コード例 #1
0
ファイル: addmul.c プロジェクト: argriffing/arb
void
arb_addmul_arf(arb_t z, const arb_t x, const arf_t y, slong prec)
{
    mag_t ym;
    int inexact;

    if (arb_is_exact(x))
    {
        inexact = arf_addmul(arb_midref(z), arb_midref(x), y, prec, ARB_RND);

        if (inexact)
            arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);
    }
    else if (ARB_IS_LAGOM(x) && ARF_IS_LAGOM(y) && ARB_IS_LAGOM(z))
    {
        mag_fast_init_set_arf(ym, y);
        mag_fast_addmul(arb_radref(z), ym, arb_radref(x));
        inexact = arf_addmul(arb_midref(z), arb_midref(x), y, prec, ARB_RND);

        if (inexact)
            arf_mag_fast_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);
    }
    else
    {
        mag_init_set_arf(ym, y);
        mag_addmul(arb_radref(z), ym, arb_radref(x));

        inexact = arf_addmul(arb_midref(z), arb_midref(x), y, prec, ARB_RND);
        if (inexact)
            arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);

        mag_clear(ym);
    }
}
コード例 #2
0
ファイル: inv.c プロジェクト: fredrik-johansson/arb
static void
_arb_arf_div_rounded_den_add_err(arb_t res, const arf_t x, const arf_t y, int yinexact, slong prec)
{
    int inexact = arf_div(arb_midref(res), x, y, prec, ARB_RND);

    if (yinexact && !arf_is_special(arb_midref(res)))
        arf_mag_add_ulp(arb_radref(res), arb_radref(res), arb_midref(res), prec - 1);
    else if (inexact)
        arf_mag_add_ulp(arb_radref(res), arb_radref(res), arb_midref(res), prec);
}
コード例 #3
0
ファイル: mul.c プロジェクト: isuruf/arb
static void
_acb_mul_slow(acb_t z, const acb_t x, const acb_t y, slong prec)
{
    int inexact;

    mag_t am, bm, cm, dm, er, fr;

    mag_init_set_arf(am, arb_midref(a));
    mag_init_set_arf(bm, arb_midref(b));
    mag_init_set_arf(cm, arb_midref(c));
    mag_init_set_arf(dm, arb_midref(d));

    mag_init(er);
    mag_init(fr);

    mag_addmul(er, am, cr);
    mag_addmul(er, bm, dr);
    mag_addmul(er, cm, ar);
    mag_addmul(er, dm, br);
    mag_addmul(er, ar, cr);
    mag_addmul(er, br, dr);

    mag_addmul(fr, am, dr);
    mag_addmul(fr, bm, cr);
    mag_addmul(fr, cm, br);
    mag_addmul(fr, dm, ar);
    mag_addmul(fr, br, cr);
    mag_addmul(fr, ar, dr);

    inexact = arf_complex_mul(arb_midref(e), arb_midref(f),
                    arb_midref(a), arb_midref(b),
                    arb_midref(c), arb_midref(d), prec, ARB_RND);

    if (inexact & 1)
        arf_mag_add_ulp(arb_radref(e), er, arb_midref(e), prec);
    else
        mag_swap(arb_radref(e), er);

    if (inexact & 2)
        arf_mag_add_ulp(arb_radref(f), fr, arb_midref(f), prec);
    else
        mag_swap(arb_radref(f), fr);

    mag_clear(am);
    mag_clear(bm);
    mag_clear(cm);
    mag_clear(dm);

    mag_clear(er);
    mag_clear(fr);
}
コード例 #4
0
ファイル: arb_extras.c プロジェクト: jwbober/ntlib
void arb_square(arb_t out, const arb_t in, slong prec) {
    mag_mul(arb_radref(out), arb_radref(in), arb_radref(in));
    int inexact = arf_mul(arb_midref(out), arb_midref(in), arb_midref(in), ARB_RND, prec);
    if (inexact)
        arf_mag_add_ulp(arb_radref(out), arb_radref(out), arb_midref(out), prec);

