void
acb_polygamma(acb_t res, const acb_t s, const acb_t z, long prec)
{
if (acb_is_zero(s))
{
acb_digamma(res, z, prec);
}
else if (acb_is_int(s) && arb_is_positive(acb_realref(s)))
{
acb_t t, u;
acb_init(t);
acb_init(u);
acb_add_ui(t, s, 1, prec);
acb_gamma(u, t, prec);
acb_hurwitz_zeta(t, t, z, prec);
if (arf_is_int_2exp_si(arb_midref(acb_realref(s)), 1))
acb_neg(t, t);
acb_mul(res, t, u, prec);
acb_clear(t);
acb_clear(u);
}
else
{
acb_t t, u;
acb_struct v[2];
acb_init(t);
acb_init(u);
acb_init(v);
acb_init(v + 1);
/* u = psi(-s) + gamma */
acb_neg(t, s);
acb_digamma(u, t, prec);
arb_const_euler(acb_realref(v), prec);
arb_add(acb_realref(u), acb_realref(u), acb_realref(v), prec);
acb_add_ui(t, s, 1, prec);
_acb_poly_zeta_cpx_series(v, t, z, 0, 2, prec);
acb_addmul(v + 1, v, u, prec);
acb_neg(t, s);
acb_rgamma(u, t, prec);
acb_mul(res, v + 1, u, prec);
acb_clear(v);
acb_clear(v + 1);
acb_clear(t);
acb_clear(u);
}
}
void
_acb_poly_zeta_cpx_series(acb_ptr z, const acb_t s, const acb_t a, int deflate, slong d, slong prec)
{
ulong M, N;
slong i, bound_prec;
mag_t bound;
arb_ptr vb;
int is_real, const_is_real;
if (d < 1)
return;
if (!acb_is_finite(s) || !acb_is_finite(a))
{
_acb_vec_indeterminate(z, d);
return;
}
if (acb_is_one(s) && deflate && d == 1)
{
acb_digamma(z, a, prec);
acb_neg(z, z);
if (!acb_is_finite(z)) /* todo: in digamma */
acb_indeterminate(z);
return;
}
is_real = const_is_real = 0;
if (acb_is_real(s) && acb_is_real(a))
{
if (arb_is_positive(acb_realref(a)))
{
is_real = const_is_real = 1;
}
else if (arb_is_int(acb_realref(a)) &&
arb_is_int(acb_realref(s)) &&
arb_is_nonpositive(acb_realref(s)))
{
const_is_real = 1;
}
}
mag_init(bound);
vb = _arb_vec_init(d);
bound_prec = 40 + prec / 20;
_acb_poly_zeta_em_choose_param(bound, &N, &M, s, a, FLINT_MIN(d, 2), prec, bound_prec);
_acb_poly_zeta_em_bound(vb, s, a, N, M, d, bound_prec);
_acb_poly_zeta_em_sum(z, s, a, deflate, N, M, d, prec);
for (i = 0; i < d; i++)
{
arb_get_mag(bound, vb + i);
arb_add_error_mag(acb_realref(z + i), bound);
if (!is_real && !(i == 0 && const_is_real))
arb_add_error_mag(acb_imagref(z + i), bound);
}
mag_clear(bound);
_arb_vec_clear(vb, d);
}
void
_acb_poly_digamma_series(acb_ptr res, acb_srcptr h, slong hlen, slong len, slong prec)
{
int reflect;
slong i, r, n, rflen, wp;
acb_t zr;
acb_ptr t, u, v;
hlen = FLINT_MIN(hlen, len);
if (hlen == 1)
{
acb_digamma(res, h, prec);
if (acb_is_finite(res))
_acb_vec_zero(res + 1, len - 1);
else
_acb_vec_indeterminate(res + 1, len - 1);
return;
}
/* use real code for real input */
if (_acb_vec_is_real(h, hlen))
{
arb_ptr tmp = _arb_vec_init(len);
for (i = 0; i < hlen; i++)
arb_set(tmp + i, acb_realref(h + i));
_arb_poly_digamma_series(tmp, tmp, hlen, len, prec);
for (i = 0; i < len; i++)
acb_set_arb(res + i, tmp + i);
_arb_vec_clear(tmp, len);
return;
