Esempio n. 1
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 def assertIsReduced(t, m_path, x_name, eps_name):
     M = fuchsia.import_matrix_from_file(m_path)
     x = SR.var(x_name)
     eps = SR.var(eps_name)
     pranks = fuchsia.singularities(M, x).values()
     t.assertEqual(pranks, [0]*len(pranks))
     t.assertTrue(eps not in (M/eps).simplify_rational().variables())
Esempio n. 2
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    def test_normalize_3(t):
        # Test with non-zero normalized eigenvalues
        x = SR.var("x")
        e = SR.var("epsilon")
        M = matrix([[(1 - e) / x, 0], [0, (1 + e) / 3 / x]])

        with t.assertRaises(FuchsiaError):
            N, T = normalize(M, x, e)
Esempio n. 3
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 def test_factorize_1(t):
     x = SR.var("x")
     e = SR.var("epsilon")
     M = matrix([[1 / x, 0, 0], [0, 2 / x, 0], [0, 0, 3 / x]]) * e
     M = transform(M, x, matrix([[1, 1, 0], [0, 1, 0], [1 + 2 * e, 0, e]]))
     F, T = factorize(M, x, e)
     F = F.simplify_rational()
     for f in F.list():
         t.assertEqual(limit_fixed(f, e, 0), 0)
Esempio n. 4
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 def test_is_normalized_1(t):
     x = SR.var("x")
     e = SR.var("epsilon")
     t.assertFalse(is_normalized(matrix([[1 / x / 2]]), x, e))
     t.assertFalse(is_normalized(matrix([[-1 / x / 2]]), x, e))
     t.assertTrue(is_normalized(matrix([[1 / x / 3]]), x, e))
     t.assertFalse(is_normalized(matrix([[x]]), x, e))
     t.assertFalse(is_normalized(matrix([[1 / x**2]]), x, e))
     t.assertTrue (is_normalized( \
             matrix([[(e+SR(1)/3)/x-SR(1)/2/(x-1)]]), x, e))
Esempio n. 5
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    def test_normalize_1(t):
        # Test with apparent singularities at 0 and oo, but not at 1.
        x = SR.var("x")
        M = matrix([[1 / x, 5 / (x - 1), 0, 6 / (x - 1)], [0, 2 / x, 0, 0],
                    [0, 0, 3 / x, 7 / (x - 1)], [6 / (x - 1), 0, 0, 1 / x]])

        N, T = normalize(M, x, SR.var("epsilon"))
        N = N.simplify_rational()
        t.assertEqual(N, transform(M, x, T).simplify_rational())
        for point, prank in singularities(N, x).iteritems():
            R = matrix_c0(N, x, point, prank)
            evlist = R.eigenvalues()
            t.assertEqual(evlist, [0] * len(evlist))
Esempio n. 6
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    def place_list(self, mx, Mx, frac=1, mark_origin=True):
        """
        return a tuple of 
        1. values that are all the integer multiple of 
                <frac>*self.numerical_value 
            between mx and Mx
        2. the multiple of the basis unit.

        Give <frac> as literal real. Recall that python evaluates 1/2 to 0. If you pass 0.5, it will be converted back to 1/2 for a nice display.
        """
        try:
            # If the user enters "0.5", it is converted to 1/2
            frac = Rational(frac)
        except TypeError:
            pass
        if frac == 0:
            raise ValueError(
                "frac is zero in AxesUnit.place_list(). Maybe you ignore that python evaluates 1/2 to 0 ? (writes literal 0.5 instead) \n Or are you trying to push me in an infinite loop ?"
            )
        l = []
        k = SR.var("TheTag")
        for x in MultipleBetween(frac * self.numerical_value, mx, Mx,
                                 mark_origin):
            if self.latex_symbol == "":
                l.append((x, "$" + latex(x) + "$"))
            else:
                pos = (x / self.numerical_value) * k
                # This risks to be Sage-version dependent.
                text = "$" + latex(pos).replace("TheTag",
                                                self.latex_symbol) + "$"
                l.append((x, text))
        return l
Esempio n. 7
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 def __init__(self,dof,name,shortname=None):
   
   self.dof = int(dof)
   self.name = name
   if shortname == None :
     self.shortname = name.replace(' ','_').replace('.','_')
   else :
     self.shortname = shortname.replace(' ','_').replace('.','_')
   
   for i in range(1 ,1 +dof):
     var('q'+str(i),domain=RR)
   
