def mpc_exp(z, prec, rnd=round_fast):
"""
Complex exponential function.
We use the direct formula exp(a+bi) = exp(a) * (cos(b) + sin(b)*i)
for the computation. This formula is very nice because it is
pefectly stable; since we just do real multiplications, the only
numerical errors that can creep in are single-ulp rounding errors.
The formula is efficient since mpmath's real exp is quite fast and
since we can compute cos and sin simultaneously.
It is no problem if a and b are large; if the implementations of
exp/cos/sin are accurate and efficient for all real numbers, then
so is this function for all complex numbers.
"""
a, b = z
if a == fzero:
return mpf_cos_sin(b, prec, rnd)
if b == fzero:
return mpf_exp(a, prec, rnd), fzero
mag = mpf_exp(a, prec + 4, rnd)
c, s = mpf_cos_sin(b, prec + 4, rnd)
re = mpf_mul(mag, c, prec, rnd)
im = mpf_mul(mag, s, prec, rnd)
return re, im
def mpc_exp(z, prec, rnd=round_fast):
"""
Complex exponential function.
We use the direct formula exp(a+bi) = exp(a) * (cos(b) + sin(b)*i)
for the computation. This formula is very nice because it is
pefectly stable; since we just do real multiplications, the only
numerical errors that can creep in are single-ulp rounding errors.
The formula is efficient since mpmath's real exp is quite fast and
since we can compute cos and sin simultaneously.
It is no problem if a and b are large; if the implementations of
exp/cos/sin are accurate and efficient for all real numbers, then
so is this function for all complex numbers.
"""
a, b = z
if a == fzero:
return mpf_cos_sin(b, prec, rnd)
if b == fzero:
return mpf_exp(a, prec, rnd), fzero
mag = mpf_exp(a, prec + 4, rnd)
c, s = mpf_cos_sin(b, prec + 4, rnd)
re = mpf_mul(mag, c, prec, rnd)
im = mpf_mul(mag, s, prec, rnd)
return re, im
def mpc_expj(z, prec, rnd='f'):
re, im = z
if im == fzero:
return mpf_cos_sin(re, prec, rnd)
if re == fzero:
return mpf_exp(mpf_neg(im), prec, rnd), fzero
ey = mpf_exp(mpf_neg(im), prec + 10)
c, s = mpf_cos_sin(re, prec + 10)
re = mpf_mul(ey, c, prec, rnd)
im = mpf_mul(ey, s, prec, rnd)
return re, im
def mpc_expj(z, prec, rnd="f"):
re, im = z
if im == fzero:
return mpf_cos_sin(re, prec, rnd)
if re == fzero:
return mpf_exp(mpf_neg(im), prec, rnd), fzero
ey = mpf_exp(mpf_neg(im), prec + 10)
c, s = mpf_cos_sin(re, prec + 10)
re = mpf_mul(ey, c, prec, rnd)
im = mpf_mul(ey, s, prec, rnd)
return re, im
def mpc_cos_sin(z, prec, rnd=round_fast):
a, b = z
if a == fzero:
ch, sh = mpf_cosh_sinh(b, prec, rnd)
return (ch, fzero), (fzero, sh)
if b == fzero:
c, s = mpf_cos_sin(a, prec, rnd)
return (c, fzero), (s, fzero)
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
cre = mpf_mul(c, ch, prec, rnd)
cim = mpf_mul(s, sh, prec, rnd)
sre = mpf_mul(s, ch, prec, rnd)
sim = mpf_mul(c, sh, prec, rnd)
return (cre, mpf_neg(cim)), (sre, sim)
def mpc_cos_sin(z, prec, rnd=round_fast):
a, b = z
if a == fzero:
ch, sh = mpf_cosh_sinh(b, prec, rnd)
return (ch, fzero), (fzero, sh)
if b == fzero:
c, s = mpf_cos_sin(a, prec, rnd)
return (c, fzero), (s, fzero)
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
cre = mpf_mul(c, ch, prec, rnd)
cim = mpf_mul(s, sh, prec, rnd)
sre = mpf_mul(s, ch, prec, rnd)
