int main()
{
slong iter;
flint_rand_t state;
flint_printf("lgamma....");
fflush(stdout);
flint_randinit(state);
for (iter = 0; iter < 3000 * arb_test_multiplier(); iter++)
{
arb_t a, b, c;
slong prec1, prec2;
prec1 = 2 + n_randint(state, 1000);
prec2 = prec1 + 30;
arb_init(a);
arb_init(b);
arb_init(c);
arb_randtest_precise(a, state, 1 + n_randint(state, 1000), 3);
arb_lgamma(b, a, prec1);
arb_lgamma(c, a, prec2);
if (!arb_overlaps(b, c))
{
flint_printf("FAIL: overlap\n\n");
flint_printf("a = "); arb_print(a); flint_printf("\n\n");
flint_printf("b = "); arb_print(b); flint_printf("\n\n");
flint_printf("c = "); arb_print(c); flint_printf("\n\n");
abort();
}
arb_lgamma(a, a, prec2);
if (!arb_equal(a, c))
{
flint_printf("FAIL: aliasing\n\n");
abort();
}
arb_clear(a);
arb_clear(b);
arb_clear(c);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
void
_arb_poly_lgamma_series(arb_ptr res, arb_srcptr h, slong hlen, slong len, slong prec)
{
int reflect;
slong r, n, wp;
arb_t zr;
arb_ptr t, u;
if (!arb_is_positive(h))
{
_arb_vec_indeterminate(res, len);
return;
}
hlen = FLINT_MIN(hlen, len);
wp = prec + FLINT_BIT_COUNT(prec);
t = _arb_vec_init(len);
u = _arb_vec_init(len);
arb_init(zr);
/* use zeta values at small integers */
if (arb_is_int(h) && (arf_cmpabs_ui(arb_midref(h), prec / 2) < 0))
{
r = arf_get_si(arb_midref(h), ARF_RND_DOWN);
if (r <= 0)
{
_arb_vec_indeterminate(res, len);
goto cleanup;
}
else
{
_arb_poly_lgamma_series_at_one(u, len, wp);
if (r != 1)
{
arb_one(zr);
_log_rising_ui_series(t, zr, r - 1, len, wp);
_arb_vec_add(u, u, t, len, wp);
}
}
}
else if (len <= 2)
{
arb_lgamma(u, h, wp);
if (len == 2)
arb_digamma(u + 1, h, wp);
}
else
{
/* otherwise use Stirling series */
arb_gamma_stirling_choose_param(&reflect, &r, &n, h, 0, 0, wp);
arb_add_ui(zr, h, r, wp);
_arb_poly_gamma_stirling_eval(u, zr, n, len, wp);
if (r != 0)
{
_log_rising_ui_series(t, h, r, len, wp);
_arb_vec_sub(u, u, t, len, wp);
}
}
/* compose with nonconstant part */
arb_zero(t);
_arb_vec_set(t + 1, h + 1, hlen - 1);
_arb_poly_compose_series(res, u, len, t, hlen, len, prec);
cleanup:
arb_clear(zr);
_arb_vec_clear(t, len);
_arb_vec_clear(u, len);
}
