int
mpc_atan (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
{
int s_re;
int s_im;
int inex_re;
int inex_im;
int inex;
inex_re = 0;
inex_im = 0;
s_re = mpfr_signbit (mpc_realref (op));
s_im = mpfr_signbit (mpc_imagref (op));
/* special values */
if (mpfr_nan_p (mpc_realref (op)) || mpfr_nan_p (mpc_imagref (op)))
{
if (mpfr_nan_p (mpc_realref (op)))
{
mpfr_set_nan (mpc_realref (rop));
if (mpfr_zero_p (mpc_imagref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
mpfr_set_ui (mpc_imagref (rop), 0, GMP_RNDN);
if (s_im)
mpc_conj (rop, rop, MPC_RNDNN);
}
else
mpfr_set_nan (mpc_imagref (rop));
}
else
{
if (mpfr_inf_p (mpc_realref (op)))
{
inex_re = set_pi_over_2 (mpc_realref (rop), -s_re, MPC_RND_RE (rnd));
mpfr_set_ui (mpc_imagref (rop), 0, GMP_RNDN);
}
else
{
mpfr_set_nan (mpc_realref (rop));
mpfr_set_nan (mpc_imagref (rop));
}
}
return MPC_INEX (inex_re, 0);
}
if (mpfr_inf_p (mpc_realref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
inex_re = set_pi_over_2 (mpc_realref (rop), -s_re, MPC_RND_RE (rnd));
mpfr_set_ui (mpc_imagref (rop), 0, GMP_RNDN);
if (s_im)
mpc_conj (rop, rop, GMP_RNDN);
return MPC_INEX (inex_re, 0);
}
/* pure real argument */
if (mpfr_zero_p (mpc_imagref (op)))
{
inex_re = mpfr_atan (mpc_realref (rop), mpc_realref (op), MPC_RND_RE (rnd));
mpfr_set_ui (mpc_imagref (rop), 0, GMP_RNDN);
if (s_im)
mpc_conj (rop, rop, GMP_RNDN);
return MPC_INEX (inex_re, 0);
}
/* pure imaginary argument */
if (mpfr_zero_p (mpc_realref (op)))
{
int cmp_1;
if (s_im)
cmp_1 = -mpfr_cmp_si (mpc_imagref (op), -1);
else
cmp_1 = mpfr_cmp_ui (mpc_imagref (op), +1);
if (cmp_1 < 0)
{
/* atan(+0+iy) = +0 +i*atanh(y), if |y| < 1
atan(-0+iy) = -0 +i*atanh(y), if |y| < 1 */
mpfr_set_ui (mpc_realref (rop), 0, GMP_RNDN);
if (s_re)
mpfr_neg (mpc_realref (rop), mpc_realref (rop), GMP_RNDN);
inex_im = mpfr_atanh (mpc_imagref (rop), mpc_imagref (op), MPC_RND_IM (rnd));
}
else if (cmp_1 == 0)
{
/* atan(+/-0+i) = NaN +i*inf
atan(+/-0-i) = NaN -i*inf */
mpfr_set_nan (mpc_realref (rop));
mpfr_set_inf (mpc_imagref (rop), s_im ? -1 : +1);
}
else
{
/* atan(+0+iy) = +pi/2 +i*atanh(1/y), if |y| > 1
atan(-0+iy) = -pi/2 +i*atanh(1/y), if |y| > 1 */
mpfr_rnd_t rnd_im, rnd_away;
mpfr_t y;
mpfr_prec_t p, p_im;
int ok;
rnd_im = MPC_RND_IM (rnd);
mpfr_init (y);
p_im = mpfr_get_prec (mpc_imagref (rop));
p = p_im;
/* a = o(1/y) with error(a) < 1 ulp(a)
b = o(atanh(a)) with error(b) < (1+2^{1+Exp(a)-Exp(b)}) ulp(b)
As |atanh (1/y)| > |1/y| we have Exp(a)-Exp(b) <=0 so, at most,
2 bits of precision are lost.
We round atanh(1/y) away from 0.
