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/* mpc_exp -- exponential of a complex number.
Copyright (C) 2002, 2009, 2010, 2011 INRIA
This file is part of GNU MPC.
GNU MPC is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the
Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
GNU MPC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
more details.
You should have received a copy of the GNU Lesser General Public License
along with this program. If not, see http://www.gnu.org/licenses/ .
*/
#include "mpc-impl.h"
int
mpc_exp (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd)
{
mpfr_t x, y, z;
mpfr_prec_t prec;
int ok = 0;
int inex_re, inex_im;
int saved_underflow, saved_overflow;
/* special values */
if (mpfr_nan_p (mpc_realref (op)) || mpfr_nan_p (mpc_imagref (op)))
/* NaNs
exp(nan +i*y) = nan -i*0 if y = -0,
nan +i*0 if y = +0,
nan +i*nan otherwise
exp(x+i*nan) = +/-0 +/-i*0 if x=-inf,
+/-inf +i*nan if x=+inf,
nan +i*nan otherwise */
{
if (mpfr_zero_p (mpc_imagref (op)))
return mpc_set (rop, op, MPC_RNDNN);
if (mpfr_inf_p (mpc_realref (op)))
{
if (mpfr_signbit (mpc_realref (op)))
return mpc_set_ui_ui (rop, 0, 0, MPC_RNDNN);
else
{
mpfr_set_inf (mpc_realref (rop), +1);
mpfr_set_nan (mpc_imagref (rop));
return MPC_INEX(0, 0); /* Inf/NaN are exact */
}
}
mpfr_set_nan (mpc_realref (rop));
mpfr_set_nan (mpc_imagref (rop));
return MPC_INEX(0, 0); /* NaN is exact */
}
if (mpfr_zero_p (mpc_imagref(op)))
/* special case when the input is real
exp(x-i*0) = exp(x) -i*0, even if x is NaN
exp(x+i*0) = exp(x) +i*0, even if x is NaN */
{
inex_re = mpfr_exp (mpc_realref(rop), mpc_realref(op), MPC_RND_RE(rnd));
inex_im = mpfr_set (mpc_imagref(rop), mpc_imagref(op), MPC_RND_IM(rnd));
return MPC_INEX(inex_re, inex_im);
}
if (mpfr_zero_p (mpc_realref (op)))
/* special case when the input is imaginary */
{
inex_re = mpfr_cos (mpc_realref (rop), mpc_imagref (op), MPC_RND_RE(rnd));
inex_im = mpfr_sin (mpc_imagref (rop), mpc_imagref (op), MPC_RND_IM(rnd));
return MPC_INEX(inex_re, inex_im);
}
if (mpfr_inf_p (mpc_realref (op)))
/* real part is an infinity,
exp(-inf +i*y) = 0*(cos y +i*sin y)
exp(+inf +i*y) = +/-inf +i*nan if y = +/-inf
+inf*(cos y +i*sin y) if 0 < |y| < inf */
{
mpfr_t n;
mpfr_init2 (n, 2);
if (mpfr_signbit (mpc_realref (op)))
mpfr_set_ui (n, 0, GMP_RNDN);
else
mpfr_set_inf (n, +1);
if (mpfr_inf_p (mpc_imagref (op)))
{
inex_re = mpfr_set (mpc_realref (rop), n, GMP_RNDN);
if (mpfr_signbit (mpc_realref (op)))
inex_im = mpfr_set (mpc_imagref (rop), n, GMP_RNDN);
else
{
mpfr_set_nan (mpc_imagref (rop));
inex_im = 0; /* NaN is exact */
}
}
else
{
mpfr_t c, s;
mpfr_init2 (c, 2);
mpfr_init2 (s, 2);
mpfr_sin_cos (s, c, mpc_imagref (op), GMP_RNDN);
inex_re = mpfr_copysign (mpc_realref (rop), n, c, GMP_RNDN);
inex_im = mpfr_copysign (mpc_imagref (rop), n, s, GMP_RNDN);
mpfr_clear (s);
mpfr_clear (c);
}
mpfr_clear (n);
return MPC_INEX(inex_re, inex_im);
}
if (mpfr_inf_p (mpc_imagref (op)))
/* real part is finite non-zero number, imaginary part is an infinity */
{
mpfr_set_nan (mpc_realref (rop));
mpfr_set_nan (mpc_imagref (rop));
return MPC_INEX(0, 0); /* NaN is exact */
}
/* from now on, both parts of op are regular numbers */
prec = MPC_MAX_PREC(rop)
+ MPC_MAX (MPC_MAX (-mpfr_get_exp (mpc_realref (op)), 0),
-mpfr_get_exp (mpc_imagref (op)));
/* When op is close to 0, then exp is close to 1+Re(op), while
cos is close to 1-Im(op); to decide on the ternary value of exp*cos,
we need a high enough precision so that none of exp or cos is
computed as 1. */
mpfr_init2 (x, 2);
mpfr_init2 (y, 2);
mpfr_init2 (z, 2);
/* save the underflow or overflow flags from MPFR */
saved_underflow = mpfr_underflow_p ();
saved_overflow = mpfr_overflow_p ();
do
{
prec += mpc_ceil_log2 (prec) + 5;
mpfr_set_prec (x, prec);
mpfr_set_prec (y, prec);
mpfr_set_prec (z, prec);
/* FIXME: x may overflow so x.y does overflow too, while Re(exp(op))
could be represented in the precision of rop. */
mpfr_clear_overflow ();
mpfr_clear_underflow ();
mpfr_exp (x, mpc_realref(op), GMP_RNDN); /* error <= 0.5ulp */
mpfr_sin_cos (z, y, mpc_imagref(op), GMP_RNDN); /* errors <= 0.5ulp */
mpfr_mul (y, y, x, GMP_RNDN); /* error <= 2ulp */
ok = mpfr_overflow_p () || mpfr_zero_p (x)
|| mpfr_can_round (y, prec - 2, GMP_RNDN, GMP_RNDZ,
MPC_PREC_RE(rop) + (MPC_RND_RE(rnd) == GMP_RNDN));
if (ok) /* compute imaginary part */
{
mpfr_mul (z, z, x, GMP_RNDN);
ok = mpfr_overflow_p () || mpfr_zero_p (x)
|| mpfr_can_round (z, prec - 2, GMP_RNDN, GMP_RNDZ,
MPC_PREC_IM(rop) + (MPC_RND_IM(rnd) == GMP_RNDN));
}
}
while (ok == 0);
inex_re = mpfr_set (mpc_realref(rop), y, MPC_RND_RE(rnd));
inex_im = mpfr_set (mpc_imagref(rop), z, MPC_RND_IM(rnd));
if (mpfr_overflow_p ()) {
/* overflow in real exponential, inex is sign of infinite result */
inex_re = mpfr_sgn (y);
inex_im = mpfr_sgn (z);
}
else if (mpfr_underflow_p ()) {
/* underflow in real exponential, inex is opposite of sign of 0 result */
inex_re = (mpfr_signbit (y) ? +1 : -1);
inex_im = (mpfr_signbit (z) ? +1 : -1);
}
mpfr_clear (x);
mpfr_clear (y);
mpfr_clear (z);
/* restore underflow and overflow flags from MPFR */
if (saved_underflow)
mpfr_set_underflow ();
if (saved_overflow)
mpfr_set_overflow ();
return MPC_INEX(inex_re, inex_im);
}
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