/* Extremely close to the branch point at -1/e, use the series expansion directly. */
int
acb_lambertw_try_near_branch_point(acb_t res, const acb_t z,
const acb_t ez1, const fmpz_t k, int flags, slong prec)
{
if (fmpz_is_zero(k) || (fmpz_is_one(k) && arb_is_negative(acb_imagref(z)))
|| (fmpz_equal_si(k, -1) && arb_is_nonnegative(acb_imagref(z))))
{
if (acb_contains_zero(ez1) ||
(arf_cmpabs_2exp_si(arb_midref(acb_realref(ez1)), -prec / 4.5 - 6) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(ez1)), -prec / 4.5 - 6) < 0))
{
acb_t t;
acb_init(t);
acb_mul_2exp_si(t, ez1, 1);
acb_sqrt(t, t, prec);
if (!fmpz_is_zero(k))
acb_neg(t, t);
acb_lambertw_branchpoint_series(res, t, 1, prec);
acb_clear(t);
return 1;
}
}
return 0;
}
void
acb_hypgeom_erf(acb_t res, const acb_t z, slong prec)
{
double x, y, absz2, logz;
slong prec2;
if (!acb_is_finite(z))
{
acb_indeterminate(res);
return;
}
if (acb_is_zero(z))
{
acb_zero(res);
return;
}
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 0) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 0) < 0))
{
acb_hypgeom_erf_1f1a(res, z, prec);
return;
}
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 64) > 0 ||
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 64) > 0))
{
acb_hypgeom_erf_asymp(res, z, prec, prec);
return;
}
x = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
y = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
absz2 = x * x + y * y;
logz = 0.5 * log(absz2);
if (logz - absz2 < -(prec + 8) * 0.69314718055994530942)
{
/* If the asymptotic term is small, we can
compute with reduced precision */
prec2 = FLINT_MIN(prec + 4 + (y*y - x*x - logz) * 1.4426950408889634074, (double) prec);
prec2 = FLINT_MAX(8, prec2);
prec2 = FLINT_MIN(prec2, prec);
acb_hypgeom_erf_asymp(res, z, prec, prec2);
}
else if (arf_cmpabs(arb_midref(acb_imagref(z)), arb_midref(acb_realref(z))) > 0)
{
acb_hypgeom_erf_1f1a(res, z, prec);
}
else
{
acb_hypgeom_erf_1f1b(res, z, prec);
}
}
void
arb_sech(arb_t res, const arb_t x, slong prec)
{
if (arf_cmpabs_2exp_si(arb_midref(x), 0) > 0)
{
arb_t t;
arb_init(t);
if (arf_sgn(arb_midref(x)) > 0)
{
arb_neg(t, x);
arb_exp(t, t, prec + 4);
}
else
{
arb_exp(t, x, prec + 4);
}
arb_mul(res, t, t, prec + 4);
arb_add_ui(res, res, 1, prec + 4);
arb_div(res, t, res, prec);
arb_mul_2exp_si(res, res, 1);
arb_clear(t);
}
else
{
arb_cosh(res, x, prec + 4);
arb_inv(res, res, prec);
}
}
void
arb_pow(arb_t z, const arb_t x, const arb_t y, slong prec)
{
if (arb_is_zero(y))
{
arb_one(z);
return;
}
if (arb_is_zero(x))
{
if (arb_is_positive(y))
arb_zero(z);
else
arb_indeterminate(z);
return;
}
if (arb_is_exact(y) && !arf_is_special(arb_midref(x)))
{
const arf_struct * ymid = arb_midref(y);
/* small half-integer or integer */
if (arf_cmpabs_2exp_si(ymid, BINEXP_LIMIT) < 0 &&
arf_is_int_2exp_si(ymid, -1))
{
fmpz_t e;
fmpz_init(e);
if (arf_is_int(ymid))
{
arf_get_fmpz_fixed_si(e, ymid, 0);
arb_pow_fmpz_binexp(z, x, e, prec);
}
else
{
arf_get_fmpz_fixed_si(e, ymid, -1);
arb_sqrt(z, x, prec + fmpz_bits(e));
arb_pow_fmpz_binexp(z, z, e, prec);
}
fmpz_clear(e);
return;
}
else if (arf_is_int(ymid) && arf_sgn(arb_midref(x)) < 0)
{
/* use (-x)^n = (-1)^n * x^n to avoid NaNs
at least at high enough precision */
int odd = !arf_is_int_2exp_si(ymid, 1);
_arb_pow_exp(z, x, 1, y, prec);
if (odd)
arb_neg(z, z);
return;
}
}
_arb_pow_exp(z, x, 0, y, prec);
}
void
acb_tan_pi(acb_t r, const acb_t z, slong prec)
{
if (arb_is_zero(acb_imagref(z)))
{
arb_tan_pi(acb_realref(r), acb_realref(z), prec);
arb_zero(acb_imagref(r));
}
else if (arb_is_zero(acb_realref(z)))
{
arb_t t;
arb_init(t);
arb_const_pi(t, prec + 4);
arb_mul(t, acb_imagref(z), t, prec + 4);
arb_tanh(acb_imagref(r), t, prec);
arb_zero(acb_realref(r));
arb_clear(t);
}
else
{
acb_t t;
acb_init(t);
if (arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 0) < 0)
{
acb_sin_cos_pi(r, t, z, prec + 4);
acb_div(r, r, t, prec);
}
else
{
acb_mul_2exp_si(t, z, 1);
if (arf_sgn(arb_midref(acb_imagref(z))) > 0)
{
acb_exp_pi_i(t, t, prec + 4);
acb_add_ui(r, t, 1, prec + 4);