}
コード例 #5
0
ファイル: set_interval_arf.c プロジェクト: isuruf/arb
void
arb_set_interval_arf(arb_t x, const arf_t a, const arf_t b, slong prec)
{
    arf_t t;
    int inexact;

    if (arf_is_inf(a) && arf_equal(a, b))
    {
        /* [-inf, -inf] or [+inf, +inf] */
        arf_set(arb_midref(x), a);
        mag_zero(arb_radref(x));
        return;
    }

    arf_init(t);
    arf_sub(t, b, a, MAG_BITS, ARF_RND_UP);

    if (arf_sgn(t) < 0)
    {
        flint_printf("exception: arb_set_interval_arf: endpoints not ordered\n");
        abort();
    }

    arf_get_mag(arb_radref(x), t);

    inexact = arf_add(arb_midref(x), a, b, prec, ARB_RND);
    if (inexact)
        arf_mag_add_ulp(arb_radref(x), arb_radref(x), arb_midref(x), prec);

    arb_mul_2exp_si(x, x, -1);

    arf_clear(t);
}
コード例 #6
0
ファイル: mul.c プロジェクト: isuruf/arb
static void
_acb_sqr_slow(acb_t z, const acb_t x, slong prec)
{
    int inexact;

    mag_t am, bm, er, fr;

    mag_init_set_arf(am, arb_midref(a));
    mag_init_set_arf(bm, arb_midref(b));

    mag_init(er);
    mag_init(fr);

    mag_addmul(er, am, ar);
    mag_addmul(er, bm, br);
    mag_mul_2exp_si(er, er, 1);
    mag_addmul(er, ar, ar);
    mag_addmul(er, br, br);

    mag_addmul(fr, bm, ar);
    mag_addmul(fr, am, br);
    mag_addmul(fr, ar, br);
    mag_mul_2exp_si(fr, fr, 1);

    inexact = arf_complex_sqr(arb_midref(e), arb_midref(f),
                    arb_midref(a), arb_midref(b), prec, ARB_RND);

    if (inexact & 1)
        arf_mag_add_ulp(arb_radref(e), er, arb_midref(e), prec);
    else
        mag_swap(arb_radref(e), er);

    if (inexact & 2)
        arf_mag_add_ulp(arb_radref(f), fr, arb_midref(f), prec);
    else
        mag_swap(arb_radref(f), fr);

    mag_clear(am);
    mag_clear(bm);

    mag_clear(er);
    mag_clear(fr);
}
コード例 #7
0
ファイル: sub.c プロジェクト: argriffing/arb
void
arb_sub_fmpz(arb_t z, const arb_t x, const fmpz_t y, slong prec)
{
    int inexact;
    inexact = arf_sub_fmpz(arb_midref(z), arb_midref(x), y, prec, ARB_RND);
    if (inexact)
        arf_mag_add_ulp(arb_radref(z), arb_radref(x), arb_midref(z), prec);
    else
        mag_set(arb_radref(z), arb_radref(x));
}
コード例 #8
0
ファイル: addmul.c プロジェクト: argriffing/arb
void
arb_addmul(arb_t z, const arb_t x, const arb_t y, slong prec)
{
    mag_t zr, xm, ym;
    int inexact;

    if (arb_is_exact(y))
    {
        arb_addmul_arf(z, x, arb_midref(y), prec);
    }
    else if (arb_is_exact(x))
    {
        arb_addmul_arf(z, y, arb_midref(x), prec);
    }
    else if (ARB_IS_LAGOM(x) && ARB_IS_LAGOM(y) && ARB_IS_LAGOM(z))
    {
        mag_fast_init_set_arf(xm, arb_midref(x));
        mag_fast_init_set_arf(ym, arb_midref(y));

        mag_fast_init_set(zr, arb_radref(z));
        mag_fast_addmul(zr, xm, arb_radref(y));
        mag_fast_addmul(zr, ym, arb_radref(x));
        mag_fast_addmul(zr, arb_radref(x), arb_radref(y));

        inexact = arf_addmul(arb_midref(z), arb_midref(x), arb_midref(y),
            prec, ARF_RND_DOWN);

        if (inexact)
            arf_mag_fast_add_ulp(zr, zr, arb_midref(z), prec);

