p3 = Poly(-x**2 + x, t, domain='ZZ(x)')
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h, A = prde_cancel_liouvillian(Poly(-1/(x - 1), t), [Poly(-x + 1, t), Poly(1, t)], 1, DE)
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V = A.nullspace()
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assert h == [p0, p0, p1, p0, p0, p0, p0, p0, p0, p0, p2, p3, p0, p0, p0, p0]
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assert A.rank() == 16
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assert (Matrix([h])*V[0][:16, :]) == Matrix([[Poly(0, t, domain='QQ(x)')]])
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### 2. case == 'exp'
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# used when integrating log(x/exp(x) + 1)
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# Not taken from book
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(-t, t)]})
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assert prde_cancel_liouvillian(Poly(0, t, domain='QQ[x]'), [Poly(1, t, domain='QQ(x)')], 0, DE) == \
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([Poly(1, t, domain='QQ'), Poly(x, t, domain='ZZ(x)')], Matrix([[-1, 0, 1]], DE.t))
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def test_param_poly_rischDE():
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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a = Poly(x**2 - x, x, field=True)
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b = Poly(1, x, field=True)
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q = [Poly(x, x, field=True), Poly(x**2, x, field=True)]
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h, A = param_poly_rischDE(a, b, q, 3, DE)
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assert A.nullspace() == [Matrix([0, 1, 1, 1], DE.t)] # c1, c2, d1, d2
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# Solution of a*Dp + b*p = c1*q1 + c2*q2 = q2 = x**2
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# is d1*h1 + d2*h2 = h1 + h2 = x.
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assert h[0] + h[1] == Poly(x, x, domain='QQ')
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# a*Dp + b*p = q1 = x has no solution.
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a = Poly(x**2 - x, x, field=True)
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b = Poly(x**2 - 5*x + 3, x, field=True)
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q = [Poly(1, x, field=True), Poly(x, x, field=True),
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Poly(x**2, x, field=True)]
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h, A = param_poly_rischDE(a, b, q, 3, DE)
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assert A.nullspace() == [Matrix([3, -5, 1, -5, 1, 1], DE.t)]
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p = -Poly(5, DE.t)*h[0] + h[1] + h[2] # Poly(1, x)
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assert a*derivation(p, DE) + b*p == Poly(x**2 - 5*x + 3, x, domain='QQ')
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def test_param_rischDE():
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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p1, px = Poly(1, x, field=True), Poly(x, x, field=True)
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G = [(p1, px), (p1, p1), (px, p1)] # [1/x, 1, x]
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h, A = param_rischDE(-p1, Poly(x**2, x, field=True), G, DE)
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assert len(h) == 3
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p = [hi[0].as_expr()/hi[1].as_expr() for hi in h]
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V = A.nullspace()
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assert len(V) == 2
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assert V[0] == Matrix([-1, 1, 0, -1, 1, 0], DE.t)
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y = -p[0] + p[1] + 0*p[2] # x
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assert y.diff(x) - y/x**2 == 1 - 1/x # Dy + f*y == -G0 + G1 + 0*G2
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# the below test computation takes place while computing the integral
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# of 'f = log(log(x + exp(x)))'
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t, t)]})
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G = [(Poly(t + x, t, domain='ZZ(x)'), Poly(1, t, domain='QQ')), (Poly(0, t, domain='QQ'), Poly(1, t, domain='QQ'))]
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h, A = param_rischDE(Poly(-t - 1, t, field=True), Poly(t + x, t, field=True), G, DE)
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assert len(h) == 5
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p = [hi[0].as_expr()/hi[1].as_expr() for hi in h]
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V = A.nullspace()
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assert len(V) == 3
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assert V[0] == Matrix([0, 0, 0, 0, 1, 0, 0], DE.t)
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y = 0*p[0] + 0*p[1] + 1*p[2] + 0*p[3] + 0*p[4]
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assert y.diff(t) - y/(t + x) == 0 # Dy + f*y = 0*G0 + 0*G1
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def test_limited_integrate_reduce():
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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assert limited_integrate_reduce(Poly(x, t), Poly(t**2, t), [(Poly(x, t),
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Poly(t, t))], DE) == \
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(Poly(t, t), Poly(-1/x, t), Poly(t, t), 1, (Poly(x, t), Poly(1, t, domain='ZZ[x]')),
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[(Poly(-x*t, t), Poly(1, t, domain='ZZ[x]'))])
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def test_limited_integrate():
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DE = DifferentialExtension(extension={'D': [Poly(1, x)]})
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G = [(Poly(x, x), Poly(x + 1, x))]
