static void
_interpolate_newton(arb_ptr ys, arb_srcptr xs, long n, long prec)
{
arb_t p, q, t;
long i, j;
arb_init(p);
arb_init(q);
arb_init(t);
for (i = 1; i < n; i++)
{
arb_set(t, ys + i - 1);
for (j = i; j < n; j++)
{
arb_sub(p, ys + j, t, prec);
arb_sub(q, xs + j, xs + j - i, prec);
arb_set(t, ys + j);
arb_div(ys + j, p, q, prec);
}
}
arb_clear(p);
arb_clear(q);
arb_clear(t);
}
int acb_cmp_pretty(const acb_t a, const acb_t b)
{
arb_t t, u, v;
int res;
arb_init(t);
arb_init(u);
arb_init(v);
arb_abs(u, acb_imagref(a));
arb_abs(v, acb_imagref(b));
arb_sub(t, u, v, MAG_BITS);
res = 0;
if (arb_contains_zero(t))
{
arb_sub(t, acb_realref(a), acb_realref(b), MAG_BITS);
res = arb_is_positive(t) ? 1 : -1;
}
else
{
res = arb_is_positive(t) ? 1 : -1;
}
arb_clear(t);
arb_clear(u);
arb_clear(v);
return res;
}
static void
_newton_to_monomial(arb_ptr ys, arb_srcptr xs, long n, long prec)
{
arb_t t, u;
long i, j;
arb_init(t);
arb_init(u);
for (i = n - 2; i >= 0; i--)
{
arb_set(t, ys + i);
arb_set(ys + i, ys + i + 1);
for (j = i + 1; j < n - 1; j++)
{
arb_mul(u, ys + j, xs + i, prec);
arb_sub(ys + j, ys + j + 1, u, prec);
}
arb_mul(u, ys + n - 1, xs + i, prec);
arb_sub(ys + n - 1, t, u, prec);
}
_arb_poly_reverse(ys, ys, n, n);
arb_clear(t);
arb_clear(u);
}
void
acb_real_min(acb_t res, const acb_t x, const acb_t y, int analytic, slong prec)
{
arb_t t;
if (!acb_is_finite(x) || !acb_is_finite(y))
{
acb_indeterminate(res);
return;
}
arb_init(t);
arb_sub(t, acb_realref(x), acb_realref(y), prec);
if (arb_is_positive(t))
acb_set_round(res, y, prec);
else if (arb_is_negative(t))
acb_set_round(res, x, prec);
else if (!analytic)
acb_union(res, x, y, prec);
else
acb_indeterminate(res);
arb_clear(t);
}
static void
arb_sqrt1pm1_tiny(arb_t r, const arb_t z, slong prec)
{
mag_t b, c;
arb_t t;
mag_init(b);
mag_init(c);
arb_init(t);
/* if |z| < 1, then |(sqrt(1+z)-1) - (z/2-z^2/8)| <= |z|^3/(1-|z|)/16 */
arb_get_mag(b, z);
mag_one(c);
mag_sub_lower(c, c, b);
mag_pow_ui(b, b, 3);
mag_div(b, b, c);
mag_mul_2exp_si(b, b, -4);
arb_mul(t, z, z, prec);
arb_mul_2exp_si(t, t, -2);
arb_sub(r, z, t, prec);
arb_mul_2exp_si(r, r, -1);
if (mag_is_finite(b))
arb_add_error_mag(r, b);
else
arb_indeterminate(r);
mag_clear(b);
mag_clear(c);
arb_clear(t);
}
void
arb_submul_naive(arb_t z, const arb_t x, const arb_t y, slong prec)
{
arb_t t;
arb_init(t);
arb_mul(t, x, y, ARF_PREC_EXACT);
arb_sub(z, z, t, prec);
arb_clear(t);
}
void arb_twobytwo_diag(arb_t u1, arb_t u2, const arb_t a, const arb_t b, const arb_t d, slong prec) {
// Compute the orthogonal matrix that diagonalizes
//
// A = [a b]
// [b d]
//
// This matrix will have the form
//
// U = [cos x , -sin x]
// [sin x, cos x]
//
// where the diagonal matrix is U^t A U.
// We set u1 = cos x, u2 = -sin x.
if(arb_contains_zero(b)) {
// this is not quite right (doesn't set error intervals)
arb_set_ui(u1, 1);
arb_set_ui(u2, 0);
return;
}
arb_t x; arb_init(x);
arb_mul(u1, b, b, prec); // u1 = b^2
arb_sub(u2, a, d, prec); // u2 = a - d
arb_mul_2exp_si(u2, u2, -1); // u2 = (a - d)/2
arb_mul(u2, u2, u2, prec); // u2 = ( (a - d)/2 )^2
arb_add(u1, u1, u2, prec); // u1 = b^2 + ( (a-d)/2 )^2
arb_sqrt(u1, u1, prec); // u1 = sqrt(above)
arb_mul_2exp_si(u1, u1, 1); // u1 = 2 (sqrt (above) )
arb_add(u1, u1, d, prec); // u1 += d
arb_sub(u1, u1, a, prec); // u1 -= a
arb_mul_2exp_si(u1, u1, -1); // u1 = (d - a)/2 + sqrt(b^2 + ( (a-d)/2 )^2)
arb_mul(x, u1, u1, prec);
arb_addmul(x, b, b, prec); // x = u1^2 + b^2
arb_sqrt(x, x, prec); // x = sqrt(u1^2 + b^2)
arb_div(u2, u1, x, prec);
arb_div(u1, b, x, prec);
arb_neg(u1, u1);
arb_clear(x);
}
void
arb_mat_sub(arb_mat_t res,
const arb_mat_t mat1, const arb_mat_t mat2, slong prec)
{
slong i, j;
for (i = 0; i < arb_mat_nrows(mat1); i++)
for (j = 0; j < arb_mat_ncols(mat1); j++)
arb_sub(arb_mat_entry(res, i, j),
arb_mat_entry(mat1, i, j),
arb_mat_entry(mat2, i, j), prec);
}
/* This gives some speedup for small lengths. */
static __inline__ void
_arb_poly_rem_2(arb_ptr r, arb_srcptr a, long al,
arb_srcptr b, long bl, long prec)
{
if (al == 2)
{
arb_mul(r + 0, a + 1, b + 0, prec);
arb_sub(r + 0, a + 0, r + 0, prec);
}
else
{
_arb_poly_rem(r, a, al, b, bl, prec);
}
}
int arb_calc_newton_step(arb_t xnew, arb_calc_func_t func,
void * param, const arb_t x, const arb_t conv_region,
const arf_t conv_factor, slong prec)
{
mag_t err, v;
arb_t t;
arb_struct u[2];
int result;
mag_init(err);
mag_init(v);
arb_init(t);