*/
do
{
p += mpc_ceil_log2 (p) + 2;
mpfr_set_prec (y, p);
rnd_away = s_im == 0 ? GMP_RNDU : GMP_RNDD;
inex_im = mpfr_ui_div (y, 1, mpc_imagref (op), rnd_away);
/* FIXME: should we consider the case with unreasonably huge
precision prec(y)>3*exp_min, where atanh(1/Im(op)) could be
representable while 1/Im(op) underflows ?
This corresponds to |y| = 0.5*2^emin, in which case the
result may be wrong. */
/* atanh cannot underflow: |atanh(x)| > |x| for |x| < 1 */
inex_im |= mpfr_atanh (y, y, rnd_away);
ok = inex_im == 0
|| mpfr_can_round (y, p - 2, rnd_away, GMP_RNDZ,
p_im + (rnd_im == GMP_RNDN));
} while (ok == 0);
inex_re = set_pi_over_2 (mpc_realref (rop), -s_re, MPC_RND_RE (rnd));
inex_im = mpfr_set (mpc_imagref (rop), y, rnd_im);
mpfr_clear (y);
}
return MPC_INEX (inex_re, inex_im);
}
/* regular number argument */
{
mpfr_t a, b, x, y;
mpfr_prec_t prec, p;
mpfr_exp_t err, expo;
int ok = 0;
mpfr_t minus_op_re;
mpfr_exp_t op_re_exp, op_im_exp;
mpfr_rnd_t rnd1, rnd2;
mpfr_inits2 (MPFR_PREC_MIN, a, b, x, y, (mpfr_ptr) 0);
/* real part: Re(arctan(x+i*y)) = [arctan2(x,1-y) - arctan2(-x,1+y)]/2 */
minus_op_re[0] = mpc_realref (op)[0];
MPFR_CHANGE_SIGN (minus_op_re);
op_re_exp = mpfr_get_exp (mpc_realref (op));
op_im_exp = mpfr_get_exp (mpc_imagref (op));
prec = mpfr_get_prec (mpc_realref (rop)); /* result precision */
/* a = o(1-y) error(a) < 1 ulp(a)
b = o(atan2(x,a)) error(b) < [1+2^{3+Exp(x)-Exp(a)-Exp(b)}] ulp(b)
= kb ulp(b)
c = o(1+y) error(c) < 1 ulp(c)
d = o(atan2(-x,c)) error(d) < [1+2^{3+Exp(x)-Exp(c)-Exp(d)}] ulp(d)
= kd ulp(d)
e = o(b - d) error(e) < [1 + kb*2^{Exp(b}-Exp(e)}
+ kd*2^{Exp(d)-Exp(e)}] ulp(e)
error(e) < [1 + 2^{4+Exp(x)-Exp(a)-Exp(e)}
+ 2^{4+Exp(x)-Exp(c)-Exp(e)}] ulp(e)
because |atan(u)| < |u|
< [1 + 2^{5+Exp(x)-min(Exp(a),Exp(c))
-Exp(e)}] ulp(e)
f = e/2 exact
*/
/* p: working precision */
p = (op_im_exp > 0 || prec > SAFE_ABS (mpfr_prec_t, op_im_exp)) ? prec
: (prec - op_im_exp);
rnd1 = mpfr_sgn (mpc_realref (op)) > 0 ? GMP_RNDD : GMP_RNDU;
rnd2 = mpfr_sgn (mpc_realref (op)) < 0 ? GMP_RNDU : GMP_RNDD;
do
{
p += mpc_ceil_log2 (p) + 2;
mpfr_set_prec (a, p);
mpfr_set_prec (b, p);
mpfr_set_prec (x, p);
/* x = upper bound for atan (x/(1-y)). Since atan is increasing, we
need an upper bound on x/(1-y), i.e., a lower bound on 1-y for
x positive, and an upper bound on 1-y for x negative */
mpfr_ui_sub (a, 1, mpc_imagref (op), rnd1);
if (mpfr_sgn (a) == 0) /* y is near 1, thus 1+y is near 2, and
expo will be 1 or 2 below */
{
MPC_ASSERT (mpfr_cmp_ui (mpc_imagref(op), 1) == 0);
