void acb_lambertw_left(acb_t res, const acb_t z, const fmpz_t k, slong prec) { if (acb_contains_zero(z) && !(fmpz_equal_si(k, -1) && acb_is_real(z))) { acb_indeterminate(res); return; } if (arb_is_positive(acb_imagref(z))) { acb_lambertw(res, z, k, 0, prec); } else if (arb_is_nonpositive(acb_imagref(z))) { fmpz_t kk; fmpz_init(kk); fmpz_add_ui(kk, k, 1); fmpz_neg(kk, kk); acb_conj(res, z); acb_lambertw(res, res, kk, 0, prec); acb_conj(res, res); fmpz_clear(kk); } else { acb_t za, zb; fmpz_t kk; acb_init(za); acb_init(zb); fmpz_init(kk); 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)); fmpz_add_ui(kk, k, 1); fmpz_neg(kk, kk); acb_lambertw(za, za, k, 0, prec); acb_lambertw(zb, zb, kk, 0, prec); acb_conj(zb, zb); acb_union(res, za, zb, prec); acb_clear(za); acb_clear(zb); fmpz_clear(kk); } }
void acb_lambertw_cleared_cut_fix_small(acb_t res, const acb_t z, const acb_t ez1, const fmpz_t k, int flags, slong prec) { acb_t zz, zmid, zmide1; arf_t eps; acb_init(zz); acb_init(zmid); acb_init(zmide1); arf_init(eps); arf_mul_2exp_si(eps, arb_midref(acb_realref(z)), -prec); acb_set(zz, z); if (arf_sgn(arb_midref(acb_realref(zz))) < 0 && (!fmpz_is_zero(k) || arf_sgn(arb_midref(acb_realref(ez1))) < 0) && arf_cmpabs(arb_midref(acb_imagref(zz)), eps) < 0) { /* now the value must be in [0,2eps] */ arf_get_mag(arb_radref(acb_imagref(zz)), eps); arf_set_mag(arb_midref(acb_imagref(zz)), arb_radref(acb_imagref(zz))); if (arf_sgn(arb_midref(acb_imagref(z))) >= 0) { acb_lambertw_cleared_cut(res, zz, k, flags, prec); } else { fmpz_t kk; fmpz_init(kk); fmpz_neg(kk, k); acb_lambertw_cleared_cut(res, zz, kk, flags, prec); acb_conj(res, res); fmpz_clear(kk); } } else { acb_lambertw_cleared_cut(res, zz, k, flags, prec); } acb_clear(zz); acb_clear(zmid); acb_clear(zmide1); arf_clear(eps); }
void acb_dirichlet_zeta_rs_mid(acb_t res, const acb_t s, slong K, slong prec) { acb_t R1, R2, X, t; slong wp; if (arf_sgn(arb_midref(acb_imagref(s))) < 0) { acb_init(t); acb_conj(t, s); acb_dirichlet_zeta_rs(res, t, K, prec); acb_conj(res, res); acb_clear(t); return; } acb_init(R1); acb_init(R2); acb_init(X); acb_init(t); /* rs_r increases the precision internally */ wp = prec; acb_dirichlet_zeta_rs_r(R1, s, K, wp); if (arb_is_exact(acb_realref(s)) && (arf_cmp_2exp_si(arb_midref(acb_realref(s)), -1) == 0)) { acb_conj(R2, R1); } else { /* conj(R(conj(1-s))) */ arb_sub_ui(acb_realref(t), acb_realref(s), 1, 10 * wp); arb_neg(acb_realref(t), acb_realref(t)); arb_set(acb_imagref(t), acb_imagref(s)); acb_dirichlet_zeta_rs_r(R2, t, K, wp); acb_conj(R2, R2); } if (acb_is_finite(R1) && acb_is_finite(R2)) { wp += 10 + arf_abs_bound_lt_2exp_si(arb_midref(acb_imagref(s))); wp = FLINT_MAX(wp, 10); /* X = pi^(s-1/2) gamma((1-s)/2) rgamma(s/2) = (2 pi)^s rgamma(s) / (2 cos(pi s / 2)) */ acb_rgamma(X, s, wp); acb_const_pi(t, wp); acb_mul_2exp_si(t, t, 1); acb_pow(t, t, s, wp); acb_mul(X, X, t, wp); acb_mul_2exp_si(t, s, -1); acb_cos_pi(t, t, wp); acb_mul_2exp_si(t, t, 1); acb_div(X, X, t, wp); acb_mul(R2, R2, X, wp); } /* R1 + X * R2 */ acb_add(res, R1, R2, prec); acb_clear(R1); acb_clear(R2); acb_clear(X); acb_clear(t); }
