def mpc_besseljn(n, z, prec, rounding=round_fast):
negate = n < 0 and n & 1
n = abs(n)
origprec = prec
zre, zim = z
mag = max(zre[2]+zre[3], zim[2]+zim[3])
prec += 20 + n*bitcount(n) + abs(mag)
if mag < 0:
prec -= n * mag
zre = to_fixed(zre, prec)
zim = to_fixed(zim, prec)
z2re = (zre**2 - zim**2) >> prec
z2im = (zre*zim) >> (prec-1)
if not n:
sre = tre = MPZ_ONE << prec
sim = tim = MPZ_ZERO
else:
re, im = complex_int_pow(zre, zim, n)
sre = tre = (re // ifac(n)) >> ((n-1)*prec + n)
sim = tim = (im // ifac(n)) >> ((n-1)*prec + n)
k = 1
while abs(tre) + abs(tim) > 3:
p = -4*k*(k+n)
tre, tim = tre*z2re - tim*z2im, tim*z2re + tre*z2im
tre = (tre // p) >> prec
tim = (tim // p) >> prec
sre += tre
sim += tim
k += 1
if negate:
sre = -sre
sim = -sim
re = from_man_exp(sre, -prec, origprec, rounding)
im = from_man_exp(sim, -prec, origprec, rounding)
return (re, im)
def mpc_besseljn(n, z, prec, rounding=round_fast):
negate = n < 0 and n & 1
n = abs(n)
origprec = prec
zre, zim = z
mag = max(zre[2] + zre[3], zim[2] + zim[3])
prec += 20 + n * bitcount(n) + abs(mag)
if mag < 0:
prec -= n * mag
zre = to_fixed(zre, prec)
zim = to_fixed(zim, prec)
z2re = (zre**2 - zim**2) >> prec
z2im = (zre * zim) >> (prec - 1)
if not n:
sre = tre = MPZ_ONE << prec
sim = tim = MPZ_ZERO
else:
re, im = complex_int_pow(zre, zim, n)
sre = tre = (re // ifac(n)) >> ((n - 1) * prec + n)
sim = tim = (im // ifac(n)) >> ((n - 1) * prec + n)
k = 1
while abs(tre) + abs(tim) > 3:
p = -4 * k * (k + n)
tre, tim = tre * z2re - tim * z2im, tim * z2re + tre * z2im
tre = (tre // p) >> prec
tim = (tim // p) >> prec
sre += tre
sim += tim
k += 1
if negate:
sre = -sre
sim = -sim
re = from_man_exp(sre, -prec, origprec, rounding)
im = from_man_exp(sim, -prec, origprec, rounding)
return (re, im)
def mpf_gamma_int(n, prec, rounding=round_fast):
if n < 1000:
return from_int(ifac(n-1), prec, rounding)
# XXX: choose the cutoff less arbitrarily
size = int(n*math.log(n,2))
if prec > size/20.0:
return from_int(ifac(n-1), prec, rounding)
return mpf_gamma(from_int(n), prec, rounding)
def mpf_gamma_int(n, prec, rounding=round_fast):
if n < 1000:
return from_int(ifac(n - 1), prec, rounding)
# XXX: choose the cutoff less arbitrarily
size = int(n * math.log(n, 2))
if prec > size / 20.0:
return from_int(ifac(n - 1), prec, rounding)
return mpf_gamma(from_int(n), prec, rounding)
def mpf_gamma(x, prec, rounding=round_fast, p1=1):
"""
Computes the gamma function of a real floating-point argument.
With p1=0, computes a factorial instead.
