Ejemplo n.º 1
0
Archivo: tests.c Proyecto: Kirija/XPIR
/* generate a random limb */
mp_limb_t
randlimb (void)
{
  mp_limb_t limb;

  mpfr_rand_raw (&limb, RANDS, GMP_NUMB_BITS);
  return limb;
}
Ejemplo n.º 2
0
/* generate one random bit */
static int
random_rounding_bit (gmp_randstate_t rstate)
{
  mp_limb_t r;

  mpfr_rand_raw (&r, rstate, 1);
  return r & MPFR_LIMB_ONE;
}
Ejemplo n.º 3
0
int
mpfr_urandomb (mpfr_ptr rop, gmp_randstate_t rstate)
{
    mpfr_limb_ptr rp;
    mpfr_prec_t nbits;
    mp_size_t nlimbs;
    mp_size_t k; /* number of high zero limbs */
    mpfr_exp_t exp;
    int cnt;

    rp = MPFR_MANT (rop);
    nbits = MPFR_PREC (rop);
    nlimbs = MPFR_LIMB_SIZE (rop);
    MPFR_SET_POS (rop);
    cnt = nlimbs * GMP_NUMB_BITS - nbits;

    /* Uniform non-normalized significand */
    /* generate exactly nbits so that the random generator stays in the same
       state, independent of the machine word size GMP_NUMB_BITS */
    mpfr_rand_raw (rp, rstate, nbits);
    if (MPFR_LIKELY (cnt != 0)) /* this will put the low bits to zero */
        mpn_lshift (rp, rp, nlimbs, cnt);

    /* Count the null significant limbs and remaining limbs */
    exp = 0;
    k = 0;
    while (nlimbs != 0 && rp[nlimbs - 1] == 0)
    {
        k ++;
        nlimbs --;
        exp -= GMP_NUMB_BITS;
    }

    if (MPFR_LIKELY (nlimbs != 0)) /* otherwise value is zero */
    {
        count_leading_zeros (cnt, rp[nlimbs - 1]);
        /* Normalization */
        if (mpfr_set_exp (rop, exp - cnt))
        {
            /* If the exponent is not in the current exponent range, we
               choose to return a NaN as this is probably a user error.
               Indeed this can happen only if the exponent range has been
               reduced to a very small interval and/or the precision is
               huge (very unlikely). */
            MPFR_SET_NAN (rop);
            __gmpfr_flags |= MPFR_FLAGS_NAN; /* Can't use MPFR_RET_NAN */
            return 1;
        }
        if (cnt != 0)
            mpn_lshift (rp + k, rp, nlimbs, cnt);
        if (k != 0)
            MPN_ZERO (rp, k);
    }
    else
        MPFR_SET_ZERO (rop);

    return 0;
}
Ejemplo n.º 4
0
int
mpfr_urandom (mpfr_ptr rop, gmp_randstate_t rstate, mpfr_rnd_t rnd_mode)
{
  mpfr_limb_ptr rp;
  mpfr_prec_t nbits;
  mp_size_t nlimbs;
  mp_size_t n;
  mpfr_exp_t exp;
  mpfr_exp_t emin;
  int cnt;
  int inex;

  rp = MPFR_MANT (rop);
  nbits = MPFR_PREC (rop);
  nlimbs = MPFR_LIMB_SIZE (rop);
  MPFR_SET_POS (rop);
  exp = 0;
  emin = mpfr_get_emin ();
  if (MPFR_UNLIKELY (emin > 0))
    {
      if (rnd_mode == MPFR_RNDU || rnd_mode == MPFR_RNDA
          || (emin == 1 && rnd_mode == MPFR_RNDN
              && random_rounding_bit (rstate)))
        {
          mpfr_set_ui_2exp (rop, 1, emin - 1, rnd_mode);
          return +1;
        }
      else
        {
          MPFR_SET_ZERO (rop);
          return -1;
        }
    }

  /* Exponent */
#define DRAW_BITS 8 /* we draw DRAW_BITS at a time */
  cnt = DRAW_BITS;
  MPFR_ASSERTN(DRAW_BITS <= GMP_NUMB_BITS);
  while (cnt == DRAW_BITS)
    {
      /* generate DRAW_BITS in rp[0] */
      mpfr_rand_raw (rp, rstate, DRAW_BITS);
      if (MPFR_UNLIKELY (rp[0] == 0))
        cnt = DRAW_BITS;
      else
        {
          count_leading_zeros (cnt, rp[0]);
          cnt -= GMP_NUMB_BITS - DRAW_BITS;
        }

      if (MPFR_UNLIKELY (exp < emin + cnt))
        {
          /* To get here, we have been drawing more than -emin zeros
             in a row, then return 0 or the smallest representable
             positive number.

             The rounding to nearest mode is subtle:
             If exp - cnt == emin - 1, the rounding bit is set, except
             if cnt == DRAW_BITS in which case the rounding bit is
             outside rp[0] and must be generated. */
          if (rnd_mode == MPFR_RNDU || rnd_mode == MPFR_RNDA
              || (rnd_mode == MPFR_RNDN && cnt == exp - emin - 1
                  && (cnt != DRAW_BITS || random_rounding_bit (rstate))))
            {
              mpfr_set_ui_2exp (rop, 1, emin - 1, rnd_mode);
              return +1;
            }
          else
            {
              MPFR_SET_ZERO (rop);
              return -1;
            }
        }
      exp -= cnt;
    }
  MPFR_EXP (rop) = exp; /* Warning: may be outside the current
                           exponent range */


  /* Significand: we need generate only nbits-1 bits, since the most
     significant is 1 */
  mpfr_rand_raw (rp, rstate, nbits - 1);
  n = nlimbs * GMP_NUMB_BITS - nbits;
  if (MPFR_LIKELY (n != 0)) /* this will put the low bits to zero */
    mpn_lshift (rp, rp, nlimbs, n);

  /* Set the msb to 1 since it was fixed by the exponent choice */
  rp[nlimbs - 1] |= MPFR_LIMB_HIGHBIT;

  /* Rounding */
  if (rnd_mode == MPFR_RNDU || rnd_mode == MPFR_RNDA
      || (rnd_mode == MPFR_RNDN && random_rounding_bit (rstate)))
    {
      /* Take care of the exponent range: it may have been reduced */
      if (exp < emin)
        mpfr_set_ui_2exp (rop, 1, emin - 1, rnd_mode);
      else if (exp > mpfr_get_emax ())
        mpfr_set_inf (rop, +1); /* overflow, flag set by mpfr_check_range */
      else
        mpfr_nextabove (rop);
      inex = +1;
    }
  else
    inex = -1;

  return mpfr_check_range (rop, inex, rnd_mode);
}