/* check for intermediate underflow */
err = 2; /* ensures err will be expo below */
}
else
err = mpfr_get_exp (a); /* err = Exp(a) with the notations above */
mpfr_atan2 (x, mpc_realref (op), a, GMP_RNDU);
/* b = lower bound for atan (-x/(1+y)): for x negative, we need a
lower bound on -x/(1+y), i.e., an upper bound on 1+y */
mpfr_add_ui (a, mpc_imagref(op), 1, rnd2);
/* if a is exactly zero, i.e., Im(op) = -1, then the error on a is 0,
and we can simply ignore the terms involving Exp(a) in the error */
if (mpfr_sgn (a) == 0)
{
MPC_ASSERT (mpfr_cmp_si (mpc_imagref(op), -1) == 0);
/* check for intermediate underflow */
expo = err; /* will leave err unchanged below */
}
else
expo = mpfr_get_exp (a); /* expo = Exp(c) with the notations above */
mpfr_atan2 (b, minus_op_re, a, GMP_RNDD);
err = err < expo ? err : expo; /* err = min(Exp(a),Exp(c)) */
mpfr_sub (x, x, b, GMP_RNDU);
err = 5 + op_re_exp - err - mpfr_get_exp (x);
/* error is bounded by [1 + 2^err] ulp(e) */
err = err < 0 ? 1 : err + 1;
mpfr_div_2ui (x, x, 1, GMP_RNDU);
/* Note: using RND2=RNDD guarantees that if x is exactly representable
on prec + ... bits, mpfr_can_round will return 0 */
ok = mpfr_can_round (x, p - err, GMP_RNDU, GMP_RNDD,
prec + (MPC_RND_RE (rnd) == GMP_RNDN));
} while (ok == 0);
/* Imaginary part
Im(atan(x+I*y)) = 1/4 * [log(x^2+(1+y)^2) - log (x^2 +(1-y)^2)] */
prec = mpfr_get_prec (mpc_imagref (rop)); /* result precision */
/* a = o(1+y) error(a) < 1 ulp(a)
b = o(a^2) error(b) < 5 ulp(b)
c = o(x^2) error(c) < 1 ulp(c)
d = o(b+c) error(d) < 7 ulp(d)
e = o(log(d)) error(e) < [1 + 7*2^{2-Exp(e)}] ulp(e) = ke ulp(e)
f = o(1-y) error(f) < 1 ulp(f)
g = o(f^2) error(g) < 5 ulp(g)
h = o(c+f) error(h) < 7 ulp(h)
i = o(log(h)) error(i) < [1 + 7*2^{2-Exp(i)}] ulp(i) = ki ulp(i)
j = o(e-i) error(j) < [1 + ke*2^{Exp(e)-Exp(j)}
+ ki*2^{Exp(i)-Exp(j)}] ulp(j)
error(j) < [1 + 2^{Exp(e)-Exp(j)} + 2^{Exp(i)-Exp(j)}
+ 7*2^{3-Exp(j)}] ulp(j)
< [1 + 2^{max(Exp(e),Exp(i))-Exp(j)+1}
+ 7*2^{3-Exp(j)}] ulp(j)
k = j/4 exact
*/
err = 2;
p = prec; /* working precision */
do
{
p += mpc_ceil_log2 (p) + err;
mpfr_set_prec (a, p);
mpfr_set_prec (b, p);
mpfr_set_prec (y, p);
/* a = upper bound for log(x^2 + (1+y)^2) */
ROUND_AWAY (mpfr_add_ui (a, mpc_imagref (op), 1, MPFR_RNDA), a);
mpfr_sqr (a, a, GMP_RNDU);
mpfr_sqr (y, mpc_realref (op), GMP_RNDU);
mpfr_add (a, a, y, GMP_RNDU);
mpfr_log (a, a, GMP_RNDU);
/* b = lower bound for log(x^2 + (1-y)^2) */
mpfr_ui_sub (b, 1, mpc_imagref (op), GMP_RNDZ); /* round to zero */
mpfr_sqr (b, b, GMP_RNDZ);
