from sympy import ( Symbol, gamma, I, oo, nan, zoo, factorial, sqrt, Rational, log, polygamma, EulerGamma, pi, uppergamma, S, expand_func, loggamma, sin, cos, O, lowergamma, exp, erf, erfc, exp_polar, harmonic, zeta,conjugate) from sympy.core.function import ArgumentIndexError from sympy.utilities.randtest import (test_derivative_numerically as td, random_complex_number as randcplx, verify_numerically as tn) from sympy.utilities.pytest import raises x = Symbol('x') y = Symbol('y') n = Symbol('n', integer=True) w = Symbol('w', real=True) def test_gamma(): assert gamma(nan) == nan assert gamma(oo) == oo assert gamma(-100) == zoo assert gamma(0) == zoo assert gamma(1) == 1 assert gamma(2) == 1 assert gamma(3) == 2 assert gamma(102) == factorial(101) assert gamma(Rational(1, 2)) == sqrt(pi) assert gamma(Rational(3, 2)) == Rational(1, 2)*sqrt(pi) assert gamma(Rational(5, 2)) == Rational(3, 4)*sqrt(pi) assert gamma(Rational(7, 2)) == Rational(15, 8)*sqrt(pi) assert gamma(Rational(-1, 2)) == -2*sqrt(pi) assert gamma(Rational(-3, 2)) == Rational(4, 3)*sqrt(pi) assert gamma(Rational(-5, 2)) == -Rational(8, 15)*sqrt(pi) assert gamma(Rational(-15, 2)) == Rational(256, 2027025)*sqrt(pi) assert gamma(Rational( -11, 8)).expand(func=True) == Rational(64, 33)*gamma(Rational(5, 8)) assert gamma(Rational( -10, 3)).expand(func=True) == Rational(81, 280)*gamma(Rational(2, 3)) assert gamma(Rational( 14, 3)).expand(func=True) == Rational(880, 81)*gamma(Rational(2, 3)) assert gamma(Rational( 17, 7)).expand(func=True) == Rational(30, 49)*gamma(Rational(3, 7)) assert gamma(Rational( 19, 8)).expand(func=True) == Rational(33, 64)*gamma(Rational(3, 8)) assert gamma(x).diff(x) == gamma(x)*polygamma(0, x) assert gamma(x - 1).expand(func=True) == gamma(x)/(x - 1) assert gamma(x + 2).expand(func=True, mul=False) == x*(x + 1)*gamma(x) assert conjugate(gamma(x)) == gamma(conjugate(x)) assert expand_func(gamma(x + Rational(3, 2))) == \ (x + Rational(1, 2))*gamma(x + Rational(1, 2)) assert expand_func(gamma(x - Rational(1, 2))) == \ gamma(Rational(1, 2) + x)/(x - Rational(1, 2)) # Test a bug: assert expand_func(gamma(x + Rational(3, 4))) == gamma(x + Rational(3, 4)) assert gamma(3*exp_polar(I*pi)/4).is_nonnegative is False assert gamma(3*exp_polar(I*pi)/4).is_nonpositive is True def test_gamma_rewrite(): assert gamma(n).rewrite(factorial) == factorial(n - 1) def test_gamma_series(): assert gamma(x + 1).series(x, 0, 3) == \ 1 - EulerGamma*x + x**2*(EulerGamma**2/2 + pi**2/12) + O(x**3) assert gamma(x).series(x, -1, 3) == \ -1/(x + 1) + EulerGamma - 1 + (x + 1)*(-1 - pi**2/12 - EulerGamma**2/2 + \ EulerGamma) + (x + 1)**2*(-1 - pi**2/12 - EulerGamma**2/2 + EulerGamma**3/6 - \ polygamma(2, 1)/6 + EulerGamma*pi**2/12 + EulerGamma) + O((x + 1)**3, (x, -1)) def tn_branch(s, func): from sympy import I, pi, exp_polar from random import uniform c = uniform(1, 5) expr = func(s, c*exp_polar(I*pi)) - func(s, c*exp_polar(-I*pi)) eps = 1e-15 expr2 = func(s + eps, -c + eps*I) - func(s + eps, -c - eps*I) return abs(expr.n() - expr2.n()).n() < 1e-10 def