acb_div(r, t, r, prec + 4);
acb_mul_2exp_si(r, r, 1);
acb_sub_ui(r, r, 1, prec);
acb_div_onei(r, r);
}
else
{
acb_neg(t, t);
acb_exp_pi_i(t, t, prec + 4);
acb_add_ui(r, t, 1, prec + 4);
acb_div(r, t, r, prec + 4);
acb_mul_2exp_si(r, r, 1);
acb_sub_ui(r, r, 1, prec);
acb_mul_onei(r, r);
}
}
acb_clear(t);
}
}
void
acb_hurwitz_zeta(acb_t z, const acb_t s, const acb_t a, slong prec)
{
if (acb_is_one(a) && acb_is_int(s) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(s)), FLINT_BITS - 1) < 0)
{
acb_zeta_si(z, arf_get_si(arb_midref(acb_realref(s)), ARF_RND_DOWN), prec);
return;
}
_acb_poly_zeta_cpx_series(z, s, a, 0, 1, prec);
}
void
arb_sin_cos_pi(arb_t s, arb_t c, const arb_t x, long prec)
{
arb_t t;
arb_t u;
fmpz_t v;
if (arf_cmpabs_2exp_si(arb_midref(x), FLINT_MAX(65536, (4*prec))) > 0)
{
arf_zero(arb_midref(s));
mag_one(arb_radref(s));
arf_zero(arb_midref(c));
mag_one(arb_radref(c));
return;
}
arb_init(t);
arb_init(u);
fmpz_init(v);
arb_mul_2exp_si(t, x, 1);
arf_get_fmpz(v, arb_midref(t), ARF_RND_NEAR);
arb_sub_fmpz(t, t, v, prec);
arb_const_pi(u, prec);
arb_mul(t, t, u, prec);
arb_mul_2exp_si(t, t, -1);
switch (fmpz_fdiv_ui(v, 4))
{
case 0:
arb_sin_cos(s, c, t, prec);
break;
case 1:
arb_sin_cos(c, s, t, prec);
arb_neg(c, c);
break;
case 2:
arb_sin_cos(s, c, t, prec);
arb_neg(s, s);
arb_neg(c, c);
break;
default:
arb_sin_cos(c, s, t, prec);
arb_neg(s, s);
break;
}
fmpz_clear(v);
arb_clear(t);
arb_clear(u);
}
int
acb_hypgeom_u_use_asymp(const acb_t z, slong prec)
{
double x, y;
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 0) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 0) < 0))
{
return 0;
}
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 64) > 0 ||
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 64) > 0))
{
return 1;
}
x = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
y = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
return sqrt(x * x + y * y) > prec * 0.69314718055994530942;
}
void
acb_pow_arb(acb_t z, const acb_t x, const arb_t y, long prec)
{
const arf_struct * ymid = arb_midref(y);
const mag_struct * yrad = arb_radref(y);
if (arb_is_zero(y))
{
acb_one(z);
return;
}
if (mag_is_zero(yrad))
{
/* small half-integer or integer */
if (arf_cmpabs_2exp_si(ymid, BINEXP_LIMIT) < 0 &&
arf_is_int_2exp_si(ymid, -1))
{
fmpz_t e;
fmpz_init(e);
if (arf_is_int(ymid))
{
arf_get_fmpz_fixed_si(e, ymid, 0);
acb_pow_fmpz_binexp(z, x, e, prec);
}
else
{
/* hack: give something finite here (should fix sqrt/rsqrt etc) */
if (arb_contains_zero(acb_imagref(x)) && arb_contains_nonpositive(acb_realref(x)))
{
_acb_pow_arb_exp(z, x, y, prec);
fmpz_clear(e);
return;
}
arf_get_fmpz_fixed_si(e, ymid, -1);
acb_sqrt(z, x, prec + fmpz_bits(e));
acb_pow_fmpz_binexp(z, z, e, prec);
}
fmpz_clear(e);
return;
}
}
_acb_pow_arb_exp(z, x, y, prec);
}
/* assumes no aliasing */
slong
acb_lambertw_initial(acb_t res, const acb_t z, const acb_t ez1, const fmpz_t k, slong prec)
{
/* Handle z very close to 0 on the principal branch. */
if (fmpz_is_zero(k) &&
(arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), -20) <= 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), -20) <= 0))
{
acb_set(res, z);
acb_submul(res, res, res, prec);
return 40; /* could be tightened... */
}
/* For moderate input not close to the branch point, compute a double
approximation as the initial value. */
if (fmpz_is_zero(k) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 400) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 400) < 0 &&
(arf_cmp_d(arb_midref(acb_realref(z)), -0.37) < 0 ||
arf_cmp_d(arb_midref(acb_realref(z)), -0.36) > 0 ||
arf_cmpabs_d(arb_midref(acb_imagref(z)), 0.01) > 0))
{
acb_lambertw_principal_d(res, z);
return 48;
}
/* Check if we are close to the branch point at -1/e. */
if ((fmpz_is_zero(k) || (fmpz_is_one(k) && arb_is_negative(acb_imagref(z)))
|| (fmpz_equal_si(k, -1) && arb_is_nonnegative(acb_imagref(z))))
&& ((arf_cmpabs_2exp_si(arb_midref(acb_realref(ez1)), -2) <= 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(ez1)), -2) <= 0)))
