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_log10 (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
{
int ok = 0, loops = 0, check_exact = 0, special_re, special_im,
inex, inex_re, inex_im;
mpfr_prec_t prec;
mpfr_t log10;
mpc_t log;
mpfr_init2 (log10, 2);
mpc_init2 (log, 2);
prec = MPC_MAX_PREC (rop);
/* compute log(op)/log(10) */
while (ok == 0) {
loops ++;
prec += (loops <= 2) ? mpc_ceil_log2 (prec) + 4 : prec / 2;
mpfr_set_prec (log10, prec);
mpc_set_prec (log, prec);
inex = mpc_log (log, op, rnd); /* error <= 1 ulp */
if (!mpfr_number_p (mpc_imagref (log))
|| mpfr_zero_p (mpc_imagref (log))) {
/* no need to divide by log(10) */
special_im = 1;
ok = 1;
}
else {
special_im = 0;
mpfr_const_log10 (log10);
mpfr_div (mpc_imagref (log), mpc_imagref (log), log10, MPFR_RNDN);
ok = mpfr_can_round (mpc_imagref (log), prec - 2,
MPFR_RNDN, MPFR_RNDZ,
MPC_PREC_IM(rop) + (MPC_RND_IM (rnd) == MPFR_RNDN));
}
if (ok) {
if (!mpfr_number_p (mpc_realref (log))
|| mpfr_zero_p (mpc_realref (log)))
special_re = 1;
else {
special_re = 0;
if (special_im)
/* log10 not yet computed */
mpfr_const_log10 (log10);
mpfr_div (mpc_realref (log), mpc_realref (log), log10, MPFR_RNDN);
/* error <= 24/7 ulp < 4 ulp for prec >= 4, see algorithms.tex */
ok = mpfr_can_round (mpc_realref (log), prec - 2,
MPFR_RNDN, MPFR_RNDZ,
MPC_PREC_RE(rop) + (MPC_RND_RE (rnd) == MPFR_RNDN));
}
/* Special code to deal with cases where the real part of log10(x+i*y)
is exact, like x=3 and y=1. Since Re(log10(x+i*y)) = log10(x^2+y^2)/2
this happens whenever x^2+y^2 is a nonnegative power of 10.
Indeed x^2+y^2 cannot equal 10^(a/2^b) for a, b integers, a odd, b>0,
since x^2+y^2 is rational, and 10^(a/2^b) is irrational.
Similarly, for b=0, x^2+y^2 cannot equal 10^a for a < 0 since x^2+y^2
is a rational with denominator a power of 2.
Now let x^2+y^2 = 10^s. Without loss of generality we can assume
x = u/2^e and y = v/2^e with u, v, e integers: u^2+v^2 = 10^s*2^(2e)
thus u^2+v^2 = 0 mod 2^(2e). By recurrence on e, necessarily
u = v = 0 mod 2^e, thus x and y are necessarily integers.
*/
if (!ok && !check_exact && mpfr_integer_p (mpc_realref (op)) &&
mpfr_integer_p (mpc_imagref (op))) {
mpz_t x, y;
unsigned long s, v;
check_exact = 1;
mpz_init (x);
mpz_init (y);
mpfr_get_z (x, mpc_realref (op), MPFR_RNDN); /* exact */
mpfr_get_z (y, mpc_imagref (op), MPFR_RNDN); /* exact */
mpz_mul (x, x, x);
mpz_mul (y, y, y);
mpz_add (x, x, y); /* x^2+y^2 */
v = mpz_scan1 (x, 0);
/* if x = 10^s then necessarily s = v */
s = mpz_sizeinbase (x, 10);
/* since s is either the number of digits of x or one more,
then x = 10^(s-1) or 10^(s-2) */
if (s == v + 1 || s == v + 2) {
mpz_div_2exp (x, x, v);
mpz_ui_pow_ui (y, 5, v);
if (mpz_cmp (y, x) == 0) {
/* Re(log10(x+i*y)) is exactly v/2
we reset the precision of Re(log) so that v can be
represented exactly */
mpfr_set_prec (mpc_realref (log),
sizeof(unsigned long)*CHAR_BIT);
mpfr_set_ui_2exp (mpc_realref (log), v, -1, MPFR_RNDN);
/* exact */
ok = 1;
}
}
mpz_clear (x);
mpz_clear (y);
}
}
}
inex_re = mpfr_set (mpc_realref(rop), mpc_realref (log), MPC_RND_RE (rnd));
if (special_re)
inex_re = MPC_INEX_RE (inex);
/* recover flag from call to mpc_log above */
inex_im = mpfr_set (mpc_imagref(rop), mpc_imagref (log), MPC_RND_IM (rnd));
if (special_im)
inex_im = MPC_INEX_IM (inex);
mpfr_clear (log10);
mpc_clear (log);
return MPC_INEX(inex_re, inex_im);
}
/* Put in z the value of x^y, rounded according to 'rnd'.