arb_init(u + 0);
arb_init(u + 1);
mag_mul(err, arb_radref(x), arb_radref(x));
arf_get_mag(v, conv_factor);
mag_mul(err, err, v);
arf_set(arb_midref(t), arb_midref(x));
mag_zero(arb_radref(t));
func(u, t, param, 2, prec);
arb_div(u, u, u + 1, prec);
arb_sub(u, t, u, prec);
mag_add(arb_radref(u), arb_radref(u), err);
if (arb_contains(conv_region, u) &&
(mag_cmp(arb_radref(u), arb_radref(x)) < 0))
{
arb_swap(xnew, u);
result = ARB_CALC_SUCCESS;
}
else
{
arb_set(xnew, x);
result = ARB_CALC_NO_CONVERGENCE;
}
arb_clear(t);
arb_clear(u);
arb_clear(u + 1);
mag_clear(err);
mag_clear(v);
return result;
}
int
_arb_poly_newton_step(arb_t xnew, arb_srcptr poly, long len,
const arb_t x,
const arb_t convergence_interval,
const arf_t convergence_factor, long prec)
{
arf_t err;
arb_t t, u, v;
int result;
arf_init(err);
arb_init(t);
arb_init(u);
arb_init(v);
arf_set_mag(err, arb_radref(x));
arf_mul(err, err, err, MAG_BITS, ARF_RND_UP);
arf_mul(err, err, convergence_factor, MAG_BITS, ARF_RND_UP);
arf_set(arb_midref(t), arb_midref(x));
mag_zero(arb_radref(t));
_arb_poly_evaluate2(u, v, poly, len, t, prec);
arb_div(u, u, v, prec);
arb_sub(u, t, u, prec);
arb_add_error_arf(u, err);
if (arb_contains(convergence_interval, u) &&
(mag_cmp(arb_radref(u), arb_radref(x)) < 0))
{
arb_swap(xnew, u);
result = 1;
}
else
{
arb_set(xnew, x);
result = 0;
}
arb_clear(t);
arb_clear(u);
arb_clear(v);
arf_clear(err);
return result;
}
static void
_acb_hypgeom_li_offset(acb_t res, const acb_t z, long prec)
{
if (acb_is_int(z) && arf_cmp_2exp_si(arb_midref(acb_realref(z)), 1) == 0)
{
acb_zero(res);
}
else
{
arb_t t;
arb_init(t);
_acb_hypgeom_const_li2(t, prec);
_acb_hypgeom_li(res, z, prec);
arb_sub(acb_realref(res), acb_realref(res), t, prec);
arb_clear(t);
}
}
static void _stirling_number_1_vec_next(arb_ptr row,
arb_srcptr prev, slong n, slong klen, slong prec)
{
slong k;
if (klen > n) arb_one(row + n);
if (n != 0 && klen != 0) arb_zero(row);
for (k = FLINT_MIN(n, klen) - 1; k >= 1; k--)
{
arb_mul_ui(row + k, prev + k, n - 1, prec);
arb_sub(row + k, prev + k - 1, row + k, prec);
}
for (k = n + 1; k < klen; k++)
arb_zero(row + k);
}
void
arb_zeta_ui_borwein_bsplit(arb_t x, ulong s, slong prec)
{
zeta_bsplit_t sum;
mag_t err;
slong wp, n;
/* zeta(0) = -1/2 */
if (s == 0)
{
arb_set_si(x, -1);
arb_mul_2exp_si(x, x, -1);
return;
}
if (s == 1)
{
flint_printf("zeta_ui_borwein_bsplit: zeta(1)");
abort();
}
n = prec / ERROR_B + 2;
wp = prec + 30;
zeta_bsplit_init(sum);
zeta_bsplit(sum, 0, n + 1, n, s, 0, wp);
/* A/Q3 - B/Q3 / (C/Q1) = (A*C - B*Q1) / (Q3*C) */
arb_mul(sum->A, sum->A, sum->C, wp);
arb_mul(sum->B, sum->B, sum->Q1, wp);
arb_sub(sum->A, sum->A, sum->B, wp);
arb_mul(sum->Q3, sum->Q3, sum->C, wp);
arb_div(sum->C, sum->A, sum->Q3, wp);
mag_init(err);
mag_borwein_error(err, n);
mag_add(arb_radref(sum->C), arb_radref(sum->C), err);
mag_clear(err);
/* convert from eta(s) to zeta(s) */
arb_div_2expm1_ui(x, sum->C, s - 1, wp);
arb_mul_2exp_si(x, x, s - 1);
zeta_bsplit_clear(sum);
}
int
acb_modular_is_in_fundamental_domain(const acb_t z, const arf_t tol, long prec)
{
arb_t t;
arb_init(t);
/* require re(w) + 1/2 >= 0 */
arb_set_ui(t, 1);
arb_mul_2exp_si(t, t, -1);
arb_add(t, t, acb_realref(z), prec);
arb_add_arf(t, t, tol, prec);
if (!arb_is_nonnegative(t))
{
arb_clear(t);
return 0;
}
/* require re(w) - 1/2 <= 0 */
arb_set_ui(t, 1);
arb_mul_2exp_si(t, t, -1);
arb_sub(t, acb_realref(z), t, prec);
arb_sub_arf(t, t, tol, prec);
if (!arb_is_nonpositive(t))
{
arb_clear(t);
return 0;
}
/* require |w| >= 1 - tol, i.e. |w| - 1 + tol >= 0 */
acb_abs(t, z, prec);
arb_sub_ui(t, t, 1, prec);
arb_add_arf(t, t, tol, prec);
if (!arb_is_nonnegative(t))
{
arb_clear(t);
return 0;
}
arb_clear(t);
return 1;
}
int main()
{
long p = 1000;
long d = 53;
arb_t a, b, x, t;
arb_init(a);
arb_init(b);
arb_init(x);
arb_init(t);
// a = 1 + 2 ^ -76
arb_set_str(a, "2", p);
arb_set_str(t, "-76", p);
arb_pow(a, a, t, p);
arb_set_str(t, "1", p);
arb_add(a, t, a, p);
printf("a = "); arb_printd(a, d); printf("\n");
// b = 4 ^ 38 + 0.5
arb_set_str(b, "0.5", p);
arb_ui_pow_ui(t, 4, 38, p);
arb_add(b, t, b, p);
printf("b = "); arb_printd(b, d); printf("\n");
// x = a ^ b
arb_pow(x, a, b, p);
printf("x = "); arb_printd(x, d); printf("\n");
arb_const_e(t, p);
printf("e = "); arb_printd(t, d); printf("\n");
arb_sub(t, x, t, p);
printf("x-e = "); arb_printd(t, d); printf("\n");
printf("Computed with arb-%s\n", arb_version);
arb_clear(a);