/* we could write mpfr_sqr (y, mpc_realref (op), GMP_RNDZ) but it is
more efficient to reuse the value of y (x^2) above and subtract
one ulp */
mpfr_nextbelow (y);
mpfr_add (b, b, y, GMP_RNDZ);
mpfr_log (b, b, GMP_RNDZ);
mpfr_sub (y, a, b, GMP_RNDU);
if (mpfr_zero_p (y))
/* FIXME: happens when x and y have very different magnitudes;
could be handled more efficiently */
ok = 0;
else
{
expo = MPC_MAX (mpfr_get_exp (a), mpfr_get_exp (b));
expo = expo - mpfr_get_exp (y) + 1;
err = 3 - mpfr_get_exp (y);
/* error(j) <= [1 + 2^expo + 7*2^err] ulp(j) */
if (expo <= err) /* error(j) <= [1 + 2^{err+1}] ulp(j) */
err = (err < 0) ? 1 : err + 2;
else
err = (expo < 0) ? 1 : expo + 2;
mpfr_div_2ui (y, y, 2, GMP_RNDN);
MPC_ASSERT (!mpfr_zero_p (y));
/* FIXME: underflow. Since the main term of the Taylor series
in y=0 is 1/(x^2+1) * y, this means that y is very small
and/or x very large; but then the mpfr_zero_p (y) above
should be true. This needs a proof, or better yet,
special code. */
ok = mpfr_can_round (y, p - err, GMP_RNDU, GMP_RNDD,
prec + (MPC_RND_IM (rnd) == GMP_RNDN));
}
} while (ok == 0);
inex = mpc_set_fr_fr (rop, x, y, rnd);
mpfr_clears (a, b, x, y, (mpfr_ptr) 0);
return inex;
}
}
int
mpc_asin (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
{
mpfr_prec_t p, p_re, p_im, incr_p = 0;
mpfr_rnd_t rnd_re, rnd_im;
mpc_t z1;
int inex;
/* special values */
if (mpfr_nan_p (mpc_realref (op)) || mpfr_nan_p (mpc_imagref (op)))
{
if (mpfr_inf_p (mpc_realref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
mpfr_set_nan (mpc_realref (rop));
mpfr_set_inf (mpc_imagref (rop), mpfr_signbit (mpc_imagref (op)) ? -1 : +1);
}
else if (mpfr_zero_p (mpc_realref (op)))
{
mpfr_set (mpc_realref (rop), mpc_realref (op), GMP_RNDN);
mpfr_set_nan (mpc_imagref (rop));
}
else
{
mpfr_set_nan (mpc_realref (rop));
mpfr_set_nan (mpc_imagref (rop));
}
return 0;
}
if (mpfr_inf_p (mpc_realref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
int inex_re;
if (mpfr_inf_p (mpc_realref (op)))
{
int inf_im = mpfr_inf_p (mpc_imagref (op));
inex_re = set_pi_over_2 (mpc_realref (rop),
(mpfr_signbit (mpc_realref (op)) ? -1 : 1), MPC_RND_RE (rnd));
mpfr_set_inf (mpc_imagref (rop), (mpfr_signbit (mpc_imagref (op)) ? -1 : 1));
if (inf_im)
mpfr_div_2ui (mpc_realref (rop), mpc_realref (rop), 1, GMP_RNDN);
}
else
{
mpfr_set_zero (mpc_realref (rop), (mpfr_signbit (mpc_realref (op)) ? -1 : 1));
inex_re = 0;
mpfr_set_inf (mpc_imagref (rop), (mpfr_signbit (mpc_imagref (op)) ? -1 : 1));
}
return MPC_INEX (inex_re, 0);
}
/* pure real argument */
