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/*
Copyright (C) 2012 Fredrik Johansson
This file is part of Arb.
Arb is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "arb.h"
void
_arb_get_rand_fmpq(fmpz_t num, fmpz_t den, flint_rand_t state,
const fmpz_t den_mult, const arb_t x)
{
fmpz_t a, b, exp;
fmpz_init(a);
fmpz_init(b);
fmpz_init(exp);
arb_get_interval_fmpz_2exp(a, b, exp, x);
if (COEFF_IS_MPZ(*exp))
{
flint_printf("exception: arb_get_rand_fmpq: too large exponent\n");
flint_abort();
}
if (*exp >= 0)
{
fmpz_mul_2exp(a, a, *exp);
fmpz_mul_2exp(b, b, *exp);
}
/* generate random integer in [a*den, b*den] */
fmpz_mul(a, a, den_mult);
fmpz_mul(b, b, den_mult);
fmpz_add_ui(b, b, UWORD(1));
fmpz_sub(b, b, a);
/* return one endpoint with high probability (used for stress
testing rounding) */
if (n_randint(state, 6) == 0)
{
if (n_randint(state, 2))
fmpz_zero(num);
else
fmpz_sub_ui(num, b, UWORD(1));
}
else
{
fmpz_randtest_mod(num, state, b);
}
fmpz_add(num, num, a);
fmpz_set(den, den_mult);
if (*exp < 0)
fmpz_mul_2exp(den, den, -(*exp));
fmpz_clear(a);
fmpz_clear(b);
fmpz_clear(exp);
}
void
arb_get_rand_fmpq(fmpq_t q, flint_rand_t state, const arb_t x, slong bits)
{
/* there is only one rational */
if (arb_is_exact(x))
{
arf_get_fmpq(q, arb_midref(x));
return;
}
/* pick a denominator */
fmpz_randbits(fmpq_denref(q), state, n_randint(state, bits + 1));
fmpz_abs(fmpq_denref(q), fmpq_denref(q));
if (fmpz_is_zero(fmpq_denref(q)))
fmpz_one(fmpq_denref(q));
_arb_get_rand_fmpq(fmpq_numref(q), fmpq_denref(q), state, fmpq_denref(q), x);
fmpq_canonicalise(q);
}
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