arb_clear(b);
arb_clear(x);
arb_clear(t);
}
void
_arb_poly_div_series(arb_ptr Q, arb_srcptr A, long Alen,
arb_srcptr B, long Blen, long n, long prec)
{
Alen = FLINT_MIN(Alen, n);
Blen = FLINT_MIN(Blen, n);
if (Blen == 1)
{
_arb_vec_scalar_div(Q, A, Alen, B, prec);
_arb_vec_zero(Q + Alen, n - Alen);
}
else if (n == 2)
{
if (Alen == 1)
{
arb_div(Q, A, B, prec);
arb_div(Q + 1, Q, B, prec);
arb_mul(Q + 1, Q + 1, B + 1, prec);
arb_neg(Q + 1, Q + 1);
}
else
{
arb_div(Q, A, B, prec);
arb_mul(Q + 1, Q, B + 1, prec);
arb_sub(Q + 1, A + 1, Q + 1, prec);
arb_div(Q + 1, Q + 1, B, prec);
}
}
else
{
arb_ptr Binv;
Binv = _arb_vec_init(n);
_arb_poly_inv_series(Binv, B, Blen, n, prec);
_arb_poly_mullow(Q, Binv, n, A, Alen, n, prec);
_arb_vec_clear(Binv, n);
}
}
void
_arb_poly_taylor_shift_horner(arb_ptr poly, const arb_t c, slong n, slong prec)
{
slong i, j;
if (arb_is_one(c))
{
for (i = n - 2; i >= 0; i--)
for (j = i; j < n - 1; j++)
arb_add(poly + j, poly + j, poly + j + 1, prec);
}
else if (arb_equal_si(c, -1))
{
for (i = n - 2; i >= 0; i--)
for (j = i; j < n - 1; j++)
arb_sub(poly + j, poly + j, poly + j + 1, prec);
}
else if (!arb_is_zero(c))
{
for (i = n - 2; i >= 0; i--)
for (j = i; j < n - 1; j++)
arb_addmul(poly + j, poly + j + 1, c, prec);
}
}
int main()
{
slong iter;
flint_rand_t state;
flint_printf("sub_si....");
fflush(stdout);
flint_randinit(state);
for (iter = 0; iter < 10000; iter++)
{
arb_t a, b, c, d;
slong x;
slong prec;
arb_init(a);
arb_init(b);
arb_init(c);
arb_init(d);
arb_randtest_special(a, state, 1 + n_randint(state, 2000), 100);
arb_randtest_special(b, state, 1 + n_randint(state, 2000), 100);
arb_randtest_special(c, state, 1 + n_randint(state, 2000), 100);
x = z_randtest(state);
prec = 2 + n_randint(state, 2000);
arb_set_si(b, x);
arb_sub_si(c, a, x, prec);
arb_sub(d, a, b, prec);
if (!arb_equal(c, d))
{
flint_printf("FAIL\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");
flint_printf("d = "); arb_print(d); flint_printf("\n\n");
abort();
}
arb_clear(a);
arb_clear(b);
arb_clear(c);
arb_clear(d);
}
/* aliasing */
for (iter = 0; iter < 10000; iter++)
{
arb_t a, b, c;
slong x;
slong prec;
arb_init(a);
arb_init(b);
arb_init(c);
arb_randtest_special(a, state, 1 + n_randint(state, 2000), 100);
arb_randtest_special(b, state, 1 + n_randint(state, 2000), 100);
arb_randtest_special(c, state, 1 + n_randint(state, 2000), 100);
x = z_randtest(state);
prec = 2 + n_randint(state, 2000);
arb_set_si(b, x);
arb_sub_si(c, a, x, prec);
arb_sub_si(a, a, x, prec);
if (!arb_equal(a, c))
{
flint_printf("FAIL (aliasing)\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_clear(a);
arb_clear(b);
arb_clear(c);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
void
acb_hypgeom_ci_asymp(acb_t res, const acb_t z, slong prec)
{
acb_t t, u, w, v, one;
acb_init(t);
acb_init(u);
acb_init(w);
acb_init(v);
acb_init(one);
acb_one(one);
acb_mul_onei(w, z);
/* u = U(1,1,iz) */
acb_hypgeom_u_asymp(u, one, one, w, -1, prec);
/* v = e^(-iz) */
acb_neg(v, w);
acb_exp(v, v, prec);
acb_mul(t, u, v, prec);
if (acb_is_real(z))
{
arb_div(acb_realref(t), acb_imagref(t), acb_realref(z), prec);
arb_zero(acb_imagref(t));
acb_neg(t, t);
}
else
{
/* u = U(1,1,-iz) */
acb_neg(w, w);
acb_hypgeom_u_asymp(u, one, one, w, -1, prec);
acb_inv(v, v, prec);
acb_submul(t, u, v, prec);
acb_div(t, t, w, prec);
acb_mul_2exp_si(t, t, -1);
}
if (arb_is_zero(acb_realref(z)))
{
if (arb_is_positive(acb_imagref(z)))
{
arb_const_pi(acb_imagref(t), prec);
arb_mul_2exp_si(acb_imagref(t), acb_imagref(t), -1);
}
else if (arb_is_negative(acb_imagref(z)))
{
arb_const_pi(acb_imagref(t), prec);
arb_mul_2exp_si(acb_imagref(t), acb_imagref(t), -1);
arb_neg(acb_imagref(t), acb_imagref(t));
}
else
{
acb_const_pi(u, prec);
acb_mul_2exp_si(u, u, -1);
arb_zero(acb_imagref(t));
arb_add_error(acb_imagref(t), acb_realref(u));
}
}
else
{
/* 0 if positive or positive imaginary
pi if upper left quadrant (including negative real axis)
-pi if lower left quadrant (including negative imaginary axis) */
if (arb_is_positive(acb_realref(z)))
{
/* do nothing */
}
else if (arb_is_negative(acb_realref(z)) && arb_is_nonnegative(acb_imagref(z)))
{
acb_const_pi(u, prec);
arb_add(acb_imagref(t), acb_imagref(t), acb_realref(u), prec);
}
else if (arb_is_nonpositive(acb_realref(z)) && arb_is_negative(acb_imagref(z)))
{
acb_const_pi(u, prec);
arb_sub(acb_imagref(t), acb_imagref(t), acb_realref(u), prec);
}
else
{
