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
acb_lambertw_principal_d(acb_t res, const acb_t z)
{
double za, zb, wa, wb, ewa, ewb, t, u, q, r;
int k, maxk = 15;
za = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
zb = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
/* make sure we end up on the right branch */
if (za < -0.367 && zb > -1e-20 && zb <= 0.0
&& arf_sgn(arb_midref(acb_imagref(z))) < 0)
zb = -1e-20;
wa = za;
wb = zb;
if (fabs(wa) > 2.0 || fabs(wb) > 2.0)
{
t = atan2(wb, wa);
wa = 0.5 * log(wa * wa + wb * wb);
wb = t;
}
else if (fabs(wa) > 0.25 || fabs(wb) > 0.25)
{
/* We have W(z) ~= -1 + (2(ez+1))^(1/2) near the branch point.
Changing the exponent to 1/4 gives a much worse local guess
which however does the job on a larger domain. */
wa *= 5.43656365691809;
wb *= 5.43656365691809;
wa += 2.0;
t = atan2(wb, wa);
r = pow(wa * wa + wb * wb, 0.125);
wa = r * cos(0.25 * t);
wb = r * sin(0.25 * t);
wa -= 1.0;
}
for (k = 0; k < maxk; k++)
{
t = exp(wa);
ewa = t * cos(wb);
ewb = t * sin(wb);
t = (ewa * wa - ewb * wb); q = t + ewa; t -= za;
u = (ewb * wa + ewa * wb); r = u + ewb; u -= zb;
ewa = q * t + r * u; ewb = q * u - r * t;
r = 1.0 / (q * q + r * r);
ewa *= r; ewb *= r;
if ((ewa*ewa + ewb*ewb) < (wa*wa + wb*wb) * 1e-12)
maxk = FLINT_MIN(maxk, k + 2);
wa -= ewa; wb -= ewb;
}
acb_set_d_d(res, wa, wb);
}
int
acb_hypgeom_2f1_choose(const acb_t z)
{
double x, y;
double mag[7];
int i, pick;
x = arf_get_d(arb_midref(acb_realref(z)), ARF_RND_DOWN);
y = arf_get_d(arb_midref(acb_imagref(z)), ARF_RND_DOWN);
x = FLINT_MAX(FLINT_MIN(x, 1e10), -1e10);
y = FLINT_MAX(FLINT_MIN(y, 1e10), -1e10);
mag[0] = x*x + y*y; /* |z|^2 */
mag[4] = (1.0-x)*(1.0-x) + y*y; /* |1-z|^2 */
if (mag[0] <= ALWAYS1) return 0;
mag[1] = mag[0] / FLINT_MAX(mag[4], 1e-10); /* |z/(z-1)|^2 */
if (mag[1] <= ALWAYS1) return 1;
if (mag[0] <= ALWAYS2 || mag[1] <= ALWAYS2)
return mag[0] <= mag[1] ? 0 : 1;
mag[2] = 1.0 / mag[0]; /* |1/z|^2 */
mag[3] = 1.0 / FLINT_MAX(mag[4], 1e-10); /* 1/|1-z|^2 */
mag[5] = mag[4] / mag[0]; /* |1-1/z|^2 = |(1-z)/z|^2 */
pick = 0;
for (i = 1; i < 6; i++)
{
if (mag[i] < mag[pick])
pick = i;
}
if (mag[pick] <= LIMIT)
return pick;
return 6;
}
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;
}
renf_elem_class::operator double() const noexcept
{
if (nf == nullptr)
{
arb_t s;
arb_init(s);
arb_set_fmpq(s, b, 128);
double ans = arf_get_d(arb_midref(s), ARF_RND_NEAR);
arb_clear(s);
return ans;
}
else
return renf_elem_get_d(a, nf->renf_t(), ARF_RND_NEAR);
}
/* this can be improved */
static int
use_recurrence(const acb_t n, const acb_t a, const acb_t b, slong prec)
{
if (!acb_is_int(n) || !arb_is_nonnegative(acb_realref(n)))
return 0;
if (arf_cmpabs_ui(arb_midref(acb_realref(n)), prec) > 0)
return 0;
if (arb_is_nonnegative(acb_realref(a)) ||
arf_get_d(arb_midref(acb_realref(a)), ARF_RND_DOWN) > -0.9)
return 0;
return 1;
}
void arb_mat_print_sage_float(const arb_mat_t A) {
int nrows = arb_mat_nrows(A);
int ncols = arb_mat_ncols(A);
printf("[");
for(int j = 0; j < nrows; j++) {
printf("[");
for(int k = 0; k < ncols; k++) {
double x = arf_get_d(arb_midref(arb_mat_entry(A, j, k)), ARF_RND_NEAR);
printf("%e", x);
if(k < nrows - 1)
printf(", ");
}
printf("],\n");
}
printf("]\n");
}
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_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
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));
}
}
double Lib_Arb_Get_D(ArbPtr x)
{
return arf_get_d( arb_midref((arb_ptr) x), ARF_RND_DOWN);
}
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);