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assert limited_integrate(Poly(-(1 + x + 5*x**2 - 3*x**3), x),
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Poly(1 - x - x**2 + x**3, x), G, DE) == \
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((Poly(x**2 - x + 2, x), Poly(x - 1, x, domain='QQ')), [2])
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G = [(Poly(1, x), Poly(x, x))]
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assert limited_integrate(Poly(5*x**2, x), Poly(3, x), G, DE) == \
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((Poly(5*x**3/9, x), Poly(1, x, domain='QQ')), [0])
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def test_is_log_deriv_k_t_radical():
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DE = DifferentialExtension(extension={'D': [Poly(1, x)], 'exts': [None],
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'extargs': [None]})
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assert is_log_deriv_k_t_radical(Poly(2*x, x), Poly(1, x), DE) is None
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(2*t1, t1), Poly(1/x, t2)],
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'exts': [None, 'exp', 'log'], 'extargs': [None, 2*x, x]})
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assert is_log_deriv_k_t_radical(Poly(x + t2/2, t2), Poly(1, t2), DE) == \
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([(t1, 1), (x, 1)], t1*x, 2, 0)
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# TODO: Add more tests
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(t0, t0), Poly(1/x, t)],
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'exts': [None, 'exp', 'log'], 'extargs': [None, x, x]})
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assert is_log_deriv_k_t_radical(Poly(x + t/2 + 3, t), Poly(1, t), DE) == \
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([(t0, 2), (x, 1)], x*t0**2, 2, 3)
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def test_is_deriv_k():
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t1), Poly(1/(x + 1), t2)],
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'exts': [None, 'log', 'log'], 'extargs': [None, x, x + 1]})
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assert is_deriv_k(Poly(2*x**2 + 2*x, t2), Poly(1, t2), DE) == \
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([(t1, 1), (t2, 1)], t1 + t2, 2)
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t1), Poly(t2, t2)],
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'exts': [None, 'log', 'exp'], 'extargs': [None, x, x]})
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assert is_deriv_k(Poly(x**2*t2**3, t2), Poly(1, t2), DE) == \
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([(x, 3), (t1, 2)], 2*t1 + 3*x, 1)
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# TODO: Add more tests, including ones with exponentials
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(2/x, t1)],
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'exts': [None, 'log'], 'extargs': [None, x**2]})
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assert is_deriv_k(Poly(x, t1), Poly(1, t1), DE) == \
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([(t1, S.Half)], t1/2, 1)
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(2/(1 + x), t0)],
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'exts': [None, 'log'], 'extargs': [None, x**2 + 2*x + 1]})
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assert is_deriv_k(Poly(1 + x, t0), Poly(1, t0), DE) == \
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([(t0, S.Half)], t0/2, 1)
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# Issue 10798
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# DE = DifferentialExtension(log(1/x), x)
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(-1/x, t)],
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'exts': [None, 'log'], 'extargs': [None, 1/x]})
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assert is_deriv_k(Poly(1, t), Poly(x, t), DE) == ([(t, 1)], t, 1)
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def test_is_log_deriv_k_t_radical_in_field():
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# NOTE: any potential constant factor in the second element of the result
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# doesn't matter, because it cancels in Da/a.
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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assert is_log_deriv_k_t_radical_in_field(Poly(5*t + 1, t), Poly(2*t*x, t), DE) == \
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(2, t*x**5)
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assert is_log_deriv_k_t_radical_in_field(Poly(2 + 3*t, t), Poly(5*x*t, t), DE) == \
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(5, x**3*t**2)
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(-t/x**2, t)]})
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assert is_log_deriv_k_t_radical_in_field(Poly(-(1 + 2*t), t),
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Poly(2*x**2 + 2*x**2*t, t), DE) == \
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(2, t + t**2)
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assert is_log_deriv_k_t_radical_in_field(Poly(-1, t), Poly(x**2, t), DE) == \
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(1, t)
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assert is_log_deriv_k_t_radical_in_field(Poly(1, t), Poly(2*x**2, t), DE) == \
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(2, 1/t)
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def test_parametric_log_deriv():
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DE = DifferentialExtension(extension={'D': [Poly(1, x), Poly(1/x, t)]})
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assert parametric_log_deriv_heu(Poly(5*t**2 + t - 6, t), Poly(2*x*t**2, t),
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Poly(-1, t), Poly(x*t**2, t), DE) == \
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(2, 6, t*x**5)
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