/* add [-pi,pi] */
acb_const_pi(u, prec);
arb_add_error(acb_imagref(t), acb_realref(u));
}
}
acb_swap(res, t);
acb_clear(t);
acb_clear(u);
acb_clear(w);
acb_clear(v);
acb_clear(one);
}
void
keiper_li_series(arb_ptr z, slong len, slong prec)
{
arb_ptr t, u, v;
t = _arb_vec_init(len);
u = _arb_vec_init(len);
v = _arb_vec_init(len);
/* -zeta(s) */
flint_printf("zeta: ");
TIMEIT_ONCE_START
arb_zero(t + 0);
arb_one(t + 1);
arb_one(u);
_arb_poly_zeta_series(v, t, 2, u, 0, len, prec);
_arb_vec_neg(v, v, len);
TIMEIT_ONCE_STOP
SHOW_MEMORY_USAGE
/* logarithm */
flint_printf("log: ");
TIMEIT_ONCE_START
_arb_poly_log_series(t, v, len, len, prec);
TIMEIT_ONCE_STOP
/* add log(gamma(1+s/2)) */
flint_printf("gamma: ");
TIMEIT_ONCE_START
arb_one(u);
arb_one(u + 1);
arb_mul_2exp_si(u + 1, u + 1, -1);
_arb_poly_lgamma_series(v, u, 2, len, prec);
_arb_vec_add(t, t, v, len, prec);
TIMEIT_ONCE_STOP
/* subtract 0.5 s log(pi) */
arb_const_pi(u, prec);
arb_log(u, u, prec);
arb_mul_2exp_si(u, u, -1);
arb_sub(t + 1, t + 1, u, prec);
/* add log(1-s) */
arb_one(u);
arb_set_si(u + 1, -1);
_arb_poly_log_series(v, u, 2, len, prec);
_arb_vec_add(t, t, v, len, prec);
/* binomial transform */
flint_printf("binomial transform: ");
TIMEIT_ONCE_START
arb_set(z, t);
_arb_vec_neg(t + 1, t + 1, len - 1);
_arb_poly_binomial_transform(z + 1, t + 1, len - 1, len - 1, prec);
TIMEIT_ONCE_STOP
_arb_vec_clear(t, len);
_arb_vec_clear(u, len);
_arb_vec_clear(v, len);
}
void
_arb_bell_sum_taylor(arb_t res, const fmpz_t n,
const fmpz_t a, const fmpz_t b, const fmpz_t mmag, long tol)
{
fmpz_t m, r, R, tmp;
mag_t B, C, D, bound;
arb_t t, u;
long wp, k, N;
if (_fmpz_sub_small(b, a) < 5)
{
arb_bell_sum_bsplit(res, n, a, b, mmag, tol);
return;
}
fmpz_init(m);
fmpz_init(r);
fmpz_init(R);
fmpz_init(tmp);
/* r = max(m - a, b - m) */
/* m = a + (b - a) / 2 */
fmpz_sub(r, b, a);
fmpz_cdiv_q_2exp(r, r, 1);
fmpz_add(m, a, r);
fmpz_mul_2exp(R, r, RADIUS_BITS);
mag_init(B);
mag_init(C);
mag_init(D);
mag_init(bound);
arb_init(t);
arb_init(u);
if (fmpz_cmp(R, m) >= 0)
{
mag_inf(C);
mag_inf(D);
}
else
{
/* C = exp(R * |F'(m)| + (1/2) R^2 * (n/(m-R)^2 + 1/(m-R))) */
/* C = exp(R * (|F'(m)| + (1/2) R * (n/(m-R) + 1)/(m-R))) */
/* D = (1/2) R * (n/(m-R) + 1)/(m-R) */
fmpz_sub(tmp, m, R);
mag_set_fmpz(D, n);
mag_div_fmpz(D, D, tmp);
mag_one(C);
mag_add(D, D, C);
mag_div_fmpz(D, D, tmp);
mag_mul_fmpz(D, D, R);
mag_mul_2exp_si(D, D, -1);
/* C = |F'(m)| */
wp = 20 + 1.05 * fmpz_bits(n);
arb_set_fmpz(t, n);
arb_div_fmpz(t, t, m, wp);
fmpz_add_ui(tmp, m, 1);
arb_set_fmpz(u, tmp);
arb_digamma(u, u, wp);
arb_sub(t, t, u, wp);
arb_get_mag(C, t);
/* C = exp(R * (C + D)) */
mag_add(C, C, D);
mag_mul_fmpz(C, C, R);
mag_exp(C, C);
}
if (mag_cmp_2exp_si(C, tol / 4 + 2) > 0)
{
_arb_bell_sum_taylor(res, n, a, m, mmag, tol);
_arb_bell_sum_taylor(t, n, m, b, mmag, tol);
arb_add(res, res, t, 2 * tol);
}
else
{
arb_ptr mx, ser1, ser2, ser3;
/* D = T(m) */
wp = 20 + 1.05 * fmpz_bits(n);
arb_set_fmpz(t, m);
arb_pow_fmpz(t, t, n, wp);
fmpz_add_ui(tmp, m, 1);
arb_gamma_fmpz(u, tmp, wp);
arb_div(t, t, u, wp);
arb_get_mag(D, t);
/* error bound: (b-a) * C * D * B^N / (1 - B), B = r/R */
/* ((b-a) * C * D * 2) * 2^(-N*RADIUS_BITS) */
/* ((b-a) * C * D * 2) */
mag_mul(bound, C, D);
mag_mul_2exp_si(bound, bound, 1);
fmpz_sub(tmp, b, a);
mag_mul_fmpz(bound, bound, tmp);
/* N = (tol + log2((b-a)*C*D*2) - mmag) / RADIUS_BITS */
if (mmag == NULL)
{
/* estimate D ~= 2^mmag */
fmpz_add_ui(tmp, MAG_EXPREF(C), tol);
fmpz_cdiv_q_ui(tmp, tmp, RADIUS_BITS);
}
else
{
fmpz_sub(tmp, MAG_EXPREF(bound), mmag);
fmpz_add_ui(tmp, tmp, tol);
fmpz_cdiv_q_ui(tmp, tmp, RADIUS_BITS);
}
if (fmpz_cmp_ui(tmp, 5 * tol / 4) > 0)
N = 5 * tol / 4;
else if (fmpz_cmp_ui(tmp, 2) < 0)
N = 2;
else
N = fmpz_get_ui(tmp);
/* multiply by 2^(-N*RADIUS_BITS) */
mag_mul_2exp_si(bound, bound, -N * RADIUS_BITS);
mx = _arb_vec_init(2);
ser1 = _arb_vec_init(N);
ser2 = _arb_vec_init(N);
ser3 = _arb_vec_init(N);
/* estimate (this should work for moderate n and tol) */
wp = 1.1 * tol + 1.05 * fmpz_bits(n) + 5;
/* increase precision until convergence */
while (1)
{
/* (m+x)^n / gamma(m+1+x) */
arb_set_fmpz(mx, m);
arb_one(mx + 1);
_arb_poly_log_series(ser1, mx, 2, N, wp);
for (k = 0; k < N; k++)
arb_mul_fmpz(ser1 + k, ser1 + k, n, wp);
arb_add_ui(mx, mx, 1, wp);
_arb_poly_lgamma_series(ser2, mx, 2, N, wp);
_arb_vec_sub(ser1, ser1, ser2, N, wp);
_arb_poly_exp_series(ser3, ser1, N, N, wp);
