92 lines
2.6 KiB
C
92 lines
2.6 KiB
C
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/* This example was presented at the CNC'2 summer school on MPFR and MPC at
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* LORIA, Nancy, France. It shows how one can use different rounding modes.
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* This example implements the OddRoundedAdd algorithm, which returns the
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* sum z = x + y rounded-to-odd:
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* * RO(z) = z if z is exactly representable;
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* * otherwise RO(z) is the value among RD(z) and RU(z) whose
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* least significant bit is a one.
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*/
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/*
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Copyright 2009-2016 Free Software Foundation, Inc.
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Contributed by the AriC and Caramba projects, INRIA.
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This file is part of the GNU MPFR Library.
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The GNU MPFR 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 3 of the License, or (at your
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option) any later version.
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The GNU MPFR 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 GNU MPFR Library; see the file COPYING.LESSER. If not, see
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http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
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51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <gmp.h>
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#include <mpfr.h>
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#define LIST x, y, d, u, e, z
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int main (int argc, char **argv)
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{
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mpfr_t LIST;
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mpfr_prec_t prec;
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int pprec; /* will be prec - 1 for mpfr_printf */
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if (argc != 4)
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{
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fprintf (stderr, "Usage: rndo-add <prec> <x> <y>\n");
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exit (1);
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}
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prec = atoi (argv[1]);
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if (prec < 2)
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{
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fprintf (stderr, "rndo-add: bad precision\n");
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exit (1);
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}
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pprec = prec - 1;
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mpfr_inits2 (prec, LIST, (mpfr_ptr) 0);
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if (mpfr_set_str (x, argv[2], 0, MPFR_RNDN))
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{
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fprintf (stderr, "rndo-add: bad x value\n");
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exit (1);
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}
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mpfr_printf ("x = %.*Rb\n", pprec, x);
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if (mpfr_set_str (y, argv[3], 0, MPFR_RNDN))
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{
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fprintf (stderr, "rndo-add: bad y value\n");
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exit (1);
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}
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mpfr_printf ("y = %.*Rb\n", pprec, y);
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mpfr_add (d, x, y, MPFR_RNDD);
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mpfr_printf ("d = %.*Rb\n", pprec, d);
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mpfr_add (u, x, y, MPFR_RNDU);
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mpfr_printf ("u = %.*Rb\n", pprec, u);
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mpfr_add (e, d, u, MPFR_RNDN);
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mpfr_div_2ui (e, e, 1, MPFR_RNDN);
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mpfr_printf ("e = %.*Rb\n", pprec, e);
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mpfr_sub (z, u, e, MPFR_RNDN);
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mpfr_add (z, z, d, MPFR_RNDN);
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mpfr_printf ("z = %.*Rb\n", pprec, z);
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mpfr_clears (LIST, (mpfr_ptr) 0);
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return 0;
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}
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