mpfr/dist/exceptions.c

/* Exception flags and utilities.

Copyright 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
Contributed by the Arenaire and Cacao projects, INRIA.

This file is part of the GNU MPFR Library.

The GNU MPFR Library 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.

The GNU MPFR Library 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 the GNU MPFR Library; see the file COPYING.LESSER.  If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */

#include "mpfr-impl.h"

unsigned int MPFR_THREAD_ATTR __gmpfr_flags = 0;

mpfr_exp_t MPFR_THREAD_ATTR __gmpfr_emin = MPFR_EMIN_DEFAULT;
mpfr_exp_t MPFR_THREAD_ATTR __gmpfr_emax = MPFR_EMAX_DEFAULT;

#undef mpfr_get_emin

mpfr_exp_t
mpfr_get_emin (void)
{
  return __gmpfr_emin;
}

#undef mpfr_set_emin

int
mpfr_set_emin (mpfr_exp_t exponent)
{
  if (exponent >= MPFR_EMIN_MIN && exponent <= MPFR_EMIN_MAX)
    {
      __gmpfr_emin = exponent;
      return 0;
    }
  else
    {
      return 1;
    }
}

mpfr_exp_t
mpfr_get_emin_min (void)
{
  return MPFR_EMIN_MIN;
}

mpfr_exp_t
mpfr_get_emin_max (void)
{
  return MPFR_EMIN_MAX;
}

#undef mpfr_get_emax

mpfr_exp_t
mpfr_get_emax (void)
{
  return __gmpfr_emax;
}

#undef mpfr_set_emax

int
mpfr_set_emax (mpfr_exp_t exponent)
{
  if (exponent >= MPFR_EMAX_MIN && exponent <= MPFR_EMAX_MAX)
    {
      __gmpfr_emax = exponent;
      return 0;
    }
  else
    {
      return 1;
    }
}

mpfr_exp_t
mpfr_get_emax_min (void)
{
  return MPFR_EMAX_MIN;
}
mpfr_exp_t
mpfr_get_emax_max (void)
{
  return MPFR_EMAX_MAX;
}


#undef mpfr_clear_flags

void
mpfr_clear_flags (void)
{
  __gmpfr_flags = 0;
}

#undef mpfr_clear_underflow

void
mpfr_clear_underflow (void)
{
  __gmpfr_flags &= MPFR_FLAGS_ALL ^ MPFR_FLAGS_UNDERFLOW;
}

#undef mpfr_clear_overflow

void
mpfr_clear_overflow (void)
{
  __gmpfr_flags &= MPFR_FLAGS_ALL ^ MPFR_FLAGS_OVERFLOW;
}

#undef mpfr_clear_nanflag

void
mpfr_clear_nanflag (void)
{
  __gmpfr_flags &= MPFR_FLAGS_ALL ^ MPFR_FLAGS_NAN;
}

#undef mpfr_clear_inexflag

void
mpfr_clear_inexflag (void)
{
  __gmpfr_flags &= MPFR_FLAGS_ALL ^ MPFR_FLAGS_INEXACT;
}

#undef mpfr_clear_erangeflag

void
mpfr_clear_erangeflag (void)
{
  __gmpfr_flags &= MPFR_FLAGS_ALL ^ MPFR_FLAGS_ERANGE;
}

