81 lines
2.0 KiB
C
81 lines
2.0 KiB
C
|
/*=============================================================================
|
||
|
|
|
||
|
|
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
|
||
|
|
|
||
|
|
******************************************************************************/
|
||
|
|
|
||
|
|
#include <gmp.h>
|
||
|
|
#include "flint.h"
|
||
|
|
#include "fmpz.h"
|
||
|
|
#include "ulong_extras.h"
|
||
|
|
|
||
|
|
slong
|
||
|
|
fmpz_flog(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_flog_ui(n, *b);
|
||
|
|
|
||
|
|
sign = fmpz_cmp(n, b);
|
||
|
|
if (sign <= 0)
|
||
|
|
return (sign == 0) ? 1 : 0;
|
||
|
|
|
||
|
|
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--;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
/* Adjust up */
|
||
|
|
else if (sign < 0)
|
||
|
|
{
|
||
|
|
while (1)
|
||
|
|
{
|
||
|
|
fmpz_mul(t, t, b);
|
||
|
|
if (fmpz_cmp(t, n) <= 0)
|
||
|
|
r++;
|
||
|
|
else
|
||
|
|
break;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
fmpz_clear(t);
|
||
|
|
return r;
|
||
|
|
}
|
||
|
|
|