   
   (alpha , a , d , theta) = SR.var('alpha,a,d,theta',domain=RR)
   default_params_dh = [ alpha , a , d , theta  ]
   default_T_dh = matrix( \
   [[ cos(theta), -sin(theta)*cos(alpha), sin(theta)*sin(alpha), a*cos(theta) ], \
   [ sin(theta), cos(theta)*cos(alpha), -cos(theta)*sin(alpha), a*sin(theta) ], \
   [ 0.0, sin(alpha), cos(alpha), d ]
   ,[ 0.0, 0.0, 0.0, 1.0] ] )
   
   #g_a = SR.var('g_a',domain=RR)
   g_a = 9.81
   self.grav = matrix([[0.0],[0.0],[-g_a]])
   
   self.params_dh = default_params_dh
   self.T_dh = default_T_dh
   
   self.links_dh = []
   
   self.motors = []
   self.Imzi = []
   
   self._gensymbols()
Esempio n. 8
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    def test_normalize_4(t):
        # Test with non-zero normalized eigenvalues
        x, e = SR.var("x eps")
        M = matrix([[1 / x / 2, 0], [0, 0]])

        with t.assertRaises(FuchsiaError):
            N, T = normalize(M, x, e)
Esempio n. 9
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    def assertReductionWorks(t, filename):
        M = import_matrix_from_file(filename)
        x, eps = SR.var("x eps")
        t.assertIn(x, M.variables())
        M_pranks = singularities(M, x).values()
        t.assertNotEqual(M_pranks, [0] * len(M_pranks))

        #1 Fuchsify
        m, t1 = simplify_by_factorization(M, x)
        Mf, t2 = fuchsify(m, x)
        Tf = t1 * t2
        t.assertTrue((Mf - transform(M, x, Tf)).simplify_rational().is_zero())
        Mf_pranks = singularities(Mf, x).values()
        t.assertEqual(Mf_pranks, [0] * len(Mf_pranks))

        #2 Normalize
        t.assertFalse(is_normalized(Mf, x, eps))
        m, t1 = simplify_by_factorization(Mf, x)
        Mn, t2 = normalize(m, x, eps)
        Tn = t1 * t2
        t.assertTrue((Mn - transform(Mf, x, Tn)).simplify_rational().is_zero())
        t.assertTrue(is_normalized(Mn, x, eps))

        #3 Factorize
        t.assertIn(eps, Mn.variables())
        m, t1 = simplify_by_factorization(Mn, x)
        Mc, t2 = factorize(m, x, eps, seed=3)
        Tc = t1 * t2
        t.assertTrue((Mc - transform(Mn, x, Tc)).simplify_rational().is_zero())
        t.assertNotIn(eps, (Mc / eps).simplify_rational().variables())
Esempio n. 10
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    def test_reduce_at_one_point_1(t):
        x = SR.var("x")
        M0 = matrix([[1 / x, 4, 0, 5], [0, 2 / x, 0, 0], [0, 0, 3 / x, 6],
                     [0, 0, 0, 4 / x]])

        u = matrix([[0, Rational((3, 5)),
                     Rational((4, 5)), 0],
                    [Rational((5, 13)), 0, 0,
                     Rational((12, 13))]])
        M1 = transform(M0, x, balance(u.transpose() * u, 0, 1, x))
        M1 = M1.simplify_rational()

        u = matrix([[8, 0, 15, 0]]) / 17
        M2 = transform(M1, x, balance(u.transpose() * u, 0, 2, x))
        M2 = M2.simplify_rational()

        M2_sing = singularities(M2, x)
        t.assertIn(0, M2_sing)
        t.assertEqual(M2_sing[0], 2)

