def mpf_atan2(y, x, prec, rnd=round_fast):
xsign, xman, xexp, xbc = x
ysign, yman, yexp, ybc = y
if not yman:
if y == fnan or x == fnan:
return fnan
if mpf_sign(x) >= 0:
return fzero
return mpf_pi(prec, rnd)
if ysign:
return mpf_neg(mpf_atan2(mpf_neg(y), x, prec, rnd))
if not xman:
if x == fnan:
return fnan
if x == finf:
return fzero
if x == fninf:
return mpf_pi(prec, rnd)
if not yman:
return fzero
return mpf_shift(mpf_pi(prec, rnd), -1)
tquo = mpf_atan(mpf_div(y, x, prec+4), prec+4)
if xsign:
return mpf_add(mpf_pi(prec+4), tquo, prec, rnd)
else:
return mpf_pos(tquo, prec, rnd)
def mpf_atan2(y, x, prec, rnd=round_fast):
xsign, xman, xexp, xbc = x
ysign, yman, yexp, ybc = y
if not yman:
if y == fnan or x == fnan:
return fnan
if mpf_sign(x) >= 0:
return fzero
return mpf_pi(prec, rnd)
if ysign:
return mpf_neg(mpf_atan2(mpf_neg(y), x, prec, rnd))
if not xman:
if x == fnan:
return fnan
if x == finf:
return fzero
if x == fninf:
return mpf_pi(prec, rnd)
if not yman:
return fzero
return mpf_shift(mpf_pi(prec, rnd), -1)
tquo = mpf_atan(mpf_div(y, x, prec + 4), prec + 4)
if xsign:
return mpf_add(mpf_pi(prec + 4), tquo, prec, rnd)
else:
return mpf_pos(tquo, prec, rnd)
def twinprime_fixed(prec):
def I(n):
return sum(
moebius(d) << (n // d) for d in xrange(1, n + 1) if not n % d) // n
wp = 2 * prec + 30
res = fone
primes = [from_rational(1, p, wp) for p in [2, 3, 5, 7]]
ppowers = [mpf_mul(p, p, wp) for p in primes]
n = 2
while 1:
a = mpf_zeta_int(n, wp)
for i in range(4):
a = mpf_mul(a, mpf_sub(fone, ppowers[i]), wp)
ppowers[i] = mpf_mul(ppowers[i], primes[i], wp)
a = mpf_pow_int(a, -I(n), wp)
if mpf_pos(a, prec + 10, 'n') == fone:
break
#from libmpf import to_str
#print n, to_str(mpf_sub(fone, a), 6)
res = mpf_mul(res, a, wp)
n += 1
res = mpf_mul(res, from_int(3 * 15 * 35), wp)
res = mpf_div(res, from_int(4 * 16 * 36), wp)
return to_fixed(res, prec)
def mpf_atan2(y, x, prec, rnd=round_fast):
xsign, xman, xexp, xbc = x
ysign, yman, yexp, ybc = y
if not yman:
if y == fzero and x != fnan:
if mpf_sign(x) >= 0:
return fzero
return mpf_pi(prec, rnd)
if y in (finf, fninf):
if x in (finf, fninf):
return fnan
# pi/2
if y == finf:
return mpf_shift(mpf_pi(prec, rnd), -1)
# -pi/2
return mpf_neg(mpf_shift(mpf_pi(prec, negative_rnd[rnd]), -1))
return fnan
if ysign:
return mpf_neg(mpf_atan2(mpf_neg(y), x, prec, negative_rnd[rnd]))
if not xman:
if x == fnan:
return fnan
if x == finf:
return fzero
if x == fninf:
return mpf_pi(prec, rnd)
if y == fzero:
return fzero
return mpf_shift(mpf_pi(prec, rnd), -1)
tquo = mpf_atan(mpf_div(y, x, prec+4), prec+4)
if xsign:
return mpf_add(mpf_pi(prec+4), tquo, prec, rnd)
else:
return mpf_pos(tquo, prec, rnd)
def mpf_bernoulli_huge(n, prec, rnd=None):
wp = prec + 10
piprec = wp + int(math.log(n, 2))
v = mpf_gamma_int(n + 1, wp)
v = mpf_mul(v, mpf_zeta_int(n, wp), wp)
v = mpf_mul(v, mpf_pow_int(mpf_pi(piprec), -n, wp))
v = mpf_shift(v, 1 - n)
if not n & 3:
v = mpf_neg(v)
return mpf_pos(v, prec, rnd or round_fast)
def mpf_bernoulli_huge(n, prec, rnd=None):
wp = prec + 10
piprec = wp + int(math.log(n,2))
v = mpf_gamma_int(n+1, wp)
v = mpf_mul(v, mpf_zeta_int(n, wp), wp)
v = mpf_mul(v, mpf_pow_int(mpf_pi(piprec), -n, wp))
v = mpf_shift(v, 1-n)
if not n & 3:
v = mpf_neg(v)
return mpf_pos(v, prec, rnd or round_fast)
def mpc_gamma(x, prec, rounding=round_fast, p1=1):
re, im = x
if im == fzero:
return mpf_gamma(re, prec, rounding, p1), fzero
# More precision is needed for enormous x.
sign, man, exp, bc = re
isign, iman, iexp, ibc = im
if re == fzero:
size = iexp + ibc
else:
size = max(exp + bc, iexp + ibc)
if size > 5:
size = int(size * math.log(size, 2))
reflect = sign or (exp + bc < -1)
wp = prec + max(0, size) + 25
# Near x = 0 pole (TODO: other poles)
if p1:
if size < -prec - 5:
return mpc_add_mpf(mpc_div(mpc_one, x, 2*prec+10), \
mpf_neg(mpf_euler(2*prec+10)), prec, rounding)
elif size < -5:
wp += (-2 * size)
if p1:
# Should be done exactly!
re_orig = re
re = mpf_sub(re, fone, bc + abs(exp) + 2)
x = re, im
if reflect:
# Reflection formula
wp += 15
pi = mpf_pi(wp), fzero
pix = mpc_mul(x, pi, wp)
t = mpc_sin_pi(x, wp)
u = mpc_sub(mpc_one, x, wp)
g = mpc_gamma(u, wp)
w = mpc_mul(t, g, wp)
return mpc_div(pix, w, wp)
# Extremely close to the real line?
# XXX: reflection formula
if iexp + ibc < -wp:
a = mpf_gamma(re_orig, wp)
b = mpf_psi0(re_orig, wp)
gamma_diff = mpf_div(a, b, wp)
return mpf_pos(a, prec, rounding), mpf_mul(gamma_diff, im, prec,
rounding)
sprec, a, c = get_spouge_coefficients(wp)
s = spouge_sum_complex(re, im, sprec, a, c)
# gamma = exp(log(x+a)*(x+0.5) - xpa) * s
repa = mpf_add(re, from_int(a), wp)
logxpa = mpc_log((repa, im), wp)
reph = mpf_add(re, fhalf, wp)
t = mpc_sub(mpc_mul(logxpa, (reph, im), wp), (repa, im), wp)
t = mpc_mul(mpc_exp(t, wp), s, prec, rounding)
return t
def mpf_zeta_int(s, prec, rnd=round_fast):
"""
Optimized computation of zeta(s) for an integer s.