}
wp = prec + FLINT_BIT_COUNT(prec);
t = _acb_vec_init(len + 1);
u = _acb_vec_init(len + 1);
v = _acb_vec_init(len + 1);
acb_init(zr);
/* use Stirling series */
acb_gamma_stirling_choose_param(&reflect, &r, &n, h, 1, 1, wp);
/* psi(x) = psi((1-x)+r) - h(1-x,r) - pi*cot(pi*x) */
if (reflect)
{
if (r != 0) /* otherwise t = 0 */
{
acb_sub_ui(v, h, 1, wp);
acb_neg(v, v);
acb_one(v + 1);
rflen = FLINT_MIN(len + 1, r + 1);
_acb_poly_rising_ui_series(u, v, 2, r, rflen, wp);
_acb_poly_derivative(v, u, rflen, wp);
_acb_poly_div_series(t, v, rflen - 1, u, rflen, len, wp);
for (i = 1; i < len; i += 2)
acb_neg(t + i, t + i);
}
acb_sub_ui(zr, h, r + 1, wp);
acb_neg(zr, zr);
_acb_poly_gamma_stirling_eval2(u, zr, n, len + 1, 1, wp);
for (i = 1; i < len; i += 2)
acb_neg(u + i, u + i);
_acb_vec_sub(u, u, t, len, wp);
acb_set(t, h);
acb_one(t + 1);
_acb_poly_cot_pi_series(t, t, 2, len, wp);
acb_const_pi(v, wp);
_acb_vec_scalar_mul(t, t, len, v, wp);
_acb_vec_sub(u, u, t, len, wp);
}
else
{
if (r == 0)
{
acb_add_ui(zr, h, r, wp);
_acb_poly_gamma_stirling_eval2(u, zr, n, len + 1, 1, wp);
}
else
{
acb_set(v, h);
acb_one(v + 1);
rflen = FLINT_MIN(len + 1, r + 1);
_acb_poly_rising_ui_series(u, v, 2, r, rflen, wp);
_acb_poly_derivative(v, u, rflen, wp);
_acb_poly_div_series(t, v, rflen - 1, u, rflen, len, wp);
acb_add_ui(zr, h, r, wp);
_acb_poly_gamma_stirling_eval2(u, zr, n, len + 1, 1, wp);
_acb_vec_sub(u, u, t, len, wp);
}
}
/* compose with nonconstant part */
acb_zero(t);
_acb_vec_set(t + 1, h + 1, hlen - 1);
_acb_poly_compose_series(res, u, len, t, hlen, len, prec);
acb_clear(zr);
_acb_vec_clear(t, len + 1);
_acb_vec_clear(u, len + 1);
_acb_vec_clear(v, len + 1);
}
void
_acb_poly_lgamma_series(acb_ptr res, acb_srcptr h, slong hlen, slong len, slong prec)
{
int reflect;
slong i, r, n, wp;
acb_t zr;
acb_ptr t, u;
hlen = FLINT_MIN(hlen, len);
if (hlen == 1)
{
acb_lgamma(res, h, prec);
if (acb_is_finite(res))
_acb_vec_zero(res + 1, len - 1);
else
_acb_vec_indeterminate(res + 1, len - 1);
return;
}
if (len == 2)
{
acb_t v;
acb_init(v);
acb_set(v, h + 1);
acb_digamma(res + 1, h, prec);
acb_lgamma(res, h, prec);
acb_mul(res + 1, res + 1, v, prec);
acb_clear(v);
return;
}
/* use real code for real input and output */
if (_acb_vec_is_real(h, hlen) && arb_is_positive(acb_realref(h)))
{
arb_ptr tmp = _arb_vec_init(len);
for (i = 0; i < hlen; i++)
arb_set(tmp + i, acb_realref(h + i));
_arb_poly_lgamma_series(tmp, tmp, hlen, len, prec);
for (i = 0; i < len; i++)
acb_set_arb(res + i, tmp + i);
_arb_vec_clear(tmp, len);
return;
}
wp = prec + FLINT_BIT_COUNT(prec);
t = _acb_vec_init(len);
u = _acb_vec_init(len);
acb_init(zr);
/* use Stirling series */
acb_gamma_stirling_choose_param(&reflect, &r, &n, h, 1, 0, wp);
if (reflect)
{
/* log gamma(h+x) = log rf(1-(h+x), r) - log gamma(1-(h+x)+r) - log sin(pi (h+x)) + log(pi) */