        M3, T23 = reduce_at_one_point(M2, x, 0, 2)
        M3 = M3.simplify_rational()
        t.assertEqual(M3, transform(M2, x, T23).simplify_rational())

        M3_sing = singularities(M3, x)
        t.assertIn(0, M3_sing)
        t.assertEqual(M3_sing[0], 1)

        M4, T34 = reduce_at_one_point(M3, x, 0, 1)
        M4 = M4.simplify_rational()
        t.assertEqual(M4, transform(M3, x, T34).simplify_rational())

        M4_sing = singularities(M4, x)
        t.assertIn(0, M4_sing)
        t.assertEqual(M4_sing[0], 0)
Esempio n. 11
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 def test_import_export_mathematica(t):
     a, b = SR.var("v1 v2")
     M = matrix([[1, a, b], [a + b, Rational((2, 3)), a / b]])
     fout = StringIO()
     export_matrix_mathematica(fout, M)
     MM = import_matrix_mathematica(StringIO(fout.getvalue()))
     t.assertEqual(M, MM)
Esempio n. 12
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def taylor_processor_factored(new_ring, Phi, scalar, alpha, I, omega):
    k = alpha.nrows() - 1
    tau = SR.var('tau')
    y = [SR('y%d' % i) for i in range(k + 1)]

    R = PolynomialRing(QQ, len(y), y)
    beta = [a * Phi for a in alpha]

    ell = len(I)

    def f(i):
        if i == 0:
            return QQ(scalar) * y[0] * exp(tau * omega[0])
        elif i in I:
            return tau / (1 - exp(tau * omega[i]))
        else:
            return 1 / (1 - y[i] * exp(tau * omega[i]))

    H = [
        f(i).series(tau, ell + 1).truncate().collect(tau) for i in range(k + 1)
    ]

    for i in range(k + 1):
        H[i] = [H[i].coefficient(tau, j) for j in range(ell + 1)]

    r = []

    # Get coefficient of tau^ell in prod(H)

    for w in NonnegativeCompositions(ell, k + 1):
        r = prod(
            CyclotomicRationalFunction.from_split_expression(H[i][
                w[i]], y, R).monomial_substitution(new_ring, beta)
            for i in range(k + 1))
        yield r
Esempio n. 13
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    def padically_evaluate_regular(self, datum):
        T = datum.toric_datum
        if not T.is_regular():
            raise ValueError('Can only processed regular toric data')

        M = Set(range(T.length()))
        q = SR.var('q')

        alpha = {}

        for I in Subsets(M):
            F = [T.initials[i] for i in I]
            V = SubvarietyOfTorus(F, torus_dim=T.ambient_dim)
            alpha[I] = V.count()

        def cat(u, v):
            return vector(list(u) + list(v))

        for I in Subsets(M):
            cnt = sum((-1)**len(J) * alpha[I + J] for J in Subsets(M - I))
            if not cnt:
                continue

            P = DirectProductOfPolyhedra(T.polyhedron,
                                         StrictlyPositiveOrthant(len(I)))

            it = iter(identity_matrix(ZZ, len(I)).rows())
            ieqs = []
            for i in M:
                ieqs.append(
                    cat(
                        vector(ZZ, (0, )),
                        cat(
                            vector(ZZ, T.initials[i].exponents()[0]) -
                            vector(ZZ, T.lhs[i].exponents()[0]),
                            next(it) if i in I else zero_vector(ZZ, len(I)))))

            if not ieqs:
                ieqs = [vector(ZZ, (T.ambient_dim + len(I) + 1) * [0])]

            Q = Polyhedron(ieqs=ieqs,
                           base_ring=QQ,
                           ambient_dim=T.ambient_dim + len(I))

            foo, ring = symbolic_to_ratfun(
                cnt * (q - 1)**len(I) / q**(T.ambient_dim),
                [var('t'), var('q')])
            corr_cnt = CyclotomicRationalFunction.from_laurent_polynomial(
                foo, ring)