        *arb_radref(z) = *zr;
    }
    else
    {
        mag_init_set_arf(xm, arb_midref(x));
        mag_init_set_arf(ym, arb_midref(y));

        mag_init_set(zr, arb_radref(z));
        mag_addmul(zr, xm, arb_radref(y));
        mag_addmul(zr, ym, arb_radref(x));
        mag_addmul(zr, arb_radref(x), arb_radref(y));

        inexact = arf_addmul(arb_midref(z), arb_midref(x), arb_midref(y),
            prec, ARF_RND_DOWN);

        if (inexact)
            arf_mag_add_ulp(arb_radref(z), zr, arb_midref(z), prec);
        else
            mag_set(arb_radref(z), zr);

        mag_clear(zr);
        mag_clear(xm);
        mag_clear(ym);
    }
}
コード例 #9
0
ファイル: sub.c プロジェクト: argriffing/arb
void
arb_sub(arb_t z, const arb_t x, const arb_t y, slong prec)
{
    int inexact;

    inexact = arf_sub(arb_midref(z), arb_midref(x), arb_midref(y), prec, ARB_RND);

    mag_add(arb_radref(z), arb_radref(x), arb_radref(y));
    if (inexact)
        arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);
}
コード例 #10
0
ファイル: div.c プロジェクト: bluescarni/arb
void
arb_div(arb_t z, const arb_t x, const arb_t y, long prec)
{
    mag_t zr, xm, ym, yl, yw;
    int inexact;

    if (arb_is_exact(y))
    {
        arb_div_arf(z, x, arb_midref(y), prec);
    }
    else if (mag_is_inf(arb_radref(x)) || mag_is_inf(arb_radref(y)))
    {
        arf_div(arb_midref(z), arb_midref(x), arb_midref(y), prec, ARB_RND);
        mag_inf(arb_radref(z));
    }
    else
    {
        mag_init_set_arf(xm, arb_midref(x));
        mag_init_set_arf(ym, arb_midref(y));
        mag_init(zr);
        mag_init(yl);
        mag_init(yw);

        /* (|x|*yrad + |y|*xrad)/(y*(|y|-yrad)) */
        mag_mul(zr, xm, arb_radref(y));
        mag_addmul(zr, ym, arb_radref(x));
        arb_get_mag_lower(yw, y);

        arf_get_mag_lower(yl, arb_midref(y));
        mag_mul_lower(yl, yl, yw);

        mag_div(zr, zr, yl);

        inexact = arf_div(arb_midref(z), arb_midref(x), arb_midref(y), prec, ARB_RND);

        if (inexact)
            arf_mag_add_ulp(arb_radref(z), zr, arb_midref(z), prec);
        else
            mag_swap(arb_radref(z), zr);

        mag_clear(xm);
        mag_clear(ym);
        mag_clear(zr);
        mag_clear(yl);
        mag_clear(yw);
    }
}
コード例 #11
0
ファイル: div.c プロジェクト: bluescarni/arb
void
arb_div_arf(arb_t z, const arb_t x, const arf_t y, long prec)
{
    mag_t zr, ym;
    int inexact;

    if (arf_is_zero(y))
    {
        arb_zero_pm_inf(z);
    }
    else if (arb_is_exact(x))
    {
        inexact = arf_div(arb_midref(z), arb_midref(x), y, prec, ARB_RND);

        if (inexact)
            arf_mag_set_ulp(arb_radref(z), arb_midref(z), prec);
        else
            mag_zero(arb_radref(z));
    }
    else if (mag_is_inf(arb_radref(x)))
    {
        arf_div(arb_midref(z), arb_midref(x), y, prec, ARB_RND);
        mag_inf(arb_radref(z));
    }
    else
    {
        mag_init(ym);
        mag_init(zr);

        arf_get_mag_lower(ym, y);
        mag_div(zr, arb_radref(x), ym);

        inexact = arf_div(arb_midref(z), arb_midref(x), y, prec, ARB_RND);

        if (inexact)
            arf_mag_add_ulp(arb_radref(z), zr, arb_midref(z), prec);
        else
            mag_swap(arb_radref(z), zr);