if (mpfr_zero_p (mpc_imagref (op)))
{
int inex_re;
int inex_im;
int s_im;
s_im = mpfr_signbit (mpc_imagref (op));
if (mpfr_cmp_ui (mpc_realref (op), 1) > 0)
{
if (s_im)
inex_im = -mpfr_acosh (mpc_imagref (rop), mpc_realref (op),
INV_RND (MPC_RND_IM (rnd)));
else
inex_im = mpfr_acosh (mpc_imagref (rop), mpc_realref (op),
MPC_RND_IM (rnd));
inex_re = set_pi_over_2 (mpc_realref (rop),
(mpfr_signbit (mpc_realref (op)) ? -1 : 1), MPC_RND_RE (rnd));
if (s_im)
mpc_conj (rop, rop, MPC_RNDNN);
}
else if (mpfr_cmp_si (mpc_realref (op), -1) < 0)
{
mpfr_t minus_op_re;
minus_op_re[0] = mpc_realref (op)[0];
MPFR_CHANGE_SIGN (minus_op_re);
if (s_im)
inex_im = -mpfr_acosh (mpc_imagref (rop), minus_op_re,
INV_RND (MPC_RND_IM (rnd)));
else
inex_im = mpfr_acosh (mpc_imagref (rop), minus_op_re,
MPC_RND_IM (rnd));
inex_re = set_pi_over_2 (mpc_realref (rop),
(mpfr_signbit (mpc_realref (op)) ? -1 : 1), MPC_RND_RE (rnd));
if (s_im)
mpc_conj (rop, rop, MPC_RNDNN);
}
else
{
inex_im = mpfr_set_ui (mpc_imagref (rop), 0, MPC_RND_IM (rnd));
if (s_im)
mpfr_neg (mpc_imagref (rop), mpc_imagref (rop), GMP_RNDN);
inex_re = mpfr_asin (mpc_realref (rop), mpc_realref (op), MPC_RND_RE (rnd));
}
return MPC_INEX (inex_re, inex_im);
}
/* pure imaginary argument */
if (mpfr_zero_p (mpc_realref (op)))
{
int inex_im;
int s;
s = mpfr_signbit (mpc_realref (op));
mpfr_set_ui (mpc_realref (rop), 0, GMP_RNDN);
if (s)
mpfr_neg (mpc_realref (rop), mpc_realref (rop), GMP_RNDN);
inex_im = mpfr_asinh (mpc_imagref (rop), mpc_imagref (op), MPC_RND_IM (rnd));
return MPC_INEX (0, inex_im);
}
/* regular complex: asin(z) = -i*log(i*z+sqrt(1-z^2)) */
p_re = mpfr_get_prec (mpc_realref(rop));
p_im = mpfr_get_prec (mpc_imagref(rop));
rnd_re = MPC_RND_RE(rnd);
rnd_im = MPC_RND_IM(rnd);
p = p_re >= p_im ? p_re : p_im;
mpc_init2 (z1, p);
while (1)
{
mpfr_exp_t ex, ey, err;
p += mpc_ceil_log2 (p) + 3 + incr_p; /* incr_p is zero initially */
incr_p = p / 2;
mpfr_set_prec (mpc_realref(z1), p);
mpfr_set_prec (mpc_imagref(z1), p);
/* z1 <- z^2 */
mpc_sqr (z1, op, MPC_RNDNN);
/* err(x) <= 1/2 ulp(x), err(y) <= 1/2 ulp(y) */
/* z1 <- 1-z1 */
ex = mpfr_get_exp (mpc_realref(z1));
mpfr_ui_sub (mpc_realref(z1), 1, mpc_realref(z1), GMP_RNDN);
mpfr_neg (mpc_imagref(z1), mpc_imagref(z1), GMP_RNDN);
ex = ex - mpfr_get_exp (mpc_realref(z1));
ex = (ex <= 0) ? 0 : ex;
/* err(x) <= 2^ex * ulp(x) */
ex = ex + mpfr_get_exp (mpc_realref(z1)) - p;
/* err(x) <= 2^ex */
ey = mpfr_get_exp (mpc_imagref(z1)) - p - 1;
/* err(y) <= 2^ey */
ex = (ex >= ey) ? ex : ey; /* err(x), err(y) <= 2^ex, i.e., the norm