Return the inexact flag in [0, 10]. */
int
mpc_pow (mpc_ptr z, mpc_srcptr x, mpc_srcptr y, mpc_rnd_t rnd)
{
int ret = -2, loop, x_real, y_real, z_real = 0, z_imag = 0;
mpc_t t, u;
mp_prec_t p, q, pr, pi, maxprec;
long Q;
x_real = mpfr_zero_p (MPC_IM(x));
y_real = mpfr_zero_p (MPC_IM(y));
if (y_real && mpfr_zero_p (MPC_RE(y))) /* case y zero */
{
if (x_real && mpfr_zero_p (MPC_RE(x))) /* 0^0 = NaN +i*NaN */
{
mpfr_set_nan (MPC_RE(z));
mpfr_set_nan (MPC_IM(z));
return 0;
}
else /* x^0 = 1 +/- i*0 even for x=NaN see algorithms.tex for the
sign of zero */
{
mpfr_t n;
int inex, cx1;
int sign_zi;
/* cx1 < 0 if |x| < 1
cx1 = 0 if |x| = 1
cx1 > 0 if |x| > 1
*/
mpfr_init (n);
inex = mpc_norm (n, x, GMP_RNDN);
cx1 = mpfr_cmp_ui (n, 1);
if (cx1 == 0 && inex != 0)
cx1 = -inex;
sign_zi = (cx1 < 0 && mpfr_signbit (MPC_IM (y)) == 0)
|| (cx1 == 0
&& mpfr_signbit (MPC_IM (x)) != mpfr_signbit (MPC_RE (y)))
|| (cx1 > 0 && mpfr_signbit (MPC_IM (y)));
/* warning: mpc_set_ui_ui does not set Im(z) to -0 if Im(rnd)=RNDD */
ret = mpc_set_ui_ui (z, 1, 0, rnd);
if (MPC_RND_IM (rnd) == GMP_RNDD || sign_zi)
mpc_conj (z, z, MPC_RNDNN);
mpfr_clear (n);
return ret;
}
}
if (mpfr_nan_p (MPC_RE(x)) || mpfr_nan_p (MPC_IM(x)) ||
mpfr_nan_p (MPC_RE(y)) || mpfr_nan_p (MPC_IM(y)) ||
mpfr_inf_p (MPC_RE(x)) || mpfr_inf_p (MPC_IM(x)) ||
mpfr_inf_p (MPC_RE(y)) || mpfr_inf_p (MPC_IM(y)))
{
/* special values: exp(y*log(x)) */
mpc_init2 (u, 2);
mpc_log (u, x, MPC_RNDNN);
mpc_mul (u, u, y, MPC_RNDNN);
ret = mpc_exp (z, u, rnd);
mpc_clear (u);
goto end;
}
if (x_real) /* case x real */
{
if (mpfr_zero_p (MPC_RE(x))) /* x is zero */
{
/* special values: exp(y*log(x)) */
mpc_init2 (u, 2);
mpc_log (u, x, MPC_RNDNN);
mpc_mul (u, u, y, MPC_RNDNN);
ret = mpc_exp (z, u, rnd);
mpc_clear (u);
goto end;
}
/* Special case 1^y = 1 */
if (mpfr_cmp_ui (MPC_RE(x), 1) == 0)
{
int s1, s2;
s1 = mpfr_signbit (MPC_RE (y));
s2 = mpfr_signbit (MPC_IM (x));
ret = mpc_set_ui (z, +1, rnd);
/* the sign of the zero imaginary part is known in some cases (see
algorithm.tex). In such cases we have
(x +s*0i)^(y+/-0i) = x^y + s*sign(y)*0i
where s = +/-1. We extend here this rule to fix the sign of the
zero part.
Note that the sign must also be set explicitly when rnd=RNDD
because mpfr_set_ui(z_i, 0, rnd) always sets z_i to +0.