if (r != 0) /* otherwise t = 0 */
{
acb_sub_ui(u, h, 1, wp);
acb_neg(u, u);
_log_rising_ui_series(t, u, r, len, wp);
for (i = 1; i < len; i += 2)
acb_neg(t + i, t + i);
}
acb_sub_ui(u, h, 1, wp);
acb_neg(u, u);
acb_add_ui(zr, u, r, wp);
_acb_poly_gamma_stirling_eval(u, zr, n, len, wp);
for (i = 1; i < len; i += 2)
acb_neg(u + i, u + i);
_acb_vec_sub(t, t, u, len, wp);
/* log(sin) is unstable with large imaginary parts;
cot_pi is implemented in a numerically stable way */
acb_set(u, h);
acb_one(u + 1);
_acb_poly_cot_pi_series(u, u, 2, len - 1, wp);
_acb_poly_integral(u, u, len, wp);
acb_const_pi(u, wp);
_acb_vec_scalar_mul(u + 1, u + 1, len - 1, u, wp);
acb_log_sin_pi(u, h, wp);
_acb_vec_sub(u, t, u, len, wp);
acb_const_pi(t, wp); /* todo: constant for log pi */
acb_log(t, t, wp);
acb_add(u, u, t, wp);
}
else
{
/* log gamma(x) = log gamma(x+r) - log rf(x,r) */
acb_add_ui(zr, h, r, wp);
_acb_poly_gamma_stirling_eval(u, zr, n, len, wp);
if (r != 0)
{
_log_rising_ui_series(t, h, r, len, wp);
_acb_vec_sub(u, u, t, len, wp);
}
}
/* compose with nonconstant part */
acb_zero(t);
_acb_vec_set(t + 1, h + 1, hlen - 1);
_acb_poly_compose_series(res, u, len, t, hlen, len, prec);
acb_clear(zr);
_acb_vec_clear(t, len);
_acb_vec_clear(u, len);
}
int main()
{
slong iter;
flint_rand_t state;
flint_printf("digamma....");
fflush(stdout);
flint_randinit(state);
for (iter = 0; iter < 3000 * arb_test_multiplier(); iter++)
{
acb_t a, b, c;
slong prec1, prec2;
prec1 = 2 + n_randint(state, 1000);
prec2 = prec1 + 30;
acb_init(a);
acb_init(b);
acb_init(c);
arb_randtest_precise(acb_realref(a), state, 1 + n_randint(state, 1000), 3);
arb_randtest_precise(acb_imagref(a), state, 1 + n_randint(state, 1000), 3);
acb_digamma(b, a, prec1);
acb_digamma(c, a, prec2);
if (!acb_overlaps(b, c))
{
flint_printf("FAIL: overlap\n\n");
flint_printf("a = "); acb_print(a); flint_printf("\n\n");
flint_printf("b = "); acb_print(b); flint_printf("\n\n");
flint_printf("c = "); acb_print(c); flint_printf("\n\n");
abort();
}
acb_set(c, a);
acb_digamma(c, c, prec2);
if (!acb_overlaps(b, c))
{
flint_printf("FAIL: aliasing\n\n");
flint_printf("a = "); acb_print(a); flint_printf("\n\n");
flint_printf("b = "); acb_print(b); flint_printf("\n\n");
flint_printf("c = "); acb_print(c); flint_printf("\n\n");
abort();
}
/* check digamma(z+1) = digamma(z) + 1/z */
acb_inv(c, a, prec1);
acb_add(b, b, c, prec1);
acb_add_ui(c, a, 1, prec1);
acb_digamma(c, c, prec1);
if (!acb_overlaps(b, c))
{
flint_printf("FAIL: functional equation\n\n");
flint_printf("a = "); acb_print(a); flint_printf("\n\n");
flint_printf("b = "); acb_print(b); flint_printf("\n\n");
flint_printf("c = "); acb_print(c); flint_printf("\n\n");
abort();
}
acb_clear(a);
acb_clear(b);
acb_clear(c);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
