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/* mpc_norm -- Square of the norm of a complex number.
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Copyright (C) INRIA, 2002, 2005, 2008, 2009, 2010
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This file is part of the MPC Library.
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The MPC Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The MPC Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPC Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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MA 02111-1307, USA. */
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#include "mpc-impl.h"
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/* the rounding mode is mpfr_rnd_t here since we return an mpfr number */
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int
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mpc_norm (mpfr_ptr a, mpc_srcptr b, mpfr_rnd_t rnd)
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{
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mpfr_t u, v;
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mpfr_prec_t prec;
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int inexact, overflow, underflow;
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prec = mpfr_get_prec (a);
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/* handling of special values; consistent with abs in that
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norm = abs^2; so norm (+-inf, nan) = norm (nan, +-inf) = +inf */
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if ( (mpfr_nan_p (MPC_RE (b)) || mpfr_nan_p (MPC_IM (b)))
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|| (mpfr_inf_p (MPC_RE (b)) || mpfr_inf_p (MPC_IM (b))))
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return mpc_abs (a, b, rnd);
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mpfr_init (u);
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mpfr_init (v);
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if (!mpfr_zero_p(MPC_RE(b)) && !mpfr_zero_p(MPC_IM(b)) &&
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2 * SAFE_ABS (mpfr_exp_t,
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mpfr_get_exp (MPC_RE (b)) - mpfr_get_exp (MPC_IM (b)))
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> (mpfr_exp_t)prec)
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/* If real and imaginary part have very different magnitudes, then the */
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/* generic code increases the precision too much. Instead, compute the */
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/* squarings _exactly_. */
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{
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mpfr_set_prec (u, 2 * MPC_PREC_RE (b));
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mpfr_set_prec (v, 2 * MPC_PREC_IM (b));
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mpfr_sqr (u, MPC_RE (b), GMP_RNDN);
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mpfr_sqr (v, MPC_IM (b), GMP_RNDN);
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inexact = mpfr_add (a, u, v, rnd);
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}
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else if (mpfr_zero_p(MPC_RE(b)) && mpfr_zero_p(MPC_IM(b)))
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{
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inexact = mpfr_set_ui (a, 0, rnd);
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}
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else
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{
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do
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{
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prec += mpc_ceil_log2 (prec) + 3;
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mpfr_set_prec (u, prec);
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mpfr_set_prec (v, prec);
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inexact = mpfr_sqr (u, MPC_RE(b), GMP_RNDN); /* err<=1/2ulp */
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inexact |= mpfr_sqr (v, MPC_IM(b), GMP_RNDN); /* err<=1/2ulp*/
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inexact |= mpfr_add (u, u, v, GMP_RNDN); /* err <= 3/2 ulps */
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overflow = mpfr_inf_p (u);
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underflow = mpfr_zero_p (u);
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}
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while (!overflow && !underflow && inexact &&
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mpfr_can_round (u, prec - 2, GMP_RNDN, rnd, mpfr_get_prec (a)) == 0);
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inexact |= mpfr_set (a, u, rnd);
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if (overflow)
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inexact = 1;
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if (underflow)
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inexact = -1;
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}
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mpfr_clear (u);
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mpfr_clear (v);
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return inexact;
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}
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