*/
if (MPC_RND_IM (rnd) == GMP_RNDD || s1 != s2)
mpc_conj (z, z, MPC_RNDNN);
goto end;
}
/* x^y is real when:
(a) x is real and y is integer
(b) x is real non-negative and y is real */
if (y_real && (mpfr_integer_p (MPC_RE(y)) ||
mpfr_cmp_ui (MPC_RE(x), 0) >= 0))
{
int s1, s2;
s1 = mpfr_signbit (MPC_RE (y));
s2 = mpfr_signbit (MPC_IM (x));
ret = mpfr_pow (MPC_RE(z), MPC_RE(x), MPC_RE(y), MPC_RND_RE(rnd));
ret = MPC_INEX(ret, mpfr_set_ui (MPC_IM(z), 0, MPC_RND_IM(rnd)));
/* the sign of the zero imaginary part is known in some cases
(see algorithm.tex). In such cases we have (x +s*0i)^(y+/-0i)
= x^y + s*sign(y)*0i where s = +/-1.
We extend here this rule to fix the sign of the zero part.
Note that the sign must also be set explicitly when rnd=RNDD
because mpfr_set_ui(z_i, 0, rnd) always sets z_i to +0.
*/
if (MPC_RND_IM(rnd) == GMP_RNDD || s1 != s2)
mpfr_neg (MPC_IM(z), MPC_IM(z), MPC_RND_IM(rnd));
goto end;
}
/* (-1)^(n+I*t) is real for n integer and t real */
if (mpfr_cmp_si (MPC_RE(x), -1) == 0 && mpfr_integer_p (MPC_RE(y)))
z_real = 1;
/* for x real, x^y is imaginary when:
(a) x is negative and y is half-an-integer
(b) x = -1 and Re(y) is half-an-integer
*/
if (mpfr_cmp_ui (MPC_RE(x), 0) < 0 && is_odd (MPC_RE(y), 1) &&
(y_real || mpfr_cmp_si (MPC_RE(x), -1) == 0))
z_imag = 1;
}
else /* x non real */
/* I^(t*I) and (-I)^(t*I) are real for t real,
I^(n+t*I) and (-I)^(n+t*I) are real for n even and t real, and
I^(n+t*I) and (-I)^(n+t*I) are imaginary for n odd and t real
(s*I)^n is real for n even and imaginary for n odd */
if ((mpc_cmp_si_si (x, 0, 1) == 0 || mpc_cmp_si_si (x, 0, -1) == 0 ||
(mpfr_cmp_ui (MPC_RE(x), 0) == 0 && y_real)) &&
mpfr_integer_p (MPC_RE(y)))
{ /* x is I or -I, and Re(y) is an integer */
if (is_odd (MPC_RE(y), 0))
z_imag = 1; /* Re(y) odd: z is imaginary */
else
z_real = 1; /* Re(y) even: z is real */
}
else /* (t+/-t*I)^(2n) is imaginary for n odd and real for n even */
if (mpfr_cmpabs (MPC_RE(x), MPC_IM(x)) == 0 && y_real &&
mpfr_integer_p (MPC_RE(y)) && is_odd (MPC_RE(y), 0) == 0)
{
if (is_odd (MPC_RE(y), -1)) /* y/2 is odd */
z_imag = 1;
else
z_real = 1;
}
/* first bound |Re(y log(x))|, |Im(y log(x)| < 2^q */
mpc_init2 (t, 64);
mpc_log (t, x, MPC_RNDNN);
mpc_mul (t, t, y, MPC_RNDNN);
/* the default maximum exponent for MPFR is emax=2^30-1, thus if
t > log(2^emax) = emax*log(2), then exp(t) will overflow */
if (mpfr_cmp_ui_2exp (MPC_RE(t), 372130558, 1) > 0)
goto overflow;
/* the default minimum exponent for MPFR is emin=-2^30+1, thus the
smallest representable value is 2^(emin-1), and if
t < log(2^(emin-1)) = (emin-1)*log(2), then exp(t) will underflow */
if (mpfr_cmp_si_2exp (MPC_RE(t), -372130558, 1) < 0)
goto underflow;
q = mpfr_get_exp (MPC_RE(t)) > 0 ? mpfr_get_exp (MPC_RE(t)) : 0;
if (mpfr_get_exp (MPC_IM(t)) > (mp_exp_t) q)
q = mpfr_get_exp (MPC_IM(t));
pr = mpfr_get_prec (MPC_RE(z));
pi = mpfr_get_prec (MPC_IM(z));
p = (pr > pi) ? pr : pi;
p += 11; /* experimentally, seems to give less than 10% of failures in
Ziv's strategy */
mpc_init2 (u, p);
pr += MPC_RND_RE(rnd) == GMP_RNDN;
pi += MPC_RND_IM(rnd) == GMP_RNDN;
maxprec = MPFR_PREC(MPC_RE(z));
if (MPFR_PREC(MPC_IM(z)) > maxprec)
maxprec = MPFR_PREC(MPC_IM(z));
for (loop = 0;; loop++)
{
mp_exp_t dr, di;
if (p + q > 64) /* otherwise we reuse the initial approximation
t of y*log(x), avoiding two computations */
{
mpc_set_prec (t, p + q);
mpc_log (t, x, MPC_RNDNN);
mpc_mul (t, t, y, MPC_RNDNN);
}
mpc_exp (u, t, MPC_RNDNN);
/* Since the error bound is global, we have to take into account the
exponent difference between the real and imaginary parts. We assume
either the real or the imaginary part of u is not zero.