"""
wp = prec + 20
s = int(s)
if s in zeta_int_cache and zeta_int_cache[s][0] >= wp:
return mpf_pos(zeta_int_cache[s][1], prec, rnd)
if s < 2:
if s == 1:
raise ValueError("zeta(1) pole")
if not s:
return mpf_neg(fhalf)
return mpf_div(mpf_bernoulli(-s + 1, wp), from_int(s - 1), prec, rnd)
# 2^-s term vanishes?
if s >= wp:
return mpf_perturb(fone, 0, prec, rnd)
# 5^-s term vanishes?
elif s >= wp * 0.431:
t = one = 1 << wp
t += 1 << (wp - s)
t += one // (MPZ_THREE**s)
t += 1 << max(0, wp - s * 2)
return from_man_exp(t, -wp, prec, rnd)
else:
# Fast enough to sum directly?
# Even better, we use the Euler product (idea stolen from pari)
m = (float(wp) / (s - 1) + 1)
if m < 30:
needed_terms = int(2.0**m + 1)
if needed_terms < int(wp / 2.54 + 5) / 10:
t = fone
for k in list_primes(needed_terms):
#print k, needed_terms
powprec = int(wp - s * math.log(k, 2))
if powprec < 2:
break
a = mpf_sub(fone, mpf_pow_int(from_int(k), -s, powprec),
wp)
t = mpf_mul(t, a, wp)
return mpf_div(fone, t, wp)
# Use Borwein's algorithm
n = int(wp / 2.54 + 5)
d = borwein_coefficients(n)
t = MPZ_ZERO
s = MPZ(s)
for k in xrange(n):
t += (((-1)**k * (d[k] - d[n])) << wp) // (k + 1)**s
t = (t << wp) // (-d[n])
t = (t << wp) // ((1 << wp) - (1 << (wp + 1 - s)))
if (s in zeta_int_cache
and zeta_int_cache[s][0] < wp) or (s not in zeta_int_cache):
zeta_int_cache[s] = (wp, from_man_exp(t, -wp - wp))
return from_man_exp(t, -wp - wp, prec, rnd)
def mpi_abs(s, prec):
sa, sb = s
sas = mpf_sign(sa)
sbs = mpf_sign(sb)
# Both points nonnegative?
if sas >= 0:
a = mpf_pos(sa, prec, round_floor)
b = mpf_pos(sb, prec, round_ceiling)
# Upper point nonnegative?
elif sbs >= 0:
a = fzero
negsa = mpf_neg(sa)
if mpf_lt(negsa, sb):
b = mpf_pos(sb, prec, round_ceiling)
else:
b = mpf_pos(negsa, prec, round_ceiling)
# Both negative?
else:
a = mpf_neg(sb, prec, round_floor)
b = mpf_neg(sa, prec, round_ceiling)
return a, b
def mpc_gamma(x, prec, rounding=round_fast, p1=1):
re, im = x
if im == fzero:
return mpf_gamma(re, prec, rounding, p1), fzero
# More precision is needed for enormous x.
sign, man, exp, bc = re
isign, iman, iexp, ibc = im
if re == fzero:
size = iexp+ibc
else:
size = max(exp+bc, iexp+ibc)
if size > 5:
size = int(size * math.log(size,2))
reflect = sign or (exp+bc < -1)
wp = prec + max(0, size) + 25
# Near x = 0 pole (TODO: other poles)
if p1:
if size < -prec-5:
return mpc_add_mpf(mpc_div(mpc_one, x, 2*prec+10), \
mpf_neg(mpf_euler(2*prec+10)), prec, rounding)
elif size < -5:
wp += (-2*size)
if p1:
# Should be done exactly!
re_orig = re
re = mpf_sub(re, fone, bc+abs(exp)+2)
x = re, im
if reflect:
# Reflection formula
wp += 15
pi = mpf_pi(wp), fzero
pix = mpc_mul(x, pi, wp)
t = mpc_sin_pi(x, wp)
u = mpc_sub(mpc_one, x, wp)
g = mpc_gamma(u, wp)
w = mpc_mul(t, g, wp)
return mpc_div(pix, w, wp)
# Extremely close to the real line?
# XXX: reflection formula
if iexp+ibc < -wp:
a = mpf_gamma(re_orig, wp)
b = mpf_psi0(re_orig, wp)
gamma_diff = mpf_div(a, b, wp)
return mpf_pos(a, prec, rounding), mpf_mul(gamma_diff, im, prec, rounding)
sprec, a, c = get_spouge_coefficients(wp)
s = spouge_sum_complex(re, im, sprec, a, c)
# gamma = exp(log(x+a)*(x+0.5) - xpa) * s
repa = mpf_add(re, from_int(a), wp)
logxpa = mpc_log((repa, im), wp)
reph = mpf_add(re, fhalf, wp)
t = mpc_sub(mpc_mul(logxpa, (reph, im), wp), (repa, im), wp)
t = mpc_mul(mpc_exp(t, wp), s, prec, rounding)
return t
def mpi_abs(s, prec):
sa, sb = s
sas = mpf_sign(sa)
sbs = mpf_sign(sb)
# Both points nonnegative?
if sas >= 0:
a = mpf_pos(sa, prec, round_floor)
b = mpf_pos(sb, prec, round_ceiling)
# Upper point nonnegative?
elif sbs >= 0:
a = fzero
negsa = mpf_neg(sa)
if mpf_lt(negsa, sb):
b = mpf_pos(sb, prec, round_ceiling)
else:
b = mpf_pos(negsa, prec, round_ceiling)
# Both negative?
else:
a = mpf_neg(sb, prec, round_floor)
b = mpf_neg(sa, prec, round_ceiling)
return a, b
def mpf_zeta_int(s, prec, rnd=round_fast):
"""
Optimized computation of zeta(s) for an integer s.