{
acb_t t;
acb_init(t);
acb_mul_2exp_si(t, ez1, 1);
mag_zero(arb_radref(acb_realref(t)));
mag_zero(arb_radref(acb_imagref(t)));
acb_mul_ui(t, t, 3, prec);
acb_sqrt(t, t, prec);
if (!fmpz_is_zero(k))
acb_neg(t, t);
acb_lambertw_branchpoint_series(res, t, 0, prec);
acb_clear(t);
return 1; /* todo: estimate */
}
acb_lambertw_initial_asymp(res, z, k, prec);
return 1; /* todo: estimate */
}
/* todo: use euler product for complex s, and check efficiency
for large negative integers */
void
acb_dirichlet_zeta(acb_t res, const acb_t s, slong prec)
{
acb_t a;
double cutoff;
if (acb_is_int(s) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(s)), FLINT_BITS - 1) < 0)
{
acb_zeta_si(res, arf_get_si(arb_midref(acb_realref(s)), ARF_RND_DOWN), prec);
return;
}
cutoff = 24.0 * prec * sqrt(prec);
if (arf_cmpabs_d(arb_midref(acb_imagref(s)), cutoff) >= 0 &&
arf_cmpabs_d(arb_midref(acb_realref(s)), 10 + prec * 0.1) <= 0)
{
acb_dirichlet_zeta_rs(res, s, 0, prec);
return;
}
acb_init(a);
acb_one(a);
if (arf_sgn(arb_midref(acb_realref(s))) < 0)
{
acb_t t, u, v;
slong wp = prec + 6;
acb_init(t);
acb_init(u);
acb_init(v);
acb_sub_ui(t, s, 1, wp);
/* 2 * (2pi)^(s-1) */
arb_const_pi(acb_realref(u), wp);
acb_mul_2exp_si(u, u, 1);
acb_pow(u, u, t, wp);
acb_mul_2exp_si(u, u, 1);
/* sin(pi*s/2) */
acb_mul_2exp_si(v, s, -1);
acb_sin_pi(v, v, wp);
acb_mul(u, u, v, wp);
/* gamma(1-s) zeta(1-s) */
acb_neg(t, t);
acb_gamma(v, t, wp);
acb_mul(u, u, v, wp);
acb_hurwitz_zeta(v, t, a, wp);
acb_mul(res, u, v, prec);
acb_clear(t);
acb_clear(u);
acb_clear(v);
}
else
{
acb_hurwitz_zeta(res, s, a, prec);
}
acb_clear(a);
}
void
acb_hypgeom_chebyshev_t(acb_t res, const acb_t n, const acb_t z, slong prec)
{
acb_t t;
if (acb_is_int(n) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(n)), FLINT_BITS - 1) < 0)
{
slong k = arf_get_si(arb_midref(acb_realref(n)), ARF_RND_DOWN);
acb_chebyshev_t_ui(res, FLINT_ABS(k), z, prec);
return;
}
if (acb_is_zero(z))
{
acb_mul_2exp_si(res, n, -1);
acb_cos_pi(res, res, prec);
return;
}
if (acb_is_one(z))
{
acb_one(res);
return;
}
acb_init(t);
acb_set_si(t, -1);
if (acb_equal(t, z))
{
acb_cos_pi(res, n, prec);
}
else
{
acb_sub_ui(t, z, 1, prec);
if (arf_cmpabs_2exp_si(arb_midref(acb_realref(t)), -2 - prec / 10) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(t)), -2 - prec / 10) < 0)
{
acb_t a, c;
acb_init(a);
acb_init(c);
acb_neg(a, n);
acb_one(c);
acb_mul_2exp_si(c, c, -1);
acb_neg(t, t);
acb_mul_2exp_si(t, t, -1);
acb_hypgeom_2f1(res, a, n, c, t, 0, prec);
acb_clear(a);
acb_clear(c);
}
else if (arb_is_nonnegative(acb_realref(t)))
{
acb_acosh(t, z, prec);
acb_mul(t, t, n, prec);
acb_cosh(res, t, prec);
}
else
{
acb_acos(t, z, prec);
acb_mul(t, t, n, prec);
acb_cos(res, t, prec);
}
}
acb_clear(t);
}
void
acb_hypgeom_airy(acb_t ai, acb_t aip, acb_t bi, acb_t bip, const acb_t z, slong prec)
{
arf_srcptr re, im;
double x, y, t, zmag, z15, term_est, airy_est, abstol;
slong n, wp;
if (!acb_is_finite(z))
{
if (ai != NULL) acb_indeterminate(ai);
if (aip != NULL) acb_indeterminate(aip);
if (bi != NULL) acb_indeterminate(bi);
if (bip != NULL) acb_indeterminate(bip);
return;
}
re = arb_midref(acb_realref(z));
im = arb_midref(acb_imagref(z));
wp = prec * 1.03 + 15;
/* tiny input -- use direct method and pick n without underflowing */
if (arf_cmpabs_2exp_si(re, -64) < 0 && arf_cmpabs_2exp_si(im, -64) < 0)
{
if (arf_cmpabs_2exp_si(re, -wp) < 0 && arf_cmpabs_2exp_si(im, -wp) < 0)
{
n = 1; /* very tiny input */
}
else
{
if (arf_cmpabs(re, im) > 0)
zmag = fmpz_get_d(ARF_EXPREF(re));
else
zmag = fmpz_get_d(ARF_EXPREF(im));
zmag = (zmag + 1) * (1.0 / LOG2);
n = wp / (-zmag) + 1;
}
acb_hypgeom_airy_direct(ai, aip, bi, bip, z, n, wp);
} /* huge input -- use asymptotics and pick n without overflowing */
else if ((arf_cmpabs_2exp_si(re, 64) > 0 || arf_cmpabs_2exp_si(im, 64) > 0))
{
if (arf_cmpabs_2exp_si(re, prec) > 0 || arf_cmpabs_2exp_si(im, prec) > 0)
{
n = 1; /* very huge input */
}
else
{
x = fmpz_get_d(ARF_EXPREF(re));
y = fmpz_get_d(ARF_EXPREF(im));