*/
dr = mpfr_zero_p (MPC_RE(u)) ? mpfr_get_exp (MPC_IM(u))
: mpfr_get_exp (MPC_RE(u));
di = mpfr_zero_p (MPC_IM(u)) ? dr : mpfr_get_exp (MPC_IM(u));
if (dr > di)
{
di = dr - di;
dr = 0;
}
else
{
dr = di - dr;
di = 0;
}
/* the term -3 takes into account the factor 4 in the complex error
(see algorithms.tex) plus one due to the exponent difference: if
z = a + I*b, where the relative error on z is at most 2^(-p), and
EXP(a) = EXP(b) + k, the relative error on b is at most 2^(k-p) */
if ((z_imag || mpfr_can_round (MPC_RE(u), p - 3 - dr, GMP_RNDN, GMP_RNDZ, pr)) &&
(z_real || mpfr_can_round (MPC_IM(u), p - 3 - di, GMP_RNDN, GMP_RNDZ, pi)))
break;
/* if Re(u) is not known to be zero, assume it is a normal number, i.e.,
neither zero, Inf or NaN, otherwise we might enter an infinite loop */
MPC_ASSERT (z_imag || mpfr_number_p (MPC_RE(u)));
/* idem for Im(u) */
MPC_ASSERT (z_real || mpfr_number_p (MPC_IM(u)));
if (ret == -2) /* we did not yet call mpc_pow_exact, or it aborted
because intermediate computations had > maxprec bits */
{
/* check exact cases (see algorithms.tex) */
if (y_real)
{
maxprec *= 2;
ret = mpc_pow_exact (z, x, MPC_RE(y), rnd, maxprec);
if (ret != -1 && ret != -2)
goto exact;
}
p += dr + di + 64;
}
else
p += p / 2;
mpc_set_prec (t, p + q);
mpc_set_prec (u, p);
}
if (z_real)
{
/* When the result is real (see algorithm.tex for details),
Im(x^y) =
+ sign(imag(y))*0i, if |x| > 1
+ sign(imag(x))*sign(real(y))*0i, if |x| = 1
- sign(imag(y))*0i, if |x| < 1
*/
mpfr_t n;
int inex, cx1;
int sign_zi;
/* cx1 < 0 if |x| < 1
cx1 = 0 if |x| = 1
cx1 > 0 if |x| > 1
*/
mpfr_init (n);
inex = mpc_norm (n, x, GMP_RNDN);
cx1 = mpfr_cmp_ui (n, 1);
if (cx1 == 0 && inex != 0)
cx1 = -inex;
sign_zi = (cx1 < 0 && mpfr_signbit (MPC_IM (y)) == 0)
|| (cx1 == 0
&& mpfr_signbit (MPC_IM (x)) != mpfr_signbit (MPC_RE (y)))
|| (cx1 > 0 && mpfr_signbit (MPC_IM (y)));
ret = mpfr_set (MPC_RE(z), MPC_RE(u), MPC_RND_RE(rnd));
/* warning: mpfr_set_ui does not set Im(z) to -0 if Im(rnd) = RNDD */
ret = MPC_INEX (ret, mpfr_set_ui (MPC_IM (z), 0, MPC_RND_IM (rnd)));
if (MPC_RND_IM (rnd) == GMP_RNDD || sign_zi)
mpc_conj (z, z, MPC_RNDNN);
mpfr_clear (n);
}
else if (z_imag)
{
ret = mpfr_set (MPC_IM(z), MPC_IM(u), MPC_RND_IM(rnd));
ret = MPC_INEX(mpfr_set_ui (MPC_RE(z), 0, MPC_RND_RE(rnd)), ret);
}
else
ret = mpc_set (z, u, rnd);
exact:
mpc_clear (t);
mpc_clear (u);
end:
return ret;
underflow:
/* If we have an underflow, we know that |z| is too small to be
represented, but depending on arg(z), we should return +/-0 +/- I*0.