"""
wp = prec + 20
s = int(s)
if s in zeta_int_cache and zeta_int_cache[s][0] >= wp:
return mpf_pos(zeta_int_cache[s][1], prec, rnd)
if s < 2:
if s == 1:
raise ValueError("zeta(1) pole")
if not s:
return mpf_neg(fhalf)
return mpf_div(mpf_bernoulli(-s+1, wp), from_int(s-1), prec, rnd)
# 2^-s term vanishes?
if s >= wp:
return mpf_perturb(fone, 0, prec, rnd)
# 5^-s term vanishes?
elif s >= wp*0.431:
t = one = 1 << wp
t += 1 << (wp - s)
t += one // (MPZ_THREE ** s)
t += 1 << max(0, wp - s*2)
return from_man_exp(t, -wp, prec, rnd)
else:
# Fast enough to sum directly?
# Even better, we use the Euler product (idea stolen from pari)
m = (float(wp)/(s-1) + 1)
if m < 30:
needed_terms = int(2.0**m + 1)
if needed_terms < int(wp/2.54 + 5) / 10:
t = fone
for k in list_primes(needed_terms):
#print k, needed_terms
powprec = int(wp - s*math.log(k,2))
if powprec < 2:
break
a = mpf_sub(fone, mpf_pow_int(from_int(k), -s, powprec), wp)
t = mpf_mul(t, a, wp)
return mpf_div(fone, t, wp)
# Use Borwein's algorithm
n = int(wp/2.54 + 5)
d = borwein_coefficients(n)
t = MPZ_ZERO
s = MPZ(s)
for k in xrange(n):
t += (((-1)**k * (d[k] - d[n])) << wp) // (k+1)**s
t = (t << wp) // (-d[n])
t = (t << wp) // ((1 << wp) - (1 << (wp+1-s)))
if (s in zeta_int_cache and zeta_int_cache[s][0] < wp) or (s not in zeta_int_cache):
zeta_int_cache[s] = (wp, from_man_exp(t, -wp-wp))
return from_man_exp(t, -wp-wp, prec, rnd)
def twinprime_fixed(prec):
def I(n):
return sum(moebius(d)<<(n//d) for d in xrange(1,n+1) if not n%d)//n
wp = 2*prec + 30
res = fone
primes = [from_rational(1,p,wp) for p in [2,3,5,7]]
ppowers = [mpf_mul(p,p,wp) for p in primes]
n = 2
while 1:
a = mpf_zeta_int(n, wp)
for i in range(4):
a = mpf_mul(a, mpf_sub(fone, ppowers[i]), wp)
ppowers[i] = mpf_mul(ppowers[i], primes[i], wp)
a = mpf_pow_int(a, -I(n), wp)
if mpf_pos(a, prec+10, 'n') == fone:
break
#from libmpf import to_str
#print n, to_str(mpf_sub(fone, a), 6)
res = mpf_mul(res, a, wp)
n += 1
res = mpf_mul(res, from_int(3*15*35), wp)
res = mpf_div(res, from_int(4*16*36), wp)
return to_fixed(res, prec)
def __new__(cls, val=fzero, **kwargs):
"""A new mpf can be created from a Python float, an int, a
or a decimal string representing a number in floating-point
format."""
prec, rounding = prec_rounding
if kwargs:
prec = kwargs.get('prec', prec)
if 'dps' in kwargs:
prec = dps_to_prec(kwargs['dps'])
rounding = kwargs.get('rounding', rounding)
if type(val) is cls:
sign, man, exp, bc = val._mpf_
if (not man) and exp:
return val
return make_mpf(normalize(sign, man, exp, bc, prec, rounding))
elif type(val) is tuple:
if len(val) == 2:
return make_mpf(from_man_exp(val[0], val[1], prec, rounding))
if len(val) == 4:
sign, man, exp, bc = val
return make_mpf(normalize(sign, MP_BASE(man), exp, bc, prec, rounding))
raise ValueError
else:
return make_mpf(mpf_pos(mpf_convert_arg(val, prec, rounding), prec, rounding))
def __new__(cls, val=fzero, **kwargs):
"""A new mpf can be created from a Python float, an int, a
or a decimal string representing a number in floating-point
format."""
prec, rounding = prec_rounding
if kwargs:
prec = kwargs.get('prec', prec)
if 'dps' in kwargs:
prec = dps_to_prec(kwargs['dps'])
rounding = kwargs.get('rounding', rounding)
if type(val) is cls:
sign, man, exp, bc = val._mpf_
if (not man) and exp:
return val
return make_mpf(normalize(sign, man, exp, bc, prec, rounding))
elif type(val) is tuple:
if len(val) == 2:
return make_mpf(from_man_exp(val[0], val[1], prec, rounding))
if len(val) == 4:
sign, man, exp, bc = val
return make_mpf(normalize(sign, MP_BASE(man), exp, bc, prec, rounding))
raise ValueError
else:
return make_mpf(mpf_pos(mpf_convert_arg(val, prec, rounding), prec, rounding))
def mpc_ei(z, prec, rnd=round_fast, e1=False):
if e1:
z = mpc_neg(z)
a, b = z
asign, aman, aexp, abc = a
bsign, bman, bexp, bbc = b
if b == fzero:
if e1:
x = mpf_neg(mpf_ei(a, prec, rnd))
if not asign:
y = mpf_neg(mpf_pi(prec, rnd))
else:
y = fzero
return x, y
else:
return mpf_ei(a, prec, rnd), fzero
if a != fzero:
if not aman or not bman:
return (fnan, fnan)
wp = prec + 40
amag = aexp + abc
bmag = bexp + bbc
zmag = max(amag, bmag)
can_use_asymp = zmag > wp
if not can_use_asymp:
zabsint = abs(to_int(a)) + abs(to_int(b))
can_use_asymp = zabsint > int(wp * 0.693) + 20
try:
if can_use_asymp:
if zmag > wp:
v = fone, fzero
else:
zre = to_fixed(a, wp)
zim = to_fixed(b, wp)
vre, vim = complex_ei_asymptotic(zre, zim, wp)
v = from_man_exp(vre, -wp), from_man_exp(vim, -wp)
v = mpc_mul(v, mpc_exp(z, wp), wp)
v = mpc_div(v, z, wp)
if e1:
v = mpc_neg(v, prec, rnd)
else:
x, y = v
if bsign:
v = mpf_pos(x, prec, rnd), mpf_sub(y, mpf_pi(wp), prec,
rnd)
else:
v = mpf_pos(x, prec, rnd), mpf_add(y, mpf_pi(wp), prec,
rnd)
return v
except NoConvergence:
pass
#wp += 2*max(0,zmag)
wp += 2 * int(to_int(mpc_abs(z, 5)))
zre = to_fixed(a, wp)
zim = to_fixed(b, wp)
vre, vim = complex_ei_taylor(zre, zim, wp)