zmag = (FLINT_MAX(x, y) - 2) * (1.0 / LOG2);
n = asymp_pick_terms(wp, zmag);
n = FLINT_MAX(n, 1);
}
acb_hypgeom_airy_asymp(ai, aip, bi, bip, z, n, wp);
}
else /* moderate input */
{
x = arf_get_d(re, ARF_RND_DOWN);
y = arf_get_d(im, ARF_RND_DOWN);
zmag = sqrt(x * x + y * y);
z15 = zmag * sqrt(zmag);
if (zmag >= 4.0 && (n = asymp_pick_terms(wp, log(zmag))) != -1)
{
acb_hypgeom_airy_asymp(ai, aip, bi, bip, z, n, wp);
}
else if (zmag <= 1.5)
{
t = 3 * (wp * LOG2) / (2 * z15 * EXP1);
t = (wp * LOG2) / (2 * d_lambertw(t));
n = FLINT_MAX(t + 1, 2);
acb_hypgeom_airy_direct(ai, aip, bi, bip, z, n, wp);
}
else
{
/* estimate largest term: log2(exp(2(z^3/9)^(1/2))) */
term_est = 0.96179669392597560491 * z15;
/* estimate the smaller of Ai and Bi */
airy_est = estimate_airy(x, y, (ai != NULL || aip != NULL));
/* estimate absolute tolerance and necessary working precision */
abstol = airy_est - wp;
wp = wp + term_est - airy_est;
wp = FLINT_MAX(wp, 10);
t = 3 * (-abstol * LOG2) / (2 * z15 * EXP1);
t = (-abstol * LOG2) / (2 * d_lambertw(t));
n = FLINT_MAX(t + 1, 2);
if (acb_is_exact(z))
acb_hypgeom_airy_direct(ai, aip, bi, bip, z, n, wp);
else
acb_hypgeom_airy_direct_prop(ai, aip, bi, bip, z, n, wp);
}
}
if (ai != NULL) acb_set_round(ai, ai, prec);
if (aip != NULL) acb_set_round(aip, aip, prec);
if (bi != NULL) acb_set_round(bi, bi, prec);
if (bip != NULL) acb_set_round(bip, bip, prec);
}
void
acb_hypgeom_m(acb_t res, const acb_t a, const acb_t b, const acb_t z, int regularized, long prec)
{
long m = LONG_MAX;
long n = LONG_MAX;
if (acb_is_int(a) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(a)), 30) < 0)
{
m = arf_get_si(arb_midref(acb_realref(a)), ARF_RND_DOWN);
}
if (acb_is_int(b) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(b)), 30) < 0)
{
n = arf_get_si(arb_midref(acb_realref(b)), ARF_RND_DOWN);
}
/* terminating */
if (m <= 0 && m < n && m > -10 * prec && (n > 0 || !regularized))
{
acb_hypgeom_m_1f1(res, a, b, z, regularized, prec);
return;
}
/* large */
if (acb_hypgeom_u_use_asymp(z, prec))
{
acb_hypgeom_m_asymp(res, a, b, z, regularized, prec);
return;
}
/* remove singularity */
if (n <= 0 && n > -10 * prec && regularized)
{
acb_t c, d, t, u;
acb_init(c);
acb_init(d);
acb_init(t);
acb_init(u);
acb_sub(c, a, b, prec);
acb_add_ui(c, c, 1, prec);
acb_neg(d, b);
acb_add_ui(d, d, 2, prec);
acb_hypgeom_m_1f1(t, c, d, z, 0, prec);
acb_pow_ui(u, z, 1 - n, prec);
acb_mul(t, t, u, prec);
acb_rising_ui(u, a, 1 - n, prec);
acb_mul(t, t, u, prec);
arb_fac_ui(acb_realref(u), 1 - n, prec);
acb_div_arb(res, t, acb_realref(u), prec);
acb_clear(c);
acb_clear(d);
acb_clear(t);
acb_clear(u);
}
else
{
acb_hypgeom_m_1f1(res, a, b, z, regularized, prec);
}
}
void
acb_hypgeom_erf(acb_t res, const acb_t z, slong prec)
{
double x, y, abs_z2, log_z, log_erf_z_asymp;
slong prec2, wp;
int more_imaginary;
if (!acb_is_finite(z))
{
acb_indeterminate(res);
return;
}
if (acb_is_zero(z))
{
acb_zero(res);
return;
}
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), -64) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), -64) < 0))
{
acb_hypgeom_erf_1f1(res, z, prec, prec, 1);
return;
}
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 64) > 0 ||
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 64) > 0))
{
acb_hypgeom_erf_asymp(res, z, 0, prec, prec);
return;
}
x = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
y = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
abs_z2 = x * x + y * y;
log_z = 0.5 * log(abs_z2);
/* estimate of log(erf(z)), disregarding csgn term */
log_erf_z_asymp = y*y - x*x - log_z;
if (log_z - abs_z2 < -(prec + 8) * 0.69314718055994530942)
{
/* If the asymptotic term is small, we can
compute with reduced precision. */
prec2 = FLINT_MIN(prec + 4 + log_erf_z_asymp * 1.4426950408889634074, (double) prec);
prec2 = FLINT_MAX(8, prec2);
prec2 = FLINT_MIN(prec2, prec);
acb_hypgeom_erf_asymp(res, z, 0, prec, prec2);
}
else
{
more_imaginary = arf_cmpabs(arb_midref(acb_imagref(z)),
arb_midref(acb_realref(z))) > 0;
/* Worst case: exp(|x|^2), computed: exp(x^2).