of the error is bounded by |h|<=2^(ex+1/2) */
/* z1 <- sqrt(z1): if z1 = z + h, then sqrt(z1) = sqrt(z) + h/2/sqrt(t) */
ey = mpfr_get_exp (mpc_realref(z1)) >= mpfr_get_exp (mpc_imagref(z1))
? mpfr_get_exp (mpc_realref(z1)) : mpfr_get_exp (mpc_imagref(z1));
/* we have |z1| >= 2^(ey-1) thus 1/|z1| <= 2^(1-ey) */
mpc_sqrt (z1, z1, MPC_RNDNN);
ex = (2 * ex + 1) - 2 - (ey - 1); /* |h^2/4/|t| <= 2^ex */
ex = (ex + 1) / 2; /* ceil(ex/2) */
/* express ex in terms of ulp(z1) */
ey = mpfr_get_exp (mpc_realref(z1)) <= mpfr_get_exp (mpc_imagref(z1))
? mpfr_get_exp (mpc_realref(z1)) : mpfr_get_exp (mpc_imagref(z1));
ex = ex - ey + p;
/* take into account the rounding error in the mpc_sqrt call */
err = (ex <= 0) ? 1 : ex + 1;
/* err(x) <= 2^err * ulp(x), err(y) <= 2^err * ulp(y) */
/* z1 <- i*z + z1 */
ex = mpfr_get_exp (mpc_realref(z1));
ey = mpfr_get_exp (mpc_imagref(z1));
mpfr_sub (mpc_realref(z1), mpc_realref(z1), mpc_imagref(op), GMP_RNDN);
mpfr_add (mpc_imagref(z1), mpc_imagref(z1), mpc_realref(op), GMP_RNDN);
if (mpfr_cmp_ui (mpc_realref(z1), 0) == 0 || mpfr_cmp_ui (mpc_imagref(z1), 0) == 0)
continue;
ex -= mpfr_get_exp (mpc_realref(z1)); /* cancellation in x */
ey -= mpfr_get_exp (mpc_imagref(z1)); /* cancellation in y */
ex = (ex >= ey) ? ex : ey; /* maximum cancellation */
err += ex;
err = (err <= 0) ? 1 : err + 1; /* rounding error in sub/add */
/* z1 <- log(z1): if z1 = z + h, then log(z1) = log(z) + h/t with
|t| >= min(|z1|,|z|) */
ex = mpfr_get_exp (mpc_realref(z1));
ey = mpfr_get_exp (mpc_imagref(z1));
ex = (ex >= ey) ? ex : ey;
err += ex - p; /* revert to absolute error <= 2^err */
mpc_log (z1, z1, GMP_RNDN);
err -= ex - 1; /* 1/|t| <= 1/|z| <= 2^(1-ex) */
/* express err in terms of ulp(z1) */
ey = mpfr_get_exp (mpc_realref(z1)) <= mpfr_get_exp (mpc_imagref(z1))
? mpfr_get_exp (mpc_realref(z1)) : mpfr_get_exp (mpc_imagref(z1));
err = err - ey + p;
/* take into account the rounding error in the mpc_log call */
err = (err <= 0) ? 1 : err + 1;
/* z1 <- -i*z1 */
mpfr_swap (mpc_realref(z1), mpc_imagref(z1));
mpfr_neg (mpc_imagref(z1), mpc_imagref(z1), GMP_RNDN);
if (mpfr_can_round (mpc_realref(z1), p - err, GMP_RNDN, GMP_RNDZ,
p_re + (rnd_re == GMP_RNDN)) &&
mpfr_can_round (mpc_imagref(z1), p - err, GMP_RNDN, GMP_RNDZ,
p_im + (rnd_im == GMP_RNDN)))
break;
}
inex = mpc_set (rop, z1, rnd);
mpc_clear (z1);
return inex;
}
int
mpc_acos (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
{
int inex_re, inex_im, inex;
mpfr_prec_t p_re, p_im, p;
mpc_t z1;
mpfr_t pi_over_2;