sim = mpf_mul(c, sh, prec, rnd)
return (cre, mpf_neg(cim)), (sre, sim)
def cos_sin_quadrant(x, wp):
sign, man, exp, bc = x
if x == fzero:
return fone, fzero, 0
# TODO: combine evaluation code to avoid duplicate modulo
c, s = mpf_cos_sin(x, wp)
t, n, wp_ = mod_pi2(man, exp, exp + bc, 15)
if sign:
n = -1 - n
return c, s, n
def cos_sin_quadrant(x, wp):
sign, man, exp, bc = x
if x == fzero:
return fone, fzero, 0
# TODO: combine evaluation code to avoid duplicate modulo
c, s = mpf_cos_sin(x, wp)
t, n, wp_ = mod_pi2(man, exp, exp+bc, 15)
if sign:
n = -1-n
return c, s, n
def mpc_sin(z, prec, rnd=round_fast):
"""Complex sine. We have sin(a+bi) = sin(a)*cosh(b) +
cos(a)*sinh(b)*i. See the docstring for mpc_cos for additional
comments."""
a, b = z
if a == fzero:
return fzero, mpf_sinh(b, prec, rnd)
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
re = mpf_mul(s, ch, prec, rnd)
im = mpf_mul(c, sh, prec, rnd)
return re, im
def mpc_sin(z, prec, rnd=round_fast):
"""Complex sine. We have sin(a+bi) = sin(a)*cosh(b) +
cos(a)*sinh(b)*i. See the docstring for mpc_cos for additional
comments."""
a, b = z
if a == fzero:
return fzero, mpf_sinh(b, prec, rnd)
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
re = mpf_mul(s, ch, prec, rnd)
im = mpf_mul(c, sh, prec, rnd)
return re, im
def mpc_cos(z, prec, rnd=round_fast):
"""Complex cosine. The formula used is cos(a+bi) = cos(a)*cosh(b) -
sin(a)*sinh(b)*i.
The same comments apply as for the complex exp: only real
multiplications are pewrormed, so no cancellation errors are
possible. The formula is also efficient since we can compute both
pairs (cos, sin) and (cosh, sinh) in single stwps."""
a, b = z
if a == fzero:
return mpf_cosh(b, prec, rnd), fzero
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
re = mpf_mul(c, ch, prec, rnd)
im = mpf_mul(s, sh, prec, rnd)
return re, mpf_neg(im)
def mpc_cos(z, prec, rnd=round_fast):
"""Complex cosine. The formula used is cos(a+bi) = cos(a)*cosh(b) -
sin(a)*sinh(b)*i.
The same comments apply as for the complex exp: only real
multiplications are pewrormed, so no cancellation errors are
possible. The formula is also efficient since we can compute both
pairs (cos, sin) and (cosh, sinh) in single stwps."""
a, b = z
if a == fzero:
return mpf_cosh(b, prec, rnd), fzero
wp = prec + 6
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
re = mpf_mul(c, ch, prec, rnd)
im = mpf_mul(s, sh, prec, rnd)
return re, mpf_neg(im)
def mpc_tan(z, prec, rnd=round_fast):
"""Complex tangent. Computed as tan(a+bi) = sin(2a)/M + sinh(2b)/M*i
where M = cos(2a) + cosh(2b)."""
a, b = z
asign, aman, aexp, abc = a
bsign, bman, bexp, bbc = b
if b == fzero: return mpf_tan(a, prec, rnd), fzero
if a == fzero: return fzero, mpf_tanh(b, prec, rnd)
wp = prec + 15
a = mpf_shift(a, 1)
b = mpf_shift(b, 1)
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
# TODO: handle cancellation when c ~= -1 and ch ~= 1
mag = mpf_add(c, ch, wp)
re = mpf_div(s, mag, prec, rnd)
im = mpf_div(sh, mag, prec, rnd)
return re, im
def mpc_tan(z, prec, rnd=round_fast):
"""Complex tangent. Computed as tan(a+bi) = sin(2a)/M + sinh(2b)/M*i
where M = cos(2a) + cosh(2b)."""