vre += euler_fixed(wp)
v = from_man_exp(vre, -wp), from_man_exp(vim, -wp)
if e1:
u = mpc_log(mpc_neg(z), wp)
else:
u = mpc_log(z, wp)
v = mpc_add(v, u, prec, rnd)
if e1:
v = mpc_neg(v)
return v
def mpc_pos(z, prec, rnd=round_fast):
a, b = z
return mpf_pos(a, prec, rnd), mpf_pos(b, prec, rnd)
def mpf_bernoulli(n, prec, rnd=None):
"""Computation of Bernoulli numbers (numerically)"""
if n < 2:
if n < 0:
raise ValueError("Bernoulli numbers only defined for n >= 0")
if n == 0:
return fone
if n == 1:
return mpf_neg(fhalf)
# For odd n > 1, the Bernoulli numbers are zero
if n & 1:
return fzero
# If precision is extremely high, we can save time by computing
# the Bernoulli number at a lower precision that is sufficient to
# obtain the exact fraction, round to the exact fraction, and
# convert the fraction back to an mpf value at the original precision
if prec > BERNOULLI_PREC_CUTOFF and prec > bernoulli_size(n)*1.1 + 1000:
p, q = bernfrac(n)
return from_rational(p, q, prec, rnd or round_floor)
if n > MAX_BERNOULLI_CACHE:
return mpf_bernoulli_huge(n, prec, rnd)
wp = prec + 30
# Reuse nearby precisions
wp += 32 - (prec & 31)
cached = bernoulli_cache.get(wp)
if cached:
numbers, state = cached
if n in numbers:
if not rnd:
return numbers[n]
return mpf_pos(numbers[n], prec, rnd)
m, bin, bin1 = state
if n - m > 10:
return mpf_bernoulli_huge(n, prec, rnd)
else:
if n > 10:
return mpf_bernoulli_huge(n, prec, rnd)
numbers = {0:fone}
m, bin, bin1 = state = [2, MPZ(10), MPZ_ONE]
bernoulli_cache[wp] = (numbers, state)
while m <= n:
#print m
case = m % 6
# Accurately estimate size of B_m so we can use
# fixed point math without using too much precision
szbm = bernoulli_size(m)
s = 0
sexp = max(0, szbm) - wp
if m < 6:
a = MPZ_ZERO
else:
a = bin1
for j in xrange(1, m//6+1):
usign, uman, uexp, ubc = u = numbers[m-6*j]
if usign:
uman = -uman
s += lshift(a*uman, uexp-sexp)
# Update inner binomial coefficient
j6 = 6*j
a *= ((m-5-j6)*(m-4-j6)*(m-3-j6)*(m-2-j6)*(m-1-j6)*(m-j6))
a //= ((4+j6)*(5+j6)*(6+j6)*(7+j6)*(8+j6)*(9+j6))
if case == 0: b = mpf_rdiv_int(m+3, f3, wp)
if case == 2: b = mpf_rdiv_int(m+3, f3, wp)
if case == 4: b = mpf_rdiv_int(-m-3, f6, wp)
s = from_man_exp(s, sexp, wp)
b = mpf_div(mpf_sub(b, s, wp), from_int(bin), wp)
numbers[m] = b
m += 2
# Update outer binomial coefficient
bin = bin * ((m+2)*(m+3)) // (m*(m-1))
if m > 6:
bin1 = bin1 * ((2+m)*(3+m)) // ((m-7)*(m-6))
state[:] = [m, bin, bin1]
return numbers[n]
def mpf_zeta(s, prec, rnd=round_fast, alt=0):
sign, man, exp, bc = s
if not man:
if s == fzero:
if alt:
return fhalf
else:
return mpf_neg(fhalf)
if s == finf:
return fone
return fnan
wp = prec + 20
# First term vanishes?
if (not sign) and (exp + bc > (math.log(wp, 2) + 2)):
return mpf_perturb(fone, alt, prec, rnd)
# Optimize for integer arguments
elif exp >= 0:
if alt:
if s == fone:
return mpf_ln2(prec, rnd)
z = mpf_zeta_int(to_int(s), wp, negative_rnd[rnd])
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_mul(z, q, prec, rnd)
else:
return mpf_zeta_int(to_int(s), prec, rnd)
# Negative: use the reflection formula
# Borwein only proves the accuracy bound for x >= 1/2. However, based on
# tests, the accuracy without reflection is quite good even some distance
# to the left of 1/2. XXX: verify this.
if sign:
# XXX: could use the separate refl. formula for Dirichlet eta
if alt:
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_mul(mpf_zeta(s, wp), q, prec, rnd)
# XXX: -1 should be done exactly
y = mpf_sub(fone, s, 10 * wp)
a = mpf_gamma(y, wp)
b = mpf_zeta(y, wp)
c = mpf_sin_pi(mpf_shift(s, -1), wp)
wp2 = wp + (exp + bc)
pi = mpf_pi(wp + wp2)
d = mpf_div(mpf_pow(mpf_shift(pi, 1), s, wp2), pi, wp2)
return mpf_mul(a, mpf_mul(b, mpf_mul(c, d, wp), wp), prec, rnd)
t = MP_ZERO
#wp += 16 - (prec & 15)
# Use Borwein's algorithm
n = int(wp / 2.54 + 5)
d = borwein_coefficients(n)
t = MP_ZERO
sf = to_fixed(s, wp)
for k in xrange(n):
u = from_man_exp(-sf * log_int_fixed(k + 1, wp), -2 * wp, wp)
esign, eman, eexp, ebc = mpf_exp(u, wp)
offset = eexp + wp
if offset >= 0:
w = ((d[k] - d[n]) * eman) << offset
else:
w = ((d[k] - d[n]) * eman) >> (-offset)
if k & 1:
t -= w
else:
t += w
t = t // (-d[n])
t = from_man_exp(t, -wp, wp)
if alt:
return mpf_pos(t, prec, rnd)
else:
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_div(t, q, prec, rnd)
def mpf_zeta(s, prec, rnd=round_fast, alt=0):
sign, man, exp, bc = s
if not man:
if s == fzero:
if alt:
return fhalf
else:
return mpf_neg(fhalf)
if s == finf:
return fone
return fnan
wp = prec + 20
# First term vanishes?
if (not sign) and (exp + bc > (math.log(wp,2) + 2)):
return mpf_perturb(fone, alt, prec, rnd)
# Optimize for integer arguments
elif exp >= 0:
if alt:
if s == fone:
return mpf_ln2(prec, rnd)
z = mpf_zeta_int(to_int(s), wp, negative_rnd[rnd])
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_mul(z, q, prec, rnd)
else:
return mpf_zeta_int(to_int(s), prec, rnd)
