def ratint_ratpart(f, g, x): """Horowitz-Ostrogradsky algorithm. Given a field K and polynomials f and g in K[x], such that f and g are coprime and deg(f) < deg(g), returns fractions A and B in K(x), such that f/g = A' + B and B has square-free denominator. """ f = Poly(f, x) g = Poly(g, x) u, v, _ = g.cofactors(g.diff()) n = u.degree() m = v.degree() A_coeffs = [ Dummy('a' + str(n-i)) for i in xrange(0, n) ] B_coeffs = [ Dummy('b' + str(m-i)) for i in xrange(0, m) ] C_coeffs = A_coeffs + B_coeffs A = Poly(A_coeffs, x, domain=ZZ[C_coeffs]) B = Poly(B_coeffs, x, domain=ZZ[C_coeffs]) H = f - A.diff()*v + A*(u.diff()*v).quo(u) - B*u result = solve(H.coeffs(), C_coeffs) A = A.as_expr().subs(result) B = B.as_expr().subs(result) rat_part = cancel(A/u.as_expr(), x) log_part = cancel(B/v.as_expr(), x) return rat_part, log_part
def ratint_ratpart(f, g, x): """ Horowitz-Ostrogradsky algorithm. Given a field K and polynomials f and g in K[x], such that f and g are coprime and deg(f) < deg(g), returns fractions A and B in K(x), such that f/g = A' + B and B has square-free denominator. Examples ======== >>> from sympy.integrals.rationaltools import ratint_ratpart >>> from sympy.abc import x, y >>> from sympy import Poly >>> ratint_ratpart(Poly(1, x, domain='ZZ'), ... Poly(x + 1, x, domain='ZZ'), x) (0, 1/(x + 1)) >>> ratint_ratpart(Poly(1, x, domain='EX'), ... Poly(x**2 + y**2, x, domain='EX'), x) (0, 1/(x**2 + y**2)) >>> ratint_ratpart(Poly(36, x, domain='ZZ'), ... Poly(x**5 - 2*x**4 - 2*x**3 + 4*x**2 + x - 2, x, domain='ZZ'), x) ((12*x + 6)/(x**2 - 1), 12/(x**2 - x - 2)) See Also ======== ratint, ratint_logpart """ from sympy import solve f = Poly(f, x) g = Poly(g, x) u, v, _ = g.cofactors(g.diff()) n = u.degree() m = v.degree() A_coeffs = [ Dummy('a' + str(n - i)) for i in range(0, n) ] B_coeffs = [ Dummy('b' + str(m - i)) for i in range(0, m) ] C_coeffs = A_coeffs + B_coeffs A = Poly(A_coeffs, x, domain=ZZ[C_coeffs]) B = Poly(B_coeffs, x, domain=ZZ[C_coeffs]) H = f - A.diff()*v + A*(u.diff()*v).quo(u) - B*u result = solve(H.coeffs(), C_coeffs) A = A.as_expr().subs(result) B = B.as_expr().subs(result) rat_part = cancel(A/u.as_expr(), x) log_part = cancel(B/v.as_expr(), x) return rat_part, log_part
def _solve_as_poly(f, symbol, solveset_solver, invert_func): """ Solve the equation using polynomial techniques if it already is a polynomial equation or, with a change of variables, can be made so. """ result = None if f.is_polynomial(symbol): solns = roots(f, symbol, cubics=True, quartics=True, quintics=True, domain='EX') num_roots = sum(solns.values()) if degree(f, symbol) <= num_roots: result = FiniteSet(*solns.keys()) else: poly = Poly(f, symbol) solns = poly.all_roots() if poly.degree() <= len(solns): result = FiniteSet(*solns) else: result = ConditionSet(symbol, Eq(f, 0), S.Complexes) else: poly = Poly(f) if poly is None: result = ConditionSet(symbol, Eq(f, 0), S.Complexes) gens = [g for g in poly.gens if g.has(symbol)] if len(gens) == 1: poly = Poly(poly, gens[0]) gen = poly.gen deg = poly.degree() poly = Poly(poly.as_expr(), poly.gen, composite=True) poly_solns = FiniteSet(*roots(poly, cubics=True, quartics=True, quintics=True).keys()) if len(poly_solns) < deg: result = ConditionSet(symbol, Eq(f, 0), S.Complexes) if gen != symbol: y = Dummy('y') lhs, rhs_s = invert_func(gen, y, symbol) if lhs is symbol: result = Union(*[rhs_s.subs(y, s) for s in poly_solns]) else: result = ConditionSet(symbol, Eq(f, 0), S.Complexes) else: result = ConditionSet(symbol, Eq(f, 0), S.Complexes) if result is not None: if isinstance(result, FiniteSet): # this is to simplify solutions like -sqrt(-I) to sqrt(2)/2 # - sqrt(2)*I/2. We are not expanding for solution with free # variables because that makes the solution more complicated. For # example expand_complex(a) returns re(a) + I*im(a) if all([s.free_symbols == set() and not isinstance(s, RootOf) for s in result]): s = Dummy('s') result = imageset(Lambda(s, expand_complex(s)), result) return result else: return ConditionSet(symbol, Eq(f, 0), S.Complexes)