mpfr_exp_t e1, e2;
mpfr_rnd_t rnd_im;
mpc_rnd_t rnd1;
inex_re = 0;
inex_im = 0;
/* special values */
if (mpfr_nan_p (mpc_realref (op)) || mpfr_nan_p (mpc_imagref (op)))
{
if (mpfr_inf_p (mpc_realref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
mpfr_set_inf (mpc_imagref (rop), mpfr_signbit (mpc_imagref (op)) ? +1 : -1);
mpfr_set_nan (mpc_realref (rop));
}
else if (mpfr_zero_p (mpc_realref (op)))
{
inex_re = set_pi_over_2 (mpc_realref (rop), +1, MPC_RND_RE (rnd));
mpfr_set_nan (mpc_imagref (rop));
}
else
{
mpfr_set_nan (mpc_realref (rop));
mpfr_set_nan (mpc_imagref (rop));
}
return MPC_INEX (inex_re, 0);
}
if (mpfr_inf_p (mpc_realref (op)) || mpfr_inf_p (mpc_imagref (op)))
{
if (mpfr_inf_p (mpc_realref (op)))
{
if (mpfr_inf_p (mpc_imagref (op)))
{
if (mpfr_sgn (mpc_realref (op)) > 0)
{
inex_re =
set_pi_over_2 (mpc_realref (rop), +1, MPC_RND_RE (rnd));
mpfr_div_2ui (mpc_realref (rop), mpc_realref (rop), 1, GMP_RNDN);
}
else
{
/* the real part of the result is 3*pi/4
a = o(pi) error(a) < 1 ulp(a)
b = o(3*a) error(b) < 2 ulp(b)
c = b/4 exact
thus 1 bit is lost */
mpfr_t x;
mpfr_prec_t prec;
int ok;
mpfr_init (x);
prec = mpfr_get_prec (mpc_realref (rop));
p = prec;
do
{
p += mpc_ceil_log2 (p);
mpfr_set_prec (x, p);
mpfr_const_pi (x, GMP_RNDD);
mpfr_mul_ui (x, x, 3, GMP_RNDD);
ok =
mpfr_can_round (x, p - 1, GMP_RNDD, MPC_RND_RE (rnd),
prec+(MPC_RND_RE (rnd) == GMP_RNDN));
} while (ok == 0);
inex_re =
mpfr_div_2ui (mpc_realref (rop), x, 2, MPC_RND_RE (rnd));
mpfr_clear (x);
}
}
else
{
if (mpfr_sgn (mpc_realref (op)) > 0)
mpfr_set_ui (mpc_realref (rop), 0, GMP_RNDN);
else
inex_re = mpfr_const_pi (mpc_realref (rop), MPC_RND_RE (rnd));
}
}
else
inex_re = set_pi_over_2 (mpc_realref (rop), +1, MPC_RND_RE (rnd));
mpfr_set_inf (mpc_imagref (rop), mpfr_signbit (mpc_imagref (op)) ? +1 : -1);
return MPC_INEX (inex_re, 0);
}
/* pure real argument */
if (mpfr_zero_p (mpc_imagref (op)))
{
int s_im;
s_im = mpfr_signbit (mpc_imagref (op));
if (mpfr_cmp_ui (mpc_realref (op), 1) > 0)
{
if (s_im)
inex_im = mpfr_acosh (mpc_imagref (rop), mpc_realref (op),
MPC_RND_IM (rnd));
else
inex_im = -mpfr_acosh (mpc_imagref (rop), mpc_realref (op),
INV_RND (MPC_RND_IM (rnd)));
mpfr_set_ui (mpc_realref (rop), 0, GMP_RNDN);
}
else if (mpfr_cmp_si (mpc_realref (op), -1) < 0)
{
mpfr_t minus_op_re;
minus_op_re[0] = mpc_realref (op)[0];
MPFR_CHANGE_SIGN (minus_op_re);
if (s_im)
inex_im = mpfr_acosh (mpc_imagref (rop), minus_op_re,
MPC_RND_IM (rnd));
else
inex_im = -mpfr_acosh (mpc_imagref (rop), minus_op_re,
