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.
102 lines
2.8 KiB
C
102 lines
2.8 KiB
C
/* mpfr_cmp_ui_2exp -- compare a floating-point number with an unsigned
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machine integer multiplied by a power of 2
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Copyright 1999, 2001, 2002, 2003, 2004, 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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#define MPFR_NEED_LONGLONG_H
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#include "mpfr-impl.h"
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/* returns a positive value if b > i*2^f,
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a negative value if b < i*2^f,
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zero if b = i*2^f.
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b must not be NaN
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*/
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int
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mpfr_cmp_ui_2exp (mpfr_srcptr b, unsigned long int i, mpfr_exp_t f)
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{
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if (MPFR_UNLIKELY( MPFR_IS_SINGULAR(b) ))
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{
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if (MPFR_IS_NAN (b))
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{
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MPFR_SET_ERANGE ();
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return 0;
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}
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else if (MPFR_IS_INF(b))
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return MPFR_INT_SIGN (b);
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else /* since b cannot be NaN, b=0 here */
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return i != 0 ? -1 : 0;
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}
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if (MPFR_IS_NEG (b))
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return -1;
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/* now b > 0 */
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else if (MPFR_UNLIKELY(i == 0))
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return 1;
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else /* b > 0, i > 0 */
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{
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mpfr_exp_t e;
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int k;
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mp_size_t bn;
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mp_limb_t c, *bp;
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/* i must be representable in a mp_limb_t */
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MPFR_ASSERTN(i == (mp_limb_t) i);
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e = MPFR_GET_EXP (b); /* 2^(e-1) <= b < 2^e */
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if (e <= f)
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return -1;
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if (f < MPFR_EMAX_MAX - GMP_NUMB_BITS &&
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e > f + GMP_NUMB_BITS)
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return 1;
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/* now f < e <= f + GMP_NUMB_BITS */
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c = (mp_limb_t) i;
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count_leading_zeros(k, c);
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if ((int) (e - f) > GMP_NUMB_BITS - k)
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return 1;
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if ((int) (e - f) < GMP_NUMB_BITS - k)
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return -1;
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/* now b and i*2^f have the same exponent */
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c <<= k;
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bn = (MPFR_PREC(b) - 1) / GMP_NUMB_BITS;
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bp = MPFR_MANT(b);
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if (bp[bn] > c)
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return 1;
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if (bp[bn] < c)
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return -1;
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/* most significant limbs agree, check remaining limbs from b */
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while (bn > 0)
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if (bp[--bn] != 0)
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return 1;
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return 0;
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}
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}
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#undef mpfr_cmp_ui
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int
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mpfr_cmp_ui (mpfr_srcptr b, unsigned long int i)
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{
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return mpfr_cmp_ui_2exp (b, i, 0);
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}
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