"""
sign, man, exp, bc = x
if not man:
if x == finf:
return finf
if x == fninf or x == fnan:
return fnan
# More precision is needed for enormous x. TODO:
# use Stirling's formula + Euler-Maclaurin summation
size = exp + bc
if size > 5:
size = int(size * math.log(size,2))
wp = prec + max(0, size) + 15
if exp >= 0:
if sign or (p1 and not man):
raise ValueError("gamma function pole")
# A direct factorial is fastest
if exp + bc <= 10:
return from_int(ifac((man<<exp)-p1), prec, rounding)
reflect = sign or exp+bc < -1
if p1:
# Should be done exactly!
x = mpf_sub(x, fone)
# x < 0.25
if reflect:
# gamma = pi / (sin(pi*x) * gamma(1-x))
wp += 15
pix = mpf_mul(x, mpf_pi(wp), wp)
t = mpf_sin_pi(x, wp)
g = mpf_gamma(mpf_sub(fone, x), wp)
return mpf_div(pix, mpf_mul(t, g, wp), prec, rounding)
sprec, a, c = get_spouge_coefficients(wp)
s = spouge_sum_real(x, sprec, a, c)
# gamma = exp(log(x+a)*(x+0.5) - xpa) * s
xpa = mpf_add(x, from_int(a), wp)
logxpa = mpf_log(xpa, wp)
xph = mpf_add(x, fhalf, wp)
t = mpf_sub(mpf_mul(logxpa, xph, wp), xpa, wp)
t = mpf_mul(mpf_exp(t, wp), s, prec, rounding)
return t
def mpf_gamma(x, prec, rounding=round_fast, p1=1):
"""
Computes the gamma function of a real floating-point argument.
With p1=0, computes a factorial instead.
"""
sign, man, exp, bc = x
if not man:
if x == finf:
return finf
if x == fninf or x == fnan:
return fnan
# More precision is needed for enormous x. TODO:
# use Stirling's formula + Euler-Maclaurin summation
size = exp + bc
if size > 5:
size = int(size * math.log(size, 2))
wp = prec + max(0, size) + 15
if exp >= 0:
if sign or (p1 and not man):
raise ValueError("gamma function pole")
# A direct factorial is fastest
if exp + bc <= 10:
return from_int(ifac((man << exp) - p1), prec, rounding)
reflect = sign or exp + bc < -1
if p1:
# Should be done exactly!
x = mpf_sub(x, fone)
# x < 0.25
if reflect:
# gamma = pi / (sin(pi*x) * gamma(1-x))
wp += 15
pix = mpf_mul(x, mpf_pi(wp), wp)
t = mpf_sin_pi(x, wp)
g = mpf_gamma(mpf_sub(fone, x), wp)
return mpf_div(pix, mpf_mul(t, g, wp), prec, rounding)
sprec, a, c = get_spouge_coefficients(wp)
s = spouge_sum_real(x, sprec, a, c)
# gamma = exp(log(x+a)*(x+0.5) - xpa) * s
xpa = mpf_add(x, from_int(a), wp)
logxpa = mpf_log(xpa, wp)
xph = mpf_add(x, fhalf, wp)
t = mpf_sub(mpf_mul(logxpa, xph, wp), xpa, wp)
t = mpf_mul(mpf_exp(t, wp), s, prec, rounding)
return t
def mpf_besseljn(n, x, prec, rounding=round_fast):
prec += 50
negate = n < 0 and n & 1
mag = x[2]+x[3]
n = abs(n)
wp = prec + 20 + n*bitcount(n)
if mag < 0:
wp -= n * mag
x = to_fixed(x, wp)
x2 = (x**2) >> wp
if not n:
s = t = MPZ_ONE << wp
else:
s = t = (x**n // ifac(n)) >> ((n-1)*wp + n)
k = 1
while t:
t = ((t * x2) // (-4*k*(k+n))) >> wp
s += t
k += 1
if negate:
s = -s
return from_man_exp(s, -wp, prec, rounding)
def mpf_besseljn(n, x, prec, rounding=round_fast):
prec += 50