test_lowergamma(): from sympy import meijerg, exp_polar, I, expint assert lowergamma(x, 0) == 0 assert lowergamma(x, y).diff(y) == y**(x - 1)*exp(-y) assert td(lowergamma(randcplx(), y), y) assert td(lowergamma(x, randcplx()), x) assert lowergamma(x, y).diff(x) == \ gamma(x)*polygamma(0, x) - uppergamma(x, y)*log(y) \ - meijerg([], [1, 1], [0, 0, x], [], y) assert lowergamma(S.Half, x) == sqrt(pi)*erf(sqrt(x)) assert not lowergamma(S.Half - 3, x).has(lowergamma) assert not lowergamma(S.Half + 3, x).has(lowergamma) assert lowergamma(S.Half, x, evaluate=False).has(lowergamma) assert tn(lowergamma(S.Half + 3, x, evaluate=False), lowergamma(S.Half + 3, x), x) assert tn(lowergamma(S.Half - 3, x, evaluate=False), lowergamma(S.Half - 3, x), x) assert tn_branch(-3, lowergamma) assert tn_branch(-4, lowergamma) assert tn_branch(S(1)/3, lowergamma) assert tn_branch(pi, lowergamma) assert lowergamma(3, exp_polar(4*pi*I)*x) == lowergamma(3, x) assert lowergamma(y, exp_polar(5*pi*I)*x) == \ exp(4*I*pi*y)*lowergamma(y, x*exp_polar(pi*I)) assert lowergamma(-2, exp_polar(5*pi*I)*x) == \ lowergamma(-2, x*exp_polar(I*pi)) + 2*pi*I assert conjugate(lowergamma(x, y)) == lowergamma(conjugate(x), conjugate(y)) assert conjugate(lowergamma(x, 0)) == conjugate(lowergamma(x, 0)) assert conjugate(lowergamma(x, -oo)) == conjugate(lowergamma(x, -oo)) assert lowergamma( x, y).rewrite(expint) == -y**x*expint(-x + 1, y) + gamma(x) k = Symbol('k', integer=True) assert lowergamma( k, y).rewrite(expint) == -y**k*expint(-k + 1, y) + gamma(k) k = Symbol('k', integer=True, positive=False) assert lowergamma(k, y).rewrite(expint) == lowergamma(k, y) assert lowergamma(x, y).rewrite(uppergamma) == gamma(x) - uppergamma(x, y) assert lowergamma(70, 6) == factorial(69) - 69035724522603011058660187038367026272747334489677105069435923032634389419656200387949342530805432320 * exp(-6) assert (lowergamma(S(77) / 2, 6) - lowergamma(S(77) / 2, 6, evaluate=False)).evalf() < 1e-16 assert (lowergamma(-S(77) / 2, 6) - lowergamma(-S(77) / 2, 6, evaluate=False)).evalf() < 1e-16 def test_uppergamma(): from sympy import meijerg, exp_polar, I, expint assert uppergamma(4, 0) == 6 assert uppergamma(x, y).diff(y) == -y**(x - 1)*exp(-y) assert td(uppergamma(randcplx(), y), y) assert uppergamma(x, y).diff(x) == \ uppergamma(x, y)*log(y) + meijerg([], [1, 1], [0, 0, x], [], y) assert td(uppergamma(x, randcplx()), x) assert uppergamma(S.Half, x) == sqrt(pi)*erfc(sqrt(x)) assert not uppergamma(S.Half - 3, x).has(uppergamma) assert not uppergamma(S.Half + 3, x).has(uppergamma) assert uppergamma(S.Half, x, evaluate=False).has(uppergamma) assert tn(uppergamma(S.Half + 3, x, evaluate=False), uppergamma(S.Half + 3, x), x) assert tn(uppergamma(S.Half - 3, x, evaluate=False), uppergamma(S.Half - 3, x), x) assert tn_branch(-3, uppergamma) assert tn_branch(-4, uppergamma) assert tn_branch(S(1)/3, uppergamma) assert tn_branch(pi, uppergamma) assert uppergamma(3, exp_polar(4*pi*I)*x) == uppergamma(3, x) assert uppergamma(y, exp_polar(5*pi*I)*x) == \ exp(4*I*pi*y)*uppergamma(y, x*exp_polar(pi*I)) + \ gamma(y)*(1 - exp(4*pi*I*y)) assert uppergamma(-2, exp_polar(5*pi*I)*x) == \ uppergamma(-2, x*exp_polar(I*pi)) - 2*pi*I assert uppergamma(-2, x) == expint(3, x)/x**2 assert conjugate(uppergamma(x, y)) == uppergamma(conjugate(x), conjugate(y)) assert conjugate(uppergamma(x, 0)) == gamma(conjugate(x)) assert conjugate(uppergamma(x, -oo)) == conjugate(uppergamma(x, -oo)) assert uppergamma(x, y).rewrite(expint) == y**x*expint(-x + 1, y) assert uppergamma(x, y).rewrite(lowergamma) == gamma(x) - lowergamma(x, y) assert uppergamma(70, 6) == 69035724522603011058660187038367026272747334489677105069435923032634389419656200387949342530805432320*exp(-6) assert (uppergamma(S(77) / 2, 6) - uppergamma(S(77) / 2, 6, evaluate=False)).evalf() < 1e-16 assert (uppergamma(-S(77) / 2, 6) - uppergamma(-S(77) / 2, 6, evaluate=False)).evalf() < 1e-16 def test_polygamma(): from sympy import I assert polygamma(n, nan) == nan assert polygamma(0, oo) == oo assert polygamma(0, -oo) == oo assert polygamma(0, I*oo) == oo assert polygamma(0, -I*oo) == oo assert polygamma(1, oo) == 0 assert polygamma(5, oo) == 0 assert polygamma(0, -9) == zoo assert polygamma(0, -9) == zoo assert polygamma(0, -1) == zoo assert polygamma(0, 0) == zoo assert polygamma(0, 1) == -EulerGamma assert polygamma(0, 7) == Rational(49, 20) - EulerGamma assert polygamma(1, 1) == pi**2/6 assert polygamma(1, 2) == pi**2/6 - 1 assert polygamma(1, 3) == pi**2/6 - Rational(5, 4) assert polygamma(3, 1) == pi**4 / 15 assert polygamma(3, 5) == 6*(Rational(-22369, 20736) + pi**4/90) assert polygamma(5, 1) == 8 * pi**6 / 63 def t(m, n): x = S(m)/n r = polygamma(0, x) if r.has(polygamma): return False return abs(polygamma(0, x.n()).n() - r.n()).n() < 1e-10 assert t(1, 2) assert t(3, 2) assert t(-1, 2) assert t(1, 4) assert t(-3, 4) assert t(1, 3) assert t(4, 3) assert t(3, 4) assert t(2, 3) assert t(123, 5) assert polygamma(0, x).rewrite(zeta) == polygamma(0, x) assert polygamma(1, x).rewrite(zeta) == zeta(2, x) assert polygamma(2, x).rewrite(zeta) == -2*zeta(3, x) assert polygamma(3, 7*x).diff(x) == 7*polygamma(4, 7*x) assert polygamma(0, x).rewrite(harmonic) == harmonic(x - 1) - EulerGamma assert polygamma(2, x).rewrite(harmonic) == 2*harmonic(x - 1, 3) - 2*zeta(3) ni = Symbol("n", integer=True) assert polygamma(ni, x).rewrite(harmonic) == (-1)**(ni + 1)*(-harmonic(x - 1, ni + 1) + zeta(ni + 1))*factorial(ni) # Polygamma of non-negative integer order is unbranched: from sympy import exp_polar k = Symbol('n', integer=True, nonnegative=True) assert polygamma(k, exp_polar(2*I*pi)*x) == polygamma(k, x) # but negative integers are branched! k = Symbol('n', integer=True) assert polygamma(k, exp_polar(2*I*pi)*x).args == (k, exp_polar(2*I*pi)*x) # Polygamma of order -1 is loggamma: assert polygamma(-1, x) == loggamma(x) # But smaller orders are iterated integrals and don't have a special name assert polygamma(-2, x).func is polygamma # Test a bug assert polygamma(0, -x).expand(func=True) == polygamma(0, -x) def test_polygamma_expand_func(): assert polygamma(0, x).expand(func=True) == polygamma(0, x) assert