def roots_cyclotomic(f, factor=False): """Compute roots of cyclotomic polynomials. """ L, U = _inv_totient_estimate(f.degree()) for n in xrange(L, U + 1): g = cyclotomic_poly(n, f.gen, polys=True) if f == g: break else: # pragma: no cover raise RuntimeError("failed to find index of a cyclotomic polynomial") roots = [] if not factor: for k in xrange(1, n + 1): if igcd(k, n) == 1: roots.append(exp(2*k*S.Pi*I/n).expand(complex=True)) else: g = Poly(f, extension=(-1)**Rational(1, n)) for h, _ in g.factor_list()[1]: roots.append(-h.TC()) return sorted(roots, key=default_sort_key)
def roots_cyclotomic(f, factor=False): """Compute roots of cyclotomic polynomials. """ L, U = _inv_totient_estimate(f.degree()) for n in range(L, U + 1): g = cyclotomic_poly(n, f.gen, polys=True) if f == g: break else: # pragma: no cover raise RuntimeError("failed to find index of a cyclotomic polynomial") roots = [] if not factor: # get the indices in the right order so the computed # roots will be sorted h = n//2 ks = [i for i in range(1, n + 1) if igcd(i, n) == 1] ks.sort(key=lambda x: (x, -1) if x <= h else (abs(x - n), 1)) d = 2*I*pi/n for k in reversed(ks): roots.append(exp(k*d).expand(complex=True)) else: g = Poly(f, extension=root(-1, n)) for h, _ in ordered(g.factor_list()[1]): roots.append(-h.TC()) return roots
def roots_cyclotomic(f, factor=False): """Compute roots of cyclotomic polynomials. """ L, U = _inv_totient_estimate(f.degree()) for n in xrange(L, U + 1): g = cyclotomic_poly(n, f.gen, polys=True) if f == g: break else: # pragma: no cover raise RuntimeError("failed to find index of a cyclotomic polynomial") roots = [] if not factor: for k in xrange(1, n + 1): if igcd(k, n) == 1: roots.append(exp(2 * k * S.Pi * I / n).expand(complex=True)) else: g = Poly(f, extension=(-1)**Rational(1, n)) for h, _ in g.factor_list()[1]: roots.append(-h.TC()) return sorted(roots, key=default_sort_key)
def _minpoly_pow(ex, pw, x, dom, mp=None): """ Returns ``minpoly(ex**pw, x)`` Parameters ========== ex : algebraic element pw : rational number x : indeterminate of the polynomial dom: ground domain mp : minimal polynomial of ``p`` Examples ======== >>> from sympy import sqrt, QQ, Rational >>> from sympy.polys.numberfields.minpoly import _minpoly_pow, minpoly >>> from sympy.abc import x, y >>> p = sqrt(1 + sqrt(2)) >>> _minpoly_pow(p, 2, x, QQ) x**2 - 2*x - 1 >>> minpoly(p**2, x) x**2 - 2*x - 1 >>> _minpoly_pow(y, Rational(1, 3), x, QQ.frac_field(y)) x**3 - y >>> minpoly(y**Rational(1, 3), x) x**3 - y """ pw = sympify(pw) if not mp: mp = _minpoly_compose(ex, x, dom) if not pw.is_rational: raise NotAlgebraic("%s does not seem to be an algebraic element" % ex) if pw < 0: if mp == x: raise ZeroDivisionError('%s is zero' % ex) mp = _invertx(mp, x) if pw == -1: return mp pw = -pw ex = 1 / ex y = Dummy(str(x)) mp = mp.subs({x: y}) n, d = pw.as_numer_denom() res = Poly(resultant(mp, x**d - y**n, gens=[y]), x, domain=dom) _, factors = res.factor_list() res = _choose_factor(factors, x, ex**pw, dom) return res.as_expr()
