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/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2011 Sebastian Pancratz
Copyright (C) 2011 Fredrik Johansson
******************************************************************************/
#include <gmp.h>
#include "flint.h"
#include "fmpz.h"
#include "ulong_extras.h"
slong
fmpz_clog(const fmpz_t n, const fmpz_t b)
{
fmpz_t t;
int sign;
slong r;
if (fmpz_is_one(n))
return 0;
if (!COEFF_IS_MPZ(*b))
return fmpz_clog_ui(n, *b);
if (fmpz_cmp(n, b) <= 0)
return 1;
r = fmpz_dlog(n) / fmpz_dlog(b);
fmpz_init(t);
fmpz_pow_ui(t, b, r);
sign = fmpz_cmp(t, n);
/* Adjust down */
if (sign > 0)
{
while (sign > 0)
{
fmpz_divexact(t, t, b);
sign = fmpz_cmp(t, n);
r--;
}
r += (sign != 0);
}
/* Adjust up */
else if (sign < 0)
{
while (sign < 0)
{
fmpz_mul(t, t, b);
sign = fmpz_cmp(t, n);
r++;
}
}
fmpz_clear(t);
return r;
}
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