}
int main()
{
slong iter;
flint_rand_t state;
flint_printf("get_d....");
fflush(stdout);
flint_randinit(state);
/* test exact roundtrip */
for (iter = 0; iter < 100000 * arb_test_multiplier(); iter++)
{
arf_t x, z;
double y;
arf_rnd_t rnd;
arf_init(x);
arf_init(z);
switch (n_randint(state, 4))
{
case 0: rnd = ARF_RND_DOWN; break;
case 1: rnd = ARF_RND_UP; break;
case 2: rnd = ARF_RND_FLOOR; break;
case 3: rnd = ARF_RND_CEIL; break;
default: rnd = ARF_RND_NEAR; break;
}
arf_randtest_special(x, state, 53, 8);
y = arf_get_d(x, rnd);
arf_set_d(z, y);
if (!arf_equal(x, z))
{
flint_printf("FAIL:\n\n");
flint_printf("x = "); arf_print(x); flint_printf("\n\n");
flint_printf("y = %.17g\n\n", y);
flint_printf("z = "); arf_print(z); flint_printf("\n\n");
abort();
}
arf_clear(x);
arf_clear(z);
}
/* test rounding */
for (iter = 0; iter < 100000 * arb_test_multiplier(); iter++)
{
arf_t x, z, w;
arf_rnd_t rnd;
double y;
arf_init(x);
arf_init(z);
arf_init(w);
arf_randtest_special(x, state, 300, 8);
switch (n_randint(state, 4))
{
case 0: rnd = ARF_RND_DOWN; break;
case 1: rnd = ARF_RND_UP; break;
case 2: rnd = ARF_RND_FLOOR; break;
default: rnd = ARF_RND_CEIL; break;
}
y = arf_get_d(x, rnd);
arf_set_d(w, y);
arf_set_round(z, x, 53, rnd);
if (!arf_equal(w, z))
{
flint_printf("FAIL:\n\n");
flint_printf("x = "); arf_print(x); flint_printf("\n\n");
flint_printf("y = %.17g\n\n", y);
flint_printf("z = "); arf_print(z); flint_printf("\n\n");
flint_printf("w = "); arf_print(w); flint_printf("\n\n");
abort();
}
arf_clear(x);
arf_clear(z);
arf_clear(w);
}
/* compare with mpfr */
for (iter = 0; iter < 100000 * arb_test_multiplier(); iter++)
{
arf_t x, r1, r2;
arf_rnd_t rnd;
mpfr_t t;
double d1, d2;
arf_init(x);
arf_init(r1);
arf_init(r2);
mpfr_init2(t, 300);
arf_randtest_special(x, state, 300, 20);
arf_get_mpfr(t, x, MPFR_RNDD);
switch (n_randint(state, 4))
{
case 0: rnd = ARF_RND_DOWN; break;
case 1: rnd = ARF_RND_UP; break;
case 2: rnd = ARF_RND_FLOOR; break;
case 3: rnd = ARF_RND_CEIL; break;
default: rnd = ARF_RND_NEAR; break;
}
d1 = arf_get_d(x, rnd);
d2 = mpfr_get_d(t, rnd_to_mpfr(rnd));
arf_set_d(r1, d1);
arf_set_d(r2, d2);
if (!arf_equal(r1, r2))
{
flint_printf("FAIL:\n\n");
flint_printf("rnd = %i\n\n", rnd);
flint_printf("x = "); arf_print(x); flint_printf("\n\n");
flint_printf("d1 = %.17g\n\n", d1);
flint_printf("d2 = %.17g\n\n", d2);
flint_printf("r1 = "); arf_print(r1); flint_printf("\n\n");
flint_printf("r2 = "); arf_print(r2); flint_printf("\n\n");
abort();
}
arf_clear(x);
arf_clear(r1);
arf_clear(r2);
mpfr_clear(t);
}
flint_randclear(state);
flint_cleanup();
flint_printf("PASS\n");
return EXIT_SUCCESS;
}
int
acb_calc_integrate_taylor(acb_t res,
acb_calc_func_t func, void * param,
const acb_t a, const acb_t b,
const arf_t inner_radius,
const arf_t outer_radius,
long accuracy_goal, long prec)
{
long num_steps, step, N, bp;
int result;
acb_t delta, m, x, y1, y2, sum;
acb_ptr taylor_poly;
arf_t err;
acb_init(delta);
acb_init(m);
acb_init(x);
acb_init(y1);
acb_init(y2);
acb_init(sum);
arf_init(err);
acb_sub(delta, b, a, prec);
/* precision used for bounds calculations */
bp = MAG_BITS;
/* compute the number of steps */
{
arf_t t;
arf_init(t);
acb_get_abs_ubound_arf(t, delta, bp);
arf_div(t, t, inner_radius, bp, ARF_RND_UP);
arf_mul_2exp_si(t, t, -1);
num_steps = (long) (arf_get_d(t, ARF_RND_UP) + 1.0);
/* make sure it's not something absurd */
num_steps = FLINT_MIN(num_steps, 10 * prec);
num_steps = FLINT_MAX(num_steps, 1);
arf_clear(t);
}
result = ARB_CALC_SUCCESS;