def apart_undetermined_coeffs(P, Q): """Partial fractions via method of undetermined coefficients. """ X = numbered_symbols(cls=Dummy) partial, symbols = [], [] _, factors = Q.factor_list() for f, k in factors: n, q = f.degree(), Q for i in xrange(1, k + 1): coeffs, q = take(X, n), q.quo(f) partial.append((coeffs, q, f, i)) symbols.extend(coeffs) dom = Q.get_domain().inject(*symbols) F = Poly(0, Q.gen, domain=dom) for i, (coeffs, q, f, k) in enumerate(partial): h = Poly(coeffs, Q.gen, domain=dom) partial[i] = (h, f, k) q = q.set_domain(dom) F += h * q system, result = [], S(0) for (k,), coeff in F.terms(): system.append(coeff - P.nth(k)) from sympy.solvers import solve solution = solve(system, symbols) for h, f, k in partial: h = h.as_expr().subs(solution) result += h / f.as_expr() ** k return result
def gosper_term(f, n): r""" Compute Gosper's hypergeometric term for ``f``. Suppose ``f`` is a hypergeometric term such that: .. math:: s_n = \sum_{k=0}^{n-1} f_k and `f_k` doesn't depend on `n`. Returns a hypergeometric term `g_n` such that `g_{n+1} - g_n = f_n`. **Examples** >>> from sympy.concrete.gosper import gosper_term >>> from sympy.functions import factorial >>> from sympy.abc import n >>> gosper_term((4*n + 1)*factorial(n)/factorial(2*n + 1), n) (-n - 1/2)/(n + 1/4) """ r = hypersimp(f, n) if r is None: return None # 'f' is *not* a hypergeometric term p, q = r.as_numer_denom() A, B, C = gosper_normal(p, q, n) B = B.shift(-1) N = S(A.degree()) M = S(B.degree()) K = S(C.degree()) if (N != M) or (A.LC() != B.LC()): D = set([K - max(N, M)]) elif not N: D = set([K - N + 1, S(0)]) else: D = set([K - N + 1, (B.nth(N - 1) - A.nth(N - 1)) / A.LC()]) for d in set(D): if not d.is_Integer or d < 0: D.remove(d) if not D: return None # 'f(n)' is *not* Gosper-summable d = max(D) coeffs = symbols("c:%s" % (d + 1), cls=Dummy) domain = A.get_domain().inject(*coeffs) x = Poly(coeffs, n, domain=domain) H = A * x.shift(1) - B * x - C solution = solve(H.coeffs(), coeffs) if solution is None: return None # 'f(n)' is *not* Gosper-summable x = x.as_expr().subs(solution) for coeff in coeffs: if coeff not in solution: x = x.subs(coeff, 0) if x is S.Zero: return None # 'f(n)' is *not* Gosper-summable else: return B.as_expr() * x / C.as_expr()
def _solve_inequality(ie, s, linear=False): """Return the inequality with s isolated on the left, if possible. If the relationship is non-linear, a solution involving And or Or may be returned. False or True are returned if the relationship is never True or always True, respectively. If `linear` is True (default is False) an `s`-dependent expression will be isoloated on the left, if possible but it will not be solved for `s` unless the expression is linear in `s`. Furthermore, only "safe" operations which don't change the sense of the relationship are applied: no division by an unsigned value is attempted unless the relationship involves Eq or Ne and no division by a value not known to be nonzero is ever attempted. Examples ======== >>> from sympy import Eq, Symbol >>> from sympy.solvers.inequalities import _solve_inequality as f >>> from sympy.abc import x, y For linear expressions, the symbol can be isolated: >>> f(x - 2 < 0, x) x < 2 >>> f(-x - 6 < x, x) x > -3 Sometimes nonlinear relationships will be False >>> f(x**2 + 4 < 0, x) False Or they may involve more than one region of values: >>> f(x**2 - 4 < 0, x) (-2 < x) & (x < 2) To restrict the solution to a relational, set linear=True and only the x-dependent portion will be isolated on the left: >>> f(x**2 - 4 < 0, x, linear=True) x**2 < 4 Division of only nonzero quantities is allowed, so x cannot be isolated by dividing by y: >>> y.is_nonzero is None # it is unknown whether it is 0 or not True >>> f(x*y < 1, x) x*y < 1 And while an equality (or unequality) still holds after dividing by a non-zero quantity >>> nz = Symbol('nz', nonzero=True) >>> f(Eq(x*nz, 1), x) Eq(x, 1/nz) the sign must be known for other inequalities involving > or <: >>> f(x*nz <= 1, x) nz*x <= 1 >>> p = Symbol('p', positive=True) >>> f(x*p <= 1, x) x <= 1/p When there are denominators in the original expression that are removed by expansion, conditions for them will be returned as part of the result: >>> f(x < x*(2/x - 1), x) (x < 1) & Ne(x, 0) """ from sympy.solvers.solvers import denoms if s not in ie.free_symbols: return ie if ie.rhs == s: ie = ie.reversed if ie.lhs == s and s not in ie.rhs.free_symbols: return ie expr = ie.lhs - ie.rhs rv = None try: p = Poly(expr, s) if p.degree() == 0: rv = ie.func(p.as_expr(), 0) elif not linear and p.degree() > 1: # handle in except clause raise NotImplementedError except (PolynomialError, NotImplementedError): if not linear: try: return reduce_rational_inequalities([[ie]], s) except PolynomialError: return solve_univariate_inequality(ie, s) else: p = Poly(expr) e = expanded = p.as_expr() # this is in exanded form if rv is None: # Do a safe inversion of e, moving non-s terms # to the rhs and dividing by a nonzero factor if # the relational is Eq/Ne; for other relationals # the sign must also be positive or negative rhs = 0 b, ax = e.as_independent(s, as_Add=True) e -= b rhs -= b ef = factor_terms(e) a, e = ef.as_independent(s, as_Add=False) if (a.is_zero != False or # don't divide by potential 0 a.is_negative == a.is_positive == None and # if sign is not known then ie.rel_op not in ('!=', '==')): # reject if not Eq/Ne e = ef a = S.One rhs /= a if a.is_positive: rv = ie.func(e, rhs) else: rv = ie.reversed.func(e, rhs) # return conditions under which the value is # valid, too. conds = [rv] beginning_denoms = denoms(ie.lhs) | denoms(ie.rhs) current_denoms = denoms(expanded) for d in beginning_denoms - current_denoms: conds.append(_solve_inequality(Ne(d, 0), s, linear=linear)) return And(*conds)
def _solve_inequality(ie, s, linear=False): """Return the inequality with s isolated on the left, if possible. If the relationship is non-linear, a solution involving And or Or may be returned. False or True are returned if the relationship is never True or always True, respectively. If `linear` is True (default is False) an `s`-dependent expression will be isolated on the left, if possible but it will not be solved for `s` unless the expression is linear in `s`. Furthermore, only "safe" operations which don't change the sense of the relationship are applied: no division by an unsigned value is attempted unless the relationship involves Eq or Ne and no division by a value not known to be nonzero is ever attempted. Examples ======== >>> from