We assume t is the approximation of y*log(x), thus we want
exp(t) = exp(Re(t))+exp(I*Im(t)).
FIXME: this part of code is not 100% rigorous, since we don't consider
rounding errors.
*/
mpc_init2 (u, 64);
mpfr_const_pi (MPC_RE(u), GMP_RNDN);
mpfr_div_2exp (MPC_RE(u), MPC_RE(u), 1, GMP_RNDN); /* Pi/2 */
mpfr_remquo (MPC_RE(u), &Q, MPC_IM(t), MPC_RE(u), GMP_RNDN);
if (mpfr_sgn (MPC_RE(u)) < 0)
Q--; /* corresponds to positive remainder */
mpfr_set_ui (MPC_RE(z), 0, GMP_RNDN);
mpfr_set_ui (MPC_IM(z), 0, GMP_RNDN);
switch (Q & 3)
{
case 0: /* first quadrant: round to (+0 +0) */
ret = MPC_INEX(-1, -1);
break;
case 1: /* second quadrant: round to (-0 +0) */
mpfr_neg (MPC_RE(z), MPC_RE(z), GMP_RNDN);
ret = MPC_INEX(1, -1);
break;
case 2: /* third quadrant: round to (-0 -0) */
mpfr_neg (MPC_RE(z), MPC_RE(z), GMP_RNDN);
mpfr_neg (MPC_IM(z), MPC_IM(z), GMP_RNDN);
ret = MPC_INEX(1, 1);
break;
case 3: /* fourth quadrant: round to (+0 -0) */
mpfr_neg (MPC_IM(z), MPC_IM(z), GMP_RNDN);
ret = MPC_INEX(-1, 1);
break;
}
goto clear_t_and_u;
overflow:
/* If we have an overflow, we know that |z| is too large to be
represented, but depending on arg(z), we should return +/-Inf +/- I*Inf.
We assume t is the approximation of y*log(x), thus we want
exp(t) = exp(Re(t))+exp(I*Im(t)).
FIXME: this part of code is not 100% rigorous, since we don't consider
rounding errors.
*/
mpc_init2 (u, 64);
mpfr_const_pi (MPC_RE(u), GMP_RNDN);
mpfr_div_2exp (MPC_RE(u), MPC_RE(u), 1, GMP_RNDN); /* Pi/2 */
/* the quotient is rounded to the nearest integer in mpfr_remquo */
mpfr_remquo (MPC_RE(u), &Q, MPC_IM(t), MPC_RE(u), GMP_RNDN);
if (mpfr_sgn (MPC_RE(u)) < 0)
Q--; /* corresponds to positive remainder */
switch (Q & 3)
{
case 0: /* first quadrant */
mpfr_set_inf (MPC_RE(z), 1);
mpfr_set_inf (MPC_IM(z), 1);
ret = MPC_INEX(1, 1);
break;
case 1: /* second quadrant */
mpfr_set_inf (MPC_RE(z), -1);
mpfr_set_inf (MPC_IM(z), 1);
ret = MPC_INEX(-1, 1);
break;
case 2: /* third quadrant */
mpfr_set_inf (MPC_RE(z), -1);
mpfr_set_inf (MPC_IM(z), -1);
ret = MPC_INEX(-1, -1);
break;
case 3: /* fourth quadrant */
mpfr_set_inf (MPC_RE(z), 1);
mpfr_set_inf (MPC_IM(z), -1);
ret = MPC_INEX(1, -1);
break;
}
clear_t_and_u:
mpc_clear (t);
mpc_clear (u);
return ret;
}
/* Put in z the value of x^y, rounded according to 'rnd'.