polygamma(0, 2*x).expand(func=True) == \ polygamma(0, x)/2 + polygamma(0, Rational(1, 2) + x)/2 + log(2) assert polygamma(1, 2*x).expand(func=True) == \ polygamma(1, x)/4 + polygamma(1, Rational(1, 2) + x)/4 assert polygamma(2, x).expand(func=True) == \ polygamma(2, x) assert polygamma(0, -1 + x).expand(func=True) == \ polygamma(0, x) - 1/(x - 1) assert polygamma(0, 1 + x).expand(func=True) == \ 1/x + polygamma(0, x ) assert polygamma(0, 2 + x).expand(func=True) == \ 1/x + 1/(1 + x) + polygamma(0, x) assert polygamma(0, 3 + x).expand(func=True) == \ polygamma(0, x) + 1/x + 1/(1 + x) + 1/(2 + x) assert polygamma(0, 4 + x).expand(func=True) == \ polygamma(0, x) + 1/x + 1/(1 + x) + 1/(2 + x) + 1/(3 + x) assert polygamma(1, 1 + x).expand(func=True) == \ polygamma(1, x) - 1/x**2 assert polygamma(1, 2 + x).expand(func=True, multinomial=False) == \ polygamma(1, x) - 1/x**2 - 1/(1 + x)**2 assert polygamma(1, 3 + x).expand(func=True, multinomial=False) == \ polygamma(1, x) - 1/x**2 - 1/(1 + x)**2 - 1/(2 + x)**2 assert polygamma(1, 4 + x).expand(func=True, multinomial=False) == \ polygamma(1, x) - 1/x**2 - 1/(1 + x)**2 - \ 1/(2 + x)**2 - 1/(3 + x)**2 assert polygamma(0, x + y).expand(func=True) == \ polygamma(0, x + y) assert polygamma(1, x + y).expand(func=True) == \ polygamma(1, x + y) assert polygamma(1, 3 + 4*x + y).expand(func=True, multinomial=False) == \ polygamma(1, y + 4*x) - 1/(y + 4*x)**2 - \ 1/(1 + y + 4*x)**2 - 1/(2 + y + 4*x)**2 assert polygamma(3, 3 + 4*x + y).expand(func=True, multinomial=False) == \ polygamma(3, y + 4*x) - 6/(y + 4*x)**4 - \ 6/(1 + y + 4*x)**4 - 6/(2 + y + 4*x)**4 assert polygamma(3, 4*x + y + 1).expand(func=True, multinomial=False) == \ polygamma(3, y + 4*x) - 6/(y + 4*x)**4 e = polygamma(3, 4*x + y + S(3)/2) assert e.expand(func=True) == e e = polygamma(3, x + y + S(3)/4) assert e.expand(func=True, basic=False) == e def test_loggamma(): raises(TypeError, lambda: loggamma(2, 3)) raises(ArgumentIndexError, lambda: loggamma(x).fdiff(2)) assert loggamma(-1) == oo assert loggamma(-2) == oo assert loggamma(0) == oo assert loggamma(1) == 0 assert loggamma(2) == 0 assert loggamma(3) == log(2) assert loggamma(4) == log(6) n = Symbol("n", integer=True, positive=True) assert loggamma(n) == log(gamma(n)) assert loggamma(-n) == oo assert loggamma(n/2) == log(2**(-n + 1)*sqrt(pi)*gamma(n)/gamma(n/2 + S.Half)) from sympy import I assert loggamma(oo) == oo assert loggamma(-oo) == zoo assert loggamma(I*oo) == zoo assert loggamma(-I*oo) == zoo assert loggamma(zoo) == zoo assert loggamma(nan) == nan L = loggamma(S(16)/3) E = -5*log(3) + loggamma(S(1)/3) + log(4) + log(7) + log(10) + log(13) assert expand_func(L).doit() == E assert L.n() == E.n() L = loggamma(19/S(4)) E = -4*log(4) + loggamma(S(3)/4) + log(3) + log(7) + log(11) + log(15) assert expand_func(L).doit() == E assert L.n() == E.n() L = loggamma(S(23)/7) E = -3*log(7) + log(2) + loggamma(S(2)/7) + log(9) + log(16) assert expand_func(L).doit() == E assert L.n() == E.n() L = loggamma(19/S(4)-7) E = -log(9) - log(5) + loggamma(S(3)/4) + 