acb_zero(sum);
for (step = 0; step < num_steps; step++)
{
/* midpoint of subinterval */
acb_mul_ui(m, delta, 2 * step + 1, prec);
acb_div_ui(m, m, 2 * num_steps, prec);
acb_add(m, m, a, prec);
if (arb_calc_verbose)
{
printf("integration point %ld/%ld: ", 2 * step + 1, 2 * num_steps);
acb_printd(m, 15); printf("\n");
}
/* evaluate at +/- x */
/* TODO: exactify m, and include error in x? */
acb_div_ui(x, delta, 2 * num_steps, prec);
/* compute bounds and number of terms to use */
{
arb_t cbound, xbound, rbound;
arf_t C, D, R, X, T;
double DD, TT, NN;
arb_init(cbound);
arb_init(xbound);
arb_init(rbound);
arf_init(C);
arf_init(D);
arf_init(R);
arf_init(X);
arf_init(T);
/* R is the outer radius */
arf_set(R, outer_radius);
/* X = upper bound for |x| */
acb_get_abs_ubound_arf(X, x, bp);
arb_set_arf(xbound, X);
/* Compute C(m,R). Important subtlety: due to rounding when
computing m, we will in general be farther than R away from
the integration path. But since acb_calc_cauchy_bound
actually integrates over the area traced by a complex
interval, it will catch any extra singularities (giving
an infinite bound). */
arb_set_arf(rbound, outer_radius);
acb_calc_cauchy_bound(cbound, func, param, m, rbound, 8, bp);
arf_set_mag(C, arb_radref(cbound));
arf_add(C, arb_midref(cbound), C, bp, ARF_RND_UP);
/* Sanity check: we need C < inf and R > X */
if (arf_is_finite(C) && arf_cmp(R, X) > 0)
{
/* Compute upper bound for D = C * R * X / (R - X) */
arf_mul(D, C, R, bp, ARF_RND_UP);
arf_mul(D, D, X, bp, ARF_RND_UP);
arf_sub(T, R, X, bp, ARF_RND_DOWN);
arf_div(D, D, T, bp, ARF_RND_UP);
/* Compute upper bound for T = (X / R) */
arf_div(T, X, R, bp, ARF_RND_UP);
/* Choose N */
/* TODO: use arf arithmetic to avoid overflow */
/* TODO: use relative accuracy (look at |f(m)|?) */
DD = arf_get_d(D, ARF_RND_UP);
TT = arf_get_d(T, ARF_RND_UP);
NN = -(accuracy_goal * 0.69314718055994530942 + log(DD)) / log(TT);
N = NN + 0.5;
N = FLINT_MIN(N, 100 * prec);
N = FLINT_MAX(N, 1);
/* Tail bound: D / (N + 1) * T^N */
{
mag_t TT;
mag_init(TT);
arf_get_mag(TT, T);
mag_pow_ui(TT, TT, N);
arf_set_mag(T, TT);
mag_clear(TT);
}
arf_mul(D, D, T, bp, ARF_RND_UP);
arf_div_ui(err, D, N + 1, bp, ARF_RND_UP);
}
else
{
N = 1;
arf_pos_inf(err);
result = ARB_CALC_NO_CONVERGENCE;
}
if (arb_calc_verbose)
{
printf("N = %ld; bound: ", N); arf_printd(err, 15); printf("\n");
printf("R: "); arf_printd(R, 15); printf("\n");
printf("C: "); arf_printd(C, 15); printf("\n");
printf("X: "); arf_printd(X, 15); printf("\n");
}
arb_clear(cbound);
arb_clear(xbound);
arb_clear(rbound);
arf_clear(C);
arf_clear(D);
arf_clear(R);
arf_clear(X);
arf_clear(T);
}
/* evaluate Taylor polynomial */
taylor_poly = _acb_vec_init(N + 1);
func(taylor_poly, m, param, N, prec);
_acb_poly_integral(taylor_poly, taylor_poly, N + 1, prec);
_acb_poly_evaluate(y2, taylor_poly, N + 1, x, prec);
acb_neg(x, x);
_acb_poly_evaluate(y1, taylor_poly, N + 1, x, prec);
acb_neg(x, x);
/* add truncation error */
arb_add_error_arf(acb_realref(y1), err);
arb_add_error_arf(acb_imagref(y1), err);
arb_add_error_arf(acb_realref(y2), err);
arb_add_error_arf(acb_imagref(y2), err);
acb_add(sum, sum, y2, prec);
acb_sub(sum, sum, y1, prec);
if (arb_calc_verbose)
{
printf("values: ");
acb_printd(y1, 15); printf(" ");
acb_printd(y2, 15); printf("\n");
}
_acb_vec_clear(taylor_poly, N + 1);
if (result == ARB_CALC_NO_CONVERGENCE)
break;
}
acb_set(res, sum);
acb_clear(delta);
acb_clear(m);
acb_clear(x);
acb_clear(y1);
acb_clear(y2);
acb_clear(sum);
arf_clear(err);
return result;
}