(x^2+y^2) - (x^2-y^2) = 2y^2, etc. */
if (more_imaginary)
wp = prec + FLINT_MAX(2 * x * x, 0.0) * 1.4426950408889634074 + 5;
else
wp = prec + FLINT_MAX(2 * y * y, 0.0) * 1.4426950408889634074 + 5;
acb_hypgeom_erf_1f1(res, z, prec, wp, more_imaginary);
}
}
void
_arb_sin_cos_generic(arb_t s, arb_t c, const arf_t x, const mag_t xrad, slong prec)
{
int want_sin, want_cos;
slong maglim;
want_sin = (s != NULL);
want_cos = (c != NULL);
if (arf_is_zero(x) && mag_is_zero(xrad))
{
if (want_sin) arb_zero(s);
if (want_cos) arb_one(c);
return;
}
if (!arf_is_finite(x) || !mag_is_finite(xrad))
{
if (arf_is_nan(x))
{
if (want_sin) arb_indeterminate(s);
if (want_cos) arb_indeterminate(c);
}
else
{
if (want_sin) arb_zero_pm_one(s);
if (want_cos) arb_zero_pm_one(c);
}
return;
}
maglim = FLINT_MAX(65536, 4 * prec);
if (mag_cmp_2exp_si(xrad, -16) > 0 || arf_cmpabs_2exp_si(x, maglim) > 0)
{
_arb_sin_cos_wide(s, c, x, xrad, prec);
return;
}
if (arf_cmpabs_2exp_si(x, -(prec/2) - 2) <= 0)
{
mag_t t, u, v;
mag_init(t);
mag_init(u);
mag_init(v);
arf_get_mag(t, x);
mag_add(t, t, xrad);
mag_mul(u, t, t);
/* |sin(z)-z| <= z^3/6 */
if (want_sin)
{
arf_set(arb_midref(s), x);
mag_set(arb_radref(s), xrad);
arb_set_round(s, s, prec);
mag_mul(v, u, t);
mag_div_ui(v, v, 6);
arb_add_error_mag(s, v);
}
/* |cos(z)-1| <= z^2/2 */
if (want_cos)
{
arf_one(arb_midref(c));
mag_mul_2exp_si(arb_radref(c), u, -1);
}
mag_clear(t);
mag_clear(u);
mag_clear(v);
return;
}
if (mag_is_zero(xrad))
{
arb_sin_cos_arf_generic(s, c, x, prec);
}
else
{
mag_t t;
slong exp, radexp;
mag_init_set(t, xrad);
exp = arf_abs_bound_lt_2exp_si(x);
radexp = MAG_EXP(xrad);
if (radexp < MAG_MIN_LAGOM_EXP || radexp > MAG_MAX_LAGOM_EXP)
radexp = MAG_MIN_LAGOM_EXP;
if (want_cos && exp < -2)
prec = FLINT_MIN(prec, 20 - FLINT_MAX(exp, radexp) - radexp);
else
prec = FLINT_MIN(prec, 20 - radexp);
arb_sin_cos_arf_generic(s, c, x, prec);
/* todo: could use quadratic bound */
if (want_sin) mag_add(arb_radref(s), arb_radref(s), t);
if (want_cos) mag_add(arb_radref(c), arb_radref(c), t);
mag_clear(t);
}
}
void
_acb_hypgeom_m_1f1(acb_t res, const acb_t a, const acb_t b, const acb_t z,
int regularized, slong prec, slong gamma_prec, int kummer)
{
if (regularized)
{
/* Remove singularity */
if (acb_is_int(b) && arb_is_nonpositive(acb_realref(b)) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(b)), 30) < 0)
{
acb_t c, d, t, u;
slong n;
n = arf_get_si(arb_midref(acb_realref(b)), ARF_RND_DOWN);
acb_init(c);
acb_init(d);
acb_init(t);
acb_init(u);
acb_sub(c, a, b, prec);
acb_add_ui(c, c, 1, prec);
acb_neg(d, b);
acb_add_ui(d, d, 2, prec);
_acb_hypgeom_m_1f1(t, c, d, z, 0, prec, gamma_prec, kummer);
acb_pow_ui(u, z, 1 - n, prec);
acb_mul(t, t, u, prec);
acb_rising_ui(u, a, 1 - n, prec);
acb_mul(t, t, u, prec);
arb_fac_ui(acb_realref(u), 1 - n, prec);
acb_div_arb(res, t, acb_realref(u), prec);
acb_clear(c);
acb_clear(d);
acb_clear(t);
acb_clear(u);
}
else
{
acb_t t;
acb_init(t);
acb_rgamma(t, b, gamma_prec);
_acb_hypgeom_m_1f1(res, a, b, z, 0, prec, gamma_prec, kummer);
acb_mul(res, res, t, prec);
acb_clear(t);
}
return;
}
/* Kummer's transformation */
if (kummer)
{
acb_t u, v;
acb_init(u);
acb_init(v);
acb_sub(u, b, a, prec);
acb_neg(v, z);
_acb_hypgeom_m_1f1(u, u, b, v, regularized, prec, gamma_prec, 0);
acb_exp(v, z, prec);
acb_mul(res, u, v, prec);
acb_clear(u);
acb_clear(v);
return;