Return the inexact flag in [0, 10]. */
int
mpc_pow (mpc_ptr z, mpc_srcptr x, mpc_srcptr y, mpc_rnd_t rnd)
{
int ret = -2, loop, x_real, x_imag, y_real, z_real = 0, z_imag = 0;
mpc_t t, u;
mpfr_prec_t p, pr, pi, maxprec;
int saved_underflow, saved_overflow;
/* save the underflow or overflow flags from MPFR */
saved_underflow = mpfr_underflow_p ();
saved_overflow = mpfr_overflow_p ();
x_real = mpfr_zero_p (mpc_imagref(x));
y_real = mpfr_zero_p (mpc_imagref(y));
if (y_real && mpfr_zero_p (mpc_realref(y))) /* case y zero */
{
if (x_real && mpfr_zero_p (mpc_realref(x)))
{
/* we define 0^0 to be (1, +0) since the real part is
coherent with MPFR where 0^0 gives 1, and the sign of the
imaginary part cannot be determined */
mpc_set_ui_ui (z, 1, 0, MPC_RNDNN);
return 0;
}
else /* x^0 = 1 +/- i*0 even for x=NaN see algorithms.tex for the
sign of zero */
{
mpfr_t n;
int inex, cx1;
int sign_zi;
/* cx1 < 0 if |x| < 1
cx1 = 0 if |x| = 1
cx1 > 0 if |x| > 1
*/
mpfr_init (n);
inex = mpc_norm (n, x, MPFR_RNDN);
cx1 = mpfr_cmp_ui (n, 1);
if (cx1 == 0 && inex != 0)
cx1 = -inex;
sign_zi = (cx1 < 0 && mpfr_signbit (mpc_imagref (y)) == 0)
|| (cx1 == 0
&& mpfr_signbit (mpc_imagref (x)) != mpfr_signbit (mpc_realref (y)))
|| (cx1 > 0 && mpfr_signbit (mpc_imagref (y)));
/* warning: mpc_set_ui_ui does not set Im(z) to -0 if Im(rnd)=RNDD */
ret = mpc_set_ui_ui (z, 1, 0, rnd);
if (MPC_RND_IM (rnd) == MPFR_RNDD || sign_zi)
mpc_conj (z, z, MPC_RNDNN);
mpfr_clear (n);
return ret;
}
}
if (!mpc_fin_p (x) || !mpc_fin_p (y))
{
/* special values: exp(y*log(x)) */
mpc_init2 (u, 2);
mpc_log (u, x, MPC_RNDNN);
mpc_mul (u, u, y, MPC_RNDNN);
ret = mpc_exp (z, u, rnd);
mpc_clear (u);
goto end;
}
if (x_real) /* case x real */
{
if (mpfr_zero_p (mpc_realref(x))) /* x is zero */
{
/* special values: exp(y*log(x)) */
mpc_init2 (u, 2);
mpc_log (u, x, MPC_RNDNN);
mpc_mul (u, u, y, MPC_RNDNN);
ret = mpc_exp (z, u, rnd);
mpc_clear (u);
goto end;
}
/* Special case 1^y = 1 */
if (mpfr_cmp_ui (mpc_realref(x), 1) == 0)
{
int s1, s2;
s1 = mpfr_signbit (mpc_realref (y));
s2 = mpfr_signbit (mpc_imagref (x));
ret = mpc_set_ui (z, +1, rnd);
/* the sign of the zero imaginary part is known in some cases (see
algorithm.tex). In such cases we have
(x +s*0i)^(y+/-0i) = x^y + s*sign(y)*0i
where s = +/-1. We extend here this rule to fix the sign of the
zero part.
Note that the sign must also be set explicitly when rnd=RNDD
because mpfr_set_ui(z_i, 0, rnd) always sets z_i to +0.
*/
if (MPC_RND_IM (rnd) == MPFR_RNDD || s1 != s2)
mpc_conj (z, z, MPC_RNDNN);
goto end;
}
/* x^y is real when:
(a) x is real and y is integer
(b) x is real non-negative and y is real */
if (y_real && (mpfr_integer_p (mpc_realref(y)) ||
mpfr_cmp_ui (mpc_realref(x), 0) >= 0))
{
int s1, s2;
s1 = mpfr_signbit (mpc_realref (y));
s2 = mpfr_signbit (mpc_imagref (x));
ret = mpfr_pow (mpc_realref(z), mpc_realref(x), mpc_realref(y), MPC_RND_RE(rnd));
ret = MPC_INEX(ret, mpfr_set_ui (mpc_imagref(z), 0, MPC_RND_IM(rnd)));
/* the sign of the zero imaginary part is known in some cases
(see algorithm.tex). In such cases we have (x +s*0i)^(y+/-0i)
= x^y + s*sign(y)*0i where s = +/-1.
We extend here this rule to fix the sign of the zero part.
Note that the sign must also be set explicitly when rnd=RNDD
because mpfr_set_ui(z_i, 0, rnd) always sets z_i to +0.