a, b = z
asign, aman, aexp, abc = a
bsign, bman, bexp, bbc = b
if b == fzero: return mpf_tan(a, prec, rnd), fzero
if a == fzero: return fzero, mpf_tanh(b, prec, rnd)
wp = prec + 15
a = mpf_shift(a, 1)
b = mpf_shift(b, 1)
c, s = mpf_cos_sin(a, wp)
ch, sh = mpf_cosh_sinh(b, wp)
# TODO: handle cancellation when c ~= -1 and ch ~= 1
mag = mpf_add(c, ch, wp)
re = mpf_div(s, mag, prec, rnd)
im = mpf_div(sh, mag, prec, rnd)
return re, im
def cos_sin_fixed_prod(x, wp):
cos, sin = mpf_cos_sin(from_man_exp(x, -2*wp), wp)
sign, man, exp, bc = cos
if sign:
man = -man
offset = exp + wp
if offset >= 0:
cos = man << offset
else:
cos = man >> (-offset)
sign, man, exp, bc = sin
if sign:
man = -man
offset = exp + wp
if offset >= 0:
sin = man << offset
else:
sin = man >> (-offset)
return cos, sin
def cos_sin_fixed_prod(x, wp):
cos, sin = mpf_cos_sin(from_man_exp(x, -2 * wp), wp)
sign, man, exp, bc = cos
if sign:
man = -man
offset = exp + wp
if offset >= 0:
cos = man << offset
else:
cos = man >> (-offset)
sign, man, exp, bc = sin
if sign:
man = -man
offset = exp + wp
if offset >= 0:
sin = man << offset
else:
sin = man >> (-offset)
return cos, sin
def mpc_zeta(s, prec, rnd=round_fast, alt=0, force=False):
re, im = s
if im == fzero:
return mpf_zeta(re, prec, rnd, alt), fzero
# slow for large s
if (not force) and mpf_gt(mpc_abs(s, 10), from_int(prec)):
raise NotImplementedError
wp = prec + 20
# Near pole
r = mpc_sub(mpc_one, s, wp)
asign, aman, aexp, abc = mpc_abs(r, 10)
pole_dist = -2*(aexp+abc)
if pole_dist > wp:
if alt:
q = mpf_ln2(wp)
y = mpf_mul(q, mpf_euler(wp), wp)
g = mpf_shift(mpf_mul(q, q, wp), -1)
g = mpf_sub(y, g)
z = mpc_mul_mpf(r, mpf_neg(g), wp)
z = mpc_add_mpf(z, q, wp)
return mpc_pos(z, prec, rnd)
else:
q = mpc_neg(mpc_div(mpc_one, r, wp))
q = mpc_add_mpf(q, mpf_euler(wp), wp)
return mpc_pos(q, prec, rnd)
else:
wp += max(0, pole_dist)
# Reflection formula. To be rigorous, we should reflect to the left of
# re = 1/2 (see comments for mpf_zeta), but this leads to unnecessary
# slowdown for interesting values of s
if mpf_lt(re, fzero):
# XXX: could use the separate refl. formula for Dirichlet eta
if alt:
q = mpc_sub(mpc_one, mpc_pow(mpc_two, mpc_sub(mpc_one, s, wp),
wp), wp)
return mpc_mul(mpc_zeta(s, wp), q, prec, rnd)
# XXX: -1 should be done exactly
y = mpc_sub(mpc_one, s, 10*wp)
a = mpc_gamma(y, wp)
b = mpc_zeta(y, wp)
c = mpc_sin_pi(mpc_shift(s, -1), wp)
rsign, rman, rexp, rbc = re
isign, iman, iexp, ibc = im
mag = max(rexp+rbc, iexp+ibc)
wp2 = wp + mag
pi = mpf_pi(wp+wp2)
pi2 = (mpf_shift(pi, 1), fzero)
d = mpc_div_mpf(mpc_pow(pi2, s, wp2), pi, wp2)
return mpc_mul(a,mpc_mul(b,mpc_mul(c,d,wp),wp),prec,rnd)
n = int(wp/2.54 + 5)
n += int(0.9*abs(to_int(im)))