        mag_clear(ym);
        mag_clear(zr);
    }
}
コード例 #12
0
ファイル: atan.c プロジェクト: argriffing/arb
void
arb_atan_arf(arb_t z, const arf_t x, slong prec)
{
    if (arf_is_special(x))
    {
        if (arf_is_zero(x))
        {
            arb_zero(z);
        }
        else if (arf_is_pos_inf(x))
        {
            arb_const_pi(z, prec);
            arb_mul_2exp_si(z, z, -1);
        }
        else if (arf_is_neg_inf(x))
        {
            arb_const_pi(z, prec);
            arb_mul_2exp_si(z, z, -1);
            arb_neg(z, z);
        }
        else
        {
            arb_indeterminate(z);
        }
    }
    else if (COEFF_IS_MPZ(*ARF_EXPREF(x)))
    {
        if (fmpz_sgn(ARF_EXPREF(x)) < 0)
            arb_atan_eps(z, x, prec);
        else
            arb_atan_inf_eps(z, x, prec);
    }
    else
    {
        slong exp, wp, wn, N, r;
        mp_srcptr xp;
        mp_size_t xn, tn;
        mp_ptr tmp, w, t, u;
        mp_limb_t p1, q1bits, p2, q2bits, error, error2;
        int negative, inexact, reciprocal;
        TMP_INIT;

        exp = ARF_EXP(x);
        negative = ARF_SGNBIT(x);

        if (exp < -(prec/2) - 2 || exp > prec + 2)
        {
            if (exp < 0)
                arb_atan_eps(z, x, prec);
            else
                arb_atan_inf_eps(z, x, prec);
            return;
        }

        ARF_GET_MPN_READONLY(xp, xn, x);

        /* Special case: +/- 1 (we require |x| != 1 later on) */
        if (exp == 1 && xn == 1 && xp[xn-1] == LIMB_TOP)
        {
            arb_const_pi(z, prec);
            arb_mul_2exp_si(z, z, -2);
            if (negative)
                arb_neg(z, z);
            return;
        }

        /* Absolute working precision (NOT rounded to a limb multiple) */
        wp = prec - FLINT_MIN(0, exp) + 4;

        /* Too high precision to use table */
        if (wp > ARB_ATAN_TAB2_PREC)
        {
            arb_atan_arf_bb(z, x, prec);
            return;
        }

        /* Working precision in limbs */
        wn = (wp + FLINT_BITS - 1) / FLINT_BITS;

        TMP_START;

        tmp = TMP_ALLOC_LIMBS(4 * wn + 3);
        w = tmp;        /* requires wn+1 limbs */
        t = w + wn + 1; /* requires wn+1 limbs */
        u = t + wn + 1; /* requires 2wn+1 limbs */

        /* ----------------------------------------------------------------- */
        /* Convert x or 1/x to a fixed-point number |w| < 1                  */
        /* ----------------------------------------------------------------- */

        if (exp <= 0)  /* |x| < 1 */
        {
            reciprocal = 0;

            /* todo: just zero top */
            flint_mpn_zero(w, wn);

            /* w = x as a fixed-point number */
            error = _arf_get_integer_mpn(w, xp, xn, exp + wn * FLINT_BITS);
        }
        else    /* |x| > 1 */
        {
            slong one_exp, one_limbs, one_bits;
            mp_ptr one;

            reciprocal = 1;

            one_exp = xn * FLINT_BITS + wn * FLINT_BITS - exp;

            flint_mpn_zero(w, wn);

            /* 1/x becomes zero */
            if (one_exp >= FLINT_BITS - 1)
            {
                /* w = 1/x */
                one_limbs = one_exp / FLINT_BITS;
                one_bits = one_exp % FLINT_BITS;

                if (one_limbs + 1 >= xn)
                {
                    one = TMP_ALLOC_LIMBS(one_limbs + 1);
                    flint_mpn_zero(one, one_limbs);
                    one[one_limbs] = UWORD(1) << one_bits;

                    /* todo: only zero necessary part */
                    flint_mpn_zero(w, wn);
                    mpn_tdiv_q(w, one, one_limbs + 1, xp, xn);

                    /* Now w must be < 1 since x > 1 and we rounded down; thus
                       w[wn] must be zero */
                }
            }

            /* todo: moderate powers of two would be exact... */
            error = 1;
        }

        /* ----------------------------------------------------------------- */
        /* Table-based argument reduction                                    */
        /* ----------------------------------------------------------------- */

        /* choose p such that p/q <= x < (p+1)/q */
        if (wp <= ARB_ATAN_TAB1_PREC)
            q1bits = ARB_ATAN_TAB1_BITS;
        else
            q1bits = ARB_ATAN_TAB21_BITS;

        p1 = w[wn-1] >> (FLINT_BITS - q1bits);