}
if (acb_is_one(a))
{
acb_hypgeom_pfq_direct(res, NULL, 0, b, 1, z, -1, prec);
}
else
{
acb_struct c[3];
c[0] = *a;
c[1] = *b;
acb_init(c + 2);
acb_one(c + 2);
acb_hypgeom_pfq_direct(res, c, 1, c + 1, 2, z, -1, prec);
acb_clear(c + 2);
}
}
void
acb_hypgeom_m_choose(int * asymp, int * kummer, slong * wp,
const acb_t a, const acb_t b, const acb_t z, int regularized, slong prec)
{
double x, y, t, cancellation;
double input_accuracy, direct_accuracy, asymp_accuracy;
slong m = WORD_MAX;
slong n = WORD_MAX;
if (acb_is_int(a) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(a)), 30) < 0)
{
m = arf_get_si(arb_midref(acb_realref(a)), ARF_RND_DOWN);
}
if (acb_is_int(b) &&
arf_cmpabs_2exp_si(arb_midref(acb_realref(b)), 30) < 0)
{
n = arf_get_si(arb_midref(acb_realref(b)), ARF_RND_DOWN);
}
*asymp = 0;
*kummer = 0;
*wp = prec;
/* The 1F1 series terminates. */
/* TODO: for large m, estimate extra precision here. */
if (m <= 0 && m < n && m > -10 * prec && (n > 0 || !regularized))
{
*asymp = 0;
return;
}
/* The 1F1 series terminates with the Kummer transform. */
/* TODO: for large m, estimate extra precision here. */
if (m >= 1 && n >= 1 && m < 0.1 * prec && n < 0.1 * prec && n <= m)
{
*asymp = 0;
*kummer = 1;
return;
}
input_accuracy = acb_rel_accuracy_bits(z);
t = acb_rel_accuracy_bits(a);
input_accuracy = FLINT_MIN(input_accuracy, t);
t = acb_rel_accuracy_bits(b);
input_accuracy = FLINT_MIN(input_accuracy, t);
input_accuracy = FLINT_MAX(input_accuracy, 0.0);
/* From here we ignore the values of a, b. Taking them into account is
a possible future improvement... */
/* Tiny |z|. */
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 2) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 2) < 0))
{
*asymp = 0;
*wp = FLINT_MAX(2, FLINT_MIN(input_accuracy + 20, prec));
return;
}
/* Huge |z|. */
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), 64) > 0 ||
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), 64) > 0))
{
*asymp = 1;
*wp = FLINT_MAX(2, FLINT_MIN(input_accuracy + 20, prec));
return;
}
x = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
y = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
asymp_accuracy = sqrt(x * x + y * y) * 1.44269504088896 - 5.0;
/* The Kummer transformation gives less cancellation with the 1F1 series. */
if (x < 0.0)
{
*kummer = 1;
x = -x;
}
if (asymp_accuracy >= prec)
{
*asymp = 1;
*wp = FLINT_MAX(2, FLINT_MIN(input_accuracy + 20, prec));
return;
}
cancellation = hypotmx(x, y) * 1.44269504088896;
direct_accuracy = input_accuracy - cancellation;
if (direct_accuracy > asymp_accuracy)
{
*asymp = 0;
*wp = FLINT_MAX(2, FLINT_MIN(input_accuracy + 20, prec + cancellation));
}
else
{
*asymp = 1;
*wp = FLINT_MAX(2, FLINT_MIN(input_accuracy + 20, prec));
}
}
static void
acb_log_sin_pi_half(acb_t res, const acb_t z, slong prec, int upper)
{
acb_t t, u, zmid;
arf_t n;
arb_t pi;
acb_init(t);
acb_init(u);
acb_init(zmid);
arf_init(n);
arb_init(pi);
arf_set(arb_midref(acb_realref(zmid)), arb_midref(acb_realref(z)));
arf_set(arb_midref(acb_imagref(zmid)), arb_midref(acb_imagref(z)));
arf_floor(n, arb_midref(acb_realref(zmid)));
arb_sub_arf(acb_realref(zmid), acb_realref(zmid), n, prec);
arb_const_pi(pi, prec);
if (arf_cmpabs_2exp_si(arb_midref(acb_imagref(zmid)), 2) < 1)
{
acb_sin_pi(t, zmid, prec);
acb_log(t, t, prec);
}
else /* i*pi*(z-0.5) + log((1-exp(-2i*pi*z))/2) */