d = borwein_coefficients(n)
ref = to_fixed(re, wp)
imf = to_fixed(im, wp)
tre = MPZ_ZERO
tim = MPZ_ZERO
one = MPZ_ONE << wp
one_2wp = MPZ_ONE << (2*wp)
critical_line = re == fhalf
for k in xrange(n):
log = log_int_fixed(k+1, wp)
# A square root is much cheaper than an exp
if critical_line:
w = one_2wp // sqrt_fixed((k+1) << wp, wp)
else:
w = to_fixed(mpf_exp(from_man_exp(-ref*log, -2*wp), wp), wp)
if k & 1:
w *= (d[n] - d[k])
else:
w *= (d[k] - d[n])
wre, wim = mpf_cos_sin(from_man_exp(-imf * log, -2*wp), wp)
tre += (w * to_fixed(wre, wp)) >> wp
tim += (w * to_fixed(wim, wp)) >> wp
tre //= (-d[n])
tim //= (-d[n])
tre = from_man_exp(tre, -wp, wp)
tim = from_man_exp(tim, -wp, wp)
if alt:
return mpc_pos((tre, tim), prec, rnd)
else:
q = mpc_sub(mpc_one, mpc_pow(mpc_two, r, wp), wp)
return mpc_div((tre, tim), q, prec, rnd)
Complex exponential function.
We use the direct formula exp(a+bi) = exp(a) * (cos(b) + sin(b)*i)
for the computation. This formula is very nice because it is
pefectly stable; since we just do real multiplications, the only
numerical errors that can creep in are single-ulp rounding errors.
The formula is efficient since mpmath's real exp is quite fast and
since we can compute cos and sin simultaneously.
It is no problem if a and b are large; if the implementations of
exp/cos/sin are accurate and efficient for all real numbers, then
so is this function for all complex numbers.
"""
if a == fzero:
return mpf_cos_sin(b, prec, rnd)
mag = mpf_exp(a, prec + 4, rnd)
c, s = mpf_cos_sin(b, prec + 4, rnd)
re = mpf_mul(mag, c, prec, rnd)
im = mpf_mul(mag, s, prec, rnd)
return re, im
def mpc_log(z, prec, rnd=round_fast):
re = mpf_log_hypot(z[0], z[1], prec, rnd)
im = mpc_arg(z, prec, rnd)
return re, im
def mpc_cos((a, b), prec, rnd=round_fast):
"""Complex cosine. The formula used is cos(a+bi) = cos(a)*cosh(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 mpc_zeta(s, prec, rnd=round_fast, alt=0, force=False):
re, im = s
if im == fzero:
return mpf_zeta(re, prec, rnd, alt), fzero
# slow for large s
if (not force) and mpf_gt(mpc_abs(s, 10), from_int(prec)):
raise NotImplementedError
wp = prec + 20
# Near pole
r = mpc_sub(mpc_one, s, wp)
asign, aman, aexp, abc = mpc_abs(r, 10)
pole_dist = -2 * (aexp + abc)
if pole_dist > wp:
if alt:
q = mpf_ln2(wp)
y = mpf_mul(q, mpf_euler(wp), wp)
g = mpf_shift(mpf_mul(q, q, wp), -1)
g = mpf_sub(y, g)
z = mpc_mul_mpf(r, mpf_neg(g), wp)
z = mpc_add_mpf(z, q, wp)
return mpc_pos(z, prec, rnd)
else:
q = mpc_neg(mpc_div(mpc_one, r, wp))
q = mpc_add_mpf(q, mpf_euler(wp), wp)
return mpc_pos(q, prec, rnd)
else:
wp += max(0, pole_dist)