        /* atan(w) = atan(p/q) + atan(w2) */
        /* where w2 = (q*w-p)/(q+p*w) */
        if (p1 != 0)
        {
            t[wn] = (UWORD(1) << q1bits) + mpn_mul_1(t, w, wn, p1);
            flint_mpn_zero(u, wn);
            u[2 * wn] = mpn_lshift(u + wn, w, wn, q1bits) - p1;
            mpn_tdiv_q(w, u, 2 * wn + 1, t, wn + 1);
            error++;  /* w2 is computed with 1 ulp error */
        }

        /* Do a second round of argument reduction */
        if (wp <= ARB_ATAN_TAB1_PREC)
        {
            p2 = 0;
        }
        else
        {
            q2bits = ARB_ATAN_TAB21_BITS + ARB_ATAN_TAB22_BITS;
            p2 = w[wn-1] >> (FLINT_BITS - q2bits);

            if (p2 != 0)
            {
                t[wn] = (UWORD(1) << q2bits) + mpn_mul_1(t, w, wn, p2);
                flint_mpn_zero(u, wn);
                u[2 * wn] = mpn_lshift(u + wn, w, wn, q2bits) - p2;
                mpn_tdiv_q(w, u, 2 * wn + 1, t, wn + 1);
                error++;
            }
        }

        /* |w| <= 2^-r */
        r = _arb_mpn_leading_zeros(w, wn);

        /* N >= (wp-r)/(2r) */
        N = (wp - r + (2*r-1)) / (2*r);

        /* Evaluate Taylor series */
        _arb_atan_taylor_rs(t, &error2, w, wn, N, 1);

        /* Taylor series evaluation error */
        error += error2;

        /* Size of output number */
        tn = wn;

        /* First table lookup */
        if (p1 != 0)
        {
            if (wp <= ARB_ATAN_TAB1_PREC)
                mpn_add_n(t, t, arb_atan_tab1[p1] + ARB_ATAN_TAB1_LIMBS - tn, tn);
            else
                mpn_add_n(t, t, arb_atan_tab21[p1] + ARB_ATAN_TAB2_LIMBS - tn, tn);
            error++;
        }

        /* Second table lookup */
        if (p2 != 0)
        {
            mpn_add_n(t, t, arb_atan_tab22[p2] + ARB_ATAN_TAB2_LIMBS - tn, tn);
            error++;
        }

        /* pi/2 - atan(1/x) */
        if (reciprocal)
        {
            t[tn] = LIMB_ONE - mpn_sub_n(t,
                arb_atan_pi2_minus_one + ARB_ATAN_TAB2_LIMBS - tn, t, tn);

            /* result can be >= 1 */
            tn += (t[tn] != 0);

            /* error of pi/2 */
            error++;
        }

        /* The accumulated arithmetic error */
        mag_set_ui_2exp_si(arb_radref(z), error, -wn * FLINT_BITS);

        /* Truncation error from the Taylor series */
        mag_add_ui_2exp_si(arb_radref(z), arb_radref(z), 1, -r*(2*N+1));

        /* Set the midpoint */
        inexact = _arf_set_mpn_fixed(arb_midref(z), t, tn, wn, negative, prec, ARB_RND);
        if (inexact)
            arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);

        TMP_END;
    }
}
コード例 #13
0
ファイル: log.c プロジェクト: isuruf/arb
void
arb_log_arf(arb_t z, const arf_t x, slong prec)
{
    if (arf_is_special(x))
    {
        if (arf_is_pos_inf(x))
            arb_pos_inf(z);
        else
            arb_indeterminate(z);
    }
    else if (ARF_SGNBIT(x))
    {
        arb_indeterminate(z);
    }
    else if (ARF_IS_POW2(x))
    {
        if (fmpz_is_one(ARF_EXPREF(x)))
        {
            arb_zero(z);
        }
        else
        {
            fmpz_t exp;
            fmpz_init(exp);
            _fmpz_add_fast(exp, ARF_EXPREF(x), -1);
            arb_const_log2(z, prec + 2);
            arb_mul_fmpz(z, z, exp, prec);
            fmpz_clear(exp);
        }
    }
    else if (COEFF_IS_MPZ(*ARF_EXPREF(x)))
    {
        arb_log_arf_huge(z, x, prec);
    }
    else
    {
        slong exp, wp, wn, N, r, closeness_to_one;
        mp_srcptr xp;
        mp_size_t xn, tn;
        mp_ptr tmp, w, t, u;
        mp_limb_t p1, q1bits, p2, q2bits, error, error2, cy;
        int negative, inexact, used_taylor_series;
        TMP_INIT;

        exp = ARF_EXP(x);
        negative = 0;