{
acb_mul_2exp_si(t, zmid, 1);
acb_neg(t, t);
if (upper)
acb_conj(t, t);
acb_exp_pi_i(t, t, prec);
acb_sub_ui(t, t, 1, prec);
acb_neg(t, t);
acb_mul_2exp_si(t, t, -1);
acb_log(t, t, prec);
acb_one(u);
acb_mul_2exp_si(u, u, -1);
acb_sub(u, zmid, u, prec);
if (upper)
acb_conj(u, u);
acb_mul_onei(u, u);
acb_addmul_arb(t, u, pi, prec);
if (upper)
acb_conj(t, t);
}
if (upper)
arb_submul_arf(acb_imagref(t), pi, n, prec);
else
arb_addmul_arf(acb_imagref(t), pi, n, prec);
/* propagated error bound from the derivative pi cot(pi z) */
if (!acb_is_exact(z))
{
mag_t zm, um;
mag_init(zm);
mag_init(um);
acb_cot_pi(u, z, prec);
acb_mul_arb(u, u, pi, prec);
mag_hypot(zm, arb_radref(acb_realref(z)), arb_radref(acb_imagref(z)));
acb_get_mag(um, u);
mag_mul(um, um, zm);
acb_add_error_mag(t, um);
mag_clear(zm);
mag_clear(um);
}
acb_set(res, t);
acb_clear(t);
acb_clear(u);
acb_clear(zmid);
arf_clear(n);
arb_clear(pi);
}
void
acb_hypgeom_legendre_q(acb_t res, const acb_t n, const acb_t m,
const acb_t z, int type, slong prec)
{
if (type == 0)
{
/* http://functions.wolfram.com/07.11.26.0033.01 */
/* todo: simplify the gamma quotients and the sqrt pi factor... */
acb_t a, b, c, z2, mn, nm, t, u;
acb_init(a);
acb_init(b);
acb_init(c);
acb_init(z2);
acb_init(mn);
acb_init(nm);
acb_init(t);
acb_init(u);
acb_add(mn, m, n, prec); /* mn = m + n */
acb_sub(nm, n, m, prec); /* nm = n - m */
acb_mul(z2, z, z, prec); /* z2 = z^2 */
/* t = 2F1((1-m-n)/2, (n-m)/2+1, 3/2, z^2) */
acb_sub_ui(a, mn, 1, prec);
acb_neg(a, a);
acb_mul_2exp_si(a, a, -1);
acb_mul_2exp_si(b, nm, -1);
acb_add_ui(b, b, 1, prec);
acb_set_ui(c, 3);
acb_mul_2exp_si(c, c, -1);
acb_hypgeom_2f1(t, a, b, c, z2, 0, prec);
/* u = 2F1(-(m+n)/2, (n-m+1)/2, 1/2, z^2) */
acb_neg(a, mn);
acb_mul_2exp_si(a, a, -1);
acb_add_ui(b, nm, 1, prec);
acb_mul_2exp_si(b, b, -1);
acb_one(c);
acb_mul_2exp_si(c, c, -1);
acb_hypgeom_2f1(u, a, b, c, z2, 0, prec);
/* a = cospi((m+n)/2) gamma((m+n)/2+1) rgamma((n-m+1)/2) z */
/* b = sinpi((m+n)/2) gamma((m+n+1)/2) rgamma((n-m)/2+1) / 2 */
acb_mul_2exp_si(a, mn, -1);
acb_sin_cos_pi(b, a, a, prec);
acb_mul_2exp_si(c, mn, -1);
acb_add_ui(c, c, 1, prec);
acb_gamma(c, c, prec);
acb_mul(a, a, c, prec);
acb_add_ui(c, nm, 1, prec);
acb_mul_2exp_si(c, c, -1);
acb_rgamma(c, c, prec);
acb_mul(a, a, c, prec);
acb_mul(a, a, z, prec);
acb_add_ui(c, mn, 1, prec);
acb_mul_2exp_si(c, c, -1);
acb_gamma(c, c, prec);
acb_mul(b, b, c, prec);
acb_mul_2exp_si(c, nm, -1);
acb_add_ui(c, c, 1, prec);
acb_rgamma(c, c, prec);
acb_mul(b, b, c, prec);
acb_mul_2exp_si(b, b, -1);
/* at - bu */
acb_mul(t, t, a, prec);
acb_mul(u, u, b, prec);
acb_sub(t, t, u, prec);
/* prefactor sqrt(pi) 2^m (1-z^2)^(-m/2) */
if (!acb_is_zero(m))
{
acb_sub_ui(u, z2, 1, prec);
acb_neg(u, u);
acb_neg(c, m);
acb_mul_2exp_si(c, c, -1);
acb_pow(u, u, c, prec);
acb_set_ui(c, 2);
acb_pow(c, c, m, prec);
acb_mul(u, u, c, prec);
acb_mul(t, t, u, prec);
}
arb_const_sqrt_pi(acb_realref(u), prec);
acb_mul_arb(t, t, acb_realref(u), prec);
acb_set(res, t);
acb_clear(a);
acb_clear(b);
acb_clear(c);
acb_clear(z2);
acb_clear(mn);
acb_clear(nm);
acb_clear(t);
acb_clear(u);
}
else if (type == 1)
{
if ((arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), -2) < 0 &&
arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), -2) < 0) ||
!_acb_hypgeom_legendre_q_single_valid(z))
{
_acb_hypgeom_legendre_q_double(res, n, m, z, prec);