# Reflection formula. To be rigorous, we should reflect to the left of
# re = 1/2 (see comments for mpf_zeta), but this leads to unnecessary
# slowdown for interesting values of s
if mpf_lt(re, fzero):
# XXX: could use the separate refl. formula for Dirichlet eta
if alt:
q = mpc_sub(mpc_one, mpc_pow(mpc_two, mpc_sub(mpc_one, s, wp), wp),
wp)
return mpc_mul(mpc_zeta(s, wp), q, prec, rnd)
# XXX: -1 should be done exactly
y = mpc_sub(mpc_one, s, 10 * wp)
a = mpc_gamma(y, wp)
b = mpc_zeta(y, wp)
c = mpc_sin_pi(mpc_shift(s, -1), wp)
rsign, rman, rexp, rbc = re
isign, iman, iexp, ibc = im
mag = max(rexp + rbc, iexp + ibc)
wp2 = wp + mag
pi = mpf_pi(wp + wp2)
pi2 = (mpf_shift(pi, 1), fzero)
d = mpc_div_mpf(mpc_pow(pi2, s, wp2), pi, wp2)
return mpc_mul(a, mpc_mul(b, mpc_mul(c, d, wp), wp), prec, rnd)
n = int(wp / 2.54 + 5)
n += int(0.9 * abs(to_int(im)))
d = borwein_coefficients(n)
ref = to_fixed(re, wp)
imf = to_fixed(im, wp)
tre = MPZ_ZERO
tim = MPZ_ZERO
one = MPZ_ONE << wp
one_2wp = MPZ_ONE << (2 * wp)
critical_line = re == fhalf
for k in xrange(n):
log = log_int_fixed(k + 1, wp)
# A square root is much cheaper than an exp
if critical_line:
w = one_2wp // sqrt_fixed((k + 1) << wp, wp)
else:
w = to_fixed(mpf_exp(from_man_exp(-ref * log, -2 * wp), wp), wp)
if k & 1:
w *= (d[n] - d[k])
else:
w *= (d[k] - d[n])
wre, wim = mpf_cos_sin(from_man_exp(-imf * log, -2 * wp), wp)
tre += (w * to_fixed(wre, wp)) >> wp
tim += (w * to_fixed(wim, wp)) >> wp
tre //= (-d[n])
tim //= (-d[n])
tre = from_man_exp(tre, -wp, wp)
tim = from_man_exp(tim, -wp, wp)
if alt:
return mpc_pos((tre, tim), prec, rnd)
else:
q = mpc_sub(mpc_one, mpc_pow(mpc_two, r, wp), wp)
return mpc_div((tre, tim), q, prec, rnd)
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
Complex exponential function.
We use the direct formula exp(a+bi) = exp(a) * (cos(b) + sin(b)*i)
for the computation. This formula is very nice because it is
pefectly stable; since we just do real multiplications, the only
numerical errors that can creep in are single-ulp rounding errors.
The formula is efficient since mpmath's real exp is quite fast and
since we can compute cos and sin simultaneously.
It is no problem if a and b are large; if the implementations of
exp/cos/sin are accurate and efficient for all real numbers, then
so is this function for all complex numbers.
"""
if a == fzero:
return mpf_cos_sin(b, prec, rnd)
mag = mpf_exp(a, prec+4, rnd)
c, s = mpf_cos_sin(b, prec+4, rnd)
re = mpf_mul(mag, c, prec, rnd)
im = mpf_mul(mag, s, prec, rnd)
return re, im
def mpc_log(z, prec, rnd=round_fast):
re = mpf_log_hypot(z[0], z[1], prec, rnd)
im = mpc_arg(z, prec, rnd)
return re, im
def mpc_cos((a, b), prec, rnd=round_fast):
"""Complex cosine. The formula used is cos(a+bi) = cos(a)*cosh(b) -
sin(a)*sinh(b)*i.