        ARF_GET_MPN_READONLY(xp, xn, x);

        /* compute a c >= 0 such that |x-1| <= 2^(-c) if c > 0 */
        closeness_to_one = 0;

        if (exp == 0)
        {
            slong i;

            closeness_to_one = FLINT_BITS - FLINT_BIT_COUNT(~xp[xn - 1]);

            if (closeness_to_one == FLINT_BITS)
            {
                for (i = xn - 2; i > 0 && xp[i] == LIMB_ONES; i--)
                    closeness_to_one += FLINT_BITS;

                closeness_to_one += (FLINT_BITS - FLINT_BIT_COUNT(~xp[i]));
            }
        }
        else if (exp == 1)
        {
            closeness_to_one = FLINT_BITS - FLINT_BIT_COUNT(xp[xn - 1] & (~LIMB_TOP));

            if (closeness_to_one == FLINT_BITS)
            {
                slong i;

                for (i = xn - 2; xp[i] == 0; i--)
                    closeness_to_one += FLINT_BITS;

                closeness_to_one += (FLINT_BITS - FLINT_BIT_COUNT(xp[i]));
            }

            closeness_to_one--;
        }

        /* if |t-1| <= 0.5               */
        /* |log(1+t) - t| <= t^2         */
        /* |log(1+t) - (t-t^2/2)| <= t^3 */
        if (closeness_to_one > prec + 1)
        {
            inexact = arf_sub_ui(arb_midref(z), x, 1, prec, ARB_RND);
            mag_set_ui_2exp_si(arb_radref(z), 1, -2 * closeness_to_one);
            if (inexact)
                arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);
            return;
        }
        else if (2 * closeness_to_one > prec + 1)
        {
            arf_t t, u;
            arf_init(t);
            arf_init(u);
            arf_sub_ui(t, x, 1, ARF_PREC_EXACT, ARF_RND_DOWN);
            arf_mul(u, t, t, ARF_PREC_EXACT, ARF_RND_DOWN);
            arf_mul_2exp_si(u, u, -1);
            inexact = arf_sub(arb_midref(z), t, u, prec, ARB_RND);
            mag_set_ui_2exp_si(arb_radref(z), 1, -3 * closeness_to_one);
            if (inexact)
                arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);
            arf_clear(t);
            arf_clear(u);
            return;
        }

        /* Absolute working precision (NOT rounded to a limb multiple) */
        wp = prec + closeness_to_one + 5;

        /* Too high precision to use table */
        if (wp > ARB_LOG_TAB2_PREC)
        {
            arf_log_via_mpfr(arb_midref(z), x, prec, ARB_RND);
            arf_mag_set_ulp(arb_radref(z), arb_midref(z), prec);
            return;
        }

        /* Working precision in limbs */
        wn = (wp + FLINT_BITS - 1) / FLINT_BITS;

        TMP_START;

        tmp = TMP_ALLOC_LIMBS(4 * wn + 3);
        w = tmp;        /* requires wn+1 limbs */
        t = w + wn + 1; /* requires wn+1 limbs */
        u = t + wn + 1; /* requires 2wn+1 limbs */

        /* read x-1 */
        if (xn <= wn)
        {
            flint_mpn_zero(w, wn - xn);
            mpn_lshift(w + wn - xn, xp, xn, 1);
            error = 0;
        }
        else
        {
            mpn_lshift(w, xp + xn - wn, wn, 1);
            error = 1;
        }

        /* First table-based argument reduction */
        if (wp <= ARB_LOG_TAB1_PREC)
            q1bits = ARB_LOG_TAB11_BITS;
        else
            q1bits = ARB_LOG_TAB21_BITS;

        p1 = w[wn-1] >> (FLINT_BITS - q1bits);