#undef mpfr_clear_underflow

void
mpfr_set_underflow (void)
{
  __gmpfr_flags |= MPFR_FLAGS_UNDERFLOW;
}

#undef mpfr_clear_overflow

void
mpfr_set_overflow (void)
{
  __gmpfr_flags |= MPFR_FLAGS_OVERFLOW;
}

#undef mpfr_clear_nanflag

void
mpfr_set_nanflag (void)
{
  __gmpfr_flags |= MPFR_FLAGS_NAN;
}

#undef mpfr_clear_inexflag

void
mpfr_set_inexflag (void)
{
  __gmpfr_flags |= MPFR_FLAGS_INEXACT;
}

#undef mpfr_clear_erangeflag

void
mpfr_set_erangeflag (void)
{
  __gmpfr_flags |= MPFR_FLAGS_ERANGE;
}


#undef mpfr_check_range

int
mpfr_check_range (mpfr_ptr x, int t, mpfr_rnd_t rnd_mode)
{
  if (MPFR_LIKELY( MPFR_IS_PURE_FP(x)) )
    { /* x is a non-zero FP */
      mpfr_exp_t exp = MPFR_EXP (x);  /* Do not use MPFR_GET_EXP */
      if (MPFR_UNLIKELY( exp < __gmpfr_emin) )
        {
          /* The following test is necessary because in the rounding to the
           * nearest mode, mpfr_underflow always rounds away from 0. In
           * this rounding mode, we need to round to 0 if:
           *   _ |x| < 2^(emin-2), or
           *   _ |x| = 2^(emin-2) and the absolute value of the exact
           *     result is <= 2^(emin-2).
           */
          if (rnd_mode == MPFR_RNDN &&
              (exp + 1 < __gmpfr_emin ||
               (mpfr_powerof2_raw(x) &&
                (MPFR_IS_NEG(x) ? t <= 0 : t >= 0))))
            rnd_mode = MPFR_RNDZ;
          return mpfr_underflow(x, rnd_mode, MPFR_SIGN(x));
        }
      if (MPFR_UNLIKELY( exp > __gmpfr_emax) )
        return mpfr_overflow (x, rnd_mode, MPFR_SIGN(x));
    }
  else if (MPFR_UNLIKELY (t != 0 && MPFR_IS_INF (x)))
    {
      /* We need to do the following because most MPFR functions are
       * implemented in the following way:
       *   Ziv's loop:
       *   | Compute an approximation to the result and an error bound.
       *   | Possible underflow/overflow detection -> return.
       *   | If can_round, break (exit the loop).
       *   | Otherwise, increase the working precision and loop.
       *   Round the approximation in the target precision.  <== See below
       *   Restore the flags (that could have been set due to underflows
       *   or overflows during the internal computations).
       *   Execute: return mpfr_check_range (...).
       * The problem is that an overflow could be generated when rounding the
       * approximation (in general, such an overflow could not be detected
       * earlier), and the overflow flag is lost when the flags are restored.
       * This can occur only when the rounding yields an exponent change
       * and the new exponent is larger than the maximum exponent, so that
       * an infinity is necessarily obtained.
       * So, the simplest solution is to detect this overflow case here in
       * mpfr_check_range, which is easy to do since the rounded result is
       * necessarily an inexact infinity.
       */
      __gmpfr_flags |= MPFR_FLAGS_OVERFLOW;
    }
  MPFR_RET (t);  /* propagate inexact ternary value, unlike most functions */
}

#undef mpfr_underflow_p

int
mpfr_underflow_p (void)
{
  return __gmpfr_flags & MPFR_FLAGS_UNDERFLOW;
}

#undef mpfr_overflow_p

int
mpfr_overflow_p (void)
{
  return __gmpfr_flags & MPFR_FLAGS_OVERFLOW;
}

#undef mpfr_nanflag_p

int
mpfr_nanflag_p (void)
{
  return __gmpfr_flags & MPFR_FLAGS_NAN;
}

#undef mpfr_inexflag_p

int
mpfr_inexflag_p (void)
{
  return __gmpfr_flags & MPFR_FLAGS_INEXACT;
}

#undef mpfr_erangeflag_p

int
mpfr_erangeflag_p (void)
{
  return __gmpfr_flags & MPFR_FLAGS_ERANGE;
}

/* #undef mpfr_underflow */

/* Note: In the rounding to the nearest mode, mpfr_underflow
   always rounds away from 0. In this rounding mode, you must call
   mpfr_underflow with rnd_mode = MPFR_RNDZ if the exact result
   is <= 2^(emin-2) in absolute value. */

int
mpfr_underflow (mpfr_ptr x, mpfr_rnd_t rnd_mode, int sign)
{
  int inex;

  MPFR_ASSERT_SIGN (sign);

  if (MPFR_IS_LIKE_RNDZ(rnd_mode, sign < 0))
    {
      MPFR_SET_ZERO(x);
      inex = -1;
    }
  else
    {
      mpfr_setmin (x, __gmpfr_emin);
      inex = 1;
    }
  MPFR_SET_SIGN(x, sign);
  __gmpfr_flags |= MPFR_FLAGS_INEXACT | MPFR_FLAGS_UNDERFLOW;
  return sign > 0 ? inex : -inex;
}

/* #undef mpfr_overflow */

int
mpfr_overflow (mpfr_ptr x, mpfr_rnd_t rnd_mode, int sign)
{
  int inex;

  MPFR_ASSERT_SIGN(sign);
  if (MPFR_IS_LIKE_RNDZ(rnd_mode, sign < 0))
    {
      mpfr_setmax (x, __gmpfr_emax);
      inex = -1;
    }
  else
    {
      MPFR_SET_INF(x);
      inex = 1;
    }
  MPFR_SET_SIGN(x,sign);
  __gmpfr_flags |= MPFR_FLAGS_INEXACT | MPFR_FLAGS_OVERFLOW;
  return sign > 0 ? inex : -inex;
}