# Negative: use the reflection formula
# Borwein only proves the accuracy bound for x >= 1/2. However, based on
# tests, the accuracy without reflection is quite good even some distance
# to the left of 1/2. XXX: verify this.
if sign:
# XXX: could use the separate refl. formula for Dirichlet eta
if alt:
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_mul(mpf_zeta(s, wp), q, prec, rnd)
# XXX: -1 should be done exactly
y = mpf_sub(fone, s, 10*wp)
a = mpf_gamma(y, wp)
b = mpf_zeta(y, wp)
c = mpf_sin_pi(mpf_shift(s, -1), wp)
wp2 = wp + (exp+bc)
pi = mpf_pi(wp+wp2)
d = mpf_div(mpf_pow(mpf_shift(pi, 1), s, wp2), pi, wp2)
return mpf_mul(a,mpf_mul(b,mpf_mul(c,d,wp),wp),prec,rnd)
# Near pole
r = mpf_sub(fone, s, wp)
asign, aman, aexp, abc = mpf_abs(r)
pole_dist = -2*(aexp+abc)
if pole_dist > wp:
if alt:
return mpf_ln2(prec, rnd)
else:
q = mpf_neg(mpf_div(fone, r, wp))
return mpf_add(q, mpf_euler(wp), prec, rnd)
else:
wp += max(0, pole_dist)
t = MPZ_ZERO
#wp += 16 - (prec & 15)
# Use Borwein's algorithm
n = int(wp/2.54 + 5)
d = borwein_coefficients(n)
t = MPZ_ZERO
sf = to_fixed(s, wp)
for k in xrange(n):
u = from_man_exp(-sf*log_int_fixed(k+1, wp), -2*wp, wp)
esign, eman, eexp, ebc = mpf_exp(u, wp)
offset = eexp + wp
if offset >= 0:
w = ((d[k] - d[n]) * eman) << offset
else:
w = ((d[k] - d[n]) * eman) >> (-offset)
if k & 1:
t -= w
else:
t += w
t = t // (-d[n])
t = from_man_exp(t, -wp, wp)
if alt:
return mpf_pos(t, prec, rnd)
else:
q = mpf_sub(fone, mpf_pow(ftwo, mpf_sub(fone, s, wp), wp), wp)
return mpf_div(t, q, prec, rnd)
def mpc_ei(z, prec, rnd=round_fast, e1=False):
if e1:
z = mpc_neg(z)
a, b = z
asign, aman, aexp, abc = a
bsign, bman, bexp, bbc = b
if b == fzero:
if e1:
x = mpf_neg(mpf_ei(a, prec, rnd))
if not asign:
y = mpf_neg(mpf_pi(prec, rnd))
else:
y = fzero
return x, y
else:
return mpf_ei(a, prec, rnd), fzero
if a != fzero:
if not aman or not bman:
return (fnan, fnan)
wp = prec + 40
amag = aexp+abc
bmag = bexp+bbc
zmag = max(amag, bmag)
can_use_asymp = zmag > wp
if not can_use_asymp:
zabsint = abs(to_int(a)) + abs(to_int(b))
can_use_asymp = zabsint > int(wp*0.693) + 20
try:
if can_use_asymp:
if zmag > wp:
v = fone, fzero
else:
zre = to_fixed(a, wp)
zim = to_fixed(b, wp)
vre, vim = complex_ei_asymptotic(zre, zim, wp)
v = from_man_exp(vre, -wp), from_man_exp(vim, -wp)
v = mpc_mul(v, mpc_exp(z, wp), wp)
v = mpc_div(v, z, wp)
if e1:
v = mpc_neg(v, prec, rnd)
else:
x, y = v
if bsign:
v = mpf_pos(x, prec, rnd), mpf_sub(y, mpf_pi(wp), prec, rnd)
else:
v = mpf_pos(x, prec, rnd), mpf_add(y, mpf_pi(wp), prec, rnd)
return v
except NoConvergence:
pass
#wp += 2*max(0,zmag)
wp += 2*int(to_int(mpc_abs(z, 5)))
zre = to_fixed(a, wp)
zim = to_fixed(b, wp)
vre, vim = complex_ei_taylor(zre, zim, wp)
vre += euler_fixed(wp)
v = from_man_exp(vre,-wp), from_man_exp(vim,-wp)
if e1:
u = mpc_log(mpc_neg(z),wp)
else:
u = mpc_log(z,wp)
v = mpc_add(v, u, prec, rnd)
if e1:
v = mpc_neg(v)
return v
def mpf_nthroot(s, n, prec, rnd=round_fast):
"""nth-root of a positive number
Use the Newton method when faster, otherwise use x**(1/n)
"""
sign, man, exp, bc = s
if sign:
raise ComplexResult("nth root of a negative number")
if not man:
if s == fnan:
return fnan
if s == fzero:
if n > 0:
return fzero
if n == 0:
return fone
return finf
# Infinity
if not n:
return fnan
if n < 0:
return fzero
return finf
flag_inverse = False
if n < 2:
if n == 0:
return fone
if n == 1:
return mpf_pos(s, prec, rnd)
if n == -1:
return mpf_div(fone, s, prec, rnd)
# n < 0
rnd = reciprocal_rnd[rnd]
flag_inverse = True
extra_inverse = 5
prec += extra_inverse
n = -n
if n > 20 and (n >= 20000 or prec < int(233 + 28.3 * n**0.62)):
prec2 = prec + 10
fn = from_int(n)
nth = mpf_rdiv_int(1, fn, prec2)
r = mpf_pow(s, nth, prec2, rnd)
s = normalize(r[0], r[1], r[2], r[3], prec, rnd)
if flag_inverse:
return mpf_div(fone, s, prec-extra_inverse, rnd)
else:
return s
# Convert to a fixed-point number with prec2 bits.
prec2 = prec + 2*n - (prec%n)
# a few tests indicate that
# for 10 < n < 10**4 a bit more precision is needed
if n > 10:
prec2 += prec2//10
prec2 = prec2 - prec2%n
# Mantissa may have more bits than we need. Trim it down.
shift = bc - prec2
# Adjust exponents to make prec2 and exp+shift multiples of n.
sign1 = 0
es = exp+shift
if es < 0:
sign1 = 1
es = -es
if sign1:
shift += es%n
else:
shift -= es%n
man = rshift(man, shift)
extra = 10
exp1 = ((exp+shift-(n-1)*prec2)//n) - extra
rnd_shift = 0
if flag_inverse:
if rnd == 'u' or rnd == 'c':
rnd_shift = 1
else:
if rnd == 'd' or rnd == 'f':
rnd_shift = 1
man = nthroot_fixed(man+rnd_shift, n, prec2, exp1)
s = from_man_exp(man, exp1, prec, rnd)
if flag_inverse:
return mpf_div(fone, s, prec-extra_inverse, rnd)
else:
return s
def mpi_pos(s, prec):
sa, sb = s
a = mpf_pos(sa, prec, round_floor)
b = mpf_pos(sb, prec, round_ceiling)
return a, b
def mpc_pos(z, prec, rnd=round_fast):
a, b = z
return mpf_pos(a, prec, rnd), mpf_pos(b, prec, rnd)
def mpf_bernoulli(n, prec, rnd=None):
"""Computation of Bernoulli numbers (numerically)"""
if n < 2:
if n < 0:
raise ValueError("Bernoulli numbers only defined for n >= 0")
if n == 0:
return fone
if n == 1:
return mpf_neg(fhalf)
# For odd n > 1, the Bernoulli numbers are zero
if n & 1:
return fzero
# If precision is extremely high, we can save time by computing
# the Bernoulli number at a lower precision that is sufficient to
# obtain the exact fraction, round to the exact fraction, and
# convert the fraction back to an mpf value at the original precision
if prec > BERNOULLI_PREC_CUTOFF and prec > bernoulli_size(n) * 1.1 + 1000:
p, q = bernfrac(n)
return from_rational(p, q, prec, rnd or round_floor)
if n > MAX_BERNOULLI_CACHE:
return mpf_bernoulli_huge(n, prec, rnd)
wp = prec + 30
# Reuse nearby precisions
wp += 32 - (prec & 31)
cached = bernoulli_cache.get(wp)
if cached:
numbers, state = cached
if n in numbers:
if not rnd:
return numbers[n]
return mpf_pos(numbers[n], prec, rnd)
m, bin, bin1 = state
if n - m > 10:
return mpf_bernoulli_huge(n, prec, rnd)
else:
if n > 10:
return mpf_bernoulli_huge(n, prec, rnd)
numbers = {0: fone}
m, bin, bin1 = state = [2, MP_BASE(10), MP_ONE]
bernoulli_cache[wp] = (numbers, state)
while m <= n:
#print m
case = m % 6
# Accurately estimate size of B_m so we can use
# fixed point math without using too much precision
szbm = bernoulli_size(m)
s = 0
sexp = max(0, szbm) - wp
if m < 6:
a = MP_ZERO
else:
a = bin1
for j in xrange(1, m // 6 + 1):
usign, uman, uexp, ubc = u = numbers[m - 6 * j]
if usign:
uman = -uman
s += lshift(a * uman, uexp - sexp)
# Update inner binomial coefficient
j6 = 6 * j
a *= ((m - 5 - j6) * (m - 4 - j6) * (m - 3 - j6) * (m - 2 - j6) *
(m - 1 - j6) * (m - j6))
a //= ((4 + j6) * (5 + j6) * (6 + j6) * (7 + j6) * (8 + j6) *
(9 + j6))
if case == 0: b = mpf_rdiv_int(m + 3, f3, wp)
if case == 2: b = mpf_rdiv_int(m + 3, f3, wp)
if case == 4: b = mpf_rdiv_int(-m - 3, f6, wp)
s = from_man_exp(s, sexp, wp)
b = mpf_div(mpf_sub(b, s, wp), from_int(bin), wp)
numbers[m] = b
m += 2
# Update outer binomial coefficient
bin = bin * ((m + 2) * (m + 3)) // (m * (m - 1))
if m > 6:
bin1 = bin1 * ((2 + m) * (3 + m)) // ((m - 7) * (m - 6))
state[:] = [m, bin, bin1]
def mpi_mul(s, t, prec):
sa, sb = s
ta, tb = t
sas = mpf_sign(sa)
sbs = mpf_sign(sb)
tas = mpf_sign(ta)
tbs = mpf_sign(tb)
if sas == sbs == 0:
# Should maybe be undefined
if ta == fninf or tb == finf:
return fninf, finf
return fzero, fzero
if tas == tbs == 0:
# Should maybe be undefined
if sa == fninf or sb == finf:
return fninf, finf
return fzero, fzero
if sas >= 0:
# positive * positive
if tas >= 0:
a = mpf_mul(sa, ta, prec, round_floor)
b = mpf_mul(sb, tb, prec, round_ceiling)
if a == fnan:
a = fzero
if b == fnan:
b = finf
# positive * negative
elif tbs <= 0:
a = mpf_mul(sb, ta, prec, round_floor)
b = mpf_mul(sa, tb, prec, round_ceiling)
if a == fnan:
a = fninf
if b == fnan:
b = fzero
# positive * both signs
else:
a = mpf_mul(sb, ta, prec, round_floor)
b = mpf_mul(sb, tb, prec, round_ceiling)
if a == fnan:
a = fninf
if b == fnan:
b = finf
elif sbs <= 0:
# negative * positive
if tas >= 0:
a = mpf_mul(sa, tb, prec, round_floor)
b = mpf_mul(sb, ta, prec, round_ceiling)
if a == fnan:
a = fninf
if b == fnan:
b = fzero
# negative * negative
elif tbs <= 0:
a = mpf_mul(sb, tb, prec, round_floor)
b = mpf_mul(sa, ta, prec, round_ceiling)
if a == fnan:
a = fzero
if b == fnan:
b = finf
# negative * both signs
else:
a = mpf_mul(sb, tb, prec, round_floor)
b = mpf_mul(sa, ta, prec, round_ceiling)
if a == fnan:
a = fninf
if b == fnan:
b = finf
else:
# General case: perform all cross-multiplications and compare
# Since the multiplications can be done exactly, we need only
# do 4 (instead of 8: two for each rounding mode)
cases = [mpf_mul(sa, ta), mpf_mul(sa, tb), mpf_mul(sb, ta), mpf_mul(sb, tb)]
if fnan in cases:
a, b = (fninf, finf)
else:
cases = sorted(cases, cmp=mpf_cmp)
a = mpf_pos(cases[0], prec, round_floor)
b = mpf_pos(cases[-1], prec, round_ceiling)
return a, b
return rs + " + " + to_str(im, dps) + "j"
def mpc_add((a, b), (c, d), prec, rnd=round_fast):
return mpf_add(a, c, prec, rnd), mpf_add(b, d, prec, rnd)
def mpc_add_mpf((a, b), p, prec, rnd=round_fast):
return mpf_add(a, p, prec, rnd), b
def mpc_sub((a, b), (c, d), prec, rnd=round_fast):
return mpf_sub(a, c, prec, rnd), mpf_sub(b, d, prec, rnd)
def mpc_sub_mpf((a, b), p, prec, rnd=round_fast):
return mpf_sub(a, p, prec, rnd), b
def mpc_pos((a, b), prec, rnd=round_fast):
return mpf_pos(a, prec, rnd), mpf_pos(b, prec, rnd)
def mpc_neg((a, b), prec=None, rnd=round_fast):
return mpf_neg(a, prec, rnd), mpf_neg(b, prec, rnd)
def mpc_shift((a, b), n):
return mpf_shift(a, n), mpf_shift(b, n)
def mpc_abs((a, b), prec, rnd=round_fast):
"""Absolute value of a complex number, |a+bi|.