3*log(4) - 3*I*pi assert expand_func(L).doit() == E assert L.n() == E.n() L = loggamma(23/S(7)-6) E = -log(19) - log(12) - log(5) + loggamma(S(2)/7) + 3*log(7) - 3*I*pi assert expand_func(L).doit() == E assert L.n() == E.n() assert loggamma(x).diff(x) == polygamma(0, x) s1 = loggamma(1/(x + sin(x)) + cos(x)).nseries(x, n=4) s2 = (-log(2*x) - 1)/(2*x) - log(x/pi)/2 + (4 - log(2*x))*x/24 + O(x**2) + \ log(x)*x**2/2 assert (s1 - s2).expand(force=True).removeO() == 0 s1 = loggamma(1/x).series(x) s2 = (1/x - S(1)/2)*log(1/x) - 1/x + log(2*pi)/2 + \ x/12 - x**3/360 + x**5/1260 + O(x**7) assert ((s1 - s2).expand(force=True)).removeO() == 0 assert loggamma(x).rewrite('intractable') == log(gamma(x)) s1 = loggamma(x).series(x) assert s1 == -log(x) - EulerGamma*x + pi**2*x**2/12 + x**3*polygamma(2, 1)/6 + \ pi**4*x**4/360 + x**5*polygamma(4, 1)/120 + O(x**6) assert s1 == loggamma(x).rewrite('intractable').series(x) assert conjugate(loggamma(x)) == loggamma(conjugate(x)) assert conjugate(loggamma(0)) == conjugate(loggamma(0)) assert conjugate(loggamma(1)) == loggamma(conjugate(1)) assert conjugate(loggamma(-oo)) == conjugate(loggamma(-oo)) assert loggamma(x).is_real is None y, z = Symbol('y', real=True), Symbol('z', imaginary=True) assert loggamma(y).is_real assert loggamma(z).is_real is False def tN(N, M): assert loggamma(1/x)._eval_nseries(x, n=N).getn() == M tN(0, 0) tN(1, 1) tN(2, 3) tN(3, 3) tN(4, 5) tN(5, 5) def test_polygamma_expansion(): # A. & S., pa. 259 and 260 assert polygamma(0, 1/x).nseries(x, n=3) == \ -log(x) - x/2 - x**2/12 + O(x**4) assert polygamma(1, 1/x).series(x, n=5) == \ x + x**2/2 + x**3/6 + O(x**5) assert polygamma(3, 1/x).nseries(x, n=11) == \ 2*x**3 + 3*x**4 + 2*x**5 - x**7 + 4*x**9/3 + O(x**11) def test_issue_8657(): n = Symbol('n', negative=True, integer=True) m = Symbol('m', integer=True) o = Symbol('o', positive=True) p = Symbol('p', negative=True, integer=False) assert gamma(n).is_real is None assert gamma(m).is_real is None assert gamma(o).is_real is True assert gamma(p).is_real is True assert gamma(w).is_real is None def test_issue_8524(): x = Symbol('x', positive=True) y = Symbol('y', negative=True) z = Symbol('z', positive=False) p = Symbol('p', negative=False) q = Symbol('q', integer=True) r = Symbol('r', integer=False) e = Symbol('e', even=True, negative=True) assert gamma(x).is_positive is True assert gamma(y).is_positive is None assert gamma(z).is_positive is None assert gamma(p).is_positive is None assert gamma(q).is_positive is None assert gamma(r).is_positive is None assert gamma(e + S.Half).is_positive is True assert gamma(e - S.Half).is_positive is False def test_issue_14450(): assert uppergamma(3/8, x).evalf() == uppergamma(0.375, x) assert lowergamma(x, 3/8).evalf() == lowergamma(x, 0.375) # some values from Wolfram Alpha for comparison assert abs(uppergamma(S(3)/8, 2).evalf() - 0.07105675881) < 1e-9 assert abs(lowergamma(S(3)/8, 2).evalf() - 2.2993794256) < 1e-9 def test_issue_14528(): k = Symbol('k', integer=True, nonpositive=True) assert isinstance(gamma(k), gamma)