sympy import Eq, Symbol >>> from sympy.solvers.inequalities import _solve_inequality as f >>> from sympy.abc import x, y For linear expressions, the symbol can be isolated: >>> f(x - 2 < 0, x) x < 2 >>> f(-x - 6 < x, x) x > -3 Sometimes nonlinear relationships will be False >>> f(x**2 + 4 < 0, x) False Or they may involve more than one region of values: >>> f(x**2 - 4 < 0, x) (-2 < x) & (x < 2) To restrict the solution to a relational, set linear=True and only the x-dependent portion will be isolated on the left: >>> f(x**2 - 4 < 0, x, linear=True) x**2 < 4 Division of only nonzero quantities is allowed, so x cannot be isolated by dividing by y: >>> y.is_nonzero is None # it is unknown whether it is 0 or not True >>> f(x*y < 1, x) x*y < 1 And while an equality (or inequality) still holds after dividing by a non-zero quantity >>> nz = Symbol('nz', nonzero=True) >>> f(Eq(x*nz, 1), x) Eq(x, 1/nz) the sign must be known for other inequalities involving > or <: >>> f(x*nz <= 1, x) nz*x <= 1 >>> p = Symbol('p', positive=True) >>> f(x*p <= 1, x) x <= 1/p When there are denominators in the original expression that are removed by expansion, conditions for them will be returned as part of the result: >>> f(x < x*(2/x - 1), x) (x < 1) & Ne(x, 0) """ from sympy.solvers.solvers import denoms if s not in ie.free_symbols: return ie if ie.rhs == s: ie = ie.reversed if ie.lhs == s and s not in ie.rhs.free_symbols: return ie def classify(ie, s, i): # return True or False if ie evaluates when substituting s with # i else None (if unevaluated) or NaN (when there is an error # in evaluating) try: v = ie.subs(s, i) if v is S.NaN: return v elif v not in (True, False): return return v except TypeError: return S.NaN rv = None oo = S.Infinity expr = ie.lhs - ie.rhs try: p = Poly(expr, s) if p.degree() == 0: rv = ie.func(p.as_expr(), 0) elif not linear and p.degree() > 1: # handle in except clause raise NotImplementedError except (PolynomialError, NotImplementedError): if not linear: try: rv = reduce_rational_inequalities([[ie]], s) except PolynomialError: rv = solve_univariate_inequality(ie, s) # remove restrictions wrt +/-oo that may have been # applied when using sets to simplify the relationship okoo = classify(ie, s, oo) if okoo is S.true and classify(rv, s, oo) is S.false: rv = rv.subs(s < oo, True) oknoo = classify(ie, s, -oo) if (oknoo is S.true and classify(rv, s, -oo) is S.false): rv = rv.subs(-oo < s, True) rv = rv.subs(s > -oo, True) if rv is S.true: rv = (s <= oo) if okoo is S.true else (s < oo) if oknoo is not S.true: rv = And(-oo < s, rv) else: p = Poly(expr) conds = [] if rv is None: e = p.as_expr() # this is in expanded form # Do a safe inversion of e, moving non-s terms # to the rhs and dividing by a nonzero factor if # the relational is Eq/Ne; for other relationals # the sign must also be positive or negative rhs = 0 b, ax = e.as_independent(s, as_Add=True) e -= b rhs -= b ef = factor_terms(e) a, e = ef.as_independent(s, as_Add=False) if (a.is_zero != False or # don't divide by potential 0 a.is_negative == a.is_positive is None and # if sign is not known then ie.rel_op not in ('!=', '==')): # reject if not Eq/Ne e = ef a = S.One rhs /= a if a.is_positive: rv = ie.func(e, rhs) else: rv = ie.reversed.func(e, rhs) # return conditions under which the value is # valid, too. beginning_denoms = denoms(ie.lhs) | denoms(ie.rhs) current_denoms = denoms(rv) for d in beginning_denoms - current_denoms: c = _solve_inequality(Eq(d, 0), s, linear=linear) if isinstance(c, Eq) and c.lhs == s: if classify(rv, s, c.rhs) is S.true: # rv is permitting this value but it shouldn't conds.append(~c) for i in (-oo, oo): if (classify(rv, s, i) is S.true and classify(ie, s, i) is not S.true): conds.append(s < i if i is oo else i < s) conds.append(rv) return And(*conds)