            Phi = matrix([
                cat(T.integrand[0], zero_vector(ZZ, len(I))),
                cat(T.integrand[1], vector(ZZ,
                                           len(I) * [-1]))
            ]).transpose()
            sm = RationalSet([P.intersection(Q)]).generating_function()
            for z in sm.monomial_substitution(QQ['t', 'q'], Phi):
                yield corr_cnt * z
Esempio n. 14
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 def test_transform_2(t):
     # transform(transform(M, x, I), x, I^-1) == M
     x = SR.var("x")
     M = randpolym(x, 2)
     T = randpolym(x, 2)
     invT = T.inverse()
     M1 = transform(M, x, T)
     M2 = transform(M1, x, invT)
     t.assertEqual(M2.simplify_rational(), M)
Esempio n. 15
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 def test_fuchsify_by_blocks_03(test):
     x, eps = SR.var("x eps")
     m = matrix([
         [eps / x, 0, 0],
         [1 / x**2, 2 * eps / x, 0],
         [1 / x**2, 2 / x**2, 3 * eps / x],
     ])
     b = [(0, 1), (1, 1), (2, 1)]
     test.assert_fuchsify_by_blocks_works(m, b, x, eps)
Esempio n. 16
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 def test_fuchsify_by_blocks_05(test):
     x, eps = SR.var("x eps")
     m = matrix([
         [eps / x, 0, 0],
         [0, 2 * eps / x, -eps / x],
         [x**2, 0, 3 * eps / x],
     ])
     b = [(0, 1), (1, 2)]
     test.assert_fuchsify_by_blocks_works(m, b, x, eps)
Esempio n. 17
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    def test_normalize_5(t):
        # An unnormalizable example by A. A. Bolibrukh
        x, e = SR.var("x eps")
        b = import_matrix_from_file("test/data/bolibrukh.mtx")
        f, ft = fuchsify(b, x)
        f_pranks = singularities(f, x).values()
        t.assertEqual(f_pranks, [0] * len(f_pranks))

        with t.assertRaises(FuchsiaError):
            n, nt = normalize(f, x, e)
Esempio n. 18
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    def get_background_graphic(self, **bdry_options):
        r"""
        Return a graphic object that makes the model easier to visualize.
        For the hyperboloid model, the background object is the hyperboloid
        itself.

        EXAMPLES::

            sage: H = HyperbolicPlane().HM().get_background_graphic()
        """
        from sage.plot.plot3d.all import plot3d
        from sage.all import SR
        hyperboloid_opacity = bdry_options.get('hyperboloid_opacity', .1)
        z_height = bdry_options.get('z_height', 7.0)
        x_max = sqrt((z_height ** 2 - 1) / 2.0)
        x = SR.var('x')
        y = SR.var('y')
        return plot3d((1 + x ** 2 + y ** 2).sqrt(),
                      (x, -x_max, x_max), (y,-x_max, x_max),
                      opacity=hyperboloid_opacity, **bdry_options)
Esempio n. 19
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    def get_background_graphic(self, **bdry_options):
        r"""
        Return a graphic object that makes the model easier to visualize.
        For the hyperboloid model, the background object is the hyperboloid
        itself.

        EXAMPLES::