        /* Special case: covers logarithms of small integers */
        if (xn == 1 && (w[wn-1] == (p1 << (FLINT_BITS - q1bits))))
        {
            p2 = 0;
            flint_mpn_zero(t, wn);
            used_taylor_series = 0;
            N = r = 0; /* silence compiler warning */
        }
        else
        {
            /* log(1+w) = log(1+p/q) + log(1 + (qw-p)/(p+q)) */
            w[wn] = mpn_mul_1(w, w, wn, UWORD(1) << q1bits) - p1;
            mpn_divrem_1(w, 0, w, wn + 1, p1 + (UWORD(1) << q1bits));
            error += 1;

            /* Second table-based argument reduction (fused with log->atanh
               conversion) */
            if (wp <= ARB_LOG_TAB1_PREC)
                q2bits = ARB_LOG_TAB11_BITS + ARB_LOG_TAB12_BITS;
            else
                q2bits = ARB_LOG_TAB21_BITS + ARB_LOG_TAB22_BITS;

            p2 = w[wn-1] >> (FLINT_BITS - q2bits);

            u[2 * wn] = mpn_lshift(u + wn, w, wn, q2bits);
            flint_mpn_zero(u, wn);
            flint_mpn_copyi(t, u + wn, wn + 1);
            t[wn] += p2 + (UWORD(1) << (q2bits + 1));
            u[2 * wn] -= p2;
            mpn_tdiv_q(w, u, 2 * wn + 1, t, wn + 1);

            /* propagated error from 1 ulp error: 2 atanh'(1/3) = 2.25 */
            error += 3;

            /* |w| <= 2^-r */
            r = _arb_mpn_leading_zeros(w, wn);

            /* N >= (wp-r)/(2r) */
            N = (wp - r + (2*r-1)) / (2*r);
            N = FLINT_MAX(N, 0);

            /* Evaluate Taylor series */
            _arb_atan_taylor_rs(t, &error2, w, wn, N, 0);
            /* Multiply by 2 */
            mpn_lshift(t, t, wn, 1);
            /* Taylor series evaluation error (multiply by 2) */
            error += error2 * 2;

            used_taylor_series = 1;
        }

        /* Size of output number */
        tn = wn;

        /* First table lookup */
        if (p1 != 0)
        {
            if (wp <= ARB_LOG_TAB1_PREC)
                mpn_add_n(t, t, arb_log_tab11[p1] + ARB_LOG_TAB1_LIMBS - tn, tn);
            else
                mpn_add_n(t, t, arb_log_tab21[p1] + ARB_LOG_TAB2_LIMBS - tn, tn);
            error++;
        }

        /* Second table lookup */
        if (p2 != 0)
        {
            if (wp <= ARB_LOG_TAB1_PREC)
                mpn_add_n(t, t, arb_log_tab12[p2] + ARB_LOG_TAB1_LIMBS - tn, tn);
            else
                mpn_add_n(t, t, arb_log_tab22[p2] + ARB_LOG_TAB2_LIMBS - tn, tn);
            error++;
        }

        /* add exp * log(2) */
        exp--;

        if (exp > 0)
        {
            cy = mpn_addmul_1(t, arb_log_log2_tab + ARB_LOG_TAB2_LIMBS - tn, tn, exp);
            t[tn] = cy;
            tn += (cy != 0);
            error += exp;
        }
        else if (exp < 0)
        {
            t[tn] = 0;
            u[tn] = mpn_mul_1(u, arb_log_log2_tab + ARB_LOG_TAB2_LIMBS - tn, tn, -exp);

            if (mpn_cmp(t, u, tn + 1) >= 0)
            {
                mpn_sub_n(t, t, u, tn + 1);
            }
            else
            {
                mpn_sub_n(t, u, t, tn + 1);
                negative = 1;
            }

            error += (-exp);

            tn += (t[tn] != 0);
        }

        /* The accumulated arithmetic error */
        mag_set_ui_2exp_si(arb_radref(z), error, -wn * FLINT_BITS);

        /* Truncation error from the Taylor series */
        if (used_taylor_series)
            mag_add_ui_2exp_si(arb_radref(z), arb_radref(z), 1, -r*(2*N+1) + 1);

        /* Set the midpoint */
        inexact = _arf_set_mpn_fixed(arb_midref(z), t, tn, wn, negative, prec);
        if (inexact)
            arf_mag_add_ulp(arb_radref(z), arb_radref(z), arb_midref(z), prec);

        TMP_END;
    }
}