Returns an mpf value."""
return mpf_hypot(a, b, prec, rnd)
def mpc_arg((a, b), prec, rnd=round_fast):
"""Argument of a complex number. Returns an mpf value."""
return mpf_atan2(b, a, prec, rnd)
def mpc_add_mpf((a, b), p, prec, rnd=round_fast):
return mpf_add(a, p, prec, rnd), b
def mpc_sub((a, b), (c, d), prec, rnd=round_fast):
return mpf_sub(a, c, prec, rnd), mpf_sub(b, d, prec, rnd)
def mpc_sub_mpf((a, b), p, prec, rnd=round_fast):
return mpf_sub(a, p, prec, rnd), b
def mpc_pos((a, b), prec, rnd=round_fast):
return mpf_pos(a, prec, rnd), mpf_pos(b, prec, rnd)
def mpc_neg((a, b), prec=None, rnd=round_fast):
return mpf_neg(a, prec, rnd), mpf_neg(b, prec, rnd)
def mpc_shift((a, b), n):
return mpf_shift(a, n), mpf_shift(b, n)
def mpc_abs((a, b), prec, rnd=round_fast):
"""Absolute value of a complex number, |a+bi|.
Returns an mpf value."""
return mpf_hypot(a, b, prec, rnd)
def __pos__(s): return make_mpf(mpf_pos(s._mpf_, *prec_rounding)) def __neg__(s): return make_mpf(mpf_neg(s._mpf_, *prec_rounding))
def __pos__(s): return make_mpf(mpf_pos(s._mpf_, *prec_rounding)) def __neg__(s): return make_mpf(mpf_neg(s._mpf_, *prec_rounding))
def mpf_ci_si(x, prec, rnd=round_fast, which=2):
"""
Calculation of Ci(x), Si(x) for real x.
which = 0 -- returns (Ci(x), -)
which = 1 -- returns (Si(x), -)
which = 2 -- returns (Ci(x), Si(x))
Note: if x < 0, Ci(x) needs an additional imaginary term, pi*i.
"""
wp = prec + 20
sign, man, exp, bc = x
ci, si = None, None
if not man:
if x == fzero:
return (fninf, fzero)
if x == fnan:
return (x, x)
ci = fzero
if which != 0:
if x == finf:
si = mpf_shift(mpf_pi(prec, rnd), -1)
if x == fninf:
si = mpf_neg(mpf_shift(mpf_pi(prec, negative_rnd[rnd]), -1))
return (ci, si)
# For small x: Ci(x) ~ euler + log(x), Si(x) ~ x
mag = exp + bc
if mag < -wp:
if which != 0:
si = mpf_perturb(x, 1 - sign, prec, rnd)
if which != 1:
y = mpf_euler(wp)
xabs = mpf_abs(x)
ci = mpf_add(y, mpf_log(xabs, wp), prec, rnd)
return ci, si
# For huge x: Ci(x) ~ sin(x)/x, Si(x) ~ pi/2
elif mag > wp:
if which != 0:
if sign:
si = mpf_neg(mpf_pi(prec, negative_rnd[rnd]))
else:
si = mpf_pi(prec, rnd)
si = mpf_shift(si, -1)
if which != 1:
ci = mpf_div(mpf_sin(x, wp), x, prec, rnd)
return ci, si
else:
wp += abs(mag)
# Use an asymptotic series? The smallest value of n!/x^n
# occurs for n ~ x, where the magnitude is ~ exp(-x).
asymptotic = mag - 1 > math.log(wp, 2)
# Case 1: convergent series near 0
if not asymptotic:
if which != 0:
si = mpf_pos(mpf_ci_si_taylor(x, wp, 1), prec, rnd)
if which != 1:
ci = mpf_ci_si_taylor(x, wp, 0)
ci = mpf_add(ci, mpf_euler(wp), wp)
ci = mpf_add(ci, mpf_log(mpf_abs(x), wp), prec, rnd)
return ci, si
x = mpf_abs(x)
# Case 2: asymptotic series for x >> 1
xf = to_fixed(x, wp)
xr = (MP_ONE << (2 * wp)) // xf # 1/x
s1 = (MP_ONE << wp)
s2 = xr
t = xr
k = 2
while t:
t = -t
t = (t * xr * k) >> wp
k += 1
s1 += t
t = (t * xr * k) >> wp
k += 1
s2 += t
s1 = from_man_exp(s1, -wp)
s2 = from_man_exp(s2, -wp)
s1 = mpf_div(s1, x, wp)
s2 = mpf_div(s2, x, wp)
cos, sin = cos_sin(x, wp)
# Ci(x) = sin(x)*s1-cos(x)*s2
# Si(x) = pi/2-cos(x)*s1-sin(x)*s2
if which != 0:
si = mpf_add(mpf_mul(cos, s1), mpf_mul(sin, s2), wp)
si = mpf_sub(mpf_shift(mpf_pi(wp), -1), si, wp)
if sign:
si = mpf_neg(si)
si = mpf_pos(si, prec, rnd)
if which != 1:
ci = mpf_sub(mpf_mul(sin, s1), mpf_mul(cos, s2), prec, rnd)
return ci, si
def mpi_pos(s, prec):
sa, sb = s
a = mpf_pos(sa, prec, round_floor)
b = mpf_pos(sb, prec, round_ceiling)
return a, b
def mpf_ci_si(x, prec, rnd=round_fast, which=2):
"""
Calculation of Ci(x), Si(x) for real x.
which = 0 -- returns (Ci(x), -)
which = 1 -- returns (Si(x), -)
which = 2 -- returns (Ci(x), Si(x))
Note: if x < 0, Ci(x) needs an additional imaginary term, pi*i.
"""
wp = prec + 20
sign, man, exp, bc = x
ci, si = None, None
if not man:
if x == fzero:
return (fninf, fzero)
if x == fnan:
return (x, x)
ci = fzero
if which != 0:
if x == finf:
si = mpf_shift(mpf_pi(prec, rnd), -1)
if x == fninf:
si = mpf_neg(mpf_shift(mpf_pi(prec, negative_rnd[rnd]), -1))
return (ci, si)
# For small x: Ci(x) ~ euler + log(x), Si(x) ~ x
mag = exp+bc
if mag < -wp:
if which != 0:
si = mpf_perturb(x, 1-sign, prec, rnd)
if which != 1:
y = mpf_euler(wp)
xabs = mpf_abs(x)
ci = mpf_add(y, mpf_log(xabs, wp), prec, rnd)
return ci, si
# For huge x: Ci(x) ~ sin(x)/x, Si(x) ~ pi/2
elif mag > wp:
if which != 0:
if sign:
si = mpf_neg(mpf_pi(prec, negative_rnd[rnd]))
else:
si = mpf_pi(prec, rnd)
si = mpf_shift(si, -1)
if which != 1:
ci = mpf_div(mpf_sin(x, wp), x, prec, rnd)
return ci, si
else:
wp += abs(mag)