def gosper_term(f, n): r""" Compute Gosper's hypergeometric term for ``f``. Suppose ``f`` is a hypergeometric term such that: .. math:: s_n = \sum_{k=0}^{n-1} f_k and `f_k` doesn't depend on `n`. Returns a hypergeometric term `g_n` such that `g_{n+1} - g_n = f_n`. Examples ======== >>> from sympy.concrete.gosper import gosper_term >>> from sympy.functions import factorial >>> from sympy.abc import n >>> gosper_term((4*n + 1)*factorial(n)/factorial(2*n + 1), n) (-n - 1/2)/(n + 1/4) """ r = hypersimp(f, n) if r is None: return None # 'f' is *not* a hypergeometric term p, q = r.as_numer_denom() A, B, C = gosper_normal(p, q, n) B = B.shift(-1) N = S(A.degree()) M = S(B.degree()) K = S(C.degree()) if (N != M) or (A.LC() != B.LC()): D = set([K - max(N, M)]) elif not N: D = set([K - N + 1, S(0)]) else: D = set([K - N + 1, (B.nth(N - 1) - A.nth(N - 1))/A.LC()]) for d in set(D): if not d.is_Integer or d < 0: D.remove(d) if not D: return None # 'f(n)' is *not* Gosper-summable d = max(D) coeffs = symbols('c:%s' % (d + 1), cls=Dummy) domain = A.get_domain().inject(*coeffs) x = Poly(coeffs, n, domain=domain) H = A*x.shift(1) - B*x - C solution = solve(H.coeffs(), coeffs) if solution is None: return None # 'f(n)' is *not* Gosper-summable x = x.as_expr().subs(solution) for coeff in coeffs: if coeff not in solution: x = x.subs(coeff, 0) if x is S.Zero: return None # 'f(n)' is *not* Gosper-summable else: return B.as_expr()*x/C.as_expr()
def ratint_ratpart(f, g, x): """ Horowitz-Ostrogradsky algorithm. Explanation =========== Given a field K and polynomials f and g in K[x], such that f and g are coprime and deg(f) < deg(g), returns fractions A and B in K(x), such that f/g = A' + B and B has square-free denominator. Examples ======== >>> from sympy.integrals.rationaltools import ratint_ratpart >>> from sympy.abc import x, y >>> from sympy import Poly >>> ratint_ratpart(Poly(1, x, domain='ZZ'), ... Poly(x + 1, x, domain='ZZ'), x) (0, 1/(x + 1)) >>> ratint_ratpart(Poly(1, x, domain='EX'), ... Poly(x**2 + y**2, x, domain='EX'), x) (0, 1/(x**2 + y**2)) >>> ratint_ratpart(Poly(36, x, domain='ZZ'), ... Poly(x**5 - 2*x**4 - 2*x**3 + 4*x**2 + x - 2, x, domain='ZZ'), x) ((12*x + 6)/(x**2 - 1), 12/(x**2 - x - 2)) See Also ======== ratint, ratint_logpart """ from sympy.solvers.solvers import solve f = Poly(f, x) g = Poly(g, x) u, v, _ = g.cofactors(g.diff()) n = u.degree() m = v.degree() A_coeffs = [Dummy('a' + str(n - i)) for i in range(0, n)] B_coeffs = [Dummy('b' + str(m - i)) for i in range(0, m)] C_coeffs = A_coeffs + B_coeffs A = Poly(A_coeffs, x, domain=ZZ[C_coeffs]) B = Poly(B_coeffs, x, domain=ZZ[C_coeffs]) H = f - A.diff() * v + A * (u.diff() * v).quo(u) - B * u result = solve(H.coeffs(), C_coeffs) A = A.as_expr().subs(result) B = B.as_expr().subs(result) rat_part = cancel(A / u.as_expr(), x) log_part = cancel(B / v.as_expr(), x) return rat_part, log_part