            sage: H = HyperbolicPlane().HM().get_background_graphic()
        """
        from sage.plot.plot3d.all import plot3d
        from sage.all import SR
        hyperboloid_opacity = bdry_options.get('hyperboloid_opacity', .1)
        z_height = bdry_options.get('z_height', 7.0)
        x_max = sqrt((z_height ** 2 - 1) / 2.0)
        x = SR.var('x')
        y = SR.var('y')
        return plot3d((1 + x ** 2 + y ** 2).sqrt(),
                      (x, -x_max, x_max), (y,-x_max, x_max),
                      opacity=hyperboloid_opacity, **bdry_options)
Esempio n. 20
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 def test_balance_2(t):
     # balance(P, x1, oo, x)*balance(P, oo, x1, x) == I
     x = SR.var("x")
     P = matrix([[1, 1], [0, 0]])
     x1 = randint(-10, 10)
     b1 = balance(P, x1, oo, x)
     b2 = balance(P, oo, x1, x)
     t.assertEqual((b1 * b2).simplify_rational(),
                   identity_matrix(P.nrows()))
     t.assertEqual((b2 * b1).simplify_rational(),
                   identity_matrix(P.nrows()))
Esempio n. 21
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 def test_fuchsify_by_blocks_06(test):
     x, eps = SR.var("x eps")
     m = matrix(
         [[eps / (x - 1), 0, 0],
          [(x**3 + x**2 - 3 * x - 3) / (2 * x**3 - 2 * x**2 - x + 1),
           2 * eps / (x - 3), 0],
          [
              -(x**3 + 3 * x**2 - 3 * x + 2) / (2 * x**3 + x**2 - 2 * x) +
              2 * (x**3 - x**2 - x + 1) / (2 * x + 1),
              -3 * (x**3 + x - 1) / (3 * x**3 + x - 2), 4 * eps / (x - 5)
          ]])
     b = [(0, 1), (1, 1), (2, 1)]
     test.assert_fuchsify_by_blocks_works(m, b, x, eps)
Esempio n. 22
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    def assertReductionWorks(test, filename, fuchsian=False):
        m = import_matrix_from_file(filename)
        x, eps = SR.var("x eps")
        test.assertIn(x, m.variables())

        if not fuchsian:
            m_pranks = singularities(m, x).values()
            test.assertNotEqual(m_pranks, [0]*len(m_pranks))

        mt, t = epsilon_form(m, x, eps)
        test.assertTrue((mt-transform(m, x, t)).simplify_rational().is_zero())
        test.assertTrue(is_fuchsian(mt, x))
        test.assertTrue(is_normalized(mt, x, eps))
        test.assertNotIn(eps, (mt/eps).simplify_rational().variables())
Esempio n. 23
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 def test_block_triangular_form_3(t):
     m = matrix([
       [1, 0, 1, 0],
       [0, 1, 0, 1],
       [1, 0, 1, 0],
       [0, 0, 0, 1]
     ])
     mt, tt, b = block_triangular_form(m)
     x = SR.var("dummy")
     t.assertEqual(mt, transform(m, x, tt))
     t.assertEqual(matrix([
       [1, 1, 0, 0],
       [1, 1, 0, 0],
       [0, 0, 1, 0],
       [0, 0, 1, 1]
     ]), mt)
Esempio n. 24
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    def assertNormalizeBlocksWorks(test, filename):
        x, eps = SR.var("x eps")

        m = import_matrix_from_file(filename)
        test.assertIn(x, m.variables())
        test.assertIn(eps, m.variables())
        test.assertFalse(is_normalized(m, x, eps))

        m_pranks = singularities(m, x).values()
        test.assertNotEqual(m_pranks, [0] * len(m_pranks))

        m, t, b = block_triangular_form(m)
        mt, tt = reduce_diagonal_blocks(m, x, eps, b=b)
        t = t * tt
        test.assertTrue(
            (mt - transform(m, x, t)).simplify_rational().is_zero())
        test.assertTrue(are_diagonal_blocks_reduced(mt, b, x, eps))
Esempio n. 25
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 def test_simplify_by_jordanification(t):
     x = SR.var("x")
     M = matrix(
         [[4 / (x + 1), -1 / (6 * x * (x + 1)), -1 / (3 * x * (x + 1))],
          [
              6 * (13 * x + 6) / (x * (x + 1)),
              -5 * (x + 3) / (3 * x * (x + 1)),
              2 * (x - 6) / (3 * x * (x + 1))
          ],
          [
              -63 * (x - 1) / (x * (x + 1)),
              (5 * x - 9) / (6 * x * (x + 1)), -(x - 18) / (3 * x * (x + 1))
          ]]).simplify_rational()
     MM, T = simplify_by_jordanification(M, x)
     MM = MM.simplify_rational()
     t.assertEqual(MM, transform(M, x, T).simplify_rational())
     t.assertLess(matrix_complexity(MM), matrix_complexity(M))
Esempio n. 26
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    def test_fuchsify_2(t):
        x = SR.var("x")
        M = matrix([[0, 1 / x / (x - 1), 0, 0], [0, 0, 0, 0], [0, 0, 0, 0],
                    [0, 0, 0, 0]])
        u = matrix([[6, 3, 2, 0]]) / 7
        P = u.transpose() * u
        M = balance_transform(M, P, 1, 0, x).simplify_rational()
        M = balance_transform(M, P, 1, 0, x).simplify_rational()
        M = balance_transform(M, P, 1, 0, x).simplify_rational()
        M = balance_transform(M, P, 1, 0, x).simplify_rational()
        M = balance_transform(M, P, 1, 0, x).simplify_rational()