void acb_dirichlet_l(acb_t res, const acb_t s, const dirichlet_group_t G, const dirichlet_char_t chi, slong prec) { if (!acb_is_finite(s)) { acb_indeterminate(res); } else if (G == NULL || G->q == 1) { acb_dirichlet_zeta(res, s, prec); } else if (dirichlet_char_is_primitive(G, chi) && (arf_cmp_d(arb_midref(acb_realref(s)), -0.5) < 0 || (G->q != 1 && dirichlet_parity_char(G, chi) == 0 && arf_cmpabs_d(arb_midref(acb_imagref(s)), 0.125) < 0 && arf_cmp_d(arb_midref(acb_realref(s)), 0.125) < 0))) { /* use functional equation */ acb_t t, u, v; int parity; ulong q; parity = dirichlet_parity_char(G, chi); q = G->q; acb_init(t); acb_init(u); acb_init(v); /* gamma((1-s+p)/2) / gamma((s+p)/2) */ acb_add_ui(t, s, parity, prec); acb_mul_2exp_si(t, t, -1); acb_rgamma(t, t, prec); if (!acb_is_zero(t)) /* assumes q != 1 when s = 0 */ { acb_neg(u, s); acb_add_ui(u, u, 1 + parity, prec); acb_mul_2exp_si(u, u, -1); acb_gamma(u, u, prec); acb_mul(t, t, u, prec); /* epsilon */ acb_dirichlet_root_number(u, G, chi, prec); acb_mul(t, t, u, prec); /* (pi/q)^(s-1/2) */ acb_const_pi(u, prec); acb_div_ui(u, u, q, prec); acb_set_d(v, -0.5); acb_add(v, v, s, prec); acb_pow(u, u, v, prec); acb_mul(t, t, u, prec); acb_sub_ui(u, s, 1, prec); acb_neg(u, u); acb_conj(u, u); acb_dirichlet_l_general(u, u, G, chi, prec); acb_conj(u, u); acb_mul(t, t, u, prec); if (dirichlet_char_is_real(G, chi) && acb_is_real(s)) arb_zero(acb_imagref(t)); } acb_set(res, t); acb_clear(t); acb_clear(u); acb_clear(v); } else { acb_dirichlet_l_general(res, s, G, chi, prec); } }
void acb_lambertw_middle(acb_t res, const acb_t z, slong prec) { fmpz_t k; if (acb_contains_zero(z)) { acb_indeterminate(res); return; } fmpz_init(k); fmpz_set_si(k, -1); if (arb_is_positive(acb_imagref(z))) { acb_lambertw(res, z, k, 0, prec); } else if (arb_is_negative(acb_imagref(z))) { acb_conj(res, z); acb_lambertw(res, res, k, 0, prec); acb_conj(res, res); } else if (arb_is_negative(acb_realref(z))) { if (arb_is_nonnegative(acb_imagref(z))) { acb_lambertw(res, z, k, 0, prec); } else if (arb_is_negative(acb_imagref(z))) { acb_conj(res, z); acb_lambertw(res, res, k, 0, prec); acb_conj(res, res); } else { acb_t za, zb; acb_init(za); acb_init(zb); 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_lambertw(za, za, k, 0, prec); acb_lambertw(zb, zb, k, 0, prec); acb_conj(zb, zb); acb_union(res, za, zb, prec); acb_clear(za); acb_clear(zb); } } else /* re is positive */ { if (arb_is_positive(acb_imagref(z))) { acb_lambertw(res, z, k, 0, prec); } else if (arb_is_nonpositive(acb_imagref(z))) { acb_conj(res, z); acb_lambertw(res, res, k, 0, prec); acb_conj(res, res); } else { acb_t za, zb; acb_init(za); acb_init(zb); 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_lambertw(za, za, k, 0, prec); acb_lambertw(zb, zb, k, 0, prec); acb_conj(zb, zb); acb_union(res, za, zb, prec); acb_clear(za); acb_clear(zb); } } fmpz_clear(k); }
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); } }
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); }