def _solve_as_poly(f, symbol, domain=S.Complexes): """ Solve the equation using polynomial techniques if it already is a polynomial equation or, with a change of variables, can be made so. """ result = None if f.is_polynomial(symbol): solns = roots(f, symbol, cubics=True, quartics=True, quintics=True, domain='EX') num_roots = sum(solns.values()) if degree(f, symbol) <= num_roots: result = FiniteSet(*solns.keys()) else: poly = Poly(f, symbol) solns = poly.all_roots() if poly.degree() <= len(solns): result = FiniteSet(*solns) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: poly = Poly(f) if poly is None: result = ConditionSet(symbol, Eq(f, 0), domain) gens = [g for g in poly.gens if g.has(symbol)] if len(gens) == 1: poly = Poly(poly, gens[0]) gen = poly.gen deg = poly.degree() poly = Poly(poly.as_expr(), poly.gen, composite=True) poly_solns = FiniteSet( *roots(poly, cubics=True, quartics=True, quintics=True).keys()) if len(poly_solns) < deg: result = ConditionSet(symbol, Eq(f, 0), domain) if gen != symbol: y = Dummy('y') inverter = invert_real if domain.is_subset( S.Reals) else invert_complex lhs, rhs_s = inverter(gen, y, symbol) if lhs == symbol: result = Union(*[rhs_s.subs(y, s) for s in poly_solns]) else: result = ConditionSet(symbol, Eq(f, 0), domain) else: result = ConditionSet(symbol, Eq(f, 0), domain) if result is not None: if isinstance(result, FiniteSet): # this is to simplify solutions like -sqrt(-I) to sqrt(2)/2 # - sqrt(2)*I/2. We are not expanding for solution with free # variables because that makes the solution more complicated. For # example expand_complex(a) returns re(a) + I*im(a) if all([ s.free_symbols == set() and not isinstance(s, RootOf) for s in result ]): s = Dummy('s') result = imageset(Lambda(s, expand_complex(s)), result) if isinstance(result, FiniteSet): result = result.intersection(domain) return result else: return ConditionSet(symbol, Eq(f, 0), domain)
def _solve_as_poly(f, symbol, solveset_solver, invert_func): """ Solve the equation using polynomial techniques if it already is a polynomial equation or, with a change of variables, can be made so. """ result = None if f.is_polynomial(symbol): solns = roots(f, symbol, cubics=True, quartics=True, quintics=True, domain='EX') num_roots = sum(solns.values()) if degree(f, symbol) <= num_roots: result = FiniteSet(*solns.keys()) else: poly = Poly(f, symbol) solns = poly.all_roots() if poly.degree() <= len(solns): result = FiniteSet(*solns) else: raise NotImplementedError("Couldn't find all roots " "of the equation %s" % f) else: poly = Poly(f) if poly is None: raise NotImplementedError("Could not convert %s to Poly" % f) gens = [g for g in poly.gens if g.has(symbol)] if len(gens) == 1: poly = Poly(poly, gens[0]) gen = poly.gen deg = poly.degree() poly = Poly(poly.as_expr(), poly.gen, composite=True) poly_solns = FiniteSet( *roots(poly, cubics=True, quartics=True, quintics=True).keys()) if len(poly_solns) < deg: raise NotImplementedError("Couldn't find all the roots of " "the equation %s" % f) if gen != symbol: y = Dummy('y') lhs, rhs_s = invert_func(gen, y, symbol) result = Union(*[rhs_s.subs(y, s) for s in poly_solns]) if lhs is not symbol and lhs is not gen: result = Union( * [solveset_solver(lhs - rhs, symbol) for rhs in result]) else: raise NotImplementedError else: raise NotImplementedError("multiple generators not handled" " by solveset") if result is not None: if isinstance(result, FiniteSet): # this is to simplify solutions like -sqrt(-I) to sqrt(2)/2 # - sqrt(2)*I/2. We are not expanding for solution with free # variables because that makes the solution more complicated. For # example expand_complex(a) returns re(a) + I*im(a) if all([ s.free_symbols == set() and not isinstance(s, RootOf) for s in result ]): s = Dummy('s') result = imageset(Lambda(s, expand_complex(s)), result) return result else: raise NotImplementedError