# Use an asymptotic series? The smallest value of n!/x^n
# occurs for n ~ x, where the magnitude is ~ exp(-x).
asymptotic = mag-1 > math.log(wp, 2)
# Case 1: convergent series near 0
if not asymptotic:
if which != 0:
si = mpf_pos(mpf_ci_si_taylor(x, wp, 1), prec, rnd)
if which != 1:
ci = mpf_ci_si_taylor(x, wp, 0)
ci = mpf_add(ci, mpf_euler(wp), wp)
ci = mpf_add(ci, mpf_log(mpf_abs(x), wp), prec, rnd)
return ci, si
x = mpf_abs(x)
# Case 2: asymptotic series for x >> 1
xf = to_fixed(x, wp)
xr = (MPZ_ONE<<(2*wp)) // xf # 1/x
s1 = (MPZ_ONE << wp)
s2 = xr
t = xr
k = 2
while t:
t = -t
t = (t*xr*k)>>wp
k += 1
s1 += t
t = (t*xr*k)>>wp
k += 1
s2 += t
s1 = from_man_exp(s1, -wp)
s2 = from_man_exp(s2, -wp)
s1 = mpf_div(s1, x, wp)
s2 = mpf_div(s2, x, wp)
cos, sin = mpf_cos_sin(x, wp)
# Ci(x) = sin(x)*s1-cos(x)*s2
# Si(x) = pi/2-cos(x)*s1-sin(x)*s2
if which != 0:
si = mpf_add(mpf_mul(cos, s1), mpf_mul(sin, s2), wp)
si = mpf_sub(mpf_shift(mpf_pi(wp), -1), si, wp)
if sign:
si = mpf_neg(si)
si = mpf_pos(si, prec, rnd)
if which != 1:
ci = mpf_sub(mpf_mul(sin, s1), mpf_mul(cos, s2), prec, rnd)
return ci, si
def mpi_mul(s, t, prec):
sa, sb = s
ta, tb = t
sas = mpf_sign(sa)
sbs = mpf_sign(sb)
tas = mpf_sign(ta)
tbs = mpf_sign(tb)
if sas == sbs == 0:
# Should maybe be undefined
if ta == fninf or tb == finf:
return fninf, finf
return fzero, fzero
if tas == tbs == 0:
# Should maybe be undefined
if sa == fninf or sb == finf:
return fninf, finf
return fzero, fzero
if sas >= 0:
# positive * positive
if tas >= 0:
a = mpf_mul(sa, ta, prec, round_floor)
b = mpf_mul(sb, tb, prec, round_ceiling)
if a == fnan: a = fzero
if b == fnan: b = finf
# positive * negative
elif tbs <= 0:
a = mpf_mul(sb, ta, prec, round_floor)
b = mpf_mul(sa, tb, prec, round_ceiling)
if a == fnan: a = fninf
if b == fnan: b = fzero
# positive * both signs
else:
a = mpf_mul(sb, ta, prec, round_floor)
b = mpf_mul(sb, tb, prec, round_ceiling)
if a == fnan: a = fninf
if b == fnan: b = finf
elif sbs <= 0:
# negative * positive
if tas >= 0:
a = mpf_mul(sa, tb, prec, round_floor)
b = mpf_mul(sb, ta, prec, round_ceiling)
if a == fnan: a = fninf
if b == fnan: b = fzero
# negative * negative
elif tbs <= 0:
a = mpf_mul(sb, tb, prec, round_floor)
b = mpf_mul(sa, ta, prec, round_ceiling)
if a == fnan: a = fzero
if b == fnan: b = finf
# negative * both signs
else:
a = mpf_mul(sa, tb, prec, round_floor)
b = mpf_mul(sa, ta, prec, round_ceiling)
if a == fnan: a = fninf
if b == fnan: b = finf
else:
# General case: perform all cross-multiplications and compare
# Since the multiplications can be done exactly, we need only
# do 4 (instead of 8: two for each rounding mode)
cases = [mpf_mul(sa, ta), mpf_mul(sa, tb), mpf_mul(sb, ta), mpf_mul(sb, tb)]
if fnan in cases:
a, b = (fninf, finf)
else:
cases = sorted(cases, cmp=mpf_cmp)
a = mpf_pos(cases[0], prec, round_floor)
b = mpf_pos(cases[-1], prec, round_ceiling)
return a, b
def mpf_nthroot(s, n, prec, rnd=round_fast):
"""nth-root of a positive number
Use the Newton method when faster, otherwise use x**(1/n)
"""
sign, man, exp, bc = s
if sign:
raise ComplexResult("nth root of a negative number")
if not man:
if s == fnan:
return fnan
if s == fzero:
if n > 0:
return fzero
if n == 0:
return fone
return finf
# Infinity
if not n:
return fnan
if n < 0:
return fzero
return finf
flag_inverse = False
if n < 2:
if n == 0:
return fone
if n == 1:
return mpf_pos(s, prec, rnd)
if n == -1:
return mpf_div(fone, s, prec, rnd)
# n < 0
rnd = reciprocal_rnd[rnd]
flag_inverse = True
extra_inverse = 5
prec += extra_inverse
n = -n
if n > 20 and (n >= 20000 or prec < int(233 + 28.3 * n**0.62)):
prec2 = prec + 10
fn = from_int(n)
nth = mpf_rdiv_int(1, fn, prec2)
r = mpf_pow(s, nth, prec2, rnd)
s = normalize(r[0], r[1], r[2], r[3], prec, rnd)
if flag_inverse:
return mpf_div(fone, s, prec-extra_inverse, rnd)
else:
return s
# Convert to a fixed-point number with prec2 bits.
prec2 = prec + 2*n - (prec%n)
# a few tests indicate that
# for 10 < n < 10**4 a bit more precision is needed
if n > 10:
prec2 += prec2//10
prec2 = prec2 - prec2%n
# Mantissa may have more bits than we need. Trim it down.
shift = bc - prec2
# Adjust exponents to make prec2 and exp+shift multiples of n.
sign1 = 0
es = exp+shift
if es < 0:
sign1 = 1
es = -es
if sign1:
shift += es%n
else:
shift -= es%n
man = rshift(man, shift)
extra = 10
exp1 = ((exp+shift-(n-1)*prec2)//n) - extra
rnd_shift = 0
if flag_inverse:
if rnd == 'u' or rnd == 'c':
rnd_shift = 1
else:
if rnd == 'd' or rnd == 'f':
rnd_shift = 1
man = nthroot_fixed(man+rnd_shift, n, prec2, exp1)
s = from_man_exp(man, exp1, prec, rnd)
if flag_inverse:
return mpf_div(fone, s, prec-extra_inverse, rnd)
else:
return s