        MM, T = fuchsify(M, x)
        MM = MM.simplify_rational()
        t.assertEqual(MM, transform(M, x, T).simplify_rational())

        pranks = singularities(MM, x).values()
        t.assertEqual(pranks, [0] * len(pranks))
Esempio n. 27
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    def test_balance_transform_1(t):
        x = SR.var("x")
        M = randpolym(x, 2)
        P = matrix([[1, 1], [0, 0]])
        x1 = randint(-10, 10)
        x2 = randint(20, 30)
        b1 = balance(P, x1, x2, x)

        M1 = balance_transform(M, P, x1, x2, x)
        M2 = transform(M, x, balance(P, x1, x2, x))
        t.assertEqual(M1.simplify_rational(), M2.simplify_rational())

        M1 = balance_transform(M, P, x1, oo, x)
        M2 = transform(M, x, balance(P, x1, oo, x))
        t.assertEqual(M1.simplify_rational(), M2.simplify_rational())

        M1 = balance_transform(M, P, oo, x2, x)
        M2 = transform(M, x, balance(P, oo, x2, x))
        t.assertEqual(M1.simplify_rational(), M2.simplify_rational())
Esempio n. 28
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    def test_fuchsify_1(t):
        x = SR.var("x")
        M = matrix([[1 / x, 5, 0, 6], [0, 2 / x, 0, 0], [0, 0, 3 / x, 7],
                    [0, 0, 0, 4 / x]])

        u = matrix([[0, Rational((3, 5)),
                     Rational((4, 5)), 0],
                    [Rational((5, 13)), 0, 0,
                     Rational((12, 13))]])
        M = transform(M, x, balance(u.transpose() * u, 0, 1, x))
        M = M.simplify_rational()

        u = matrix([[8, 0, 15, 0]]) / 17
        M = transform(M, x, balance(u.transpose() * u, 0, 2, x))
        M = M.simplify_rational()

        Mx, T = fuchsify(M, x)
        Mx = Mx.simplify_rational()
        t.assertEqual(Mx, transform(M, x, T).simplify_rational())

        pranks = singularities(Mx, x).values()
        t.assertEqual(pranks, [0] * len(pranks))
Esempio n. 29
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def taylor_processor_naive(new_ring, Phi, scalar, alpha, I, omega):
    k = alpha.nrows() - 1
    tau = SR.var('tau')
    y = [SR('y%d' % i) for i in range(k + 1)]

    R = PolynomialRing(QQ, len(y), y)
    beta = [a * Phi for a in alpha]

    def f(i):
        if i == 0:
            return QQ(scalar) * y[0] * exp(tau * omega[0])
        elif i in I:
            return 1 / (1 - exp(tau * omega[i]))
        else:
            return 1 / (1 - y[i] * exp(tau * omega[i]))

    h = prod(f(i) for i in range(k + 1))