/* t = a - m, u = b - m */
arb_set_fmpz(t, a);
arb_sub_fmpz(t, t, m, wp);
arb_set_fmpz(u, b);
arb_sub_fmpz(u, u, m, wp);
arb_power_sum_vec(ser1, t, u, N, wp);
arb_zero(res);
for (k = 0; k < N; k++)
arb_addmul(res, ser3 + k, ser1 + k, wp);
if (mmag != NULL)
{
if (_fmpz_sub_small(MAG_EXPREF(arb_radref(res)), mmag) <= -tol)
break;
}
else
{
if (arb_rel_accuracy_bits(res) >= tol)
break;
}
wp = 2 * wp;
}
/* add the series truncation bound */
arb_add_error_mag(res, bound);
_arb_vec_clear(mx, 2);
_arb_vec_clear(ser1, N);
_arb_vec_clear(ser2, N);
_arb_vec_clear(ser3, N);
}
mag_clear(B);
mag_clear(C);
mag_clear(D);
mag_clear(bound);
arb_clear(t);
arb_clear(u);
fmpz_clear(m);
fmpz_clear(r);
fmpz_clear(R);
fmpz_clear(tmp);
}
void Lib_Arb_Sub(ArbPtr f, ArbPtr g, ArbPtr h, int32_t prec)
{
arb_sub( (arb_ptr) f, (arb_ptr) g, (arb_ptr) h, prec);
}
void
acb_sqrt(acb_t y, const acb_t x, slong prec)
{
arb_t r, t, u;
slong wp;
#define a acb_realref(x)
#define b acb_imagref(x)
#define c acb_realref(y)
#define d acb_imagref(y)
if (arb_is_zero(b))
{
if (arb_is_nonnegative(a))
{
arb_sqrt(c, a, prec);
arb_zero(d);
return;
}
else if (arb_is_nonpositive(a))
{
arb_neg(d, a);
arb_sqrt(d, d, prec);
arb_zero(c);
return;
}
}
if (arb_is_zero(a))
{
if (arb_is_nonnegative(b))
{
arb_mul_2exp_si(c, b, -1);
arb_sqrt(c, c, prec);
arb_set(d, c);
return;
}
else if (arb_is_nonpositive(b))
{
arb_mul_2exp_si(c, b, -1);
arb_neg(c, c);
arb_sqrt(c, c, prec);
arb_neg(d, c);
return;
}
}
wp = prec + 4;
arb_init(r);
arb_init(t);
arb_init(u);
acb_abs(r, x, wp);
arb_add(t, r, a, wp);
if (arb_rel_accuracy_bits(t) > 8)
{
/* sqrt(a+bi) = sqrt((r+a)/2) + b/sqrt(2*(r+a))*i, r = |a+bi| */
arb_mul_2exp_si(u, t, 1);
arb_sqrt(u, u, wp);
arb_div(d, b, u, prec);
arb_set_round(c, u, prec);
arb_mul_2exp_si(c, c, -1);
}
else
{
/*
sqrt(a+bi) = sqrt((r+a)/2) + (b/|b|)*sqrt((r-a)/2)*i
(sign)
*/
arb_mul_2exp_si(t, t, -1);
arb_sub(u, r, a, wp);
arb_mul_2exp_si(u, u, -1);
arb_sqrtpos(c, t, prec);
if (arb_is_nonnegative(b))
{
arb_sqrtpos(d, u, prec);
}
else if (arb_is_nonpositive(b))
{
arb_sqrtpos(d, u, prec);
arb_neg(d, d);
}
else
{
arb_sqrtpos(t, u, wp);
arb_neg(u, t);
arb_union(d, t, u, prec);
}
}
arb_clear(r);
arb_clear(t);
arb_clear(u);
#undef a
#undef b
#undef c
#undef d
}
int renf_elem_cmp_fmpq(renf_elem_t a, const fmpq_t b, renf_t nf)
{
int s;
slong prec, cond;
arb_t diffball;
renf_elem_t diffnf;
if (fmpq_is_zero(b))
return renf_elem_sgn(a, nf);
if (nf_elem_is_rational(a->elem, nf->nf))
{
if (nf->nf->flag & NF_LINEAR)
return _fmpq_cmp(LNF_ELEM_NUMREF(a->elem),
LNF_ELEM_DENREF(a->elem),
fmpq_numref(b),
fmpq_denref(b));
else if (nf->nf->flag & NF_QUADRATIC)
return _fmpq_cmp(QNF_ELEM_NUMREF(a->elem),
QNF_ELEM_DENREF(a->elem),
fmpq_numref(b),
fmpq_denref(b));
else
return _fmpq_cmp(NF_ELEM_NUMREF(a->elem),
NF_ELEM_DENREF(a->elem),
fmpq_numref(b),
fmpq_denref(b));
}
arb_init(diffball);
arb_set_fmpq(diffball, b, nf->prec);
arb_sub(diffball, a->emb, diffball, nf->prec);
if (!arb_contains_zero(diffball))
{
s = arf_sgn(arb_midref(diffball));
arb_clear(diffball);
return s;
}
renf_elem_relative_condition_number_2exp(&cond, a, nf);
prec = FLINT_MAX(nf->prec, arb_rel_accuracy_bits(nf->emb));
renf_elem_set_evaluation(a, nf, prec + cond);
arb_set_fmpq(diffball, b, prec);
arb_sub(diffball, a->emb, diffball, prec);
if (!arb_contains_zero(diffball))
{
s = arf_sgn(arb_midref(diffball));
arb_clear(diffball);
return s;
}
arb_clear(diffball);
renf_elem_init(diffnf, nf);
renf_elem_set(diffnf, a, nf);
renf_elem_sub_fmpq(diffnf, diffnf, b, nf);
s = renf_elem_sgn(diffnf, nf);
renf_elem_clear(diffnf, nf);
return s;
}
void
acb_calc_cauchy_bound(arb_t bound, acb_calc_func_t func, void * param,
const acb_t x, const arb_t radius, slong maxdepth, slong prec)
{
slong i, n, depth, wp;
arb_t pi, theta, v, s1, c1, s2, c2, st, ct;
acb_t t, u;
arb_t b;
arb_init(pi);
arb_init(theta);
arb_init(v);
arb_init(s1);
arb_init(c1);
arb_init(s2);
arb_init(c2);
arb_init(st);
arb_init(ct);
acb_init(t);
acb_init(u);
arb_init(b);
wp = prec + 20;
arb_const_pi(pi, wp);
arb_zero_pm_inf(b);
for (depth = 0, n = 16; depth < maxdepth; n *= 2, depth++)
{
arb_zero(b);
/* theta = 2 pi / n */
arb_div_ui(theta, pi, n, wp);
arb_mul_2exp_si(theta, theta, 1);
/* sine and cosine of i*theta and (i+1)*theta */
arb_zero(s1);
arb_one(c1);
arb_sin_cos(st, ct, theta, wp);
arb_set(s2, st);
arb_set(c2, ct);
for (i = 0; i < n; i++)
{
/* sine and cosine of 2 pi ([i,i+1]/n) */