def _minpoly_pow(ex, pw, x, dom, mp=None): """ Returns ``minpoly(ex**pw, x)`` Parameters ========== ex : algebraic element pw : rational number x : indeterminate of the polynomial dom: ground domain mp : minimal polynomial of ``p`` Examples ======== >>> from sympy import sqrt, QQ, Rational >>> from sympy.polys.numberfields import _minpoly_pow, minpoly >>> from sympy.abc import x, y >>> p = sqrt(1 + sqrt(2)) >>> _minpoly_pow(p, 2, x, QQ) x**2 - 2*x - 1 >>> minpoly(p**2, x) x**2 - 2*x - 1 >>> _minpoly_pow(y, Rational(1, 3), x, QQ.frac_field(y)) x**3 - y >>> minpoly(y**Rational(1, 3), x) x**3 - y """ pw = sympify(pw) if not mp: mp = _minpoly_compose(ex, x, dom) if not pw.is_rational: raise NotAlgebraic("%s doesn't seem to be an algebraic element" % ex) if pw < 0: if mp == x: raise ZeroDivisionError('%s is zero' % ex) mp = _invertx(mp, x) if pw == -1: return mp pw = -pw ex = 1/ex y = Dummy(str(x)) mp = mp.subs({x: y}) n, d = pw.as_numer_denom() res = Poly(resultant(mp, x**d - y**n, gens=[y]), x, domain=dom) _, factors = res.factor_list() res = _choose_factor(factors, x, ex**pw, dom) return res.as_expr()
def _prime_decomp_easy_case(p, ZK): r""" Compute the decomposition of rational prime *p* in the ring of integers *ZK* (given as a :py:class:`~.Submodule`), in the "easy case", i.e. the case where *p* does not divide the index of $\theta$ in *ZK*, where $\theta$ is the generator of the ``PowerBasis`` of which *ZK* is a ``Submodule``. """ T = ZK.parent.T T_bar = Poly(T, modulus=p) lc, fl = T_bar.factor_list() return [ PrimeIdeal(ZK, p, ZK.parent.element_from_poly(Poly(t, domain=ZZ)), t.degree(), e) for t, e in fl ]
def _apply_Dedekind_criterion(T, p): r""" Apply the "Dedekind criterion" to test whether the order needs to be enlarged relative to a given prime *p*. """ x = T.gen T_bar = Poly(T, modulus=p) lc, fl = T_bar.factor_list() assert lc == 1 g_bar = Poly(1, x, modulus=p) for ti_bar, _ in fl: g_bar *= ti_bar h_bar = T_bar // g_bar g = Poly(g_bar, domain=ZZ) h = Poly(h_bar, domain=ZZ) f = (g * h - T) // p f_bar = Poly(f, modulus=p) Z_bar = f_bar for b in [g_bar, h_bar]: Z_bar = Z_bar.gcd(b) U_bar = T_bar // Z_bar m = Z_bar.degree() return U_bar, m
def _minpoly_op_algebraic_element(op, ex1, ex2, x, dom, mp1=None, mp2=None): """ return the minimal polynomial for ``op(ex1, ex2)`` Parameters ========== op : operation ``Add`` or ``Mul`` ex1, ex2 : expressions for the algebraic elements x : indeterminate of the polynomials dom: ground domain mp1, mp2 : minimal polynomials for ``ex1`` and ``ex2`` or None Examples ======== >>> from sympy import sqrt, Add, Mul, QQ >>> from sympy.polys.numberfields.minpoly import _minpoly_op_algebraic_element >>> from sympy.abc import x, y >>> p1 = sqrt(sqrt(2) + 1) >>> p2 = sqrt(sqrt(2) - 1) >>> _minpoly_op_algebraic_element(Mul, p1, p2, x, QQ) x - 1 >>> q1 = sqrt(y) >>> q2 = 1 / y >>> _minpoly_op_algebraic_element(Add, q1, q2, x, QQ.frac_field(y)) x**2*y**2 - 2*x*y - y**3 + 1 References ========== .. [1] https://en.wikipedia.org/wiki/Resultant .. [2] I.M. Isaacs, Proc. Amer. Math. Soc. 25 (1970), 638 "Degrees of sums in a separable field extension". """ y = Dummy(str(x)) if mp1 is None: mp1 = _minpoly_compose(ex1, x, dom) if mp2 is None: mp2 = _minpoly_compose(ex2, y, dom) else: mp2 = mp2.subs({x: y}) if op is Add: # mp1a = mp1.subs({x: x - y}) if dom == QQ: R, X = ring('X', QQ) p1 = R(dict_from_expr(mp1)[0]) p2 = R(dict_from_expr(mp2)[0]) else: (p1, p2), _ = parallel_poly_from_expr((mp1, x - y), x, y) r = p1.compose(p2) mp1a = r.as_expr() elif op is Mul: mp1a = _muly(mp1, x, y) else: raise NotImplementedError('option not available') if op is Mul or dom != QQ: r = resultant(mp1a, mp2, gens=[y, x]) else: r = rs_compose_add(p1, p2) r = expr_from_dict(r.as_expr_dict(), x) deg1 = degree(mp1, x) deg2 = degree(mp2, y) if op is Mul and deg1 == 1 or deg2 == 1: # if deg1 = 1, then mp1 = x - a; mp1a = x - y - a; # r = mp2(x - a), so that `r` is irreducible return r r = Poly(r, x, domain=dom) _, factors = r.factor_list() res = _choose_factor(factors, x, op(ex1, ex2), dom) return res.as_expr()
def _minpoly_op_algebraic_element(op, ex1, ex2, x, dom, mp1=None, mp2=None): """ return the minimal polynomial for ``op(ex1, ex2)`` Parameters ========== op : operation ``Add`` or ``Mul`` ex1, ex2 : expressions for the algebraic elements x : indeterminate of the polynomials dom: ground domain mp1, mp2 : minimal polynomials for ``ex1`` and ``ex2`` or None Examples ======== >>> from sympy import sqrt, Add, Mul, QQ >>> from sympy.polys.numberfields import _minpoly_op_algebraic_element >>> from sympy.abc import x, y >>> p1 = sqrt(sqrt(2) + 1) >>> p2 = sqrt(sqrt(2) - 1) >>> _minpoly_op_algebraic_element(Mul, p1, p2, x, QQ) x - 1 >>> q1 = sqrt(y) >>> q2 = 1 / y >>> _minpoly_op_algebraic_element(Add, q1, q2, x, QQ.frac_field(y)) x**2*y**2 - 2*x*y - y**3 + 1 References ========== [1] http://en.wikipedia.org/wiki/Resultant [2] I.M. Isaacs, Proc. Amer. Math. Soc. 25 (1970), 638 "Degrees of sums in a separable field extension". """ from sympy import gcd y = Dummy(str(x)) if mp1 is None: mp1 = _minpoly_compose(ex1, x, dom) if mp2 is None: mp2 = _minpoly_compose(ex2, y, dom) else: mp2 = mp2.subs({x: y}) if op is Add: # mp1a = mp1.subs({x: x - y}) (p1, p2), _ = parallel_poly_from_expr((mp1, x - y), x, y) r = p1.compose(p2) mp1a = r.as_expr() elif op is Mul: mp1a = _muly(mp1, x, y) else: raise NotImplementedError('option not available') r = resultant(mp1a, mp2, gens=[y, x]) deg1 = degree(mp1, x) deg2 = degree(mp2, y) if op is Add and gcd(deg1, deg2) == 1: # `r` is irreducible, see [2] return r if op is Mul and deg1 == 1 or deg2 == 1: # if deg1 = 1, then mp1 = x - a; mp1a = x - y - a; # r = mp2(x - a), so that `r` is irreducible return r r = Poly(r, x, domain=dom) _, factors = r.factor_list() res = _choose_factor(factors, x, op(ex1, ex2), dom) return res.as_expr()