    # Get constant term of h as a Laurent series in tau.
    g = h.series(tau, 1).truncate().collect(tau).coefficient(tau, 0)
    g = g.factor() if g else g
    yield CyclotomicRationalFunction.from_split_expression(
        g, y, R).monomial_substitution(new_ring, beta)
Esempio n. 30
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 def test_block_triangular_form_4(t):
     M = matrix([
       [1, 2, 3, 0, 0, 0],
       [4, 5, 6, 0, 0, 0],
       [7, 8, 9, 0, 0, 0],
       [2, 0, 0, 1, 2, 0],
       [0, 2, 0, 3, 4, 0],
       [0, 0, 2, 0, 0, 1]
     ])
     x = SR.var("dummy")
     T = matrix.identity(6)[random.sample(xrange(6), 6),:]
     M = transform(M, x, T)
     MM, T, B = block_triangular_form(M)
     t.assertEqual(MM, transform(M, x, T))
     t.assertEqual(sorted(s for o, s in B), [1, 2, 3])
     for o, s in B:
         for i in xrange(s):
             for j in xrange(s):
                 MM[o + i, o + j] = 0
     for i in xrange(6):
         for j in xrange(i):
             MM[i, j] = 0
     t.assertEqual(MM, matrix(6))
Esempio n. 31
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 def test_fuchsify_by_blocks_07(test):
     x, eps = SR.var("x ep")
     m = matrix([[0, 0], [1 / (x**2 - x + 1)**2, 0]])
     b = [(0, 1), (1, 1)]
     test.assert_fuchsify_by_blocks_works(m, b, x, eps)
Esempio n. 32
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def elliptic_cm_form(E, n, prec, aplist_only=False, anlist_only=False):
    """
    Return q-expansion of the CM modular form associated to the n-th
    power of the Grossencharacter associated to the elliptic curve E.

    INPUT:
        - E -- CM elliptic curve
        - n -- positive integer
        - prec -- positive integer
        - aplist_only -- return list only of ap for p prime
        - anlist_only -- return list only of an

    OUTPUT:
        - power series with integer coefficients

    EXAMPLES::

        sage: from psage.modform.rational.special import elliptic_cm_form
        sage: f = CuspForms(121,4).newforms(names='a')[0]; f
        q + 8*q^3 - 8*q^4 + 18*q^5 + O(q^6)
        sage: E = EllipticCurve('121b')
        sage: elliptic_cm_form(E, 3, 7)
        q + 8*q^3 - 8*q^4 + 18*q^5 + O(q^7)
        sage: g = elliptic_cm_form(E, 3, 100)
        sage: g == f.q_expansion(100)
        True
    """
    if not E.has_cm():
        raise ValueError, "E must have CM"
    n = ZZ(n)
    if n <= 0:
        raise ValueError, "n must be positive"

    prec = ZZ(prec)
    if prec <= 0:
        return []
    elif prec <= 1:
        return [ZZ(0)]
    elif prec <= 2:
        return [ZZ(0), ZZ(1)]
    
    # Derive formula for sum of n-th powers of roots
    a,p,T = SR.var('a,p,T')
    roots = (T**2 - a*T + p).roots(multiplicities=False)
    s = sum(alpha**n for alpha in roots).simplify_full()
    
    # Create fast callable expression from formula
    g = fast_callable(s.polynomial(ZZ))

    # Compute aplist for the curve
    v = E.aplist(prec)

    # Use aplist to compute ap values for the CM form attached to n-th
    # power of Grossencharacter.
    P = prime_range(prec)

    if aplist_only:
        # case when we only want the a_p (maybe for computing an
        # L-series via Euler product)
        return [g(ap,p) for ap,p in zip(v,P)]

    # Default cause where we want all a_n
    anlist = [ZZ(0),ZZ(1)] + [None]*(prec-2)
    for ap,p in zip(v,P):
        anlist[p] = g(ap,p)

    # Fill in the prime power a_{p^r} for r >= 2.
    N = E.conductor()
    for p in P:
        prm2 = 1
        prm1 = p
        pr = p*p
        pn = p**n
        e = 1 if N%p else 0
        while pr < prec:
            anlist[pr] = anlist[prm1] * anlist[p]
            if e:
                anlist[pr] -= pn * anlist[prm2]
            prm2 = prm1
            prm1 = pr
            pr *= p

    # fill in a_n with n divisible by at least 2 primes
    extend_multiplicatively_generic(anlist)

    if anlist_only:
        return anlist

    f = Integer_list_to_polynomial(anlist, 'q')
    return ZZ[['q']](f, prec=prec)