/* since we use power of two subdivision points, the
sine and cosine are monotone on each subinterval */
arb_union(acb_realref(t), c1, c2, wp);
arb_union(acb_imagref(t), s1, s2, wp);
acb_mul_arb(t, t, radius, wp);
acb_add(t, t, x, prec);
/* next angle */
arb_mul(v, c2, ct, wp);
arb_mul(c1, s2, st, wp);
arb_sub(c1, v, c1, wp);
arb_mul(v, c2, st, wp);
arb_mul(s1, s2, ct, wp);
arb_add(s1, v, s1, wp);
arb_swap(c1, c2);
arb_swap(s1, s2);
func(u, t, param, 1, prec);
acb_abs(v, u, prec);
arb_add(b, b, v, prec);
}
arb_div_ui(b, b, n, prec);
if (arb_is_positive(b))
break;
}
arb_set(bound, b);
arb_clear(pi);
arb_clear(theta);
arb_clear(v);
acb_clear(t);
acb_clear(u);
arb_clear(b);
arb_clear(s1);
arb_clear(c1);
arb_clear(s2);
arb_clear(c2);
arb_clear(st);
arb_clear(ct);
}
int arb_mat_jacobi(arb_mat_t D, arb_mat_t P, const arb_mat_t A, slong prec) {
//
// Given a d x d real symmetric matrix A, compute an orthogonal matrix
// P and a diagonal D such that A = P D P^t = P D P^(-1).
//
// D should have already been initialized as a d x 1 matrix, and Pp
// should have already been initialized as a d x d matrix.
//
// If the eigenvalues can be certified as unique, then a nonzero int is
// returned, and the eigenvectors should have reasonable error bounds. If
// the eigenvalues cannot be certified as unique, then some of the
// eigenvectors will have infinite error radius.
#define B(i,j) arb_mat_entry(B, i, j)
#define D(i) arb_mat_entry(D, i, 0)
#define P(i,j) arb_mat_entry(P, i, j)
int dim = arb_mat_nrows(A);
if(dim == 1) {
arb_mat_set(D, A);
arb_mat_one(P);
return 0;
}
arb_mat_t B;
arb_mat_init(B, dim, dim);
arf_t * B1 = (arf_t*)malloc(dim * sizeof(arf_t));
arf_t * B2 = (arf_t*)malloc(dim * sizeof(arf_t));
arf_t * row_max = (arf_t*)malloc((dim - 1) * sizeof(arf_t));
int * row_max_indices = (int*)malloc((dim - 1) * sizeof(int));
for(int k = 0; k < dim; k++) {
arf_init(B1[k]);
arf_init(B2[k]);
}
for(int k = 0; k < dim - 1; k++) {
arf_init(row_max[k]);
}
arf_t x1, x2;
arf_init(x1);
arf_init(x2);
arf_t Gii, Gij, Gji, Gjj;
arf_init(Gii);
arf_init(Gij);
arf_init(Gji);
arf_init(Gjj);
arb_mat_set(B, A);
arb_mat_one(P);
for(int i = 0; i < dim - 1; i++) {
for(int j = i + 1; j < dim; j++) {
arf_abs(x1, arb_midref(B(i,j)));
if(arf_cmp(row_max[i], x1) < 0) {
arf_set(row_max[i], x1);
row_max_indices[i] = j;
}
}
}
int finished = 0;
while(!finished) {
arf_zero(x1);
int i = 0;
int j = 0;
for(int k = 0; k < dim - 1; k++) {
if(arf_cmp(x1, row_max[k]) < 0) {
arf_set(x1, row_max[k]);
i = k;
}
}
j = row_max_indices[i];
slong bound = arf_abs_bound_lt_2exp_si(x1);
if(bound < -prec * .9) {
finished = 1;
break;
}
else {
//printf("%ld\n", arf_abs_bound_lt_2exp_si(x1));
//arb_mat_printd(B, 10);
//printf("\n");
}
arf_twobytwo_diag(Gii, Gij, arb_midref(B(i,i)), arb_midref(B(i,j)), arb_midref(B(j,j)), 2*prec);
arf_neg(Gji, Gij);
arf_set(Gjj, Gii);
//printf("%d %d\n", i, j);
//arf_printd(Gii, 100);
//printf(" ");
//arf_printd(Gij, 100);
//printf("\n");
if(arf_is_zero(Gij)) { // If this happens, we're
finished = 1; // not going to do any better
break; // without increasing the precision.
}
for(int k = 0; k < dim; k++) {
arf_mul(B1[k], Gii, arb_midref(B(i,k)), prec, ARF_RND_NEAR);
arf_addmul(B1[k], Gji, arb_midref(B(j,k)), prec, ARF_RND_NEAR);
arf_mul(B2[k], Gij, arb_midref(B(i,k)), prec, ARF_RND_NEAR);
arf_addmul(B2[k], Gjj, arb_midref(B(j,k)), prec, ARF_RND_NEAR);
}
for(int k = 0; k < dim; k++) {
arf_set(arb_midref(B(i,k)), B1[k]);
arf_set(arb_midref(B(j,k)), B2[k]);
}
for(int k = 0; k < dim; k++) {
arf_mul(B1[k], Gii, arb_midref(B(k,i)), prec, ARF_RND_NEAR);
arf_addmul(B1[k], Gji, arb_midref(B(k,j)), prec, ARF_RND_NEAR);
arf_mul(B2[k], Gij, arb_midref(B(k,i)), prec, ARF_RND_NEAR);
arf_addmul(B2[k], Gjj, arb_midref(B(k,j)), prec, ARF_RND_NEAR);
}
for(int k = 0; k < dim; k++) {
arf_set(arb_midref(B(k,i)), B1[k]);
arf_set(arb_midref(B(k,j)), B2[k]);
}
for(int k = 0; k < dim; k++) {
arf_mul(B1[k], Gii, arb_midref(P(k,i)), prec, ARF_RND_NEAR);
arf_addmul(B1[k], Gji, arb_midref(P(k,j)), prec, ARF_RND_NEAR);
arf_mul(B2[k], Gij, arb_midref(P(k,i)), prec, ARF_RND_NEAR);
arf_addmul(B2[k], Gjj, arb_midref(P(k,j)), prec, ARF_RND_NEAR);
}
for(int k = 0; k < dim; k++) {
arf_set(arb_midref(P(k,i)), B1[k]);
arf_set(arb_midref(P(k,j)), B2[k]);
}
if(i < dim - 1)
arf_set_ui(row_max[i], 0);
if(j < dim - 1)
arf_set_ui(row_max[j], 0);
// Update the max in any row where the maximum
// was in a column that changed.