}
else
{
_acb_hypgeom_legendre_q_single(res, n, m, z, prec);
}
}
else
{
flint_printf("unsupported 'type' %d for legendre q\n", type);
abort();
}
}
void
_acb_lambertw(acb_t res, const acb_t z, const acb_t ez1, const fmpz_t k, int flags, slong prec)
{
slong goal, ebits, ebits2, ls, lt;
const fmpz * expo;
/* Estimated accuracy goal. */
/* todo: account for exponent bits and bits in k. */
goal = acb_rel_accuracy_bits(z);
goal = FLINT_MAX(goal, 10);
goal = FLINT_MIN(goal, prec);
/* Handle tiny z directly. For k >= 2, |c_k| <= 4^k / 16. */
if (fmpz_is_zero(k)
&& arf_cmpabs_2exp_si(arb_midref(acb_realref(z)), -goal / 2) < 0
&& arf_cmpabs_2exp_si(arb_midref(acb_imagref(z)), -goal / 2) < 0)
{
mag_t err;
mag_init(err);
acb_get_mag(err, z);
mag_mul_2exp_si(err, err, 2);
acb_set(res, z);
acb_submul(res, res, res, prec);
mag_geom_series(err, err, 3);
mag_mul_2exp_si(err, err, -4);
acb_add_error_mag(res, err);
mag_clear(err);
return;
}
if (arf_cmpabs(arb_midref(acb_realref(z)), arb_midref(acb_imagref(z))) >= 0)
expo = ARF_EXPREF(arb_midref(acb_realref(z)));
else
expo = ARF_EXPREF(arb_midref(acb_imagref(z)));
ebits = fmpz_bits(expo);
/* ebits ~= log2(|log(z) + 2 pi i k|) */
/* ebits2 ~= log2(log(log(z))) */
ebits = FLINT_MAX(ebits, fmpz_bits(k));
ebits = FLINT_MAX(ebits, 1) - 1;
ebits2 = FLINT_BIT_COUNT(ebits);
ebits2 = FLINT_MAX(ebits2, 1) - 1;
/* We gain accuracy from the exponent when W ~ log - log log */
if (fmpz_sgn(expo) > 0 || (fmpz_sgn(expo) < 0 && !fmpz_is_zero(k)))
{
goal += ebits - ebits2;
goal = FLINT_MAX(goal, 10);
goal = FLINT_MIN(goal, prec);
/* The asymptotic series with truncation L, M gives us about
t - max(2+lt+L*(2+ls), M*(2+lt)) bits of accuracy where
ls = -ebits, lt = ebits2 - ebits. */
ls = 2 - ebits;
lt = 2 + ebits2 - ebits;
if (ebits - FLINT_MAX(lt + 1*ls, 1*lt) > goal)
{
acb_lambertw_asymp(res, z, k, 1, 1, goal);
acb_set_round(res, res, prec);
return;
}
else if (ebits - FLINT_MAX(lt + 3*ls, 5*lt) > goal)
{
acb_lambertw_asymp(res, z, k, 3, 5, goal);
acb_set_round(res, res, prec);
return;
}
}
/* Extremely close to the branch point at -1/e, use the series expansion directly. */
if (acb_lambertw_try_near_branch_point(res, z, ez1, k, flags, goal))
{
acb_set_round(res, res, prec);
return;
}
/* compute union of both sides */
if (acb_lambertw_branch_crossing(z, ez1, k))
{
acb_t za, zb, eza1, ezb1;
fmpz_t kk;
acb_init(za);
acb_init(zb);
acb_init(eza1);
acb_init(ezb1);
fmpz_init(kk);
fmpz_neg(kk, k);
acb_set(za, z);
acb_conj(zb, z);
arb_nonnegative_part(acb_imagref(za), acb_imagref(za));
arb_nonnegative_part(acb_imagref(zb), acb_imagref(zb));
acb_set(eza1, ez1);
acb_conj(ezb1, ez1);
arb_nonnegative_part(acb_imagref(eza1), acb_imagref(eza1));
arb_nonnegative_part(acb_imagref(ezb1), acb_imagref(ezb1));
/* Check series expansion again, because now there is no crossing. */
if (!acb_lambertw_try_near_branch_point(res, za, eza1, k, flags, goal))
acb_lambertw_cleared_cut_fix_small(za, za, eza1, k, flags, goal);
if (!acb_lambertw_try_near_branch_point(res, zb, ezb1, kk, flags, goal))
acb_lambertw_cleared_cut_fix_small(zb, zb, ezb1, kk, flags, goal);
acb_conj(zb, zb);
acb_union(res, za, zb, prec);
acb_clear(za);
acb_clear(zb);
acb_clear(eza1);
acb_clear(ezb1);
fmpz_clear(kk);
}
else
{
acb_lambertw_cleared_cut_fix_small(res, z, ez1, k, flags, goal);
acb_set_round(res, res, prec);
}
}