*/
if (MPC_RND_IM(rnd) == MPFR_RNDD || s1 != s2)
mpfr_neg (mpc_imagref(z), mpc_imagref(z), MPC_RND_IM(rnd));
goto end;
}
/* (-1)^(n+I*t) is real for n integer and t real */
if (mpfr_cmp_si (mpc_realref(x), -1) == 0 && mpfr_integer_p (mpc_realref(y)))
z_real = 1;
/* for x real, x^y is imaginary when:
(a) x is negative and y is half-an-integer
(b) x = -1 and Re(y) is half-an-integer
*/
if ((mpfr_cmp_ui (mpc_realref(x), 0) < 0) && is_odd (mpc_realref(y), 1)
&& (y_real || mpfr_cmp_si (mpc_realref(x), -1) == 0))
z_imag = 1;
}
else /* x non real */
/* I^(t*I) and (-I)^(t*I) are real for t real,
I^(n+t*I) and (-I)^(n+t*I) are real for n even and t real, and
I^(n+t*I) and (-I)^(n+t*I) are imaginary for n odd and t real
(s*I)^n is real for n even and imaginary for n odd */
if ((mpc_cmp_si_si (x, 0, 1) == 0 || mpc_cmp_si_si (x, 0, -1) == 0 ||
(mpfr_cmp_ui (mpc_realref(x), 0) == 0 && y_real)) &&
mpfr_integer_p (mpc_realref(y)))
{ /* x is I or -I, and Re(y) is an integer */
if (is_odd (mpc_realref(y), 0))
z_imag = 1; /* Re(y) odd: z is imaginary */
else
z_real = 1; /* Re(y) even: z is real */
}
else /* (t+/-t*I)^(2n) is imaginary for n odd and real for n even */
if (mpfr_cmpabs (mpc_realref(x), mpc_imagref(x)) == 0 && y_real &&
mpfr_integer_p (mpc_realref(y)) && is_odd (mpc_realref(y), 0) == 0)
{
if (is_odd (mpc_realref(y), -1)) /* y/2 is odd */
z_imag = 1;
else
z_real = 1;
}
pr = mpfr_get_prec (mpc_realref(z));
pi = mpfr_get_prec (mpc_imagref(z));
p = (pr > pi) ? pr : pi;
p += 12; /* experimentally, seems to give less than 10% of failures in
Ziv's strategy; probably wrong now since q is not computed */
if (p < 64)
p = 64;
mpc_init2 (u, p);
mpc_init2 (t, p);
pr += MPC_RND_RE(rnd) == MPFR_RNDN;
pi += MPC_RND_IM(rnd) == MPFR_RNDN;
maxprec = MPC_MAX_PREC (z);
x_imag = mpfr_zero_p (mpc_realref(x));
for (loop = 0;; loop++)
{
int ret_exp;
mpfr_exp_t dr, di;
mpfr_prec_t q;
mpc_log (t, x, MPC_RNDNN);
mpc_mul (t, t, y, MPC_RNDNN);
/* Compute q such that |Re (y log x)|, |Im (y log x)| < 2^q.
We recompute it at each loop since we might get different
bounds if the precision is not enough. */
q = mpfr_get_exp (mpc_realref(t)) > 0 ? mpfr_get_exp (mpc_realref(t)) : 0;
if (mpfr_get_exp (mpc_imagref(t)) > (mpfr_exp_t) q)
q = mpfr_get_exp (mpc_imagref(t));
mpfr_clear_overflow ();
mpfr_clear_underflow ();
ret_exp = mpc_exp (u, t, MPC_RNDNN);
if (mpfr_underflow_p () || mpfr_overflow_p ()) {
/* under- and overflow flags are set by mpc_exp */
mpc_set (z, u, MPC_RNDNN);
ret = ret_exp;
goto exact;
}
/* Since the error bound is global, we have to take into account the
exponent difference between the real and imaginary parts. We assume
either the real or the imaginary part of u is not zero.
