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/* mpfr_urandomb (rop, state, nbits) -- Generate a uniform pseudorandom
real number between 0 (inclusive) and 1 (exclusive) of size NBITS,
using STATE as the random state previously initialized by a call to
gmp_randinit_lc_2exp_size().
Copyright 2000-2004, 2006-2019 Free Software Foundation, Inc.
Contributed by the AriC and Caramba 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
https://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#define MPFR_NEED_LONGLONG_H
#include "mpfr-impl.h"
/* generate nbits random bits into mp[], assuming mp was allocated to contain
a sufficient number of limbs */
void
mpfr_rand_raw (mpfr_limb_ptr mp, gmp_randstate_t rstate,
mpfr_prec_t nbits)
{
mpz_t z;
MPFR_ASSERTN (nbits >= 1);
/* Check for integer overflow (unless mp_bitcnt_t is signed,
but according to the GMP manual, this shouldn't happen).
Note: mp_bitcnt_t has been introduced in GMP 5.0.0. */
MPFR_ASSERTN ((mp_bitcnt_t) -1 < 0 || nbits <= (mp_bitcnt_t) -1);
mpz_init (z);
mpz_urandomb (z, rstate, nbits);
MPN_COPY(mp, PTR(z), MPFR_PREC2LIMBS (nbits));
mpz_clear (z);
}
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 */
exp -= cnt;
if (MPFR_UNLIKELY (! MPFR_EXP_IN_RANGE (exp)))
{
/* 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;
}
MPFR_SET_EXP (rop, exp);
if (cnt != 0)
mpn_lshift (rp + k, rp, nlimbs, cnt);
else if (k != 0)
mpn_copyd (rp + k, rp, nlimbs);
if (k != 0)
MPN_ZERO (rp, k);
}
else
MPFR_SET_ZERO (rop);
return 0;
}
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