INV_RND (MPC_RND_IM (rnd)));
inex_re = mpfr_const_pi (mpc_realref (rop), MPC_RND_RE (rnd));
}
else
{
inex_re = mpfr_acos (mpc_realref (rop), mpc_realref (op), MPC_RND_RE (rnd));
mpfr_set_ui (mpc_imagref (rop), 0, MPC_RND_IM (rnd));
}
if (!s_im)
mpc_conj (rop, rop, MPC_RNDNN);
return MPC_INEX (inex_re, inex_im);
}
/* pure imaginary argument */
if (mpfr_zero_p (mpc_realref (op)))
{
inex_re = set_pi_over_2 (mpc_realref (rop), +1, MPC_RND_RE (rnd));
inex_im = -mpfr_asinh (mpc_imagref (rop), mpc_imagref (op),
INV_RND (MPC_RND_IM (rnd)));
mpc_conj (rop,rop, MPC_RNDNN);
return MPC_INEX (inex_re, inex_im);
}
/* regular complex argument: acos(z) = Pi/2 - asin(z) */
p_re = mpfr_get_prec (mpc_realref(rop));
p_im = mpfr_get_prec (mpc_imagref(rop));
p = p_re;
mpc_init3 (z1, p, p_im); /* we round directly the imaginary part to p_im,
with rounding mode opposite to rnd_im */
rnd_im = MPC_RND_IM(rnd);
/* the imaginary part of asin(z) has the same sign as Im(z), thus if
Im(z) > 0 and rnd_im = RNDZ, we want to round the Im(asin(z)) to -Inf
so that -Im(asin(z)) is rounded to zero */
if (rnd_im == GMP_RNDZ)
rnd_im = mpfr_sgn (mpc_imagref(op)) > 0 ? GMP_RNDD : GMP_RNDU;
else
rnd_im = rnd_im == GMP_RNDU ? GMP_RNDD
: rnd_im == GMP_RNDD ? GMP_RNDU
: rnd_im; /* both RNDZ and RNDA map to themselves for -asin(z) */
rnd1 = MPC_RND (GMP_RNDN, rnd_im);
mpfr_init2 (pi_over_2, p);
for (;;)
{
p += mpc_ceil_log2 (p) + 3;
mpfr_set_prec (mpc_realref(z1), p);
mpfr_set_prec (pi_over_2, p);
set_pi_over_2 (pi_over_2, +1, GMP_RNDN);
e1 = 1; /* Exp(pi_over_2) */
inex = mpc_asin (z1, op, rnd1); /* asin(z) */
MPC_ASSERT (mpfr_sgn (mpc_imagref(z1)) * mpfr_sgn (mpc_imagref(op)) > 0);
inex_im = MPC_INEX_IM(inex); /* inex_im is in {-1, 0, 1} */
e2 = mpfr_get_exp (mpc_realref(z1));
mpfr_sub (mpc_realref(z1), pi_over_2, mpc_realref(z1), GMP_RNDN);
if (!mpfr_zero_p (mpc_realref(z1)))
{
/* the error on x=Re(z1) is bounded by 1/2 ulp(x) + 2^(e1-p-1) +
2^(e2-p-1) */
e1 = e1 >= e2 ? e1 + 1 : e2 + 1;
/* the error on x is bounded by 1/2 ulp(x) + 2^(e1-p-1) */
e1 -= mpfr_get_exp (mpc_realref(z1));
/* the error on x is bounded by 1/2 ulp(x) [1 + 2^e1] */
e1 = e1 <= 0 ? 0 : e1;
/* the error on x is bounded by 2^e1 * ulp(x) */
mpfr_neg (mpc_imagref(z1), mpc_imagref(z1), GMP_RNDN); /* exact */
inex_im = -inex_im;
if (mpfr_can_round (mpc_realref(z1), p - e1, GMP_RNDN, GMP_RNDZ,
p_re + (MPC_RND_RE(rnd) == GMP_RNDN)))
break;
}
}
inex = mpc_set (rop, z1, rnd);
inex_re = MPC_INEX_RE(inex);
mpc_clear (z1);
mpfr_clear (pi_over_2);
return MPC_INEX(inex_re, inex_im);
}