for(int k = 0; k < dim - 1; k++) {
if(row_max_indices[k] == j || row_max_indices[k] == i) {
arf_abs(row_max[k], arb_midref(B(k,k+1)));
row_max_indices[k] = k+1;
for(int l = k+2; l < dim; l++) {
arf_abs(x1, arb_midref(B(k,l)));
if(arf_cmp(row_max[k], x1) < 0) {
arf_set(row_max[k], x1);
row_max_indices[k] = l;
}
}
}
}
// Update the max in the ith row.
for(int k = i + 1; k < dim; k++) {
arf_abs(x1, arb_midref(B(i, k)));
if(arf_cmp(row_max[i], x1) < 0) {
arf_set(row_max[i], x1);
row_max_indices[i] = k;
}
}
// Update the max in the jth row.
for(int k = j + 1; k < dim; k++) {
arf_abs(x1, arb_midref(B(j, k)));
if(arf_cmp(row_max[j], x1) < 0) {
arf_set(row_max[j], x1);
row_max_indices[j] = k;
}
}
// Go through column i to see if any of
// the new entries are larger than the
// max of their row.
for(int k = 0; k < i; k++) {
if(k == dim) continue;
arf_abs(x1, arb_midref(B(k, i)));
if(arf_cmp(row_max[k], x1) < 0) {
arf_set(row_max[k], x1);
row_max_indices[k] = i;
}
}
// And then column j.
for(int k = 0; k < j; k++) {
if(k == dim) continue;
arf_abs(x1, arb_midref(B(k, j)));
if(arf_cmp(row_max[k], x1) < 0) {
arf_set(row_max[k], x1);
row_max_indices[k] = j;
}
}
}
for(int k = 0; k < dim; k++) {
arb_set(D(k), B(k,k));
arb_set_exact(D(k));
}
// At this point we've done that diagonalization and all that remains is
// to certify the correctness and compute error bounds.
arb_mat_t e;
arb_t error_norms[dim];
for(int k = 0; k < dim; k++) arb_init(error_norms[k]);
arb_mat_init(e, dim, 1);
arb_t z1, z2;
arb_init(z1);
arb_init(z2);
for(int j = 0; j < dim; j++) {
arb_mat_set(B, A);
for(int k = 0; k < dim; k++) {
arb_sub(B(k, k), B(k, k), D(j), prec);
}
for(int k = 0; k < dim; k++) {
arb_set(arb_mat_entry(e, k, 0), P(k, j));
}
arb_mat_L2norm(z2, e, prec);
arb_mat_mul(e, B, e, prec);
arb_mat_L2norm(error_norms[j], e, prec);
arb_div(z2, error_norms[j], z2, prec); // and now z1 is an upper bound for the
// error in the eigenvalue
arb_add_error(D(j), z2);
}
int unique_eigenvalues = 1;
for(int j = 0; j < dim; j++) {
if(j == 0) {
arb_sub(z1, D(j), D(1), prec);
}
else {
arb_sub(z1, D(j), D(0), prec);
}
arb_get_abs_lbound_arf(x1, z1, prec);
for(int k = 1; k < dim; k++) {
if(k == j) continue;
arb_sub(z1, D(j), D(k), prec);
arb_get_abs_lbound_arf(x2, z1, prec);
if(arf_cmp(x2, x1) < 0) {
arf_set(x1, x2);
}
}
if(arf_is_zero(x1)) {
unique_eigenvalues = 0;
}
arb_div_arf(z1, error_norms[j], x1, prec);
for(int k = 0; k < dim; k++) {
arb_add_error(P(k, j), z1);
}
}
arb_mat_clear(e);
arb_clear(z1);
arb_clear(z2);
for(int k = 0; k < dim; k++) arb_clear(error_norms[k]);
arf_clear(x1);
arf_clear(x2);
arb_mat_clear(B);
for(int k = 0; k < dim; k++) {
arf_clear(B1[k]);
arf_clear(B2[k]);
}
for(int k = 0; k < dim - 1; k++) {
arf_clear(row_max[k]);
}
arf_clear(Gii);
arf_clear(Gij);
arf_clear(Gji);
arf_clear(Gjj);
free(B1);
free(B2);
free(row_max);
free(row_max_indices);
if(unique_eigenvalues) return 0;
else return 1;
#undef B
#undef D
#undef P
}
int main()
{
slong iter;
flint_rand_t state;
flint_printf("get_mpn_fixed_mod_pi4....");
fflush(stdout);
flint_randinit(state);
/* _flint_rand_init_gmp(state); */
for (iter = 0; iter < 100000 * arb_test_multiplier(); iter++)
{
arf_t x;
int octant;
fmpz_t q;
mp_ptr w;
arb_t wb, t, u;
mp_size_t wn;
slong prec, prec2;
int success;
mp_limb_t error;
prec = 2 + n_randint(state, 10000);
wn = 1 + n_randint(state, 200);
prec2 = FLINT_MAX(prec, wn * FLINT_BITS) + 100;
arf_init(x);
arb_init(wb);
arb_init(t);
arb_init(u);
fmpz_init(q);
w = flint_malloc(sizeof(mp_limb_t) * wn);
arf_randtest(x, state, prec, 14);
/* this should generate numbers close to multiples of pi/4 */
if (n_randint(state, 4) == 0)
{
arb_const_pi(t, prec);
arb_mul_2exp_si(t, t, -2);
fmpz_randtest(q, state, 200);
arb_mul_fmpz(t, t, q, prec);
arf_add(x, x, arb_midref(t), prec, ARF_RND_DOWN);
}
arf_abs(x, x);
success = _arb_get_mpn_fixed_mod_pi4(w, q, &octant, &error, x, wn);
if (success)
{
/* could round differently */
if (fmpz_fdiv_ui(q, 8) != octant)
{
flint_printf("bad octant\n");
abort();
}
_arf_set_mpn_fixed(arb_midref(wb), w, wn, wn, 0, FLINT_BITS * wn, ARB_RND);
mag_set_ui_2exp_si(arb_radref(wb), error, -FLINT_BITS * wn);
arb_const_pi(u, prec2);
arb_mul_2exp_si(u, u, -2);
arb_set(t, wb);
if (octant % 2 == 1)