negate = n < 0 and n & 1
mag = x[2] + x[3]
n = abs(n)
wp = prec + 20 + n * bitcount(n)
if mag < 0:
wp -= n * mag
x = to_fixed(x, wp)
x2 = (x**2) >> wp
if not n:
s = t = MPZ_ONE << wp
else:
s = t = (x**n // ifac(n)) >> ((n - 1) * wp + n)
k = 1
while t:
t = ((t * x2) // (-4 * k * (k + n))) >> wp
s += t
k += 1
if negate:
s = -s
return from_man_exp(s, -wp, prec, rounding)
def mpf_expint(n, x, prec, rnd=round_fast, gamma=False):
"""
E_n(x), n an integer, x real
With gamma=True, computes Gamma(n,x) (upper incomplete gamma function)
Returns (real, None) if real, otherwise (real, imag)
The imaginary part is an optional branch cut term
"""
sign, man, exp, bc = x
if not man:
if gamma:
if x == fzero:
# Actually gamma function pole
if n <= 0:
return finf, None
return mpf_gamma_int(n, prec, rnd), None
if x == finf:
return fzero, None
# TODO: could return finite imaginary value at -inf
return fnan, fnan
else:
if x == fzero:
if n > 1:
return from_rational(1, n-1, prec, rnd), None
else:
return finf, None
if x == finf:
return fzero, None
return fnan, fnan
n_orig = n
if gamma:
n = 1-n
wp = prec + 20
xmag = exp + bc
# Beware of near-poles
if xmag < -10:
raise NotImplementedError
nmag = bitcount(abs(n))
have_imag = n > 0 and sign
negx = mpf_neg(x)
# Skip series if direct convergence
if n == 0 or 2*nmag - xmag < -wp:
if gamma:
v = mpf_exp(negx, wp)
re = mpf_mul(v, mpf_pow_int(x, n_orig-1, wp), prec, rnd)
else:
v = mpf_exp(negx, wp)
re = mpf_div(v, x, prec, rnd)
else:
# Finite number of terms, or...
can_use_asymptotic_series = -3*wp < n <= 0
# ...large enough?
if not can_use_asymptotic_series:
xi = abs(to_int(x))
m = min(max(1, xi-n), 2*wp)
siz = -n*nmag + (m+n)*bitcount(abs(m+n)) - m*xmag - (144*m//100)
tol = -wp-10
can_use_asymptotic_series = siz < tol
if can_use_asymptotic_series:
r = ((-MPZ_ONE) << (wp+wp)) // to_fixed(x, wp)
m = n
t = r*m
s = MPZ_ONE << wp
while m and t:
s += t
m += 1
t = (m*r*t) >> wp
v = mpf_exp(negx, wp)
if gamma:
# ~ exp(-x) * x^(n-1) * (1 + ...)
v = mpf_mul(v, mpf_pow_int(x, n_orig-1, wp), wp)
else:
# ~ exp(-x)/x * (1 + ...)
v = mpf_div(v, x, wp)
re = mpf_mul(v, from_man_exp(s, -wp), prec, rnd)
elif n == 1:
re = mpf_neg(mpf_ei(negx, prec, rnd))
elif n > 0 and n < 3*wp:
T1 = mpf_neg(mpf_ei(negx, wp))
if gamma:
if n_orig & 1:
T1 = mpf_neg(T1)
else:
T1 = mpf_mul(T1, mpf_pow_int(negx, n-1, wp), wp)
r = t = to_fixed(x, wp)
facs = [1] * (n-1)
for k in range(1,n-1):
facs[k] = facs[k-1] * k
facs = facs[::-1]
s = facs[0] << wp
for k in range(1, n-1):
if k & 1:
s -= facs[k] * t
else:
s += facs[k] * t
t = (t*r) >> wp
T2 = from_man_exp(s, -wp, wp)
T2 = mpf_mul(T2, mpf_exp(negx, wp))
if gamma:
T2 = mpf_mul(T2, mpf_pow_int(x, n_orig, wp), wp)
R = mpf_add(T1, T2)
re = mpf_div(R, from_int(ifac(n-1)), prec, rnd)
else:
raise NotImplementedError
if have_imag:
M = from_int(-ifac(n-1))
if gamma:
