efee5258bc
The MPFR library is a C library for multiple-precision floating-point computations with exact rounding (also called correct rounding). It is based on the GMP multiple-precision library and should replace the MPF class in further releases of GMP. GCC >= 4.2 requires MPFR.
60 lines
2.1 KiB
C
60 lines
2.1 KiB
C
/* mpfr_div_2ui -- divide a floating-point number by a power of two
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Copyright 1999, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
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Contributed by the Arenaire and Cacao 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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#include "mpfr-impl.h"
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int
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mpfr_div_2ui (mpfr_ptr y, mpfr_srcptr x, unsigned long n, mpfr_rnd_t rnd_mode)
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{
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int inexact;
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MPFR_LOG_FUNC (("x[%#R]=%R n=%lu rnd=%d", x, x, n, rnd_mode),
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("y[%#R]=%R inexact=%d", y, y, inexact));
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if (MPFR_UNLIKELY (MPFR_IS_SINGULAR (x)))
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return mpfr_set (y, x, rnd_mode);
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else
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{
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mpfr_exp_t exp = MPFR_GET_EXP (x);
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mpfr_uexp_t diffexp;
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MPFR_SETRAW (inexact, y, x, exp, rnd_mode);
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diffexp = (mpfr_uexp_t) exp - (mpfr_uexp_t) (__gmpfr_emin - 1);
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if (MPFR_UNLIKELY (n >= diffexp)) /* exp - n <= emin - 1 */
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{
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if (rnd_mode == MPFR_RNDN &&
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(n > diffexp || (inexact >= 0 && mpfr_powerof2_raw (y))))
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rnd_mode = MPFR_RNDZ;
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return mpfr_underflow (y, rnd_mode, MPFR_SIGN (y));
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}
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/* exp - n >= emin (no underflow, no integer overflow) */
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while (n > LONG_MAX)
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{
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n -= LONG_MAX;
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exp -= LONG_MAX; /* note: signed values */
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}
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MPFR_SET_EXP (y, exp - (long) n);
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}
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MPFR_RET (inexact);
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}
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