arb_sub(t, u, t, prec2);
arb_addmul_fmpz(t, u, q, prec2);
if (!arb_contains_arf(t, x))
{
flint_printf("FAIL (containment)\n");
flint_printf("x = "); arf_printd(x, 50); flint_printf("\n\n");
flint_printf("q = "); fmpz_print(q); flint_printf("\n\n");
flint_printf("w = "); arb_printd(wb, 50); flint_printf("\n\n");
flint_printf("t = "); arb_printd(t, 50); flint_printf("\n\n");
abort();
}
arb_const_pi(t, prec2);
arb_mul_2exp_si(t, t, -2);
if (arf_sgn(arb_midref(wb)) < 0 ||
arf_cmp(arb_midref(wb), arb_midref(t)) >= 0)
{
flint_printf("FAIL (expected 0 <= w < pi/4)\n");
flint_printf("x = "); arf_printd(x, 50); flint_printf("\n\n");
flint_printf("w = "); arb_printd(wb, 50); flint_printf("\n\n");
abort();
}
}
flint_free(w);
fmpz_clear(q);
arf_clear(x);
arb_clear(wb);
arb_clear(t);
arb_clear(u);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
void
acb_hypgeom_chi_asymp(acb_t res, const acb_t z, slong prec)
{
acb_t t, u, v, one;
acb_init(t);
acb_init(u);
acb_init(v);
acb_init(one);
acb_one(one);
/* u = U(1,1,z) */
acb_hypgeom_u_asymp(u, one, one, z, -1, prec);
/* v = e^(-z) */
acb_neg(v, z);
acb_exp(v, v, prec);
acb_mul(t, u, v, prec);
if (arb_is_zero(acb_realref(z)))
{
arb_div(acb_realref(t), acb_imagref(t), acb_imagref(z), prec);
arb_zero(acb_imagref(t));
acb_neg(t, t);
}
else
{
/* u = U(1,1,-z) */
acb_neg(u, z);
acb_hypgeom_u_asymp(u, one, one, u, -1, prec);
acb_inv(v, v, prec);
acb_submul(t, u, v, prec);
acb_div(t, t, z, prec);
acb_mul_2exp_si(t, t, -1);
acb_neg(t, t);
}
if (acb_is_real(z))
{
if (arb_is_positive(acb_realref(z)))
{
arb_zero(acb_imagref(t));
}
else if (arb_is_negative(acb_realref(z)))
{
arb_const_pi(acb_imagref(t), prec);
}
else
{
/* add [-pi,pi]/2 i */
acb_const_pi(u, prec);
arb_zero(acb_imagref(t));
arb_add_error(acb_imagref(t), acb_realref(u));
}
}
else
{
/* -pi/2 if positive real or in lower half plane
pi/2 if negative real or in upper half plane */
if (arb_is_negative(acb_imagref(z)))
{
acb_const_pi(u, prec);
acb_mul_2exp_si(u, u, -1);
arb_sub(acb_imagref(t), acb_imagref(t), acb_realref(u), prec);
}
else if (arb_is_positive(acb_imagref(z)))
{
acb_const_pi(u, prec);
acb_mul_2exp_si(u, u, -1);
arb_add(acb_imagref(t), acb_imagref(t), acb_realref(u), prec);
}
else
{
/* add [-pi,pi]/2 i */
acb_const_pi(u, prec);
acb_mul_2exp_si(u, u, -1);
arb_add_error(acb_imagref(t), acb_realref(u));
}
}
acb_swap(res, t);
acb_clear(t);
acb_clear(u);
acb_clear(v);
acb_clear(one);
}
void
acb_gamma_stirling_eval(acb_t s, const acb_t z, long nterms, int digamma, long prec)
{
acb_t t, logz, zinv, zinv2;
arb_t b;
mag_t err;
long k, term_prec;
double z_mag, term_mag;
acb_init(t);
acb_init(logz);
acb_init(zinv);
acb_init(zinv2);
arb_init(b);
acb_log(logz, z, prec);
acb_inv(zinv, z, prec);
nterms = FLINT_MAX(nterms, 1);
acb_zero(s);
if (nterms > 1)
{
acb_mul(zinv2, zinv, zinv, prec);
z_mag = arf_get_d(arb_midref(acb_realref(logz)), ARF_RND_UP) * 1.44269504088896;
for (k = nterms - 1; k >= 1; k--)
{
term_mag = bernoulli_bound_2exp_si(2 * k);
term_mag -= (2 * k - 1) * z_mag;
term_prec = prec + term_mag;
term_prec = FLINT_MIN(term_prec, prec);
term_prec = FLINT_MAX(term_prec, 10);
arb_gamma_stirling_coeff(b, k, digamma, term_prec);
if (prec > 2000)
{
acb_set_round(t, zinv2, term_prec);
acb_mul(s, s, t, term_prec);
}
else
acb_mul(s, s, zinv2, term_prec);
arb_add(acb_realref(s), acb_realref(s), b, term_prec);
}
if (digamma)
acb_mul(s, s, zinv2, prec);
else
acb_mul(s, s, zinv, prec);
}
/* remainder bound */
mag_init(err);
acb_gamma_stirling_bound(err, z, digamma ? 1 : 0, 1, nterms);
mag_add(arb_radref(acb_realref(s)), arb_radref(acb_realref(s)), err);
mag_add(arb_radref(acb_imagref(s)), arb_radref(acb_imagref(s)), err);
mag_clear(err);
if (digamma)
{
acb_neg(s, s);
acb_mul_2exp_si(zinv, zinv, -1);
acb_sub(s, s, zinv, prec);
acb_add(s, s, logz, prec);
}
else
{
/* (z-0.5)*log(z) - z + log(2*pi)/2 */
arb_one(b);
arb_mul_2exp_si(b, b, -1);
arb_set(acb_imagref(t), acb_imagref(z));
arb_sub(acb_realref(t), acb_realref(z), b, prec);
acb_mul(t, logz, t, prec);
acb_add(s, s, t, prec);
acb_sub(s, s, z, prec);
arb_const_log_sqrt2pi(b, prec);
arb_add(acb_realref(s), acb_realref(s), b, prec);
}
acb_clear(t);
acb_clear(logz);
acb_clear(zinv);
acb_clear(zinv2);
arb_clear(b);
}