im = mpf_div(mpf_pi(wp), M, prec, rnd)
else:
im = mpf_div(mpf_mul(mpf_pi(wp), mpf_pow_int(negx, n_orig-1, wp), wp), M, prec, rnd)
return re, im
else:
return re, None
def mpf_expint(n, x, prec, rnd=round_fast, gamma=False):
"""
E_n(x), n an integer, x real
With gamma=True, computes Gamma(n,x) (upper incomplete gamma function)
Returns (real, None) if real, otherwise (real, imag)
The imaginary part is an optional branch cut term
"""
sign, man, exp, bc = x
if not man:
if gamma:
if x == fzero:
# Actually gamma function pole
if n <= 0:
return finf, None
return mpf_gamma_int(n, prec, rnd), None
if x == finf:
return fzero, None
# TODO: could return finite imaginary value at -inf
return fnan, fnan
else:
if x == fzero:
if n > 1:
return from_rational(1, n - 1, prec, rnd), None
else:
return finf, None
if x == finf:
return fzero, None
return fnan, fnan
n_orig = n
if gamma:
n = 1 - n
wp = prec + 20
xmag = exp + bc
# Beware of near-poles
if xmag < -10:
raise NotImplementedError
nmag = bitcount(abs(n))
have_imag = n > 0 and sign
negx = mpf_neg(x)
# Skip series if direct convergence
if n == 0 or 2 * nmag - xmag < -wp:
if gamma:
v = mpf_exp(negx, wp)
re = mpf_mul(v, mpf_pow_int(x, n_orig - 1, wp), prec, rnd)
else:
v = mpf_exp(negx, wp)
re = mpf_div(v, x, prec, rnd)
else:
# Finite number of terms, or...
can_use_asymptotic_series = -3 * wp < n <= 0
# ...large enough?
if not can_use_asymptotic_series:
xi = abs(to_int(x))
m = min(max(1, xi - n), 2 * wp)
siz = -n * nmag + (m + n) * bitcount(abs(m + n)) - m * xmag - (
144 * m // 100)
tol = -wp - 10
can_use_asymptotic_series = siz < tol
if can_use_asymptotic_series:
r = ((-MPZ_ONE) << (wp + wp)) // to_fixed(x, wp)
m = n
t = r * m
s = MPZ_ONE << wp
while m and t:
s += t
m += 1
t = (m * r * t) >> wp
v = mpf_exp(negx, wp)
if gamma:
# ~ exp(-x) * x^(n-1) * (1 + ...)
v = mpf_mul(v, mpf_pow_int(x, n_orig - 1, wp), wp)
else:
# ~ exp(-x)/x * (1 + ...)
v = mpf_div(v, x, wp)
re = mpf_mul(v, from_man_exp(s, -wp), prec, rnd)
elif n == 1:
re = mpf_neg(mpf_ei(negx, prec, rnd))
elif n > 0 and n < 3 * wp:
T1 = mpf_neg(mpf_ei(negx, wp))
if gamma:
if n_orig & 1:
T1 = mpf_neg(T1)
else:
T1 = mpf_mul(T1, mpf_pow_int(negx, n - 1, wp), wp)
r = t = to_fixed(x, wp)
facs = [1] * (n - 1)
for k in range(1, n - 1):
facs[k] = facs[k - 1] * k
facs = facs[::-1]
s = facs[0] << wp
for k in range(1, n - 1):
if k & 1:
s -= facs[k] * t
else:
s += facs[k] * t
t = (t * r) >> wp
T2 = from_man_exp(s, -wp, wp)
T2 = mpf_mul(T2, mpf_exp(negx, wp))
if gamma:
T2 = mpf_mul(T2, mpf_pow_int(x, n_orig, wp), wp)
R = mpf_add(T1, T2)
re = mpf_div(R, from_int(ifac(n - 1)), prec, rnd)
else:
raise NotImplementedError
if have_imag:
M = from_int(-ifac(n - 1))
if gamma:
im = mpf_div(mpf_pi(wp), M, prec, rnd)
else:
im = mpf_div(
mpf_mul(mpf_pi(wp), mpf_pow_int(negx, n_orig - 1, wp), wp), M,
prec, rnd)
return re, im
else:
return re, None