*/
dr = mpfr_zero_p (mpc_realref(u)) ? mpfr_get_exp (mpc_imagref(u))
: mpfr_get_exp (mpc_realref(u));
di = mpfr_zero_p (mpc_imagref(u)) ? dr : mpfr_get_exp (mpc_imagref(u));
if (dr > di)
{
di = dr - di;
dr = 0;
}
else
{
dr = di - dr;
di = 0;
}
/* the term -3 takes into account the factor 4 in the complex error
(see algorithms.tex) plus one due to the exponent difference: if
z = a + I*b, where the relative error on z is at most 2^(-p), and
EXP(a) = EXP(b) + k, the relative error on b is at most 2^(k-p) */
if ((z_imag || (p > q + 3 + dr && mpfr_can_round (mpc_realref(u), p - q - 3 - dr, MPFR_RNDN, MPFR_RNDZ, pr))) &&
(z_real || (p > q + 3 + di && mpfr_can_round (mpc_imagref(u), p - q - 3 - di, MPFR_RNDN, MPFR_RNDZ, pi))))
break;
/* if Re(u) is not known to be zero, assume it is a normal number, i.e.,
neither zero, Inf or NaN, otherwise we might enter an infinite loop */
MPC_ASSERT (z_imag || mpfr_number_p (mpc_realref(u)));
/* idem for Im(u) */
MPC_ASSERT (z_real || mpfr_number_p (mpc_imagref(u)));
if (ret == -2) /* we did not yet call mpc_pow_exact, or it aborted
because intermediate computations had > maxprec bits */
{
/* check exact cases (see algorithms.tex) */
if (y_real)
{
maxprec *= 2;
ret = mpc_pow_exact (z, x, mpc_realref(y), rnd, maxprec);
if (ret != -1 && ret != -2)
goto exact;
}
p += dr + di + 64;
}
else
p += p / 2;
mpc_set_prec (t, p);
mpc_set_prec (u, p);
}
if (z_real)
{
/* When the result is real (see algorithm.tex for details),
Im(x^y) =
+ sign(imag(y))*0i, if |x| > 1
+ sign(imag(x))*sign(real(y))*0i, if |x| = 1
- sign(imag(y))*0i, if |x| < 1
*/
mpfr_t n;
int inex, cx1;
int sign_zi, sign_rex, sign_imx;
/* cx1 < 0 if |x| < 1
cx1 = 0 if |x| = 1
cx1 > 0 if |x| > 1
*/
sign_rex = mpfr_signbit (mpc_realref (x));
sign_imx = mpfr_signbit (mpc_imagref (x));
mpfr_init (n);
inex = mpc_norm (n, x, MPFR_RNDN);
cx1 = mpfr_cmp_ui (n, 1);
if (cx1 == 0 && inex != 0)
cx1 = -inex;
sign_zi = (cx1 < 0 && mpfr_signbit (mpc_imagref (y)) == 0)
|| (cx1 == 0 && sign_imx != mpfr_signbit (mpc_realref (y)))
|| (cx1 > 0 && mpfr_signbit (mpc_imagref (y)));
/* copy RE(y) to n since if z==y we will destroy Re(y) below */
mpfr_set_prec (n, mpfr_get_prec (mpc_realref (y)));
mpfr_set (n, mpc_realref (y), MPFR_RNDN);
ret = mpfr_set (mpc_realref(z), mpc_realref(u), MPC_RND_RE(rnd));
if (y_real && (x_real || x_imag))
{
/* FIXME: with y_real we assume Im(y) is really 0, which is the case
for example when y comes from pow_fr, but in case Im(y) is +0 or
-0, we might get different results */
mpfr_set_ui (mpc_imagref (z), 0, MPC_RND_IM (rnd));
fix_sign (z, sign_rex, sign_imx, n);
ret = MPC_INEX(ret, 0); /* imaginary part is exact */
}
else
{
ret = MPC_INEX (ret, mpfr_set_ui (mpc_imagref (z), 0, MPC_RND_IM (rnd)));
/* warning: mpfr_set_ui does not set Im(z) to -0 if Im(rnd) = RNDD */
if (MPC_RND_IM (rnd) == MPFR_RNDD || sign_zi)
mpc_conj (z, z, MPC_RNDNN);
}
mpfr_clear (n);
}
else if (z_imag)
{
ret = mpfr_set (mpc_imagref(z), mpc_imagref(u), MPC_RND_IM(rnd));
/* if z is imaginary and y real, then x cannot be real */
if (y_real && x_imag)
{
int sign_rex = mpfr_signbit (mpc_realref (x));
/* If z overlaps with y we set Re(z) before checking Re(y) below,
but in that case y=0, which was dealt with above. */
mpfr_set_ui (mpc_realref (z), 0, MPC_RND_RE (rnd));
/* Note: fix_sign only does something when y is an integer,
then necessarily y = 1 or 3 (mod 4), and in that case the
sign of Im(x) is irrelevant. */
fix_sign (z, sign_rex, 0, mpc_realref (y));
ret = MPC_INEX(0, ret);
}
else
ret = MPC_INEX(mpfr_set_ui (mpc_realref(z), 0, MPC_RND_RE(rnd)), ret);
}
else
ret = mpc_set (z, u, rnd);
exact:
mpc_clear (t);
mpc_clear (u);
/* restore underflow and overflow flags from MPFR */
if (saved_underflow)
mpfr_set_underflow ();
if (saved_overflow)
mpfr_set_overflow ();
end:
return ret;
}
mpcomplex mpcomplex::log2() {
mpc_log(mpc_val, mpc_val, default_rnd);
return *this;
}
